described herein are methods of preparing collagen films containing therapeutic compounds that readily dissolve upon exposure to normal human body temperature ( 35 - 37 ° c .). these collagen films can be used for the rapid and accurate delivery of compounds to specific tissue sites . for the purposes of this invention , collagen can be collected , solubilized , subjected to modification by mono - reactive , amine - modifying agents , and re - precipitated by any standard technique , e . g ., those provided in devore et al . ( u . s . pat . no . 4 , 713 , 446 ), herein incorporated by reference . the following example is provided as an illustration and is in no way intended to limit the scope of the invention . as a first step toward producing rapidly dissolving films , soluble collagen was prepared by standard procedures . young calf hide was washed thoroughly with reagent alcohol and with deionized , pyrogen - free water , cut into approximately 1 cm 2 sections , and stirred overnight in 40 volumes of 0 . 5 m acetic acid . the mixture was then supplemented with pepsin ( 3 % hide wet weight ) and stirred for 72 hours . the digested , solubilized collagen was filtered through cheesecloth and precipitated by increasing the nacl concentration to 0 . 8 m . the collagen was then cycled twice through steps of redissolution , in 0 . 5 m acetic acid , and reprecipitated . the collagen precipitate was then redissolved in 0 . 1 n acetic acid , dialyzed against 0 . 1 m acetic acid , filtered ( 0 . 45 μm ), and refiltered ( 0 . 22 μm ). the purified , telopeptide - poor collagen was derivatized with glutaric anhydride as previously described ( u . s . pat . nos . 5 , 631 , 243 and 5 , 492 , 135 ). briefly , the collagen solution ( approximately 3 mg / ml ) was adjusted to ph 9 . 0 with 10 n and 1 n naoh . while stirring the solution , glutaric anhydride was added at 10 % ( weight of collagen ). for twenty minutes , the stirring continued , and the ph was maintained . the ph of the solution was adjusted to 4 . 3 with 6 n and 1 n hcl to precipitate the derivatized collagen . the precipitate was centrifuged at 3500 rpm for 30 minutes . the pellet was washed three times in pyrogen - free deionized water and then redissolved in phosphate buffered glycerol ( 2 % glycerol in 0 . 004 m phosphate buffer , ph 7 . 4 ) to achieve a final concentration of approximately 10 mg / ml . to prepare collagen films containing mitomycin , the collagen solution , described above , was heated in a 35 ° c . water bath for 30 minutes to reduce viscosity . mitomycin ( e . g ., mutamycin ®, bristol myers squibb , princeton , n . j . ), also known as mitomicin c , was added to the heated collagen . the collagen solution was then poured into petri dishes in a thin layer and allowed to air dry under a laminar - flow hood . collagen film melting time at 35 ° c . was measured after placing the films in 0 . 8 % saline in a 35 ° c . water bath . pre - heated collagen films melted in approximately one minute . in contrast , collagen films poured into petri dishes without pre - heating melted at 35 ° c . in approximately 30 minutes . mitomycin - containing collagen films had a final mitomycin concentration of 400 μg per 16 mm 2 . 6 mm diameter discs were cut from the film and applied to human subconjunctival fibroblasts derived from tenon &# 39 ; s membrane layered in 96 well plates ( csm supplemented with 10 % fetal bovine serum ). after 72 hours , mitomycin - induced inhibition of cell division was assessed by measuring the reduction in fluorescence intensity ( rfu ) using a fluorogenic calceinam assay ( see , for example , decherchi et al ., j . neurosci . meth . 71 : 205 ( 1997 ); sugita , pflitgers arch . 429 : 555 ( 1995 ); padanilam et al ., ann . ny acad . sci . 720 : 111 ( 1994 ); lichtenfels et al ., j . immunol . meth . 172 : 227 ( 1994 ); and wang et al ., human immunol . 37 : 264 ( 1993 )). the mitomycin - containing collagen films inhibited approximately 91 % of the cell division demonstrated in control cells . mitomycin - containing films may be stored for later use . for example , mitomycin activity in the collagen films described above was maintained for at least 6 weeks after preparation of the films ( stored at 4 ° c .). administration of mitomycin - collagen films , 2 , 4 , and 6 weeks old , demonstrated 91 %, 90 %, and 92 % inhibition of cell division , respectively , compared to mitomycin - free controls . these values were comparable to the % cell death inhibition elicited by administration of a freshly prepared mitomycin solution ( 0 . 4 mg / ml solution , dissolved in usp sterile water ). in contrast to the stability of mitomycin in the collagen film , hplc analysis of the mitomycin solution determined that stability was maintained for only 4 days following storage at ambient temperature and 4 ° c . in the dark . dissolution and storage in 0 . 9 % saline or phosphate buffer ( ph 7 . 4 ) is not recommended due to degradation and precipitation . rapidly dissolving collagen films containing therapeutic compounds are useful for various treatments . for example , the collagen - mitomycin film may be administered to the external opening of the fistula created during glaucoma filtering surgery ( trabeculectomy ). immediately following surgery , a collagen film , e . g ., a 4 × 4 mm patch , containing 100 - 1000 μg mitomycin ( preferably 400 μg ), is directly applied to the external opening of the fistula prior to replacing the scleral flap . administration of the mitomycin increases the duration of fistula patency , increasing filtration from the eye and reducing intraocular pressure . other compounds may also be administered to the trabeculectomy - created fistula to increase filtration during recovery . for example , 5 - fluorouracil - containing films may be administered in the same fashion to deliver a 5 - fluorouracil dose of 25 - 250 μg ( preferably 100 μg ). other alternative compounds that are effective for this treatment are anti - fibrotic , angiostatic , and anti - viral compounds . administration of the rapidly dissolving collagen films containing inhibitors of cell proliferation are also useful for treatment during recovery from other surgical procedures where prevention of wound healing is beneficial . in addition , the collagen films of the invention may be administered to reduce cellular proliferation in specific tissue sites , such as for the localized inhibition of neoplastic or non - neoplastic cell growth . for this application , any chemotherapeutic compound may be dissolved in the collagen matrix in concentrations appropriate for inhibiting cell growth . while the treatment regimens described herein are preferably applied to human patients , they also find use in the treatment of other animals , such as domestic pets or livestock . moreover , while the invention has been described in connection with specific embodiments thereof , it will be understood that it is capable of further modifications and this application is intended to cover any variations , uses , or adaptations of the invention following , in general , the principles of the invention and including such departures from the present disclosure come within known or customary practice within the art to which the invention pertains and may be applied to the essential features hereinbefore set forth , and follows in the scope of the appended claims .
disclosed herein are collagen films which rapidly dissolve at 35 ° c . also disclosed are methods for the preparation of the collagen films and their use as a vehicle for delivering a dose of therapeutic compound to a specific tissue site .