Label-Free Assessment of Neuron-Specific Enolase via Polydopamine over a Carbon-Nanotube-Based Flexible Immunosensor.

A label-free electrochemical immunosensor was developed for the rapid and sensitive detection of neuron-specific enolase (NSE). The electropolymerization of dopamine in conjunction with highly conductive carbon nanotubes offers a simple and quick platform for the direct anchoring of antibodies without the assistance of any coupling agent as well as a blocking agent. The developed immunosensor exhibited a wider detection range from 120 pM (9 ng mL-1) to 3 nM (200 ng mL-1) for NSE with a high sensitivity of 3.9 µA pM-1 cm-2 in 0.1 M phosphate-buffered saline (PBS) at physiological pH (7.4). Moreover, the short recognition time (15 min) for the antigen enabled the detection to be fast and less invasive. Additionally, the evaluation of a rate constant at various concentrations of NSE via feedback mode of scanning electrochemical microscopy (SECM) explained the profound effect of antigen concentration on the rate of flow of electrons. Therefore, the proposed immunosensor can be a promising tool for the early detection of small cell lung cancer in a very short period of time with consistent accuracy.

Realizing the label-free sensitive detection of carcinoembryogenic antigen (CEA) in blood serum via a MNC-decorated flexible immunosensor.

A label-free electrochemical immunosensor utilising nitrogen-rich mesoporous carbon (MNC) as the substrate material was developed for the sensitive quantification of carcinoembryonic antigen (CEA). The synergic interactions between MNC and AbCEA also eliminated the need for coupling agents such as EDC/NHS. The novel immunosensor demonstrated a wide detection range from 500 fM (9.04 pg mL-1) to 50 nM (1 µg mL-1) and a low detection limit (LOD) of 500 fM. Moreover, the immunosensor showed sensitivities of 12.27 mA nM-1 cm-2 and 0.066 mA nM-1 cm-2 for detecting CEA in the linear ranges 10 pM to 1 nM and 2 nM to 50 nM, respectively, while maintaining long-term storage stability of 6 weeks. Analysis of real serum sample analysis yielded highly accurate results with recovery rates ranging from 99.3% to 103.7%. Furthermore, the developed paper-based screen-printed electrode exhibited a similar detection range, suggesting its potential for use in point-of-care detection devices in future applications.

Advances and Challenges in Nanomaterial-Based Electrochemical Immunosensors for Small Cell Lung Cancer Biomarker Neuron-Specific Enolase.

Early and rapid detection of neuron-specific enolase (NSE) is highly significant, as it is putative biomarker for small-cell lung cancer as well as COVID-19. Electrochemical techniques have attracted substantial attention for the early detection of cancer biomarkers due to the important properties of simplicity, high sensitivity, specificity, low cost, and point-of-care detection. This work reviews the clinically relevant labeled and label-free electrochemical immunosensors developed so far for the analysis of NSE. The prevailing role of nanostructured materials as electrode matrices is thoroughly discussed. Subsequently, the key performances of various immunoassays are critically evaluated in terms of limit of detection, linear ranges, and incubation time for clinical translation. Electrochemical techniques coupled with screen-printed electrodes developing market level commercialization of NSE sensors is also discussed. Finally, the review concludes with the current challenges associated with available methods and provides a future outlook toward commercialization opportunities for easy detection of NSE.

Tailoring cellulose paper via electroless CuSnB deposition for selective electrochemical detection of dopamine.

A novel, biodegradable substrate based, and cost-effective flexible electrochemical sensor was developed for the highly selective and sensitive detection of one of the major neurotransmitters, dopamine, which can be utilised as a disposable electrode for point-of-care diagnostic applications. The active material CuSnB decorated over cellulose paper exhibits good sensitivities of 3.92 µA µM-1 cm-2 with a limit of detection of 0.5 nM. Moreover, the flexible sensor demonstrated superior selectivity towards co-existing metabolites such as ascorbic acid, glucose, and uric acid, in addition to stability at various mechanical deformations.

Flexible electrochemical sensor for highly sensitive and selective non-enzymatic detection of creatinine via electrodeposited copper over polymelamine formaldehyde.

A non-enzymatic electrochemical biosensor was developed for highly sensitive detection of creatinine using copper nanoparticles supported over polymelamine formaldehyde. The synergy between the electrodeposited copper nanoparticles over the highly porous polymer (eCu-PMF) provided a greener platform to boost up the electron transport at the electrode electrolyte interface by eliminating the role of redox species as well as interference of major interferents like glucose, dopamine, and ascorbic acid in physiological media 0.1 M PBS (pH 7.4). The proposed sensor exhibited a wide detection range of 100 fM-60 mM with high sensitivities of 0.320 mA nM-1 cm-2 and 3.8 mA nM-1 cm-2. Moreover, the sensor was applied to real samples of serum creatinine and recoveries of 97 to 114% were found. Additionally, a paper-based flexible screen-printed electrode was fabricated which displayed an excellent activity with the same detection range of 100 fM-60 mM and long-term storage stability of 15 days.

Ultrasensitive and Highly Selective Electrochemical Detection of Dopamine Using Poly(ionic liquids)-Cobalt Polyoxometalate/CNT Composite.

A novel sandwich polyoxometalate (POM) Na12[WCo3(H2O)2(CoW9O34)2] and poly(vinylimidazolium) cation [PVIM+] in combination with nitrogen-doped carbon nanotubes (NCNTs) was developed for a highly selective and ultrasensitive detection of dopamine. Conductively efficient heterogenization of Co5POM catalyst by PVIM over NCNTs provides the synergy between PVIM-POM catalyst and NCNTs as a conductive support which enhances the electron transport at the electrode/electrolyte interface and eliminates the interference of ascorbic acid (AA) at physiological pH (7.4). The novel PVIM-Co5POM/NCNT composite demonstrates a superior selectivity and sensitivity with a lowest detection limit of 500 pM (0.0005 µM) and a wide linear detection range of 0.0005-600 µM even in the presence of higher concentration of AA (500 µM).