Electrochemical Biosensors for Pathogen Detection: An Updated Review

Electrochemical biosensors are a family of biosensors that use an electrochemical transducer to perform their functions. In recent decades, many electrochemical biosensors have been created for pathogen detection. These biosensors for detecting infections have been comprehensively studied in terms of transduction elements, biorecognition components, and electrochemical methods. This review discusses the biorecognition components that may be used to identify pathogens. These include antibodies and aptamers. The integration of transducers and electrode changes in biosensor design is a major discussion topic. Pathogen detection methods can be categorized by sample preparation and secondary binding processes. Diagnostics in medicine, environmental monitoring, and biothreat detection can benefit from electrochemical biosensors to ensure food and water safety. Disposable and reusable biosensors for process monitoring, as well as multiplexed and conformal pathogen detection, are all included in this review. It is now possible to identify a wide range of diseases using biosensors that may be applied to food, bodily fluids, and even objects' surfaces. The sensitivity of optical techniques may be superior to electrochemical approaches, but optical methods are prohibitively expensive and challenging for most end users to utilize. On the other hand, electrochemical approaches are simpler to use, but their efficacy in identifying infections is still far from satisfactory.

Electrochemical biosensors for pathogen detection

Recent advances in electrochemical biosensors for pathogen detection are reviewed. Electrochemical biosensors for pathogen detection are broadly reviewed in terms of transduction elements, biorecognition elements, electrochemical techniques, and biosensor performance. Transduction elements are discussed in terms of electrode material and form factor. Biorecognition elements for pathogen detection, including antibodies, aptamers, and imprinted polymers, are discussed in terms of availability, production, and immobilization approach. Emerging areas of electrochemical biosensor design are reviewed, including electrode modification and transducer integration. Measurement formats for pathogen detection are classified in terms of sample preparation and secondary binding steps. Applications of electrochemical biosensors for the detection of pathogens in food and water safety, medical diagnostics, environmental monitoring, and bio-threat applications are highlighted. Future directions and challenges of electrochemical biosensors for pathogen detection are discussed, including wearable and conformal biosensors, detection of plant pathogens, multiplexed detection, reusable biosensors for process monitoring applications, and low-cost, disposable biosensors.

Non-Specific Adsorption Reduction Methods in Biosensing

Non-specific adsorption (NSA) is a persistent problem that negatively affects biosensors, decreasing sensitivity, specificity, and reproducibility. Passive and active removal methods exist to remedy this issue, by coating the surface or generating surface forces to shear away weakly adhered biomolecules, respectively. However, many surface coatings are not compatible or effective for sensing, and thus active removal methods have been developed to combat this phenomenon. This review aims to provide an overview of methods of NSA reduction in biosensing, focusing on the shift from passive methods to active methods in the past decade. Attention is focused on protein NSA, due to their common use in biosensing for biomarker diagnostics. To our knowledge, this is the first review to comprehensively discuss active NSA removal methods. Lastly, the challenges and future perspectives of NSA reduction in biosensing are discussed.

Functional Biointerfaces Based on Mixed Zwitterionic Self-Assembled Monolayers for Biosensing Applications

Surface modification for biosensors has focused attention for improvement of their sensitivity and specificity, particularly for the detection in complex medium. In this work, we have synthesized zwitterionic carboxybetaine-thiols (CB-thiols) and sulfobetaine-thiols (SB-thiols) for modification of gold substrates to form a functional self-assembled monolayer (SAM) for the immunoassay in a surface plasmon resonance (SPR) biosensor. X-ray photoelectron spectroscopy (XPS), contact angle goniometer, and cyclic voltammetry were applied for characterizations of elemental composition, surface wettability, and packing density, respectively. The antifouling properties of the SAMs were accessed by quantitative analysis of protein and bacterial adsorption. The results from the SAMs with a single component indicated that the SB-thiol SAM provides better surface hydrophilicity, fouling resistance, and packing density as compared to the CB-thiol SAM, likely due to the ionic association of CB moieties. However, the CB-thiol with the functional carboxylate group plays a critical role in postmodification of biomolecules via commercially available amine coupling chemistry. Thus, the mixed SAMs were prepared to integrate the unique characteristics from CB- and SB-thiols to control compositions and surface properties. The immunoassay was performed in the SPR biosensor, showing that the zwitterionic mixed SAM enables immobilization of biorecognition elements (BREs), and improved sensitivity and specificity. Consequently, the work reveals excellent and attractive versatility, antifouling, and functionalizable properties of zwitterionic mixed SAMs comprising CB- and SB-thiols for biosensing applications. This surface chemistry is expected to be applicable to monitor specific molecular recognition events.

Piezoelectric Cantilever Biosensors for Label-free, Real-time Detection of DNA and RNA

This chapter reviews the design, fabrication, characterization, and application of piezoelectric-excited millimeter-sized cantilever (PEMC) sensors. The sensor transduction mechanism, sensing principle, and mode of operation are discussed. Bio-recognition strategies and surface functionalization methods for detection of DNA and RNA are discussed with a focus on self-assembly-based approaches. Methods for the verification of biosensor response via secondary binding assays, reversible binding assays, and the integration of complementary transduction mechanisms are presented. Sensing applications for medical diagnostics, food safety, and environmental monitoring are provided. PEMC sensor technology provides a robust platform for the real-time, label-free detection of DNA and RNA in complex matrices over nanomolar (nM) to attomolar (aM) concentration ranges.

Acoustofluidic particle trapping, manipulation, and release using dynamic-mode cantilever sensors

Active and programmable mixing, trapping, separation, manipulation and release of suspended particles in liquids using dynamic-mode cantilever sensors.