Collagen-Hydroxypropyl Methylcellulose Membranes for Corneal Regeneration.

To improve intraocular transparency of collagen matrices, hydroxypropyl methylcellulose (HPMC) was introduced for the first time into cross-linked collagen to form collagen-HPMC composite membranes. Light transmittance and refractive indices of the membranes are enhanced by incorporation of HPMC in comparison to the control of cross-linked collagen membranes. Maximum light transmittance of the collagen-HPMC membrane was up to 92%. In addition, their permeability of nutrients such as glucose, tryptophan, and NaCl was superior or comparable to that of human corneas. In vitro results demonstrated that the collagen-HPMC membrane supported adhesion and proliferation of human corneal epithelial cells (HCECs), showing good cytocompatibility to HCECs. The corneas maintained a smooth surface and clear stroma postoperatively after 7 months of implantation of collagen-HPMC membranes into the corneas of rabbits. The good intraocular biocompatibility was verified by maintaining a high optical clarity for over 6 months after transplantation. Hematoxylin and eosin staining results showed the growth of stromal keratocytes into the collagen-HPMC implants, indicating the ability of the collagen-HPMC membrane to induce corneal cell regeneration. Taken together, the collagen-HPMC membrane might be a promising candidate for use in corneal repair and regeneration.

Coating of silicone with mannoside-PAMAM dendrimers to enhance formation of non-pathogenic Escherichia coli biofilms against colonization of uropathogens.

Bacterial interference using non-pathogenic Escherichia coli 83972 is a novel strategy for preventing catheter-associated urinary tract infection (CAUTI). Crucial to the success of this strategy is to establish a high coverage and stable biofilm of the non-pathogenic bacteria on the catheter surface. However, this non-pathogenic strain is sluggish to form biofilms on silicone as the most widely used material for urinary catheters. We have addressed this issue by modifying the silicone catheter surfaces with mannosides that promote the biofilm formation, but the stability of the non-pathogenic biofilms challenged by uropathogens over long-term remains a concern. Herein, we report our study on the stability of the non-pathogenic biofilms grown on propynylphenyl mannoside-modified silicone. The result shows that 94% non-pathogenic bacteria were retained on the modified silicone under >0.5 Pa shear stress. After being challenged by three multidrug-resistant uropathogenic isolates in artificial urine for 11 days, large amounts (>4 × 106 CFU cm-2) of the non-pathogenic bacteria remained on the surfaces. These non-pathogenic biofilms reduced the colonization of the uropathogens by >3.2-log. STATEMENT OF SIGNIFICANCE: In bacterial interference, the non-pathogenic Escherichia coli strains are sluggish to form biofilms on the catheter surfaces, due to rapid removal by urine flow. We have demonstrated a solution to this bottleneck by pre-functionalization of mannosides on the silicone surfaces to promote E. coli biofilm formation. A pre-conjugated high affinity propynylphenyl mannoside ligand tethered to the nanometric amino-terminated poly(amido amine) (PAMAM) dendrimer is used for binding to a major E. coli adhesin FimH. It greatly improves the efficiency for the catheter modification, the non-pathogenic biofilm coverage, as well as the (long-term) stability for prevention of uropathogen infections.

Fabrication and characterization of chitosan-collagen crosslinked membranes for corneal tissue engineering.

This article describes a chitosan-collagen composite membrane as corneal tissue-engineering biomaterials. The membrane was prepared by dissolving the chitosan into collagen with the weight ratio of 0, 15, 30, 45, 60, and 100%, followed by crosslinked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. Mechanical properties, contact angles, and optical transmittance were determined and compared between chitosan membrane and crosslinking composite membrane. As a result, the optical transparency and mechanical strength of the chitosan-collagen membranes were significantly better than that of the sample of chitosan. In addition, in vitro cell culture studies revealed that the collagen has no negative effect on the cell morphology, viability, and proliferation and possess good biocompatibility. Overall, the dendrimer crosslinked chitosan-collagen composite membranes showed promising properties that suggest that these might be suitable biomaterials for corneal tissue-engineering applications.

[Evaluation of biocompatibility of modified gelatin composite membranes for corneal regeneration].

In order to investigate the feasibility of the modified chitosan-gelatin crosslinked membrane (MC-Gel) and chitosan-gelatin crosslinked membrane (CS-Gel) to be a potential biomaterial for corneal regeneration, we evaluated their physicochemical properties and intraocular biocompatibility in this study. White light transmission and permeability of these membranes were detected. Results showed that white light transmission of both membranes was above 90% at 500 nm, which was similar to that of human cornea. The glucose, tryptophan and NaCl permeability of MC-Gel membrane and CS-Gel membrane was better than or similar to those of human cornea. The methylthiazol tetrazolium (MTT) assay was used to assess cell viability and proliferation. Also, interlamellar corneal transplantation was carried out to evaluate ophthalmic biocompatibility of MC-Gel membrane and CS-Gel membrane. Results indicated that MC-Gel membranes could support the proliferation of HCEC and displayed good intraocular biocompatibility when implanted into rabbits. No severe inflammatory reaction occurred after transplantation and the implanted MC-Gel membrane degraded completely 16 weeks post-operation. Due to its good physicochemical properties and biocompatibility, MC-Gel membrane could be a promising candidate material for corneal regeneration.