Extruded polysaccharide/protein matrix from Arthrospira platensis cultures mediated silver nanoparticles biosynthesis and capping

Abstract

Herein, Silver nanoparticles (AgNPs) have been synthesized and capped using secreted polysaccharide-protein matrix (EPS) from Arthrospira platensis cultures (A-EPS) and compared with EPS extracted from 1.0 K Gy gamma-irradiated A. platensis cultures (IA-EPS). Gamma irradiation enhanced EPS secretion and modified its biochemical composition. A. platensis cultures have been exposed to two acute gamma irradiation doses of 1.0–2.0 K Gy, EPS secretion was scaled up in response to gamma irradiation from 0.559 g L−1 at non-irradiated culture to 0.752, 0.690 g L−1 at 1.0–2.0 K Gy, respectively. Saccharide-protein nature of EPSs was confirmed via chemical, UV Visible spectrophotometer, and Fourier-transform infrared spectroscopy (FT-IR), revealed an increment of protein content in (IA-EPS). Hetero-polymeric constituents were elucidated using HPLC analysis which revealed seven monomers in the saccharide portion of (IA-EPS). AgNP biosynthesis was fabricated in alkaline medium whereas IA-EPS-mediated AgNPs (IEPS-AgNPs) exhibited a stronger UV absorbance than A-EPS-mediated AgNPs (EPS-AgNPs) at pH 9.0 and 2.0 mg L−1. Synthesized AgNPs displayed the difference in coating nature and its aggregation under Transmission Electron Microscope (TEM) whereas (IEPS-AgNPs) displayed mono-dispersed nanoparticles capped by protein layers meanwhile (EPS-AgNPs) exhibited poly-dispersed ones capped with a faint sheath of EPS. FT-IR analysis illustrated the capping mechanism for both EPS-AgNPs and IEPS-AgNPs.