Electrochemical biosensors based on Ti3C2Tx MXene: future perspectives for on-site analysis

MXenes are recently developed two-dimensional layered materials composed of early transition metal carbides and/or nitrides that provide unique characteristics for biosensor applications. This review presents the recent progress made on the usage and applications of MXenes in the field of electrochemical biosensors, including microfluidic biosensors and wearable microfluidic biosensors, and highlights the challenges with possible solutions and future needs. The multilayered configuration and high conductivity make these materials as an immobilization matrix for the biomolecule immobilization with activity retention and to be explored in the fabrication of electrochemical sensors, respectively. First, how the MXene nanocomposite as an electrode modifier affects the sensing performance of the electrochemical biosensors based on enzymes, aptamer/DNA, and immunoassays is well described. Second, recent developments in MXene nanocomposites as wearable biosensing platforms for the biomolecule detection are highlighted. This review pointed out the future concerns and directions for the use of MXene nanocomposites to fabricate advanced electrochemical biosensors with high sensitivity and selectivity. Specifically, possibilities for developing microfluidic electrochemical sensors and wearable electrochemical microfluidic sensors with integrated biomolecule detection are emphasized.     

FET‐Based Chemical Sensor Systems Fabricated with Standard Technologies

Miniaturized solid‐state ion sensors based on field‐effect transistors on silicon can take advantage of the capabilities of microelectronics and microsystems technology for the integration of combined functionalities. Optimized solid‐state chemical sensors usually require specific materials and fabrication processes. However, if standard fabrication processes can be used, integrated chemical sensor systems can be developed in a shorter time and in a cost effective way. We show that, for applications in which a long operating time is not required, such as in disposable biomedical sensors, good integrated sensor systems can be fabricated with standard materials and processes. Specific examples are presented, such as multisensor systems, sensors with integrated signal‐processing circuits and sensors with particle manipulation electrodes.     

Recent advances on the development of graphene-based field-effect transistors,electrochemical biosensors and electrochemiluminescence biosensors

Graphene, a honeycomb lattice of carbon material with single-atom-layer structure, demonstrates extraordinary mechanical, thermal, chemical and electronic properties. Thus, it has sparked tremendous interests in various fields, such as energy storage and conversion devices, field-effect transistors (FET), chemical sensors and biosensors. In this review, we will first focus on the synthesis method of graphene and the fabrication strategy of graphene-based materials. Subsequently, the construction of graphene-based biosensors are introduced, in which three kinds of biosensors are discussed in details, including the FET, electrochemical biosensors and electrochemiluminescence (ECL) biosensors. The performances of the state-of-the-art biosensors on the detection of biomolecules are also displayed. Finally, we also highlight some critical challenges remain to be solved and the development in this field for further research.     

Recent advances in the application of nanomaterials in enzymatic glucose sensors

Due to the critical role of glucose level in the diagnosis and treatment of diabetes, as well as the increasing number of diabetics, there is an overwhelming demand for developing glucose sensors. It is well acknowledged that these sensors, especially those based on glucose oxidase, have played an important role in blood glucose detection. Inspired by the attractive properties, nanomaterials, especially nanostructured carbon and metal/metal oxides, have been extensively explored to develop enzymatic glucose sensors with high sensitivity, fast response time, and satisfied stability. In this review, a brief history of glucose biosensors is firstly presented. Furthermore, we discuss the currently available fabrication possesses in the field of enzymatic glucose biosensors based on nanomaterials, focusing on the carbon-based, metal-based, and metal oxides-based nanocomposites. What is more, we discuss the challenges and attempt to give an outlook on the possible further developments.     

Multiplexed inkjet functionalization of silicon photonic biosensors

The transformative potential of silicon photonics for chip-scale biosensing is limited primarily by the inability to selectively functionalize and exploit the extraordinary density of integrated optical devices on this platform. Silicon biosensors, such as the microring resonator, can be routinely fabricated to occupy a footprint of less than 50 × 50 μm; however, chemically addressing individual devices has proven to be a significant challenge due to their small size and alignment requirements. Herein, we describe a non-contact piezoelectric (inkjet) method for the rapid and efficient printing of bioactive proteins, glycoproteins and neoglycoconjugates onto a high-density silicon microring resonator biosensor array. This approach demonstrates the scalable fabrication of multiplexed silicon photonic biosensors for lab-on-a-chip applications, and is further applicable to the functionalization of any semiconductor-based biosensor chip.     

