Fine-tuning the encapsulation of a photosensitizer in nanoparticles reveals the relationship between internal structure and phototherapeutic effects.

Photodynamic therapy (PDT) is a cancer therapy that uses a photosensitizer (PS) in the presence of oxygen molecules. Since singlet oxygen is highly reactive, it is important to deliver it to the target site. Thus, an efficient drug delivery system (DDS) is essential for enhancing the efficacy of such a treatment and protecting against the side effects of PDT. Here, we report on attempts to increase the therapeutic effect of PDT by using a DDS, a lipid nanoparticle (LNP). We prepared a porphyrin analog, rTPA (PS) that was encapsulated in LNPs using a microfluidic device. The findings indicated that the internal structure of the prepared particles changed depending on the amount of rTPA in LNPs. The photoactivity and cell-killing effect of PS in LNPs also changed when the amount of the cargo increased. These results suggest that the internal structure of LNPs is important factors that affect drug efficacy.