Screening of two-photon activated photodynamic therapy sensitizers using a 3D osteosarcoma model.

Photodynamic therapy (PDT) involves a photosensitizing agent activated with light to induce cell death. Two-photon excited PDT (TPE-PDT) offers numerous benefits compared to traditional one-photon induced PDT, including an increased penetration depth and precision. However, the in vitro profiling and comparison of two-photon photosensitizers (PS) are still troublesome. Herein, we report the development of an in vitro screening platform of TPE-PS using a 3D osteosarcoma cell culture. The platform was tested using three different two-photon (2P) active compounds - a 2P sensitizer P2CK, a fluorescent dye Eosin Y, and a porphyrin derivative (TPP). Their 2P absorption cross-sections (σ2PA) were characterised using a fully automated z-scan setup. TPP exhibited a remarkably high σ2PA at 720 nm (8865 GM) and P2CK presented a high absorption at 850 nm (405 GM), while Eosin Y had the lowest 2P absorption at the studied wavelengths (<100 GM). The cellular uptake of PS visualized using confocal laser scanning microscopy showed that both TPP and P2CK were internalized by the cells, while Eosin Y stayed mainly in the surrounding media. The efficiency of the former two TPE-PS was quantified using the PrestoBlue metabolic assay, showing a significant reduction in cell viability after two-photon irradiation. The possibility of damage localization was demonstrated using a co-culture of adipose derived stem cells together with osteosarcoma spheroids showing no signs of damage to the surrounding healthy cells after TPE-PDT.

Highly selective and sensitive macrocycle-based dinuclear foldamer for fluorometric and colorimetric sensing of citrate in water.

The selective detection of citrate anions is essential for various biological functions in living systems. A quantitative assessment of citrate is required for the diagnosis of various diseases in the human body; however, it is extremely challenging to develop efficient fluorescence and color-detecting molecular probes for sensing citrate in water. Herein, we report a macrocycle-based dinuclear foldamer (1) assembled with eosin Y (EY) that has been studied for anion binding by fluorescence and colorimetric techniques in water at neutral pH. Results from the fluorescence titrations reveal that the 1·EY ensemble strongly binds citrate anions, showing remarkable selectivity over a wide range of inorganic and carboxylate anions. The addition of citrate anions to the 1·EY adduct led to a large fluorescence enhancement, displaying a detectable color change under both visible and UV light in water up to 2 µmol. The biocompatibility of 1·EY as an intracellular carrier in a biological system was evaluated on primary human foreskin fibroblast (HF) cells, showing an excellent cell viability. The strong binding properties of the ensemble allow it to be used as a highly sensitive, detective probe for biologically relevant citrate anions in various applications.

Antimicrobial activity and cytotoxicity of 3 photosensitizers activated with blue light.

INTRODUCTION: Pulp repair is less likely to occur when dentin or pulpal tissue remains infected after caries excavation. Yet there are currently few options to kill residual bacteria without damaging resident cells. The current study has evaluated the effect of 3 blue light-activated chemicals on the viability of lactobacilli, odontoblast-like cells (MDPC-23), undifferentiated pulp cells (OD21), and human embryonic stem cells (hESC H1). METHODS: Bacteria were incubated for 15 minutes with curcumin, eosin Y, or rose bengal and then irradiated with blue light (240 seconds). Bacteria were labeled with LIVE/DEAD BacLight Bacterial Viability kit, and viability was assessed by fluorescence-activated cell sorting. Cytotoxicity assays were performed on MDPC-23 cells, OD21, and hESC H1 cells grown in 24-well plates and exposed to the same photosensitizer-light combination. After 24 hours, cellular response was measured by using the methyl-thiazol-diphenyl-tetrazolium assay. Results were statistically analyzed by using one-way analysis of variance and Tukey multiple comparison intervals (α = 0.05). RESULTS: Bacterial viability was significantly reduced after exposure to different combinations of light and photosensitizers; mitochondrial activity of cultured cells remained unaffected when exposed to the same conditions, suggesting a good therapeutic index in vitro. CONCLUSIONS: Blue light-mediated disinfection is promising for the development of new treatment strategies designed to promote pulp repair after carious exposure.