Patent Grant
8765652
The present invention relates to formulations, methods and kits containing or employing an agent for use in deactivating nucleic acids present on a surface or in a solution.
Procedures for qualitatively or quantitatively determining the presence of particular organisms or viruses in a test sample routinely rely upon nucleic acid-based probe testing. To increase the sensitivity of these procedures, an amplification step is often included to increase the copy number of potential nucleic acid target sequences present in the test sample. During amplification, polynucleotide chains containing the target sequence and/or its complement are synthesized in a template-dependent manner from ribonucleoside or deoxynucleoside triphosphates using nucleotidyltransferases known as polymerases. There are many amplification procedures in general use today, including the polymerase chain reaction (PCR), Q-beta replicase, self-sustained sequence replication (3SR), transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), ligase chain reaction (LCR), strand displacement amplification (SDA) and loop-mediated isothermal amplification (LAMP), each of which is well known in the art. See, e.g., Mullis, “Process for Amplifying Nucleic Acid Sequences,” U.S. Pat. No. 4,683,202; Erlich et al., “Kits for Amplifying and Detecting Nucleic Acid Sequences,” U.S. Pat. No. 6,197,563; Walker et al., Nucleic Acids Res., 20:1691-1696 (1992); Fahy et al., “Self-sustained Sequence Replication (3SR): An Isothermal Transcription-Based Amplification System Alternative to PCR,” PCR Methods and Applications, 1:25-33 (1991); Kacian et al., “Nucleic Acid Sequence Amplification Methods,” U.S. Pat. No. 5,399,491; Davey et al., “Nucleic Acid Amplification Process,” U.S. Pat. No. 5,554,517; Birkenmeyer et al., “Amplification of Target Nucleic Acids Using Gap Filling Ligase Chain Reaction,” U.S. Pat. No. 5,427,930; Marshall et al., “Amplification of RNA Sequences Using the Ligase Chain Reaction,” U.S. Pat. No. 5,686,272; Walker, “Strand Displacement Amplification,” U.S. Pat. No. 5,712,124; Notomi et al., “Process for Synthesizing Nucleic Acid,” U.S. Pat. No. 6,410,278; Dattagupta et al., “Isothermal Strand Displacement Amplification,” U.S. Pat. No. 6,214,587; and Lee et al., Nucleic Acid Amplification Technologies: Application To Disease Diagnosis (1997).
Nucleic acid products formed during an amplification procedure (i.e., amplicon) can be analyzed either during the course of the amplification reaction (real-time) or once the amplification reaction has been generally completed (end-point) using detectable probes. While the probes are designed to screen for target-containing amplicon, other products may be produced during an amplification procedure (e.g., primer-dimers formed in a typical PCR reaction) that have the potential to interfere with the desired amplification reaction. Following completion of the amplification procedure and exposure to detectable probes, the resulting reaction mixture is discarded.
During the steps of an assay or synthesis procedure which includes an amplification procedure, it is possible to contaminate work surfaces or laboratory equipment with nucleic acids used or formed in the assay through spills, mishandling, aerosol formation, etc. This nucleic acid can then carry-over and contaminate future amplification and other nucleic acid assay procedures performed using the same laboratory equipment and/or on the same work surfaces. The presence of carryover products can result in the unwanted consumption of amplification reagents or, in the case of target-containing amplicon from a previous amplification procedure, it can lead to an erroneous result, as amplification procedures are capable of detecting the presence of even minute amounts of target nucleic acid. In the case of a synthetic amplification reaction, the desired nucleic acid product may become contaminated by carry-over products and/or synthesis yields may be reduced.
Various methods have been devised to limit carryover contamination. A PCR amplification product, for example, can be deactivated from further amplification by irradiation with UV light. See Ou et al., BioTechniques, 10:442-446 (1991); and Cimino et al., Nucleic Acids Res., 19:99-107 (1991). Such irradiation in the absence or presence of a DNA binding photoactivatable ligand (e.g., isopsoralen) makes the product DNA nonamplifiable but retains the specific hybridization property. In addition, use of a 3′-ribose primer in a PCR reaction produces nucleic acid that can be readily destroyed by an alkali (e.g., NaOH). See Walder et al., Nucleic Acids Res., 21:4339-4343 (1993). Similarly, other procedures are used to produce specific modified nucleic acids that can be selectively destroyed by treatment with a specific enzyme. Such modified nucleic acids have been produced by amplification in the presence of dUTP as a substrate in a PCR reaction. Deoxy U-containing product DNA can be deactivated by a U-specific enzyme making the DNA nonamplifiable. See Integrated DNA Technologies Technical Bulletin, Triple C primers (1992); and Longo et al., Gene, 93:125-128 (1990). Many of these methods function well with DNA but require expensive reagents and affect the course of the amplification procedure (e.g., requiring longer times and specific reagents).
In a preferred method, work surfaces and laboratory equipment exposed to nucleic acid products are treated with a 50% bleach solution (i.e., a bleach solution containing about 2.5% to about 3.25% (w/v) sodium hypochlorite) to deactivate nucleic acids. See GEN-PROBE® APTIMA COMBO 2® Assay Package Insert, IN0037 Rev. A/2003-08. While this bleach solution is effective at deactivating nucleic acids present on treated surfaces, it tends to create noxious fumes in poorly ventilated areas and corrodes laboratory equipment over time. Therefore, it is an object of the present invention to provide a formulation containing a nucleic acid deactivating agent that is stable in solution, has a tolerable odor, and which is non-corrosive or is substantially less corrosive than a standard 50% bleach solution.
The present invention satisfies this objective by providing a formulation that contains or can be combined with a nucleic acid deactivating agent (“deactivating agent”) in an amount sufficient to deactivate nucleic acids contacted with the formulation in solution or on a solid surface. By “deactivate” is meant that the nucleic acid is altered such that it can no longer function as it did prior to deactivation. For example, the nucleic acid may no longer be capable of acting as a template in, or otherwise interfering with (e.g., through the formation of primer-dimers), an amplification reaction, binding to another nucleic acid or protein, or serving as a substrate for an enzyme. The term “deactivate” does not imply any particular mechanism by which the deactivating agent of the formulation alters nucleic acids. The components of the formulation include a corrosion-inhibiting agent, a wetting agent, a solubilizing agent and, optionally, a deactivating agent. When the formulation is comprised of all four components, the corrosion-inhibiting agent is present in an amount sufficient to reduce the corrosiveness of the deactivating agent, the wetting agent is present in an amount sufficient to improve the dispersion properties of the deactivating agent and/or to increase the solubility of the deactivating agent and/or other material present on a solid surface or in a solution, the solubilizing agent is present in an amount sufficient to increase the solubility of the deactivating agent, or the corrosion inhibiting agent, or the wetting agent, or various combinations thereof, and the deactivating agent is present in an amount sufficient to substantially deactivate nucleic acids contacted with the formulation. If the formulation does not include the deactivating agent, then the amounts of the corrosion-inhibiting agent, the wetting agent and the solubilizing agent are concentrated to account for their decreased concentrations when combined with the deactivating agent and any diluents (e.g., water) which may be used to form a final working solution capable of deactivating nucleic acids.
Deactivating agents of the present invention are selected for their ability to substantially deactivate nucleic acids present on a surface or in a solution, thereby preventing the nucleic acids from acting as unintended templates in an amplification reaction or otherwise contaminating a workspace, laboratory equipment or materials, or working solutions. For certain applications, the deactivating agents of the present invention may be used without the corrosion-inhibiting agent, the wetting agent and/or the solubilizing agent referred to above. Preferred deactivating agents include bleach, sodium hypochlorite (NaOCl) (or hypochlorous acid (HOCl), which results when chlorine ions are combined with water), sodium hypochlorite and sodium bromide (NaBr), dichloroisocyanurate (DCC), hydrogen peroxide (H2O2) and metal ions, preferably copper ions (Cu++) (e.g., cupric sulfate (CuSO4) or cupric acetate (Cu(CH3COO)2.H2O)), hydrogen peroxide in combination with metal ions and piperazine or piperazine-containing formulations, acetate or ascorbate, percarbonate (2Na2CO3.3H2O2), peroxymonosulfate (KHSO5), peroxymonosulfate and potassium bromide (KBr), hypobromite ions (OBr—) (e.g., hypobromous acid (HOBr)) and halohydantoins (e.g., 1,3-dihalo-5,5-dimethylhydantoins). Hypochlorite and hypobromite ions may be delivered to a solution using a salt, such as sodium. Particularly preferred are deactivating agents containing chloronium ions (Cl+), such as sodium hypochlorite, a component of household bleach, or DCC. The DCC may be substantially pure or it may be part of a DCC-containing solution, such as ACT 340 PLUS 2000® disinfectant, containing sodium dichloroisocyanurate dihydrate at 40% p/p. An advantage of DCC is that it is less corrosive and, in some cases, more resistant to inactivation by contaminating organic material than hypochlorite.
