PH-controlled protein removing cleaner

Abstract: A pH controlled protein removal system and a method of using it in the substantial absence of a protein digesting enzyme and, preferably, in the substantial absence of a surfactant is disclosed. The system is a pH-controlled protein-cleaning composition for e.g. contact lenses comprising (a) water; (b) a tonicity builder sufficient to render said composition ophthalmically acceptable; and (c) a pH regulator sufficient to provide and maintain the pH of the composition at a pH of about 7.5 to about 11.5; in the substantial absence of a protein-digesting enzyme. The inventive method is for removing proteinaceous deposits from a polymeric substrate, e.g. a contact lens, in the substantial absence of a proteinaceous deposit digesting enzyme, comprising contacting said polymeric substrate having a proteinaceous deposit thereon with an aqueous solution at a pH of about 7.5 to about 11.5 to free at least a significant portion of said proteinaceous deposit from said substrate and removing said proteinaceous deposit reduced substrate from said solution.

Description: The invention relates to the field of cleaning compositions, more specifically to the use of cleaning compositions for the removal of protein from contact lenses. Cleaning compositions of various types have been known for many years, comprising many different components. Such compositions are used to solubilize, abrade, oxidize, or reduce surfaces in an effort to remove undesirable surface adherents and restore a desired surface. Each type of surface to be cleaned presents its own characteristics which must be taken into account when choosing an appropriate cleaning composition therefor. Polymeric substrates offer particularly problematic issues in choice of cleanser composition due to the relatively large amounts of proteins which adhere thereto. Especially thorny cleaning problems arise when the substrate to be cleaned is a contact lens. In addition to the parameters to be considered for the polymeric material of the contact lens per se, one must also take into account that the optical surfaces cannot be scarred, residue must be quickly and easily rinsed away with very small volumes of fluid, tonicity must be in an appropriate range so as not to destabilize the material, and the cleaning system has to be non-toxic and non-allergenic (at least to the extent residue remains or is likely to remain). Specifically with reference to contact lens cleaning, protein adhesion and build up on the lens, sequestered primarily from tear fluid, has been a persistant and nagging problem. To deal with this difficulty, three general approaches have been attempted. The earliest attempt was to include an abrasive component, so that upon rubbing the lens therewith, the adhering protein would be broken up and town away from the lens. Compositions of this type include slurries of organic compounds such as sucrose or dextrose, of inorganic compounds such as silica, sodium chloride, aluminium oxide or sodium carbonate, of polymeric materials such as nylon beads or silicon polymer beads, or of other particulate matter such as glass beads. A typical representative of this first type is US-A-4,127,423. A second type of attempted solution involved adding a surfactant. The surfactant is added to substantially solubilize the adherent protein. Compositions of this type include siloxane surfactants, alkylglycosides or polyalkyleneoxy modified silicone. Attempts were also made in the combination of the two types above. Such compositions include Opticlean™ and Restore™. A third type of attempt to deal with the adherent protein has been to utilize an enzyme to digest the protein. A fourth type of attempt to deal with the adherent protein is the use of hydrogen peroxide or a precursor thereof in aqueous solutions as disclosed e.g. in EP-A-124 461, WO-A-86/05695 or EP-A-139 994. The hydrogen peroxide in such systems is always reduced to water in a second step. EP-A-349 487 describes an antimicrobial ophthalmic solution containing Bradosol® and methods of using the same. Ophthalmic solutions containing hydroxyethyl cellulose are described in GB-A-2 169 508, which solutions may serve as artificial tears. EP-A-76 136 describes aqueous disinfecting solutions for contact lenses, which solutions contain certain quaternary ammonium salts, e.g. Onamer M®. US-A-4 490 389 describes a method for sterilizing contact lenses in an aqueous solution, wherein said solution has a pH between about 6 and 9 and comprises an ene-diol compound and copper ions. Of course the protein method can be used alone or in combination with any of the aforementioned methods of dealing with protein deposits. Typical available enzymatic cleaners for contact lenses include papain, subtilisin, pancreatin and other proteases. While each of these methods has been somewhat successful in protein removal, each presents its share of drawbacks. For example, many abrasives are too harsh for use with contact lenses. Surfactants, in efficacious amounts for their surfactant properties, can irritate the eye terribly. Enzymes which degrade protein must never be placed into the eye for obvious reasons. Furthermore, the smaller protein fragments which result may be taken up further by the lens material or penetrate deeper into the lens matrix. In addition, enzymes if injected into the environment in substantial