Drug delivery into the malignant cell is a basic requirement for effectiveness of photosensitizing systems for photodynamic therapy (PDT). For anticancer tumoricidal drugs, e.g., 5-aminolevulinic acid (ALA), zinc oxide (ZnO) nanoparticles (NPs) are used as efficient intracellular photosensitizer carriers. Apoptotic effect of tumoricidal drugs (ALA and Photofrin®) is studied in HepG2 (Hepatucellular carcinoma) cells in the presence and absence of ZnO NPs using confocal microscopy as well as Neutral Red Assay (NRA). In dark, ZnO NPs conjugated with ALA or Photofrin® has been found to have a remarkable fluorescence in Hepatucellular carcinoma (HepG2) cells. This fact illustrates the great potential of ZnO NPs as biomarker in relevant clinical and biomedical applications.