An ultra-sensitive and highly selective impedimetric sensor for vitamin D measurement based on a novel imprinted polymer synthesized utilizing template-derived functional monomer

Abstract

A novel vitamin D₃-imprinted (VD)-polymer was synthesized utilizing a functional monomer derived from vitamin D₃. Acryloyl chloride reacted with VD leading to a functional monomer capable of interaction with VD during the molecularly imprinted polymer (MIP) synthesis step. Vitamin D₃-derived functional monomer and divinylbenzene were copolymerized in the presence of vitamin D₃ in order to create a new MIP, holding VD selective cavities, after template (VD) removal from the polymer. The MIP nanoparticles were used for the modification of a carbon paste electrode to fabricate VD selective sensor. The charge transfer resistance of Fe(CN)₆^3-/Fe(CN)₆^4-couple for the MIP-modified electrode increased significantly in the presence of VD; whereas, the non-imprinted polymer (NIP)-CPE electrode was not affected by VD, suggesting well acting of recognition sites of the MIP nanoparticles, incorporated into the electrode. The sensing mechanism was attributed to a gate effect principle. Interring of VD molecules to the selective sites of the MIP nanoparticles, existing on the electrode surface, makes the MIP particles swell and this leads to blocking the majority of routes via which the probe electroactive species accesses the carbon particles at the electrode surface. The MIP electrode was not sensitive to some molecules structurally similar to VD, suggesting a highly selective nature of the designed sensor. The new VD sensor impedimetric response as a function of the logarithm of VD concentration was found to be linear in the range of 1.0-100.0 pM. The detection limit of the sensor was estimated to be 0.22 pM. The sensor was used for VD level estimation in plasma samples.

Keywords: Carbon paste; Charge transfer; Impedimetric sensor; Imprinted polymer; Vitamin D(3).