STABLE LIQUID ENZYME COMPOSITIONS AND METHODS OF USE

Abstract: Compositions containing an ophthalmically acceptable enzyme of high purity and integrity in a liquid medium and methods involving the use of these compositions for cleaning a contact lens, and in combination with an antimicrobial agent for the simultaneous cleaning and disinfecting of contact lens are disclosed.

Description: STABLE LIQUID ENZYME COMPOSITIONS AND METHODS OF USE The present application is a continuation-in-part of United States Patent Application Serial No. 08/477,000, filed June 7, 1995. Background of the Invention The present invention relates to the field of contact lens cleaning and disinfecting. In particular, this invention relates to liquid enzyme compositions and methods for cleaning human-worn contact lenses with those compositions. The invention also relates to methods of simultaneously cleaning and disinfecting contact lenses by combining the liquid enzyme compositions of the present invention with a chemical disinfecting agent. Various compositions and methods for cleaning contact lenses have been described in the patent and scientific literature. Some of these methods have employed compositions containing surfactants or enzymes to facilitate the cleaning of lenses. The first discussion of the use of proteolytic enzymes to clean contact lenses was in an article by Lo, et al. in the Journal of The American Optometric Association, volume 40, pages 1106-1109 (1969). Methods of removing protein deposits from contact lenses by means of proteolytic enzymes have been described in many publications since the initial article by Lo, et al., including U.S. Patent No. 3,910,296 (Karageozian, et al.). Numerous compositions and methods for disinfecting contact lenses have also been described. Those methods may be generally characterized as involving the use of heat and/or chemical agents. Representative chemical agents for this purpose include organic antimicrobials such as benzalkonium chloride and chlorhexidine, and inorganic antimicrobials such as hydrogen peroxide and peroxide-generating compounds. U.S. Patents Nos. 4,407,791 and 4,525,346 (Stark) describe the use of polymeric quaternary ammonium compounds to disinfect contact lenses and to preserve contact lens care products. U.S. Patents Nos. 4,758,595 and 4,836,986 (Ogunbiyi) describe the use of polymeric biguanides for the same purpose. Various methods for cleaning and disinfecting contact lenses at the same time have been proposed. Methods involving the combined use of proteolytic enzymes and peroxides to clean and disinfect contact lenses simultaneously, are described in U.S. Patent No. Re 32,672 (Huth, et al.). A representative method of simultaneously cleaning and disinfecting contact lenses involving the use of proteolytic enzymes and quaternary ammonium compounds is described in Japanese Patent Publication 57-24526 (Boghosian, et al.). The combined use of a biguanide (i.e., chlorhexidine) and liquid enzyme compositions to simultaneously clean and disinfect contact lenses is described in Canadian Patent No. 1,150,907 (Ludwig, et al.). Methods involving the combined use of dissolved proteolytic enzymes to clean and heat to disinfect are described in U.S. Patent No. 4,614,549 (Ogunbiyi). The combined use of proteolytic enzymes and polymeric biguanides or polymeric quaternary ammonium compounds is described in copending, and commonly assigned United States Patent Application Serial No. 08/156,043 and in corresponding European Patent Application Publication No. 0 456 467 A2 (Rosenthal, et al.), as well as in U.S. Patent No. 5,096,607 (Mowrey-McKee, et al.). The commercial viability of most prior enzyme/disinfectant combinations has depended on the use of stable enzyme tablets. More specifically, the use of solid chemical agents used in treating contact lenses, particularly antimicrobial agents utilized to disinfect the lenses. The following patents may be referred to for further background concerning prior attempts to stabilize liquid enzyme formulations: U.S. Patents Nos. 4,462,922 (Boskamp); 4,537,706 (Severson); and 5,089,163 (Aronson). These patents describe detergent compositions containing enzymes. The detergent compositions may be used to treat laundry, as well as other industrial uses. Such detergents are not appropriate for treating contact lenses. The compositions of the present invention do not contain a detergent, or other agents potentially damaging or irritating to the eye. U.S. Patent No. 5,281,277 (Nakagawa) and Japanese Kokai Patent Applications Nos. 92-370197; 92-143718; and 92-243215 describe liquid enzyme compositions for treating contact lenses. The compositions of the present invention are believed to provide significant improvements relative to the compositions described in those publications. Summary of the Invention The present invention provides stable liquid enzyme compositions for cleaning contact lenses and methods for using the compositions. The liquid enzyme compositions of the present invention contain enzymes of high purity and structural integrity. This high purity and integrity limits: 1) the number of different potential antigenic substances on a contact lens; 2) the quantity of potential antigenic substances on a contact lens and 3) the unstabilizing feature of cross-degradation by dissimilar enzymes in liquid compositions. - 4 enzymatic cleaning compositions has been necessary to ensure