A Novel Strategy for Selective Thyroid Hormone Determination Based on an Electrochemical Biosensor with Graphene Nanocomposite

This article presents a novel and selective electrochemical bioassay with antibody and laccase for the determination of free thyroid hormone (free triiodothyronine, fT3). The biosensor was based on a glassy carbon electrode modified with a Fe₃O₄@graphene nanocomposite with semiconducting properties, an antibody (anti-PDIA3) with high affinity for fT3, and laccase, which was responsible for catalyzing the redox reaction of fT3. The electrode modification procedure was investigated using a cyclic voltammetry technique, based on the response of the peak current after modifications. All characteristic working parameters of the developed biosensor were analyzed using differential pulse voltammetry. Obtained experimental results showed that the biosensor revealed a sensitive response to fT3 in a concentration range of 10-200 µM, a detection limit equal to 27 nM, and a limit of quantification equal to 45.9 nM. Additionally, the constructed biosensor was selective towards fT3, even in the presence of interference substances: ascorbic acid, tyrosine, and levothyroxine, and was applied for the analysis of fT3 in synthetic serum samples with excellent recovery results. The designed biosensor also exhibited good stability and can find application in future medical diagnostics.

Fast Screening of Whole Blood Samples and Pharmaceutical Compounds for Enantiorecognition of Free L-T3 , L-T4 , and D-T4

A fast screening method of whole blood was proposed for enantiorecognition of free L-T3 , L-T4 , and D-T4 . Stochastic microsensors based on four inulins (IN, IQ, TEX, and HD) immobilized on diamond paste (DP) were used for recognition of free L-T3 , L-T4 , and D-T4 . For the enantiorecognition of free L-T4 and D-T4 in whole blood and pharmaceutical samples, the best microsensor was the one based on TEX/DP (wide linear concentration ranges, and low limits of quantification). The best limit of detection for the assay of free L-T3 (400 fmol/L) was recorded using the microsensors based on HD/DP, while for the assay of free L-T4, and D-T4 the best limit of determination (1 pmol/L) was recorded using the TX/DP-based microsensor. For the enantiorecognition of free L-T3 in whole blood and pharmaceutical samples the best microsensor was the one based on HD/DP (the wider linear concentration range, and the lower limit of quantification - of pmol/L magnitude order). For the enantiorecognition of free L-T3 in whole blood and pharmaceutical samples the best microsensor was the one based on HD/DP (the wider linear concentration range, and the lower limit of quantification - of pmol/L magnitude order). Free L-T3 , L-T4 , and D-T4 were recovered with high reliabilities in whole blood samples (recoveries higher than 99.00%, with RSD values lower than 1.00%) and pharmaceutical samples (recoveries higher than 95.00% with RSD values lower than 1.00%).

Ionic liquids for the molecular enantiorecognition of freel-T3,l-T4andd-T4

Ionic liquids are used for the enantiorecognition of thyroid hormones.