Nanotubes in biosensing

Progress in Nanomaterials-Based Enzyme and Aptamer Biosensor for the Detection of Organophosphorus Pesticides

With the improvement of people's safety awareness, the requirement of pesticide detection is gradually increasing, and many new detection methods toward Organophosphorus pesticide (OPs) has been further developed and applied. Nanomaterials-based biosensors have played an important role in the trace detection of OPs. This article mainly introduces the detection principle of enzymes and aptamers as the identification element of biosensors. Various nanomaterials (i.e., metals and metal oxides, carbon nanotubes, graphene and graphene oxide, quantum dots, metal organic frameworks, molecular imprinted polymers, etc.) possess their unique properties and play different roles in the enzyme and aptamer-based biosensors toward OPs: (a) to produce the optical or electrochemical signal; (b) as a carrier to load the enzyme or aptamer; (c) to enhance the signal response. Besides, the intelligent portable devices provide the possibility to realize the onsite and real-time detection. The limitations of some nanomaterials and the future development are discussed. Finally, the future of enzyme and aptamer-based biosensors has prospected.

Carbon Nanotube (CNT)-Based Biosensors

This review focuses on recent advances in the application of carbon nanotubes (CNTs) for the development of sensors and biosensors. The paper discusses various configurations of these devices, including their integration in analytical devices. Carbon nanotube-based sensors have been developed for a broad range of applications including electrochemical sensors for food safety, optical sensors for heavy metal detection, and field-effect devices for virus detection. However, as yet there are only a few examples of carbon nanotube-based sensors that have reached the marketplace. Challenges still hamper the real-world application of carbon nanotube-based sensors, primarily, the integration of carbon nanotube sensing elements into analytical devices and fabrication on an industrial scale.

Recent progress on the sensitive detection of cardiovascular disease markers by electrochemical-based biosensors

Cardiovascular disease is the most reason for deaths in all over the world. Hence, biomarkers of cardiovascular diseases are very crucial for diagnosis and management process. Biomarker detection demand is opened the important way in biosensor development field. Rapid, cheap, portable, precise, selective and sensitive biomarker sensing devices are needed at this point to detect and predict disease. A cardiac biomarker can be orderable as C-reactive protein, troponin I or T, myoglobin, tumor necrosis factor alpha, interleukin-6, interleukin-1, lipoprotein-associated phospholipase, low-density lipoprotein and myeloperoxidase. They are used for prediction of cardiovascular diseases. There are many methods for early diagnosis of cardiovascular diseases, but these have long time process and expensive devices. In recent studies, different biosensors have been developed to remove the problems in this field. Electrochemical devices and developed biosensors have many superiorities than others such as low cost, mobile, reliable, repeatable, need a little amount of solution. In this review, recent studies were presented as details for cardiovascular disease biomarkers detection using electrochemical methods.

Scanning Techniques for Nanobioconjugates of Carbon Nanotubes

Nanobioconjugates using carbon nanotubes (CNTs) are attractive and promising hybrid materials. Various biological applications using the CNT nanobioconjugates, for example, drug delivery systems and nanobiosensors, have been proposed by many authors. Scanning techniques such as scanning electron microscopy (SEM) and scanning probe microscopy (SPM) have advantages to characterize the CNT nanobioconjugates under various conditions, for example, isolated conjugates, conjugates in thin films, and conjugates in living cells. In this review article, almost 300 papers are categorized based on types of CNT applications, and various scanning data are introduced to illuminate merits of scanning techniques.

Electrochemical Enzyme Biosensors Revisited: Old Solutions for New Problems

Worldwide legislation is driving the development of novel and highly efficient analytical tools for assessing the composition of every material that interacts with Consumers or Nature. The biosensor technology is one of the most active R&D domains of Analytical Sciences focused on the challenge of taking analytical chemistry to the field. Electrochemical biosensors based on redox enzymes, in particular, are highly appealing due to their usual quick response, high selectivity and sensitivity, low cost and portable dimensions. This review paper aims to provide an overview of the most important advances made in the field since the proposal of the first biosensor, the well-known hand-held glucose meter. The first section addresses the current needs and challenges for novel analytical tools, followed by a brief description of the different components and configurations of biosensing devices, and the fundamentals of enzyme kinetics and amperometry. The following sections emphasize on enzyme-based amperometric biosensors and the different stages of their development.

Nanostructured Electrochemical Biosensors for Label-Free Detection of Water- and Food-Borne Pathogens

The emergence of nanostructured materials has opened new horizons in the development of next generation biosensors. Being able to control the design of the electrode interface at the nanoscale combined with the intrinsic characteristics of the nanomaterials engenders novel biosensing platforms with improved capabilities. The purpose of this review is to provide a comprehensive and critical overview of the latest trends in emerging nanostructured electrochemical biosensors. A detailed description and discussion of recent approaches to construct label-free electrochemical nanostructured electrodes is given with special focus on pathogen detection for environmental monitoring and food safety. This includes the use of nanoscale materials such as nanotubes, nanowires, nanoparticles, and nanosheets as well as porous nanostructured materials including nanoporous anodic alumina, mesoporous silica, porous silicon, and polystyrene nanochannels. These platforms may pave the way toward the development of point-of-care portable electronic devices for applications ranging from environmental analysis to biomedical diagnostics.

