3D stochastic microsensors for molecular recognition and determination of heregulin-α in biological samples.

Two 3D stochastic microsensors based on single and multi-walled carbon nanotubes modified with 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine manganese (III) chloride were proposed for the molecular recognition and determination of heregulin-α, in whole blood samples and tumour brain tissues. The proposed 3D stochastic sensors had limits of determinations of 102 fg mL-1 and high sensitivities. The linear concentration ranges of the two 3D stochastic microsensors covered the healthy people as well as the patients confirmed with brain cancer. Determination of heregulin-α was done in whole blood and tissue samples using the screening method based on the proposed 3D stochastic microsensors as well as using the ELISA method; very good correlations were obtained between the two methods proving that the proposed method can be used in screening tests of whole blood and tumoural tissue samples for molecular recognition and determination of heregulin-α.

Gold nanoparticle-graphene quantum dots nanozyme for the wide range and sensitive electrochemical determination of quercetin in plasma droplets.

A gold nanoparticle/graphene quantum dots (AuNP/GQD) nanozyme-modified screen-printed carbon electrode (SPCE) was developed for fast and ultrasensitive determination of quercetin by square-wave voltammetry. The nanosensing device was inserted in miniaturized equipment. Under the optimal experimental conditions, a good linear relationship between oxidation peak current and concentration of quercetin within a very wide range of 1.0 × 10-10 to 1.0 × 10-3 mol L-1 was obtained, with a very low limit of detection of 3.3 × 10-11 mol L-1. To prove the performance of the method, the reproducibility was evaluated and the RSD values were lower than 5.3% and 5.1% for the intra-day and inter-day measurements, respectively. The method was applied to the sensitive determination of quercetin in human plasma droplets with recovery rates of 92.6 to 101.7%.Graphical abstract.