While the deactivating agents of the present invention may be provided, alone or as part of a formulation, in any amount sufficient to deactivate nucleic acids, preferred concentration ranges of above-described deactivating agents are as follows: (i) from about 0.06% to about 3% (w/v), about 0.18% to about 1.8% (w/v), about 0.6% to about 1.5% (w/v), or about 0.6% to about 1.2% (w/v) sodium hypochlorite, or sodium hyphochlorite and sodium bromide, where the sodium hypochlorite:sodium bromide ratio is about 5:1 to about 1:5, about 2:1 to about 1:2, or about 1:1; (ii) from about 5 mM to about 400 mM, about 10 mM to about 200 mM, about 20 mM to about 100 mM, or about 40 mM to about 80 mM DCC; (iii) from about 100 mM to about 880 mM, about 200 mM to about 880 mM, or about 250 mM to about 800 mM percarbonate; (iv) from about 50 mM to about 300 mM or about 100 mM to about 200 mM peroxymonosulfate or peroxymonosulfate and potassium bromide, where the peroxymonosulfate:potassium bromide ratio is about 2:1 to about 1:2 or about 1:1. These ranges reflect concentrations in final working solutions to be used directly on a surface or in a solution and may be adjusted where the formulation is a concentrate. The preferred concentration ranges of hydrogen peroxide containing formulations are described below.
When chlorine is a component of the deactivating agent (e.g., sodium hypochlorite or DCC), the potential organic load on a surface or in a solution that will be exposed to the deactivating agent is a factor in determining the concentration of the chlorine-containing component. This is because organic materials, especially compounds containing primary amine and sulfhydryl groups, react with chloronium ions and effectively scavenge them from solution. Therefore, when selecting the concentration of the chlorine containing component to use in the formulation for deactivating nucleic acids, consideration must be given not only to the expected amount of nucleic acid on the surface or in the solution to be treated, but also to the expected organic load, as well as sources of interfering substances of a non-organic origin. Interfering substances may also affect non-chlorine based deactivating agents and, for this reason, their influence on a deactivating agent should be evaluated when determining the concentration of the deactivating agent needed to deactivate nucleic acids on a surface or in a solution.
The corrosion-inhibiting agents of the formulation are selected to counter the corrosive effects of the deactivating agent. As an example, bleach is a highly corrosive material that can damage laboratory equipment and fixtures over time, requiring early replacement. We unexpectedly discovered that the corrosion-inhibiting agents do not interfere with the activity of the deactivating agents. Corrosion-inhibiting agents of the present invention include phosphate, borate, sodium bicarbonate, detergents and other corrosion-inhibiting agents known in the art. Particularly preferred is sodium bicarbonate. The concentration of the corrosion-inhibiting agent present in the formulation, when combined with the deactivating agent in a final working solution for direct use on a surface or in a solution, is preferably in the range of from about 10 mM to about 750 mM. The pH of the corrosion-inhibiting agent should be selected to limit any loss in the activity of the deactivating agent over time, yet still be effective in reducing the corrosiveness of the deactivating agent. By way of example, sodium salts of phosphate were found to destabilize sodium hypochlorite at pH 6.4 and 7.5 but not at pH 9.1 and 9.5. Conversely, sodium salts of phosphate were found to destabilize DCC at pH 9.1 and 9.5 but not at pH 6.4 and 7.5.
The wetting agent is included in the formulation to ensure that the deactivating agent makes sufficient contact with the surface being treated and/or to improve the solubility of the deactivating agent and/or other material that may be present on a surface or in a solution to be decontaminated (e.g., nucleic acids, organic substances, oils or films, etc.). Detergents and surfactants are preferred wetting agents because they reduce surface tension and allow for more complete wetting of surfaces with the deactivating agent. Additionally, detergents and surfactants help to solubilize materials to be removed from surfaces or deactivated in a solution. But because detergents and surfactants tend to foam, detergent and surfactant types and concentrations should be selected to limit foaming while providing good wetting and solubilization qualities in the final working solution. Preferred detergents and surfactants include sodium dodecyl sulfate (SDS), lithium lauryl sulfate (LLS), PHOTO-FLO® 200 Solution (Eastman Kodak Company, Rochester, N.Y.; Cat. No. 146-4502), saponin, cetyl trimethylammonium bromide (CTAB), ALCONOX® detergent containing 10-30% (w/w) sodium dodecylbenzenesulfonate, 7-13% (w/w) sodium carbonate, 10-30% (w/w) tetrasodium pyrophosphate and 10-13% (w/w) sodium phosphate (Alconox, Inc., White Plains, N.Y.; Cat. No. 1104-1), MICRO-90® cleaning solution containing less than 20% (w/w) glycine, N,N′-1,2-ethanediylbis-(N-(carboxymethyl)-,tetra-sodium salt, less than 20% (w/w) benzenesulfonic acid, dimethyl-, ammonium salt, less than 20% (w/w) benzenesulfonic acid, dodecyl-, cpd. with 2,2′,2″-nitrilotris (ethanol), and less than 20% (w/w) poly(oxy-1,2-ethanediyl),alpha-(undecyl)-omega-hydroxy (International Products Corporation, Burlington, N.J.), and polyoxyethylene detergents (e.g., TRITON® X-100). Most preferred are SDS and LLS at a concentration range preferably of from about 0.005% to about 1% (w/v), about 0.005% to about 0.1% (w/v), or about 0.005% to about 0.02% (w/v) in the final working solution.
The formulation further includes the solubilizing agent for helping to maintain the components of the formulation in solution. The solubilizing agent may contain, for example, an organic solvent or an emulsifying agent, such as that found in Fragrance No. 2141-BG, a citrus fragrance available from International Flavors and Fragrances (IFF) of Hazlet, N.J. Fragrances may have the additional advantage of masking the odor of the deactivating agent (e.g., sodium hypochlorite). Organic solvents that may be included in the formulation include benzyl acetate, PS20 and isopropanol. Emulsifying agents that may be included in the formulation include polyoxyethylene sorbitan mono-palmitate (TWEEN® 40), lecithin and ethylene glycol distearate. In some cases, the inventors discovered that the wetting agent was necessary to maintain the solubilizing agent in solution when combined with the corrosion-inhibiting agent and that the solubilizing agent was necessary to maintain the detergent in solution when combined with the corrosion-inhibiting agent. And, when the formulation also include the deactivating agent, all four components remained in solution. When the solubilizing agent is a fragrance, such as IFF Fragrance No. 2415-BG or 2141-BG, the preferred concentration of the solubilizing agent in a final working solution which contains the deactivating agent is in a range from about 0.001% to about 20% (v/v), about 0.001% to about 2% (v/v), or about 0.002% to about 0.2% (v/v). The concentration of the solubilizing agent selected should be such that it has no substantial impact on the activity and stability of the deactivating agent and the corrosion-inhibiting agent.
In a particularly preferred formulation of the present invention, a 6.7× concentrate is prepared having the following formulation: 600 mM sodium bicarbonate, pH 9.3+0.1% SDS+0.05% IFF Fragrance No. 2145-BG. When the formulation further includes a deactivating agent, a particularly preferred formulation is as follows: 0.6% sodium hypochlorite+90 mM sodium bicarbonate, pH 9.3+0.015% SDS+0.0075% IFF Fragrance No. 2145-BG. Of course, the components and concentrations of these preferred formulations can be modified in the manner described herein, without the exercise of undue experimentation, to arrive at alternative formulations that are stable and capable of deactivating nucleic acids on a surface or in a solution while minimizing the potential corrosive effect of the deactivating agent selected.
Based on our discovery that the order in which the agents are combined can be important to preventing the formation of precipitates or an otherwise non-homogenous formulation, a further embodiment of the present invention is directed to a method of making the above-described formulations. This method includes the following ordered steps: (i) separately dissolving solid forms of a corrosion-inhibiting agent and a wetting agent; (ii) combining together the dissolved forms of the corrosion-inhibiting agent and the wetting agent to form a mixture; and (iii) combining together a solubilizing agent and the mixture to form a formulation comprising the corrosion-inhibiting agent, the wetting agent and the solubilizing agent, where the agents of this formulation remain substantially in solution at 22° C. (approximately room temperature). If the solubilizing agent is provided in a solid form, it too may be dissolved prior to combining the solubilizing agent with the mixture. The deactivating agent can then be added to the formulation, where the deactivating agent may be added directly to the formulation or it may be dissolved prior to combining it with the formulation. If water is used to dissolve any of the solid forms of the agents, it is preferably distilled or deionized water. For many of the formulations tested, it was discovered that deviating from the above-ordered steps for combining the agents resulted in the formation of non-homogenous solutions (e.g., the solubilizing agent was first combined with either the corrosion-inhibiting agent or the wetting agent).
For those applications that do not require a wetting agent, we discovered that the deactivating agent and the corrosion-inhibiting agent may be combined without substantially affecting the ability of the deactivating agent to deactivate nucleic acids. Therefore, formulations of the present invention containing corrosive deactivating agents are not required to include a wetting agent and a solubilizing agent.
