Self-Reporting Molecularly Imprinted Polymer-Based Electrochemical Sensors for Structurally Similar Analytes

Abstract

Molecularly imprinted polymers (MIPs) having inherent redox activity is developed for reagent-free electrochemical detection of steroid hormone biomarker cortisol. Ferrocenylmethyl methacrylate and acrylic acid were used as redox and functional monomers, respectively. Free radical initiated co-polymerization process was performed in the presence of cortisol as a template to create electroactive MIPs. The copolymerized ferrocenylmethyl methacrylate network provided the redox-active and self-reporting electrochemical platform for detecting redox-inactive biomarkers without using any additional reagents. Cortisol is chosen as the model analyte to evaluate the performance of the self-reporting molecular recognition property. The self-reporting MIPs allowed the quantitative detection of cortisol (as low as 0.5 ng) in the presence of other structurally similar steroid hormones.

Introducing Nanoscale Electrochemistry in Small-Molecule Detection for Tackling Existing Limitations of Affinity-Based Label-Free Biosensing Applications

“…Detection of small molecules such as metabolites, neurotransmitters, and hormones can provide useful biological information for the diagnosis of specific diseases, prediction of treatment responses, and monitoring of health conditions. , Among various sensing techniques, electrochemical detection has great advantages for point-of-care (PoC) applications due to its merits, such as easy miniaturization, low cost, and fast response. , While electroactive small target molecules are easily detected by direct charge transfer from their own redox reactions on electrode surfaces, electrochemically inactive small molecules can also be detected by monitoring the electroactive products generated from highly selective enzymatic reactions with target molecules. , However, electrochemically inactive small molecules, not involving proper enzymatic reactions generating electroactive products, can be detected with affinity-based electrochemical (bio)­sensors, in which small target molecules are selectively bound with bioreceptors (e.g., antibodies and aptamers) or biomimetic receptors (e.g., molecularly imprinted polymers). − Traditional affinity-based electrochemical (bio)­sensors require either electroactive labels such as labeled secondary antibodies for voltammetric detections or external solutions containing redox probes for electrochemical impedance spectroscopic detections, which are not suitable for PoC applications. , Moreover, the affinity-based (bio)­sensors exhibit extremely high binding affinity, which renders highly selective detection of target molecules but creates difficulty in the regeneration of receptors, impeding repetitive and continuous measurements. Therefore, a significant effort has been made on developing “label-free” and “bind-and-read” electrochemical sensing techniques by coimmobilizing (bio)­receptors and redox probes on electrode surfaces toward the decentralized on-site monitoring of clinically important molecules. − …”