Recent advances in peptide probe-based biosensors for detection of infectious agents

Label-Free Electrochemical Biosensor Platforms for Cancer Diagnosis: Recent Achievements and Challenges

With its fatal effects, cancer is still one of the most important diseases of today's world. The underlying fact behind this scenario is most probably due to its late diagnosis. That is why the necessity for the detection of different cancer types is obvious. Cancer studies including cancer diagnosis and therapy have been one of the most laborious tasks. Since its early detection significantly affects the following therapy steps, cancer diagnosis is very important. Despite researchers' best efforts, the accurate and rapid diagnosis of cancer is still challenging and difficult to investigate. It is known that electrochemical techniques have been successfully adapted into the cancer diagnosis field. Electrochemical sensor platforms that are brought together with the excellent selectivity of biosensing elements, such as nucleic acids, aptamers or antibodies, have put forth very successful outputs. One of the remarkable achievements of these biomolecule-attached sensors is their lack of need for additional labeling steps, which bring extra burdens such as interference effects or demanding modification protocols. In this review, we aim to outline label-free cancer diagnosis platforms that use electrochemical methods to acquire signals. The classification of the sensing platforms is generally presented according to their recognition element, and the most recent achievements by using these attractive sensing substrates are described in detail. In addition, the current challenges are discussed.

Phages and Nanotechnology: New Insights against Multidrug-Resistant Bacteria

Bacterial infections are a major threat to the human healthcare system worldwide, as antibiotics are becoming less effective due to the emergence of multidrug-resistant strains. Therefore, there is a need to explore nontraditional antimicrobial alternatives to support rapid interventions and combat the spread of pathogenic bacteria. New nonantibiotic approaches are being developed, many of them at the interface of physics, nanotechnology, and microbiology. While physical factors (e.g., pressure, temperature, and ultraviolet light) are typically used in the sterilization process, nanoparticles and phages (bacterial viruses) are also applied to combat pathogenic bacteria. Particularly, phage-based therapies are rising due to the unparalleled specificity and high bactericidal activity of phages. Despite the success of phages mostly as compassionate use in clinical cases, some drawbacks need to be addressed, mainly related to their stability, bioavailability, and systemic administration. Combining phages with nanoparticles can improve their performance in vivo. Thus, the combination of nanotechnology and phages might provide tools for the rapid and accurate detection of bacteria in biological samples (diagnosis and typing), and the development of antimicrobials that combine the selectivity of phages with the efficacy of targeted therapy, such as photothermal ablation or photodynamic therapies. In this review, we aim to provide an overview of how phage-based nanotechnology represents a step forward in the fight against multidrug-resistant bacteria.

Advanced nano biosensors for rapid detection of zoonotic bacteria

An infectious disease that is transmitted from animals to humans and vice-versa is called zoonosis. Bacterial zoonotic diseases can re-emerge after they have been eradicated or controlled and are among the world's major health problems which inflict tremendous burden on healthcare systems. The first step to encounter such illnesses can be early and precise detection of bacterial pathogens to further prevent the following losses due to their infections. Although conventional methods for diagnosing pathogens, including culture-based, polymerase chain reaction-based, and immunological-based techniques, benefit from their advantages, they also have their own drawbacks, for example, taking long time to provide results, and requiring laborious work, expensive materials, and special equipment in certain conditions. Consequently, there is a greater tendency to introduce simple, innovative, quicker, accurate, and low-cost detection methods to effectively characterize the causative agents of infectious diseases. Biosensors, therefore, seem to practically be one of those novel promising diagnostic tools on this aim. These are effective and reliable elements with high sensitivity and specificity, that their usability can even be improved in medical diagnostic systems when empowered by nanoparticles. In the present review, recent advances in the development of several bio and nano biosensors, for rapid detection of zoonotic bacteria, have been discussed in details.

New analytical methods using carbon-based nanomaterials for detection of Salmonella species as a major food poisoning organism in water and soil resources

Salmonella is one of the most prevalent causing agents of food- and water-borne illnesses, posing an ongoing public health threat. These food-poisoning bacteria contaminate the resources at different stages such as production, aggregation, processing, distribution, as well as marketing. According to the high incidence of salmonellosis, effective strategies for early-stage detection are required at the highest priority. Since traditional culture-dependent methods and polymerase chain reaction are labor-intensive and time-taking, identification of early and accurate detection of Salmonella in food and water samples can prevent significant health economic burden and lessen the costs. The immense potentiality of biosensors in diagnosis, such as simplicity in operation, the ability of multiplex analysis, high sensitivity, and specificity, have driven research in the evolution of nanotechnology, innovating newer biosensors. Carbon nanomaterials enhance the detection sensitivity of biosensors while obtaining low levels of detection limits due to their possibility to immobilize huge amounts of bioreceptor units at insignificant volume. Moreover, conjugation and functionalization of carbon nanomaterials with metallic nanoparticles or organic molecules enables surface functional groups. According to these remarkable properties, carbon nanomaterials are widely exploited in the development of novel biosensors. To be specific, carbon nanomaterials such as carbon nanotubes, graphene and fullerenes function as transducers in the analyte recognition process or surface immobilizers for biomolecules. Herein the potential application of carbon nanomaterials in the development of novel Salmonella biosensors platforms is reviewed comprehensively. In addition, the current problems and critical analyses of the future perspectives of Salmonella biosensors are discussed.

