Rapid synthesis of gold nanoparticles using silk fibroin: characterization, antibacterial activity, and anticancer properties

In the present work, well-dispersed gold nanoparticles (AuNPs) were synthesised by the reduction of HAuCl4.xH2O using silk fibroin as a reducing agent. UV-visible spectroscopy confirmed the formation of AuNPs by showing surface plasmon resonance (SPR) at 526–518 nm. The FT-IR study revealed that the hydroxyl groups in the Tyr residue and the carboxyl groups in the Asp and/or Glu residues were the most active functional groups for the conversion of Au ion reduction. The transmission electron microscope (TEM) images showed that the formed nanoparticles were uniformly embedded in the silk fibroin solution. The AuNPs are spherical in shape with smooth edges and around 5–8 nm in diameter. Also, these possess very good stability and dispersity and can be stored for a long period. Further, the X-ray diffraction (XRD) study confirmed the nanocrystalline phase of the gold with cubic crystal structure. The biogenic gold nanoparticles displayed antibacterial activity against Gram-positive and Gram-negative bacteria, and also showed promising anticancer properties.