Explore the vast range of titles available.

Label-free biosensors are devices that use biological or chemical receptors to detect analytes (molecules) in a sample. They give detailed information on the selectivity, affinity, and, in many cases, also the binding kinetics and thermodynamics of an interaction. Although they can be powerful tools in the hands of a skilled user, there is often a lack of knowledge of the best methods for using label-free assays to screen for biologically active molecules and accurately and precisely characterize molecular recognition events. This book reviews both established and newer label-free techniques giving both the expert user and the general reader interested in the technologies and applications behind label-free an insight into the field from expert opinion leaders and practitioners of the technologies. Most importantly, chapters contain worked examples from leaders in the field that take the reader through the basics of experimental design, setup, assay development, and data analysis.

We report a combinatorial approach to design peptide-based biomimetic sensors for detecting β-type coronaviruses with high sensitivity and selectivity. We selected three peptide epitopes from key regions of the ACE2 receptor that are involved in viral binding to different variants and immobilized them individually or in binary combinations on gold sensor chips. Using Surface Plasmon Resonance (SPR), we found that single-epitope sensors displayed nanomolar dissociation constants to three RBD variants (SARS-CoV-2 Delta < SARS-CoV-2 Alpha < SARS-CoV-1) and a K D = 1.2 ± 0.4 nM to the full SARS-CoV-2 Alpha spike protein, with negligible binding to the a-coronavirus hCoV-NL63 spike protein. Molecular dynamics simulations revealed that the tightest binding epitope closely mimics ACE2 interactions with β-coronaviruses, explaining its superior performance. In contrast, dual epitope systems exhibited a reversed variant preference, with a pronounced affinity enhancement for SARS-CoV-1 (K D = 6 ± 2 nM). This was attributed to cooperative epitope interactions that could restrict the conformational flexibility of the longer epitope, favoring the effective intermolecular contacts that strengthen the interaction with the RBD. These findings suggest a time-saving approach for developing sensitive and selective sensors for rapidly mutating viruses.

The goal of this study was to determine whether MUC1 antibody conjugated with a fluorophore could be used to visualize pancreatic cancer. Anti-MUC1 (CT2) antibody was conjugated with 550 nm or 650 nm fluorophores. Nude mouse were used to make subcutaneous and orthotopic models of pancreatic cancer. Western blot and flow cytometric analysis confirmed the expression of MUC1 in human pancreatic cancer cell lines including BxPC-3 and Panc-1. Immunocytochemistry with fluorophore conjugated anti-MUC1 antibody demonstrated fluorescent areas on the membrane of Panc-1 cancer cells. After injecting the conjugated anti-MUC1 antibodies via the tail vein, subcutaneously transplanted Panc-1 and BxPC-3 tumors emitted strong fluorescent signals. In the subcutaneous tumor models, the fluorescent signal from the conjugated anti-MUC1 antibody was noted around the margin of the tumor and space between the cells. The conjugated anti-MUC1 antibody bound the tumor in orthotopically-transplanted Panc-1 and BxPC-3 models enabling the tumors to be imaged. This study showed that fluorophore conjugated anti-MUC1 antibodies could visualize pancreatic tumors in vitro and in vivo and may help to improve the diagnosis and treatment of pancreatic cancer.

Electrochemical impedance spectroscopy is finding increasing use in electrochemical sensors and biosensors, both in their characterisation, including during successive phases of sensor construction, and in application as a quantitative determination technique. Much of the published work continues to make little use of all the information that can be furnished by full physical modelling and analysis of the impedance spectra, and thus does not throw more than a superficial light on the processes occurring. Analysis is often restricted to estimating values of charge transfer resistances without interpretation and ignoring other electrical equivalent circuit components. In this article, the important basics of electrochemical impedance for electrochemical sensors and biosensors are presented, focussing on the necessary electrical circuit elements. This is followed by examples of its use in characterisation and in electroanalytical applications, at the same time demonstrating how fuller use can be made of the information obtained from complete modelling and analysis of the data in the spectra, the values of the circuit components and their physical meaning. The future outlook for electrochemical impedance in the sensing field is discussed.

Molecular imprinting is the process of template-induced formation of specific recognition sites in a polymer. Synthetic receptors prepared using molecular imprinting possess a unique combination of properties such as robustness, high affinity, specificity, and low-cost production, which makes them attractive alternatives to natural receptors. Improvements in polymer science and nanotechnology have contributed to enhanced performance of molecularly imprinted polymer (MIP) sensors. Encouragingly, recent years have seen an increase in high-quality publications describing MIP sensors for the determination of biomolecules, drugs of abuse, and explosives, driving toward applications of this technology in medical and forensic diagnostics. This review aims to provide a focused overview of the latest achievements made in MIP-based sensor technology, with emphasis on research toward real-life applications. Electrochemical and optical sensing based on molecularly imprinted polymers (MIPs) has particular relevance in real-life applications and point-of-care testing in real human samples. MIPs are a leading technology for sensing molecules where there is no available bioreceptor. MIP nanoparticles can be used for direct and indirect detection (labeled or label free). The sensitivity of MIP-based sensors can be enhanced by coupling with nanomaterials such as graphene oxide, carbon nanotubes, or nanoparticles. The present challenges and perspectives of MIP-based electrochemical and optical sensors include exploring the market niches for MIP sensors and identifying the necessary steps toward commercialization.

