A Review on Biosensors and Recent Development of Nanostructured Materials-Enabled Biosensors.

A sensor can be called ideal or perfect if it is enriched with certain characteristics viz., superior detections range, high sensitivity, selectivity, resolution, reproducibility, repeatability, and response time with good flow. Recently, biosensors made of nanoparticles (NPs) have gained very high popularity due to their excellent applications in nearly all the fields of science and technology. The use of NPs in the biosensor is usually done to fill the gap between the converter and the bioreceptor, which is at the nanoscale. Simultaneously the uses of NPs and electrochemical techniques have led to the emergence of biosensors with high sensitivity and decomposition power. This review summarizes the development of biosensors made of NPssuch as noble metal NPs and metal oxide NPs, nanowires (NWs), nanorods (NRs), carbon nanotubes (CNTs), quantum dots (QDs), and dendrimers and their recent advancement in biosensing technology with the expansion of nanotechnology.

Optimal sensing devices exhibit a combination of key performance attributes, including an extensive detection limit, exceptional selectivity, high sensitivity, consistent repeatability, precise measurement, and rapid response times with efficient analyte flow. In recent years, biosensing platforms incorporating nanoscale materials have garnered considerable attention due to their diverse applications across various scientific and technological domains. The integration of nanoparticles (NPs) in biosensor design primarily bridges the dimensional gap between the signal transduction element and the biological recognition component, both of which operate at nanometer scales. The synergistic combination of NPs with electrochemical techniques has facilitated the development of biosensors characterized by enhanced sensitivity and superior analyte discrimination capabilities. This comprehensive analysis examines the evolution and recent advancements in nanomaterial (NM)-based biosensors, encompassing an extensive array of nanostructures. These consists of one-dimensional nanostructures including carbon nanotubes (CNTs), nanowires (NWs), nanorods (NRs), and quantum dots (QDs), as well as noble metal and metal and metal oxide nanoparticles (NPs). The article examines how advancements in biosensing techniques across a range of applications have been fueled by the growth of nanotechnology. Researchers have significantly improved biosensor performance parameters by utilizing the distinct physiochemical properties of these NMs. The developments have increased the potential uses of nanobiosensors in a wide range of fields, from food safety and biodefense to medical diagnostics and environmental monitoring. The continuous developments in NM-based biosensors are the result of the integration of several scientific areas, such as analytical chemistry, materials science, and biotechnology. This interdisciplinary approach continues to drive innovations in sensor design, signal amplification strategies, and data analysis techniques, ultimately leading to more sophisticated and capable biosensing platforms. As the field progresses, challenges related to the scalability, reproducibility, and long-term stability of nanobiosensors are being addressed through innovative fabrication methods and surface modification techniques. These efforts aim to translate the promising results observed in laboratory settings into practical, commercially viable biosensing devices that can address real-world analytical challenges across various sectors.

Nanomaterials for Biosensors

Carbon nanotubes : their synthesis and integration into nanofabricated structures

A biosensor is a device developed from biological materials and transducers for the detection of analytes such as metabolites, pollutants, microbial load, etc., in which the biochemical signals are converted into physicochemical signals that can be easily measured. Most of the analytes are biological in nature, such as DNAs of bacteria or viruses, and proteins produced from the immune system (antibodies, antigens). Also, the analytes could be simple molecules like pollutants. Currently, nanotechnology plays a vital role in biosensor development. Nanostructured materials have gained significant attention owing to their distinct physicochemical properties due to the quantum size effects. These materials have shown extraordinary results in the improvement of biosensor's performance through new signal transduction technologies. Moreover, nanomaterials are promising candidates for sensing with high sensitivity and low detection limits. These materials support a large amount of bio-receptor units which can be immobilized in a smaller space. Several nanomaterials such as nanoparticles (NPs), nanotubes, nanorods (NRs), and nanowires (NWs) that are being used in bio-sensing, exhibit faster detection and reproducibility. Specifically, carbon nanotube (CNT), gold nanoparticles (AuNPs), magnetic NPs, and quantum dots (QDs), etc., have been investigated for sensing purposes. In this review, we provide a brief overview of biosensors, including general introduction and recent advances in bio-sensing strategies relating to the cross-disciplines of chemistry and biology. Also, we highlight some smart applications of bio-functional nanomaterials in ultrasensitive bioanalysis.

