Targeted inactivation of bacteriophages by polypyrrole nanoparticles

• Polypyrrole nanoparticles with 1 % carboxyl groups selectively inactivated >95 % of phages (T4, MS2, vB_SauS_CS1). • Minimal impact (<5 %) on host bacteria ( E. coli and S. aureus ) demonstrates high selectivity. • TEM analysis revealed phage inactivation occurs via blocking active sites without structural damage. • Cytotoxicity testing confirmed >90 % viability in fibroblasts, supporting biocompatibility. • These low-cost polymer nanoparticles offer a scalable alternative to metal-based antivirals. Bacteriophage contamination is a persistent issue in various industrial and medical settings, requiring effective yet selective inactivation strategies. The source of phages may be antibiotics, other additives, or raw substrates. There are no effective methods to protect bacterial cultures against such events. This study proposes polypyrrole nanoparticles functionalized with 1 % carboxyl groups (P(Py:PyCOOH) 100:1 NPs) as a targeted solution for phage inactivation. The P(Py:PyCOOH) 100:1 nanoparticles exhibit selective antiviral properties, with above 95 % inactivation of T4, MS2, and vB_SauS_CS1 phages, while maintaining less than 5 % inactivation of their corresponding bacterial hosts ( E. coli and S. aureus ). TEM imaging reveals no significant morphological changes in the phages post-treatment, suggesting that inactivation occurs through blocking active sites rather than structural damage. Cytotoxicity studies demonstrate > 90 % viability of 3 T3 NIH fibroblast cells upon exposure to P(Py:PyCOOH) 100:1 nanoparticles, confirming their biocompatibility and safety for potential biomedical applications. Because some phages serve as surrogates for pathogenic viruses, the presented results are the next step towards selective and safe antivirals acting directly on virions.