Preparation of magnetic nanoparticle-cholesterol imprinted polymer using semi-covalent imprinting approach for ultra-effective and highly selective cholesterol adsorption

Abstract

In the present study, a magnetic nanoparticle-cholesterol imprinted polymer for cholesterol (CHO) adsorption exploring semi-covalent imprinting approach was proposed. The Fe3O4/SiO2/MIP synthesis was carried out by using surface imprinting polymerization technique on the silica-coated magnetite, using 3-(triethoxysilyl)propyl isocyanate (ICPTES) as functional monomer and CHO as template, where occurs a covalent bond between them, and TEOS as a cross-linking reagent. The Fe3O4/SiO2/MIP material was characterized by X-ray diffractometry (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray fluorescence (XRF), values of specific surface area, pore size, and pore volume through nitrogen adsorption/desorption isotherms and vibrating sample magnetometry (VSM). The surface area of Fe3O4/SiO2/MIP (151.04 m2 g−1) was significantly higher compared to Fe3O4/SiO2/NIP (66.09 m2 g−1) and based on relative selectivity coefficient (k´), Fe3O4/SiO2/MIP showed higher selectivity towards CHO in competitive adsorption studies CHO/5-α-cholestane, CHO/7-dehydrocholesterol and CHO/estradiol in chloroform. From the kinetic study, the adsorption equilibrium for Fe3O4/SiO2/MIP was quickly achieved at 60 s in a vortex mixer and described by the second-order kinetic model. High adsorption capacity for Fe3O4/SiO2/MIP (314.1 mg g−1) was obtained from the isotherm studies, and it was adjusted to dual-site Langmuir–Freundlich isotherm model. The obtained outcomes in terms of selectivity, maximum adsorption capacity, and fast kinetic make the magnetic nanoparticle-cholesterol imprinted polymer an outstanding material for future application in magnetic dispersive solid-phase extraction for analytical purposes.