Shield, collagen

Bioconjugates Biocontamination Bio-Cor collagen shield Bio-Cox Biocytin Biodegradability... 

The collagen shield, fabricated from procine scleral tissue, is a spherical contact lens-shaped film whose thickness can be made to vary from 0.027 to 0,071 mm. It has a diameter of 14.5 mm and a base curve of 9 mm. Once the shield is hydrated by tear fluid and begins to dissolve, it softens and conforms to the corneal surface. Dissolution rates can be varied from 2 to as long as 72 hr by exposing the shields to ultraviolet radiation in order to achieve varying degrees of crosslinking. 

JA Hobden, JJ Reidy, RJ O Callaghan, MS Insler, JM Hill. (1990). Quinolones in collagen shields to treat aminoglycoside-resistant pseudomonas keratitis. Invest Ophthalmol Vis Sci 31 2241-2243. 

U Pleyer, B Elkins, D Ruckert, S Lutz, J Grammer, J Chou, KH Schmidt, BJ Mon-dino. (1994). Ocular absorption of cyclosporine A from liposomes incorporated into collagen shields. Curr Eye Res 13 177-181. 

JK Milani, I Verbukh, U Pleyer, H Sumner, S Adamu, HP Halabi, HJ Chou, DA Lee, BJ Mondino. (1993). Collagen shields impregnated with gentamicin-dexa-methasone as a potential drug delivery device. Am J Opthalmol 116 622-627. 

JT Jacob-LaBarre, HE Kaufman. (1990). Investigation of pilocarpine loaded poly-butylcyanoacrylate nanocapsules in collagen shields as a drug delivery system. Invest Ophthalmol Vis Sci 31(Suppl) 485-488. 

Grammer et al. [120] studied collagen shield with dissolution times of 12 h, that were presoaked with either hydrophilic or lipophilic fluorophore (4,5-carboxyfluorescein and jV-[Lissamine rhodamine B sulfonyl]-diacyl-phosphatidylethanolamine, respectively), in a solution or unilamellar liposome suspension with different surface charges and bilayer fluidity. For the hydrophilic fluorophore, two to seven times higher concentrations were achieved in the collagen shield by immersion in aqueous solution than immersion in the liposome suspensions. 

The release kinetics data results indicated that liposome surface charge and bilayer fluidity are of minor importance for the interaction of liposomes with collagen shields. Moreover, the release kinetics of hydrophilic or lipophilic substance from collagen shield was similar for both liposome-encapsulated and nonencapsulated drug. Thus, these results suggest that there is no added value for combined application of collagen shields and liposomes. In another study, the combination of collagen shield and liposomes enhanced CsA ocular penetration but failed to provide sustained release compared to CsA liposomal suspension [121]. 

Phinney, R.B., et al. 1988. Collagen-shield delivery of gentamicin and vancomycin. Arch Ophthalmol 106 1599. 

Pleyer, U., et al. 1992. Use of collagen shields containing amphotericin B in the treatment of experimental Candida albicans-induced keratomycosis in rabbits. Am J Ophthalmol 113 303. 

Silbiger, J., and G.A. Stern. 1992. Evaluation of corneal collagen shields as a drug delivery device for the treatment of experimental Pseudomonas keratitis. Ophthalmology 99 889. 

Clinch, T.E., et al. 1992. Collagen shields containing tobramycin for sustained therapy (24 hours) of experimental Pseudomonas keratitis. CLAO J 18 245. 

Callegan, M.C., et al. 1994. Efficacy of tobramycin drops applied to collagen shields for experimental staphylococcal keratitis. Curr Eye Res 13 875. 

Hwang, D.G., et al. 1989. Collagen shield enhancement of topical dexamethasone penetration. Arch Ophthalmol 107 1375. 

Chen, Y.F., et al. 1990. Cyclosporine-containing collagen shields suppress corneal allograft rejection. Am J Ophthalmol 109 132. 

Porcine collagen shields, which are designed to promote corneal healing and provide lubricity to the eye. 

Liposomes to deliver cyclosporin A (CsA) have been incorporated into collagen shields. This delivery system provided the highest levels of CsA in both the cornea and sclera with higher levels in the aqueous humor compared to unencapsulated and capsulated CsA but not loaded into collagen shields. 

Soft contact lenses and collagen shields absorb drugs from solution and then slowly release them when placed on the eye. This form of drug therapy can be valuable when continuous treatment is desired (see Chapter 3). 

Currently available collagen shields have variable dissolution rates of 12, 24, or 72 hours depending on the... 

Figure 3-12 Rehydrated collagen shield on eye. (Courtesy Bausch Lomb, Inc.)...

Friedberg ML, Pleyer U, Mondino J. Device drug deUvery to the eye collagen shields, iontophoresis and pumps. Ophthalmology 1991 98 725-732. 

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