Peptide-Chitosan Engineered Scaffolds for Biomedical Applications

Peptides are signaling epitopes that control many vital biological events. Increased specificity, synthetic feasibility with concomitant lack of toxicity, and immunogenicity make this emerging class of biomolecules suitable for different applications including therapeutics, diagnostics, and biomedical engineering. Further, chitosan, a naturally occurring linear polymer composed of d-glucosamine and N-acetyl-d-glucosamine units, possesses anti-microbial, muco-adhesive, and hemostatic properties along with excellent biocompatibility. As a result, chitosan finds application in drug/gene delivery, tissue engineering, and bioimaging. Despite these applications, chitosan demonstrates limited cell adhesion and lacks biosignaling. Therefore, peptide-chitosan hybrids have emerged as a new class of biomaterial with improved biosignaling properties and cell adhesion properties. As a result, recent studies encompass increased application of peptide-chitosan hybrids as composites or conjugates in drug delivery, cell therapy, and tissue engineering and as anti-microbial material. This review discusses the recent investigations involving chitosan-peptide materials and uncovers various aspects of these interesting hybrid materials for biomedical applications.

Clinical Application for Screening Down's Syndrome by Using Carboxylated Graphene Oxide-Based Surface Plasmon Resonance Aptasensors

BACKGROUND

Advanced medical detection technology requires high sensitivity and accuracy to increase the disease detection rate. We showed that carboxyl-functionalized graphene oxide (carboxyl-GO) biosensing materials are capable of accurate detection.

METHODS

We developed a carboxylated GO-based surface plasmon resonance (SPR) aptasensor suitable for screening Down's syndrome in clinical serum. This biosensing material could rapidly and accurately detect hCG protein with a low concentration to identify fetal Down's syndrome. The developed carboxyl-GO-based SPR aptasensor showed excellent sensitivity and limit of detection without the use of antibodies and without any specific preference.

RESULTS

hCG protein detection limits of 1 pM in buffer samples and 1.9 pM in clinical serum samples were achieved. The results showed that the carboxyl-GO-based chip could detect hCG well below the normal physiological level of serum protein (5.0 mIU/mL). High affinity, sensitivity, and better detection limit were obtained in the range of 1.9 pM to 135 pM. The results showed a 5k-fold dilution factor, and that an SPR angle shift of more than 20 millidegrees (mo) was associated with a significant risk of fetal Down's syndrome compared to normal pregnant women. The results clearly showed that the detection of hCG protein in serum samples from pregnant women at 12-19 weeks could be used to screen Down's syndrome with high selectivity and sensitivity.

CONCLUSION

Our findings suggest the potential application of carboxyl-GO film in proof-of-concept studies for serum assays as a new type of SPR material. In addition, peptide and carboxyl-GO films may be conducive to the development of future point of care testing and rapid diagnostic devices for other diseases such as cancer.

Rational Design of Functional Peptide-Gold Hybrid Nanomaterials for Molecular Interactions

Gold nanoparticles (AuNPs) have been extensively used for decades in biosensing-related development due to outstanding optical properties. Peptides, as newly realized functional biomolecules, are promising candidates of replacing antibodies, receptors, and substrates for specific molecular interactions. Both peptides and AuNPs are robust and easily synthesized at relatively low cost. Hence, peptide-AuNP-based bio-nano-technological approaches have drawn increasing interest, especially in the field of molecular targeting, cell imaging, drug delivery, and therapy. Many excellent works in these areas have been reported: demonstrating novel ideas, exploring new targets, and facilitating advanced diagnostic and therapeutic technologies. Importantly, some of them also have been employed to address real practical problems, especially in remote and less privileged areas. This contribution focuses on the application of peptide-gold hybrid nanomaterials for various molecular interactions, especially in biosensing/diagnostics and cell targeting/imaging, as well as for the development of highly active antimicrobial/antifouling coating strategies. Rationally designed peptide-gold nanomaterials with functional properties are discussed along with future challenges and opportunities.

Novel surface plasmon resonance biosensor that uses full-length Det7 phage tail protein for rapid and selective detection of Salmonella enterica serovar Typhimurium

We report a novel surface plasmon resonance (SPR) biosensor that uses the full-length Det7 phage tail protein (Det7T) to rapidly and selectively detect Salmonella enterica serovar Typhimurium (S. Typhimurium). Det7T, which was obtained using recombinant protein expression and purification in Escherichia coli, demonstrated a size of ∼75 kDa upon SDS-PAGE and was homotrimeric in its native structure. Microagglutination and transmission electron microscopy (TEM) data revealed that the protein specifically bound to the host, S. Typhimurium, but not to nonhost E. coli K-12 cells. The observed protein agglutination occurred over a concentration range of 0.8-24.6 µg/mL. The Det7T proteins were immobilized on gold-coated surfaces using amine-coupling to generate a novel Det7T-functionalized SPR biosensor, wherein the specific binding of these proteins with bacteria was detected by SPR. We observed rapid detection of (∼20 Min) and typical binding kinetics with S. Typhimurium in the range of 5 × 10⁴ -5 × 10⁷  CFU/mL, but not with E. coli at any tested concentration, indicating that the sensor exhibited recognition specificity. Similar binding was observed with 10% apple juice spiked with S. Typhimurium, suggesting that this strategy provides promise for the rapid, real-time, and selective monitoring of target microorganisms in the environment, and thus has great potential for supporting health by enabling early disease prevention.

