Antibacterial and anti-tumor migration potency of biosynthesized gold/silver alloy nanoparticles mediated by polydopamine

Abstract

Bacterial infection is a leading cause of death, and has been increasingly associated with cancer development. Thus, developing nanomaterials with both antibacterial and anticancer properties is crucial. Antibiotics are mono-functional and their misuse can lead to the development of antibiotic-resistant bacteria and ecological problems. This study developed the biosynthesis of gold-silver alloy nanoparticles (Au/AgNPs) using polydopamine (PDA) as a multifunctional agent, combining high photothermal efficiency and biocompatibility of gold, along with the antibacterial and anticancer properties of silver, while mitigating its toxicity. These nanoparticles were synthesized and optimized for size, morphology, SPR peak, stability, crystallinity, and photothermal performance, and characterized using SEM, TEM, DLS, UV–Vis spectroscopy, and XRD analysis. In addition, their antibacterial performance and underlying mechanism were studied by MIC determination, inhibition zone test, SEM imaging and RT-PCR analysis. Their anti cancer cell migration effect was also evaluated by a wound healing assay. Major results indicated that optimized Au/AgNPs exhibited quasi-spherical morphology (153.14 ± 3.62 nm) with multiple twinning structures, uniform dispersion, and excellent photothermal performance. XRD analysis showed a lattice constant of 4.7154 Å with 185 nm crystallite size and 0.108 strain value. They exhibited enhanced antibacterial efficacy under NIR irradiation, achieving over 80 % inhibition of both Gram-positive and Gram-negative bacteria at a concentration of 6.04 μg/mL. Simultaneously, they downregulated the expression of PBP2 and MurB by 30–40 %. This outstanding performance stems from the synergistic effect of photothermal/chemotherapy therapy. Moreover, tumor targeting peptide (YL) decorated Au/AgNPs significantly inhibited invasive MDA-MB-231 cell migration, reducing the rate to only 1.12 %. In addition, they demonstrated 3.4 times higher biocompatibility than AgNPs. This dual-action platform merged PTT and metal ion chemotherapy, offering a targeted, biocompatible strategy to concurrently combat antibiotic-resistant infections and cancer metastasis, which is of great significance for the progress of novel antibacterial and antitumor combined therapy drugs.