quantities create a considerable environmental hazard. One object of the present invention is related to the use of a cleaner composition for removal of protein from a contact lens which avoids the problems of the art as noted above. Another object of the invention is related to the use of a simple, yet effective cleaning regimen for contact lenses. Still another object of the invention is related to the use of a means for creating a cleaning solution in accordance with the preceeding objectives in situ by the user thereof. Yet another object is related to the use of an environmentally responsible formulation for removing protein from contact lenses. Surprisingly, these and other objectives of the invention are achieved by a pH controlled cleaning composition consisting of water, a tonicity builder and a pH regulator, in the substantial absence of a protein-digesting enzyme and in the substantial absence of a protein dissolving efficacious amount of a surfactant, and by a method of removing protein therewith from a contact lens having protein or proteinaceous deposits thereon consisting of contacting said contact lens with said composition for a time sufficient to loosen and remove substrate-adhered protein therefrom to result in a cleaned substrate and removing said substrate (absent the formerly adhered protein) from said composition. The invention is thus directed to the use of a solution having as its only requirements: (a) water as a carrier; (b) a tonicity builder in an amount sufficient to render said composition ophthalmically acceptable; (c) a pH regulating agent in an amount sufficient to provide and maintain an alkaline pH in the range of 7.5 to 11.5 in the presence of the other components of the composition; (d) substantially no protein digesting enzyme. Said solution is further characterized by the absence of a protein dissolving effective amount of a surfactant. The tonicity builder can be any ionic or non-ionic species which is sufficiently soluble to give the appropriate tonicity, which after the cleaning regimen is complete is ocularly acceptable, and which is compatible with the lens material. The appropriate tonicity is preferably approximate isotonicity at the conclusion of the dosage regimen Typical tonicity builders for use in the invention include suitable water soluble salts compatible with ocular tissue, preferably alkali or earth alkali metal halides, sulfates, nitrates, carbonates, borates, and phosphates, more preferably alkali metal halides, such as bromides or chlorides, e.g. sodium or potassium chloride. The tonicity builder is present in an amount sufficient to provide a tonicity in the final solution of the dosage regimen of 50 to 400 mosmole, most preferably 250 to 350 mosmole. The pH regulator maintains the pH preferably in the range of 7.5 to 11.5, more preferably 8.0 to 10.0, most preferably 8.5 to 9.5. Said pH is maintained advantageously for at least a period of time of from 10 minutes to 24 hours, preferably 30 minutes to 8 hours, more preferably 1 hour to 6 hours or until a pH altering agent is added to the solution. The pH regulating agent is typically selected from inorganic or organic bases, preferably basic acetates, phosphates, borates, nitrates, sulfates, tartrates, lactates, carbonates, bicarbonates and mixtures thereof, more preferably basic phosphates, borates, citrates, tartrates, carbonates, bicarbonates and mixtures thereof. Typically, it is present in an amount of 0.001 % to 2 %, preferably 0.01% to 1 %. The pH altering agent may or may not be a part of the initial composition and, when not part of the initial composition, may be added after a specified period of time as set forth above. The pH altering agent is preferably selected from inorganic or organic acids, more preferably acidic acetates, phosphates, borates, nitrates, sulfates, citrates, tartrates, lactates, carbonates, and bicarbonates, most preferably acidic phosphates, borates, citrates, tartrates, carbonates and mixtures thereof. The pH altering agent is present in an amount, when part of the original composition, or added in an amount, when not, which is sufficient to overcome the pH regulating agent and reset the pH to that desired. A pH typically desired is a pH corresponding to the pH of the tear fluid, e.g. 6.5 to 7.5. As stated above, the cleaner compositions do not contain any enzymes for the removal of protein. Enzyme, as used in the present context, is intended to mean a catalytic biological entity capable of degrading protein. The compositions of the present invention can be formulated in nearly any conventional manner that would be considered suitable by those of ordinary skill. More specifically, the present invention is directed to the removal of protein, especially lysozyme and other proteins typically adhering to contact lenses, such as IgM, serum IgA, secretory IgA, IgG, lactoferrin, albumin, peroxidase and tear specific prealbumin, from contact lenses, especially soft contact lenses. In the contact lens field lysozyme (found in tear fluid), its deposition on contact lenses and subsequent cleaning of lenses so fouled is a continuous and thorny problem. Most contact lenses have polymeric matrix structures which contain multiple negative sites at neutral or approximately neutral pH. Lysozyme, and a significant number of other proteins, have an isoelectric point above the usual range of pH