stability of the enzymes prior to use. In order to use such compositions, a separate packet containing a tablet must be opened, the tablet must be placed in a separate vial containing a solution, and the tablet must be dissolved in order to release the enzyme into the solution. This practice is usually performed only once a week due to the cumbersome and tedious procedure and potential for irritation and toxicity. Moreover, the enzymatic cleaning tablets contain a large amount of excipients, such as effervescent agents (e.g., bicarbonate) and bulking agents (e.g., sodium chloride). As explained below, such excipients can adversely affect both cleaning and disinfection of the contact lenses. There have been prior attempts to use liquid enzyme compositions to clean contact lenses. However, those attempts have been hampered by the fact that aqueous liquid enzyme compositions are inherently unstable. When a proteolytic enzyme is placed in an aqueous solution for an extended period (i.e., several months or more), the enzyme may lose all or a substantial portion of its proteolytic activity. Steps can be taken to stabilize the compositions, but the use of stabilizing agents may have an adverse effect on the activity of the enzyme. For example, stabilizing agents can protect enzymes from chemical instability problems during storage in an aqueous liquid, by placing the enzymes in a dormant physical conformation. This conformation is referred to herein as being "partially denatured." However, such agents may also inhibit the ability of the enzymes to become active again (i.e., become "renatured") at the time of use. Finally, in addition to the general problems referred to above, a commercially viable liquid enzyme preparation for treating contact lenses must be relatively nontoxic, and must be compatible with other The liquid enzyme compositions of the present invention contains single enzymes of high integrity and purity, and an aqueous vehicle. In order to further enhance the stability of the compositions, the use of an aqueous vehicle which contains critical amounts of selected stabilizing agents is preferred. The stabilizing agents are combinations of a borate or boric acid compound and one or more 2-3 carbon polyols. The amounts of stabilizing agents utilized have been delicately balanced, such that maximum stability is achieved, while maximum activity is later obtained when the composition is put into use. Furthermore, the borate or boric acid compound also preserves the liquid enzyme compositions of the present invention from microbial contamination when the compositions are packaged in multiple use containers. The present invention also provides methods for cleaning contact lenses with the above-described liquid enzyme compositions. In order to clean a soiled lens, the lens is placed in a few milliliters of an aqueous solution and a small amount, generally one to two drops, of the enzyme composition is added to the solution. The lens is then soaked in the resultant cleaning solution for a time sufficient to clean the lens. The liquid enzyme compositions of the present invention are preferably combined with an aqueous disinfecting solution to simultaneously clean and disinfect contact lenses. As will be appreciated by those skilled in the art, the disinfecting solution must be formulated so as to be compatible with contact lenses. The antimicrobial activity of many chemical disinfecting agents is adversely affected by ionic solutes (e.g., sodium chloride). As explained below, the liquid enzyme compositions of the present invention are substantially nonionic, and therefore do not adversely affect the antimicrobial activity of such disinfecting agents. This is considered to be a major advantage of the present invention. The enzyme compositions of the present invention are formulated as concentrated, multi-dose liquids, and consequently do not contain conventional enzyme tablet excipients, such as sodium chloride (bulking agent) and bicarbonate (effervescent agent). The liquid enzyme compositions of the present invention utilize an aqueous vehicle. The primary components of the vehicle are one or more polyols and water. Both of these components are non-ionic. The liquid enzyme compositions of the present invention are thus substantially nonionic, and therefore have very little impact on the ionic strength of a disinfecting solution, and little to no effect on the antimicrobial activity of disinfecting solutions. The compositions and methods of the present invention provide greater ease of use. This ease of use enables contact lens users to clean their lenses 2 to 3 times a week, or more preferably, every day. It has been found that daily use of the liquid enzyme compositions of the present invention results in dramatically better cleaning and safety, as compared to the once-a-week enzyme cleaning regimens currently being utilized. Detailed Description of the Invention The enzymes which may be utilized in the compositions and methods of the present invention include all enzymes which: (1) are useful in removing deposits from contact lenses; (2) cause, at most, only minor ocular irritation in the event a small amount of enzyme contacts the eye as a result of inadequate rinsing of a contact lens; (3) are relatively chemically stable and effective in the presence of the antimicrobial agents described below; and (4) do not adversely affect the physical or chemical properties