Control of multi-drug-resistant pathogens with non-thermal-plasma-treated alginate wound dressing

Non-thermal dielectric-barrier discharge plasma (non-thermal plasma) is being investigated for use in wound healing. Alginate gel, already in clinical use, is non-toxic but has no meaningful antimicrobial property. This study reports that a non-thermal-plasma-treated alginate wound dressing has strong antimicrobial properties.

Alginate gel was treated with non-thermal plasma in room air and inoculated with bacterial pathogens. At 15 min after this, bacterial cell viability was determined by colony assay or 2,3-bis-(2-methoxy-4- nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay. The anti-biofilm efficacy of the non-thermal-plasma-treated alginate gel was investigated and the treated gel was tested against vascular endothelial cells for a cytotoxic effect. The proliferation and migration of bacterial cells before and after exposure to the treated gel were investigated with an in vitro wound testing assay. Scanning electron microscopy was used to observe changes in the gel surface associated with exposure to bacterial pathogens. The treated gel was tested against Acinetobacter baumannii, Escherichia coli, Staphylococcus aureus, S. epidermidis, Candida albicans, and C. glabrata as representative pathogens (at 10(6)-10(9) colony-forming units [CFU]/mL), and the thickness of a plasma-treated gel dressing and distance between a glass dielectric-barrier discharge plasma probe and the gel surface were kept constant.

Non-thermal-plasma-treated alginate gel exhibited a strong biocidal property and inactivated all of the pathogens included in the study at counts of 10(8) CFU/mL and within 15 sec of treatment. The treated gel inactivated 10(9) CFU/mL of the organisms within 1 min, and 3 min of exposure to the treated gel inactivated pathogens embedded in biofilms. The plasma-treated gel showed no significant cytotoxicity, and endothelial cells exposed to the treated gel proliferated and migrated well across a wound area over a period of time. Dressings made with the treated gel retained their biocidal effects for about a month. Scanning electron microscopy showed no damage to the surfaces of treated gels, but damage to the bacterial pathogens on plasma exposure.

A non-thermal-plasma-treated alginate gel dressing has the clinical potential to decontaminate wounds, prevent surgical site infection, and promote wound healing.