Amongst different living organisms studied as potential candidates for the green synthesis of copper nanoparticles, algal biomass is presented as a novel and easy-to-handle method. However, the role of specific biomolecules and their contribution as reductant and capping agents has not yet been described. This contribution reports a green synthesis method to obtain copper oxide nanoparticles (CuO-NPs) using separated protein fractions from an aqueous extract of brown algae Macrocystis pyrifera through size exclusion chromatography (HPLC-SEC). Proteins were detected by a UV/VIS diode array, time-based fraction collection was carried out, and each collected fraction was used to evaluate the synthesis of CuO-NPs. The characterization of CuO-NPs was evaluated by Dynamic Light Scattering (DLS), Z-potential, Fourier Transform Infrared (FTIR), Transmission Electron Microscope (TEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) detector. Low Molecular Weight (LMW) and High Molecular Weight (HMW) protein fractions were able to synthesize spherical CuO-NPs. TEM images showed that the metallic core present in the observed samples ranged from 2 to 50 nm in diameter, with spherical nanostructures present in all containing protein samples. FTIR measurements showed functional groups from proteins having a pivotal role in the reduction and stabilization of the nanoparticles. The highly negative zeta potential average values from obtained nanoparticles suggest high stability, expanding the range of possible applications. This facile and novel protein-assisted method for the green synthesis of CuO-NPs may also provide a suitable tool to synthesize other nanoparticles that have different application areas.

BACKGROUND: A biomimetic method was developed for the synthesis of silver nanoparticles (AgNPs). Synthetic chemical compounds were used according to the metabolites present in the fungal extracts for the synthesis of AgNPs. The main objective of this study was to find a simple and effective synthesis method without the presence of a living organism. METHODOLOGY: A central composite design combined with response surface methodology was used to optimize the necessary metabolite concentrations (flavin adenine dinucleotide (FAD), hydroquinone (HQ), and L-cysteine (L-cys)) for the synthesis of AgNPs. The design was assessed based on the size distribution and zeta potential of the nanoparticles. In addition, the antibacterial activity of the AgNPs against Escherichia coli, Staphylococcus aureus, Serratia marcescens and Salmonella enterica was tested. RESULTS:The results demonstrated that AgNO 3 (2 mmol L −1 ), HQ (20 mmol L −1 ), L-cys (20 mmol L −1 ) and FAD (50.5 nmol L −1 ) at pH 8.4 were the optimal reaction parameters. The characterization allowed the determination of quasi-spherical AgNPs with an average hydrodynamic size of 101 nm, a zeta potential of −24 mV and the presence of elemental silver (Ag 0 ) in their composition. Fourier transform infrared spectroscopy showed silver and L-cys interactions, supporting the role of L-cys as a coating agent. The antibacterial activity showed that AgNPs displayed a minimum inhibitory concentration of 20-30 ∼g mL −1 and a minimum bactericidal concentration of 30-40 ∼g mL −1 .CONCLUSIONS: This study demonstrates the feasibility of the reduction of Ag + to Ag 0 using synthetic metabolites, which mimic the reduction and synthesis of fungal biomass. Therefore, it represents a new biocompatible, eco-friendly and fast method to produce AgNPs.