This paper reviews sensors with nano- and microscale dimensions used for diverse biological applications. A biosensor converts biological responses into electrical signals. In recent years, there have been significant advancements in the design and development of biosensors that generated a large spectrum of biosensor applications including healthcare, disease diagnosis, drug delivery, environmental monitoring, and water and food quality monitoring. There has been significant work to enhance the performance of biosensors by improving sensitivity, reproducibility, and sensor response time. However, a key challenge of these technologies is their ability to efficiently capture and transform biological signals into electric, optic, gravimetric, electrochemical, or acoustic signals. This review summarizes the working principle of a variety of biosensors in terms of their classification, design considerations, and diverse applications. Other lines of research highlighted in this paper are focused on the miniaturization of biosensing devices with micro and nano-fabrication technologies, and the use of nanomaterials in biosensing. Recently wearable sensors have had important applications such as monitoring patients with chronic conditions in home and community settings. This review paper mentions applications of wearable technology. Machine learning is shown to help discover new knowledge in the field of medical applications. We also review artificial intelligence (AI) and machine learning (ML)-based applications.

Nanomaterials are being increasingly used for the development of electrochemical DNA biosensors, due to the unique electrocatalytic properties found in nanoscale materials. They offer excellent prospects for interfacing biological recognition events with electronic signal transduction and for designing a new generation of bioelectronic devices exhibiting novel functions. In particular, nanomaterials such as noble metal nanoparticles (Au, Pt), carbon nanotubes (CNTs), magnetic nanoparticles, quantum dots and metal oxide nanoparticles have been actively investigated for their applications in DNA biosensors, which have become a new interdisciplinary frontier between biological detection and material science. In this article, we address some of the main advances in this field over the past few years, discussing the issues and challenges with the aim of stimulating a broader interest in developing nanomaterial-based biosensors and improving their applications in disease diagnosis and food safety examination.

WARNING : The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!

Carbon nanotubes (CNTs) have received impressive consideration as support materials of noble metal catalysts in heterogeneous catalysis due to their good mechanical strength, large surface area and good durability under harsh conditions. The interaction between CNTs and noble metal nanoparticles (NPs) gives an unusual unique microstructure properties and or modification of the electron density of the noble metal clusters, and enhances the catalytic activity. In this study, the MWCNTs were first treated with a mixture of concentrated sulfuric and nitric acid by sonication to improve its dispersibility and to introduce the carboxylic (-COOH) groups on CNTs surfaces. Gold nanoparticles (Au NPs) on multiwalled carbon nanotubes (MWCNTs) were synthesized by the deposition precipitation (DP) method as this method is simpler, low cost, and excellent method. Then, the effect of reducing agent (NaBH4) on gold distribution on the support of MWCNTs was also studied. Dispersion test, Fourier Transform Infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM) are all used to characterize the functionalized MWCNTs (fCNTs) and the Au NPs-fCNTs catalyst. There are three important peaks in functionalized MWCNTs which correspond to C=O, O-H, and C-O absorption peaks, as a result of the oxidation of COOH groups on the surface of CNTs. The absorption band at 1717 cm−1 is corresponded to C=O stretching of COOH, while the absorption bands at 3384 cm−1 and 1011cm−1 are associated with O–H bending and C–O stretching, respectively. Surface morphology of Au NPs-fCNTs R4 and Au NPs- fCNTs WR catalyst by FESEM showed that the Au NPs of 19.22 ± 2.33 nm and 23.05 ± 2.57 nm size were successfully deposited on CNTs, respectively.Carbon nanotubes (CNTs) have received impressive consideration as support materials of noble metal catalysts in heterogeneous catalysis due to their good mechanical strength, large surface area and good durability under harsh conditions. The interaction between CNTs and noble metal nanoparticles (NPs) gives an unusual unique microstructure properties and or modification of the electron density of the noble metal clusters, and enhances the catalytic activity. In this study, the MWCNTs were first treated with a mixture of concentrated sulfuric and nitric acid by sonication to improve its dispersibility and to introduce the carboxylic (-COOH) groups on CNTs surfaces. Gold nanoparticles (Au NPs) on multiwalled carbon nanotubes (MWCNTs) were synthesized by the deposition precipitation (DP) method as this method is simpler, low cost, and excellent method. Then, the effect of reducing agent (NaBH4) on gold distribution on the support of MWCNTs was also studied. Dispersion test, Fourier Transform Infrared spectro...

