Effective Photothermal Killing of Pathogenic Bacteria by Using Spatially Tunable Colloidal Gels with Nano-Localized Heating Sources

• Published in: Advanced functional materials 2015-02, Vol.25 (5), p.721-728
• Main Authors: Hsiao, Chun-Wen, Chen, Hsin-Lung, Liao, Zi-Xian, Sureshbabu, Radhakrishnan, Hsiao, Hsu-Chan, Lin, Shu-Jyuan, Chang, Yen, Sung, Hsing-Wen
• Format: Article
• Language: English
• Subjects: Bacteria; bactericidal effect; Colloids; Damage; Derivatives; Gels; Heating; localized heating; Mathematical models; Nanostructure; pH-responsive micellar hydrogel; photothermal agent; self-doped conducting polymer
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201403478

Alternative approaches to treating subcutaneous abscesses—especially those associated with antibiotic‐resistant pathogenic bacterial strains—that eliminate the need for antibiotics are urgently needed. This work descibes a chitosan (CS) derivative with self‐doped polyaniline (PANI) side chains that can self‐assemble into micelles in an aqueous environment and be transformed into colloidal gels in a process that is driven by a local increase in pH. These self‐doped PANI micelles can be utilized as nano‐localized heat sources, remotely controllable using near‐infrared (NIR) light. To test the in vivo efficacy of the CS derivative as a photothermal agent, an aqueous solution thereof is directly injected at the site of infected abscesses in a mouse model. The injected polymer solution eventually becomes distributed over the acidic abscesses, forming colloidal gels when it meets the boundaries of healthy tissues. After treatment with an 808 nm laser, the colloidal gels convert NIR light into heat, causing the thermal lysis of bacteria and repairing the infected wound without leaving residual implanted materials. This approach has marked potential because it can provide colloidal gels with tunable spatial stability, limiting localized heating to the infected sites, and reducing thermal damage to the surrounding healthy tissues. An injected polymer solution exhibits a rapid nanostructure transformation over a narrow range of pH values and forms a colloidal gel at the site of the abscess, providing tunable spatial stabilization. The formed colloidal gel converts near‐infrared (NIR) light energy into heat and causes thermal lysis of the bacteria, reducing thermal damage to the surrounding tissues.