基于导电聚吡咯生物电化学传感器的研究进展

导电聚合物具有良好的导电性能,可以作为分子导线使电子在生物活性物质与电极间直接传递,是构建生物传感器的一种新型材料.聚吡咯(PPy)具有导电性、生物相容性、易固定等特点,在传感器中用于固定生物活性物质有着良好的应用前景.该文简要介绍了导电聚吡咯的合成方法及掺杂机理,重点评述了聚吡咯用于固定生物活性物质构建生物传感器的多...     

Conducting polymer composites with graphene for use in chemical sensors and biosensors

This review (with 79 references) summarizes the recent work on the development of chemical sensors and biosensors based on the use of composites made from conducting polymers (CPs) and graphene. Owing to the unique electrical, mechanical, optical, chemical and structural properties of CP and graphene, these kinds of composites have generated increasing interest in senor field. In this review, we first discuss methods for preparation of CP/GE composites by chemical, electrochemical, or physical methods including electrostatic interactions. We then cover aspects of the fabrication of modified electrodes and the performance of respective sensors with electrochemical, electronic or optical signal transduction. We then discuss sensors for the determination of inorganic and organic species, gases and vapors. We also review the state of the art in respective biosensors for hydrogen peroxide and glucose, for oligomers (DNA, RNA, and aptamers), for biogenic amines, NAD^+/NADH, cytochromes and the like, and in immunosensors. Finally, the perspective and current challenges of CP/GE composites for use in (bio)sensors are outlooked.

Nanowire‐Based Electrochemical Biosensors

We review recent advances in biosensors based on one‐dimensional (1‐D) nanostructure field‐effect transistors (FET). Specifically, we address the fabrication, functionalization, assembly/alignment and sensing applications of FET based on carbon nanotubes, silicon nanowires and conducting polymer nanowires. The advantages and disadvantages of various fabrication, functionalization, and assembling procedures of these nanosensors are reviewed and discussed. We evaluate how they have been used for detection of various biological molecules and how such devices have enabled the achievement of high sensitivity and selectivity with low detection limits. Finally, we conclude by highlighting some of the challenges researchers face in the 1‐D nanostructures research arena and also predict the direction toward which future research in this area might be directed.     

Natural and artificial ion channels for biosensing platforms

The single-molecule selectivity and specificity of the binding process together with the expected intrinsic gain factor obtained when utilizing flow through a channel have attracted the attention of analytical chemists for two decades. Sensitive and selective ion channel biosensors for high-throughput screening are having an increasing impact on modern medical care, drug screening, environmental monitoring, food safety, and biowarefare control. Even virus antigens can be detected by ion channel biosensors. The study of ion channels and other transmembrane proteins is expected to lead to the development of new medications and therapies for a wide range of illnesses. From the first attempts to use membrane proteins as the receptive part of a sensor, ion channels have been engineered as chemical sensors. Several other types of peptidic or nonpeptidic channels have been investigated. Various gating mechanisms have been implemented in their pores. Three technical problems had to be solved to achieve practical biosensors based on ion channels: the fabrication of stable lipid bilayer membranes, the incorporation of a receptor into such a structure, and the marriage of the modified membrane to a transducer. The current status of these three areas of research, together with typical applications of ion-channel biosensors, are discussed in this review.     