A biosensor is commonly defined as a device incorporating a bioreceptor connected to a transducer, which converts an observed response into a measurable signal proportional to analyte concentration which then is conveyed to a detector (Eggins, 1996). As demonstrated in Fig. 1, a biosensor consists of a bio-element and a sensor-element. A specific bio-element, including enzyme, antibody, microorganism, cell, and DNA, recognizes a specific analyte, and a sensor element transduces the change in the biomolecules into an electrical signal. Biosensors can be classified either by their bioreceptor or their transducer. Biosensors are known as enzymatic biosensors (enzymes), genosensors (DNAs), immunosensors (antibodies), etc. depending on the bioreceptors used. Biosensors can also be divided into several categories based on the transduction process, such as electrochemical, optical, piezoelectric, and thermal/calorimetric. Among these, electrochemical biosensors are the most widespread, numerous and successfully commercialized devices of biomolecular electronics (Dzyadevych et al., 2008). Much literature on carbon nanotube (CNT)-based biosensors has been published over the past several years because CNTs have the following advantages: (1) small size with large surface area, (2) high sensitivity, (3) fast response time, (4) enhanced electron transfer and (5) easy protein immobilization on CNT-modified electrodes, coupled with the fact that several methods have been developed (J. Wang & Musameh, 2003a; J. Wang et al., 2003b; Y. Saito et al., 1993). These properties make CNTs ideal for use in electrochemical biosensors and nanoscale electronic devices. Such potential applications would greatly benefit from CNTs in promoting the electron-transfer reaction of biomolecules, including catecholamine neurotransmitters (J. Wang et al., 2002a), cytochrome c (J. Wang et al., 2002b), ascorbic acid (Z. H. Wang et al., 2002), NADH (Musameh et al., 2002), and hydrazine compounds (Zhao et al., 2002). The insolubility of CNTs in most solvents is a major barrier for developing such CNT-based biosensing devices. Therefore, surface modification is necessary for CNT materials to be biocompatible and to improve solubility in common solvents and selective binding capability to biotargets. There are two main approaches for surface modification of CNTs: a non-covalent wrapping or adsorption and covalent chemical tethering. The non-covalent approach includes surfactant modification, polymer wrapping, and polymer absorption via various adsorption forces, such as van der Waals and π-stacking interactions. The advantage of non-covalent modification is that the structures and mechanical properties of CNTs remain intact.

The plasmon phenomenon is the driving force behind noble metal nanoparticle research. While some work synthesizing new kinds of particles is still performed, a wider range of opportunities is available if these nanoparticles’ self-assembly in solution and on substrates can be controlled. This text presents several such methodologies, describing each assembly process and characterizing the resulting structures. The selective, aqueous dimerization of gold bipyramids is the first study. These novel antennae are created by stabilizing the gold biypramid’s ligand shell, then linking the particles with amino acids. Because of the gold bipyramids’ monodispersity and the precision of the reaction, the assembly can be monitored to ensure high dimer yield. Gold nanorod alignment on, and by, a shallowly corrugated diblock copolymer thin film demonstrates the power of template assisted assembly. Controlling the alignment of the underlying film controls the gold nanorods’ alignment, yielding mesoscale structures with orientation dependent optical properties. With intentional design, other polymer substrates are used to construct gold bipyramid – silver nanosphere plasmonic heterostructures. With proper ligand-polymer interaction tailoring, this result demonstrates how this technique can rationally create almost any noble metal nanoparticle based structure. The nonlinear optical properties of these heterostructures are currently being investigated. These assemblies are all unique, and barely represent a fraction of what plasmonic nanoparticle assembly research can entail. Given polymer templates’ efficacy in controlling these particle’s deposition and alignment, a study of a diblock copolymer thin film’s swelling behavior is also contained in this work. By understanding and controlling the film’s surface morphologies, its efficacy for noble metal nanoparticle alignment can be determined. Gold nanoparticles are used to probe the chemical nature of diblock’s swollen surface, and concurrently demonstrate that it can align small, highly charged, plasmonic nanoparticles. Several attempts to synthesize solution-based plasmonic antennae and fluorophore hybrids are also described, resulting in an introduction to the realm of semiconductor nanocrystal synthesis. Although these gold bipyramid – water soluble quantum dot systems have not yet been achieved, with some refinement, such systems should be possible. Finally, following the theme of unexpected research directions, two collaborations are presented that utilized the nanoparticle synthesis and characterization skills required to perform the rest of this research.

