Solubilizer-Assisted Formulation of Porphyrin-Containing Lipid Nanoparticles for Photodynamic Applications

Hydrophobic porphyrin photosensitizers can lose photodynamic activity when densely loaded into nanoparticles because intermolecular aggregation promotes excited-state quenching. We investigated whether CAOM, a cinnamic-acid-derived oily solubilizer, could regulate the intraparticle organization of the π-extended porphyrin photosensitizer rTPA in MITO-Porter nanoparticles. Low-loading MITO-Porter (Low-MP), high-loading MITO-Porter (High-MP), and CAOM-containing High-MP (High-MP+CAOM) were prepared using the iLiNP microfluidic device. At an equivalent rTPA concentration, High-MP generated substantially less singlet oxygen than Low-MP, whereas High-MP+CAOM showed singlet oxygen generation comparable to Low-MP. High-MP+CAOM was internalized by HeLa cells and was observed in proximity to mitochondria. At comparable total lipid concentrations calculated from formulation inputs, High-MP+CAOM produced the greatest light-dependent reduction in cell viability, while dark toxicity remained limited under the tested conditions. Fluorescence spectroscopy was consistent with attenuated aggregation-caused quenching (ACQ), while cryo-transmission electron microscopy showed a more homogeneous intraparticle morphology after CAOM incorporation. These findings suggest that CAOM incorporation may support the photodynamic performance of porphyrin-containing lipid formulations under the tested conditions.