Patent Application
20120251458
The present invention relates to the use of one or more natural dyes, alone or in combination with other dyes, for preparation of a composition to stain membranes and biological structures in order to facilitate their identification during surgical procedures and to the use of one or more natural dyes, alone or in combination with other dyes, to stain membranes and biological structures in order to facilitate their identification during surgical procedures and their compositions. The present invention also relates to the use of one or more natural dye compositions that protect tissues and cells exposed during surgical procedures from damage by light. The present invention also relates to the use of one or more natural dyes, alone or in combination with synthetic dyes, for histopathological staining, both in vitro and on the surface of the eye. The present invention further relates to the topical use of one or more natural compositions inside the eye.
Surgical procedures, in various fields of medicine, often require the visualization and, in some cases, the removal of delicate membranes, which in most cases are thin and semitransparent. During some surgical procedures, it is necessary to remove these membranes. This step is technically very complex, given the difficulty of identifying each membrane adequately.
The intraoperative utilization of vital dyes for staining of human tissues has been established for more than three decades. The use of vital dyes in ophthalmology to stain retinal tissues dates back to the last century.35 Beginning with Sorsby in 193936 and later Gifford in 1940,37 ophthalmologists began injecting Kiton-fast-green V, Xylene-Fast-green B, and fluorescein intravenously. In 1969, Kutschera began injecting patent blue intravítreally to stain retinal tissue and determine retinal breaks in retinal detachments.38
The introduction of vitreoretinal surgery, pars plana vitrectomy, allowed the treatment of serious diseases of the retina such as diabetic retinopathy, macular hole and retinal detachment. The vitrectomy surgical technique involves removing the intraocular vitreous gel, taking off all pre-retinal membranes, and restoring the ocular volume with a balanced salt solution, gas or silicone oil. The removal of pre-retinal membranes such as in the treatment of proliferative vitreoretinopathy, as a consequence of retinal detachment, fibroglials epiretinal membranes and internal limiting membrane (ILM), consists of a technically difficult surgical step due to the thin and semi-transparent nature of the tissues1,2. Several studies have shown retinal complications caused iatrogenically by the action of removing these micro-structures. The use of intraoperative dyes in chromovitrectomy is one of the most recent advances in vitreoretinal surgery3. This technique was first described by Burk et al. in 2000. In this work the vital dye indocyanine green (ICG) showed high affinity for fine ILM4. The previously difficult task of removing the ILM and epiretinal membranes in vitreoretinal surgery was made much easier, increasing the rates of anatomic and functional success5-6. However, the initial enthusiasm was replaced by concern after clinical trials demonstrated clinical postoperative complications related to use of ICG such as visual field and retinal pigment epithelium changes7-12. Studies in vitro and in vivo in different animal models such as mice, rabbits and pigs, have determined dose-dependent ICG toxicity in retinal cells13-16. The harmful effect of ICG during chromovitrectomy motivated the scientific community to research vital dyes that are less toxic. Some of the first dyes used in research and clinical use in chromovitrectomy are trypan blue (AT) and patent blue (AP). However the acceptance of these dyes has been limited because both have low chemical affinity for ILM and other pre-retinal membranes, and there are no precise indicators of their biosecurity17-21.
Since then, several researchers around the world have proposed to study this further in order to find a dye with high capacity and staining of the intraocular structures that is safe for the retina. In the search for the ideal dye, the present invention proposes the use of natural dyes, including the use of a pigment that is a constitutive structure of the retina, as a new alternative dye for use in chromovitrectomy or other surgeries or procedures where it is necessary or helpful to define layers or boundaries to guide a health care provider during a procedure or process.
The document PI0311609-3 reveals compositions containing lutein and zeaxanthin and the use of such compositions as a source of nutrition for infants, whose purpose, as well as the composition, dosage, formulation, mode of administration, use context and production process are completely distinct to those revealed in the present invention.
The document JP2008138158 refers to a yellow pigment extracted from cocoons cricula, and a yellow dye, an artificial color, a UV-filtering agent and an antioxidant.
The document EP1075284B1 refers to the use of vital dyes to facilitate surgical procedures in vitreoretinal surgery.
The present invention is distinguished by the fact that (i) the vital dyes used in this invention are natural dyes, alone or in combination with other dyes, while the dyes mentioned in the document above are all synthetic, (ii) the application of this invention relates not only to the field of chromovitrectomy but to other medical fields of surgery or treatment, including eye, brain, abdomen, joint, plastic, gynecologic and oncology, and (iii) the membranes to be identified are not just intraocular but also intracerebral, intra-abdominal, intrapelvic and intra-articular, among others.
The present invention also provides one or more natural compositions that can be used to protect tissues and cells exposed during surgical procedures from damage due to light present in the surgical field. The compositions include lutein and zeaxanthin which absorb light and provide a protective effect, particularly against the most damaging wavelengths of light.