Uniform, Scalable, High-Temperature Microwave Shock for Nanoparticle Synthesis through Defect Engineering

We have recently fabricated enzyme encapsulated CdTe quantum dot (QDs) hydrogels using the sol-gel method, a versatile way in the QD gel formation. The porous three dimensional QD hydrogel turned out to be an adequate encapsulation medium for enzymes and furthermore, the optoelectronic properties of the individual QDs were still retained in the QD hydrogels. The as-prepared enzyme-encapsulated QD hydrogel incorporated both a bio-catalysis unit and a fluorescence signaling unit, and was taken as a multi-functional platform in the development of optical biosensors.

Recently, the use of carbon nanotubes (CNTs) and fullerenes in the design of new biosensors have attracted great interest in the development of carbon nanomaterials. Due to the superior properties of CNTs and fullerenes, the use of sensor components allows the development of reliable, accurate and fast biosensors. Depending on the types of target molecules, the development and application areas of the sensors vary. This review summarizes the role of CNTs and fullerenes in the development of biosensors in different application areas. Considering the difference between other members of the nano-carbon family, we explain why CNTs are used more widely in biosensor applications and why fullerenes have high potentials in these areas of application. Moreover, we focused on investigating the function of these nano-carbons in the detection of various analytes in bio-sensing. By discussing the challenges and future expectations, we have put forward a perspective that may help synthesize advanced composites in the development of new generation designs in biosensor applications.

Photoelectrochemical (PEC) splitting water technology over the years has gradually matured, and now photoanodes loaded with nanoparticles (NPs) show excellent PEC performance. Each of the metal NPs has a different effect on the PEC performance of BiVO4. This work selected the noble metals Ag and Au to modify BiVO4 and study its PEC performance. After recombination, the photocurrent densities of Ag/BiVO4 and Au/BiVO4 photoanodes were 3.88 mA/cm2 and 1.61 mA/cm2 at 1.23 VRHE, which were 3.82 and 1.72 times that of pure BiVO4. The hydrogen evolution of pure BiVO4 is about 1.10 μmol·cm−2. Ag/BiVO4 and Au/BiVO4 contain 3.56 and 2.32 times pure BiVO4, respectively. Through the research, it was found that the composite noble metal (NM) NPs could improve the PEC properties; this is because NM NPs can introduce a surface plasmon resonance (SPR) effect to increase the concentration and accelerate the separation of carriers. The mechanism of the SPR effect can be explained as NM NPs are excited by light generating “hot electrons”, and the hot electrons can directly enter the conduction band (CB) of BiVO4 through an electron transfer mechanism. The potential energy of the Schottky barrier generated by the contact of NM NPs with BiVO4 is smaller than that generated by the SPR effect, which enables the “hot electrons” to be smoothly transferred from the NM NPs to the conduction band of BiVO4 without returning to the NM NPs. Ag/BiVO4 showed higher PEC activity than Au/BiVO4 because of its higher light absorption, photocurrent, and oxygen evolution capacity. It can be seen that loading NM NPs increases the concentration of the carriers while the separation and transfer rates of the carriers are improved. In conclusion, it was concluded from this study that the loading of NM NPs is an effective method to improve the water oxidation kinetics of BiVO4 photoanodes.