Photodynamic diagnosis (PDD) can improve diagnostic accuracy by using PDD agents such as 5-aminolevulinic acid (ALA). However, the weakness and photobleaching of fluorescence of PDD agents may lead to insufficient fluorescence visibility for the detection of cancer during resection operations. We focused on the "fluorescence enhancement effect" resulting from the addition of polyethylene glycol-modified titanium dioxide nanoparticles (TiO2-PEG NPs) to address these problems. The results showed that the combined administration of TiO2-PEG NPs and ALA could enhance and prolong fluorescence in bladder cancer cells, similar to in the mixture alone. It was suggested that the fluorescence enhancement was related to the accumulation of TiO2-PEG NPs in cells via endocytosis, causing the light scattering and enhancement of fluorescence. This fluorescence enhancement effect could be applicable for PDD.
Keywords: cellular uptake; fluorescence enhancement effect; photodynamic diagnosis; polyethylene glycol-modified titanium dioxide nanoparticles.