Improving Nonenzymatic Biosensing Performance of Electrospun Carbon Nanofibers decorated with Ni/Co Particles via Oxidation

Inbuilt self-cascade catalysis of the bimetal-confined structural nanozyme CoNi@CNTs-N/GO for increased bienzymatic activity and H2O2-free smartphone-based visual assay of total antioxidant capacity in foods

The level of total antioxidant capacity (TAC) reflects the overall ability of food to resist oxidative damage, maintain quality and nutritional stability. In this work, we pioneered a CoNi alloy-confined N-doped carbon nanozyme (CoNi@CNT-N/GO) with a self-cascade catalysis. Compared to other nanozymes, the synergistic effect of OXD and POD realized self-sustained generation of H2O2, eliminating the need of exogenous addition, and further decomposition of H2O2 into ·OH and oxidizes colorless 3,3',5,5'- tetramethylbenzidine (TMB) to blue oxTMB as an efficient catalyst. The integration of multiple components and the built-in unique mechanism enhance bienzymatic activity. A "Thing Identify" APP was utilized to construct a smartphone-based visualization platform, demonstrating satisfactory linearity (0.01-1.2 mM) and low detection limit (3.3 μM) in TAC detection of real-world foods. This platform yielded data comparable to those from commercially colorimetric kits. Overall, it proposes a novel idea for engineering multi-functional and non-additional H2O2 nanozymes in on-site food-quality monitoring.

Electrospun nanofibers and their application as sensors for healthcare

Electrospinning is a type of electrohydrodynamics that utilizes high-voltage electrostatic force to stretch a polymer solution into nanofibers under the influence of an electric field, with most of the fibers falling onto a collector. This technology is favored by researchers across various fields due to its simple and inexpensive device for producing nanofibers in a straightforward manner. Nanofibers prepared through electrospinning have a high specific surface area and high porosity. Electrospinning technology shows extensive potential, especially within biomedical sensors. This article provides a systematic overview of the factors influencing electrospinning, the parameters of the electrospinning process, the types of electrospun nanofibers, and the applications of electrospinning technology in the field of sensors, including wearable sensors, pressure sensors, and glucose sensors. The paper summarizes the research progress in this field and points out the direction of development for electrospinning technology, as well as the future challenges.

Aleem M, Gao H, Eissa NG, Elghamry I, Salim SA. Recent Progress of Polymer-Based Biosensors for Cancer Diagnostic Applications: Natural versus Synthetic Polymers

Early diagnosis of cancer can significantly contribute to improving therapeutic outcomes and enhancing survival rates for cancer patients. Polymer-based biosensors have emerged as a promising tool for cancer detection due to their high sensitivity, selectivity, and low cost. These biosensors utilize functionalized polymers in different parts of the body to detect cancer biomarkers in biological samples. This approach offers several advantages over traditional detection methods, including real-time monitoring and noninvasive detection while maintaining high sensitivity and accuracy. This review discusses recent advances in the development of polymer-based biosensors for cancer detection including their design, fabrication, and performance. The essential characteristics of biosensing devices are presented, along with examples for natural and synthetic polymers commonly utilized in biosensors. Furthermore, strategies employed to tailor polymers to improve biosensing applications and future perspectives for the application of polymer-based biosensors in cancer diagnosis are also highlighted. Integrating these advancements will illuminate the potential of polymer-based biosensors as transformative tools in the early detection and management of cancer.

Graphene-Based Electrochemical Biosensors for Breast Cancer Detection

Breast cancer (BC) is the most common cancer in women, which is also the second most public cancer worldwide. When detected early, BC can be treated more easily and prevented from spreading beyond the breast. In recent years, various BC biosensor strategies have been studied, including optical, electrical, electrochemical, and mechanical biosensors. In particular, the high sensitivity and short detection time of electrochemical biosensors make them suitable for the recognition of BC biomarkers. Moreover, the sensitivity of the electrochemical biosensor can be increased by incorporating nanomaterials. In this respect, the outstanding mechanical and electrical performances of graphene have led to an increasingly intense study of graphene-based materials for BC electrochemical biosensors. Hence, the present review examines the latest advances in graphene-based electrochemical biosensors for BC biosensing. For each biosensor, the detection limit (LOD), linear range (LR), and diagnosis technique are analyzed. This is followed by a discussion of the prospects and current challenges, along with potential strategies for enhancing the performance of electrochemical biosensors.

Development of Kovacs model for electrical conductivity of carbon nanofiber-polymer systems

This study develops a model for electrical conductivity of polymer carbon nanofiber (CNF) nanocomposites (PCNFs), which includes two steps. In the first step, Kovacs model is developed to consider the CNF, interphase and tunneling regions as dissimilar zones in the system. In the second step, simple equations are expressed to estimate the resistances of interphase and tunnels, the volume fraction of CNF and percolation onset. Although some earlier models were proposed to predict the electrical conductivity of PCNFs, developing of Kovacs model causes a better understanding of the effects of main factors on the nanocomposite conductivity. The developed model is supported by logical influences of all factors on the conductivity and by experimented conductivity of several samples. The calculations show good accordance to the experimented data and all factors rationally manage the conductivity of PCNFs. The highest conductivity of PCNF is gained as 0.019 S/m at the lowest ranges of polymer tunnel resistivity (ρ = 500 Ω m) and tunneling distance (d = 2 nm), whereas the highest levels of these factors (ρ > 3000 Ω m and d > 6 nm) cannot cause a conductive sample. Also, high CNF volume fraction, poor waviness, long and thin CNF, low "k", thick interphase, high CNF conduction, high percentage of percolated CNFs, low percolation onset and high interphase conductivity cause an outstanding conductivity in PCNF.

