Biosynthesis of Bimetallic Au-Ag Nanoparticles Using Escherichia coli and its Biomedical Applications

Bimetallic nanoparticles act as a multifunctional platform because their properties are dependent on the composition, size, and shape, so their synthetic approaches and technological applications have fascinated many researchers. However, the rigorous reaction conditions and the hazardous chemicals are required during the chemical synthesizing processes. In this study, we develop a biosynthesis method of the bimetallic Au-Ag nanoparticles at room temperature without stabilizers or surfactants. In the solution containing Escherichia coli and Au ions, Au nanoparticles are first obtained upon increasing the pH. After Ag ions join, the core-shell Au-Ag nanoparticles are orderly produced. Transmission electron microscopy (TEM), UV-vis, Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS) are performed to confirm the structure and composition of biosynthetic Au-Ag nanoparticles. Furthermore, we have demonstrated that our bimetallic Au-Ag nanoparticles have greater application prospects in the ultrafast colorimetric detection of H₂O₂, photothermal therapy, and antibiotic therapy in comparison with single Au or Ag nanoparticles. Our bimetallic Au-Ag NPs could achieve the rapid and colorimetric detection of H₂O₂ without 3,3',5,5'-tetramethylbenzidine (TMB) and peroxidase. Moreover, Au-Ag NPs could enhance antibacterial ability but not increase their cytotoxicity, which provides a guarantee for the clinical applications of silver.