Extracorporeal near-infrared-activated antimicrobial photodynamic therapy for pneumonia using an ICG-polymer formulation.

SIGNIFICANCE: Pneumonia remains a global health challenge, exacerbated by antimicrobial resistance, which limits the effectiveness of conventional treatments. Antimicrobial photodynamic therapy (aPDT) has emerged as a promising alternative for lower respiratory infections; however, its in vivo performance is hindered by lung surfactant, which traps photosensitizers and reduces their ability to reach bacterial targets. AIM: To address this limitation, recent studies demonstrated that combining indocyanine green (ICG) with the polymer Gantrez AN-139 enhances photodynamic activity even in the presence of lung surfactants. APPROACH: We assessed the therapeutic potential of this formulation in a murine pneumonia model using pulmonary delivery followed by 808 nm infrared irradiation. RESULTS: Nebulization of 200    μ M ICG with 4% Gantrez AN-139 and irradiation at 120    J / cm 2 yielded the best results, reducing bacterial load by up to 3   log 10 and improving survival to 80%, compared with 40% in controls. CONCLUSION: These findings validate the formulation and the procedure for further animal studies.