of the lens being treated. The proteolytic enzymes used herein are required to be of high purity and integrity. The enzymes of compositions of the present invention exhibit high gel electrophoretic ratios. As used herein, the term "high gel electrophoretic ratios" refers to a ratio of at least 99: 1 of the amount of the band of a proteolytic enzyme of the present invention to the amount of all other bands of material separated on the gel. The enzymes of the present invention also exhibit a substantially undenatured integrity. As used herein, the term "substantially undenatured integrity" refers to activity related to at least 95% of total protein. High purity and integrity enzymes can be obtained commercially. Various companies sell such enzymes including: NovoNordsk (Bagsvaerd, Denmark) and Sigma Chemical Co. (St. Louis, Missouri, U.S.A.). Alternatively, a crude enzyme can be purified and selected for substantially undenatured portions by typical methods known by those skilled in the art. For example, the use of column chromatography and crystallization techniques can generally be used to purify enzymes of the present invention. For purposes of the present specification, enzymes which satisfy the foregoing requirements are referred to as being "ophthalmically acceptable." Examples of suitable proteolytic enzymes include but are not limited to trypsin, subtilisin, collagenase, keratinase, carboxylase, aminopeptidase, Aspergillo peptidase, pronase E (from S ^ . griseus and dispase (from Bacillus, polymyxa) and mixtures thereof. Microbial derived enzymes, such as those derived from Bacillus. Streptomyces. and Aspergillus microorganisms, represent one type of enzyme which may be utilized in the present invention. Of this sub-group of enzymes, the most preferred are the Bacillus derived alkaline proteases generically called "subtilisin" enzymes. The identification, separation and purification of enzymes is known in the art. Many identification and isolation techniques exist in the general scientific literature for the isolation of enzymes. The enzymes contemplated by this invention can be readily obtained by known techniques from plant, animal or microbial sources. With the advent of recombinant DNA techniques, it is anticipated that new sources and types of stable proteolytic enzymes will become available. Such enzymes should be considered to fall within the scope of this invention so long as they meet the criteria for stability and activity set forth herein. Subtilisin and trypsin are preferred enzymes for use in the present invention. Subtilisin is derived from Bacillus bacteria and is commercially available from various commercial sources including Novo Industries (Bagsvaerd, Denmark), Fluka Biochemika (Buchs, Germany and Boehringer Mannheim. Trypsin is purified from various animal sources and is commercially available from Sigma Chemical Co. and Boehringer Mannheim. While Applicants do not wish to be bound by any theory, it is believed that the stability of the liquid enzyme compositions of the present invention is attributable to the high purity of the enzymes. More specifically, the use of enzymes having high gel electrophoretic ratios substantially eliminates the risk of cross-degradation by dissimilar enzymes. The stability of the compositions can be further enhanced by partially denaturing the enzymes. The enzymes are partially denatured by forming a complex with the stabilizing agents. The enzymes are denatured to a point where the enzymes are inactivated, but where renaturation is easily achieved by dilution of the denatured enzyme/stabilizing agent complex in an aqueous medium. It is believed that the stabilizing agents compete with water for hydrogen bonding sites on the proteins. Thus, a certain percentage of these agents will effectively displace a certain percentage of water molecules. As a result, the proteins will change conformation (partially denature) to an inactive and complexed (with the stabilizing agents) form. When the enzyme is in an inactive form, it is prevented from self-degradation and other spontaneous, chemically irreversible events. On the other hand, displacement of too many water molecules results in protein conformational changes that are irreversible. In order to obtain a stable liquid enzyme composition of significant shelf life and thus commercial viability, a delicate balance point of maximum stability and maximum reversible renaturation must be ascertained. Such a point has now been discovered. It has been found that the use of an aqueous vehicle which contains a polyol in combination with a borate compound further enhances the stability of the highly pure enzymes utilized in the present invention. The use of this type of vehicle is therefore preferred. The polyols utilized in the preferred vehicles described above are 2-3 carbon polyols. As used herein, the term "2-3 carbon polyol" refers to a compound with 2 to 3 carbon atoms and at least two hydroxy groups. Examples of 2-3 carbon polyols are glycerol, 1,2-propane diol ("propylene glycol"), 1,3-propane diol and ethylene glycol. Propylene glycol is the preferred 2-3 carbon polyol. The borate or boric acid compounds utilized in the preferred vehicles described above include alkali metal salts of borate, boric acid and borax. The most preferred borate or boric acid compound is sodium borate. As mentioned above, the borate or boric acid compound also contributes to the