Effect of Acidification on the Absorption and Fluorescence Properties of Sn(IV) Chlorin e6 Dichloride Trisodium Salt

Abstract

Chlorins are potential photosensitizers for photodynamic therapy because of their intense absorption in the red spectral region. In this study, the effect of pH on the absorption and fluorescence of Sn(IV) chlorin e6 dichloride trisodium salt was investigated. Absorption, fluorescence emission and fluorescence excitation spectra of the photosensitizer were recorded at different pH values in an analytical buffer solution with and without fetal bovine serum (FBS). In the neat buffer solution, changing the pH resulted in small shifts in both absorption and emission spectra. The shape of the excitation spectra also changed slightly, with shoulders almost vanishing below pH 5. Also, a pronounced reduction of the fluorescence intensity was observed upon acidification. The fluorescence intensity gradually decreased as the concentration of FBS was increased without shifting fluorescence maxima. The absorbance of the photosensitizer in different solvents was recorded and revealed that Sn(IV) chlorin e6 is highly soluble in polar solvents.

pH-sensitive metal-phenolic network capsules for targeted photodynamic therapy against cancer cells

“…This phenomenon may be caused by the PEG-MSN encapsulation of HMME, which has larger absorption at 392 nm in pH 7.4 than that in pH 5.0 [37]. The acidic environment facilitates the protonation of pyrrole nitrogen atoms in HMME and changes the symmetry of the conjugated ring and the absorbance of both Soret band and Q band, leading to a little lower singlet oxygen quantum yields of MPN@HMMEs in pH 5.0 [44].…”