No abstract

Rapid and accurate diagnostic technologies for early-state identification of cardiovascular abnormalities have become of high importance to prevent and attenuate their progression. The capability of biosensors to determine an increase in the concentration of cardiovascular protein biomarkers in circulating blood immediately after a myocardial infarction makes them ideal point-of-care platforms and alternative approaches to electrocardiograms, chest X-rays, and different laboratory-based immunoassays. We report here a generic approach toward multianalyte sensing platforms for cardiac biomarkers by developing aptamer-based electrochemical sensors for brain natriuretic peptide (BNP-32) and cardiac troponin I (cTnI). For this, commercial gold-based screen-printed electrodes were modified electrophoretically with polyethyleneimine/reduced graphene oxide films. Covalent grafting of propargylacetic acid integrates propargyl groups onto the electrode to which azide-terminated aptamers can be immobilized using Cu(I)-based “click” chemistry. To ensure low biofouling and high specificity, cardiac sensors were modified with pyrene anchors carrying poly(ethylene glycol) units. In the case of BNP-32, the sensor developed has a linear response from 1 pg mL–1 to 1 μg mL–1 in serum; for cTnI, linearity is observed from 1 pg mL–1 to 10 ng mL–1 as demanded for early-stage diagnosis of heart failure. These electrochemical aptasensors represent a step further toward multianalyte sensing of cardiac biomarkers.

This work presents a comparison of two different aptamers (COX and TRAN) for the detection of the ubiquitous protein lysozyme using aptamer-based biosensors. The detection is based on the specific recognition by the aptamer immobilized on screen printed carbon electrodes (SPCEs) via diazonium coupling reaction. The quantitative detection of lysozyme protein was achieved by electrochemical impedance spectroscopy (EIS). Very good linear ranges and detection limits for the lysozyme detection were obtained, from 0.025 to 1 µM and 725nM using aptamer COX and from 0.025 to 1 µM and 31.7nM using aptamer TRAN. The obtained results showed that the developed aptasensors exhibit good specificity, stability and reproducibility for lysozyme detection. The aptasensors were also tested in wine samples; very good recovery rates were obtained in the range from 96.4 to 102% for lysozyme detection. The recovery rates confirm the reliability and suitability of the developed method in wine matrix. The developed method could be a useful and promising platform for detection of lysozyme in different applications.

In this paper, we have reported a novel electrochemical aptamer-antibody based sandwich biosensor for the detection of lysozyme. In the sensing strategy, an anti-lysozyme aptamer was immobilized onto the carbon electrode surface by covalent binding via diazonium salt chemistry. After incubating with a target protein (lysozyme), a biotinylated antibody was used to complete the sandwich format. The subsequent additions of avidin-alkaline phosphatase as an enzyme label, and a 1-naphthyl phosphate substrate (1-NPP) allowed us to determine the concentration of lysozyme (Lys) via Differential Pulse Voltammetry (DPV) of the generated enzyme reaction product, 1-naphthol. Using this strategy, a wide detection range from 5 fM to 5 nM was obtained for a target lysozyme, with a detection limit of 4.3 fM. The control experiments were carried out by using bovine serum albumin (BSA), cytochrome c and casein. The results showed that the proposed biosensor had good specificity, stability and reproducibility for lysozyme analysis. In addition, the biosensor was applied for detecting lysozyme in spiked wine samples, and very good recovery rates were obtained in the range from 95.2 to 102.0% for lysozyme detection. This implies that the proposed sandwich biosensor is a promising analytical tool for the analysis of lysozyme in real samples.