antimicrobial preservation of the liquid enzyme compositions of the present invention to a level effective for multi-use dispensing. The use of certain amounts of a 2-3 carbon polyol and a borate or boric acid compound enhances the stability and sustainable activity required in the liquid enzyme compositions of the present invention. More specifically, the combination of 50-70% volume/volume ("% v/v") of a 2-3 carbon polyol and 4-8% weight/volume ("% w/v") of a borate or boric acid compound is preferred to achieve enhanced stability and provide particularly efficacious and commercially viable liquid enzyme compositions, as described above. The combination of about 50% v/v of a 2-3 carbon polyol and about 7.6% w/v of sodium borate is most preferred. Examples 1 and 2 below further illustrate these preferred compositions of the present invention. The liquid enzyme compositions of the present invention will have an enzyme concentration sufficient to provide an effective amount of enzyme to clean a lens when a small amount of the composition is added to a diluent. As used herein, such an amount is referred to as "an amount effective to clean the lens." The amount of enzyme used in the liquid enzyme compositions of the present invention will generally range from 0.05 to 2% w/v. The selection of a specific concentration will depend on various factors, such as: the specificity and efficacy of the enzyme selected; the type of lenses to be cleaned; the intended frequency of cleaning (e.g., daily or weekly); and the intended duration of each cleaning. During storage, some of the activity of the enzyme may be lost, depending on length of storage and temperature conditions. Thus, the liquid enzyme compositions of the present invention may be prepared with initial amounts of enzyme that exceed the concentration ranges described herein. The preferred compositions of the present invention will generally contain one or more enzymes in an amount of about 300-6000 PAU/mL. The compositions will most preferably contain about 900-2200 PAU/mL, which corresponds to subtilisin in a range of about 0.1 to 0.3% w/v; and trypsin in the range of about 0.1 to 0.3% w/v. For purposes of this specification, a "proteolytic activity unit" or "PAU" is defined as the amount of enzyme activity necessary to generate one microgram (meg) of tyrosine per minute ("meg Tyr/min"), as determined by the casein- digestion, colorimetric assay described below. Casein-digestion assay A 5.0 mL portion of casein substrate (0.65% casein w/v) is equilibrated for 10 minutes (min) ± 5 seconds (sec) at 37°C. A 1.0 mL portion of enzyme solution (0.2 mg/ml) is then added to the casein substrate and the mixture vortexed, then incubated for 10 min ± 5 sec at 37°C. After incubation, 5.0 mL of 14% trichloroacetic acid is added and the resultant mixture immediately vortexed. The mixture is incubated for at least another 30 min, then vortexed and centrifuged for 15-20 min (approx. 2000 rpm). The supernatant of the centrifuged sample is filtered into a serum filter sampler and a 2.0 mL aliquot removed. To the 2.0 mL sample is added 5.0 mL of 5.3%) Na 2 CO 3 . The sample is vortexed, 1.0 mL of 0.67 N Folin's Phenol reagent is added, and the sample is immediately vortexed again, then incubated for 60 min at 37°C. The sample is then read on a visible light spectrophotometer at 660 nanometers (nm) versus purified water as the reference. The sample concentration is then determined by comparison to a tyrosine standard curve. The cleaning obtained with the liquid enzyme compositions of the present invention is a function of the time. The soaking times utilized will generally vary from about 1 hour to overnight. However, if longer soaking periods (e.g., 24 hours) were to be employed, lower concentrations than those described above can be utilized. The cleaning methods of the present invention involve the use of a small amount of the above-described liquid enzyme compositions to facilitate the removal of proteins and other deposits from contact lenses. The amount of enzyme composition utilized in particular embodiments of the present invention may vary, depending on various factors, such as the specificity and efficacy of the enzyme utilized, the proposed duration of exposure of lenses to the compositions, the nature of the lens care regimen (e.g., the frequency of lens disinfection and cleaning), the type of lens being treated, and the use of adjunctive cleaning agents (e.g., surfactants). However, the cleaning methods of the present invention will generally employ an amount of the above-described liquid enzyme compositions sufficient to provide a final enzyme concentration of about 5-75 PAU/mL of solution, following dispersion of the liquid enzyme compositions in a disinfecting solution or other aqueous solvent. A final concentration of about 5-25 PAU/mL is preferred. As indicated above, the liquid enzyme compositions of the present invention contain relatively minor amounts of ionic solutes. More specifically, the compositions do not contain bulking agents, effervescent agents or other ionic solutes commonly contained in prior enzyme tablets. The present compositions do contain the ionic solutes of borate or boric acid compounds and hydrochloric acid and/or sodium hydroxide, but the concentration of these solutes in the present compositions is relatively low. The compositions are therefore substantially nonionic. Moreover, as a result of