The present invention also provides one or more natural compositions that can be used to protect intraocular tissues and cells by topical application to the eye or injection into the eye. The compositions include lutein and zeaxanthin which are known to provide a protective effect r to intraocular tissues, particularly against macular degeneration.
The present invention relates to the use of one or more natural dyes, alone or in combination with other dyes, to stain membranes and biological structures, in general, and the use of such compounds for the preparation of compositions to stain membranes and biological structures with the purpose of facilitating the identification of these during surgical or medical procedures.
The present invention further relates to compositions comprising one or more natural dyes, alone or in combination with other dyes, in combination with pharmaceutically acceptable vehicles and structures, to identify biological membranes during surgical or medical procedures.
The present invention also relates to processes for producing compositions comprising natural dyes, alone or in combination with other dyes, used in surgical or medical procedures.
In another embodiment, the invention relates to a process of identification of membrane and biological structures with the dyes defined herein.
An object of the present invention is the protection of tissues and cells exposed during surgical procedures from damage due to light present in the surgical field by the administration of one or more dyes that incorporate lutein and zeaxanthin, which absorb light.
Another object of the present invention is to protect intraocular tissues and cells by topical application to the eye (externally or internally) or injection into the eye (externally or internally) of one or more dyes that include natural substances such as lutein and zeaxanthin.
The present invention relates to compositions comprising one or more natural dyes, alone or in combination with other dyes, in combination with pharmaceutically acceptable vehicles, for the identification of membrane and biological structures during surgical or medical procedures.
In a method according to the present invention, the biological membrane or structure is selectively stained such that biological tissue adjacent the selected biological membranes or structures are not stained to a substantial extent, or at least to a significantly lesser, non-detrimental extent than the selected biological membranes or structures selected to be stained. Accordingly, during the surgical procedure, the selected biological membrane or structure is clearly distinguishable from adjacent tissues and so facilitates the surgical procedure and reduces the risk of damage to adjacent tissues.
Using dyes of the present invention, little or no detrimental effect on adjacent tissues has been observed. Further, any remaining dye in the surgical field is removed shortly after the procedure, thereby reducing the possibility of adverse side effects of the dye.
Dyes of the present invention create a satisfactory level of staining at a concentration which is physiologically and toxicologically acceptable. It is preferred that a minimum amount of dye be used that will still provide a visible differentiation between the selected biological membranes or structures and the adjacent tissue.
The dyes of the present invention are selected from the group comprising ingredients, portions or extracts of lutein, zeaxanthin, urucum, lycopene, astaxanthin, beta-carotene, and beta-cryptoxanthin, alone or in combination with each other. Such dyes may also be used in combination with dyes selected from the group comprising ingredients, portions or extracts of brilliant blue, indocyanine green, infracyanine green, trypan blue, patent blue, bromophenol blue, fast green, indigo carmine, evans blue, light green, triamcinolone, crystal violet, fluorescein, fluormetolone acetate and congo red. In a more particular embodiment, the compositions comprise lutein and zeaxanthin alone or combined with trypan or brilliant blue.
The pharmaceutically acceptable vehicles can be selected from the group comprising phosphate buffer, balanced salt solution (BSS), polyvinyl alcohol, benzyl alcohol, purified water, sodium phosphate, sodium chloride, calcium chloride, magnesium chloride, potassium chloride, sodium citrate, sodium acetate, boric acid, borax, methylcellulose and derivatives, hyaluronic acid, dextran sodium polysorbate, tweens, chondroitin sulfate, sodium edetate, propylene glycol, polyethylene glycol, phenylphosphate, sodium phthalate, potassium phosphate, citric acid, carbomer 934, carbopol, metaphosphoric acid, glycocholic acid and acetic acid.
The compositions of the present invention may comprise from about 0.001% to about 20%, preferably about 0.01% to about 5%, and including all ratios in between these recited limits, of the dye.
The intraocular membranes referred to in this invention are preferably selected from the group comprising the anterior and posterior capsule, corneal epithelium and endothelium, epiretinal membrane, internal limiting membrane, vitreous, posterior hyaloid and other ocular membranes.
Biological membranes in this invention are referred to any and all membranes that need to be identified in surgery or medical care in general, particularly in ophthalmic, brain, joint, abdominal, plastic, gynecological and oncologic surgery.
The compositions of the invention can be used for identification of membranes or structures in general surgical or medical procedures. Common surgical procedures where it is necessary to identify structures and membranes include ophthalmic, brain, arthro-orthopedic, abdominal, plastic, joint, gynecologic and oncologic surgeries. The invention is especially applicable in the identification of intraocular membranes and biological structures in ophthalmic surgeries including chromovitrectomy. Preferably, the dyes used in this invention are lutein and zeaxanthin and their combinations.
