Neat Chitosan Films that Release Polyhexanide for Use in Antibacterial Wound Dressings

Introduction
Chronic, non-healing wounds, including diabetic foot and venous ulcers, affect ~2% of people in developed countries and their prevalence is expected to rise with population ageing and rising obesity and diabetes. As these wounds are frequently infected, antimicrobial dressings (AMDs) are commonly used to aid healing. Here, we produced sustainable antimicrobial films composed solely of chitosan and loaded them with polyhexanide (poly(hexamethylene biguanide); PHMB), an antiseptic used in wound care. The drug loading and sterilization steps were merged to reduce production steps. All assays were conducted on sterilized films, ensuring that sterilization-related effects were reflected in the results. Film performance was benchmarked against a commercial PHMB-releasing AMD.
Methods
Chitosan films were produced by cryogelation without plasticizers or crosslinkers, yielding porous matrices made solely of chitosan. PHMB was loaded by immersing films in PHMB solutions during autoclave sterilization. The films were characterized for dissolution, water uptake, vapor transmission and antioxidant activity. PHMB release kinetics was studied under wound-relevant conditions and benchmarked against a commercial PHMB-releasing AMD assayed in parallel. Antibacterial activity duration and interactions with blood were also evaluated and compared to the commercial AMD.
Results
The films exhibited high porosity, high water uptake, high moisture vapor transmission and high antioxidant activity, along with low dissolution. Higher PHMB loading led to higher PHMB release. Films loaded with a 1 mg/mL PHMB solution exhibited a release profile most similar to a commercial PHMB-releasing AMD assayed in parallel, while releasing more PHMB over a longer period. These films inhibited and killed Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa for at least 24 h. They also promoted blood coagulation and showed hemolysis levels comparable to the commercial AMD.
Conclusions
The results indicate that PHMB‑loaded chitosan cryogel films are promising candidates for use in AMDs.