Biocompatible and biomimetic keratin capped Au nanoparticles enable the inactivation of mesophilic bacteria via photo-thermal therapy

We report on the synthesis, characterization, and application of biomimetic, spherical Au nanoparticles (AuNPs) coated with keratin (Ker-AuNPs). They are characterized in terms of morphological, spectral, and thermo-optical properties. Besides their excellent colloidal stability, Ker-AuNPs exhibit excellent biocompatibility. The latter is verified by performing viability assay experiments of a strain of Escherichia coli (E. coli) in the presence of Ker-AuNPs as a function of the incubation time. Ker-AuNPs do not affect the E. coli viability and proliferation, even at the highest concentration tested (C = 5.83*10−5 M). Photo-thermal assisted viability experiments are performed by setting the starting temperature at 37 °C, mimicking the normal human body temperature condition. They evidence the capability of the Ker-AuNPs to generate a temperature up to about 73 °C (an increase of 36 °C), thus reducing the viability of bacterial cells 3 order of magnitudes. We also conducted a theoretical analysis with an ad-hoc model that evidences an excellent agreement between theory and experiments. Ker-AuNPs represent a new generation of multifunctional nanotherapeutics, and they constitute a new opportunity in drug-free and minimally invasive biomedical applications.