Monitoring the antioxidant effects of catechin using single-walled carbon nanotubes: Comparative analysis by near-infrared absorption and near-infrared photoluminescence

We measured the optical responses of single-walled carbon nanotubes (SWNTs) after adding Japanese green tea or catechin. SWNTs were covered with DNA in aqueous solution, and tea or catechin solution was added to the DNA-SWNT suspension. The antioxidant effects of tea and catechin were detected as changes in the near-infrared (NIR) absorption (ABS) and NIR-photoluminescence (PL) spectra of the SWNTs. Commercial Japanese tea, diluted 100 times and containing 15μg/mL catechin, was sufficient for recovering NIR-ABS and NIR-PL spectra when the DNA-SWNT suspension was pre-treated with 0.03% hydrogen peroxide(H₂O₂). Similar results were obtained with 15μg/mL of pure catechin solution. SWNTs with specific chirality were sensitive to the NIR-ABS and NIR-PL changes. The (10, 5)/(8, 7) and (9, 4) SWNTs showed the highest recovery in NIR-ABS and NIR-PL, respectively. NIR-PL recovery was higher than that of NIR-ABS for (10, 5)/(8, 7) and (9, 4). Spectral changes could be monitored thoroughly at pH 8.0, contrary to pH 6.0 and 7.3. However, the most dynamic recovery of NIR-ABS and NIR-PL was observed at pH 6.0. Furthermore, time-lapse measurements revealed that recovery was faster with tea or catechin addition than H₂O₂-induced oxidation.

Escherichia coli bacteria detection by using graphene-based biosensor

Graphene is an allotrope of carbon with two-dimensional (2D) monolayer honeycombs. A larger detection area and higher sensitivity can be provided by graphene-based nanosenor because of its 2D structure. In addition, owing to its special characteristics, including electrical, optical and physical properties, graphene is known as a more suitable candidate compared to other materials used in the sensor application. A novel model employing a field-effect transistor structure using graphene is proposed and the current-voltage (I-V) characteristics of graphene are employed to model the sensing mechanism. This biosensor can detect Escherichia coli (E. coli) bacteria, providing high levels of sensitivity. It is observed that the graphene device experiences a drastic increase in conductance when exposed to E. coli bacteria at 0-10(5) cfu/ml concentration. The simple, fast response and high sensitivity of this nanoelectronic biosensor make it a suitable device in screening and functional studies of antibacterial drugs and an ideal high-throughput platform which can detect any pathogenic bacteria. Artificial neural network and support vector regression algorithms have also been used to provide other models for the I-V characteristic. A satisfactory agreement has been presented by comparison between the proposed models with the experimental data.

Hybrids of Nucleic Acids and Carbon Nanotubes for Nanobiotechnology

Recent progress in the combination of nucleic acids and carbon nanotubes (CNTs) has been briefly reviewed here. Since discovering the hybridization phenomenon of DNA molecules and CNTs in 2003, a large amount of fundamental and applied research has been carried out. Among thousands of papers published since 2003, approximately 240 papers focused on biological applications were selected and categorized based on the types of nucleic acids used, but not the types of CNTs. This survey revealed that the hybridization phenomenon is strongly affected by various factors, such as DNA sequences, and for this reason, fundamental studies on the hybridization phenomenon are important. Additionally, many research groups have proposed numerous practical applications, such as nanobiosensors. The goal of this review is to provide perspective on biological applications using hybrids of nucleic acids and CNTs.

Nanomaterials based electrochemical sensors for biomedical applications

A growing variety of sensors have increasingly significant impacts on everyday life. Key issues to take into consideration toward the integration of biosensing platforms include the demand for minimal costs and the potential for real time monitoring, particularly for point-of-care applications where simplicity must also be considered. In light of these developmental factors, electrochemical approaches are the most promising candidate technologies due to their simplicity, high sensitivity and specificity. The primary focus of this review is to highlight the utility of nanomaterials, which are currently being studied for in vivo and in vitro medical applications as robust and tunable diagnostic and therapeutic platforms. Highly sensitive and precise nanomaterials based biosensors have opened up the possibility of creating novel technologies for the early-stage detection and diagnosis of disease related biomarkers. The attractive properties of nanomaterials have paved the way for the fabrication of a wide range of electrochemical sensors that exhibit improved analytical capacities. This review aims to provide insights into nanomaterials based electrochemical sensors and to illustrate their benefits in various key biomedical applications. This emerging discipline, at the interface of chemistry and the life sciences, offers a broad palette of opportunities for researchers with interests that encompass nanomaterials synthesis, supramolecular chemistry, controllable drug delivery and targeted theranostics in biology and medicine.