Label-free analytical performances of a peptide-based QCM biosensor for trypsin

A label-free biosensor was fabricated for the detection of trypsin by using a peptide-functionalized quartz crystal microbalance gold electrode. The synthetized peptide chains were immobilized tightly on the QCM electrode via a self-assembly method, which formed a thin and approximate rigid layer of peptides. The detection signal was achieved by calculating the mass changes on the QCM electrode because the peptide chains could be specifically cleaved in the carboxyl terminuses of arginine and lysine by trypsin. When gold nanoparticles were coupled to the peptide chains, the sensing signal would be amplified 10.9 times. Furthermore, the sensor interface shows a lower resonance resistance change when the peptide chain is immobilized horizontally. Independent detections in parallel on different electrodes have a wide linear range. Under the optimum conditions, the signal-amplified biosensor allowed the measurement of trypsin over the range of 0-750 ng mL-1 with a detection limit of 8.6 ng mL-1. Moreover, for screening the inhibitor of trypsin, the IC50 values were obtained to be 1.85 μg mL-1 for benzamidine hydrochloride and 20.5 ng mL-1 for the inhibitor from soybean.

A review on peptide functionalized graphene derivatives as nanotools for biosensing

Peptides exhibit unique binding behavior with graphene and its derivatives by forming bonds on its edges and planes. This makes them useful for sensing and imaging applications. This review with (155 refs.) summarizes the advances made in the last decade in the field of peptide-GO bioconjugation, and the use of these conjugates in analytical sciences and imaging. The introduction emphasizes the need for understanding the biotic-abiotic interactions in order to construct controllable peptide-functionalized graphitic material-based nanotools. The next section covers covalent and non-covalent interactions between peptide and oxidized graphene derivatives along with a discussion of the adsorption events during interfacing. We then describe applications of peptide-graphene conjugates in bioassays, with subsections on (a) detection of cancer cells, (b) monitoring protease activity, (c) determination of environmental pollutants and (d) determination of pathogenic microorganisms. The concluding section describes the current status of peptide functionalized graphitic bioconjugates and addresses future perspectives. Graphical abstractSchematic representation depicting biosensing applications of peptide functionalized graphene oxide.

Ultrasensitive Fluorescence Detection of Alzheimer's Disease Based on Polyvalent Directed Peptide Polymer Coupled to a Nanoporous ZnO Nanoplatform

Amyloid-beta 42 (Aβ₄₂), the key biomarker of Alzheimer's disease (AD), aggregates to form neurotoxic amyloid plaques. In this work, we modified two fluorescein isothiocyanate-labeled Aβ₄₂-targeting peptides and designed an Aβ₄₂-specific ultrasensitive polyvalent-directed peptide polymer (PDPP) to enhance AD diagnosis sensitivity. The dissociation constant of Aβ₄₂ by PDPP was 10³-fold higher than the single-site-directed peptide. The improved binding was due to the ability of PDPP to detect multiple receptors on the target. The power of the PDPP diagnostic probe was verified in its application to detect Aβ₄₂ in cerebrospinal fluid (CSF), which showed a lower limit of detection (LOD) in the fg mL^-1 range that is more sensitive than detection by antibodies or single peptides. In addition, we present a novel ultrasensitive diagnostic system using an array of nanoporous ZnO nanoparticles, which play a role in fluorescence signal amplification, to further improve AD diagnosis sensitivity. We enhanced the signal on the basis of the properties of nanoporous ZnO nanoparticles and measured and quantified an ultralow concentration (ag mL^-1 range) of Aβ₄₂. This PDPP coupled to the nanoporous ZnO-based system is a novel approach to AD diagnosis that might also be useful for the detection of other target biomarkers and clinical applications.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Localized surface plasmon resonance based biosensing

INTRODUCTION

Bioanalytical sensing based on the principle of localized surface plasmon resonance experiences is currently an extremely rapid development. Novel sensors with new kinds of plasmonic transducers and innovative concepts for the signal development as well as read-out principles were identified. This review will give an overview of the development of this field. Areas covered: The focus is primarily on types of transducers by preparation or dimension, factors for optimal sensing concepts and the critical view of the usability of these devices as innovative sensors for bioanalytical applications. Expert commentary: Plasmonic sensor devices offer a high potential for future biosensing given that limiting factors such as long-time stability of the transducers, the required high sensitivity and the cost-efficient production are addressed. For higher sensitivity, the design of the sensor in shape and material has to be combined with optimal enhancement strategies. Plasmonic nanoparticles from bottom-up synthesis with a post-synthetic processing show a high potential for cost-efficient sensor production. Regarding the measurement principle, LSPRi offers a large potential for multiplex sensors and can provide a high-throughput as well as highly paralleled sensing. The main trends are expected towards optimal LSPR concepts which represent cost-efficient and robust point-of-care solutions, and the use of multiplexed devices for clinical applications.

Pilot study on an innovative biosensor with a range of medical and surgical applications

Objectives

The objective of this article is to briefly outline the utilization of biosensors in medicine and surgery and present diagnostic efficacy of thermal product (TP) based biosensor.

