Eco-friendly antimicrobial nanoparticles of keratin-metal ion complex

Eco-friendly antimicrobial nanoparticles were prepared by adsorbing metal ions to keratin nanoparticles (KNP) isolated from the chicken feather. The mean size of KNP determined by STEM and DLS was 47 ± 15 nm and 80.7 ± 8.3 nm, respectively. The KNP-Ag complex exhibited a larger negative surface charge (−28.2 ± 4.2 mV) than the KNP-Cu (−2.7 ± 0.9 mV) and KNP-Zn (−5.7 ± 1.3 mV) complexes. The FTIR results showed that the interaction of KNP and metal ions was different depending on the type of metal ion. EDX and XPS results revealed the presence of metal ions in KNP-metal ion complexes. Metal ion adsorption and desorption kinetics results showed that the silver binding to KNP was the highest among the metal ions tested, while the release rate was the slowest. The adsorption of cationic metal ions promoted the adhesion of KNP to bacterial cell and enhanced the killing effect for both Gram-positive and Gram-negative bacteria. Metal ion depletion test result revealed that the bactericidal activity of the KNP-metal ion complex was time-dependent due to the desorption of metal ions from the KNP core. The antimicrobial activity of the KNP-metal ion complex was dependent on the type of metal ions. The nanoparticle complex prepared by adsorbing antimicrobial metal ions on biodegradable core materials is likely to be used for the development of eco-friendly antimicrobial nanomaterials.