Another preferred deactivating agent of the present invention comprises hydrogen peroxide and metal ions, such as, for example, copper, cobalt, iron or manganese ions (e.g., cupric sulfate or cupric acetate). For solution-based applications in particular, we found that the metal ions (e.g., copper ions) can be stabilized in a chemical configuration that is active with hydrogen peroxide at deactivating nucleic acids when the deactivating agent further includes piperazine or reagents that contain the piperazine group, such as the buffer HEPES (N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid)), acetate, and like compounds and reagents. Surprisingly, we further discovered that piperazine can stimulate the deactivation of nucleic acids in the presence of hydrogen peroxide and copper ions. The hydrogen peroxide of this deactivating agent is preferably present at a concentration range of from about 0.5% to about 30% (w/v), about 1% to about 15% (w/v), or about 1% to about 6% (w/v). Where, for example, copper sulfate is the source of the metal ions, the preferred concentration range of copper sulfate is from about 0.1 mM to about 5 mM, about 0.5 mM to about 2.5 mM, or about 1 mM to about 2.5 mM. And if piperazine is used to stimulate the deactivation of nucleic acids, the preferred concentration range of piperazine is from about 0.5 mM to about 250 mM, about 1 mM to about 200 mM, or about 10 mM to about 100 mM. A preferred formulation of this embodiment comprises 3% hydrogen peroxide+2 mM CuSO4+50 mM piperazine, pH 5.5. This deactivating agent has the advantage of being non-corrosive and odorless.
In a further embodiment, the present invention relates to a method for deactivating nucleic acids suspected of being present on a surface. In this method, a first amount of a first reagent comprising a deactivating agent is applied to the surface. Where warranted by the expected presence of interfering substances (e.g., organic load and/or oily films or residue on the surface), and to ensure adequate deactivation of nucleic acids present on the surface, a second amount of a second reagent comprising a deactivating agent can be applied to the surface. The first and second reagents of this method may be the same or different and one or both of the reagents may comprise one of the formulations described above. In a preferred embodiment, the reagents are removed from the surface, such as by wiping with an absorbent material (e.g., a paper towel or cotton gauze), before the reagents have had an opportunity to completely evaporate. By wiping before the reagents have completely evaporated, nucleic acids that may not have been chemically deactivated by the reagents can be mechanically removed by the absorbent material. Additionally, by wiping with an absorbent material after the first application, other materials solubilized by the first reagent that might consume all or part of the deactivating agent in the second application can be removed. Therefore, in a particularly preferred mode, there is no substantial “soak time” between the applying and removing steps of the preferred embodiment. This means that the delay between application of a reagent to the surface and its removal therefrom is no more than a few minutes, preferably no more than one minute, and, more preferably, the removal of the reagent from the surface immediately follows its application thereto. Also, to avoid all possible sources of contamination, it is recommended that the reagents for deactivating nucleic acids be applied with one gloved hand and that removal of the reagents be performed with another gloved hand.
To reduce the organic load on a surface prior to application of the first reagent, the surface may be pre-treated with an application of a detergent. Additionally, for surface applications, it is recommended that the surface not be cleaned with water following removal of the first or second reagents from the surface, as the water may contain amplifiable nucleic acids or nucleic acids or other chemicals that could interfere with an amplification reaction.
In still another embodiment, the present invention relates to a method for deactivating nucleic acids suspected of being present in one or more conduits using a formulation described above. The conduits may be present, for example, in one or more pipettes or an aspirator manifold. In this method, the formulation containing the deactivating agent is drawn into the one or more conduits, such as by suctioning. The formulation is then dispensed from the one or more conduits. After dispensing the formulation, the one or more conduits may be exposed to a wash solution by drawing the wash solution into the one or more conduits and then dispensing the wash solution from the conduits. The wash solution may be, for example, purified water or a reagent solution and is used to rinse residual amounts of the formulation from the conduits.
In yet another embodiment, the present invention relates to a kit comprising, in one or more receptacles, a formulation as described above for use in deactivating nucleic acids. In one embodiment, if the kit includes a deactivating agent, the deactivating agent is preferably contained in a receptacle separate from one or more receptacles containing the corrosion-inhibiting agent, the wetting agent and/or the solubilizing agent. One or more of the components of the formulation may be provided in a pre-measured amount suitable for making a specific volume of final solution or as a bulk powder. If pre-measured, powder forms of the component or components may be provided in packets or capsules or as tablets to be dissolved in water before being combined with the other components of the formulation. The kit may further include instructions recorded in tangible form (e.g., paper, diskette, CD-ROM, DVD or video cassette) for combining the deactivating agent and the other components of the formulation. The kit may also include one or more reagents for performing a nucleic acid amplification reaction. Such reagents may include one or more enzyme reagents (e.g., an RNA or a DNA polymerase) for use in amplifying a nucleic acid sequence of interest. Enzyme reagents for use in performing a transcription-based amplification, for example, include a reverse transcriptase and an RNA polymerase (e.g., T7 RNA polymerase). Other amplification reagents may also be included, such as, for example, amplification oligonucleotides (e.g., primers, promoter-primers and/or splice templates), nucleotide triphosphates, metal ions and co-factors necessary for enzymatic activity.
The present invention is directed in part to formulations, methods and kits which are useful for deactivating nucleic acids. These formulations, methods and kits are described above and in the examples and claims which follow. In addition, the examples describe screening methods for selecting formulations of the present invention which are useful for deactivating nucleic acids on work surfaces, laboratory equipment and/or in solution, or which could be used as, for example, disinfectants. Such formulations may also be useful for deactivating biological molecules, like proteins and lipids. The examples further consider the effect of a number of exemplary formulations in both pre- and post-amplification applications.
The examples set forth below illustrate but do not limit the invention.
An experiment was conducted in which a 71-mer DNA oligonucleotide was reacted with various concentrations of ULTRA CLOROX® BLEACH (The Clorox Company, Oakland, Calif.) at a concentration of 6.15% (w/v) sodium hypochlorite, and the reaction products were analyzed using polyacrylamide gel electrophoresis (PAGE). Ten samples were prepared by mixing 2 μL of the DNA oligonucleotide, at a concentration of 173 μg/mL, with distilled water in sample vials before adding varying concentrations of bleach to bring the total volume of each sample to 20 μL. The samples were mixed by vortexing for about 10 seconds and then provided with 20 μL of a 2× TBE-Urea sample buffer containing 180 mM Tris base, 180 mM boric acid, 4 mM ethylenediaminetetraacetic acid (EDTA), pH 8.0 (Invitrogen Corporation, Carlsbad, Calif.; Cat. No. LC 6876), bringing the total volume of each sample to 40 μL. The samples were again mixed by vortexing for about 10 seconds. Final bleach concentrations in the samples ranged from 0 to 50% bleach, as set forth in Table 1 below. A 10 μL aliquot of each sample was loaded into one of the 10 lanes of a 10% polyacrylamide TBE-Urea gel, and the gel was run for 40 minutes at 180 V. When the run was completed, the gel was removed from its cast, contacted with 100 mL of a SYBR® Green I nucleic acid gel stain (Molecular Probes, Eugene Oreg.; Cat. No. 57563) diluted 1/10,000 with distilled water, and mixed at 10 rpm for 30 minutes. After staining, the gel was photographed using a CHEMIIMAGER™ System 4400 (Alpha Innotech Corporation, San Leandro, Calif.). The separated products stained on a gel are commonly referred to as bands. A copy of the resulting electrophoretogram is presented in
From the results illustrated in the electrophoretogram of
The experiment of Example 1 was repeated, substituting a 60-mer DNA/RNA chimeric oligonucleotide at a concentration of 200 μg/ml for the DNA oligonucleotide of that experiment. The RNA of the chimera consisted of 2′-O-methyl ribonucleotides. A copy of the resulting electrophoretogram appears in
Dichloroisocyanuric acid, sodium salt (DCC) (Sigma-Aldrich, Milwaukee, Wis.; Prod. No. 21, 892-8) and ULTRA CLOROX® BLEACH (6.15% (w/v) sodium hypochlorite) were examined at varying available chlorine concentrations in this experiment for their comparative abilities to react with nucleic acid. The chlorine concentrations tested are set forth in Table 2 below. In all other aspects, including the use of the 71-mer DNA oligonucleotide, this experiment was identical to the experiment detailed in Example 1.
The results of this experiment are illustrated in
In this experiment, a 71-mer DNA oligonucleotide present at a concentration of 53 μg/mL was reacted with various concentrations of 30% (w/v) hydrogen peroxide (Fisher Scientific, Tustin, Calif.; Cat. No. BP2633-500) and 30% (w/v) hydrogen peroxide plus cupric sulfate (Sigma-Aldrich, Milwaukee, Wis.; Prod. No. 45, 165-7), and the reaction products were analyzed using polyacrylamide gel electrophoresis (PAGE). Ten samples were prepared in the manner indicated in Table 3 below, with the DNA and water being combined prior to adding 30% (w/v) hydrogen peroxide (8.8 M) and/or 1 mM cupric sulfate. The remaining procedural details of this experiment are the same as those set forth in Example 1. The concentration of peroxide in each lane is set forth in Table 4 below.
The resulting electrophoretogram appears in
The experiment of Example 4 was repeated using lower concentrations of the hydrogen peroxide component and 100 μM cupric sulfate in all lanes of the gel. The final concentration of peroxide in each lane of the gel is set forth in Table 5 below.