Lutein and zeaxanthin, besides being carotenoids, and more particularly xanthophylls, are known and studied for their association with the prevention of age-related maculopathy. The present invention relates to the use of lutein and/or zeaxanthin as safe and effective dyes or stains for surgical procedures, such as, among others, chromovitrectomy, allowing an easy identification of membrane and biological structures such as epiretinal membrane, ILM, anterior and posterior capsule, corneal epithelium and endothelium, vitreous and posterior hyaloid, and their complete removal, when necessary, by the ophthalmic surgeon.
In view of the iatrogenic retinal complications caused by the procedures in removing these micro-structures shown in prior art, the use of natural colorants, alone or in combination with other dyes, to stain intraocular membranes and other structures, enable a breakthrough both in the surgical technique as well as in the toxicity profile, with substantial improvements in surgical outcomes.
Lutein, which has the structural formula below:
and zeaxanthin, which has the structural form below:
are lipophilic pigments belonging to the group of carotenoids and traditionally found in fruits and vegetables. These two carotenoids are structural isomers and have a hydroxyl group in the terminal portion of the molecule, which partly explains their different polarity and tropism for certain biological structures, such as the macula. Lutein and zeaxanthin are associated with the possible prevention of age-related maculopathies due both to their antioxidant properties, which can prevent progress of macular degeneration; and to their recognized distribution in the macula. This selective and specific distribution of these carotenoids suggests that they play an important role in this region, both as a “filter” of blue light, which typically induces the formation of radical oxygen species, as well as their activity as antioxidants. The role of lutein and zeaxanthin in the eye is a good example of how the human body can defend itself against an oxidative process. Interestingly, lutein and zeaxanthin have a dual and synergistic mechanism of action in the macula. Lutein and zeaxanthin are present in the central yellow region (the fovea) having a maximum absorption at 446 nm, which is coincidentally the same wavelength as blue light in the electromagnetic spectrum, thus, absorbing the excess photon energy. Exactly because of this absorption, lutein and zeaxanthin have chromophore groups responsible for the their characteristic yellow-orange color.
In Europe, lutein is classified as a food dye, registered under number E161b in EFSA (European Food Safety Authority). The fact that it is (i) a GRAS molecule (Generally Recognized as Safe, the highest distinction awarded to a food/additive/dye), (ii) recognized by the FDA (Food & Drug Administration in the United States of America) as such, (iii) widely studied and the object of several scientific papers published in peer-reviewed journals, (iv) associated with a possible beneficial effect in preventing today's major retinal diseases and (v) a dye, makes it an interesting substance as an object of study and identification of intraocular membranes and other biological structures, not limited to, for example, intraocular membranes.
In Europe, zeaxanthin is also registered as a food dye by EFSA and has been assigned E number E161h. Zeaxanthin is a GRAS molecule and has been the subject of scientific papers published in peer reviewed journals. As dye, zeaxanthin makes an interesting substance as an object of study and identification of intraocular membranes biological structures, not limited to, for example, intraocular membranes.
The combined use of lutein and/or zeaxanthin, alone or in combination with other substances such as dyes and other pharmaceutically acceptable vehicles, as a dye composition of the anterior and posterior capsule, corneal epithelium and endothelium, epiretinal membrane, internal limiting membrane, the vitreous and posterior hyaloid, is illustrated along with data pertaining to its actions through examples described below.
Despite the fact that certain definitions about lutein and zeaxanthin dyes and their combinations in the field of ophthalmic surgery are described in more detail here, the invention may also be achieved with other dyes and application fields previously defined.
Table 1 below lists dyes that can be used in the invention and their particular quantitative ranges.
There are many benefits associated with the use of natural dyes, including: (i) easy identification of membrane and biological structures to identify, remove, or work with; (ii) prevention of side effects caused by incomplete removal of membranes and biological structures; (iii) reducing the time of surgery with reduction in medical and hospital fees; (iv) increased safety because the proposed dye is a natural dye, alone or in combination with other dyes, not synthetic, and all the alternatives on the market today have demonstrated toxicity; and (v) possible antioxidant effect associated with the use of dye in the surgery or other medical procedures.
A general process of the preparation of compositions of the present invention is as follows. The packaging material is received. Subsequently, the raw materials needed for manufacturing are properly weighed. The handling and/or filtration is done in ISO 8 class room. Before septic or aseptic filling, in-process quality control is performed. If the filling is aseptic, it follows the following flow: Filling in the ISO 5 class room, Sealing in ISO 7 class room and Sterilization in the final sterilization room. Conversely, if the filling is septic, it follows the following flow: Sterilizing Filtration in ISO 5 class room, Filling in ISO 5 class room and Sealing in ISO 7 class room. After these steps, packaging and quality control of the finished product takes place.