Results

The working principle of biosensor is based on measuring TP of a material in contact with the sensor. When an electrical square wave pulse of certain amplitude and duration is passed through TP based biosensor, the generated heat from its higher resistance will be dissipated and recorded by the sensor. As the surrounding material composition changes, the dissipated heat split between the sensor substrate and surrounding material changes which can be correlated to the change in TP of the material. For biological tissues, it is known that the thermal properties of tissues are quite different for different layers in the body and hence the heat absorbed will be different. The experiments were conducted on biological and non-biological tissues. For data acquisition software LabView 2014 (64-bit) was used and software used for post-processing was MATLAB R2015a (64-bit). The resulting graphs of TP from various materials (oil, water, saline, acetone) and biological tissue (porcine belly, porcine thigh layers and porcine abdominal viscera) expressed prominent deflections indicating diagnostic efficacy of TP based biosensor.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3163-6) contains supplementary material, which is available to authorized users.

Peptide-based electrochemical biosensor for juvenile idiopathic arthritis detection

Juvenile idiopathic arthritis (JIA) is a wide group of diseases, characterized by synovial inflammation and joint tissue damage. Due to the delay in the implementation of biomarkers into clinical practice and the association with severe sequels, there is an imperative need for new JIA diagnosis strategies. Electrochemical biosensors based on screen-printed electrodes and peptides are promising alternatives for molecular diagnosis. In this work, a novel biosensor for detecting juvenile idiopathic arthritis (JIA) was developed based on the immobilization of the PRF+1 mimetic peptide, as recognition biological element, on the surface of screen-printed carbon electrode. This biosensor was able to discriminate the JIA positive and negative serum samples from different individuals using differential pulse voltammetry, presenting limits of detection and quantification in diluted samples of 1:784 (v/v) and 1:235 (v/v), respectively. Evaluation by electrochemical impedance spectroscopy showed R_CT 3 times higher for JIA positive sample than for a pool of human serum samples from healthy individuals. Surface analysis of the biosensor by atomic force microscopy, after contact with JIA positive serum, presented great globular clusters irregularly distributed. The long-term stability of the biosensor was evaluated, remaining functional for over 40 days of storage (after storage at 8°C). Therefore, a simple, miniaturized and selective biosensor was developed, being the first one based on mimetic peptide and screen-printed carbon electrode, aiming at the diagnosis of the juvenile idiopathic arthritis in real serum samples.

Hydrogel Based Biosensors for In Vitro Diagnostics of Biochemicals, Proteins, and Genes

Hydrogel-based biosensors have drawn considerable attention due to their various advantages over conventional detection systems. Recent studies have shown that hydrogel biosensors can be excellent alternative systems to detect a wide range of biomolecules, including small biochemicals, pathogenic proteins, and disease specific genes. Due to the excellent physical properties of hydrogels such as the high water content and stimuli-responsive behavior of cross-linked network structures, this system can offer substantial improvement for the design of novel detection systems for various diagnostic applications. The other main advantage of hydrogels is the role of biomimetic three-dimensional (3D) matrix immobilizing enzymes and aptamers within the detection systems, which enhances their stability. This provides ideal reaction conditions for enzymes and aptamers to interact with substrates within the aqueous environment of the hydrogel. In this review, we have highlighted various novel detection approaches utilizing the outstanding properties of the hydrogel. This review summarizes the recent progress of hydrogel-based biosensors and discusses their future perspectives and clinical limitations to overcome.

Peptide-based fluorescence biosensors for detection/measurement of nanoparticles

The ability to detect and quantify nanoparticles is essential but there is currently no simple, sensitive, and rapid method for the detection of nanomaterials. We have developed a novel peptide-based fluorescence-based biosensor for detection and measurement of negatively charged engineered nanoparticles (ENPs). A peptide biosensor (seven lysine residues linked to a cysteine through a three glycine residue linker) with attached fluorescent probes-fluorescein-5-maleimide (F5M) and tetramethylrhodamine-5-maleimide (TMR5M)-was constructed. The fluorescent probes allow close monitoring of the molecular interaction of the labeled peptide with ENPs. The ENP-peptide interaction induces the formation of agglomerates that can be detected and measured by changes in the fluorescence intensities of the labeled peptides or/and by differential light scattering. The relative fluorescence intensities of F5M and TMR5M decreased in a concentration-dependent manner on interaction with various types of negatively charged ENPs (ZnO, Fe₃O₄, CeO, and single-walled carbon nanotubes). Differential light scattering measurements also showed increases in the hydrodynamic size of the complex. The interactions were not affected by the pH of aqueous media, where humic acid (1 μg/mL) quenched the fluorescence intensity of F5M by approximately 25 %, whereas that of TMR5M was completely quenched. Interference by humic acid at lower concentrations was less prevalent. This novel method is a simple, rapid, and inexpensive in situ assay that shows promise as a primary-level testing technique for detection of ENPs in environmental samples. Graphical Abstract Detection of nanomaterials in aqueous solutions using fluorescently-labeled designer peptides.