the fact that the compositions are formulated as concentrated, multi-dose liquids, only a small amount of the compositions, generally one or two drops, is required to clean a contact lens. The present compositions therefore have very little impact on the ionic strength of disinfecting solutions. As explained below, this feature of the present invention is particularly important when the liquid enzyme compositions are combined with disinfecting solutions which contain ionic antimicrobial agents, such as polyquaternium-1. The antimicrobial activity of disinfecting agents, particularly polymeric quaternary ammonium compounds such as polyquaternium-1, is adversely affected by high concentrations of sodium chloride or other ionic solutes. More specifically, polymeric quaternary ammonium compounds, and particularly those of Formula (I), below, lose antimicrobial activity when the concentration of ionic solutes in the disinfecting solution is increased. The use of solutions having low ionic strengths (i.e., low concentrations of ionic solutes such as sodium chloride) is therefore preferred. Since both ionic solutes (e.g., sodium chloride) and nonionic solutes (e.g., glycerol) affect the osmolality and tonicity of a solution, osmolality and tonicity are indirect measures of ionic strength. However, the low ionic strengths preferably utilized in the cleaning and disinfecting methods of the present invention generally correspond to tonicities/osmolalities in the range of hypotonic to isotonic, and more preferably in the range of 150 to 350 milliOsmoles per kilogram (mOs/kg). A range of 200 to 300 mOs/kg is particularly preferred, and an osmolality of about 220 mOs/kg is most preferred. The liquid enzyme compositions of the present invention demonstrate effective cleaning efficacy while exhibiting minimal adverse effects or, more preferably, enhanced effects on the antimicrobial activity of disinfecting solutions. It has unexpectedly been discovered that the liquid enzyme compositions of the present invention enhance the antimicrobial activity of disinfecting solutions containing polyquaternium-1, a polymeric quaternary ammonium disinfecting agent. It has also been discovered that combinations of the liquid enzyme compositions and polyquaternium-1 disinfecting solutions become even more effective than the polyquaternium-1 disinfecting solutions alone when lenses are treated for extended periods of approximately one hour to overnight, with four to eight hours preferred. Since, for the sake of convenience, contact lenses are typically soaked overnight in order to be cleaned with enzymes or disinfected with chemical agents, this finding has practical significance. While Applicants do not wish to be bound by any theory, it is believed that the above-described enhancement of antimicrobial activity is due to the disruption or lysis of microbial membranes by the enzyme over time. The cleaning methods of the present invention utilize an aqueous solvent. The aqueous solvent may contain various salts such as sodium chloride and potassium chloride, buffering agents such as boric acid and sodium borate, and other agents such as chelating agents and preservatives. An example of a suitable aqueous solvent is a saline solution, such as Unisol® Plus Solution (registered trademark of Alcon Laboratories). The cleaning and disinfecting methods of the present invention utilize a disinfecting solution containing an antimicrobial agent. Antimicrobial agents can be oxidative, such as hydrogen peroxide, or non-oxidative polymeric antimicrobial agents which derive their antimicrobial activity through a chemical or physicochemical interaction with the organisms. As used in the present specification, the term "polymeric antimicrobial agent" refers to any nitrogen-containing polymer or co-polymer which has antimicrobial activity. Preferred polymeric antimicrobial agents include: polyquaternium- 1, which is a polymeric quaternary ammonium compound; and polyhexamethylene biguanide ("PHMB") or polyaminopropyl biguanide ("PAPB"), which is a polymeric biguanide. These preferred antimicrobial agents are disclosed in U.S. Patent Nos. 4,407,791 and 4,525,346, issued to Stark, and 4,758,595 and 4,836,986, issued to Ogunbiyi, respectively. The entire contents of the foregoing publications are hereby incorporated in the present specification by reference. Other antimicrobial agents suitable in the methods of the present invention include: other quaternary ammonium compounds, such as benzalkonium halides, and other biguanides, such as chlorhexidine. The antimicrobial agents used herein are preferably employed in the absence of mercury- containing compounds such as thimerosal. The most preferred antimicrobial agents are polymeric quaternary ammonium compounds of the structure: wherein: R] and R 2 can be the same or different and are selected from: N + (CH 2 CH 2 OH) 3 X " , N(CH 3 ) 2 or OH; X " is a pharmaceutically acceptable anion, preferably chloride; and n = integer from 1 to 50. The most preferred compound of this structure is polyquaternium-1, which is also known as Onamer M τ (registered trademark of Onyx Chemical Corporation) or as Polyquad ® (registered trademark of Alcon Laboratories, Inc.). Polyquaternium-1 is a mixture of the above referenced compounds, wherein X ' is chloride and R R 2 and n are as defined above. The above-described antimicrobial agents are utilized in the methods of the present