The manufacturing process of compositions comprising one or more dyes or stains, such as lutein, zeaxanthin, urucum, lycopene, astaxanthin, beta-carotene, beta-cryptoxanthin, alone or in combination with each other, and such dyes and dye compositions alone or in combination with brilliant blue, indocyanine green, infracyanine green, trypan blue, patent blue, bromophenol blue, fast green, indigo carmine, Evans blue, light green, triamcinolone, crystal violet, fluorescein, fluormetolone acetate and congo red. Those skilled in the art will be able to utilize mixtures of these dyes as long as the mixture accomplishes the purposes of staining selected biological tissues to readily distinguish them from adjacent biological tissues, preferably at low amounts and with no, or very little, toxicity, and with no, or very little, dye remaining after the procedure. In general, the concentration of the dye or mixture of dyes is minimized while still effectively staining the selected biological tissue while at the same time minimizing the risk of possible damage or toxicity to the biological tissue. The viscosity of the dye solution may be adjusted, for example by the addition of hyaluronic acid, to achieve improved adherence to the selected biological tissue. In addition, the solution may be formulated as a dispersion. It is well within the skill in the art to select and formulate a suitable form of the solution for particular applications.
Forty human eyes were tested using solutions of other substances including lutein/zeaxanthin(L/Z) (Lutein 5% CWS/S-TG from DSM Nutritional Products, Inc., Parsippany, N.J.), brilliant blue (OPHT-Blue from Ophthalmos Industry, Sao Paolo) and/or other vehicles at concentrations of lutein from 0.01% to 20% and brilliant blue from 0.0125% to 0.025%. The staining solutions were prepared as described in Example 2. The anterior capsule, vitreous, posterior hyaloid and corneal endothelium were stained through immediate deposition of the dye solution in the membrane.
The following scoring technique was used for the cornea:
1Draize. J. H., et al., J. Pharm. Exp. Ther., 82: 377-390, 1944.
For the ILM the scoring used was: 0/4+ (none), 1+/4+ (weak), 2+/4+ (regular), 3+/4+(good), 4+/4+ (intense).
Staining of the anterior capsule was observed of 3+/4+ and 4+/4+, respectively with a solution of L/Z 0.25% and brilliant blue 0.025% and a solution of L/Z 0.5% and brilliant blue 0.025%. This staining degree received a score of 1+/4+ with a solution of L/Z at 1%. It was also observed the staining of the vitreous at 4+/4+ with a solution of L/Z at 20% as well as staining the ILM at 4+/4+ with a solution of L/Z at 0.3% and 0.025 brilliant blue. The solution of L/Z at 1% alone also stained the ILM at 2+/4+. It was observed a staining of corneal endothelium at 2+/4+ with a solution of L/Z at 20%.
These experiments establish that lutein and zeaxanthin in combination with vehicles and/or pharmaceutically acceptable dyes, can be used for the preparation of a composition to facilitate the identification of membranes and biological structures during surgical procedures, not limited to, for example, ophthalmic surgical procedures.
The quantities of dyes in general, and more specifically, lutein and zeaxanthin, as well as vehicles and/or pharmaceutically acceptable dyes are listed in Table 1.
While either lutein or zeaxanthin may be used alone or in combination with other dyes, the preferred proportion of lutein to zeaxanthin in the composition ranges from 5:1 to 1:5 and all values in between.
The preparation technique described below is valid for L/Z, whatever its chemical form, purity, crystallization or degree of esterification and for all the vehicles mentioned above.
L/Z does not exhibit good water solubility, therefore, polyvinyl alcohol was used as a vehicle at a concentration of 1.4% dissolved in phosphate buffer at pH 7.0. This alcohol can be dissolved in another buffer or a simple or balanced saline solution.
L/Z 0.5 g
Brilliant blue: 0.025 g
Monobasic sodium phosphate: 0.004 g
Dibasic sodium phosphate. 0.028 g
Sodium chloride. 0.85 g
Povidone 0.4 g
Polyvinyl Alcohol 1.4 g
Water q.s.p. 100 mL
Weigh the active component: Brilliant Blue and L/Z and, under stirring, dissolve it in buffer solution (pH: 7.0 to 7.4) containing 1.4% polyvinyl alcohol.
Check the pH.
Proceed with filling in clean area ISO Class 5 (Class 100) into a vial with a rubber stopper and a Flip-Off aluminum seal containing 0.5 mL. (Single dose).
Sterilize by autoclaving for 30 min at 121° C.
The process starts by dissolving the components in a balanced salt solution, or any other solution that has compatibility with the components of the formula and to provide stability, pH and osmolality compatible with ocular use, including various forms and dosages of the active components and their vehicles. Some examples of formulas are included in Table 2.