A copy of the resulting electrophoretogram appears in
Bleach is known to react with a variety of organic materials. These materials may thus interfere with the deactivation of nucleic acids by reacting with and consuming the bleach. The presence of these organic materials thus constitutes an “organic load” that must be compensated for by the presence of sufficient bleach to react with both the DNA and the organic materials. In this experiment, the scavenging effect of N-acetyl-L-cysteine (NALC), an organic load compound (i.e., a compound that may be expected to consume bleach), was examined in the presence of varying concentrations of ULTRA CLOROX® BLEACH. NALC is a reducing agent found in some enzyme reagents intended for use in amplification reactions. Two sets of 10 samples were prepared in this experiment, each sample containing 2 μL of a 71-mer DNA oligonucleotide at a concentration of 173 μg/mL. The first set of samples contained no NALC, while each sample of the second set of samples contained 16 μL NALC at a concentration of 11.4 mg/mL. The samples were prepared by first providing the DNA and NALC (if any) to sample vials and mixing the samples containing NALC by vortexing for about 10 seconds. The bleach was then added to both sets of samples at varying concentrations, along with distilled water, to bring the total volume of each sample to 20 μL. The samples were mixed by vortexing for about 10 seconds before adding 20 μL of a 2× TBE-Urea sample buffer (Invitrogen Corporation; Cat. No. LC 6876), bringing the total volume of each sample to 40 μL. The samples were again mixed by vortexing for about 10 seconds. Final bleach concentrations in the samples ranged from 0% to 50% bleach, as set forth in Table 6 below. A 10 μL aliquot of each sample was loaded into one of 10 lanes of a 10% polyacrylamide TBE-Urea gel, a separate gel being provided for each of the two sets of samples, and the gels were run for 40 minutes at 180V. When the runs were completed, the gels were removed from their casts, contacted with 100 mL of a SYBR® Green I nucleic acid gel stain (Molecular Probes; Cat. No. 57563) diluted 1/10,000 with distilled water, and mixed at 10 rpm for 30 minutes. After staining, the gels were photographed using a ChemiImager™ System 4400, and a copy of the resulting electrophoretogram is presented in
From the results illustrated in the electrophoretograms of
In this experiment, the effect of NALC and human serum upon the reaction of various concentrations of hydrogen peroxide and cupric sulfate with DNA was examined. A set of 11 samples was prepared, each sample containing 2 μL of a 71-mer DNA oligonucleotide at a concentration of 53 μg/mL. Other components of the samples included 100 μM cupric sulfate, 30% (w/v) hydrogen peroxide, and NALC at a concentration of 11.4 mg/mL. The amount of each component in the sample vials is set forth in Table 7 below. The samples were prepared by combining all sample components, except the hydrogen peroxide, in sample vials and mixing by vortexing for about 10 seconds. After mixing, the hydrogen peroxide was added to the samples at varying concentrations, bringing the total volume of sample 1 to 20 μL and samples 2-11 to 22 μL and giving the final concentrations indicated in Table 8 below. The samples were again mixed by vortexing for about 10 seconds before adding 20 μL of a 2× TBE-Urea sample buffer (Invitrogen Corporation; Cat. No. LC 6876), bringing the total volume of sample 1 to 40 μL and samples 2-11 to 42 μL. The remainder of the procedure and sources of the reagents were identical to that set forth in Example 6 above. A copy of the resulting electrophoretogram is presented in
The results illustrated in the electrophoretograms of
This experiment was conducted to evaluate the ability of various bleach concentrations to deactivate purified ribosomal RNA derived from Neisseria gonorrhoeae (“target”) in a pure system. Eight sample tubes were initially set up to contain 4 μL of target-containing water and 4 μL of bleach in the concentrations indicated in Table 9. For sample tubes 6 and 8, 4 μL of water was used in place of a bleach solution). The bleach used in this experiment was Ultra Chlorox® Bleach (6.15% (w/v) sodium hypochlorite). After set up, the contents of the sample tubes were incubated for 5 minutes at room temperature.
0
Following the room temperature incubation, 392 μL, of water (chilled on ice) was added to each sample tube. The samples then were analyzed by a real-time Transcription-Mediated Amplification (TMA) assay. In the assay, amplification reaction mixtures were prepared by combining a 4 μL, aliquot from each sample tube with 300 μL, of an Amplification Reagent (44.1 mM HEPES, 2.82% (w/v) trehalose, 33.0 mM KCl, 9.41 mM rATP, 1.76 rCTP, 11.76 rGTP, 1.76 mM UTP, 0.47 mM dATP, 0.47 mM dCTP, 0.47 mM dGTP, 0.47 mM dTTP, 30.6 mM MgCl2, 0.30% (v/v) ethanol, 0.1% (w/v) methyl paraben, 0.02% (w/v) propyl paraben, and 0.003% (w/v) phenol red) at pH 7.7 and spiked with 25.6 pmol of a T7 promoter-primer and 20.0 pmol of a non-T7 primer for amplifying a region of the target following a Transcription-Mediated Amplification (TMA) procedure (see Kacian et al., U.S. Pat. No. 5,399,491) and 80 pmol of a molecular beacon probe for detecting the resulting amplicon in real-time (see Tyagi et al., “Detectably Labeled Dual Conformation Oligonucleotide Probes, Assays and Kits,” U.S. Pat. No. 5,925,517). The probes and primers of this experiment were synthesized on an Expedite™ 8909 Nucleic Acid Synthesizer (Applied Biosystems, Foster City, Calif.) using standard phosphoramidite chemistry. See, e.g., Caruthers et al., Methods in Enzymology, 154:287 (1987). The molecular beacon probes were synthesized to include interacting Cy™5 and BHQ™ dyes using Cy5-CE phosphoramidite (Glen Research Corporation, Sterling, Va.; Cat. No. 10-5915-90) and 3′-BHQ-2 Glycolate CPG (BioSearch Technologies, Inc., Novato, Calif.; Cat. No. CG5-5042G-1).
Amplification reaction mixtures were then set up in a 96-well MICROTITER® plate (Thermo Labsystems, Helsinki, Finland; Cat. No. 9502887) in replicates of three, each well containing 75 μL, of a light mineral oil and 75 μL, of the amplification reaction mixture. The plates were covered with ThermalSeal sealing film (Sigma-Aldrich Co., St. Louis, Mo.; Product No. Z36, 967-5) and incubated in a Solo HT Microplate Incubator (Thermo Electron Corporation; Milford, Mass.) for 15 minutes at 62° C. to permit hybridization of the promoter-primer to the target, followed by a second 15 minute incubation in the Solo HT Microplate Incubator at 42° C. After incubating the contents of the plate, a multi-channel pipettor was used to add 25 μL of an Enzyme Reagent (50 mM N-acetyl-L-cysteine (NALC), 58 mM HEPES, 3.03% (w/v) trehalose, 10% TRITON® X-100 detergent, 1.04 mM EDTA, 20% (v/v) glycerol, 120 mM KCl, 120 RTU/μL Moloney murine leukemia virus (“MMLV”) reverse transcriptase, and 80 U/μL T7 RNA polymerase, where one “unit” of activity is defined as the synthesis and release of 5.75 fmol cDNA in 15 minutes at 37° C. for MMLV reverse transcriptase, and the production of 5.0 fmol RNA transcript in 20 minutes at 37° C. for T7 RNA polymerase) at pH 7.0 to each sample. Immediately after each set of Enzyme Reagent additions, the contents of the reaction wells were mixed by stirring with the corresponding pipette tips held by the pipettor. To measure the formation of amplicon in real-time, the plate was transferred to a Fluoroskan Ascent microplate fluorometer (Thermo Electron Corporation; Product No. 5210470) and incubated for 60 minutes at 42° C. Fluorescence from the reaction wells was measured in 30 second increments using a 639 nm excitation filter and 671 nm emission filter.
The results of this experiment are reported in the graph of
Several formulations were tested for efficacy in deactivating nucleic acids using multiple assays.
A. Real-time TMA Results
Neisseria gonorrhoaea (Ngo) ribosomal RNA (rRNA) was reacted with 0-20% commercial bleach, where the lowest bleach concentration was 0.2%, in a pure system and reaction products were analyzed by real-time TMA assays (see Example 8). Even at the lowest bleach concentration the rRNA was inactivated within the limits of sensitivity of the real-time assay (
Chlamydia trachomatis (Ctr) rRNA also was reacted with 0-20% bleach, where the lowest bleach concentration was 0.016%, in a pure system and reaction products were analyzed by real-time TMA assays. The lowest bleach concentration also inactivated the rRNA (
B. Capillary Electrophoresis Results
Ribosomal RNA was reacted with bleach in solution and products were analyzed by capillary electrophoresis. An Agilent 2100 Bioanalyzer was utilized to characterize nucleic acids exposed to deactivation solutions. In a 10 μL total reaction, the following were added (in order): (a) Milli-Q H2O or buffer, (b) an indicated amount of reagent (e.g., —OCl from bleach or H2O2), and (c) 0 nM (blank) or 150 nM (718 μM=470 ng/μL nt) Mycobacterium tuberculosis (Mtb) rRNA or 15 nM (71.8 μM=47.0 ng/μL nt) Mtb rRNA. The reactants were incubated for 10 min at room temperature (ca. 23° C.), and 90 μL 1 mM sodium ascorbate (900 μM final) then was added. As in the LABCHIP® protocol (Agilent Technologies, Inc.; Palo Alto, Calif.), the RNA ladder was denatured at 70° C. for 2 min, and then 1 μL of each reaction was loaded into wells on RNA 6000 Nano LABCHIP® or Pico LABCHIP® (Agilent Technologies, Inc.; Palo Alto, Calif.) containing 5 μL sample buffer. The components were mixed and the assay Prokaryote Total RNA was run in the Bio Sizing program (Agilent Technologies, Inc.; Palo Alto, Calif.).