invention in an amount effective to eliminate substantially or to reduce significantly the number of viable microorganisms found on contact lenses, in accordance with the requirements of governmental regulatory agencies, such as the United States Food and Drug Administration. For purposes of the present specification, that amount is referred to as being "an amount effective to disinfect" or "an antimicrobially effective amount." The amount of antimicrobial agent employed will vary, depending on factors such as the type of lens care regimen in which the method is being utilized. For example, the use of an efficacious daily cleaner in the lens care regimen may substantially reduce the amount of material deposited on the lenses, including microorganisms, and thereby lessen the amount of antimicrobial agent required to disinfect the lenses. The type of lens being treated (e.g., "hard" versus "soft" lenses) may also be a factor. In general, a concentration in the range of about 0.000001% to about 0.01% by weight of one or more of the above-described antimicrobial agents will be employed. The most preferred concentration of the polymeric quaternary ammonium compounds of Formula (I) is about 0.001% by weight. Oxidative disinfecting agents may also be employed in the methods of the present invention. Such oxidative disinfecting agents include various peroxides which yield active oxygen in solution. Preferred methods will employ hydrogen peroxide in the range of 0.3 to 3.0 % to disinfect the lens. Methods utilizing an oxidative disinfecting system are described in U. S. Patent No. Re 32,672 (Huth, et al.), the entire contents of which are hereby incoφorated in the present specification by reference. As will be appreciated by those skilled in the art, the disinfecting solutions utilized in the present invention may contain various components in addition to the above- described antimicrobial agents, such as suitable buffering agents, chelating and/or sequestering agents and tonicity adjusting agents. The disinfecting solutions may also contain surfactants. The methods of the present invention will typically involve adding a small amount of a liquid enzyme composition of the present invention to about 2 to 10 mL of an aqueous solvent or disinfecting solution, placing the soiled lens into the enzyme/solvent or enzyme/disinfectant solution, and soaking the lens for a period of time effective to clean or clean and disinfect the lens. The amount of liquid enzyme composition utilized can vary based on factors such as the amount of disinfecting solution used, but generally it is about 1 to 2 drops. Preferred methods involve adding 1 drop (approximately 30 μL) to 5 mL of aqueous solvent or disinfecting solution. The soiled lens can be placed in the aqueous solvent or disinfecting solution either before or after the addition of the liquid enzyme composition. Optionally, the contact lenses are first rubbed with a non-enzymatic daily surfactant cleaner prior to immersion in the enzyme/solvent or enzyme/disinfectant solution. The lens will typically be soaked overnight, but shorter or longer durations are contemplated by the methods of the present invention. A soaking time of 4 to 8 hours is preferred. The methods of the present invention allow the above-described regimen to be performed once per week, but more preferably, every day. The following examples are presented to illustrate further, various aspects of the present invention, but are not intended to limit the scope of the invention in any respect. EXAMPLE 1 A specific liquid subtilisin composition of the present invention, and a suitable disinfecting solution for use in combination with that composition, are described below: A. Liquid Subtilisin Composition The following liquid enzyme formulation represents a preferred embodiment of the present invention: Ingredient amount Subtilisin 0.1% (w/v)* Sodium borate 7.62% (w/v) Propylene glycol 50% (v/v) Water QS Hydrochloric acid/sodium QS* hydroxide * corresponds to an amount to adjust the pH to 6.0 Note: (w/v) means weight/volume; (v/v) means volume/volume; and QS means quantity sufficient The above formulation was prepared by first sequentially mixing propylene glycol, purified water, hydrochloric acid and sodium borate together. The solution was polish filtered (1.2 mm filter) into a sterile receiving tank, and then sterile filtered (0.2 mm filter). The required amount of subtilisin was then dissolved an appropriate amount of water and the solution was polished filtered (0.6 mm filter). This enzyme solution was then sterile filtered (0.2 mm filter) into the sterile receiving tank containing the sterilized propylene glycol/sodium borate solution. With appropriate mixing, the contents of the receiving tank were then brought to volume with an appropriate amount of water. The optimal pH of the above formulation was in the range of 6-7, a pH of 6 is most preferred. B. Disinfecting Solution The following formulation represents a preferred disinfecting solution: Ingredient weight/volume (%) Polyquatemium-l 0.001 + 10% excess Sodium chloride 0.48 Disodium Edetate 0.05 Citric acid monohydrate 0.021 Sodium citrate dihydrate 0.56 Purified water QS To prepare the above formulation, sodium citrate dihydrate, citric acid monohydrate, disodium edetate, sodium chloride and Polyquaternium-1, in the relative concentrations indicated above, were mixed with purified water and the components allowed