Substrate morphology modulates bacteriophage mobility and alters bactericidal potency.

Bacteriophages (phages) are regaining attention as alternatives to antibiotics in the antimicrobial resistance crisis. Although successful cases are widely reported, the influence of physical, abiotic substrate morphology on phage performance remains largely unexamined, despite morphology being an intrinsic topographical feature present at many infection and decontamination sites, such as granular chronic wound beds or porous bone-implant interfaces. In this study, smooth, rough, and porous substrates were physically engineered to investigate the effects of abiotic substrate morphology on phage potency. Profiler and SEM analyses confirmed three distinct morphologies spanning several orders of magnitude in surface roughness. Phage K exhibited a clear hierarchy of bactericidal activity across these morphologies, with the highest activity on smooth substrates, reduced activity on rough substrates, and the lowest activity on porous architectures. Histological analysis and COMSOL simulations revealed that increasing morphological complexity elevates tortuosity and reduces phage accessibility and the probability of encountering pathogens. Together, these findings establish substrate morphology as a critical determinant of phage kinetics and bactericidal potency, relevant both to surface decontamination and, cautiously, to real infection sites such as wound beds and implant-tissue interfaces that inherently possess complex microarchitectures. Incorporating substrate morphology into the design of phage-based applications may improve the predictive accuracy of dosing, interval design, and clinical translation, and deepen understanding of the underlying pharmacology.