Patent Application
20130220835
1. Field of the Invention
The present invention relates, in general, to medical devices and, in particular, to polymeric nanoparticle compositions, biosensors containing polymeric nanoparticles and related methods.
2. Description of Related Art
The determination (e.g., detection and/or concentration measurement) of an analyte in a fluid sample is of particular interest in the medical field. For example, it can be desirable to determine glucose, ketone bodies, cholesterol, lipoproteins, triglycerides, acetaminophen and/or HbA1c concentrations in a sample of a bodily fluid such as urine, blood, plasma or interstitial fluid. Such determinations can be achieved using sensors, based on, for example, visual, photometric or electrochemical techniques. Conventional electrochemical-based analytical test strips are described in, for example, U.S. Pat. Nos. 5,708,247 and 6,284,125, each of which is hereby incorporated in full by reference.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention, in which:
The following detailed description should be read with reference to the drawings, in which like elements in different drawings are identically numbered. The drawings, which are not necessarily to scale, depict exemplary embodiments for the purpose of explanation only and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.
As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein
In general, biosensors (such as an electrochemical-based analytical test strip configured for the determination of glucose in a whole blood sample) according to embodiments of the present invention include a substrate, an electrode disposed on the substrate and a uric acid scavenger layer containing polymeric nanoparticles that include polymerized vinyl-4,6-diamino-1,3,5-triazine (also referred to herein as polyVDAT nanoparticles). The polyVDAT nanoparticles included in biosensors according to embodiments of the present invention can include only polymerized vinyl-4,6-diamino-1,3,5-triazine (i.e., vinyl-4,6-diamino-1,3,5-triazine molecules polymerized directly to other vinyl-4,6-diamino-1,3,5-triazine molecules as depicted in
Biosensors according to embodiments of the present invention are beneficial in that the uric acid scavenging layer reduces the interfering effect of uric acid in a bodily fluid sample applied to the biosensor, thus increasing the accuracy of the biosensor. Uric acid can behave as an interferent by, for example, exhibiting either direct electroactive behavior at the electrode of the biosensor or by being oxidized by enzymatic reagents (such as ferricyanide) included in the biosensor. Such interfering effects are mitigated once uric acid is bound to the polyVDAT nanoparticles through hydrogen bonding (i.e., scavenged).
In general, aqueous vinyl-4,6-diamino-1,3,5-triazine compositions according to embodiments of the present invention include polyVDAT nanoparticles and water with the polyVDAT nanoparticles being present as a dispersion in the water. Typically, to avoid nanoparticle agglomeration during the nanoparticle synthesis, such aqueous vinyl-4,6-diamino-1,3,5-triazine compositions include polyVDAT nanoparticles at a w/w % of no more than 5%. However, the w/w % of polyVDAT can exceed 5% if deleterious agglomeration does not occur during/or after the nanoparticle synthesis. Aqueous vinyl-4,6-diamino-1,3,5-triazine compositions according to embodiments of the present invention are particularly advantageous in comparison to non-aqueous compositions due to their simplicity, the ability to readily add further components such as the commercially available binder Pluronic P103, and their compatibility with aqueous enzymatic reagents commonly used in biosensor manufacturing.
A method for determining an analyte in a bodily fluid sample containing uric acid according to embodiments of the present invention includes applying a bodily fluid sample (such as a whole blood sample) containing uric acid to a biosensor such that the bodily fluid sample comes into contact with a uric acid scavenger layer containing polymeric vinyl-4,6-diamino-1,3,5-triazine (polyVDAT) nanoparticles, and determining the analyte based on an electronic signal produced by the biosensor.
The term “nanoparticle” as used herein refers to particles that are of a size, or have a structural feature of a size, that causes them to display properties or behaviors that are different than the properties of the bulk material. For example, polyVDAT nanoparticles according to embodiments of the present invention can be formulated as a free-flowing dispersion in a liquid (e.g., water) without changing their dimensions or shape.
The term “dispersion” as used herein refers to a mixture, in which fine particles of one or more than one substance (for example, polyVDAT nanoparticles) are scattered throughout another substance or mixture of substances (for example, water). Dispersions are classed as suspensions.
The term “biosensor” as used herein refers to an analytical device that includes a biological material (e.g., an enzyme) associated or integrated with a physiochemical transducer system (such as an electrochemical-based system). Examples include immune-sensors, enzyme-based biosensors (such as electrochemical-based analytical test strips configured for the determination of an analyte in a whole blood sample) and whole-cell based biosensors. Such biosensors typically produce an electronic signal that is proportional to the concentration of a predetermined analyte or group of analytes.
Uric acid is a known interferent for electrochemical-based biosensors. Moreover, the concentration of uric acid in bodily fluid samples (e.g., blood samples and plasma samples) can vary from person to person based on their gender, health and medications. Therefore, the presence of uric acid in a bodily fluid sample applied to a biosensor can lead to inaccuracies in biosensor results. PolyVDAT can scavenge uric acid via hydrogen bonding in biological fluids at a neutral/or physiological pH. However, polyVDAT bulk material is only water soluble at low (acidic) pH (<4.0) and is, therefore, not compatible with typical biosensors or their manufacturing processes.
