Advancements in Nanofiber-Based Electrochemical Biosensors for Diagnostic Applications.

Biosensors are analytical tools that can be used as simple, real-time, and effective devices in clinical diagnosis, food analysis, and environmental monitoring. Nanoscale functional materials possess unique properties such as a large surface-to-volume ratio, making them useful for biomedical diagnostic purposes. Nanoengineering has resulted in the increased use of nanoscale functional materials in biosensors. Various types of nanostructures i.e., 0D, 1D, 2D, and 3D, have been intensively employed to enhance biosensor selectivity, limit of detection, sensitivity, and speed of response time to display results. In particular, carbon nanotubes and nanofibers have been extensively employed in electrochemical biosensors, which have become an interdisciplinary frontier between material science and viral disease detection. This review provides an overview of the current research activities in nanofiber-based electrochemical biosensors for diagnostic purposes. The clinical applications of these nanobiosensors are also highlighted, along with a discussion of the future directions for these materials in diagnostics. The aim of this review is to stimulate a broader interest in developing nanofiber-based electrochemical biosensors and improving their applications in disease diagnosis. In this review, we summarize some of the most recent advances achieved in point of care (PoC) electrochemical biosensor applications, focusing on new materials and modifiers enabling biorecognition that have led to improved sensitivity, specificity, stability, and response time.

Electrochemical Sensor for Detection and Degradation Studies of Ethyl Violet Dye.

In this work, a simple and sensitive electrochemical method was developed to determine ethyl violet (EV) dye in aqueous systems by using square wave anodic stripping voltammetry (SWASV) employing a glassy carbon electrode modified with acidic-functionalized carbon nanotubes (COOH-fCNTs). In square wave anodic stripping voltammetry, EV exhibited a well-defined oxidation peak at 0.86 V at the modified GCE. Impedance spectroscopy and cyclic voltammetry were used to examine the charge transduction and sensing capabilities of the modified electrode. The influence of pH, deposition potential, and accumulation time on the electro-oxidation of EV was optimized. Under the optimum experimental conditions, the limit of detection with a value of 0.36 nM demonstrates high sensitivity of COOH-fCNTs/GCE for EV. After detection, it was envisioned to devise a method for the efficient removal of EV from an aqueous system. In this regard a photocatalytic degradation method of EV using Ho/TiO2 nanoparticles was developed. The Ho/TiO2 nanoparticles synthesized by the sol-gel method were characterized by UV-vis, XRD, FTIR, SEM, and EDX. The photocatalytic degradation studies revealed that basic medium is more suitable for a higher degradation rate of EV than acidic and neutral media. The photodegradation kinetic parameters were evaluated using UV-vis spectroscopic and electrochemical methods. The results revealed that the degradation process of EV follows first-order kinetics.

Electrochemical detection of mercuric(ii) ions in aqueous media using glassy carbon electrode modified with synthesized tribenzamides and silver nanoparticles.

This study reports the synthesis, characterization, and mercuric ion detection ability of novel tribenzamides having flexible and rigid moieties. N-{4-[2-(1,3-Benzoxazolyl)]phenyl}-3,5-N,N'-bis(4-alkyloxybenzoyl)benzamides (TBa-TBc) were synthesized from newly synthesized diamine, N-(1,3-benzoxazol-2-yl-phenyl)-3,5-diaminobenzamide (BODA) and p-alkoxybenzoic acids (p-ABA) by amidation reaction. Structural characterization of the synthesized compounds was done through spectroscopic techniques (FT-IR and NMR). The synthesized tribenzamides along with silver nanoparticles were used for modification of a glassy carbon electrode. Square wave anodic stripping voltammetry was carried out to test the performance of the modified electrode for mercuric ion detection. The designed sensor was found to demonstrate the qualities of sensitivity, selectivity, reproducibility and anti-interference ability. The sensing platform helped in detecting femtomolar concentrations of mercuric ions which are much below the level declared toxic by the World Health Organization.

Electrochemical sensing platform for the simultaneous femtomolar detection of amlodipine and atorvastatin drugs.

The development of a proficient and ultra-high sensitive functionalized electrode for accurate analysis of drugs is a long-standing challenge. Herein, we report an electrochemical nanocomposite scaffold, comprising of silver nanoparticles integrated with functionalized carbon nanotubes (COOH-CNTs/Ag/NH2-CNTs) for the simultaneous quantification of two widely used amlodipine (AM) and atorvastatin (AT) drugs. The sandwiched nanocomposite materials were thoroughly characterized morphologically and structurally. The nanocomposite COOH-CNTs/Ag/NH2-CNTs immobilized over glassy carbon electrode catalyzed electron transfer reactions at the electrode-electrolyte interface and facilitated detection of targeted drugs, as revealed by the significant decrease in oxidation potentials at 879 mV and 1040 mV and improved current signals. Electrochemical characterization and testing show that the functionalized porous architecture with a large effective surface area is a promising scaffold for the sensing of a binary mixture of AM and AT with limits of detection in the femtomolar range (77.6 fM, and 83.2 fM, respectively). Besides, the specificity, stability, and reliability of the electrochemical sensing platform in simple and complex biological and pharmaceutical samples with high percentage recoveries highlight its scope for practical applications. Computational studies supported the experimental outcomes and offered insights about the role of modifier in facilitating electron transfer between transducer and analytes.