to dissolve by stirring with a mixer. Purified water was added to bring the solution to almost 100%. The pH was recorded at 6.3 and adjusted to 7.0 with NaOH. Purified water was added to bring the solution to 100%. The solution was stirred and a pH reading of 7.0 was taken. The solution was then filtered into sterile bottles and capped. EXAMPLE 2 A preferred liquid trypsin composition of the present invention for use in combination with a suitable disinfecting solution, e.g. EXAMPLE IB., are described below: Liquid Trypsin Compositions Ingredient amount Trypsin 0.3% (w/v) Sodium borate 7.62% (w/v) Propylene glycol 50% (v/v) Water QS Hydrochloric acid/sodium QS* hydroxide * corresponds to an amount to adjust the pH to 6.0 The above liquid trypsin compositions are made in the same manner as the liquid subtilisin composition, described in EXAMPLE 1 , are made. EXAMPLE 3 A stability study comparing trypsin and pancreatin in the liquid enzyme composition of EXAMPLE 1, wherein trypsin, at 0.3% weight/volume, and pancreatin, at 1.7% w/v was substituted for subtilisin, was performed. The data are shown in Table I below. Aliquots of the compositions were stored in a chamber held to 35° C. At the appointed time, aliquots were tested for enzyme activity. Activity levels were compared with initial levels and expressed as percent remaining activity. TABLE I: STABILITY OF LIQUID ENZYME COMPOSITIONS CONTAINING TRYPSIN OR CHYMOTRYPSIN STORED AT 35° C % Remaining Activity Time Trypsin Pancreatin 24 hours 100 83.0 1 weeks 100 76.5 2 weeks 96.0 81.1 3 weeks 93.2 80.2 4 weeks 93.2 78.3 The trypsin composition demonstrated an excellent stability profile at 35 C, whereas the multiple enzyme pancreatin, containing trypsin, chymotrypsin, lipas, amyl ase and carboxypeptidase, was less stable. EXAMPLE 4 The disinfecting efficacy of a composition of the present invention was evaluated by determining the rate and extent of kill achieved with an aqueous system formed by combining the liquid enzyme composition and disinfecting solution described in EXAMPLE 1 above. That system was tested against Serratia marcescens. The test procedures and results are described below. A 0.1 ml volume of inoculum (10 colony forming units/mL) was first added to a 10 ml volume of the disinfecting solution of EXAMPLE 1, followed by the addition of 2 drops of the liquid enzyme composition of EXAMPLE 1. A similarly inoculated 10 ml volume of the disinfecting solution of EXAMPLE 1 was used as a control. The solutions were maintained at room temperature throughout the test. Each microorganism and test solution was tested individually. Sets of four replicate (n = 8) samples were tested for each organism. At selected time intervals of 4 and 24 hours a 1 ml volume of the inoculated test solution was removed and appropriate serial dilutions were made in sterile 0.9% sodium chloride solution dilution blanks. Pour-plates were prepared with soybean-casein digest agar containing 0.07% Asolectin and 0.5% Polysorbate 80. At Time 0, a 1.0 ml volume of the saline control was removed and serial dilution pour-plates were prepared using the same recovery medium and dilution blanks. The Time 0 saline control count was used as the initial count. The pour-plates were incubated at 30°-35°C for appropriate incubation periods. The number of surviving organisms at each time interval was then determined. The results are summarized in Tables II below. TABLE II EFFECTS OF A SUBTILISIN CONTAINING LIQUID ENZYME COMPOSITION ON THE ANTIMICROBIAL ACTIVITY OF A POLYQUATERNIUM- 1 DISINFECTING SOLUTION LOG REDUCTION Time Disinfecting Solution Liquid Enzyme Control (subtilisin)+ Disinfecting Solution 4 hours 0.85 ± 0.07 1.33 ± 0.15 24 hours 3.65 ± 0.35 3.37 ± 1.01 As illustrated in Table II, the liquid enzyme composition containing subtilisin had an enhancing effect on the antimicrobial activity of the disinfecting solution of EXAMPLE 1 through 4 hours of incubation, and a negligible effect at 24 hours. EXAMPLE 5 The disinfecting efficacy of a further embodiment of the present invention was evaluated by determining the rate and extent of kill achieved with an aqueous system formed by combining the liquid trypsin composition of Example 2 and the disinfecting solution described in Example 1. The system was tested against Serratia marcescens. Staphylococcus aureus. Pseudomonas aeruginosa. Candida albicans and Fusarium solani. The test procedure in Example 4 was followed. Sample times were 4, 6 and 24 hours. The test results, expressed as log reductions are presented in Table III below. TABLE III: EFFECTS OF A TRYPSIN CONTAINING LIQUID ENZYME COMPOSITION ON THE ANTIMICROBIAL ACTIVITY OF A POLYQUATERNIUM- 1 DISINFECTING SOLUTION LOG REDUCTION Liquid Trypsin Disinfecting Microorganism Time Composition and solution (hours) disinfecting alone solution S. marcescens 4 1.9 ± 0.1 1.3 ± 0.1 6 2.0 ± 0.6 1.5 ± 0.1 24 4.4 ± 0.8 3.4 ± 0.5 S. aureus 4 3.1 ± 0.2 2.6 ± 0.2 6 3.5 ± 0.3 3.0 ± 0.0 24 4.9 ± 0.0 4.6 ± 0.3 P. aeruginosa 4 3.8 ± 1.0 2.3 ± 0.9 6 4.2 ± 0.7 2.9 ± 1.0 24 4.9 ± 0.0 4.4 ± 0.5 C. albicans 4 0.1 ± 0.1 0.1 ± 0.2 6 0.1 ± 0.2 0.1 ± 0.2 ' 24 0.1 ± 0.2 0.2 ± 0.3 F. solani 4 3.8 ± 0.6 3.4 ± 1.3 6 4.5 ± 0.4 3.6 ± 0.3 24 4.6 ± 0.2 4.3 ± 0.5 The invention in its broader aspects is not limited to the specific details shown and described above. Departures may be made from such details within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its advantages.