Electrochemical bacterial detection using poly(3-aminophenylboronic acid)-based imprinted polymer

Biosensors can deliver the rapid bacterial detection that is needed in many fields including food safety, clinical diagnostics, biosafety and biosecurity. Whole-cell imprinted polymers have the potential to be applied as recognition elements in biosensors for selective bacterial detection. In this paper, we report on the use of 3-aminophenylboronic acid (3-APBA) for the electrochemical fabrication of a cell-imprinted polymer (CIP). The use of a monomer bearing a boronic acid group, with its ability to specifically interact with cis-diol, allowed the formation of a polymeric network presenting both morphological and chemical recognition abilities. A particularly beneficial feature of the proposed approach is the reversibility of the cis-diol-boronic group complex, which facilitates easy release of the captured bacterial cells and subsequent regeneration of the CIP. Staphylococcus epidermidis was used as the model target bacteria for the CIP and electrochemical impedance spectroscopy (EIS) was explored for the label-free detection of the target bacteria. The modified electrodes showed a linear response over the range of 10³-10⁷cfu/mL. A selectivity study also showed that the CIP could discriminate its target from non-target bacteria having similar shape. The CIPs had high affinity and specificity for bacterial detection and provided a switchable interface for easy removal of bacterial cell.

Enhanced Biosensor Platforms for Detecting the Atherosclerotic Biomarker VCAM1 Based on Bioconjugation with Uniformly Oriented VCAM1-Targeting Nanobodies

Surface bioconjugation of biomolecules has gained enormous attention for developing advanced biomaterials including biosensors. While conventional immobilization (by physisorption or covalent couplings using the functional groups of the endogenous amino acids) usually results in surfaces with low activity, reproducibility and reusability, the application of methods that allow for a covalent and uniformly oriented coupling can circumvent these limitations. In this study, the nanobody targeting Vascular Cell Adhesion Molecule-1 (NbVCAM1), an atherosclerotic biomarker, is engineered with a C-terminal alkyne function via Expressed Protein Ligation (EPL). Conjugation of this nanobody to azidified silicon wafers and Biacore™ C1 sensor chips is achieved via Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) “click” chemistry to detect VCAM1 binding via ellipsometry and surface plasmon resonance (SPR), respectively. The resulting surfaces, covered with uniformly oriented nanobodies, clearly show an increased antigen binding affinity, sensitivity, detection limit, quantitation limit and reusability as compared to surfaces prepared by random conjugation. These findings demonstrate the added value of a combined EPL and CuAAC approach as it results in strong control over the surface orientation of the nanobodies and an improved detecting power of their targets—a must for the development of advanced miniaturized, multi-biomarker biosensor platforms.

An Electrochemical Biosensor Based on a Myoglobin-specific Binding Peptide for Early Diagnosis of Acute Myocardial Infarction

In this study, a simple, highly sensitive electrochemical biosensor for myoglobin was developed using a myoglobin-specific binding peptide as a sensing probe. A peptide (Myo-3R7, CPSTLGASC, 838 Da) identified by phage display and that specifically binds to myoglobin was covalently immobilized on a gold electrode functionalized via a dithiobis(succinimidyl propionate) (DSP) self-assembled monolayer (SAM). The peptide immobilization was confirmed with fluorescence microarray scanning and cyclic voltammetry (CV). The electrochemical performance of the biosensor with respect to myoglobin was characterized by CV and differential pulse voltammetry (DPV) using Fe(CN)6(3-)/Fe(CN)6(4-) as a redox probe. We successfully detected myoglobin in a broad working range of 17.8 to 1780 ng mL(-1) with a correlation coefficient (R(2)) of 0.998. The estimated limit of detection (LOD) was fairly low, 9.8 ng mL(-1) in 30 min. The electrochemical biosensor based on a myoglobin-specific binding peptide offers sensitivity, selectivity, and rapidity, making it an attractive tool for the early detection of cardiac infarction.

Sensitive detection of Escherichia coli O157:H7 using Pt-Au bimetal nanoparticles with peroxidase-like amplification

Escherichia coli O157:H7 is one of the most notorious foodborne pathogens causing serious disease at low infectious dose. To protect consumers from deadly foodborne E. coli O157:H7 infection, it is vital to develop a simple, reliable, sensitive and rapid method which can detect low level E. coli O157:H7 in foods at real-time. We have successfully developed a novel immunochromatographic assay (ICA) with enhanced sensitivity for the visual and quantitative detection of E. coli O157:H7. Sandwich-type immunoreactions were performed on the ICA, and Pt-Au bimetal nanoparticles (NPs) were accumulated on the test zone. The signal amplification is based on Pt-Au bimetal NPs possessing high peroxidase activity toward 3,3',5,5'-tetramethylbenzidine, which can produce characteristic colored bands and thus, enable visual detection of E. coli O157:H7 without instrumentation. The innovative aspect of this approach lies in the visualization and quantification of target pathogen through the detection of color intensity. Due to the excellent peroxidase activity of Pt-Au NPs, they emit strong visible color intensity in less than 1 min for visual observation even in low concentration range of E. coli O157:H7. Quantification was performed using a commercial assay meter. The sensitivity was improved more than 1000-folds compared to the conventional test strip based on colored gold-colloids. Although the feasibility was demonstrated using E. coli O157:H7 as a model analyte, this approach could be easily developed to be a universal signal amplification technique and applied to detection of a wide variety of foodborne pathogens and protein biomarkers.

