Preparation of a biomimetic Cu(II) protoporphyrin magnetic nanocomposite and its application for the selective adsorption of angiotensin I

Abstract

In this study, a novel Cu(II) protoporphyrin polymer-based magnetic nanocomposite, CuPPIX@MNPs, is obtained by electropolimerization of metalloporphyrin IX dimethyl ester onto Fe3O4 nanoparticles in organic medium. CuPPIX@MNPs are proposed as a biomimetic magnetic solid-phase extraction sorbent with high selectivity toward peptides containing histidine residues. The nanocomposite was characterized by SEM/EDX, TEM and FTIR. Magnetic saturation values for magnetic nanoparticles (MNPs), naked MNPs (74 emu g−1) and CuPPIX@MNPs (43 emu g−1), were obtained at 300 K. At pH 7, CuPPIX@MNPs show selective adsorption toward angiotensin, about 90% adsorption vs 49 % adsorption for naked MNPs. In order to evaluate the mechanisms involved in angiotensin adsorption onto CuPPIX@MNPs, different adsorption–desorption conditions and the model that describes the adsorption isotherm for both sorbents were determined. The parameters of fitting analyses were qm = 2.55 mg g−1 and b = 0.012 L mg−1 by Langmuir model for naked MNPs, and KF = 0.4105 mg g−1 and n = 2.09 by Freundlich model for CuPPIX@MNPs. This indicates that CuPPIX@MNPs have heterogenous adsorption surface and different adsorption sites. The Freundlich exponent greater than 1 suggests strong adsorption interactions between angiotensin and this magnetic solid-phase extraction (MSPE) nanomaterial. The selectivity the CuPPIX@MNPs toward angiotensin was evaluated in an aqueous mixture composed of four peptides by capillary electrophoresis. Finally, the intrinsic characteristics of the magnetic substrate, the stable inclusion of the copper in an environment that favors the interaction with histidine residues, in addition to easy and reproducible preparation of the nanocomposite offer a very interesting strategy for the design of the MSPE sorbents.