Results from the capillary electrophoresis analysis showed a 1:1 ratio of hypochlorite-to-rRNA nucleotide substantially eliminated rRNA peaks (
C. Conclusions
Reaction of bleach (hypochlorite) with nucleic acids in a pure system was rapid and essentially complete at a 1:1 ratio of hypochlorite to nucleoside. These data suggested that any observed lack of decontamination of nucleic acids in the laboratory using bleach was not due to an inherently slow reaction of hypochlorite with the nucleic acids or the need for a high molar excess of bleach over the nucleic acids.
Effects of N-acetyl-L-cysteine (NALC), an organic load material, on the reaction between bleach and oligonucleotides were characterized by PAGE in Example 6. Presented hereafter is a characterization of the effects of NALC and other organic load materials on the reaction between oligonucleotides and bleach using PAGE and other characterization methods.
A. Real-time TMA Results
Ribosomal RNA was reacted with bleach in the presence of different amounts of various organic load materials. The ability of this RNA to be amplified was then tested using real-time TMA. Organic load materials included Amplification, Hybridization, Enzyme and Selection Reagents from the APTIMA COMBO 2® Assay kit (Catalog No. 1032; Gen-Probe Incorporated; San Diego, Calif.), and mixtures thereof, urine transport medium (UTM; Catalog No. 1040 APTIMA COMBO 2® Assay Urine Specimen Collection Kit for Male and Female Urine Specimens; Gen-Probe Incorporated), swab transport medium (STM), KOVA-Trol™ (Hycor Biomedical Inc.; Garden Grove, Calif.), bovine serum albumin (BSA), lithium lauryl sulfate (LLS) and human plasma. Of these compounds, UTM and Enzyme Reagent were most effective at interfering with reaction of the bleach with RNA. In one experiment, 20% commercial bleach was required to overcome the effects of UTM, which is in contrast to the very rapid and complete reaction of rRNA with 0.016% bleach in the absence of organic load materials (
B. PAGE Results
PAGE was performed using a procedure similar to that disclosed in Example 1. Briefly, a known amount of a 71-mer oligonucleotide was incubated with a formulation having a known concentration of candidate reagent. A 1× volume of 2× TBE-urea loading buffer (180 mM Tris, 180 mM boric acid, 4 mM EDTA, pH 8.0) was added to the mixture solution and vortexed for 10 seconds. Ten microliters of sample was loaded in each lane of a 10% polyacrylamide TBE-Urea gel. The gel was run in 1× TBE running buffer at 180 V for 35 to 40 minutes depending on the length of oligonucleotide. The gel then was removed from the cast and stained in 1/10,000 SYBr Green I dye solution for 20 minutes. The stained gel was imaged using a ChemiImager™ 4400.
Oligonucleotides were reacted with bleach in the presence of various concentrations of organic load compounds, and reaction products were analyzed by PAGE. Serum, Amplification Reagent and the NALC in Enzyme Dilution Buffer interfered with the reaction of bleach with the oligonucleotide (
C. RP-HPLC Results
Reverse phase (RP) HPLC was utilized to characterize nucleic acids exposed to deactivation solutions using standard procedures. Specifications for the HPLC apparatus and methodology utilized were as follows. A ZORBAX® Eclipse XDB C-8 Reverse Phase Column (Agilent Technologies, Inc.; Palo Alto, Calif.) having a 4.6 mm internal diameter and a 15 cm length was utilized. Triethyl ammonium acetate (TEAA)/acetonitrile was utilized as the mobile phase, where Buffer A contained 0.1 M TEAA and Buffer B contained 100% acetonitrile. A gradient of 5%-100% Buffer B was utilized in a time interval of 15 minutes at a flow rate of 0.5 ml/min. 50 μL, oligonucleotide samples having an optical density of 2.0 OD (oligonucleotide 26 mer=10 μM) were injected on the column and column output was detected at a wavelength of 254 nm.
Reaction of bleach with a 26 mer DNA oligomer in the presence of NALC and subsequent chromatography using RP-HPLC revealed that NALC interfered with the reaction of bleach with DNA. These results confirmed PAGE findings in Example 6.
D. Conclusions
Materials that effectively interfered with the reaction of bleach with nucleic acids were Urine Transport Medium (UTM) and the NALC in Enzyme Dilution Buffer (EDB). Materials that moderately interfered with the reaction of bleach with nucleic acids were Swab Transport Medium (STM), Hybridization Reagent, Amplification Reagent and human serum. Materials that weakly interfered with the reaction of bleach with nucleic acids (or not at all) were Selection Reagent, APTIMA COMBO 2® Assay Target Capture Reagent, lithium lauryl sulfate and KOVA-Trol™. From this analysis, it was determined that organic load material, especially materials containing primary amine and sulfhydryl groups, reacted with bleach and consumed it so that it was not all available to deactivate the nucleic acids. Loss of decontamination power of bleach at lower concentrations was not due to slow reaction rates or the need for excess hypochlorite over nucleotides, but rather consumption of bleach by other compounds.
Alternative formulations to bleach, such as solutions containing dichloroisocyanuric acid (DCC) or hydrogen peroxide and copper ions, were characterized in Examples 3 and 4 by PAGE. These and additional alternative formulations were characterized by PAGE and other assays as described hereafter.
A. PAGE Results
A 71-mer oligonucleotide was reacted with various candidate compounds and the products were analyzed using PAGE. Solutions containing DCC or hydrogen peroxide with copper sulfate were tested, among other formulations. As shown in Example 3, DCC, which is less corrosive than bleach, was as effective as bleach for deactivating the oligonucleotide, if not more so. The effects of scavengers including Enzyme Dilution Buffer (EDB) and serum on DCC were also tested and compared with their effects on bleach. Similar effects were observed as shown in
Other candidate solutions were characterized by incubating them with oligonucleotide and analyzing the resulting reaction products by PAGE. The following reagents exhibited little or no changes to nucleic acid migration or band intensity in this assay: (1) peroxymonosulfate (KHSO5) with or without copper sulfate; (2) perborate; (3) percarbonate; (4) hydrogen peroxide with KBr; and (5) NUCLEOCLEAN™ (Chemicon International, Inc.; Temecula, Calif.).
B. RP-HPLC Results
The RP-HPLC retention shift assay (described previously) was used to screen several bleach alternative candidates in the presence or absence of organic load material (NALC). Following is a summary of the efficacy of the alternative formulations tested as compared to 10% bleach, where “=” is roughly equivalent, “<” is less effective and “>” is more effective.
NaBr/NaOCl
peroxide/CuSO
4
peroxide/CuSO
4
Formulations determined by the assay as more effective than 10% bleach are shown in bold text. Accordingly, formulations comprising (a) NaBr/NaOCl or (b) peroxide/CuSO4 were as effective or more effective for deactivating nucleic acids as compared to bleach alone under the conditions of this experiment.
C. Capillary Electrophoresis Results
Ribosomal RNA was reacted with various candidate formulations in solution and the products were analyzed using a capillary electrophoresis assay. In the assay, 1 mM dichloroisocyanurate (DCC) and 17.5 mM peroxymonosulfate (VIRKON® S; DuPont Animal Health Solutions, United Kingdom), tested separately, substantially eliminated peaks corresponding to 0.72 mM rRNA oligonucleotide. In situ-generated Cl2 (10 mM peroxymonosulfate+20 mM KCl) partially eliminated 72 μM rRNA oligonucleotide. Tested separately, (a) in situ-generated Br2 (10 mM peroxymonosulfate+20 mM KBr), (b) between 10 and 100 μM dichloro-hydantoin or dibromo-hydantoin, (c) between 10 and 100 μM hypobromite, and (d) 10 mM peroxymonosulfate+metal ions (1 mM Cu2+, 1 or 10 mM Fe2+) substantially eliminated 72 μM rRNA oligonucleotide.
D. Real-Time TMA Results
Ribosomal RNA was reacted with various compounds in solution, and the ability of the RNA to be amplified was then tested using the real-time TMA assay described in Example 8. The efficacies of certain formulations are described hereafter.
VIRKON® S (Peroxymonosulfate).
The nucleic acid was reacted with a 2.5% VIRKON® S solution (about 8.7 mM peroxymonosulfate), which was a substantially lower concentration than the organic load included in the reaction (Enzyme Dilution Buffer (EDB) or Urine Transport Medium (UTM) here). Thus, 2.5% VIRKON® S solution did not substantially inactivate the nucleic acid target in the presence of 5 μL EDB or UTM.
DCC.
An 83 mM DCC solution, which was determined as approximately equivalent to 10% bleach, inactivated target in the presence of EDB.
Peroxymonosulfate/KBr.