Advances in Anthrax Detection: Overview of Bioprobes and Biosensors

Anthrax is an infectious disease caused by Bacillus anthracis. Although anthrax commonly affects domestic and wild animals, it causes a rare but lethal infection in humans. A variety of techniques have been introduced and evaluated to detect anthrax using cultures, polymerase chain reaction, and immunoassays to address the potential threat of anthrax being used as a bioweapon. The high-potential harm of anthrax in bioterrorism requires sensitive and specific detection systems that are rapid, field-ready, and real-time monitoring. Here, we provide a systematic overview of anthrax detection probes with their potential applications in various ultra-sensitive diagnostic systems.

Bacteriophages: biosensing tools for multi-drug resistant pathogens

Pathogen detection is of utmost importance in many sectors, such as in the food industry, environmental quality control, clinical diagnostics, bio-defence and counter-terrorism. Failure to appropriately, and specifically, detect pathogenic bacteria can lead to serious consequences, and may ultimately be lethal. Public safety, new legislation, recent outbreaks in food contamination, and the ever-increasing prevalence of multidrug-resistant infections have fostered a worldwide research effort targeting novel biosensing strategies. This review concerns phage-based analytical and biosensing methods targeted towards theranostic applications. We discuss and review phage-based assays, notably phage amplification, reporter phage, phage lysis, and bioluminescence assays for the detection of bacterial species, as well as phage-based biosensors, including optical (comprising SPR sensors and fiber optic assays), electrochemical (comprising amperometric, potentiometric, and impedimetric sensors), acoustic wave and magnetoelastic sensors.

A novel biosensor for quantitative monitoring of on-target activity of paclitaxel

This study describes a system for quantifying paclitaxel activity using the C-terminus of α-tubulin as a biomarker. Following stabilization of microtubules with paclitaxel, a specific detyrosination reaction occurs at the C-terminus of α-tubulin which could be used to assess efficacy. A fluorescence resonance energy transfer (FRET) based biosensor was synthesized comprising a short peptide that corresponded to the C-terminus of α-tubulin, a fluorophore (Abz), and a quencher (Dnp). The fluorophore added to the end of the peptide can be released upon enzymatic detyrosination. In addition, a single fluorophore-tagged peptide was also conjugated to mesoporous silica nanoparticles to examine the feasibility of combining the drug with the peptide biomarker. As a proof of concept, we found that the degree of peptide cleavage, and therefore enzymatic activity, was directly correlated with exogenous bovine carboxypeptidase (CPA) an enzyme that mimics endogenous detyrosination. In addition, we show that cell lysates obtained from paclitaxel-treated cancer cells competed with exogenous CPA for biosensor cleavage in a paclitaxel dose-dependent manner. Our work provides strong evidence for the feasibility of combining paclitaxel with a novel biosensor in a multi-load nanoparticle.

Impacts on Human Health Caused by Zoonoses

Zoonosis is an infectious disease and a potential bioterrorism agent. Bioterrorism aimed at a society, government, and/or its citizens is meant to cause destabilization, fear, anxiety, illness, and death in people, animals, or plants using biological agents. A bioterrorism attack is the intentional release of biological agents such as viruses, bacteria, fungi, rickettsial or chlamydial organisms, toxins, or other harmful agents. This chapter focuses on the induction, monitoring, and prevention of some zoonotic diseases that have potential as bioterrorism agents. The etiology, clinical manifestations, transmission routes, and treatment of these zoonotic agents are briefly discussed.

Construction of helper plasmid-mediated dual-display phage for autoantibody screening in serum

M13 filamentous bacteriophage has been used in displaying disease-specific antibodies, biomarkers, and peptides. One of the major drawbacks of using phage in diagnostic assays is the aspecific adsorption of proteins leading to a high background signal and decreasing sensitivity. To deal with this, we developed a genetically pure, exchangeable dual-display phage system in which biomarkers and streptavidin-binding protein (SBP) are displayed at opposite ends of the phage. This approach allows for sample purification, using streptavidin-coated magnetic beads resulting in a higher sensitivity of signal detection assays. Our dual-display cassette system approach also allows for easy exchange of both the anchor protein (SBP) and the displayed biomarker. The presented principle is applied for the detection of antibody reactivity against UH-RA.21 which is a good candidate biomarker for rheumatoid arthritis (RA). The applicability of dual-display phage preparation using a helper plasmid system is demonstrated, and its increased sensitivity in phage ELISA assays using patient serum samples is shown.

A biomimetic bitter receptor-based biosensor with high efficiency immobilization and purification using self-assembled aptamers

It is of substantial interest to mimic mechanisms of biological sensing systems for the development of novel biosensors. This paper presents a novel biomimetic bitter receptor-based biosensor for the detection of specific bitter substances, in which bitter receptors were used as sensitive elements for the first time. A simple and practical self-assembled aptamer-based strategy was proposed for functional immobilization and purification of bitter receptors. A human bitter receptor, T2R4, was expressed on the plasma membrane of HEK-293 cells and fused with a His6-tag on its C-terminal. The membrane fractions containing the expressed T2R4 were extracted and immobilized on the gold surface of a quartz crystal microbalance (QCM) pretreated with a monolayer of self-assembled aptamers that can specifically recognize and capture biomolecules labeled with His6-tags. The QCM device was used to monitor the responses of T2R4 to various bitter stimuli. The results indicate that this biosensor can detect denatonium with high sensitivity and specificity, which is the specific target of T2R4. In addition, this biosensor shows dose-dependent responses to a certain concentration range of denatonium. The sensitivity of bitter receptor-based biosensors prepared by an aptamer-based method is 1.21 kHz mM(-1), which is 2 times higher than that prepared by a SAM-based method. The major advances on bitter receptor immobilization and purification presented in this work could substantially be very useful for developing other membrane receptor-based biosensors and molecular sensor arrays. This bitter receptor-based biosensor has great potential to be used as a valuable tool for bitter detection as well as for the research of taste signal transduction.

