The formation of complexes with albumin increases the stability of the protoporphyrin IX spectra.

Photodynamic therapy is a high-target, low-invasive treatment utilized to manage a variety of malignant diseases and precancerous lesions. Protoporphyrin IX (PpIX) is one of the most important photosensitizers used in photodynamic therapy, carried to the cancer tissue by serum albumin. Its delivery by transport protein is one of the major factors in determining the efficacy of photodynamic therapy. The distribution of the albumin-PpIX complexes to the target tissue enables the accomplishment of an optimal PDT effect. This study aimed to assess in vitro the stability of spectrofluorimetric spectra of albumin-PpIX complexes. The experiment used three chemicals: PpIX, human serum albumin (HSA), and bovine serum albumin (BSA). Spectral data was recorded using a Kontron SFM-25 Instrument AG, at two excitation wavelengths λ=280 nm and 295 nm. A concentration of 1x10M of PpIX, in combination with 1.25x10M of HSA and 4x10M of BSA, have been recorded repetitively for ten days and compared to the initial spectrum. The maximum of PpIX fluorescence changed significantly on the first day following sample preparation. The maximum of PpIX - serum albumin complex was stable 10 and 4 days for HSA and 5 and 2 days for BSA for λ=280 nm and 295 nm, respectively. The formation of a complex between PpIX and serum albumin was seen to extend the stability of the spectrofluorimetric spectrum. However, a less significant effect was observed in the case of BSA, which could most plausibly be attributed to the variations in primary structure between HSA and BSA, leading to discernible variations in spectroscopic measurements.