We present an electrochemical and optical characterization of 5,10,15,20-tetraphenylporphyrin tin(IV) dichloride (Sn-tpp) in terms of its potential use as a hybrid proteins' label. Our research comprised Sn-tpp and Sn-tpp in the presence of model proteins selected as to mimic a receptor or surface blocking agents: bovine serum albumin, ovalbumin, and immunoglobulin G. In the course of the study, we determined optimal conditions for analysis by means of differential pulse voltammetry, ultraviolet-visible spectrophotometry, and spectrofluorimetry. In electrochemical detection, the influence of the working electrode, solvent, and supporting electrolyte was examined. Displacements of the received signals along the potential axis (a shift of the potential) and changes in signal intensities due to the addition of proteins were observed and analyzed. Simultaneously, the suitability of Sn-tpp as a label in optical detection mode was assessed by using spectroscopic techniques. The obtained results prove Sn-tpp to be applicable in dual and triple detection systems. Such an approach will improve the reliability of the analysis and, at the same time, will allow for widening the range of the linear response with some overlapping ranges of concentrations.
Keywords: Affinity biosensor; Label; Metalloporphyrin; Optical spectra; Voltammetry.
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