Target rRNA in the presence of UTM was inactivated with 0.25 M peroxymonosulfate/0.25 M KBr. Other ratios tested were not as effective, and an optimum ratio is determined by varying the ratio in additional runs of the assay. At 0.25 M of each component, intensive coloration and odor were observed (due to the Br2), and after addition to UTM/Target mix, a residue formed. The residue dissolved upon a 50× dilution in water. The stability of this formulation may be characterized further by varying reaction conditions in additional runs of the assay. If formulations including these components are found to have limited stability, they can be provided in dry powder formulations and the solutions can be prepared shortly before use.
Perborate and Percarbonate.
Perborate was not sufficiently soluble at concentrations useful in solution. Percarbonate was soluble to 880 mM (roughly the equivalent of 3% peroxide). When combined with copper(II), percarbonate at this concentration reacted with nucleic acid essentially with the efficacy of 3% hydrogen peroxide. Percarbonate evolved oxygen quite readily when mixed with copper(II), however, indicating the stability of the active reagents would require additional testing by the assay. Also, when percarbonate was combined with copper(II)/piperazine, a yellow residue formed. Enhanced activity was observed in solution (as with hydrogen peroxide/copper(II)/piperazine), but the solution characteristics were not ideal (lower solubility, foamy). Accordingly, while the percarbonate solutions were effective nucleic acid deactivators, the solution properties were less favorable than hydrogen peroxide formulations. Provision of the components in dry form to prepare solutions just prior to use would overcome some of these disadvantages.
From these results, the compounds that were especially effective (at appropriate concentrations) included bleach+peroxide, KHSO5+KBr, DCC and peroxide+UTM. Compounds that were not as effective under the particular conditions of the experiments include 15% peroxide alone; peroxide+potassium, sodium or iron ions; 5 mM bromo- or chloro-hydantoin and KMnO4. The effectiveness of peroxide+copper was not determined at the time of these studies since the corresponding control failed (i.e., the reaction mix itself inhibited TMA). It also was determined 1 mM CuSO4/3% H2O2 inactivated rRNA oligonucleotide to a greater degree than 1 mM CuBr2/3% H2O2, CuCl2/3% H2O2, or Cu(NO3)2/3% H2O2. Additionally, 1 mM Cu(OAc)2/3% H2O2 inactivated rRNA to a greater degree than 1 mM CuSO4/3% H2O2.
Results from the analytical methods described herein are summarized in the following Table. In the Table, “+” indicates the compound was deactivating; “−” indicates the compound was not substantially deactivating under the conditions and by the methods used; “*” indicates equivocal results were obtained and further results can be obtained by repeating the assay at the conditions shown; no notation indicates the conditions were not examined by the indicated assay.
In this Table, DNA AWAY™ is an alkali hydroxide solution (Molecular BioProducts, Inc., San Diego, Calif.; Cat. No. 7010), DNAZAP™ is a pair of PCR DNA degradation solutions (Ambion, Inc., Austin, Tex.; Cat. No. 9890), DNA-OFF™ is a non-alkaline cleaning solution (Q-biogene, Inc., Irvine, Calif.; Cat. No. QD0500), and NUCLEOCLEAN™ is a PCR decontamination solution (Chemicon International, Temecula, Calif.; Cat. No. 3097S). These results showed bleach (at reduced levels), dichloroisocyanurate (DCC), H2O2/Cu(II), peroxymonosulfate, peroxymonosulfate/KBr (generates Br2) and hypobromite displayed especially potent nucleic acid deactivation activity in solution.
Multiple formulations and various methods of applying them were characterized for nucleic acid deactivation efficacy in an APTIMA COMBO 2® Assay (described hereafter) and associated components. Following is a list of materials utilized for the assay and characterization process:
Amplification Reagent
Amplification Reconstitution Solution
Target Capture Reagent
Target Capture Reagent B
CT Positive Control
GC Positive Control
Oil Reagent
Wash Buffer
Urine Transport Media (UTM)
Swab Transport Media (STM)
Enzyme Reagent
Enzyme Reconstitution Solution
CT rRNA
GC rRNA
KOVA-Trol™ (Normal)
Probe Reagent
Probe recon Solution
Selection Reagent
Detection Reagent I
Detection Reagent II
Endocervical swabs
Household liquid bleach (Chlorox®)
Dichloroisocyanurate (DCC)
Household hydrogen peroxide, 3% U.S.P. (H2O2)
Cupric sulfate (Cu(II))
Peroxymonosulfate (KHSO5)
Following is a description of several analytical processes employed for the characterization procedures.
A. Preparation of Positive and Negative Amplification Reactions
Oil reagent (200 microliters) was added to 80 reaction tubes (12×75 mm). 4.2×1010 copies of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) rRNA were spiked into 3.15 ml of reconstituted Amplification Reagent. Seventy-five microliters (1×109 copies (˜2.5 ng)) of this spiked Amplification Reagent was added to 40 of the reaction tubes (positive samples). Seventy-five microliters of Amplification Reagent without target (negative samples) was added to the other 40 tubes. All 80 samples were incubated for 10 min at 62° C., then 5 min at 42° C. Twenty-five microliters of reconstituted Enzyme Reagent was added to each tube, the rack was removed from the water bath, the rack was shaken to mix tube contents, and the rack then was quickly returned to the water bath. Reaction tube contents were incubated 60 min at 42° C. (amplification), then for 10 min at 80° C. (inactivation of enzymes). Thirty-eight of the positive samples and 38 of the negative samples were pooled and oil was removed from each pool. The two remaining positive and negative samples were assayed according to the standard APTIMA COMBO 2® manual assay protocol (described above).
B. Preparation of CT+GC rRNA Samples
5×108 copies of CT and GC rRNA prepared by standard procedures were added to 100 microliters of UTM:KOVA-Trol™ in a 1:1 ratio (in some cases (indicated in the table below), samples were added to 100 microliters of STM). The desired number of replicates of this mixture can be prepared as a pool before spotting on the surface.
C. Decontamination Assay Protocol
Surface.
Decontamination assays were performed on 2×4 ft sections of ChemSurf laboratory bench (“surface”). Before, between and after the various experiments, the surface was cleaned with a 50% bleach solution (household liquid bleach (e.g., ULTRA CLOROX® BLEACH) diluted 1:1 with water) followed by a water rinse. Wiping was accomplished with paper towels or large Kimwipes.
Sample Application.
One-hundred microliters of each selected sample (see below) was applied to the surface in a circular spot of about 1.5 inches in diameter. Approximately eight samples were applied, evenly spaced, on the surface. Samples were allowed to dry for approximately 15-30 min.
Sample Collection.
A Gen-Probe Incorporated endocervical swab was placed in 3 ml of Swab Transport Medium (STM) in a transport tube labeled with the name of the sample to be collected. The swab was removed from the transport tube and, using a circular motion, each spot was swabbed where the sample was applied. Each swab was returned to its transport tube, the end of the swab was carefully snapped-off at the scoreline, and the tube was closed using its penetrable cap, and then vortexed.
Deactivation Formulations Tested.
Among the formulations tested were:
Decontamination Protocol.
The decontamination protocol utilized included the following steps:
1) The surface was cleaned (see above).
2) For negative controls a sample was collected from a circular area of ˜1.5 inch in diameter, selected randomly on the surface, before any positive samples were applied to the surface.
3) Approximately eight replicate CT & GC rRNA in UTM:KOVA-Trol™ (1:1) (or STM) samples (100 microliters each) were spotted and evenly spaced on the surface.
4) Spot 1 was treated with decontamination condition “a” above (10% bleach, one application) as follows: the area containing the sample (about 7×7 inch square with sample in the center) was wetted with approximately 2 ml of reagent (in some cases (indicated in table below) approximately 3 ml was used) and then immediately wiped with a paper towel or large Kimwipe until it was dry (the towel sometimes was flipped over during the process if necessary to complete the drying). The towel and the glove that was on the hand that performed the wiping were carefully discarded (the other glove was discarded if there was a possibility it became contaminated). A sample from the original spot of application was collected using an endocervical swab as described above.
5) Spot 2 was treated with condition “b” using the same general method described in “4” above, but also with a second application of the decontamination reagent.
6) The sample spots then were treated with the decontamination conditions listed above until all samples on the surface were treated.
7) The surface was cleaned as described above, and a sufficient number of sample replicates were applied to complete testing of the decontamination conditions plus one additional spot (to be used as a positive control).
8) Testing of decontamination conditions then was completed.
9) For last remaining sample spot (positive control), the spot was swabbed directly without any application of decontamination reagent.
10) Steps 1-9 were completed for the negative amplification and the positive amplification samples.
Assay Protocol.
Replicates (2×400 μL) of each of the samples collected in the decontamination studies described above were assayed using an APTIMA COMBO 2® Assay (Catalog No. 1032; Gen-Probe Incorporated; San Diego, Calif.), described below. The assay amplified Chlamydia trachomatis (referred to herein as “CT” or “Ctr”) and Neisseria gonorrhoeae (referred to herein as “GC” or “Ngo”) template rRNA prepared by standard methodology (“positive Amp”) and also was run without template rRNA (“negative Amp”). The assay was performed using the following general protocol:
Before assay, Ngo/Ctr NA samples were prepared by spiking amplification-negative samples with 0.5 fg of CT rRNA (about 2×102 copies) and 50 fg of GC rRNA (about 2×104 copies). In addition, 5-10 negative assay controls (STM only) were performed. Acceptance criteria were as follows:
Follow-Up Testing.