Application of MXene in Electrochemical Sensors: A Review

Electroanalysis has obtained considerable progress over the past few years, especially in the field of electrochemical sensors. Broadly speaking, electrochemical sensors include not only conventional electrochemical biosensors or non-biosensors, but also emerging electrochemiluminescence (ECL) sensors and photoelectrochemical (PEC) sensors which are both combined with optical methods. In addition, various electrochemical sensing devices have been developed for practical purposes, such as multiplexed simultaneous detection of disease-related biomarkers and non-invasive body fluid monitoring. For the further performance improvement of electrochemical sensors, material is crucial. Recent years, a kind of two-dimensional (2D) nanomaterial MXene containing transition metal carbides, nitrides and carbonitrides, with unique structural, mechanical, electronic, optical, and thermal properties, have attracted a lot of attention form analytical chemists, and widely applied in electrochemical sensors. Here, we reviewed electrochemical sensors based on MXene from Nov. 2014 (when the first work about electrochemical sensor based on MXene published) to Mar. 2021, dividing them into different types as electrochemical biosensors, electrochemical non-biosensors, electrochemiluminescence sensors, photoelectrochemical sensors and flexible sensors. We believe this review will be of help to those who want to design or develop electrochemical sensors based on MXene, hoping new inspirations could be sparked.     

Silicon nanowire biosensor and its applications in disease diagnostics: A review

Over the past decade, silicon nanowire (SiNW) biosensors have been studied for the detection of biological molecules as highly sensitive, label-free, and electrical tools. Herein we present a comprehensive review about the fabrication of SiNW biosensors and their applications in disease diagnostics. We discuss the detection of important biomarkers related to diseases including cancer, cardiovascular diseases, and infectious diseases. SiNW biosensors hold great promise to realize point-of-care (POC) devices for disease diagnostics with potential for miniaturization and integration.     

Molekül‐Detektive. Biosensoren

Biosensors are analytical devices incorporating biological material (receptor) intimately associated with or integrated within a physicochemical transducer. Advantages are the high selectivity for analyte detection. Examples given comprise the very successful commercial blood glucose biosensors made for the self‐control by the diabetic patients. Other biosensors are part of an analytic system, including the sensor chips of surface plasmon resonance or interferometry based devices, piezoelectric or reflectometric sensors capable of direct measurement of mass changes, and thermometric and other reagentless sensors. The development of nanotubes‐based devices allows for significant enhancment of the signal‐tonoise ratio of the biosensors. A milestone on the way towards miniaturization and parallelization of biosensors is the recently developed and prize‐winning electronic DNA chip.     

Selective patterning of Si-based biosensor surfaces using isotropic silicon etchants

Ultra-sensitive, label-free biosensors have the potential to have a tremendous impact on fields like medical diagnostics. For the majority of these Si-based integrated devices, it is necessary to functionalize the surface with a targeting ligand in order to perform specific biodetection. To do this, silane coupling agents are commonly used to immobilize the targeting ligand. However, this method typically results in the bioconjugation of the entire device surface, which is undesirable. To compensate for this effect, researchers have developed complex blocking strategies that result in selective patterning of the sensor surface. Recently, silane coupling agents were used to attach biomolecules to the surface of silica toroidal biosensors integrated on a silicon wafer. Interestingly, only the silica biosensor surface was conjugated. Here, we hypothesize why this selective patterning occurred. Specifically, the silicon etchant (xenon difluoride), which is used in the fabrication of the biosensor, appears to reduce the efficiency of the silane coupling attachment to the underlying silicon wafer. These results will enable future researchers to more easily control the bioconjugation of their sensor surfaces, thus improving biosensor device performance.     

Selective in situ functionalization of biosensors on LOC devices using laminar co-flow

Many applications involving lab-on-a-chip (LOC) devices are prevented from entering the market because of difficulties to achieve mass production and impart suitable properties allowing long-term storage. To integrate biosensors on these microfluidic chips, one of the main restrictions is the fabrication and stability of the molecular modifications that must be performed on the surfaces of the sensors for a given application. The complexity of the problem increases exponentially when the LOC integrates several of these sensors. Here we present a system based on laminar co-flow to perform an on-chip selective surface bio-functionalization of LOC-integrated sensors. This method has the advantage that the surface modification protocols are performed in situ before analyte detection. This approach reduces the burdens during LOC fabrication, keeping the required reagents stored outside of the detection structure in suitable wet conditions. The proof of concept is demonstrated through an optical characterization followed by electronic detection based on a novel differential impedance measurement setup. The system can be easily scaled to incorporate several sensors with distinct biosensing targets in a single chip.     