Organ-on-a-chip systems are miniaturized microfluidic 3D human tissue and organ models designed to recapitulate the important biological and physiological parameters of their in vivo counterparts. They have recently emerged as a viable platform for personalized medicine and drug screening. These in vitro models, featuring biomimetic compositions, architectures, and functions, are expected to replace the conventional planar, static cell cultures and bridge the gap between the currently used preclinical animal models and the human body. Multiple organoid models may be further connected together through the microfluidics in a similar manner in which they are arranged in vivo, providing the capability to analyze multiorgan interactions. Although a wide variety of human organ-on-a-chip models have been created, there are limited efforts on the integration of multisensor systems. However, in situ continual measuring is critical in precise assessment of the microenvironment parameters and the dynamic responses of the organs to pharmaceutical compounds over extended periods of time. In addition, automated and noninvasive capability is strongly desired for long-term monitoring. Here, we report a fully integrated modular physical, biochemical, and optical sensing platform through a fluidics-routing breadboard, which operates organ-on-a-chip units in a continual, dynamic, and automated manner. We believe that this platform technology has paved a potential avenue to promote the performance of current organ-on-a-chip models in drug screening by integrating a multitude of real-time sensors to achieve automated in situ monitoring of biophysical and biochemical parameters.

Automated emotion recognition (AEE) is an important issue in various fields of activities which use human emotional reactions as a signal for marketing, technical equipment, or human–robot interaction. This paper analyzes scientific research and technical papers for sensor use analysis, among various methods implemented or researched. This paper covers a few classes of sensors, using contactless methods as well as contact and skin-penetrating electrodes for human emotion detection and the measurement of their intensity. The results of the analysis performed in this paper present applicable methods for each type of emotion and their intensity and propose their classification. The classification of emotion sensors is presented to reveal area of application and expected outcomes from each method, as well as their limitations. This paper should be relevant for researchers using human emotion evaluation and analysis, when there is a need to choose a proper method for their purposes or to find alternative decisions. Based on the analyzed human emotion recognition sensors and methods, we developed some practical applications for humanizing the Internet of Things (IoT) and affective computing systems.

G-protein-coupled receptors (GPCRs) remain major drug targets, despite our incomplete understanding of how they signal through 16 non-visual G-protein signal transducers (collectively named the transducerome) to exert their actions. To address this gap, we have developed an open-source suite of 14 optimized bioluminescence resonance energy transfer (BRET) Gαβγ biosensors (named TRUPATH) to interrogate the transducerome with single pathway resolution in cells. Generated through exhaustive protein engineering and empirical testing, the TRUPATH suite of Gαβγ biosensors includes the first Gα15 and GαGustducin probes. In head-to-head studies, TRUPATH biosensors outperformed first-generation sensors at multiple GPCRs and in different cell lines. Benchmarking studies with TRUPATH biosensors recapitulated previously documented signaling bias and revealed new coupling preferences for prototypic and understudied GPCRs with potential in vivo relevance. To enable a greater understanding of GPCR molecular pharmacology by the scientific community, we have made TRUPATH biosensors easily accessible as a kit through Addgene. Development of BRET sensors for nearly all major G proteins show that GPCR–G-protein coupling ranges from promiscuous to extremely specific, Switch III is a novel site for G-protein engineering, and optimal donor–acceptor positioning is non-obvious.

Electrochemiluminescence (ECL) is a powerful transduction technique with a leading role in the biosensing field due to its high sensitivity and low background signal. Although the intrinsic analytical strength of ECL depends critically on the overall efficiency of the mechanisms of its generation, studies aimed at enhancing the ECL signal have mostly focused on the investigation of materials, either luminophores or coreactants, while fundamental mechanistic studies are relatively scarce. Here, we discover an unexpected but highly efficient mechanistic path for ECL generation close to the electrode surface (signal enhancement, 128%) using an innovative combination of ECL imaging techniques and electrochemical mapping of radical generation. Our findings, which are also supported by quantum chemical calculations and spin trapping methods, led to the identification of a family of alternative branched amine coreactants, which raises the analytical strength of ECL well beyond that of present state-of-the-art immunoassays, thus creating potential ECL applications in ultrasensitive bioanalysis. Electrochemiluminescence (ECL) is a leading technique in biosensing. Here the authors identify an ECL generation mechanism near the electrode surface, which they exploit in combination with the use of branched amine coreactants to improve the ECL signal beyond the state-of-the-art immunoassays.

Peripheral biochemical monitoring involves the use of wearable devices for minimally invasive or noninvasive measurement of analytes in biofluids such as interstitial fluid, saliva, tears and sweat. The goal in most cases is to obtain measurements that serve as surrogates for circulating analyte concentrations in blood. Key technological developments to date include continuous glucose monitors, which use an indwelling sensor needle to measure glucose in interstitial fluid, and device-integrated sweat stimulation for continuous access to analytes in sweat. Further development of continuous sensing technologies through new electrochemical sensing modalities will be a major focus of future research. While there has been much investment in wearable technologies to sense analytes, less effort has been directed to understanding the physiology of biofluid secretion. Elucidating the underlying biology is crucial for accelerating technological progress, as the biofluid itself often presents the greatest challenge in terms of sample volumes, secretion rates, filtration, active analyte channels, variable pH and salinity, analyte breakdown and other confounding factors.Heikenfeld et al. survey the range of biochemical analytes that can be sensed in dermal interstitial fluid, saliva and sweat, and outline criteria for tailoring sensor design to address the right analyte in the right body site for the right disease or wellness application.