A new sulfonic-substituted Zinc(II)-Porphyrin with high aqueous solubility: Synthesis, photophysical properties and application in porcine cell-imaging

The poor aqueous solubility of porphyrins and metalloporphyrins has long impeded their applications in biological systems. In this study, we report the synthesis of a novel porphyrin derivative—ZnTSPP—achieved by introducing four sulfonic acid groups onto a single porphyrin molecule. The photophysical properties were comprehensively characterized via UV–Vis absorption and fluorescence emission spectroscopy in deionized water, phosphate-buffered saline (PBS), and fetal bovine serum (FBS). ZnTSPP exhibits intense absorption in both the Soret and Q bands and displays a reversible pH response. Density Functional Theory (DFT) calculations further corroborate the pH-dependent formation of J- and H-aggregates. Additionally, cellular imaging studies performed on pig kidney epithelial cells (LLC-PK1) demonstrate that ZnTSPP is not only pH-responsive but also an efficient singlet oxygen generator. These attributes position ZnTSPP as a promising agent for biomedical imaging and photodynamic therapy.