Development of an oligopeptide functionalized surface plasmon resonance biosensor for online detection of glyphosate

We report a surface plasmon resonance (SPR) biosensor for online detection of glyphosate. The surface of the sensing element is decorated with an oligopeptide, TPFDLRPSSDTR, which is identified by using phage display library. This oligopeptide shows high binding specificity for glyphosate (KD = 8.6 μM), probably because of the presence of R and D in the oligopeptide. To detect glyphosate in buffer solution, an SPR gold sensor chip is modified by using the oligopeptide with a surface density of 0.6 1/nm(2). The sensitivity of this oligopeptide-functionalized SPR biosensor is 1.02 RU/μM whereas the limit of detection (LOD) is 0.58 μM. This oligopeptide functionalized SPR biosensor also shows good specificity against other analytes such as glycine, thiacloprid, and imidacloprid.

Identification, characterization and application of a G-quadruplex structured DNA aptamer against cancer biomarker protein anterior gradient homolog 2

Background

Anterior gradient homolog 2 (AGR2) is a functional protein with critical roles in a diverse range of biological systems, including vertebrate tissue development, inflammatory tissue injury responses, and cancer progression. Clinical studies have shown that the AGR2 protein is overexpressed in a wide range of human cancers, including carcinomas of the esophagus, pancreas, breast, prostate, and lung, making the protein as a potential cancer biomarker. However, the general biochemical functions of AGR2 in human cells remain undefined, and the signaling mechanisms that drive AGR2 to inhibit p53 are still not clearly illustrated. Therefore, it is of great interest to develop molecular probes specifically recognizing AGR2 for its detection and for the elucidation of AGR2-associated molecular mechanism.

Methodology/Principal Findings

Through a bead-based and flow cytometry monitored SELEX technology, we have identified a group of DNA aptamers that can specifically bind to AGR2 with K_d values in the nanomolar range after 14 rounds of selections. Aptamer C14B was chosen to further study, due to its high binding affinity and specificity. The optimized and shortened C14B1 has special G-rich characteristics, and the G-rich region of this binding motif was further characterized to reveal an intramolecular parallel G-quadruplex by CD spectroscopy and UV spectroscopy. Our experiments confirmed that the stability of the G-quadruplex structure was strongly dependent on the nature of the monovalent ions and the formation of G-quadruplex structure was also important for the binding capacity of C14B1 to the target. Furthermore, we have designed a kind of allosteric molecule beacon (aMB) probe for selective and sensitive detection of AGR2.

Conclusion/Significance

In this work, we have developed new aptamer probes for specific recognition of the AGR2. Structural study have identified that the binding motif of aptamer is an intramolecular parallel G-quadruplex structure and its structure and binding affinity are strongly dependent on the nature of the monovalent ion. Furthermore, with our design of AGR2-aMB, AGR2 could be sensitively and selectively detected. This aptamer probe has great potential to serve as a useful tool for early diagnosis and prognosis of cancer and for fundamental research to elucidate the biochemical functions of AGR2.

Detection of Cryptosporidium in miniaturised fluidic devices

Contamination of drinking water with the protozoan pathogen, Cryptosporidium, represents a serious risk to human health due to the low infectious dose and the resistance of this parasite to chlorine disinfection. Therefore, several countries have legislated for the frequent monitoring of drinking water for Cryptosporidium presence. Existing approved monitoring protocols are however time-consuming and do not provide essential information on the species, virulence or viability of detected oocysts. Rapid, more information-rich and automatable systems for Cryptosporidium detection are highly sought-after, and numerous miniaturised devices have been developed to address this need. This review article aims to summarise the state-of-the-art and compare the performance of these systems in terms of detection limit, ability to determine species, viability and performance in the presence of interferents. Finally, conclusions are drawn with regard to the most promising methods and directions of future research.

New trends in impedimetric biosensors for the detection of foodborne pathogenic bacteria

The development of a rapid, sensitive, specific method for the foodborne pathogenic bacteria detection is of great importance to ensure food safety and security. In recent years impedimetric biosensors which integrate biological recognition technology and impedance have gained widespread application in the field of bacteria detection. This paper presents an overview on the progress and application of impedimetric biosensors for detection of foodborne pathogenic bacteria, particularly the new trends in the past few years, including the new specific bio-recognition elements such as bacteriophage and lectin, the use of nanomaterials and microfluidics techniques. The applications of these new materials or techniques have provided unprecedented opportunities for the development of high-performance impedance bacteria biosensors. The significant developments of impedimetric biosensors for bacteria detection in the last five years have been reviewed according to the classification of with or without specific bio-recognition element. In addition, some microfluidics systems, which were used in the construction of impedimetric biosensors to improve analytical performance, are introduced in this review.

