Cytocompatible and Antimicrobial Human Hair-Derived Keratin/ N , N , N -Trimethyl Chitosan Polyelectrolyte Multilayers

This study describes the preparation and characterization of keratin-based polyelectrolyte multilayers (PEMs) deposited on oxidized polystyrene (PSox) using the layer-by-layer technique. Supernatant keratin (SK), precipitate keratin (PK), and N,N,N-trimethyl chitosan (TMC) were used as polyelectrolytes to assemble PMEs with 6 and 14 layers, respectively. Atomic force microscopy, water contact angle (WCA), and X-ray photoelectron spectroscopy analyses confirmed the formation of PEMs on PSox. PEM's surface composition and morphology depended on both the keratin fraction (SK and PK) and the number of deposited layers (6 or 14). The resulting PEMs exhibited WCA between 31°-41° and root-mean-square surface roughness of 8-18 nm. The PMEs also remained on the substrate after 24 h of exposure to phosphate-buffered saline (PBS, pH 7.4). Antibacterial assays against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) showed reduced bacterial adhesion and increased bacterial inactivation on the coated PSox. Among the evaluated systems, the 14-layer PEMs made of SK and TMC (SK/TMC)14 exhibited the highest antimicrobial activity against S. aureus, achieving 51% area coverage of dead, adhered cells after 24 h of incubation. No cytotoxic effects toward adipose-derived stem cells (ADSCs) were detected for PMEs based on SK/TMC and PK/TMC. Overall, the results show that keratin/TMC-based PEMs reduce bacterial colonization while maintaining cytocompatibility with mammalian cells, supporting their use as surface coatings for biomedical purposes.