Evaluation of photostability, cellular uptake, photochemical mechanism, and photodynamic efficacy of rose bengal-incorporated mesoporous silica nanoparticles

Abstract

Aim: Rose bengal is a xanthene dye approved by the Food and Drug Administration for determining liver function and some ophthalmologic applications. Research has shown that rose bengal can also be used as an anti-cancer photodynamic therapy agent. However, its hydrophilic tendency and low half-life limit its accumulation in tumor tissue. The purpose of this study was to incorporate rose bengal with mesoporous silica nanoparticles and to conduct comprehensive analyses to investigate the synthesized nanoconjugates in terms of photostability, cellular uptake, and photodynamic therapy efficacy.

Method: Rose bengal was incorporated into mesoporous silica nanoparticles and tested on the A-549 lung cancer cell line to evaluate its photostability, cellular uptake, photochemical mechanism, and photodynamic therapy efficacy. A 530 nm LED light source set to 100 mW/cm² was used to irradiate the samples.

Results: The 1,3-Diphenylisobenzofuran (DPBF) assay results demonstrated that the irradiation of rose bengal-loaded mesoporous silica nanoparticles initiated more DPBF degradation than free rose bengal (76% and 18% DPBF degradation in 5 minutes of irradiation, respectively), which indicates that the incorporation with MSN increases the photodynamic activity of the photosensitizer. Sodium azide assay showed that the photodynamic therapy effect was primarily through singlet oxygen production because the presence of sodium azide inhibited cell killing by around 50%. Additionally, the photostability of rose bengal was enhanced when loaded into the mesoporous silica matrix. However, the cellular uptake did not show a significant change (p<0.54).

Conclusion: The results show that incorporating rose bengal with mesoporous silica increases its efficacy as a photodynamic therapy agent and overcomes the limits of this dye as a photosensitizing agent. Although the cellular uptake did not change, it should be kept in mind that these experiments were conducted on an in vitro model, and the actual effect of this drug delivery strategy would be revealed under in vivo conditions, where circulation and extravasation take place.