Other embodiments prepared include: (1) 20% L/Z dispersible/soluble in water regardless of physical form and polyvinyl acid 1.4% qs 100%; (2) 0.5% L/Z dispersible/soluble in water regardless of physical form, 0.025% brilliant blue, and polyvinyl acid 1.4% qs 100%; and (3) 0.5% L/Z dispersible/soluble in water regardless of physical form, 0.0125% brilliant blue, and polyvinyl acid 1.4% qs 100%.
The main manipulation techniques used include: (i) dissolution; (2) agitation; (3) filtration; and (4) sterilization.
The sterilization step, when necessary, is either performed through wet heat, by autoclaving with temperatures ranging from 80° to 140° C., by sterilizing filtration, by radiation or by other compatible method.
The pH is observed in a range from 3 to 12 and osmolarity and osmolality ranges from 100 to 2000 mOsm, with preferred formulations having osmolality around 300mOsm.
Besides the use of one dye alone in a composition, as previously mentioned, it is also possible to prepare a composition comprising of a combination of more than one dye. In this invention, not only are vehicle and active concentrations supplied and identified that differ from prior art, but also the specific use and site of deposition, which is made directly into the eye membranes or other biological structures. This was not provided by prior art where lutein and zeaxanthin were administered orally (capsules, tablets, cereal bars, or fortified milks). The present invention provides a composition in the form of an injectable dye formulated from the raw material including lutein and/or zeaxanthin. The prior art did not teach compositions that could be administered during surgical procedures in an injectable administration form. Specific applications include an injection solution or dispersion, an ocular implant for protection against macular degeneration or the progression of macular degeneration, and a slow-release form of LIZ placed in the eye.
Lutein and/or Zeaxanthin
The dissolution is done with the vehicles identified in Table 1 above. The solution of L/Z is weighed and diluted with distilled water in various concentrations ranging between 0.01% and 20%. The osmolality of the solutions is calculated by the ATM Osmomette osmometer (Precision Systems, Inc., Sudbury, Mass.) or other applicable osmometers. A balanced salt solution (BSS) is used as the control using an osmolarity or osmolality from 100 to 2000 mOsm.
The main steps are listed below:
1. To determine a vehicle from Table 1 so that the final solution is water soluble, solubility tests in water and in various vehicles including those shown in Table 1 were performed. Solubilities ranging between 0.02 and 110 mg/m were found.
2. To characterize the absorbance of the L/Z solution, UV spectrophotometry was used. Absorbency between 2-5 within a wavelength range of 250 nm to 1000 nm at a speed of 600 nm/min and using 1.4% polyvinyl alcohol as a white standard were observed.
3. To identify the resulting color of the chromophore groups, mixtures comprising different colors within the visible spectrum were analyzed.
4. To test the physicochemical parameters of optimum pH, osmolarity/osmolality, and concentration, the procedures described above were followed.
One hundred and twenty human cadaver eyes from human corneal donors were tested using solutions lutein and zeaxanthin alone or combined with brilliant and trypan blue. Initially, the anterior part of the eye or the cornea was removed through limbal incision 360 degrees as routine, and kept for a cornea transplant. The rest of the eyeball was usually discarded, with the only exception of the scleral tissue that can eventually be used as an implant to correct human scleral thinning or in enucleation surgery. Before the elimination of most ocular tissues and sclera preparation, experiments were performed in coloring different eye membranes and intraocular structures.
Soon after the removal of the cornea, 0.1-0.3 mL of the dye (L/Z 0.25-20% alone or combined with brilliant blue (0.0125%-0.025%) or Trypan Blue (0.01%-0.15%) were applied to the anterior capsule of the lens. After 30 seconds the dye was removed with a light irrigation of 10 mL of BSS. Then the capsule of the lens was removed with Utrata capsulorhexis forceps by applying circular motion with 360 deg. After removal of excess dye, the staining intensity was measured by grade 0 (no staining), + (slight staining), ++ (moderate staining), +++/++++ (intense staining), by three experienced surgeons who did not know the substances and who were operating independently. The anterior capsules removed were evaluated by spectrophotometry.
The lens was removed for the experiments by using a surgical forceps for vitreous excision in block. The entire vitreous was immersed in 1 mL of each dye solution for 1 minute, followed by the immersion of the same vitreous in 1 mL of BSS.
In the last experiment, the binding capacity of the dye in the ILM was evaluated after intravítreal injection of the ILM. A total of 0.1-0.3 mL of each dye solution was injected into the vitreous cavity on the ILM. The excess dye was removed by an infusion of 0.1 mL of BSS. After removal of excess dye, the intensity of staining in the ILM and vitreous were evaluated grade 0 (no staining), + (slight staining), ++ (moderate staining), +++/++++ (intense staining) by three vitreoretinal surgeons experts who do not know the substances used and who were operating independently. Then a bent 27-gauge needle was used to create a flap on the ILM, and a 20-gauge vitrectomy surgery pinch is used to hold and gently remove the ILM. The ILMs removed were evaluated by means of spectrophotometry.