Referring to
PolyVDAT nanoparticles created via the emulsifier-free emulsion polymerization have nanoparticle surfaces with the VDAT functional groups exposed (which is beneficial for hydrogen bonding with uric acid) have large surface areas that enable fast and effective uric acid scavenging and have a diameter that is compatible with conventional screen-printing and syringe dispensing application techniques.
An aqueous dispersion of polyVDAT nanoparticles was created by synthesizing polyVDAT in a 1 liter glass reactor vessel as follows. 600 grams of deionized water was added to the reactor vessel and heated to 70 degrees Celsius. 20.0 g VDAT (commercially available from TCI America) and 0.2 g 2,2′-azobis-(2-amidinopropane)hydrochloride were dissolved in 250 g dimethyl sulfoxide (DMSO) in a 500 ml round-bottom glass flask which was equipped with magnetic stirrer bars, nitrogen inlets and outlets. Flowing nitrogen was employed to deoxygenate the reactor vessel and the round-bottom flask, which were under agitation.
The solution in the round-bottom flask was then fed into the reactor at a flow rate of approximately 0.8 ml per minute and the polymerization continued for 15 hours. The resulting product was purified by dialysis in cellulose tubing (Sigmal-Aldrich, product car. No. D9777) against DDI water over 5 days with daily change of the water.
The polyVDAT nanoparticle synthesis of example 2 was identical to that of example 1 with the exception that 10 g of VDAT (commercially available from TCI America) and 0.5 g potassium persulfate was dissolved in 150 ml MDSO and fed continuously to the reactor at a flow rate of approximately 0.3 mL per minute.
Referring to
A solution of 2% w/w of dispersion of polyVDAT nanoparticles (created per the synthesis of Example 1) and 0.5% w/w of Pluronic P103 (added as a binder to maintain the integrity of the deposited uric acid scavenger layer) in water was incorporated into an electrochemical-based analytical test strip configured for the determination of glucose in a whole blood sample. The polyVDAT nanoparticles were included in the electrochemical-based analytical test strip as a uric acid scavenger layer with a thickness in the range of 0.5 to 1.5 microns disposed on top of an enzymatic reagent layer (see
The data of
Referring to
Electrically-insulating substrate layer 120 can be any suitable electrically-insulating substrate known to one skilled in the art including, for example, a nylon substrate, polycarbonate substrate, a polyimide substrate, a polyvinyl chloride substrate, a polyethylene substrate, a polypropylene substrate, a glycolated polyester (PETG) substrate, or a polyester substrate. The electrically-insulating substrate can have any suitable dimensions including, for example, a width dimension of about 5 mm, a length dimension of about 27 mm and a thickness dimension of about 0.5 mm.
Insulation layer 160 can be formed, for example, from a screen printable insulating ink. Such a screen printable insulating ink is commercially available from Ercon of Wareham, Mass. U.S.A. under the name “Insulayer.” Patterned spacer layer 200 can be formed, for example, from a screen-printable pressure sensitive adhesive commercially available from Apollo Adhesives, Tamworth, Staffordshire, UK.
Hydrophilic layer 220 can be, for example, a clear film with hydrophilic properties that promote wetting and filling of electrochemical-based analytical test strip 100 by a fluid sample (e.g., a whole blood sample). Such clear films are commercially available from, for example, 3M of Minneapolis, Minn. U.S.A. Top film 240 can be, for example, a clear film overprinted by black decorative ink. A suitable clear film is commercially available from Tape Specialities, Tring, Hertfordshire, UK.
Combined enzymatic reagent and uric acid scavenger layer 180 can include, in addition to polyVDAT nanoparticles, any suitable enzymatic reagents, with the selection of enzymatic reagents being dependent on the analyte to be determined. For example, if glucose is to be determined in a blood sample, combined enzymatic reagent and uric acid scavenger layer 180 can include glucose oxidase or glucose dehydrogenase along with other components necessary for functional operation. Further details regarding enzymatic reagent layers, and electrochemical-based analytical test strips in general, are in U.S. Pat. No. 6,241,862, the contents of which are hereby fully incorporated by reference.
Combined enzymatic reagent and uric acid scavenger layer 180 contains polyVDAT nanoparticles as illustrated in
The configuration of
Electrochemical-based analytical test strip 100 can be manufactured, for example, by the sequential aligned formation of patterned conductor layer 140, insulation layer 160 (with electrode exposure window 170 extending therethrough), combined enzymatic reagent and uric acid scavenger layer 180, patterned spacer layer 200, hydrophilic layer 220 and top film 240 onto electrically-insulating substrate layer 120. Any suitable techniques known to one skilled in the art can be used to accomplish such sequential aligned formation, including, for example, screen printing, photolithography, photogravure, chemical vapour deposition and tape lamination techniques.
Once apprised of the present disclosure, one skilled in the art will recognize that method 600 can be readily modified to incorporate any of the techniques, benefits and characteristics of biosensors and aqueous vinyl-4,6-diamino-1,3,5-triazine (VDAT) compositions according to embodiments of the present invention and described herein.
While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that compositions, devices and methods within the scope of these claims and their equivalents be covered thereby.
