Electrochemistry is a genuinely interdisciplinary science that may be used in various physical, chemical, and biological domains. Moreover, using biosensors to quantify biological or biochemical processes is critical in medical, biological, and biotechnological applications. Nowadays, there are several electrochemical biosensors for various healthcare applications, such as for the determination of glucose, lactate, catecholamines, nucleic acid, uric acid, and so on. Enzyme-based analytical techniques rely on detecting the co-substrate or, more precisely, the products of a catalyzed reaction. The glucose oxidase enzyme is generally used in enzyme-based biosensors to measure glucose in tears, blood, etc. Moreover, among all nanomaterials, carbon-based nanomaterials have generally been utilized thanks to the unique properties of carbon. The sensitivity can be up to pM levels using enzyme-based nanobiosensor, and these sensors are very selective, as all enzymes are specific for their substrates. Furthermore, enzyme-based biosensors frequently have fast reaction times, allowing for real-time monitoring and analyses. These biosensors, however, have several drawbacks. Changes in temperature, pH, and other environmental factors can influence the stability and activity of the enzymes, affecting the reliability and repeatability of the readings. Additionally, the cost of the enzymes and their immobilization onto appropriate transducer surfaces might be prohibitively expensive, impeding the large-scale commercialization and widespread use of biosensors. This review discusses the design, detection, and immobilization techniques for enzyme-based electrochemical nanobiosensors, and recent applications in enzyme-based electrochemical studies are evaluated and tabulated.

Nanomaterials have revolutionized scientific research due to their exceptional physical and chemical capabilities. Carbon-based nanomaterials such as graphene and its derivates have excellent electrical, optical, thermal, physical, and chemical properties that have made them indispensable in several industries worldwide, including medicine, electronics, and energy. By incorporating carbon-based nanomaterials as nanofillers in electrospun nanofibers (ESNFs), smoother and highly conductive nanofibers can be achieved that possess a large surface area and porosity. This approach provides a superior alternative to traditional materials in the development of improved biosensors. Carbon-based ESNFs, among the most exciting new-generation materials, have many applications, including filtration, pharmaceuticals, biosensors, and membranes. The electrospinning technique is a highly efficient and cost-effective method for producing desired nanofibers compared to other methods. Various types of natural and synthetic organic polymers have been successfully utilized in solution electrospinning to produce nanofibers directly. To create diagnostics devices, various biomolecules like antibodies, enzymes, aptamers, ligands, and even cells can be bound to the surface of nanofibers. Electrospun nanofibers can serve as an immobilization matrix to create a biofunctional surface. Thus, biosensors with desired features can be produced in this way. This study comprehensively reviews biosensors that integrate nanodiamonds, fullerenes, carbon nanotubes, graphene oxide, and carbon dots into electrospun nanofibers.

Herein, dendrimer-modified montmorillonite (Mt)-decorated poly-Ɛ-caprolactone (PCL) and chitosan (CHIT)-based nanofibers were prepared. Mt was modified with a poly(amidoamine) generation 1 (PAMAM_G1) dendrimer, and the obtained PAMAM_G1–Mt was incorporated into the PCL–CHIT nanofiber’s structure. The PCL–CHIT/PAMAM_G1–Mt nanofibers were conjugated with glutamate oxidase (GluOx) to design a bio-based detection system for monosodium glutamate (MSG). PAMAM_G1–Mt was added to the PCL–CHIT backbone to provide a multipoint binding side to immobilize GluOx via covalent bonds. After the characterization of PCL–CHIT/PAMAM_G1–Mt/GluOx, it was calibrated for MSG. The linear ranges were determined from 0.025 to 0.25 mM MSG using PCL–CHIT/Mt/GluOx and from 0.0025 to 0.175 mM MSG using PCL–CHIT/PAMAMG₁–Mt/GluOx (with a detection limit of 7.019 µM for PCL–CHIT/Mt/GluOx and 1.045 µM for PCL–CHIT/PAMAMG₁–Mt/GluOx). Finally, PCL–CHIT/PAMAMG₁–Mt/GluOx was applied to analyze MSG content in tomato soup without interfering with the sample matrix, giving a recovery percentage of 103.125%. Hence, the nanofiber modification with dendrimer-intercalated Mt and GluOx conjugation onto the formed nanocomposite structures was performed, and the PCL–CHIT/PAMAM_G1–Mt/GluOx system was successfully developed for MSG detection.

Multifunctional electrospun nanofibers (ENs) with improved properties have increased attention nowadays. Their insoluble forms in water with decreased hydrophobicity are desired for the immobilization of biological molecules. Also, the addition of functional groups on the backbone provides the conjugation of biomolecules onto the surface of ENs via covalent bonds to increase their stability. Here, poly(vinylidene fluoride) (PVDF) was chosen to prepare a platform, which is insoluble in water, and polyethylenimine (PEI) was used to add amine groups on the surface of ENs to bind biological molecules via covalent conjugation. So, PVDF-PEI nanofibers were prepared on a glassy carbon electrode to immobilize an antimethamphetamine antibody (Anti-METH) as a model biomolecule. The obtained PVDF-PEI/Anti-METH was used for the bioelectrochemical detection of methamphetamine (METH), a common illicit drug. Bioelectrochemical detection of METH on PVDF-PEI/Anti-METH-coated electrodes was carried out by voltammetry in the range of 2.0-50 ng/mL METH. Moreover, the effect of dansyl chloride (DNC) derivatization of METH on the sensitivity of PVDF-PEI/Anti-METH was tested. Finally, METH analysis was carried out in synthetic body fluids. The obtained results showed that PVDF-PEI ENs can be adopted as an immobilization matrix for the biorecognition elements of biobased detection systems, and the derivative of METH (METH-DNC) increased the sensitivity of PVDF-PEI/Anti-METH.

Infectious illnesses are on the rise in today's world, with serious consequences for animals, plants, and humans. Several infections, including the human immunodeficiency virus, affect a large number of individuals in various countries, particularly in the poorer portions of contemporary society, and continue to cause a variety of health problems. Viruses are tiny parasitic organisms. They are infectious agents that can only reproduce within a live cell of an organism. Viruses may infect any living organism. For clinical pointof- care applications, early detections for harmful agents such as bacteria, viruses are critical. The possibility of worldwide epidemics as a result of viral propagation emphasizes the importance of creating speedy, precise, and sensitive early detection systems. Furthermore, because certain viruses have a long latent phase and can evolve from one person to another, early detection during the incubation period is critical for improving recovery rates and avoiding pandemics. Nowadays, there has been various bio-based detection systems that have rapid reaction times, user-friendly, cost-effective, and repeatable. In this review, biological molecule-based detection technologies which focus on virus analysis are examined.