Evaluating the photodynamic therapy efficacy using 5-aminolevulinic acid and folic acid-conjugated bismuth oxide nanoparticles on human nasopharyngeal carcinoma cell line.

Selective accumulation of photosensitizers (PSs) into cancerous cells is one of the most important factors affecting photodynamic therapy (PDT) efficacy. 5-Aminolevulinic acid (5-ALA) is precursor of a strong PS, protoporphyrin-IX (Pp-IX); but it has poor permeability in lipophilic membrane of the cells due to its hydrophilic property. Therefore, establishment of an improved delivery strategy could highly affect on treatment outcome. Moreover, folate receptors (FRs) are overexpressed on the surface of many tumor cells. In the present work, targeting ligand folic acid (FA) and 5-ALA conjugated bismuth oxide nanoparticles (FA-5ALA-Bi2O3 NPs) were synthesized; and used in PDT against human nasopharyngeal carcinoma cells (KB cell line). The KB cells incubated with the synthesized NPs for 2 h; then illuminated using a custom-made red light LED lamp at the light dose of 26 J/cm2. MTT and caspase-3 activity assays were performed to evaluate the efficacy of treatment. Results showed that FR targeting ligand enables selective endocytosis of FA-5-ALA-conjugated NPs into KB cells. Improved internalization of 5-ALA into cells decreased the cell viability to about 50%, 65%, and 85% in the groups receiving FA-5ALA-Bi2O3 NPs, 5ALA-Bi2O3 NPs, free 5-ALA and subsequent PDT, respectively. Therefore, FA-5ALA-Bi2O3 NPs can significantly increase the cell killing effect of PDT.