Abstract
Photodynamic therapy (PDT) is phototherapeutic modality used in the treatment
of neoplastic and non-neoplastic diseases. The photochemical interaction of light,
photosensitizer (PS) and molecular oxygen produces singlet oxygen which induces cell
death. Zinc sulfophthalocyanine (ZnPcSmix) has been shown to be effective in A549
monolayers, multicellular tumor spheroids (MCTSs) (250 μm) and not on MCTSs with
a size of 500 μm. A549 cells used in this study were grown as MCTSs to a size of 500 μm
in order to determine their susceptibility to PDT. ZnPcSmix distribution in MCTSs and
nuclear morphology was determined using a fluorescent microscope. Changes in cellular
responses were evaluated using cell morphology, viability, proliferation, cytotoxicity, cell
death analysis and mitochondrial membrane potential. Untreated MCTSs, showed no
changes in cellular morphology, proliferation, cytotoxicity and nuclear morphology.
Photoactivated ZnPcSmix also showed no changes in cellular morphology and nuclear
morphology. However, photoactivated ZnPcSmix resulted in a significant dose dependant
decrease in viability and proliferation as well as an increase in cell membrane damage
in MCTSs over time. ZnPcSmix photosensitization induces apoptotic cell death in MCTSs
with a size of 500 μm and more resistantance when compared to monolayer cells and MCTSs