the present invention provides a gel - like composition which may be used as a superabsorber , a hydrogel , a sustained release vehicle , an entrapment molecule , and for a variety of other uses . the gels formed are stable so long as they are moist and ph range is not varied such that the ionic cross - linking is interrupted . normally , the gels are stable in a slightly acidic to neutral ph while at very high acid or alkaline ph , the gels disintegrate . a variety of factors can change the consistency and other properties of the gel to tailor the gel to desired specifications . for example , the use of an additional cross - linking agent such as the organo - metallic cross - linking agent described in u . s . patent applic . ser . no . 320 , 944 can strengthen certain of the gels . as the concentration of the carbohydrate or the cross - linker rises , the stiffness and spreadability of the gels change , becoming stiffer as more carbohydrate or cross - linker is used . changing the ionic strength of the fluid in the material also makes a difference in the property of the gels , with the gels tending to be more fluid at low ionic strengths and firmer at higher salt concentrations . this is in contrast to the carbopols often used in cosmetics as thickeners which collapse with increasing ionic strength . as noted , the gels are somewhat ph sensitive but appear substantially insensitive to ph changes between 3 . 5 and 6 . 5 . some or part of the water used in the gel may be replaced by other aqueous miscible solvents such as ethanol ( up to 35 %) or glycerol or propylene glycol ( up to 60 %). the gels can encapsulate oils such as mineral oil , silicone oil , para - aminobenzoate esters , diethyltoluamide ( deet ) and cinnamate sunscreens . the gels also may contain suspensions of a particulate such as benzoyl peroxide , or may contain a variety of water soluble amino acids , sugars , proteins , and water soluble dyes including dihydroxy acetone or amphotercin b . further , the gels may contain a variety of other drugs such as erythromycin , salicylic acid , metronidazole , and retinoic acid . when the gels dry , they will form water vapor barriers on the skin which is of importance because of the skin moisturizer action . this example shows a gel made using a tetracycline derivative , specifically oxytetracycline . table 1 shows the ingredients and proportions used . table 1______________________________________5 mm sodium acetate in water 80 mlcarboxymethylcellulose ( cmc7l2p ) 2 . 12 goxytetracycline hcl 24 g2n sodium hydroxide 21 . 4 ml______________________________________ the gel was made by dissolving the carboxymethylcellulose in the sodium acetate solution which had been heated to approximately 40 ° c . a clear solution is obtained . after cooling to 30 - 32 ° c ., the oxytetracycline hydrochloride is added with stirring . the suspension is then mixed with sodium hydroxide and the ph is adjusted , using the sodium hydroxide , to 4 . 5 . the gel sets instantly . the resulting gel is a fine suspension which settles out of solution but can be redispersed . this gel , upon breakdown or dissociation , would yield the oxytetracycline , making it particularly useful for veterinary applications where oxytetracycline is used often as an antibiotic . a major benefit is that the oxytetracycline - carboxymethylcellulose complex is non - irritating . in this example , a quinone derivative , norfloxacin was used to make a gel . norfloxacin ( sigma chemical company ) has the formula the ingredients shown in making the gel are listed in table 2 . table 2______________________________________a . carboxethylcellulose ( cmc7l2p ) 4 . 0 g 0 . 9 % saline 50 mlb . norfloxacin 6 . 0 g acetic acid 2 ml 0 . 9 % saline 50 ml______________________________________ the procedure used to make the norfloxacin gel was slightly different than that used to make the oxytetracycline complex . first 40 ml of 0 . 9 % saline is heated to 40 ° c . and the carboxymethylcellulose is dissolved to give a clear solution . the solution is cooled to room temperature and 0 . 9 % saline is added to make a volume of 50 ml . at the same time , the acetic acid is mixed with 40 ml of the 0 . 9 % saline and the norfloxacin is dissolved into it . the volume is again corrected to 50 ml . the two resulting solution are then mixed together , e . g ., by mixing between two syringes . the resulting suspension , which can be sedimented by centrifugation and resuspended , is then adjusted to ph 4 . 5 using acetic acid . the gel formed of norfloxacin does not settle out of solution like that formed with oxytetracycline but could have similar uses . this example illustrates the use of conazoles within the scope of the invention is making gels . the two conazoles used are miconazole and econazole . both of these conazoles have side chains with two chlorinated benzene rings attached the imidazole ring , the difference being the number of chlorines on one of the benzene rings . the structures of miconazole ( top ) and econazole ( bottom ) are shown below . ## str4 ## the procedure used to form each of the gels was identical . table 3 has the materails used to form the miconazole gel . table 3______________________________________carboxymethylcellulose ( cmc7hf ) 1 gwater 75 mlmiconazole nitrate 1 galuminum acetate ( boric salt ) 12 . 5 g0 . 9 % saline 1 . 25 mlethanol 23 . 75 ml______________________________________ while table 4 has the materials used to form the econazole gel . table 4______________________________________carboxymethylcellulose ( cmc7hf ) 1 gwater 75 mleconazole nitrate 1 galuminum acetate ( boric salt ) 12 . 5 g0 . 9 % saline 1 . 25 mlethanol 23 . 75 ml______________________________________ in both cases , 70 ml of water was heated to approximately 60 ° c . and the carboxymethylcellulose was dissolved therein to get a clear solution . the solution was cooled to room temperature and water was added to make a volume of 75 ml . at the same time , the aluminum acetate was dissolved into the 0 . 9 % saline and mixed with 25 ml of the alcohol . the conazole was then dissolved into the aluminum acetate / saline / ethanol solution and the volume was raised to 25 ml with alcohol . the two resulting solutions were then mixed together , e . g ., using two syringes , to obtain even suspension . the material was allowed to gel for several hours at room temperature . the resulting gel became firmer with time . by changing the concentration of the ethanol ( replacing it with water or saline ), the properties of the gel can be modified . in addition to the two conazoles described above , other conazoles without the aromatic side chains have been tried . none of these formed a gel , probably because they did not have a second site for a partial positive charge other than the ring structure . accordingly , these other conazoles did not have the ability to ionically cross - link the carboxymethylcellulose properly . the gels of the present invention could also have particulates , including lipid vesicles , suspended therein . since these lipid vesicles can also be designed to carry a variety of materials which cannot otherwise be carried in the gel , a wound patch or other covering made of the gel with vesicles dispersed therein could be used to apply a variety of drugs on a sustained release basis to a selected site . using this hybrid material , it would be possible to deliver incompatible materials by encapsulating one within a lipid vesicle and suspending the lipid vesicle within the gel containing the other . those skilled in the art will be able determine other modifications of the exemplary procedures and materials . such other modifications are with the scope of the following claims .
a new gel - like composition of matter containing a complex carbohydrate with a high degree of carboxyl substitution cross - linked by an organic cross - linker has been developed . the cross - linkers have complex ring structures , e . g ., polynuclear or heterocyclic compounds , which permit development of two distinct partial positive charges under conditions where a carbohydrate is negatively charged . antibiotics are the preferred cross - linking agents and a method of sustained release of the antibodies is also disclosed .