Exposure of single-walled carbon nanotubes impairs the functions of primarily cultured murine peritoneal macrophages

It is increasingly important to understand the single-walled carbon nanotubes' (SWCNTs) immune response as their increasingly biomedical researches and applications. Macrophages and T cells play important roles in scavenging foreign materials and pathogens and regulating immune response. In this work, primarily cultured murine peritoneal macrophages and purified splenic T cells were utilised to determine the toxic effects of SWCNTs and acid-functionalised SWCNTs (AF-SWCNTs) on the immune system, especially on macrophage functions. Macrophages were exposed to 0-50 μg/ml of CNTs for 24 h and no significant cytotoxicity was found by live/dead and annexin-V-FITC/PI analyses. The TEM images revealed that AF-SWCNTs were engulfed mostly through phagocytosis and located in lysosomes of macrophages. Measurement of mitochondrial membrane potential and proteasome subunit gene expression demonstrated that 10 and 50 μg/ml AF-SWCNTs could damage mitochondrial function and proteasome formation in a concentration-dependent manner. Functional analyses revealed that the percentage of phagocytic cells were affected significantly by 20 μg/ml CNTs, and 5 μg/ml AF-SWCNTs inhibited the phagocytic efficiency of latex beads in macrophages. The accessory cell function was affected by both AF-SWCNTs and SWCNTs at concentrations of 10 and 50 μg/ml, respectively. Furthermore, AF-SWCNT biased naïve T-cell differentiation to Th1 type by inducing the production of IFN-γ and TNF, implying the potential risk of Th1-associated diseases (e.g. autoimmune diseases and inflammation) on AF-SWCNT exposure.

Lipid bilayers covalently anchored to carbon nanotubes

The unique physical and electrical properties of carbon nanotubes make them an exciting material for applications in various fields such as bioelectronics and biosensing. Due to the poor water solubility of carbon nanotubes, functionalization for such applications has been a challenge. Of particular need are functionalization methods for integrating carbon nanotubes with biomolecules and constructing novel hybrid nanostructures for bionanoelectronic applications. We present a novel method for the fabrication of dispersible, biocompatible carbon nanotube-based materials. Multiwalled carbon nanotubes (MWCNTs) are covalently modified with primary amine-bearing phospholipids in a carbodiimide-activated reaction. These modified carbon nanotubes have good dispersibility in nonpolar solvents. Fourier transform infrared (FTIR) spectroscopy shows peaks attributable to the formation of amide bonds between lipids and the nanotube surface. Simple sonication of lipid-modified nanotubes with other lipid molecules leads to the formation of a uniform lipid bilayer coating the nanotubes. These bilayer-coated nanotubes are highly dispersible and stable in aqueous solution. Confocal fluorescence microscopy shows labeled lipids on the surface of bilayer-modified nanotubes. Transmission electron microscopy (TEM) shows the morphology of dispersed bilayer-coated MWCNTs. Fluorescence quenching of lipid-coated MWCNTs confirms the bilayer configuration of the lipids on the nanotube surface, and fluorescence anisotropy measurements show that the bilayer is fluid above the gel-to-liquid transition temperature. The membrane protein α-hemolysin spontaneously inserts into the MWCNT-supported bilayer, confirming the biomimetic membrane structure. These biomimetic nanostructures are a promising platform for the integration of carbon nanotube-based materials with biomolecules.

Cavitand-functionalized SWCNTs for N-methylammonium detection

Single-walled carbon nanotubes (SWCNTs) have been functionalized with highly selective tetraphosphonate cavitand receptors. The binding of charged N-methylammonium species to the functionalized SWCNTs was analyzed by X-ray photoelectron spectroscopy and confirmed by (31)P MAS NMR spectroscopy. The cavitand-functionalized SWCNTs were shown to function as chemiresistive sensory materials for the detection of sarcosine and its ethyl ester hydrochloride in water with high selectivity at concentrations as low as 0.02 mM. Exposure to sarcosine and its derivative resulted in an increased conductance, in contrast to a decreased conductance response observed for potential interferents such as the structurally related glycine ethyl ester hydrochloride.

Antibody-targeted nanoparticles for cancer therapy

In recent years, nanoparticulate-mediated drug delivery research has examined a full spectrum of nanoparticles that can be used in diagnostic and therapeutic cancer applications. A key aspect of this technology is in the potential to specifically target the nanoparticles to diseased cells using a range of molecules, in particular antibodies. Antibody–nanoparticle conjugates have the potential to elicit effective targeting and release of therapeutic targets at the disease site, while minimizing off-target side effects caused by dosing of normal tissues. This article provides an overview of various antibody-conjugated nanoparticle strategies, focusing on the rationale of cell-surface receptors targeted and their potential clinical application.