Biofilm-derived polymer networks constrain immune cell motility through adhesion-mediated physical interactions

Abstract

Understanding how immune cells navigate complex microbial environments requires models that integrate biophysical and biological realism. However, the microscale mechanisms underlying phagocyte migration on pathogenic biofilms remain poorly understood, and there remains a lack of experimental models for study of 3D-interactions between host cells and biofilms. Here, we present a multiscale microfluidic secondary-infection-on-a-chip incorporating human-cell-based model or an ex vivo perfused porcine skin system, to study macrophage migration across bacterial biofilms under controlled flow and spatial confinement. Using Pseudomonas aeruginosa as model pathogen, we demonstrated that biofilm matrix components, specifically the exopolysaccharide Psl, physically impede macrophage motility and directional persistence. Exopolysaccharide-deficient mutants allowed near-normal macrophage migration. Persistent random walk (PRW) simulation modeling recapitulated these motility dynamics, revealing altered migration coefficients within biofilm matrices. Consistent with cell-based model, biofilms impede macrophages on the skin tissue. Hence, our results establish an experimental and modelling framework for studying physical constraints in host-pathogen interactions, providing new insights into mechanical and spatial barriers that shape immune responses to biofilm infections.