Advanced growth of 2D MXene for electrochemical sensors

Revolutionizing human healthcare with wearable sensors for monitoring human strain

With the rapid advancements in wearable sensor technology, healthcare is witnessing a transformative shift towards personalized and continuous monitoring. Wearable sensors designed for tracking human strain offer promising applications in rehabilitation, athletic performance, occupational health, and early disease detection. Recent advancements in the field have centered on the design optimization and miniaturization of wearable biosensors. Wireless communication technologies have facilitated the simultaneous, non-invasive detection of multiple analytes with high sensitivity and selectivity through wearable biosensors, significantly enhancing diagnostic accuracy. This review meticulously chronicles noteworthy advancements in wearable sensors tailored for healthcare and biomedical applications, spanning the current market landscape, challenges faced, and prospective trends, including multifunctional smart wearable sensors and integrated decision-support systems. The domain of flexible electronics has witnessed substantial progress over the past decade, particularly in flexible strain sensors, which are crucial for contemporary wearable and implantable devices. These innovations have broadened the scope of applications in human health monitoring and diagnostics. Continuous advancements in novel materials and device architectural methodologies aim to expand the utility of these sensors while meeting the increasingly stringent demands for enhanced sensing performance. This review explores the diverse array of wearable sensors-from piezoelectric, piezoresistive, and capacitive sensors to advanced optical and bioimpedance sensors-each distinguished by unique material properties and functionalities. We analyzed these technologies' sensitivity, accuracy, and response time, which were crucial for reliably capturing strain metrics in dynamic, real-world conditions. Quantitative performance comparisons across various sensor types highlighted their relative effectiveness, strengths, and limitations regarding detection precision, durability, and user comfort. Additionally, we discussed the current challenges in wearable sensor design, including energy efficiency, data transmission, and integration with machine learning models for enhanced data interpretation. Ultimately, this review emphasized the revolutionary potential of wearable strain sensors in advancing preventative healthcare and enabling proactive health management, ushering in an era where real-time health insights could lead to more timely interventions and improved health outcomes.

MXene-rGO nanocomposite based electrochemical immunosensor for detection of endosulfan - An organochlorine pesticide

Endosulfan (Ed), a widely used organochlorine pesticide, is classified as a persistent organic pollutant (POP). Its long half-life, resistance to degradation, and bioaccumulation in the food chain contaminates soil, water, and air. Such widespread environmental damage triggers monitoring its levels for ensuring compliance with safety regulations and protecting public health. In the current work, Ed was chemically altered and coupled with a carrier protein to elicit an immunological response. The purified in-house generated antibodies against Ed (Ed-Ab) were characterized by sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE). MXene, a class of 2D inorganic compounds, is known to depict significant optoelectrical potential. Herein, we have synthesized a novel nanocomposite of MXene and reduced graphene oxide (rGO). For designing the MXene-rGO biosensor, Ed-Ab were combined with the nanocomposite post characterization by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR). Using the differential pulse voltammetry (DPV), electrochemical parameters such as pH, temperature, scan rate and response time of the electrode were evaluated. The fabricated electro-immunosensor was employed for the detection of endosulfan wherein the limit of detection (LOD) for Ed was determined to be 0.497 ppt with a linear range of 0.1 ppt-1 ppm. The composed electrode's working efficacy and sensitivity against similar cross-reactive pesticides was also determined. The MXene-rGO based nanocomposite depicted potential for determination of Ed traces in environmental samples.

Holistic insights into carbon nanotubes and MXenes as a promising route to bio-sensing applications