Simulation of electrical conductivity for polymer silver nanowires systems

A simple model is developed for the conductivity of polymeric systems including silver nanowires (AgNWs). This model reveals the effects of interphase thickness, tunneling distance, waviness and aspect ratio of nanowires, as well as effective filler volume fraction on the percolation and electrical conductivity of AgNW-reinforced samples. The validity of this model is tested by using the measured data from several samples. Based on this model, the conductivity calculations are in proper accordance with the measured values. A large network and a low percolation onset are produced by nanowires with a high aspect ratio developing the nanocomposite conductivity. The results also show that a thicker interphase expands the network, thereby increasing the electrical conductivity. Furthermore, non-waved AgNWs exhibit more conductivity compared to wavy nanowires. It is concluded that the surface energies of polymer medium and nanowires have no effect on the conductivity of samples. On the other hand, the volume fraction and aspect ratio of nanowires, in addition to the interphase thickness and tunneling distance have the greatest influences on the conductivity of nanocomposites.

Synergistic Effect of Composite Nickel Phosphide Nanoparticles and Carbon Fiber on the Enhancement of Salivary Enzyme-Free Glucose Sensing

An electrospinning method was used for the preparation of an in situ composite based on Ni₂P nanoparticles and carbon fiber (FC). The material was tested for the first time against direct glucose oxidation reaction. The Ni₂P nanoparticles were distributed homogeneously throughout the carbon fibers with a composition determined by thermogravimetric analysis (TGA) of 40 wt% Ni₂P and 60 wt% carbon fiber without impurities in the sample. The electrochemical measurement results indicate that the GCE/FC/Ni₂P in situ sensor exhibits excellent catalytic activity compared to the GCE/Ni₂P and GCE/FC/Ni₂P ex situ electrodes. The GCE/FC/Ni₂P in situ sensor presents a sensitivity of 1050 µAmM^-1cm^-2 in the range of 5-208 µM and a detection limit of 0.25 µM. The sensor was applied for glucose detection in artificial saliva, with a low interference observed from normally coexisting electroactive species. In conclusion, our sensor represents a novel and analytical competitive alternative for the development of non-enzymatic glucose sensors in the future.

A Review on Non-Enzymatic Electrochemical Biosensors of Glucose Using Carbon Nanofiber Nanocomposites

Diabetes mellitus has become a worldwide epidemic, and it is expected to become the seventh leading cause of death by 2030. In response to the increasing number of diabetes patients worldwide, glucose biosensors with high sensitivity and selectivity have been developed for rapid detection. The selectivity, high sensitivity, simplicity, and quick response of electrochemical biosensors have made them a popular choice in recent years. This review summarizes the recent developments in electrodes for non-enzymatic glucose detection using carbon nanofiber (CNF)-based nanocomposites. The electrochemical performance and limitations of enzymatic and non-enzymatic glucose biosensors are reviewed. Then, the recent developments in non-enzymatic glucose biosensors using CNF composites are discussed. The final section of the review provides a summary of the challenges and perspectives, for progress in non-enzymatic glucose biosensors.

Modeling of Electrical Conductivity for Polymer-Carbon Nanofiber Systems

There is not a simple model for predicting the electrical conductivity of carbon nanofiber (CNF)-polymer composites. In this manuscript, a model is proposed to predict the conductivity of CNF-filled composites. The developed model assumes the roles of CNF volume fraction, CNF dimensions, percolation onset, interphase thickness, CNF waviness, tunneling length among nanoparticles, and the fraction of the networked CNF. The outputs of the developed model correctly agree with the experimentally measured conductivity of several samples. Additionally, parametric analyses confirm the acceptable impacts of main factors on the conductivity of composites. A higher conductivity is achieved by smaller waviness and lower radius of CNFs, lower percolation onset, less tunnel distance, and higher levels of interphase depth and fraction of percolated CNFs in the nanocomposite. The maximum conductivity is obtained at 2.37 S/m by the highest volume fraction and length of CNFs.

Electrospun nanofiber-based glucose sensors for glucose detection

Diabetes is a chronic, systemic metabolic disease that leads to multiple complications, even death. Meanwhile, the number of people with diabetes worldwide is increasing year by year. Sensors play an important role in the development of biomedical devices. The development of efficient, stable, and inexpensive glucose sensors for the continuous monitoring of blood glucose levels has received widespread attention because they can provide reliable data for diabetes prevention and diagnosis. Electrospun nanofibers are new kinds of functional nanocomposites that show incredible capabilities for high-level biosensing. This article reviews glucose sensors based on electrospun nanofibers. The principles of the glucose sensor, the types of glucose measurement, and the glucose detection methods are briefly discussed. The principle of electrospinning and its applications and advantages in glucose sensors are then introduced. This article provides a comprehensive summary of the applications and advantages of polymers and nanomaterials in electrospun nanofiber-based glucose sensors. The relevant applications and comparisons of enzymatic and non-enzymatic nanofiber-based glucose sensors are discussed in detail. The main advantages and disadvantages of glucose sensors based on electrospun nanofibers are evaluated, and some solutions are proposed. Finally, potential commercial development and improved methods for glucose sensors based on electrospinning nanofibers are discussed.