This work presents a simple method for the green synthesis of silver nanoparticles (AgNPs) using as reducing and stabilizing agent a polysaccharide extracted from red algae Gracilaria birdiae present in the coast of Piauí. The AgNPS were prepared using three polysaccharide concentrations (0.02, 0.03 and 0.05% v/v) and two pHs (10 and 11) at stirring for 30min at 90°C. The formation of silver nanoparticles was monitored by measurements of UV–vis and FTIR and characterized by size and zeta potential measurements using DLS and morphologically by TEM. The UV–vis absorption spectrum showed the surface plasmon peak at 410nm, which is characteristic peak of silver nanoparticles. The functional biomolecules present in the polysaccharide and the interaction between the nanoparticles were identified by the Fourier transform infrared spectroscopy (FTIR) analysis. The stability of the synthesized silver nanoparticles was analyzed during four months and no significant agglomeration was observed. The hydrodynamic diameter of the AgNPs varied between 20.2nm and 94.9nm. The AgNPs were tested for antimicrobial activity using Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) and all samples showed antimicrobial activity against E. coli. Using an environment-friendly, the AgNPs were synthesized in a simple, rapid and one-step process using natural sources as red algae with favorable characteristics such as spherical shape, small size and zeta potential negative. The results suggest that the polysaccharide mediated synthesized silver nanoparticles could be used as a model for future projects of nano-medicines or drug delivery systems

Chemical modifications to cashew gum (CG) structure have been previously reported to obtain new physicochemical characteristics, however until now there were no reports of modifications by introduction of new functional groups to add cationic character. This study presents a quaternization route for CG using a quaternary ammonium reagent. The chemical features of the quaternized cashew gum derivatives (QCG) were analyzed by: FTIR, elemental analysis, degree of substitution, Zeta potential, 1H NMR and 1H-13C correlation (HSQC). QCG were evaluated for their anti-staphylococcal activity by determining minimum inhibitory and bactericidal concentrations against pathogenic Staphylococcus spp. and by imaging using atomic force microscopy. Moreover, the mammalian cell biocompatibility were also assessed through hemolytic and cell toxicity assays. QCG presented promising antimicrobial activity against methicillin-resistant S. aureus and biocompatibility on tested cells. These results show that QCG could be a promising tool in the development of biomaterials with an anti-septic action.