Essential biosensor use has become increasingly important in drug discovery and recognition, biomedicine, food safety, security, and environmental research. It directly contributed to the development of specialized, reliable diagnostic instruments known as biosensors, which use biological sensing components. Traditional biosensors have poor performance, so scientists need to develop advanced biosensors with promising selectivity, sensitivity, stability, and reusability. These are all parameter modifications associated with the characteristics of the sensing material. Carbon nanotubes (CNTs) and MXenes are promising as targeted sensing agents in advanced functional materials because of their promising chemical and physical properties and limited toxic effects. Based on available data and sensing performance, MXene is better for biosensing applications than CNTs. Because of their large specific surface area (SSA), superior electrical conductivity, and adaptable surface chemistry that facilitates simple functionalization and robust interactions with biomolecules, MXenes are typically regarded as the superior option for biosensors. Additionally, because of their hydrophilic nature, they are more suited to biological settings, which increases their sensitivity and efficacy in identifying biological targets. MXenes are more suitable for biosensing applications due to their versatility and compatibility with aquatic environments, even if CNTs have demonstrated stability and muscular mechanical strength. However, MXenes offer better thermal stability, which is crucial for applications in diverse temperature environments. This study reviews and compares the biosensing capabilities, synthesis methods, unique properties, and toxicity of CNTs and MXenes. Both nanomaterials effectively detect various pollutants in food, biological substances, and human bodies, making them invaluable in environmental monitoring and medical diagnostics. In conclusion, CNTs work better for biosensors that must be strong, flexible, and long-lasting under different conditions. MXenes, on the other hand, work better when chemical flexibility and compatibility with wet environments are essential.

An electrochemical point-of-care testing device for specific diagnosis of the albinism biomarker based on paradigm shift designs

L-tyrosine is a recognized biomarker of albinism, whose endogenous level in human bodies is directly linked to melanin synthesis while no attention has been paid to its specific diagnosis. To this end, we have developed an electrochemical point-of-care testing device based on a molecularly imprinted gel prepared by a universal paradigm shift design to achieve the enhanced specific recognition of the L-tyrosine. Interestingly, this theoretically optimized molecularly imprinted gel validates the recognition pattern of L-tyrosine and optimizes the structure of the polymer itself with the aid of computational chemistry. Besides, modified extended-layer MXene and Au nanoclusters have significantly improved the sensing activity. As a result, the linear diagnostic range of this electrochemical point-of-care testing device for L-tyrosine is 0.1-100 μM in actual human fluids, which fully covers the L-tyrosine levels of healthy individuals and people with albinism. The diagnosis is completed in 90 s and then the results are transmitted by Bluetooth low energy to the smart mobile terminal. Therefore, we are convinced that this electrochemical point-of-care testing device is a promising tool in the future smart medical system.

A novel molecularly imprinted electrochemical sensor based on quasi-three-dimensional nanomaterials Nb2CTx/AgNWs for specific detection of sulfadiazine

A novel molecularly imprinted electrochemical sensor (MIECS) was constructed for the specific detection of sulfadiazine (SDZ) in food. Niobium carbide (Nb2CTx) as a typical two-dimensional lamellar nanomaterial has good electrical conductivity and unique structure, which was assembled with one-dimensional silver nanowires (AgNWs) to form quasi-three-dimensional composite nanomaterials (Nb2CTx/AgNWs). As spacer material, AgNWs prevented the aggregation of Nb2CTx and the collapse of Nb2CTx layers. At the same time, a fast electron transport channel was constructed through the synergistic effect between nanomaterials the two. The Nb2CTx/AgNWs realized the enhancement of electrical signals. Molecularly imprinted polymers (MIPs) endowed the sensor with selectivity, achieving the specific detection of sulfadiazine. Under the optimal experimental conditions, the method has a wide linear range (1 × 10-8-1 × 10-4 mol L-1) and a low limit of detection (1.30 × 10-9 mol L-1). The sensor was used to detect sulfadiazine in pork, chicken, and feed samples, and the recovery was 82.61-94.87%. The results were in good agreement with the HPLC results, which proved the accuracy and practicability of the method.

A high-sensitivity flexible bionic tentacle sensor for multidimensional force sensing and autonomous obstacle avoidance applications

Bionic tentacle sensors are important in various fields, including obstacle avoidance, human‒machine interfaces, and soft robotics. However, most traditional tentacle sensors are based on rigid substrates, resulting in difficulty in detecting multidirectional forces originating from the external environment, which limits their application in complex environments. Herein, we proposed a high-sensitivity flexible bionic tentacle sensors (FBTSs). Specifically, the FBTS featured an ultrahigh sensitivity of 37.6 N-1 and an ultralow detection limit of 2.4 mN, which benefited from the design of a whisker-like signal amplifier and crossbeam architecture. Moreover, the FBTS exhibited favorable linearity (R2 = 0.98) and remarkable durability (more than 5000 cycles). This was determined according to the improvement in the uniformity of the sensing layer through a high-shear dispersion process. In addition, the FBTS could accurately distinguish the direction of external stimuli, resulting in the FBTS achieving roughness recognition, wind speed detection and autonomous obstacle avoidance. In particular, the ability of autonomous obstacle avoidance was suitably demonstrated by leading a bionic rat through a maze with the FBTS. Notably, the proposed FBTS could be widely applied in tactile sensing, orientation perception, and obstacle avoidance.

