Potential diagnostic applications of biosensors: current and future directions

This review describes recent advances in biosensors of potential clinical applications. Biosensors are becoming increasingly important and practical tools in pathogen detection, molecular diagnostics, environmental monitoring, food safety control as well as in homeland defense. Electrochemical biosensors are particularly promising toward these goals arising due to several combined advantages including low-cost, operation convenience, and miniaturized devices. We review the clinical applications of electrochemical biosensors based on a few selected examples, including enzyme-based biosensors, immunological biosensors and DNA biosensors.     

Development of biosensors for cancer clinical testing

Biosensors are devices that combine a biochemical recognition/binding element (ligand) with a signal conversion unit (transducer). Biosensors are already used for several clinical applications, for example for electrochemical measurement of blood glucose concentrations. Application of biosensors in cancer clinical testing has several potential advantages over other clinical analysis methods including increased assay speed and flexibility, capability for multi-target analyses, automation, reduced costs of diagnostic testing and a potential to bring molecular diagnostic assays to community health care systems and to underserved populations. They have the potential for facilitating Point of Care Testing (POCT), where state-of-the-art molecular analysis is carried out without requiring a state-of-the-art laboratory. However, not many biosensors have been developed for cancer-related testing. One major challenge in harnessing the potential of biosensors is that cancer is a very complex set of diseases. Tumors vary widely in etiology and pathogenesis. Oncologists rely heavily on histological characterization of tumors and a few biomarkers that have demonstrated clinical utility to aid in patient management decisions. New genomic and proteomic molecular tools are being used to profile tumors and produce "molecular signatures." These signatures include genetic and epigenetic signatures, changes in gene expression, protein profiles and post-translational modifications of proteins. These molecular signatures provide new opportunities for utilizing biosensors. Biosensors have enormous potential to deliver the promise of new molecular diagnostic strategies to patients. This article describes some of the basic elements of cancer biology and cancer biomarkers relevant for the development of biosensors for cancer clinical testing, along with the challenges in using this approach.     

Aptamers for pharmaceuticals and their application in environmental analytics

Aptamers are single-stranded DNA or RNA oligonucleotides, which are able to bind with high affinity and specificity to their target. This property is used for a multitude of applications, for instance as molecular recognition elements in biosensors and other assays. Biosensor application of aptamers offers the possibility for fast and easy detection of environmental relevant substances. Pharmaceutical residues, deriving from human or animal medical treatment, are found in surface, ground, and drinking water. At least the whole range of frequently administered drugs can be detected in noticeable concentrations. Biosensors and assays based on aptamers as specific recognition elements are very convenient for this application because aptamer development is possible for toxic targets. Commonly used biological receptors for biosensors like enzymes or antibodies are mostly unavailable for the detection of pharmaceuticals. This review describes the research activities of aptamer and sensor developments for pharmaceutical detection, with focus on environmental applications.     

Modularized synthetic biology enabled intelligent biosensors

Biosensors that sense the concentration of a specified target and produce a specific signal output have become important technology for biological analysis. Recently, intelligent biosensors have received great interest due to their adaptability to meet sophisticated demands. Advances in developing standard modules and carriers in synthetic biology have shed light on intelligent biosensors that can implement advanced analytical processing to better accommodate practical applications. This review focuses on intelligent synthetic biology-enabled biosensors (SBBs). First, we illustrate recent progress in intelligent SBBs with the capability of computation, memory storage, and self-calibration. Then, we discuss emerging applications of SBBs in point-of-care testing (POCT) and wearable monitoring. Finally, future perspectives on intelligent SBBs are proposed.     

Advances in Cell‐Free Biosensors: Principle,Mechanism, and Applications

Synthetic biology has promoted the development of biosensors as tools for detecting trace substances. In the past, biosensors based on synthetic biology have been designed on living cells, but the development of cell biosensors has been greatly limited by defects such as genetically modified organism problem and the obstruction of cell membrane. However, the advent of cell‐free synthetic biology addresses these limitations. Biosensors based on the cell‐free protein synthesis system have the advantages of higher safety, higher sensitivity, and faster response time over cell biosensors, which make cell‐free biosensors have a broader application prospect. This review summarizes the workflow of various cell‐free biosensors, including the identification of analytes and signal output. The detection range of cell‐free biosensors is greatly enlarged by different recognition mechanisms and output methods. In addition, the review also discusses the applications of cell‐free biosensors in environmental monitoring and health diagnosis, as well as existing deficiencies and aspects that should be improved. In the future, through continuous improvement and optimization, the potential of cell‐free biosensors will be stimulated, and their application fields will be expanded.     

