Synthesis of Chi-sphere silver nanocomposite and nanocomposites of silver, gold, and S@G using a chitosan biopolymer extracted from potato peels and their antimicrobial application

Chitin and chitosan have been proven to have numerous applications in biomedical, pharmaceutical, and industrial fields. In the present study, chitin structural polymer was extracted from potato peel wastes by the use of chemical methods and chitosan biopolymer was generated through the deacetylation of the isolated potato peel chitin. On a dry weight basis, the yield of chitin content of the potato peel wastes is 49.80±1.2 % and the yield of deacetylated potato peel chitin (potato peel chitosan) is 47.60±1.8 %. It was characterized by FTIR and ¹H NMR studies. Consequently, the potato peel chitosan was employed in the synthesis of Chitosan-Silver-Nanocomposite-Sphere (Chi-SNC-Sphere), and other metal nanocomposite of silver (C.g-CSNCs), gold (C.g-CGNCs), and bimetallic (C.g-CS@GNCs). The physicochemical features of the resulting products were characterized using UV-Vis, FT-IR, PXRD, FESEM, TEM, and EDAX. The FESEM unveiled a smooth, spherical, and nonporous surface morphology of the synthesized Chi-SNCs-Sphere, while the remaining three have surfaces that appeared in the form of flakes. As per TEM images, particles were visible in black-spherical (C.g-CSNC) and black-multi-shapes (C.g-CSNC, C.g-CS@GNC) nanostructures. Their sizes were confined within the range of 1–10 nm, with average values of 4.36 nm±0.40–5.85 nm±0.42. On the basis of BET analysis, C.g.CSNCs C.g-CS@GNC and C.g.CGNCs under identical conditions possess the surface area of 69.92 m²g^−1, 52.35 m²g⁻¹, and 49.75 m²g⁻¹ respectively. The nanomaterials were found stable as revealed by the study of zeta potential which is found in the range of +41.3–56.2. The results of the bioassay for antibacterial activity against P. aeruginosa and S. aureus uncovered that the Chi-SNCs-Sphere, C.g-CSNCs, and C.g-CS@GNCs demonstrated superior activities than C.g-CGNCs. According to statistical analysis results of one-way ANOVA of antibacterial results against S. aureus, the P-value F- calculated F-critical was 0.99,1.5 and 3.4 and for P. aeruginosa; P-value, F-calculated, F-critical was 0.80, 0.22 and 5.94 respectively. Minimum inhibitory concentration (MIC) was found most significant for C.g-CSNC (20 µg/mL) due to its higher surface area. These activities could be attributed to the synergistic effect of the metal nanoparticles, potato peel chitosan, and the plant extract that was used for the reduction, stabilization, and biofunctionalization.