Layer by layer preparation of Fe₃O₄@Cg-DTC/AgNPs as colloidal antimicrobial and anti-biofilm agent

To solve antimicrobial resistance in bacteria, metal nanoparticles (NPs) have gained tremendous attention due to their effectiveness and ease of use. Here, we prepared a core-shell dithiocarbonate carbon functionalized magnetic composite and employed it to support and stabilize the silver nanoparticle (Ag NPs). A chemical reduction method was employed to decorate the Ag NPs over the surface of the magnetic composite. The prepared materials were characterized using FT-IR, XRD, VSM, EDX, SEM, TEM, particle size distribution analysis, and elemental mapping. The results demonstrated that the designed support effectively prevented aggregation of the Ag NPs, ensuring their uniform dispersion throughout the structure. The Ag NPs decorated core-shell material was used as an antimicrobial agent against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The minimum inhibitory concentrations of nanocomposite against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were 0.58 ± 0.38, 1 ± 0, and 4.67 ± 3.06 µg mL^-1, respectively. The results demonstrated that Fe₃O₄@C_g-DTC/AgNPs nanocomposite has a stronger antibacterial effect than the control antibiotic, ciprofloxacin. Regarding biofilm inhibition, the lowest concentration of Fe₃O₄@Cg-DTC/Ag composite required to inhibit biofilm formation in E. coli was 0.0625 µg mL^-1, while the concentrations required for P. aeruginosa and S. aureus were 0.5 and 1 µg mL^-1, respectively. Cytotoxicity assays confirmed that the nanocomposite did not induce toxicity in NIH-3T3 cells. Overall, these results demonstrate the potent antibacterial and anti-biofilm activity of the Fe₃O₄@Cg-DTC/AgNPs nanocomposite while maintaining cytocompatibility.