Claims: What is Claimed is: 1. A stable, concentrated, liquid enzyme composition for cleaning contact lenses comprising: an enzyme in an amount effective to clean the lens, said enzyme having a gel electrophoretic ratio of at least 99:1, and an aqueous vehicle for said enzyme, wherein the enzyme is substantially undenatured upon dilution in an aqueous solvent. 2. A composition according to Claim 1, wherein the aqueous vehicle comprises 4-8% weight/volume of a borate compound, 50-70% weight/volume of a 2-3 carbon polyol, and water. 3. A composition according to Claim 1, wherein the enzyme is trypsin. 4. A composition according to Claim 2, where in the enzyme is trypsin. 5. A composition according to Claim 2, wherein the borate compound is sodium borate and the 2-3 carbon polyol is 1,2-propane diol. 6. A composition according to Claim 5, wherein the composition contains 7.6? % Ό weight/volume sodium borate and 50% weight/volume 1,2-propane diol. 7. A composition according to Claim 6, wherein the enzyme is trypsin. 8. A method of cleaning a contact lens which comprises: placing the lens in an aqueous solvent; dispersing a small amount of a stable, concentrated, liquid enzyme cleaning composition in the aqueous solvent to form an aqueous enzymatic cleaning solution, said cleaning composition comprising: an enzyme in an amount effective to clean the lens, said enzyme having a gel electrophoretic ratio of at least 99:1, and an aqueous vehicle for said enzyme, and soaking the lens in the enzymatic cleaning solution for a period of time sufficient to clean the lens; wherein the enzyme is substantially undenatured upon dispersion in the aqueous solvent. 9. A method according to Claim 8, where the aqueous vehicle comprises 50-70% weight/volume of a 2-3 carbon polyol, 4-8% weight/volume of a borate compound, and water. 10. A method according to Claim 8, wherein the enzyme is trypsin. 11. A method according to Claim 9, wherein the enzyme is trypsin. 12. A method according to Claim 9, wherein the borate compound is sodium borate and the 2-3 carbon polyol is 1,2-propane diol. 13. A method according to Claim 12, wherein the composition contains 7.6% weight/volume sodium borate and 50% weight/volume 1,2-propane diol. 14. A method according to Claim 13, wherein the enzyme is trypsin. 15. A method according to Claim 14, wherein the method is performed daily. 16. A method for cleaning and disinfecting a contact lens which comprises: placing the lens in an aqueous disinfecting solution containing an amount of an antimicrobial agent effective to disinfect the lens; dispersing a small amount of a stable, concentrated, liquid enzyme cleaning composition in said disinfecting solution to form an aqueous disinfectant enzyme solution, said cleaning composition comprising: an enzyme in an amount effective to clean the lens, said enzyme having a gel electrophoretic ratio of at least 99:1, and an aqueous vehicle for said enzyme, and soaking the lens in the aqueous disinfectant/enzyme solution for a period of time sufficient to clean and disinfect the lens; wherein the enzyme is substantially undenatured upon dispersion in the disinfecting solution. 17. A method according to Claim 16, wherein the cleaning composition further comprises 50-70%) weight/volume of a 2-3 carbon polyol, 4-8% weight/volume of a borate compound, and water. » 18. A method according to Claim 16, wherein the enzyme is trypsin. 19. A method according to Claim 17, wherein the enzyme is trypsin. 20. A method according to Claim 17, wherein the borate compound is sodium borate and the 2-3 carbon polyol is 1,2-propane diol. 21. A method according to Claim 20, wherein the composition contains 7.6% weight/volume sodium borate and 50% weight/volume 1,2-propane diol. 22. A method according to Claim 21, wherein the enzyme is trypsin. 23. A method according to Claim 22, wherein the method is performed daily.

Inventors: STONE RALPH P, VAN DUZEE BARRY F, STONE, RALPH, P., VAN DUZEE, BARRY, F.
Applicants: ALCON LAB INC, DUZEE BARRY F VAN, STONE RALPH P, ALCON LABORATORIES, INC., STONE, RALPH, P., VAN DUZEE, BARRY, F.
Application year: 1996
Main classification: C11D3
IPC codes: A61L2, C11D3, C11D7