Chitosan-based blended films loaded with cajeput oil as enhancers of antibacterial action against <em>Staphylococcus aureus</em> and <em>Pseudomonas aeruginosa</em>

Abstract

Chronic wounds (CW) have numerous entry ways for pathogen invasion and prosperity, damaging host tissue and hindering tissue remodeling. Essential oils (EOs) exert quick and efficient antimicrobial (AM) action, unlikely to induce bacterial resistance. Cajeput oil (CJO) has strong AM properties, namely against Staphylococcus aureus and Pseudomonas aeruginosa, as previously established by the team. Chitosan (CS) is a natural and biodegradable cationic polysaccharide, widely known for its AM features. CS (100-300 kDa; DA of 9.6±1.4%) and PVA (72 kDa, 88% hydrolyzed) films (ratio 30/70; 9%wt) were prepared by solvent casting and phase inversion method. Films thermal stability and chemical composition and reinforce the achievement of blended films. CJO-supplemented films contained a loading amount of 1 and 10wt% in relation to total polymeric mass. Loaded films with 0.89 ± 0.05 and 1.14 ± 0.10 mm in thickness were obtained, respectively, 23 and 57% thicker than the unloaded films. Degree of swelling (%) and porosity also increased, particularly with CJO at 10wt%. Tested AM activity revealed that CS films alone showed an outstanding AM activity against both bacteria, eradicating all P. aeruginosa colony traces within the hour (***p<0.001). Still, loaded CS/PVA films showed improved AM traits, being more efficient than unloaded films right after 2h of contact (*p<0.05 and **p<0.005 for CS/CJO/PVA at 1 and 10% EO, respectively, against S. aureus; *p<0.05 for CS/CJO/PVA at 10% EO, against P. aeruginosa). This study is a first proof of concept that CJO can be dispersed into CS/PVA films and show bactericidal effects, particularly against P. aeruginosa, this way opening new avenues for CW therapeutics.