Photodynamic Therapy as a Supportive Approach for Treating Bacterial Pneumonia – An In Vivo Study

Respiratory infections, particularly pneumonia, cause around 3.5 million deaths annually. Bacterial pneumonia inflames the alveoli, leading to fluid accumulation and breathing difficulties. With rising antimicrobial resistance, Antimicrobial Photodynamic Therapy (aPDT) offers a promising alternative, though its effectiveness is hindered by lung surfactant (LS) trapping photosensitizers (PSs). This study explored nebulization for PS delivery, testing Methylene Blue (MB) and Indocyanine Green (ICG) with the polymer Gantrez AN-139. The most effective formulation was ICG (200 µM) with Gantrez AN-139 (4% w/v), showing spectral broadening and red-shift post-nebulization. Fluorescence emission decreased significantly, while size and scattering analyses indicated a high dispersion index. In vivo, a 120 J/cm² light dose reduced bacterial counts by 2.5 logs. While results are promising, challenges in administration and variability remain. Refining dosage precision and delivery methods is crucial to optimizing therapeutic efficacy.