The potential of MXene-based materials in fluorescence-based sensing/biosensing of ionic and organic contaminants in environment and food samples: Recent advancements and challenges

MXenes belong to one of the recently developed advanced materials with tremendous potential for diverse sensing applications. To date, various types of MXene-based materials have been developed to generate direct/indirect ultrasensitive sensing signals against various forms of analytes via fluorescence quenching or enhancement. In this work, the fluorescence sensing/biosensing capabilities of the MXene-based materials have been explored and evaluated against a list of ionic/emerging pollutants in environment and food matrices. The suitability of an MXene-based sensing approach is also validated through the assessment of the performance based on the basic quality assurance parameters, e.g., limit of detection (LOD), sensing range, and response time. Accordingly, the best performing MXene-based materials are selected and recommended for the given target(s) to help facilitate their scalable applications under real-world conditions.

Electrochemical biosensor based on the integration of maple leaf-like gold nanocrystal and truncated aptamer for detection of α-amanitin with high sensitivity, selectivity and rapidity

This study reports the fabrication of three-dimensional gold nanocrystals as sensing material in the presence of l-glutathion and high-performance aptamer with 20 bases of α-amanitin via truncation and optimization of along aptamer. The resulting maple leaf-like gold nanocrystal (ML-Au) exhibits an improved catalytic activity due to more exposed high-index facets. The use of truncated aptamer increases the sensitivity by 15 times and reduces the reaction time by two times compared with those of original aptamer. An α-amanitin electrochemical biosensor constructed by integrating ML-Au nanocrystals with truncated aptamer exhibits high sensitivity, selectivity and rapidity. An increase of the α-amanitin concentration in the range of 1 × 10-14-1 × 10-9 M causes a linear decrease in the amperometric current with a limit of detection of 2.9 × 10-15 M (S/N = 3). The proposed analytical method is satisfactorily used for electrochemical sensing of α-amanitin in urine and wild mushroom samples.

Miniaturized MXene-based electrochemical biosensors for virus detection

The timely control of infectious diseases can prevent the spread of infections and mitigate the significant socio-economic damage witnessed during recent pandemics. Diagnostic methods play a significant role in detecting highly contagious agents, such as viruses, to prevent further transmission. The emergence of advanced point-of-care techniques offers several advantages over conventional approaches for detecting infectious agents. These techniques are highly sensitive, rapid, can be miniaturized, and are cost-effective. Recently, MXene-based 2D nanocomposites have proven beneficial for fabricating electrochemical biosensors due to their suitable electrical, optical, and mechanical properties. This article covers electrochemical biosensors based on MXene nanocomposite for the detection of viruses, along with the associated challenges and future possibilities. Additionally, we highlight various conventional techniques for the detection of infectious agents, discussing their pros and cons. We delve into the challenges faced during the fabrication of MXene-based biosensors and explore future endeavors. It is anticipated that the information presented in this work will pave the way for the development of Point-of-Care (POC) devices capable of sensitive and selective virus detection, enhancing preparedness for ongoing and future pandemics.

2D MXene-Based Nanoscale Materials for Electrochemical Sensing Toward the Detection of Hazardous Pollutants: A Perspective

MXenes (Mn+1XnTx), a subgroup of 2-dimensional (2D) materials, specifically comprise transition metal carbides, nitrides, and carbonitrides. They exhibit exceptional electrocatalytic and photocatalytic properties, making them well-suited for the detection and removal of pollutants from aqueous environments. Because of their high surface area and remarkable properties, they are being utilized in various applications, including catalysis, sensing, and adsorption, to combat pollution and mitigate its adverse effects. Different characterization techniques like XRD, SEM, TEM, UV-Visible spectroscopy, and Raman spectroscopy have been used for the structural elucidation of 2D MXene. Current responses against applied potential were measured during the electrochemical sensing of the hazardous pollutants in an aqueous system using a variety of electroanalytical techniques, including differential pulse voltammetry, amperometry, square wave anodic stripping voltammetry, etc. In this review, a comprehensive discussion on structural patterns, synthesis, properties of MXene and their application for electrochemical detection of lethal pollutants like hydroquionone, phenol, catechol, mercury and lead, etc. are presented. This review will be helpful to critically understand the methods of synthesis and application of MXenes for the removal of environmental pollutants.

