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

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.

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.

We assessed the therapeutic potential of this formulation in a murine pneumonia model using pulmonary delivery followed by 808 nm infrared irradiation.

Nebulization of $200\mu M$ ICG with 4% Gantrez AN-139 and irradiation at $120J/{\mathrm{cm}}^2$ yielded the best results, reducing bacterial load by up to $3{\log }_{10}$ and improving survival to 80%, compared with 40% in controls.

These findings validate the formulation and the procedure for further animal studies.