ILM and anterior capsule of the lens were removed and fixed in a solution of formalin at 10% for 24 hours. This was followed by soaking the tissue in Araldite® (Huntsman International, LLC) for histological sections. The material was collected from two different areas at sites of the previous injections of each dye solution. All samples were collected in areas separated by a minimum of 500 μm from each other. The samples were analyzed by light microscopy and electron microscopy. For light microscopy, the thin tissue sections were examined after staining with toluidine blue dye. For electron microscopy ultrathin sections were placed on copper micro-supports or grids, stained with uranyl acetate and silver citrate, and examined with electron microscope Jeol JX 1500™ (Jeol Ltd., Tokyo, Japan).
Thirty Dutch-belted rabbits weighing 1.5 to 2 kg were used according to the research standards of the Helsinki Declaration, and the Rules of the Association for Research in Vision and Ophthalmology (ARVO) and the Standards of Ethics in Research of the University of Sao Paulo regarding experiments on animals. All surgical procedures and tests were done under anesthesia after intramuscular injection of 35 mg/kg ketamine hydrochloride (Phoenix Scientific Inc., USA) and 5 mg/kg of ketamine hydrochloride (Phoenix Scientific Inc., USA). The pupil was dilated before surgery through the instillation of cyclopentolate hydrochloride 1% (Bausch & Lomb Pharmaceuticals Inc., USA) and phenylephrine 5% (Bausch & Lomb Pharmaceuticals Inc., USA).
Intravitreal Injection and Surgical Technique.
Two surgical techniques were used to make the subretinal or intravítreal injection application of the dye. In a first technique, the subretinal toxicity of the dye was evaluated. Anesthesia was performed by intramuscular injection of 35 mg/kg of xylazine hydrochloride and 5 mg/kg of ketamine hydrochloride, followed by placement of a blepharostat in the right eye of the animals and a drop of topical povidone-iodine 5% for preparation of the eye for vitrectomy with 3 sclerotomies. An infusion was positioned at the temporal sclera to maintain the intraocular pressure at 30 mmHg and fixed by Vycril 7-0 sutures (Ethicon, Inc.). Then two nasal and superior temporal sclerotomies 2.5 mm posterior to the limbus were performed. Pars plana vitrectomy was performed using a 20-gauge system with the vitrectiomia Accurus™—(Alcon, Fort Worth, Tex., USA) instrument.
The next surgical step was the application of two marks of diode laser photocoagulation FTC/TTT/IPDT 2000™ (Electronica Opto, São Carlos, SP, Brazil) with the parameters of 100 μm in diameter, 100 milliwatts and duration of 300 milliseconds, in the temporal and nasal retina 4 mm below the optic nerve. The function of the laser marks is to delimit the region that the dye is injected into the subretinal for histological analysis. The administration of the dye was made with a polyamide 41-gauge infusion cannula for macular translocation (Bausch & Lomb, USA). The cannula was positioned 2 mm above the prior laser photocoagulation mark. The dye to be used was injected into the subretinal space at different concentrations, and at 2 mm below the mark of temporal photocoagulation. The dye was infused continuously until a bubble of 3 mm in diameter is formed by an infusion of 0.02 mL of the dye. Next, 0.02 mL of BSS control solution was infused with the same shape than the nasal laser mark. The eye was sutured with 7-0 Vicryl thread in the three sclerotomies. This experiment was repeated in two animals with each dye at different concentrations. The rabbits were sacrificed with intravenous injection of 2 mL of phenobarbital and the eyes were removed by laser enucleation 24 hours after surgery.
In a second experiment, the toxicity of intravítreal dye was evaluated. A total of 0.1 mL of dye was injected into the vitreous cavity of eyes and repeated in two additional animals. In the contralateral eye of an animal was injected 0.1 mL of BSS (290 mOsm) as control. The technique of intravítreal injection follows international patterns22. Briefly, a blepharostat was placed followed by instillation of a drop of 5% povidone-iodine on the eye. Under the surgical microscope, a 27-gauge needle was connected to a 1 mL syringe containing the dye or BSS and was injected in the superotemporal sclera region, 2 mm posterior to the limbus. The eyes were examined to exclude retinal detachment, vitreous hemorrhage, or injury to the lens. At the end of the procedure, a drop of sterile eye drops with antibiotics and steroids were applied. The rabbits were sacrificed with intravenous injection of 2 mL of phenobarbital and the eyes were removed by laser enucleation 24 hours after the injection and fixed in glutamaldehyde at 2.5%.