Survey of the 2009 commercial optical biosensor literature

We took a different approach to reviewing the commercial biosensor literature this year by inviting 22 biosensor users to serve as a review committee. They set the criteria for what to expect in a publication and ultimately decided to use a pass/fail system for selecting which papers to include in this year's reference list. Of the 1514 publications in 2009 that reported using commercially available optical biosensor technology, only 20% passed their cutoff. The most common criticism the reviewers had with the literature was that "the biosensor experiments could have been done better." They selected 10 papers to highlight good experimental technique, data presentation, and unique applications of the technology. This communal review process was educational for everyone involved and one we will not soon forget.

Rapid development of new protein biosensors utilizing peptides obtained via phage display

There is a consistent demand for new biosensors for the detection of protein targets, and a systematic method for the rapid development of new sensors is needed. Here we present a platform where short unstructured peptides that bind to a desired target are selected using M13 phage display. The selected peptides are then chemically synthesized and immobilized on gold, allowing for detection of the target using electrochemical techniques such as electrochemical impedance spectroscopy (EIS). A quartz crystal microbalance (QCM) is also used as a diagnostic tool during biosensor development. We demonstrate the utility of this approach by creating a novel peptide-based electrochemical biosensor for the enzyme alanine aminotransferase (ALT), a well-known biomarker of hepatotoxicity. Biopanning of the M13 phage display library over immobilized ALT, led to the rapid identification of a new peptide (ALT5-8) with an amino acid sequence of WHWRNPDFWYLK. Phage particles expressing this peptide exhibited nanomolar affinity for immobilized ALT (K(d,app) = 85±20 nM). The newly identified ALT5-8 peptide was then chemically synthesized with a C-terminal cysteine for gold immobilization. The performance of the gold-immobilized peptides was studied with cyclic voltammetry (CV), QCM, and EIS. Using QCM, the sensitivity for ALT detection was 8.9±0.9 Hz/(µg/mL) and the limit of detection (LOD) was 60 ng/mL. Using EIS measurements, the sensitivity was 142±12 impedance percentage change %/(µg/mL) and the LOD was 92 ng/mL. In both cases, the LOD was below the typical concentration of ALT in human blood. Although both QCM and EIS produced similar LODs, EIS is preferable due to a larger linear dynamic range. Using QCM, the immobilized peptide exhibited a nanomolar dissociation constant for ALT (K(d) = 20.1±0.6 nM). These results demonstrate a simple and rapid platform for developing and assessing the performance of sensitive, peptide-based biosensors for new protein targets.

Computerized disease profiling using GPS-linked multi-function sensor cartridges

Disease identification in public health monitoring routinely employs analyte detection systems capable of discriminating mixtures of analytes, toxins, cells and/or bacteria in medical and/or environmental solutions. The development of smart sensors capable of discriminating such compounds has become increasingly important for clinical, environmental, and health applications. While some sensors have been fashioned for single analyte detection, methods and systems that facilitate rapid screening of multiple clinical components are needed, serving as triggers for potential epidemics or more specific confirmatory testing. In public health applications, there is like need for immediate collection of geocoded data tagged by disease identification characteristics, with corresponding alerting capabilities. In this technology review we propose one promising model for using a combination of emerging systems-based technologies in multi sensor cartridges, integrated with GPS-enabled, alert-capable mobile phone devices.

High-throughput biosensors for multiplexed food-borne pathogen detection

Incidental contamination of foods by pathogenic bacteria and/or their toxins is a serious threat to public health and the global economy. The presence of food-borne pathogens and toxins must be rapidly determined at various stages of food production, processing, and distribution. Producers, processors, regulators, retailers, and public health professionals need simple and cost-effective methods to detect different species or serotypes of bacteria and associated toxins in large numbers of food samples. This review addresses the desire to replace traditional microbiological plate culture with more timely and less cumbersome rapid, biosensor-based methods. Emphasis focuses on high-throughput, multiplexed techniques that allow for simultaneous testing of numerous samples, in rapid succession, for multiple food-borne analytes (primarily pathogenic bacteria and/or toxins).

Bioconjugation strategies for microtoroidal optical resonators

The development of label-free biosensors with high sensitivity and specificity is of significant interest for medical diagnostics and environmental monitoring, where rapid and real-time detection of antigens, bacteria, viruses, etc., is necessary. Optical resonant devices, which have very high sensitivity resulting from their low optical loss, are uniquely suited to sensing applications. However, previous research efforts in this area have focused on the development of the sensor itself. While device sensitivity is an important feature of a sensor, specificity is an equally, if not more, important performance parameter. Therefore, it is crucial to develop a covalent surface functionalization process, which also maintains the device’s sensing capabilities or optical qualities. Here, we demonstrate a facile method to impart specificity to optical microcavities, without adversely impacting their optical performance. In this approach, we selectively functionalize the surface of the silica microtoroids with biotin, using amine-terminated silane coupling agents as linkers. The surface chemistry of these devices is demonstrated using X-ray photoelectron spectroscopy, and fluorescent and optical microscopy. The quality factors of the surface functionalized devices are also characterized to determine the impact of the chemistry methods on the device sensitivity. The resulting devices show uniform surface coverage, with no microstructural damage. This work represents one of the first examples of non-physisorption-based bioconjugation of microtoroidal optical resonators.