Photosensitiser-incorporated microparticles for photodynamic inactivation of bacteria

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2023-04, Vol.241, p.112671-112671, Article 112671
• Main Authors: Moore, Jessica V., Wylie, Matthew P., Andrews, Gavin P., McCoy, Colin P.
• Format: Article
• Language: English
• Subjects: Antimicrobial photodynamic therapy; Ball milling; Disinfection; Light; Photochemotherapy - methods; Photosensitizing Agents - pharmacology; Polymeric microparticles; Reactive Oxygen Species - pharmacology; Staphylococcus aureus; Tolonium Chloride - pharmacology; Toluidine blue O
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2023.112671

Antimicrobial resistance is an ever-growing global concern, making the development of alternative antimicrobial agents and techniques an urgent priority to protect public health. Antimicrobial photodynamic therapy (aPDT) is one such promising alternative, which harnesses the cytotoxic action of reactive oxygen species (ROS) generated upon irradiation of photosensitisers (PSs) with visible light to destroy microorganisms. In this study we report a convenient and facile method to produce highly photoactive antimicrobial microparticles, exhibiting minimal PS leaching, and examine the effect of particle size on antimicrobial activity. A ball milling technique produced a range of sizes of anionic p(HEMA-co-MAA) microparticles, providing large surface areas available for electrostatic attachment of the cationic PS, Toluidine Blue O (TBO). The TBO-incorporated microparticles showed a size-dependent effect on antimicrobial activity, with a decrease in microparticle size resulting in an increase in the bacterial reductions achieved when irradiated with red light. The >6 log10Pseudomonas aeruginosa and Staphylococcus aureus reductions (>99.9999%) achieved within 30 and 60 min, respectively, by TBO-incorporated >90 μm microparticles were attributed to the cytotoxic action of the ROS generated by TBO molecules bound to the microparticles, with no PS leaching from these particles detected over this timeframe. TBO-incorporated microparticles capable of significantly reducing the bioburden of solutions with short durations of low intensity red light irradiation and minimal leaching present an attractive platform for various antimicrobial applications. •A ball milling technique was employed to produce polymeric microparticles.•Cationic TBO was immobilised to anionic microparticles via electrostatic attraction.•TBO-loaded microparticles produced >99.9999% S. aureus and P. aeruginosa reductions.