Gold nanoparticle-doped silk film as biocompatible SERS substrate

In this work, we present a novel rapid method for fabricating biocompatible, biodegradable gold nanoparticle-embedded silk films (AuNP-silk films) that have potential applications in bioengineering and biomedical research. Thin AuNP-silk films are prepared from a AuNP-silk nanocomposite and characterized by scanning electron microscopy (SEM), solid-state nuclear magnetic resonance (NMR) spectroscopy, and UV-visible spectroscopy. Results indicate that the size and distribution of AuNPs can be well controlled in AuNP-silk films, which may have great significance in developing novel biosensors. As a proof of principle, we further demonstrate that the prepared AuNP-silk films can serve as an excellent substrate for surface-enhanced Raman scattering in trace analysis. Moreover, the solid-state NMR results show that the AuNP-silk films possess a structure similar to natural silk, indicating that the fabrication process has little effect on silk protein. Surface plasmon absorption study of AuNPs shows that the optical properties of AuNPs vary when embedded into silk films because of the higher refractive index of silk, which is demonstrated by theoretical simulation.