Biomimetic electrochemical sensors: New horizons and challenges in biosensing applications.

The urge to meet the ever-growing needs of sensing technology has spurred research to look for new alternatives to traditional analytical methods. In this scenario, the glucometer is the flagship of commercial electrochemical sensing platforms, combining selectivity, reliability and portability. However, other types of enzyme-based biosensors seldom achieve the market, in spite of the large and increasing number of publications. The reasons behind their commercial limitations concern enzyme denaturation, and the high costs associated with procedures for their extraction and purification. In this sense, biomimetic materials that seek to imitate the desired properties of natural enzymes and biological systems have come out as an appealing path for robust and sensitive electrochemical biosensors. We herein portray the historical background of these biomimicking materials, covering from their beginnings until the most impactful applications in the field of electrochemical sensing platforms. Throughout the discussion, we present and critically appraise the major benefits and the most significant drawbacks offered by the bioinspired systems categorized as Nanozymes, Synzymes, Molecularly Imprinted Polymers (MIPs), Nanochannels, and Metal Complexes. Innovative strategies of fabrication and challenging applications are further reviewed and evaluated. In the end, we ponder over the prospects of this emerging field, assessing the most critical issues that shall be faced in the coming decade.

Disposable immunoplatforms for the simultaneous determination of biomarkers for neurodegenerative disorders using poly(amidoamine) dendrimer/gold nanoparticle nanocomposite.

Early diagnosis in primary care settings can increase access to therapies and their efficiency as well as reduce health care costs. In this context, we report in this paper the development of a disposable immunoplatform for the rapid and simultaneous determination of two protein biomarkers recently reported to be involved in the pathological process of neurodegenerative disorders (NDD), tau protein (tau), and TAR DNA-binding protein 43 (TDP-43). The methodology involves implementation of a sandwich-type immunoassay on the surface of dual screen-printed carbon electrodes (dSPCEs) electrochemically grafted with p-aminobenzoic acid (p-ABA), which allows the covalent immobilization of a gold nanoparticle-poly(amidoamine) (PAMAM) dendrimer nanocomposite (3D-Au-PAMAM). This scaffold was employed for the immobilization of the capture antibodies (CAbs). Detector antibodies labeled with horseradish peroxidase (HRP) and amperometric detection at - 0.20 V (vs. Ag pseudo-reference electrode) using the H2O2/hydroquinone (HQ) system were used. The developed methodology exhibits high sensitivity and selectivity for determining the target proteins, with detection limits of 2.3 and 12.8 pg mL-1 for tau and TDP-43, respectively. The simultaneous determination of tau and TDP-43 was accomplished in raw plasma samples and brain tissue extracts from healthy individuals and NDD-diagnosed patients. The analysis can be performed in just 1 h using a simple one-step assay protocol and small sample amounts (5 µL plasma and 2.5 µg brain tissue extracts). Graphical abstract.

An electrochemical immunosensor using gold nanoparticles-PAMAM-nanostructured screen-printed carbon electrodes for tau protein determination in plasma and brain tissues from Alzheimer patients.

This work reports a new sensitive strategy for the determination of tau protein, a hallmark of Alzheimer's disease (AD), involving a sandwich immunoassay and amperometric detection at disposable screen-printed carbon electrodes (SPCEs) modified with a gold nanoparticles-poly(amidoamine) (PAMAM) dendrimer nanocomposite (3D-Au-PAMAM) covalently immobilized onto electrografted p-aminobenzoic acid (p-ABA). The capture antibody (CAb) was immobilized by crosslinking with glutaraldehyde (GA) on the amino groups of the 3D-Au-PAMAM-p-ABA-SPCE, where tau protein was sandwiched with a secondary antibody labeled with horseradish peroxidase (HRP-DAb). Amperometry at -200 mV (vs the Ag pseudo-reference electrode) upon the addition of hydroquinone (HQ) as electron transfer mediator and H2O2 as the enzyme substrate was used to detect the immunocomplex formation. The great analytical performance of the immunosensor in terms of selectivity and low limit of detection (LOD) (1.7 pg mL-1) allowed the direct determination of the target protein in raw plasma samples and in brain tissue extracts from healthy individuals and post mortem diagnosed AD patients, using a simple and fast protocol.

Sensitive determination of carbendazim in orange juice by electrode modified with hybrid material.

This paper describes the application of a glassy carbon electrode modified with a thin film of mesoporous silica/multiwalled carbon nanotubes for voltammetric determination of the fungicide carbendazim (CBZ). The hybrid material, (SiO2/MWCNT), was obtained by a sol-gel process using HF as the catalyst. The amperometric response to CBZ was measured at +0.73 V vs. Ag/AgCl by square wave voltammetry at pH 8.0. SiO2/MWCNT/GCE responded to CBZ in the linear range from 0.2 to 4.0 µmol L(-1). The calculated detection limit was 0.056 µmol L(-1), obtained using statistical methods. The SiO2/MWCNT/GCE sensor presented as the main characteristics high sensitivity, low detection limit and robustness, allowing CBZ determination in untreated real samples. In addition, this strategy afforded remarkable selectivity for CBZ against ascorbic and citric acid which are the main compounds of the orange juice. The excellent sensitivity and selectivity yielded feasible application for CBZ detection in orange juice sample.