  Antimicrobial biomaterials are critical to aid in the regeneration of oral
soft tissue and prevent or treat localised bacterial infections. With the
rising trend in antibiotic resistance, there is a pressing clinical need for
new antimicrobial chemistries and biomaterial design approaches enabling
on-demand activation of antibiotic-free antimicrobial functionality following
an infection that are environment-friendly, flexible and commercially-viable.
This study explores the feasibility of integrating a bioresorbable electrospun
polymer scaffold with localised antimicrobial photodynamic therapy (aPDT)
capability. To enable aPDT, we encapsulated a photosensitiser (PS) in polyester
fibres in the PS inert state, so that the antibacterial function would be
activated on-demand via a visible light source. Fibrous scaffolds were
successfully electrospun from FDA-approved polyesters, either
poly(epsilon-caprolactone (PCL) or poly[(rac-lactide)-co-glycolide] (PLGA) with
encapsulated PS (either methylene blue (MB) or erythrosin B (ER)). The
electrospun fibres achieved an ~100 wt.% loading efficiency of PS, which
significantly increased their tensile modulus and reduced their average fibre
diameter and pore size with respect to PS-free controls. In vitro, PS release
varied between a burst release profile to limited release within 100 hours
depending on the selected scaffold formulation. Exposure of PS-encapsulated PCL
fibres to visible light successfully led to at least a 1 log reduction in E.
coli viability after 60 minutes of light exposure whereas PS-free electrospun
controls did not inactive microbes. This study successfully demonstrates the
significant potential of PS-encapsulated electrospun fibres as photodynamically
active biomaterial for antibiotic-free infection control.