Electrochemical Aptasensors for Biological and Chemical Analyte Detection

Aptamers are short length, single-stranded DNA or RNA affinity molecules which interact with any desired targets such as biomarkers, cells, biological molecules, drugs or chemicals with high sensitivity. They have been extensively employed for medical applications due to having more advantages than the antibodies such as easier preparation and modification, higher stability, lower batch-to-batch variability and cost. Moreover, aptamers can be easily integrated efficiently with sensors, biosensors, actuators and other devices. In this review article, different applications of aptamers for biological and chemical molecules detection within the scope of electrochemical methods were presented with recent studies. In addition, the present status and future perspectives for highly-effective aptasensors for specific and selective analyte detection were discussed. As in stated throughout the review, combining of extraordinary properties of aptamers with the electrochemical-based biosensors could have improved the sensitivity of the assay and reduced limit of detection.     

Carbon nanomaterials and metallic nanoparticles-incorporated electrochemical sensors for small metabolites: Detection methodologies and applications

Detection of small metabolite biomarkers at different concentrations could be powerfully used for disease diagnosis and progression. To enhance detection capabilities, nanomaterials possessing excellent optical and electrochemical properties have been integrated into a wide range of sensing or detection platforms. This review will highlight recent developments in creating electrochemical sensors alongside biosensors using carbon nanomaterials and metallic nanoparticles that target small metabolites. Moreover, electrochemical sensors having different detection strategies toward metabolites (such as amino acids, amino acid–derived neurotransmitters, vitamins, adenosine triphosphate, and purine derivatives) will be discussed. Finally, certain challenging issues and future aspects of nanomaterials-integrated electrochemical sensors for small metabolites will be discussed.     

The impact of drying phenomena and heat treatment on the structure of porous silicon

Porous silicon (PS) has received a great deal of attention due to its light emitting properties. This characteristic has led to a wide range of applications (optoelectronic devices, physical and chemical sensors, solar cells??). Indeed, this material is a good candidate for improving the ratio quality/price of solar cells. Its fabrication needs anodisation of single crystalline silicon in a mixture of HF/methanol solution. In order to simulate the different steps needed to ??develop?? the solar cells, PS layers (single or two layers) were subjected to different annealing. In this article, we discuss the influence of drying and annealing on the morphology of PS. SEM observations and gravimetric measurements are reported.     

A Review on the Effects of Introducing CNTs in the Modification Process of Electrochemical Sensors

This review summarizes some developments in the fabrication of modified sensors and biosensors through the incorporating the carbon nanotubes (CNTs) in their modification ingredients. A large number of papers have paid attention towards the application of carbon nanotubes (CNTs) as electrode constituents and studied its electrochemical behavior. Here, we survey the achievements in the detection of various substances with high selectivity and sensitivity provided using CNTs based electrodes. Moreover, modified electrodes by CNTs have demonstrated the electrocatalytic features and higher sensitivity in detection of analytes. The improved characteristics arises from the large surface area and good conductivity of CNTs. However, it should be considered that the use of single walled carbon nanotubes (SWCNTs) or multi‐walled carbon nanotubes (MWCNTs), the presence of impurities, and the chemical procedures adopted are effective on the performance of the modified sensors.     

Recent Progress on Highly Selective and Sensitive Electrochemical Aptamer-based Sensors

Highly selective, sensitive, and stable biosensors are essential for the molecular level understanding of many physiological activities and diseases. Electrochemical aptamer-based (E-AB) sensor is an appealing platform for measurement in biological system, attributing to the combined advantages of high selectivity of the aptamer and high sensitivity of electrochemical analysis. This review summarizes the latest development of E-AB sensors, focuses on the modification strategies used in the fabrication of sensors and the sensing strategies for analytes of different sizes in biological system, and then looks forward to the challenges and prospects of the future development of electrochemical aptamer-based sensors.