(536i) A Starch-Mediated Synthesis of Bimetallic Silver/Gold Nanoparticles with Different Chemical Composition As Antimicrobial and Anticancer Agents

Nanomedicine is a branch of nanotechnology that is concerned with the synthesis, characterization and application of nanomaterials in the field of medicine. In recent years, the application of noble metal nanoparticles (NPs) in nanomedicine has received considerable attention due to their promising use as anticancer and antibacterial treatment agents.

The synthesis of noble metal NP systems has been reported through a variety of physical, chemical and biological methods. Out of these approaches, the wet chemical reduction method is one of the most applied, due to precise compositional, size and crystallographic control of the resulting nanomaterials. In general, this method consists of a metal salt precursor, reducing and stabilizing agents and a dispersion medium. Some examples of common chemical compounds include N, N- dimethylformamide (DMF) and sodium borohydride (NaBH4) as reducing agents, cetyltrimethylammonium bromide (CTAB) as capping agents, and toluene or chloroform as solvent. Although the use of these compounds often yields better control of the final product, they may leave toxic contaminants. For this reason, their use in medical applications is potentially dangerous due to toxic effects on the environment and biological systems. An alternative to the usage of toxic reagents is the employ of plant extracts, unfortunately, this route requires a complex purification process and, in many cases, there is a necessity to use toxic solvents in the determination of the active molecules that play the role as reducing and capping agents of the NPs.

Therefore, a simpler eco-friendly method has been proposed for the synthesis of colloidal noble metal NPs, in which biocompatible starch acts as both the capping and reducing agent and water as the solvent. Starch is a highly abundant biopolymer found in nature, especially in food products such as rice, potato and nuts. This biopolymer can act as a reducing agent in the presence of sodium hydroxide (NaOH), which dissociates in water and the hydroxyl groups (OH^-) react with starch to release electrons that reduce Ag+ to metallic silver. The capping properties of starch are given by its hydroxyl groups, which stabilize the AgNPs through inter- and intra-molecular hydrogen bonding.

In the present work, we report a simple, environmentally friendly, cost-effective and highly reproducible green synthetic approach for the production of colloidal AuNPs, AgNPs and bimetallic Ag/AuNPs with different atomic composition using potato starch as the capping and reducing agent and water as the dispersion medium. The NPs were characterized for their optical properties, colloid stability, particle size, morphology and composition using ultraviolet (UV)–visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), ζ-potential, energy-dispersive X-ray spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS). Antimicrobial studies with commercially available antibiotic-resistant bacterial strains (MRSA and multidrug-resistant [MDR] Escherichia coli) as well as cytocompatibility and anticancer studies with human dermal fibroblast (HDF) and human melanoma cells, respectively, were completed in order to elucidate the biomedical applications of the novel green-synthesized noble metal NPs.