Aspects Affecting Biosynthesis and Biotransformation of Secondary Metabolites in Plant Cell Cultures

Abstract

Biosensors are useful analytical devices that can be integrated with on-line process monitoring schemes. In this article, the principles and applications of these devices for bioprocess monitoring are considered. Several different types of biosensors are described, and the applications and limitations of flow injection analysis (FIA) for these applications are discussed. It is hoped that the background provided here can be useful to researchers in this area.     

Plant tissue-and photosynthesis-based biosensors

Biosensors are promising biotools, alternative or complementary to conventional analysis techniques, for fast, simple, cheap and reliable screening. This article reviews the biosensors that use plant components as biorecognition elements. In the first section, plant tissue-based biosensors are summarised and classified according to the enzyme used. Afterwards, photosynthesis-based biosensors, including the types of photosynthetic materials and immobilisation methods, are described.     

Development of an optimized backbone of FRET biosensors for kinases and GTPases

Biosensors based on the principle of Förster (or fluorescence) resonance energy transfer (FRET) have shed new light on the spatiotemporal dynamics of signaling molecules. Among them, intramolecular FRET biosensors have been increasingly used due to their high sensitivity and user-friendliness. Time-consuming optimizations by trial and error, however, obstructed the development of intramolecular FRET biosensors. Here we report an optimized backbone for rapid development of highly sensitive intramolecular FRET biosensors. The key concept is to exclude the “orientation-dependent” FRET and to render the biosensors completely “distance-dependent” with a long, flexible linker. We optimized a pair of fluorescent proteins for distance-dependent biosensors, and then developed a long, flexible linker ranging from 116 to 244 amino acids in length, which reduced the basal FRET signal and thereby increased the gain of the FRET biosensors. Computational simulations provided insight into the mechanisms by which this optimized system was the rational strategy for intramolecular FRET biosensors. With this backbone system, we improved previously reported FRET biosensors of PKA, ERK, JNK, EGFR/Abl, Ras, and Rac1. Furthermore, this backbone enabled us to develop novel FRET biosensors for several kinases of RSK, S6K, Akt, and PKC and to perform quantitative evaluation of kinase inhibitors in living cells.     

On the challenges of detecting whole Staphylococcus aureus cells with biosensors

Due to the increasing number of nosocomial infections and multidrug‐resistant bacterial strains, Staphylococcus aureus is now a major worldwide concern. Rapid detection and characterization of this bacterium has become an important issue for biomedical applications. Biosensors are increasingly appearing as low‐cost, easy‐to‐operate and fast alternatives for rapid detection. In this review, we will introduce the main characteristics of S. aureus and will focus on the interest of biosensors for a faster detection of whole S. aureus cells. In particular, we will review the most promising strategies in the choice of ligand for the design of selective and efficient biosensors. Their specific characteristics as well as their advantages and/or disadvantages will also be commented.     

生物传感器在环境分析中的研究现状与前景

论述生物传感器的发展现状与前景。在环境控制中,生物传感器作为广谱装置应用于废水或生化需氧量的检测以及特异性地对农药、重金属、硝酸盐、亚硝酸盐、除草剂和次氮基乙酸等环境污染物进行检测。讨论了各类生物传感器（如酶生物传感器、全细胞生物传感器、受体传感器和免疫传感器）在环境分析中的应用实例及其优缺点,并指出了急需解决的问题以阐明其应用趋势,以期在这一跨学科领域进行更多的研究。     

Biosensors for process control

Biosensors have been extensively studied during the last 20 years, and a myriad of laboratory biosensors have been developed. Improvements are required in biosensor design and performance before they become widely accepted in industrial process monitoring. However, as the biotechnology industry expands, biosensors may become more acceptable because, despite their limitations, they are the only devices capable of delivering the information required.     

Biosensors for the Detection of Environmental and Urban Pollutions

Release of harmful pollutants such as heavy metals, pesticides, and pharmaceuticals to the environment is a global concern. Rapid and reproducible detection of these pollutants is thus necessary. Biosensors are the sensitive and high specific tools for detection of environmental pollutants. Broad range various types of biosensors have been fabricated for this purpose. This review focuses on the feature and application of biosensors developed for environmental and urban pollutants detection. J. Cell. Biochem. 119: 207–212, 2018. © 2017 Wiley Periodicals, Inc.     

Campylobacter spp. detection in the 21st century: A review of the recent achievements in biosensor development

Campylobacter spp. are an important cause of acute bacterial diseases in humans worldwide. Many bacterial species in the Campylobacter genus are considered harmful and may cause several infectious diseases. Currently, there are no commercial biosensors available to detect Campylobacter spp. in food matrices, and little to no testing has been done in research laboratories with actual food matrices. Biosensors potentially provide a powerful means to detect Campylobacter spp. with the advantages of high sensitivity (low limits of detection with a high signal to noise ratio), high specificity (able to selectively detect the target among several similar targets), real time sensing, and in-site monitoring. This review summarizes the latest research in biosensing technologies for detection of Campylobacter spp. based on a variety of transducers and recognition elements. Finally, a comparison is made among all recently reported biosensors for the detection of Campylobacter spp.     

