Abstract: AimTo establish a simple, rapid and accurate electroanalytical method for water soluble porphyrin meso-tetrakis-(4-sulfonatophenyl) porphyrin (TPPS₄); to clarify the reaction between water soluble porphyrins and bovine serum albumin (BSA); and to determine the interaction of TPPS₄ with BSA in the absence of presence of cyclodextrins (CDs), separately. MethodsThree methods including LSV, UV spectroscopy and fluorescence spectroscopy had been employed to the relevant experiments. The way of employing three methods at the same time could make the experiment results more reliable. ResultsIn the supporting electrolyte of NaH₂PO₄-Na₂HPO₄ (pH 7.18), a sensitive reduction peak of TPPS₄ was found by linear sweep voltammetry (LSV), the peak potential (E_P) was -0.70 V (vs SCE). The relationship between the second derivative peak of LSV (i_P″)and the concentration of TPPS₄ was linear from 1.0×10^-7 mol·L^-1 to 1.0×10^-5 mol·L^-1, the square of correlation coefficients (r²) were 0.998 3 and 0.999 3, respectively. The relative standard deviation (RSD) was 0.56% (n=5). The mean recovery of TPPS₄ was 99.59%. In NH₄Cl-NH₃·H₂O buffers (pH 9.05), it was proved that BSA and TPPS₄ could interact with each other and form 1∶1 TPPS₄-BSA supramolecular system. Moreover, the interaction between TPPS₄ and BSA had been investigated by adding cyclodextrins (CDs). The interaction of TPPS₄ with BSA was facilitated both by hydroxypropyl-β-CD (HP-β-CD) and sulforbutylether-β-CD (SBE-β-CD). ConclusionAn electroanalytical method for TPPS₄ has been established by LSV. The porphyrin drugs included by CDs could react with protein existing inside the human body easier. The consequences of this article also show that CDs will play important role in controlling and releasing the porphyrin drugs.