Nanometric polythiophene films with electrocatalytic activity for non-enzymatic detection of glucose

Electrochemical Sensors Based on Conducting Polymers for the Aqueous Detection of Biologically Relevant Molecules

Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability in environmental conditions. In this state-of-the-art review, synthetic processes, morphological characterization, and nanostructure formation are analyzed for relevant literature about electrochemical sensors based on conducting polymers for the determination of molecules that (i) have a fundamental role in the human body function regulation, and (ii) are considered as water emergent pollutants. Special focus is put on the different types of micro- and nanostructures generated for the polymer itself or the combination with different materials in a composite, and how the rough morphology of the conducting polymers based electrochemical sensors affect their limit of detection. Polypyrroles, polyanilines, and polythiophenes appear as the most recurrent conducting polymers for the construction of electrochemical sensors. These conducting polymers are usually built starting from bifunctional precursor monomers resulting in linear and branched polymer structures; however, opportunities for sensitivity enhancement in electrochemical sensors have been recently reported by using conjugated microporous polymers synthesized from multifunctional monomers.

Recent Advances of Conducting Polymers and Their Composites for Electrochemical Biosensing Applications

Conducting polymers (CPs) have been at the center of research owing to their metal-like electrochemical properties and polymer-like dispersion nature. CPs and their composites serve as ideal functional materials for diversified biomedical applications like drug delivery, tissue engineering, and diagnostics. There have also been numerous biosensing platforms based on polyaniline (PANI), polypyrrole (PPY), polythiophene (PTP), and their composites. Based on their unique properties and extensive use in biosensing matrices, updated information on novel CPs and their role is appealing. This review focuses on the properties and performance of biosensing matrices based on CPs reported in the last three years. The salient features of CPs like PANI, PPY, PTP, and their composites with nanoparticles, carbon materials, etc. are outlined along with respective examples. A description of mediator conjugated biosensor designs and enzymeless CPs based glucose sensing has also been included. The future research trends with required improvements to improve the analytical performance of CP-biosensing devices have also been addressed.

A molecular dynamics study on glucose molecular recognition by a non-enzymatic selective sensor based on a conducting polymer

Poly(hydroxymethyl-3,4-ethylendioxythiophene) (PHMeDOT), a very electroactive polythiophene derivative bearing a dioxane ring fused onto the thiophene ring and an exocyclic hydroxymethyl substituent, is able to electrocatalyze the oxidation of glucose in the presence of interferents (e.g. dopamine, uric acid and ascorbic acid) without the assistance of an enzymatic catalyst. In this work, after demonstrating that the chronoamperometric response of such polythiophene derivatives allows discrimination of glucose from fructose, the PHMeDOTsugar recognition mechanism has been investigated using atomistic computer simulations. More specifically, molecular dynamics simulations were conducted on model systems formed by a steel surface covered with a nanometric film of PHMeDOT, which was immersed in an aqueous environment with a few explicit sugar molecules (i.e. glucose or fructose). Analyses of the trajectories indicate that glucose interacts with PHMeDOT forming a well-defined network of specific hydrogen bonds. More specifically, glucose prefers to interact as a hydrogen bonding donor using the hydroxyl group tether to the main sugar ring, while PHMeDOT acts as the hydrogen bonding acceptor. Interestingly, (glucose)O-HO(PHMeDOT) interactions involve, as hydrogen bonding acceptors, not only the oxygen atoms of the dioxane ring but also the oxygen atom of the exocyclic hydroxymethyl substituent, which is a differential trend with respect to the other polythiophene derivatives that do not exhibit sensing ability. In contrast, fructose does not present such well-defined patterns of specific interactions, especially those that are distinctive because of the exocyclic hydroxymethyl substituent, making the experimental observations understandable.