Electrochemical sensing mechanisms of neonicotinoid pesticides and recent progress in utilizing functional materials for electrochemical detection platforms

The excessive residue of neonicotinoid pesticides in the environment and food poses a severe threat to human health, necessitating the urgent development of a sensitive and efficient method for detecting trace amounts of these pesticides. Electrochemical sensors, characterized by their simplicity of operation, rapid response, low cost, strong selectivity, and high feasibility, have garnered significant attention for their immense potential in swiftly detecting trace target molecules. The detection capability of electrochemical sensors primarily relies on the catalytic activity of electrode materials towards the target analyte, efficient loading of biomolecular functionalities, and the effective conversion of interactions between the target analyte and its receptor into electrical signals. Electrode materials with superior performance play a crucial role in enhancing the detection capability of electrochemical sensors. With the continuous advancement of nanotechnology, particularly the widespread application of novel functional materials, there is paramount significance in broadening the applicability and expanding the detection range of pesticide sensors. This comprehensive review encapsulates the electrochemical detection mechanisms of neonicotinoid pesticides, providing detailed insights into the outstanding roles, advantages, and limitations of functional materials such as carbon-based materials, metal-organic framework materials, supramolecular materials, metal-based nanomaterials, as well as molecular imprinted materials, antibodies/antigens, and aptamers as molecular recognition elements in the construction of electrochemical sensors for neonicotinoid pesticides. Furthermore, prospects and challenges facing various electrochemical sensors based on functional materials for neonicotinoid pesticides are discussed, providing valuable insights for the future development and application of biosensors for simplified on-site detection of agricultural residues.

Recent advances in photoelectrochemical platforms based on porous materials for environmental pollutant detection

Human health and ecology are seriously threatened by harmful environmental contaminants. It is essential to develop efficient and simple methods for their detection. Environmental pollutants can be detected using photoelectrochemical (PEC) detection technologies. The key ingredient in the PEC sensing system is the photoactive material. Due to the unique characteristics, such as a large surface area, enhanced exposure of active sites, and effective mass capture and diffusion, porous materials have been regarded as ideal sensing materials for the construction of PEC sensors. Extensive efforts have been devoted to the development and modification of PEC sensors based on porous materials. However, a review of the relationship between detection performance and the structure of porous materials is still lacking. In this work, we present an overview of PEC sensors based on porous materials. A number of typical porous materials are introduced separately, and their applications in PEC detection of different types of environmental pollutants are also discussed. More importantly, special attention has been paid to how the porous material's structure affects aspects like sensitivity, selectivity, and detection limits of the associated PEC sensor. In addition, future research perspectives in the area of PEC sensors based on porous materials are presented.

2D MXenes and their composites; design, synthesis, and environmental sensing applications

Novel 2D layered MXene materials were first reported in 2011 at Drexel University. MXenes are widely used in multidisciplinary applications due to their anomalous electrical conductivity, high surface area, and chemical, mechanical, and physical properties. This review summarises MXene synthesis and applications in environmental sensing. The first section describes different methods for MXene synthesis, including fluorinated and non-fluorinated methods. MXene's layered structure, surface terminal groups, and the space between layers significantly impact its properties. Different methods to separate different MXene layers are also discussed using various intercalation reagents and commercially synthesized MXene without compromising the environment. This review also explains the effect of MXene's surface functionalization on its characteristics. The second section of the review describes gas and pesticide sensing applications of Mxenes and its composites. Its good conductivity, surface functionalization with negatively charged groups, intrinsic chemical nature, and good mechanical stability make it a prominent material for room temperature sensing of environmental samples, such as polar and nonpolar gases, volatile organic compounds, and pesticides. This review will enhance the young scientists' knowledge of MXene-based materials and stimulate their diversity and hybrid conformation in environmental sensing applications.