Fundoscopy and Fluorescein Angiography.
Fluorescein angiography was performed by intravenous injection for 30 seconds of 0.3 mL of sodium fluorescein 10% in the auricular vein of the animal magna. Angiography was performed using a specific camera eye fundus (Topcon TRC, Topcon, Tokyo, Japan) every 20 seconds up until 5 minutes after initial injection. An examination of fluorescein angiography was performed 6 hours and 24 hours after intravítreal application of dye. The dye injection was performed slowly to avoid iatrogenically breaking the hematorretinian barrier by rapid bolus injection that can happen in these animals.
Histology.
The eyes were enucleated and fixed in a solution of 2% paraformaldehyde, 2% glutaraldehyde and phosphate buffer 0.1 mol/L and pH 7.4 for 24 hours. This was followed by soaking the tissue in Araldite® for histological sections. The material was collected from two different areas at sites of previous injections of the dye. All samples were collected in areas separated 500 μm from each other. The samples were analyzed by optical microscopy and electron microscopy. For optical microscopy, the thin tissue sections were examined after staining with toluidine blue dye. For electron microscopy ultrathin sections were placed in copper microstructures, stained with uranyl acetate and silver citrate, and examined with electron microscope Jeol JX 1500™ (Jeol Ltd., Tokyo, Japan).
The following describes the actions taken at each point of the study:
Time zero: Antisepsis and anesthesia of the animal, intravítreal injection/subretinal dye (experimental group), and intravítreal injection/subretinal balanced salt solution (control group).
Time 6 hours: Fundus fluorescein angiography and retinal examination.
Time 24 hours: Fundus fluorescein angiography and retinal examination, asepsis and anesthesia of the animal; sacrifice the animal by an overdose of pentobarbital.
After the procedure: Data collection for histology, electron microscopy and statistical analysis of results.
Time 7 days: Fundus fluorescein angiography and retinal examination, asepsis and anesthesia of the animal, and sacrifice the animal by an overdose of pentobarbital.
The present compositions are useful as dyes for histopathological staining, both in vitro and on the external surface of the eye. Dye compositions used were a dispersion of lutein and zeaxanthin (L/Z) 0.1-0.7% associated with brilliant blue 0.0125%-0.05% in a aqueous buffer solution at pH range [6-7.4] and osmolality range of [280-320] Osm/Kg. 2 ml of these solutions were packaged in 3 ml-vials. Tissues used for staining were conjunctiva, cornea, lids and retinal epithelial tissue. The staining was done by the following process: the whole eye globe was obtained and immersed in a Karnovski fixative composed with glutaraldehyde 2.5% and paraformaldehyde 2% in sodium cacodylate 0.1M buffer keeping the solution at pH 7.2.
The solution was maintained for 24 hours and retinal tissue, conjunctiva and cornea tissues were cut. Then, the first rinse process was conducted three times by using a sodium cacodylate 0.1M buffer during 15 minutes. The second rinse process was then conducted leaving the tissue in solution overnight with the same buffer. The second fixative process is conducted with osmium tetroxide 2% in sodium cacodylate 0.1 M buffer for 2 h, followed by a 10 minute rinse with same buffer. After that, the material went through the dehydration/drying process, starting with ethanol 70% (15 min, twice), 90% (15 min, twice) and 100% (15 min, 4 times) and finishing with propylene oxide (30 min, 3 times). The material was then submitted to infiltration with Epon® resin (Miller-Stephenson) in a 1:1 solution of Epon®:propylene oxyde overnight, with lid open. The day after, the material was re-infiltered with Epon® for 4 h in vacuum conditions. After this, the material was included in a mold and taken to the polymerization process at 60° C. for 48 h. After trimming, semi-thin cuts were made with 40 micrometer thickness in a Leyca Reichert Ultracut #702501 microtome and finally stained with the dye solutions mentioned above. There was an adequate staining of the material cut providing a greenish blue staining to all materials.
