Modelling antibiotic delivery from functionally graded materials to target biofilm-associated infections

Medical implant-related infections remain notoriously difficult to treat due to the formation of bacterial biofilms. Systemic antibiotic delivery is often ineffective and antibiotic-eluting technologies remain immature in this field, at least in part due to limitations in adequately controlling the antibiotic release rate. A confounding factor is the lack of understanding of the most efficacious antibiotic release profile. In this paper, we introduce a novel theoretical framework that leverages functionally graded materials to achieve tunable, spatially controlled antibiotic delivery - addressing both of these key challenges. Specifically, we develop a new coupled nonlinear partial differential equation model that simultaneously captures antibiotic release from a functionally graded material coating and its transport dynamics within an evolving biofilm. Our results reveal that functionally graded material coatings can outperform homogeneous coatings in sustaining local antibiotic concentrations and suppressing biofilm growth. This study thus establishes functionally graded materials as a promising, previously underexplored design paradigm for infection-resistant medical implants and provides a quantitative basis for optimizing antibiotic release profiles in biofilm-prone environments.