in the cleaners used with contact lenses. Specifically, lysozyme has an isoelectric point of about 10-11. Below the isoelectric point, the protein has substantial positive charge and hence is attracted to the lens matrix. Enzymes, which cleave the protein into smaller pieces but do not account for the attractive ionic forces, only permit the fragment to permeate still further into the lens matrix, making cleaning even harder. In the instant invention, the pH of the cleaner is maintained in the range of 7.5 to 11.5, which is near the isoelectric point. Since the lysozyme will have significantly less positive charge and may have a net negative charge the attractive force of the lysozyme for the lens will diminish or even be replaced by a weak repulsive force. In this way the protein contaminant on the lens can be readily removed. In addition, the present invention offers advantages over the enzyme cleaners. First, the present invention does not fragment the adhered protein so that further migration of protein into the matrix is not increased. Additionally, as enzymes are themselves proteins, with the enzyme cleaners, there is risk of the lens having residual enzyme present even after careful rinsing. The present invention has no added enzyme and therefore is free of this problem. Still further, as enzymes continue to remain active after disposal, the present, enzyme free, formulations are much more environmentally elegant and suitable than prior enzyme containing compositions. Still more specifically, the present invention is directed to the use of compositions for cleaning protein deposits from contact lenses in the absence of enzymes and in the absence of a protein dissolving effective amount of a surfactant consisting of a 250 to 350 mosmole solution at pH of 7.5 to 11.5 by basic borate or phosphate buffer and sodium chloride. A means for creating cleaning solution according to the invention is e.g. a solid pH-controlled contact lens cleaner dosage form consisting of (a) a sufficient amount of tonicity builder to render ophthalmically acceptable an amount of water which is sufficient to cover a contact lens; and (b) a pH regulator sufficient to provide and maintain a pH of 7.5 to 11.5 in said amount of water; in the substantial absence of a protein-digesting enzyme. Said solid dosage form may be in the form of tablets, capsules, powder, granules or pellets, tablets being preferred, which can be formulated from or with conventional excipients, as known in the art. In a further embodiment, the use of a one step system is contemplated wherein e.g. an outer shell of a solid dosage form, e.g. of a tablet, consists of the ingredients for carrying out the cleaning according to the instant invention, and a delayed release core comprises a pH altering agent adjusting the pH of the cleaning solution into a tolerable range from which the lens, without rinsing or with minimal rinsing, can be placed directly on the users eye without significant irritation. In such case the solid phase pH-controlled cleaner composition, e.g. contact lens cleaner composition, consists of a delayed release component and an immediate release component, said immediate release component dissolving in an aqueous environment to form a first solution, said immediate release component consisting in the substantial absence of a protein digesting enzyme and in the substantial absence of a protein dissolving amount of a surfactant, of a pH regulator in an effective buffering amount, and a tonicity builder in a sufficient amount, such that upon complete dissolution of the immediate release component of the solid cleaner composition, the resulting solution has a tonicity of from 200 to 400 mosmol, preferably 200 to 300 mosmol, and a pH of 7.5 to 11.5; said delayed release component dissolving in said first solution from 10 minutes to 24 hours after said solid cleaner composition is introduced into said aqueous environment, said delayed release component comprising ophthalmically acceptable coating agents such as hydroxypropylmethylcellulose phthalate, sucrose, gelatin, methylcellulose, polyethylene glycol, maleic acid copolymers, methacrylic acid polymers, cellulose acetate phthalate ethylcellulose or mixtures thereof, and a pH altering agent, whereby said first solution is converted into a second solution, said second solution having a pH of 6.5 to 7.5, and having a preferred tonicity of 250 to 350 mosmol. In this embodiment, the cleaner solution is the result of e.g. a coating on a core dissolving, and after a specified time in which the lens resides in such solution, the core dissolves, whereby the cleaner solution is transformed in situ into a type of soaking solution. In such an embodiment, at minimum, the pH is returned to one from which with minimal rinsing direct administration to the eye would be suitable. The method according to the present invention consists of contacting a proteinacous deposit containing polymeric material, especially a contact lens, with a solution as hereinbefore described, wherein the pH is between 7.5 and 11.5, preferably 8.2 and 10, more preferably 8.5 to 9.5, for a period of up to 24 hours, peferably 10 minutes to 12 hours, more preferably 30 minutes to 8 hours, most preferably 1 hour to 6 hours, in the substantial absence of a proteinaceous deposit digesting enzyme, and removing the contact lens from such solution. The tonicity