Engineering hydrophobic and electrostatic interactions for selective inactivation of bacteriophages by mixed-ligand nanoparticles

Bacteriophage contamination poses significant challenges in bacteria-based industries, disrupting processes that rely on bacterial metabolism, such as insulin production using Escherichia coli. This study introduces mixed-ligand nanoparticles (MLNPs) as a novel solution for selective phage inactivation while preserving bacterial viability. By controlling the ratios of positively charged ((11-Mercaptoundecyl)-N,N,N-trimethylammonium cation, TMA), negatively charged (mercaptoundecanate anion, MUA), and hydrophobic (dodecane-1-thiol, DDT) ligands, MLNPs leverage tailored multivalent interactions to disrupt bacteriophage functions. The optimum MLNP formulation (60:20:18 ratio of TMA:MUA:DDT) achieved complete phage inactivation (7-log reduction) within 9 hours at 25 °C, a significant improvement over traditional methods that require harsh conditions, elevated temperatures, and/or extended durations. Our results demonstrate that hydrophobic ligands enhance phage inactivation while maintaining bacterial viability, with survival rates exceeding 90%. The MLNPs were tested against diverse bacteriophages, including MS2, M13, Qβ, LR1_PA01, and vB_SauS_CS1, achieving broad-spectrum efficacy without significant harm to host bacteria. Furthermore, cytotoxicity tests on mammalian 3T3 NIH fibroblast cells confirmed the high biocompatibility of MLNPs, with cell viability exceeding 90% at effective concentrations. This study highlights the potential of MLNPs as a selective and cost-effective tool for managing bacteriophage contamination, offering advantages for industrial and medical applications by ensuring bacterial productivity while mitigating phage-induced disruptions.