Electrochemical Biosensors Based on Molecularly Imprinted Polymer Biomimetic Receptors

Abstract

This thesis presents the utilization of molecularly imprinted polymer (MIP) biomimetic receptors as recognition elements in the development of two MIP electrochemical biosensors. One is a MIP cryogel for the direct detection of insulin, performed in a flow system. The other is an electrochemical biosensor with dual MIPs for the simultaneous determination of creatinine and albumin to provide the albumin to creatinine ratio (ACR) value. The insulin sensor was prepared using a gold electrode modified with carboxylated multiwalled carbon nanotubes (f-MWCNTs) to provide a large surface area platform for the high loading of the MIP cryogel and to increase the conductivity of the sensor. The MIP cryogel porous structure provided a large number of the imprinted recognition sites and improved the access of insulin to/from the MIP cavities. In addition, the flow system facilitated the mass transfer and limited the non-specific binding. This MIP cryogel provided a 0.050-1.40 pM linear range and a low limit of detection (LOD) of 33 fM with good stability at room temperature. For the dual MIP sensor, it was prepared on the dual screen-printed carbon electrodes (SPdCEs) modified with f-MWCNTs and redox probes, polymethylene blue (PMB) and ferrocene (Fc). The surface imprinting and electropolymerization were carried out to obtain more controlled imprinted binding sites of the two analytes on the respective electrode. This sensor was able to selectively recognize the two analytes with linear ranges of 5.0-100 ng mL-1 and 100-2500 ng mL-1 for creatinine and 5.0-100 ng mL-1 for albumin with an LOD of 1.5±0.2 ng mL-1 and 1.5±0.3 ng mL-1, respectively. The two MIP electrochemical biosensors exhibited good reusability and the real sample detection results showed comparable performances to the clinically employed standard methods (P  0.05). The good performances of these MIP electrochemical biosensors, i.e., high sensitivity and selectivity, low limit of detection, and high stability indicate their potential as alternative methods for analysis.