Optimization of Nasopharyngeal carcinoma (NPC) spheroid formation for 5-ALA PDT study

Significance
Recently, there is an increase in PDT studies using 3D spheroids. However, there is limited information demonstrating the effect of spheroid size on PDT study. This study aims to provide information on the effect of NPC/CNE2 spheroid size on PpIX accumulation and PDT efficacy.
Approach
NPC/CNE2 spheroids were generated with different initial cell densities (5,000-60,000 cells/well). Spheroids’ diameter and morphological characteristics were recorded for 5 days and post-PDT 24-72 hours. The intracellular PpIX accumulation was measured by the Incucyte S3 live-cell analysis system.
Results
Spheroid size increased with initial cell density increased. Spheroids formed within 5,000-20,000 cells were less varied in size and with smooth round edges. The PpIX accumulation was spheroid size-dependent with PpIX accumulation increased in larger spheroids. 5-ALA-PDT inhibited spheroid growth with a decrease in size of periphery compared to the control.
Conclusions
The spheroid size is an important factor affects in vitro PDT study.