Bionanocomposites are formed through the electrostatic interactions of exfoliated clay nanoparticles initially dispersed in an aqueous solution with chitosan macromolecules that are gradually charged in the course of a progressive pH decrease by chemical acidulating agent to exclude the phase separation.Chitosan is a product of the de-acetylation of chitin, which is the second abundant organic compound on Earth after cellulose. Although this polysaccharide presents a huge renewal resource of biomass, of which annual production in nature reaches 100 billion tonnes, it is still almost unutilized, being a biopolymer of significant versatility and promise. 1-3 Clay is a natural mineral that is widely used for making various materials and in many industrial processes. Clay nanoparticles of smectite-type, such as montmorillonite and saponite, dispersed into polymers remarkably improve their material properties including strong reinforcing, increased heat resistance, decreased gas permeability and flammability. 4,5 Their effect is observed after exfoliation into
The present study reports a green chemistry approach for the rapid and easy biological synthesis of silver (Ag), gold (Au), and bimetallic Ag/Au nanoparticles using the callus extract of Lithospermum erythrorhizon as a reducing and capping agent. The biosynthesized nanoparticles were characterized with ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD) analysis, and transmission electron microscopy (TEM). Our results showed the formation of crystalline metal nanostructures of both spherical and non-spherical shape. Energy dispersive X-ray (EDX) spectroscopy showed the characteristic peaks in the silver and gold regions, confirming the presence of the corresponding elements in the monometallic particles and both elements in the bimetallic particles. Fourier-transform infrared (FTIR) spectroscopy affirmed the role of polysaccharides and polyphenols of the L. erythrorhizon extract as the major reducing and capping agents for metal ions. In addition, our results showed that the polysaccharide sample and the fraction containing secondary metabolites isolated from L. erythrorhizon were both able to produce large amounts of metallic nanoparticles. The biosynthesized nanoparticles demonstrated cytotoxicity against mouse neuroblastoma and embryonic fibroblast cells, which was considerably higher for Ag nanoparticles and for bimetallic Ag/Au nanoparticles containing a higher molar ratio of silver. However, fibroblast migration was not significantly affected by any of the nanoparticles tested. The obtained results provide a new example of the safe biological production of metallic nanoparticles, but further study is required to uncover the mechanism of their toxicity so that the biomedical potency can be assessed.
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