Any samples not meeting the above specifications were stored at room temperature and re-tested the following day. The acceptance criteria for the follow-up testing are the same as the acceptance criteria for the initial testing (see above).
D. Characterization Results of Nucleic Acid Deactivation Using Various Formulations and Application Methods
The following table depicts results collected using the protocols described above. “NA Source” is the nucleic acid source, “# App” is the number of reagent applications, “kRLU” is relative light units times a factor of 1000, and “pip” is piperazine. Expected Ctr and Ngo results are negative (Neg) for Ngo/Ctr rRNA, Neg for Pos Amplification and positive (Pos) for Neg Amp. The majority of Ctr and Ngo results from the tests were valid, and invalid results are not included in the Table.
Effectiveness of Reagents Used for Surface Decontamination
The results in the table show bleach-containing reagents—including those that also contain a corrosion inhibitor and a surfactant—effectively deactivated rRNA and positive and negative TMA reactions on surfaces. The same was true for solutions containing 40 mM DCC. Solutions containing peroxide and copper effectively deactivated rRNA on surfaces, and were not as efficacious as bleach for consistently decontaminating surfaces of positive or negative TMA reactions under the conditions tested. Adding piperazine or HEPES to the peroxide/copper solutions did not significantly alter deactivation performance on surfaces under the conditions tested. Peroxymonosulfate deactivated rRNA on surfaces, but not positive and negative TMA reactions under the conditions tested.
Effects of including corrosion inhibitors, surfactants and fragrances in nucleic acid deactivation formulations were assessed. Bleach, and to a lesser but still significant extent DCC, cause corrosion of metals and other materials. Nucleic acid deactivation activity of various candidate anti-corrosion compounds, including the sodium salts of phosphate (PB), borate, bicarbonate and dodecyl sulfate (SDS), were tested in solution prior to analysis using real-time TMA and PAGE (e.g., Example 8 and Example 1). Studies were performed to test the activity of bleach and DCC when mixed together with the candidate corrosion inhibitors. Phosphate at pH 6.4 and 7.5 destabilized bleach (loss of activity increased with time) whereas phosphate at pH 9.1 or 9.5 did not. The converse was true for DCC, where the higher pH phosphate's (9.1 and 9.5) were destabilizing whereas the lower pH phosphate's (6.4 and 7.5) were not. Bleach was stable in borate at pH 7.6 or 9.1 and bicarbonate at pH 9.3. SDS did not have any apparent effect on the activity of bleach.
Anti-corrosion formulations with bleach were also tested with the surface decontamination protocol described in Example 12. All formulations tested were determined to be effective, thus demonstrating the anti-corrosion agents have no apparent negative effect on bleach activity. One application (“1 app”) is one application of the reagent and two applications (“2 app”) is two applications of the reagent. Results from the analysis are presented hereafter:
An assay for assessing corrosion was devised. The assay comprised soaking stainless steel bolts (1″ long, ⅛″ diameter, standard thread, hex-head stainless steel bolts) in candidate solutions and visually scoring corrosion over time. Results from the corrosion inhibition studies are summarized hereafter:
Detergents and surfactants also were tested for effects on the physical properties of bleach solutions on surfaces. These agents decreased surface tension and allowed for more complete wetting of the surface with the bleach solution (typically 0.6% hypochlorite). To decrease foaming of the solution when applied to the surface, detergent concentration was lowered to a level that minimized foaming but retained effective surfactant qualities. SDS and LLS levels of approximately 0.005% to 0.02% (w/v) minimized foaming in this particular application.
Effects of fragrances on activity and stability of bleach and DCC also were tested. Among the fragrances tested were 2141-BG, 2145-BG, and two other custom fragrances from International Flavors and Fragrance. The fragrances exhibited no detectable effect on activity and stability of 10% bleach and DCC according to PAGE analysis. Also, the fragrances exhibited no detectable effect on corrosion inhibition of various compounds tested (e.g., phosphate and bicarbonate).
As a culmination of results for corrosion inhibitors, detergent/surfactants and fragrances, formulations of these reagents with bleach were developed. Unexpectedly, the balance between components was critical for maintaining physical stability of the solution. There were various combinations of these components that were successful in this regard. One formulation was as follows:
corrosion inhibitor/detergent/fragrance (6.7× concentrate): 600 mM bicarbonate (pH 9.3), 0.1% SDS, 0.05% 2141-BG
finished decontamination reagent: 0.6% hypochlorite, 90 mM bicarbonate (pH 9.3), 0.015% SDS, 0.0075% 2141-BG.
Solutions comprising peroxide and copper were further characterized. It was discovered that UTM stimulated inactivation of rRNA in solutions containing peroxide and Cu(II). The effects of the individual components of the UTM formulation (150 mM HEPES, pH 7.6, 300 mM LLS, 10 mM (NH4)2SO4) were examined, and it was discovered that the HEPES was responsible for the stimulation. Effects of pH and concentration on the observed inactivation of rRNA then was examined. The activity of different chemical components of HEPES (ethanol, ethanesulfonic acid and piperazine) and PIPES, a buffer similar to HEPES, also were examined. It was discovered piperazine was essentially as active as HEPES, and piperazine at a pH of 5.5 was utilized for further characterization. It also was discovered that piperazine stabilized Cu(II) in solution in a chemical configuration that maintains activity with peroxide for inactivating nucleic acids.
Selected reagents were stored under a variety of conditions. At selected time points, the formulations were assayed for the ability to deactivate target nucleic acid using a solution assay, in which rRNA was incubated with reagents in solution, diluted, and an aliquot was assayed using real-time TMA (Example 8). Incubation conditions were at room temperature with no protection from light. Results are provided hereafter.
I. 40 mM CuSO4/1M piperazine (acetate), pH 5.5
II. 80 mM CuSO4/1M piperazine (acetate), pH 5.5
III. 200 mM CuSO4 (in water)
A. Stored at Room Temperature, No Protection from Light
IV. 10% Bleach/Sodium Bicarbonate/SDS/IFF
A. 10% Bleach/0.2 M Sodium Bicarbonate (pH 9.3)/0.05% SDS
B. 10% Bleach/0.08M Sodium Bicarbonate (pH 9.3)/0.020% SDS/0.025%2141-BG
C. 10% Bleach/0.09M Sodium Bicarbonate (pH 9.3)/0.015% SDS/0.0075% 2141-BG
V. Sodium Bicarbonate/SDS/2141-BG (then Added to “Fresh” Bleach)
A. 600 mM Sodium Bicarbonate (pH 9.3)/0.1% SDS/0.05% 2141-BG (6.7× Solution)
B. 600 mM Sodium Bicarbonate (pH 9.3)/0.1% SDS/0.05% 2145-BG (6.7× Solution)
Formulations and procedures for deactivating nucleic acid on several pieces of laboratory equipment, including a vacuum trap system, an aspiration manifold, a rack and a deck, were assessed for efficacy.
A. Vacuum Trap System
A vacuum system comprising an aspiration manifold, two traps, an inline filter, and a vacuum pump connected in series by tubing was utilized for conducting an amplification assay after multiple target capture runs (both Ctr and Ngo rRNA). Contamination was assessed without adding bleach to the first trap. After the runs, swab samples were taken from various locations in the vacuum system and assayed for presence of Ctr and Ngo rRNA using the real-time TMA assay presented in Example 8. No detectable contamination with Ngo rRNA was identified outside of the first trap. Contamination with Ctr rRNA was identified in the tubing between the first and second traps, in the second trap and in the tubing between the second trap and the inline filter, and no contamination was detected after the inline filter. These results demonstrated that no detectable Ngo or Ctr rRNA escaped into the environment, and it is therefore feasible to not to include bleach in the first trap during usage.
B. Aspiration Manifold
One protocol for decontaminating a target capture aspiration manifold utilized for a TMA assay (APTIMA COMBO 2® Assay, Catalog No. 1032, Gen-Probe Incorporated, San Diego, Calif.) included the step of soaking the manifold in 50% bleach for 10 minutes followed by thorough rinsing with water. This procedure resulted in corrosion of the manifold and the relatively frequent need to replace it.
To test other decontamination protocols and agents, the manifold was intentionally contaminated, decontamination was attempted, then contamination levels measured. Each of target negative samples (10 replicates) remained negative using the contaminated manifold, demonstrating that the target capture system prevented contamination from entering new samples. In one decontamination protocol, it was discovered that leaving the manifold attached to the system and aspirating nucleic acid deactivation formulations through it successfully decontaminated the manifold. In such a procedure, it was determined 0.6% hypochlorite (10% bleach) or 40 mM DCC (followed by a water rinse) successfully decontaminated the manifold. A hydrogen peroxide/copper solution also successfully decontaminated the manifold, but this reagent was not as suitable for routine use as it could vigorously evolve oxygen when under reduced pressure in the vacuum system. It was determined that aspirating approximately 50 ml (about 5 ml per nozzle) of a 0.6% hypochlorite solution (with corrosion inhibitor, detergent and fragrance) followed by approximately 50 ml (about 5 ml per nozzle) of water, and then leaving the vacuum pump on for at least 1 minute sufficiently decontaminated the aspiration manifold.