A computational tool for designing FRET protein biosensors by rigid-body sampling of their conformational space

Biosensors relying on the fluorescence resonance energy transfer (FRET) between fluorescent proteins have been used for live-cell imaging of cellular events including Ca(2+) signaling. The efficiency of energy transfer between the donor and acceptor fluorescent proteins depends on the relative distance and orientation between them, which become altered by conformational changes of a fused sensory protein caused by a cellular event. In this way, changes in FRET efficiency of Ca(2+) biosensors can be correlated with Ca(2+) concentrations. The design of these FRET biosensors can be improved by modeling conformational changes before and after a cellular event. Hence, a computational tool called FPMOD was developed to predict FRET efficiency changes by constructing FRET biosensors and sampling their conformational space through rigid-body rotation. We showed with FPMOD that our computational modeling approach can qualitatively predict the FRET efficiencies of a range of biosensors, which had strong agreement with experimental results.     

Biosensors for environmental monitoring

Increasing environmental legislation which controls the release and the levels of certain chemicals in the environment has created a need for reliable monitoring of these substances in air, soil and especially water. Conventional analytical techniques, although highly precise, suffer from the disadvantages of high cost, the need for trained personnel and the fact that they are mostly laboratory bound. Biosensors because of their specificity, fast response times, low cost, portability, ease of use and a continuous real time signal, can present distinct advantages in certain cases. Their biological base makes them ideal for toxicological measurements which are suited for health and safety applications. Over the last 3-4 years there has been an increase in the number of publications concerning biosensors for environmental monitoring, especially in the field of pesticide measurements.This paper reviews some of the more important developments over the past 3-4 years.     

Sensing cellular biochemistry with fluorescent chemical–genetic hybrids

Fluorescent biosensors are powerful tools for the detection of biochemical events inside cells with high spatiotemporal resolution. Biosensors based on fluorescent proteins often suffer from issues with photostability and brightness. On the other hand, hybrid, chemical–genetic systems present unique opportunities to combine the strengths of synthetic, organic chemistry with biological macromolecules to generate exquisitely tailored semisynthetic sensors.     

Applications of whole-cell bacterial sensors in biotechnology and environmental science

Biosensors have major advantages over chemical or physical analyses with regard to specificity, sensitivity, and portability. Recently, many types of whole-cell bacterial biosensors have been developed using recombinant DNA technology. The bacteria are genetically engineered to respond to the presence of chemicals or physiological stresses by synthesizing a reporter protein, such as luciferase, β-galactosidase, or green fluorescent protein. In addition to an overview of conventional biosensors, this minireview discusses a novel type of biosensor using a photosynthetic bacterium as the sensor strain and the crtA gene, which is responsible for carotenoid synthesis, as the reporter. Since bacteria possess a wide variety of stress-response mechanisms, including antioxidation, heat-shock responses, nutrient-starvation, and membrane-damage responses, DNA response elements for several stress-response proteins can be fused with various reporter genes to construct a versatile set of bacterial biosensors for a variety of analytes. Portable biosensors for on-site monitoring have been developed using a freeze-dried biosensing strain, and cell array biosensors have been designed for high-throughput analysis. Moreover, in the future, the use of single-cell biosensors will permit detailed analyses of samples. Signals from such sensors could be detected with digital imaging, epifluorescence microscopy, and/or flow cytometry.     

Biosensor Architectures for High-Fidelity Reporting of Cellular Signaling

Understanding mechanisms of information processing in cellular signaling networks requires quantitative measurements of protein activities in living cells. Biosensors are molecular probes that have been developed to directly track the activity of specific signaling proteins and their use is revolutionizing our understanding of signal transduction. The use of biosensors relies on the assumption that their activity is linearly proportional to the activity of the signaling protein they have been engineered to track. We use mechanistic mathematical models of common biosensor architectures (single-chain FRET-based biosensors), which include both intramolecular and intermolecular reactions, to study the validity of the linearity assumption. As a result of the classic mechanism of zero-order ultrasensitivity, we find that biosensor activity can be highly nonlinear so that small changes in signaling protein activity can give rise to large changes in biosensor activity and vice versa. This nonlinearity is abolished in architectures that favor the formation of biosensor oligomers, but oligomeric biosensors produce complicated FRET states. Based on this finding, we show that high-fidelity reporting is possible when a single-chain intermolecular biosensor is used that cannot undergo intramolecular reactions and is restricted to forming dimers. We provide phase diagrams that compare various trade-offs, including observer effects, which further highlight the utility of biosensor architectures that favor intermolecular over intramolecular binding. We discuss challenges in calibrating and constructing biosensors and highlight the utility of mathematical models in designing novel probes for cellular signaling.