Phenolic water toxins: redox mechanism and method of their detection in water and wastewater.

Phenolic pollutants are highly toxic and persistent in the environment. Their efficient detection is a pressing social demand. In this regard we introduce a novel ultrasensitive electroanalytical platform for the individual and synchronized detection of three phenolic isomers commonly known as hydroquinone (HQ), resorcinol (RC), and catechol (CC). The sensing device consists of a glassy carbon electrode (GCE) modified with functionalized carbon nanotubes (fCNTs) and gold-silver (Au-Ag NPs) bimetallic nanoparticles. The sandwiched scaffold represented as fCNTs/Au-Ag NPs/fCNTs/GCE efficiently senses HQ, RC, and CC with detection limits of 28.6 fM, 36.5 fM and 42.8 fM respectively. The designed sensor is more promising than reported sensors for phenolic toxins in the context of high sensitivity, selectivity, and rapid responsiveness. The designed sensor also shows the qualities of stability, reproducibility, reliability, and selective recognition capacity for target analytes in multiple real water samples. Moreover, computational calculations explain the function of the electrode modifier in facilitating charge transfer between the transducer and analytes.

Tripeptide Derivative-Modified Glassy Carbon Electrode: A Novel Electrochemical Sensor for Sensitive and Selective Detection of Cd2+ Ions.

A N-[(Benzyloxy)carbonyl]-l-alanyl-l-prolyl-l-leucine-N-cyclohexylcyclohexanamine (Cbz-APL) tripeptide-coated glassy carbon electrode (GCE)-based sensor was used for sensitive and selective recognition of cadmium ions in environmental water. Detailed cyclic voltammetric and electrochemical impedance spectroscopic studies were performed to investigate the charge transfer and sensing activity of the developed electrochemical sensor. Square wave anodic stripping voltammetry (SWASV) was employed to further investigate the sensitivity, selectivity, validity, and applicability of the developed sensor. A sharp electrochemical signal of oxidized Cd at -0.84 V versus Ag/AgCl provides evidence for the higher sensing ability of Cbz-APL/GCE than bare GCE at -0.79 V. Moreover, on Cbz-APL/GCE, extraordinary low detection limits of 4.34 fM and linearity range of 15 nM to 0.1 pM with coefficients of correlation higher than 0.99 for Cd2+ were achieved. Besides, the influence of inorganic and organic interferents on the targeted analyte signals was examined, and high selectivity of Cbz-APL/GCE for Cd2+ ions was observed. Lastly, the validity and applicability of the developed electrochemical sensor for the detection of Cd2+ ions were checked in real water samples, and 100% recovery was obtained.

Amino Acid-Fabricated Glassy Carbon Electrode for Efficient Simultaneous Sensing of Zinc(II), Cadmium(II), Copper(II), and Mercury(II) Ions.

Herein, we present a greener approach to achieve an ultrasensitive, selective, and viable sensor engineered by amino acids as a recognition layer for simultaneous electrochemical sensing of toxic heavy metals (HMs). Electrochemical techniques like electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square-wave anodic stripping voltammetry (SWASV) were applied to demonstrate sensing capabilities of the designed analytical tool. The comparative results of different amino acids demonstrate alanine's superior performance with a well-resolved and enhanced current signal for target metal ions due to strong complexation of its functional moieties. The working conditions for alanine-modified GCE were optimized by investigating the effect of alanine concentration, different supporting electrolytes, pH values, accumulation potentials, and time. The limits of detection for Zn2+, Cd2+, Cu2+, and Hg2+ were found to be 8.92, 5.77, 3.01, and 5.89 pM, respectively. The alanine-modified electrode revealed absolute discrimination ability, stability, and ultrasensitivity toward metal ions even in the presence of multifold interfering species. Likewise, greener modifier-designed electrodes possessed remarkable electrocatalytic activity, cost affordability, reproducibility, and applicability for picomolar level detection of HM ions in real water sample matrixes. Theoretical calculations for the HM-amino acid interaction also support a significantly improved mediator role of the alanine modifier that is consistent with the experimental findings.