Polymer dressings with encapsulated thrombin or synthetic peptides which can mimic thrombin action are employed for wound healing. Paper describes the method for preparation of these hydrogel composites of PVCL-CaAlg [poly(N-vinyl caprolactam-calcium alginate). The effect of encapsulated thrombin/peptides on tissue repair process have beet investigatat in vivo experiments using a mouse model of wound healing. The developed dressings accelerated wound healing: thascan be used as a basis for creation of novel formulations with controlled drug release for wound therapy.

To accelerate the healing processes in wound repair, attempts have been repeatedly made to use growth factors including thrombin and its peptide fragments. Unfortunately, the employment of thrombin is limited because of its high liability and pro-inflammatory actions at high concentrations. Some cellular effects of thrombin in wound healing are mediated by the activation of protease activated receptor-1 (PAR-1). The thrombin receptor agonist peptide (TRAP:SFLLRN) activates this receptor and mimics the effects of thrombin, but TRAP is a relatively weak agonist. We speculated that the encapsulated peptide may be more effective for PAR-1 activation than nonimmobilized peptide and developed a novel method for TRAP encapsulation in hydrogel films based on natural and synthetic polymers. The effects of an encapsulated TRAP in composite poly(N-vinyl caprolactam)-calcium alginate (PVCL) hydrogel films were investigated in a mouse model of wound healing. On day 7 the wound sizes decreased by about 60% under TRAP-chitosan-containing PVCL films, as compared with control films without TRAP. In the case of TRAP-polylysine-containing films no significant decrease in wound sizes was found. The fibroblast/macrophage ratio increased under TRAP-containing films on day 3 and on day 7. The number of proliferating fibroblasts increased to 150% under TRAP-chitosan films on day 7 as compared with control films. The number of [ 3 H]-thymidine labeled endothelial and epithelial cells in granulation tissues was also enhanced. Thus, the immobilized TRAP to PVCL-chitosan hydrogel films were found to promote wound healing following the stimulation of fibroblast and epithelial cell proliferation and neovascularization. Furthermore, TRAP was shown to inhibit the secretion of the inflammatory mediator PAF from stimulated rat peritoneal mast cells due to augmentation of NO release from the mast cells. The encapsulated TRAP is suggested to accelerate wound healing due to the anti-inflammatory effects and earlier development of the proliferative phase of wound healing.

Chemico-enzymatic methods are a promising approach to obtain various biologically active compounds, including enantiomerically pure substances. Entrapment in gels is one of the most convenient methods to stabilize enzymes for their application in water/organic media. In this study, proteases (trypsin and chymotrypsin) were entrapped into a composite poly (N-vinyl caprolactam)-calcium alginate (PVCL-CaAlg) hydrogel, and properties of the biocatalysts obtained were studied. Both entrapped trypsin and α-chymotrypsin retained high activity (up to 85% of the initial value for the immobilized trypsin) and displayed high storage stability. The entrapped proteases were active over broad temperature ranges, and their heat tolerance was approximately 20-25°C higher than that of the soluble enzymes. The dependence of the activities of the soluble and entrapped enzymes on the organic solvent concentration was studied. It appeared that gel entrapment provided retention of enzyme activity in the media with high concentrations of organic solvents (up to 0.5% water content) and ensured high operational stability of α-chymotrypsin in a cyclic process (270 h in total). The entrapped α-chymotrypsin was used as a biocatalyst for obtaining optically pure L-phenylalanine (e.e. 87.8%) by enantioselective hydrolysis of Schiff's base of amino acid ethyl ester in an acetonitrile/water system.