Artificial neural network-facilitated V2C MNs-based colorimetric/fluorescence dual-channel biosensor for highly sensitive detection of AFB1 in peanut

In this work, V2C Mxene nano-enzyme materials (V2C MNs) with excellent peroxidase-like activity and fluorescence quenching performance were prepared, and it was modified using 6-carboxyfluorescein-labelled aptamers (ssDNA-FAM) to construct a novel dual-mode sensor V2C@ssDNA-FAM, with detection limits of 0.0477 ng mL-1 and 0.2789 ng mL-1 of fluorescence (linear range of 0.1-550 ng mL-1) and colorimetric (linear range of 1-1000 ng mL-1) modes, respectively. Meanwhile, an ANN intelligent detection platform has been constructed, which could automatically track and analyze the fluorescence and colorimetric signal of the detection system through machine learning and immediately obtain the AFB1 concentration, and the detection limits of the fluorescence (linear range of 0.1-500 ng mL-1) and colorimetric (linear range of 1-800 ng mL-1) channels of it were 0.0905 ng mL-1 and 0.6845 ng mL-1, respectively. The recovery rates of fluorescence, colorimetric sensing detection and ANN-assisted fluorescence and colorimetric sensing detection of real samples ranged from 95.40% to 101.76%. The method constructed in this work was superior to most existing literature reports and had great potential for application in the field of food quality testing.

Chitosan-Based Electrochemical Sensors for Pharmaceuticals and Clinical Applications

Chitosan (CTS), a biocompatible and multifunctional material derived from chitin, has caught researchers' attention in electrochemical detection due to its unique properties. This review paper provides a comprehensive overview of the recent progress and applications of CTS-based electrochemical sensors in the analysis of pharmaceutical products and other types of samples, with a particular focus on the detection of medicinal substances. The review covers studies and developments from 2003 to 2023, highlighting the remarkable properties of CTS, such as biocompatibility, chemical versatility, and large surface area, that make it an excellent candidate for sensor modification. Combining CTS with various nanomaterials significantly enhances the detection capabilities of electrochemical sensors. Various types of CTS-based sensors are analyzed, including those utilizing carbon nanomaterials, metallic nanoparticles, conducting polymers, and molecularly imprinted CTS. These sensors exhibit excellent sensitivity, selectivity, and stability, enabling the precise and reliable detection of medications. The manufacturing strategies used for the preparation of CTS-based sensors are described, the underlying detection mechanisms are elucidated, and the integration of CTS sensors with transducer systems is highlighted. The prospects of CTS-based electrochemical sensors are promising, with opportunities for miniaturization, simultaneous detection, and real-time monitoring applications.

MXenes and MXene-based materials for removal of pharmaceutical compounds from wastewater: Critical review

The rapid increase in the global population and its ever-rising standards of living are imposing a huge burden on global resources. Apart from the rising energy needs, the demand for freshwater is correspondingly increasing. A population of around 3.8 billion people will face water scarcity by 2030, as per the reports of the World Water Council. This may be due to global climate change and the deficiency in the treatment of wastewater. Conventional wastewater treatment technologies fail to completely remove several emerging contaminants, especially those containing pharmaceutical compounds. Hence, leading to an increase in the concentration of harmful chemicals in the human food chain and the proliferation of several diseases. MXenes are transition metal carbide/nitride ceramics that primarily structure the leading 2D material group. MXenes act as novel nanomaterials for wastewater treatment due to their high surface area, excellent adsorption properties, and unique physicochemical properties, such as high electrical conductivity and hydrophilicity. MXenes are highly hydrophilic and covered with active functional groups (i.e., hydroxyl, oxygen, fluorine, etc.), which makes them efficient adsorbents for a wide range of species and promising candidates for environmental remediation and water treatment. This work concludes that the scaling up process of MXene-based materials for water treatment is currently of high cost. The up-to-date applications are still limited because MXenes are currently produced mainly in the laboratory with limited yield. It is recommended to direct research efforts towards lower synthesis cost procedures coupled with the use of more environmentally friendly materials to avoid secondary contamination.