Comparative study of two surface techniques of proteins imprinting in a polydopamine matrix. Application to immunoglobulin detection
Résumé
A comparison between molecularly imprinted polymer strategies based on the same monomer for large protein detection is rarely performed. Here, immunoglobulin (IgG) was chosen as a protein model. The first approach is based on the cyclic voltammetry (CV) electropolymerization of a mixture of dopamine monomer and IgG template, while in the second route the protein is anchored to the transducer's surface, via a mixed self-assembled monolayer of mercaptohexanol (MHOH) and mercaptoundecanoic acid (MUDA), prior to CV dopamine electropolymerization. To guarantee the efficiency and accuracy of both approaches, several parameters were optimized mainly the CV cycles' number, the scan rate value, the ratio of dopamine-monomer to IgG-template, and the nature of the extracting agent. Square wave voltammetry (SWV), hydrophobicity and surface energy measurements were investigated to follow up all surface modification steps and IgG detection in the concentration range of 10−15 to 10−2 mg mL−1. Both strategies exhibited the same limit of detection (LOD = 10−15 mg mL−1). Sensitivities of the designed electrochemical sensors were of the order of (7.23 0.53) 10−5 mA−1 cm2/mg.mL−1 and (8.85 0.27) 10−2 mA−1 cm2/mg.mL−1 for the molecularly imprinted polymers (MIPs) 1 and 2 respectively. The dissociation constants, estimated from a combined power-law-Hill model at (1.65 0.45) 10−10 mg mL−1 and (1.77 0.43) 10−11 mg mL−1, confirm the strong binding between the designed MIPs and IgG protein. Contrary to what was reported in the literature, both MIPs strategies based on the same monomer polydopamine presented similar sensing performances in terms of imprinting factor, sensitivity, reproductibility, LOD values and validation in real samples.