Study on spectroscopic characterization of meso-tetrakis (4-hydroxyphenyl) porphyrin (THPP) in β-cyclodextrin and its derivatives

Meso-Tetrakis (4-hydroxylphenyl) porphyrin (THPP) is a photosensitize offering an alternate approach to the treatment of cancer in the form of photodynamic therapy (PDT). The supramolecular system of THPP and β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and carboxymethyl-β-cyclodextrin (CM-β-CD), in aqueous solution has been studied by fluorescence and UV–vis spectroscopy. The formation of inclusion complexes has been observed on the base of change of spectroscopy properties. It is noted that the addition of HP-β-CD leads to remarkably strong enhancement of fluorescence intensity (nearly 300 times) of THPP. THPP forms 1:1 inclusion complex with β-CD and 1:2 inclusion complexes with the two other derivatives. Comparative to β-CD and CM-β-CD, the strongest inclusion ability of HP-β-CD can be explained that the hydrogen bond plays significant role in the inclusion process. In addition, the UV–vis experimental showed that the cavity of HP-β-CD causes the transform of the state of THPP, which is in agreement with the effect of polarity of solvent. Comparative to the pure buffer solution, the distinct equilibrium, H 4 THP P 2+ ⇌ H 2 THPP , has been observed in the solution of HP-β-CD. It is certain that the enhancement factor of nearly 300 of fluorescence presents a potential application in the detection of THPP in pharmacokinetics and biodistribution studies.