C. Tecan Deck Decontamination
Leading bleach alternative candidates were tested for decontamination of the deck of the DTS® TECAN GENESIS System (Catalog No. 5216 or 5203; Gen-Probe Incorporated; San Diego, Calif.). The following results were observed.
Thus, multiple formulations and procedures effectively deactivated nucleic acids that contaminated various laboratory equipment.
Efficacy of two decontamination reagents and methods in a clinical laboratory setting were characterized at two sites. Reagent 1 (3% H2O2, 2 mM cupric sulfate) and Reagent 2 (0.6% hypochlorite, 90 mM bicarbonate, 0.015% SDS, 0.0075% 2141-BG), used according to the prescribed protocol provided to each site (see below), were equivalent to the protocol using 50% bleach described in the package insert for the APTIMA COMBO 2® Assay kit (Gen-Probe Incorporated Catalog No. 1032) and at http address www.gen-probe.com/pdfs/pi/IN0037-04RevA.pdf, and yielded effective nucleic acid deactivation and decontamination control for nucleic acid assay procedures in a clinical laboratory setting.
A. Materials
Following is a list of materials utilized at each site:
B. Procedures
The following procedures were utilized at each site. For each rack of samples (up to 10 Ten-Tube Units (TTUs; Catalog No. TU0022; Gen-Probe Incorporated) run in the APTIMA COMBO 2® Assay, included were the usual two-run controls (Positive Control, CT and Positive Control, GC), two Dual Positive Controls (see Materials), 16 Negative Controls (see Materials) and up to 80 patient specimens. The assay was performed according to the standard protocol (package insert).
If the two-run controls met run control criteria, the run was valid (PASS). If one or both of the run controls did not meet run control criteria, the run was invalid (FAIL) and all results in the same run were invalid and were not reported. The run was then repeated. Also, as usual for patient samples, initial equivocal or invalid results were repeated.
Described below are the three phases of the research study. Each stage was run between 2 and 4 weeks as less than 2 weeks might not allow adequate evaluation of the decontamination protocol. Three weeks was determined as being ideal, and the maximum duration was four weeks. The entire study was expected to be completed in 9 weeks, with a maximum duration of 12 weeks. For each phase of the study, 15 racks of samples were assayed, with all containing the appropriate controls as described above.
Phase 1:
The standard APTIMA COMBO 2® protocol utilizing 50% bleach was used for decontamination as described in the package insert (http address www.gen-probe.com/pdfs/pi/IN0037-04RevA.pdf). This approach was utilized to establish a baseline of results for comparison with results obtained when the test decontamination protocol was used.
Phase 2:
The test decontamination protocol was utilized (see below).
Phase 3:
The test decontamination protocol (see below) was utilized, except Reagent 2 was used when the protocol called for use of Reagent 1. Reagent 2 still was utilized when the protocol called for use of Reagent 2.
1. Rack Set-Up
Each laboratory was instructed to utilize the following procedure for setting-up racks of samples:
2. General Decontamination Protocol
Each laboratory was instructed to apply good physical containment techniques in order to guard against spread of contamination in the lab while decontaminating each workspace. Each laboratory was cautioned that the glove on the hand used for cleaning would become contaminated and that touching clean objects with this hand should be avoided. It was recommended that one hand should be reserved for cleaning only and the other hand (clean) for application of reagent only. It also was recommended that used towels and gloves should be discarded in a receptacle in which they would be well-contained, making sure that no dripping occurred between the area undergoing decontamination and the receptacle.
3. Reagent Preparation
Each laboratory was instructed to prepare the following reagents using the procedures outlined below:
a) Prepare Reagent 1B (every 2 weeks)
b) Prepare Reagent 1 (daily)
c) Prepare Reagent 2 (every 2 weeks)
The recipe provided below is for the preparation of 1 liter of Reagent 2. The actual amount made is to be determined based on the anticipated reagent usage in a given laboratory. The preparation of Reagent 2 to be used for cleaning racks and other equipment and may be performed in the vessel used for soaking
4. Pre-Assay Procedures
Each laboratory was instructed to perform the following pre-assay procedures.
5. Post-Specimen Preparation Procedures
Each laboratory was instructed to perform the following post-specimen preparation procedures:
6. Post-Target Capture Procedures
Each laboratory was instructed to employ the following post-target capture procedures:
7. Amplification Reaction b Procedures
Each laboratory was instructed to perform the following procedures after each amplification reaction was started, which is the last step performed in the pre-amp area. After starting the reaction, each laboratory was instructed to clean the bench tops surrounding the water baths, the handles to the lids of the water baths and the pipettors using Reagent 1 according to the procedures described above. Each laboratory was instructed to carefully discard both gloves after performing these procedures.
8. Post-Amp Area Procedures
Each laboratory was provided with the following instructions concerning post-amplification area procedures. After the last cleaning in the pre-amp area was completed and new gloves were adorned, each laboratory was instructed to immediately turn on the 62° C. water bath after entering the pre-amp area. Instructions also were to pre-clean all surfaces in the post-amp area (lab benches, pipettors, handles, and others) using Reagent 2 according to the specific procedures described above, and then to carefully discard both gloves.
9. Post Amplification Procedures
Each laboratory was provided with the following instructions concerning post-amplification procedures. After adorning a clean set of gloves, instructions were provided to carefully remove the rack(s) from the 42° C. water bath, and to avoid contaminating the lid of the water bath.
10. Post Detection Procedures
Each laboratory was provided with the following instructions concerning post-detection procedures. Instructions were to (a) remove TTU's from the luminometer and deactivate reactions using the current procedure in the product insert; (b) clean all surfaces (bench surfaces, pipettors, handle on water bath lid, exterior of the LEADER® HC+Luminometer, and others) using Reagent 2 according to the specific procedures described above, (c) every two weeks, or as needed, clean the interior of the HC+ with DI water as currently described in the operator's manual and soak the HC+ cassettes in Reagent 2 for 30-60 minutes, and (d) carefully discard both gloves.
11. Acceptance Criteria
Each laboratory was instructed to use the following acceptance criteria.
C. Results
Reagents 1 and 2 used according to the prescribed protocol were equivalent to the protocol using 50% bleach provided with the APTIMA COMBO 2® Assay kit, and yielded effective decontamination control for the APTIMA COMBO 2® Assay in a clinical setting.
Analysis of Negative and Positive Control Data
When the new decontamination reagents and protocol were used, 540 of 540 (100%) control samples for Phase II and 554 of 558 (99.3%) control samples for Phase III yielded the expected results. When 50% bleach with the standard protocol was used (Phase I), 535 of 540 (99.1%) control samples yielded the expected results. A Fisher's exact test (a statistical hypothesis test method to demonstrate statistical differences between multiple groups with qualitative outcomes; Categorical Data Analysis by Alan Agresti (1990), pages 59-67, 68, 70, 78, 488, John Wiley & Sons, New York, N.Y.) was performed on the data using SAS Version 8.2 software. It is widely accepted that P<0.05 suggests a significant difference between groups while P>0.05 is indicative of no statistical difference. The Fisher's exact test yielded a p value of 0.625 for assays run at Laboratory 1 and 0.110 for assays run at Laboratory II. These results indicate statistical equivalence between the conditions of all three phases.
The entirety of each patent, patent application, publication and document referenced herein hereby is incorporated by reference. Citation of the above patents, patent applications, publications and documents is not an admission that any of the foregoing is pertinent prior art, nor does it constitute any admission as to the contents or date of these publications or documents. Incorporation by reference of these documents, standing alone, should not be construed as an assertion or admission that any portion of the contents of any document is considered to be essential material for satisfying any national or regional statutory disclosure requirement for patent applications. Notwithstanding, the right is reserved for relying upon any of such documents, where appropriate, for providing material deemed essential to the claimed subject matter by an examining authority or court.
Modifications may be made to the foregoing without departing from the basic aspects of the invention. Although the invention has been described in substantial detail with reference to one or more specific embodiments, those of ordinary skill in the art will recognize that changes may be made to the embodiments specifically disclosed in this application, and yet these modifications and improvements are within the scope and spirit of the invention. The invention illustratively described herein suitably may be practiced in the absence of any element(s) not specifically disclosed herein. Thus, for example, in each instance herein any of the terms “comprising”, “consisting essentially of”, and “consisting of” may be replaced with either of the other two terms. Thus, the terms and expressions which have been employed are used as terms of description and not of limitation, equivalents of the features shown and described, or portions thereof, are not excluded, and it is recognized that various modifications are possible within the scope of the invention. Embodiments of the invention are set forth in the following claims.
This application is a division of U.S. patent application Ser. No. 11/073,085, filed on Mar. 4, 2005, which claims the benefit of U.S. Provisional Patent Application No. 60/550,749, filed on Mar. 5, 2004, the contents of which are hereby incorporated herein by reference in their entirety.
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| Number | Date | Country | |
|---|---|---|---|
| 20120260951 A1 | Oct 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60550749 | Mar 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11073085 | Mar 2005 | US |
| Child | 13531924 | US |
