Polyurethane-based leukocyte-inspired biocidal materials

Abstract

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 2O 2 generated by GOX to oxidize halide ions into free halogens. Typically, 15 units/ml HRP and 25 units/ml GOX reacted with 0.8 m m NaI and 5 m m 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 μm. 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 1 mg 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 1 h at 37 °C.