Surgical procedures normally involve an exposure of tissues and cells to the surgical room ambient, which typically has oxygen and light. Specifically, most surgical rooms possess powerful illuminators (endoilluminators) whose only function is to provide the best illumination possible for the surgeon to visualize the target areas and be able to perform with no problem all surgical steps. The endoilluminator is described in scientific literature as a powerful source of blue light which can provide phototoxic effect in the retina.32 Blue light is described in scientific literature as an inherent source of free radicals.33 Free radicals are extensively described in the literature as attackers of the integrity of photoreceptor lipophilic membrane, causing premature cell death, and leading to age-related macular degeneration, the leading cause of blindness in the western world. Free radicals also provide for the accumulation of drusen in the lens leading to premature onset of cataracts.34 Lutein and Zeaxanthin (L/Z) can stabilize, quench or scavenge free radicals avoiding further damages to phtotoreceptor or lens integrity and therefore contributing to decrease the severity or even incidence of these conditions. On the other hand L/Z have the property to absorb blue wavelengths of light in the area of the 446 nm therefore diminishing the exposure of lens or retinal photoreceptors to the hazardous light (3-23). The next paragraph portrays a description of L/Z mechanism of action. The endoilluminator is a source of intense light exposure, mainly blue light. The surgical room is full of oxygen, the perfect fuel for free radical formation. The intraocular use of L/Z solutions will provide an extra protection to the surgery given by its filter and antioxidant mechanism of action. Costa et al conclude that “Light-induced retinal toxicity by the endoilluminator is dependent on factors such as the duration of use, type, power, and wavelength of light source. The hazard of light radiation increases with decreasing wavelength because stronger phototoxic effects are mediated by ultraviolet rays and blue light, as shown in experimental studies.” Moreover, since oxidation is a systemic problem that can happen anywhere in human body tissues and since exposure to the endoilluminator is present in all surgeries, not only in ophthalmic surgeries, the presence of L/Z as a surgical aid can diminish the contact and attack of blue light photons and free radicals to the tissues, accelerating its degenerations (and consequent degenerative diseases), in virtually all parts of the body.
Lutein and zeaxanthin are lipophilic pigments belonging to the group of carotenoids and traditionally found in fruits and vegetables. These two carotenoids are structural isomers and have a hydroxyl group in the terminal portion of the molecule, which partly explains their different polarity and tropism for certain biological structures, such as the macula. There is a significant array of published peer-reviewed prior studies showing that L/Z are associated with the possible prevention of age-related maculopathies due (i) to its antioxidant mechanism, which can prevent progress of macular degeneration and (ii) to its exclusive distribution in the macula. The selective and specific distribution of these carotenoids suggests that they play an important role in this region, both as a “filter” of blue light and as an antioxidant. Blue light is well-known to be one of the major generators of hydroxyl radical, a reactive oxygen specimen that will attack biological structures such as photoreceptors. Reactive Oxygen Species (ROS) are continuously generated in the retina by the existence of several metabolic reactions, considerable oxygen levels, polyunsaturated fatty acids, and photons of blue light. The continuous exposure to these photons in the retina will lead to the formation of ROS which, in its quest for stabilization, will capture an electron of any photosensitizer such as a photoreceptor, attacking this structure. With an extensive polyenic chain, L/Z, if present in the lens and retinal region, can donate the electron needed to the ROS formed as a result of the blue light presence, quenching the triplet stage of both photosensitizers as well as singlet oxygen, inhibiting further formation of ROS and preventing lipo-peroxydation. Interestingly, L/Z molecules absorb light in the region of the visible spectrum, around 446 nm, which coincides exactly with the blue region of the electromagnetic spectrum. For this reason, it is known that L/Z may be natural absorbers of blue light, diminishing its negative prevalence in the lens and retina. The use of oral supplements of L/Z with the objective of preventing age-related maculopathies has been registered for several years.
Referring to
Based on the experiments, a combination in the ratio L/Z 0.3%+BB0.025% (close to 10:1) has a good green color and possess high dying activity and low toxicity. L/Z 0.3%+TB 0.1% (3:1) also has an interesting green color and intense dying activity but some toxicity. In order to decrease the amount of TB to 0.05%, we must accept a little dark green color solution (L/Z 0.5%+TB 0.05%) or accept a little low dying activity (L/Z 0.15%+TB0.05%). A 10:1 L/Z-BB ratio is optimal for color/toxicity. A 3:1 L/Z-TB ratio is optimal for color but not for toxicity. The 10:1 ratio seems the best balance between color/solubilization/toxicity with either solution. Also, concentrations of BB below 0.025% and of TB below 0.05% seem to have staining efficacy that was impaired in cadaveric eyes. Additionally, concentrations of L/Z above 0.5% can result in precipitation from the solution and pose a challenge to dissolution. Furthermore, it appears that the L/Z limiting concentration is 0.5% in each combination either with BB or TB using different concentrations of buffer, stirring time and temperature.
The foregoing description and drawings comprise illustrative embodiments of the present inventions. The foregoing embodiments and the methods described herein may vary based on the ability, experience, and preference of those skilled in the art. Merely listing the steps of the method in a certain order does not constitute any limitation on the order of the steps of the method. The foregoing description and drawings merely explain and illustrate the invention, and the invention is not limited thereto, except insofar as the claims are so limited. Those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.
This application claims priority to U.S. Patent Application Ser. No. 61/468,838, filed Mar. 29, 2011, which is incorporated herein in its entirety by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 61468838 | Mar 2011 | US |
