Polyurethane-based leukocyte-inspired biocidal materials.

During the neutrophil respiratory burst myeloperoxidase uses hydrogen peroxide and chloride ion to generate hypochlorite which kills pathogens. Synthetic antimicrobial materials based on this chemistry are described herein. The oxidizing enzymes glucose oxidase (GOX) and horseradish peroxidase (HRP) catalyze two reactions in tandem using glucose, hydrogen peroxide and sodium halide (iodide or bromide). The final product of these two consecutive enzymatic reactions is either iodine or bromine. HRP, acting as haloperoxidase, utilizes the H(2)O(2) generated by GOX to oxidize halide ions into free halogens. Typically, 15 units/ml HRP and 25 units/ml GOX reacted with 0.8mm NaI and 5mm glucose to generate 5-7 ppm free iodine within 30 min. Medical grade polyurethane ChronoFlex AR (CF) was electrospun together with GOX and HRP. The electrospun fibers were collected as a uniform, water-insoluble, flexible elastomeric matrix with an average fiber diameter of 1+/-0.2 microm. Biocidal activity of CF/enzyme fibers resulted in >6-log unit reduction of both Escherichia coli and Staphylococcus aureus challenges. A time-course of biocidal activity displayed a 3-4 log reduction of E. coli and S. aureus within the first 5 min and complete kill (>6 logs) within 15 min. A dose-response study of fiber weight (0.5-30 mg/ml) exhibited complete kill of E. coli (>6 logs) and at least 99.99% S. aureus kill (>4 logs) with as little as 1mg fiber. The fibers were reusable with slightly less activity on the second use and significant activity after continuous soaking in buffer for up to 7 days. Electrospun CF/GOX/HRP fibers adhered to a thin film with embedded NaI and glucose caused a complete kill of E. coli (>7-log units) and MRSA (6-log unit reduction) within 1h at 37 degrees C.

Matrix metalloproteinase-1 treatment of muscle fibrosis.

The onset of scarring after injury may impede the regeneration and functional recovery of skeletal muscle. Matrix metalloproteinase-1 (MMP-1) hydrolyzes type I collagen and thus may improve muscle regeneration by resolving fibrotic tissue. We examined the effect of recombinant human MMP-1 on fibrosis in the lacerated gastrocnemius muscle of NOD/scid mice, allowing treatment potential to be ascertained in isolation from immune response. The efficacy of proMMP-1 and active MMP-1 were compared with or without poly(ethylene glycol) (PEG) modification, which was intended to increase the enzyme's stability. Active MMP-1 was most effective in reducing fibrosis, although treatment with proMMP-1 was also beneficial relative to controls. PEG-modified MMP-1 had minimal activity in vivo, despite retaining activity towards a thioester substrate. Moreover, the modified enzyme was inactivated by trypsin and subtilisin at rates comparable to that of native MMP-1. These results and those of computational structural studies suggest that modification occurs at the C-terminal hemopexin domain of MMP-1, which plays a critical role in collagen turnover. Site-specific modifications that spares catalytic and substrate binding sites while protecting susceptible proteolytic digestion sites may be beneficial. We conclude that active MMP-1 can effectively reduce muscle scarring and that its activity is related to the ability of the enzyme to digest collagen, thereby facilitating remodeling of the injured muscle.