Activity of wet-spun fibers chemically modified with active biomolecules against Gram-positive and Gram-negative bacteria

Essential oils (EOs), which are complex biomolecules composed of volatile compounds, have emerged as a new strategy to deal with bacterial infections and as a valid alternative to synthetic drugs. Here, we report the modification of biodegradable wet-spun microfibers composed of cellulose acetate (CA) and polycaprolactone (PCL) with EOs, aiming at their localized, controlled release. Cinnamon leaf oil (CLO), cajeput oil (CJO), and clove oil (CO) were selected from a group of 20 EOs according to their minimal inhibitory concentration (MIC) against Staphylococcus aureus (<22.4 mg/mL) and Escherichia coli (<11.2 mg/mL). CA/PCL prepared at 10% and 14%wt in a 3/1 ratio in acetic acid and acetone were processed in the form of microfibers by wet-spinning at an extrusion rate of 0.5 mL/h directly into an ethanol coagulation bath. Microfibers were modified by immersion in ethanol solutions containing EOs at 2xMIC and ampicillin (control antibiotic). Incorporation was confirmed by UV-VIS, FTIR and TGA. After 72h, fibers contained ampicillin at MIC but only 14%, 66% and 76% of MIC for CLO, CO and CJO, respectively. Unloaded and loaded microfibers were characterized as uniform and homogeneous. Data showed that even at small amounts the EO-modified microfibers were effective against the tested bacteria. Considering the amount immobilized, CLO-containing fibers were deemed the most effective from the group, suggesting a superior affinity of the EOs active groups towards the CA/PCL matrix. These results indicate that CA/PCL microfibers loaded with EOs can be easily produced and applied in scaffolds for biomedical applications.