of said solution is preferably ophthalmically acceptable. If desired the so cleaned lens may then be rinsed or placed into a soaking solution. The instant invention will be more fully understood by reference to the following illustrative, but non-limiting Examples. Example 1: Ten Vifilcon A® lenses are soaked for 18-20 hours in a 0.12 % lysozyme solution containing 0.7 % sodium chloride, 0.58 % boric acid, and 0.05 % sodium borate decahydrate, adjusted to pH 7.2 with dilute HCl or dilute NaOH as needed. Lysozyme deposition is determined by absorbance measurement at 280 nm. The lenses are then placed in one of five buffered saline solutions (as set forth in Table I) for 2 hours, rinsed in saline, and absorbance at 280 nm is measured again and is reported in Table I (hereinafter). Example 2 (Comparative): The procedure of example 1 is followed except that enzymatic cleaners designated in Table II, having the given pH values, after tablet dissolution are used instead of the present invention solution (Table II follows Table I). Example 3 (Comparative): The procedure of example 1 is followed except that Bausch & Lomb's ReNu™ Effervescent Enzymatic Cleaner containing the enzyme subtilisin is added to the instant invention solution, in the same concentration as in example 2. This eliminates any confusion due to other materials in example 2 which are dissimilar to those in example 1. The results are shown in Table III. Absorbance Average % Decrease in Abs pH Post Deposition Post Treatment % Decrease in Abs 6 0.750 0.677 10 8 0.749 0.701 6 7 0.828 0.763 8 10 0.736 0.649 12 8 0.674 0.608 10 13 0.949 0.794 16 9 0.582 0.514 12 15 0.961 0.785 18 10 0.653 0.541 17 14 0.700 0.629 10

Claims: Use of a pH-controlled contact lens cleaner composition for removing proteinaceous deposits from a contact lens in the substantial absence of a proteinaceous deposit digesting enzyme and in the substantial absence of a protein dissolving amount of a surfactant, wherein said cleaner composition consists of (a) water, (b) a tonicity builder to render said composition ophthalmically acceptable, and (c) a pH regulator sufficient to provide and maintain a pH of 7.5 to 11.5. Use of a solid pH-controlled contact lens cleaner composition for removing proteinaceous deposits from a contact lens in the substantial absence of a proteinaceous deposit digesting enzyme and in the substantial absence of a protein dissolving amount of a surfactant, wherein said solid cleaner composition consists of (a) a sufficient amount of tonicity builder to render ophthalmically acceptable an amount of water which is sufficient to cover a contact lens; and (b) a pH regulator sufficient to provide and maintain a pH of 7.5 to 11.5 in said amount of water. Use of a solid phase pH-controlled contact lens cleaner composition for removing proteinaceous deposits from a contact lens in the substantial absence of a proteinaceous deposit digesting enzyme and in the substantial absence of a protein dissolving amount of a surfactant, wherein said cleaner composition consists of a delayed release component and an immediate release component according to claim 2, such that upon complete dissolution of the immediate release component of the solid cleaner composition, the resulting first solution has a tonicity of from 200 to 400 mosmol and a pH of 7.5 to 11.5; said delayed release component dissolving in said first solution from 10 minutes to 24 hours after said solid cleaner composition is introduced into said aqueous environment, said delayed release component comprising an ophthalmically acceptable coating agent, and a pH altering agent, whereby said first solution is converted into a second solution, said second solution having a pH of 6.5 to 7.5. The use according to claim 1 or 2, wherein the tonicity builder is sodium chloride. The use according to claim 1 or 2, wherein the pH-regulator is basic borate or phosphate. The use according to claim 1 or 2, wherein the tonicity builder is sodium chloride in an amount to bring the tonicity of the composition to 250 to 350 mosmole and the pH-regulator is basic borate or phosphate in an amount to maintain the pH of the composition at 7.5 to 11.5. The use according to claim 3, characterized in that the tonicity of the second solution is in the range of 250 to 350 mosmol. The use according to claim 3, wherein the coating agent of the delayed release component is selected from hydroxypropylmethylcellulose phthalate, sucrose, gelatin, polyvinylpyrrolidone, methylcellulose, polyethylene glycol, maleic acid copolymers, methacrylic acid polymers, cellulose acetate phthalate ethylcellulose or mixtures thereof. A method of removing proteinaceous deposits from a contact lens in the substantial absence of a proteinaceous deposit digesting enzyme and in the substantial absence of a protein dissolving amount of a surfactant, which method consists of contacting said contact lens having a proteinaceous deposit thereon with an aqueous solution according to claims 1-8 to free at least a significant portion of said proteinaceous deposit from said contact lens and removing said proteinaceous deposit reduced contact lens from said solution.

Inventors: DANDRIDGE ROSALIND, TSAO FU-PAO DR, DANDRIDGE, ROSALIND, TSAO, FU-PAO, DR.
Applicants: CIBA GEIGY AG, NOVARTIS AG
Application year: 1990
Main classification: C11D7
IPC codes: C11D11, C11D3, G02C13, A61L12, C11D7, C11D17