Clinical detection of Hepatitis C viral infection by yeast-secreted HCV-core:Gold-binding-peptide

Straightforward fabrication of electrochemical aptasensors with outstanding antifouling performance

Self-assembled monolayers (SAMs) are popular tools for many different applications - SAMs of commercially available chemicals that convincingly inhibit unspecific binding for electrochemical sensors, however, have yet to be developed. While adsorption of foulants prohibits the reliable analysis of biological samples, unspecific binding of the analyte similarly impedes the investigation of binding characteristics from buffer solutions. In this communication, diglycolamine is introduced for the modification of electrodes with outstanding antifouling performance. The presented sensor design, solely consisting of diglycolamine and an aptamer of choice, convinces with its ease of preparation, low cost, and, most importantly, an exceptional specificity. The latter was found to rely on a gentle but potent cleaning of the electrodes, as only our optimized cleaning procedure granted the diglycolamine layer its excellent fouling minimization performance, while literature standard protocols failed to do so. Each step of the sensor fabrication protocol was optimized by electrochemical impedance spectroscopy, while square-wave voltammetry, surface-enhanced Raman spectroscopy, and zeta potential measurement were performed for further characterization. The presented approach of surface modification with diglycolamine is a versatile method applicable not just to electrochemical measurements, but to a variety of other detection techniques, too, and has the potential to change the way we investigate binding characteristics and fabricate sensors for the analysis of complex biological samples.

Development of Nanobody-Displayed Whole-Cell Biosensors for the Colorimetric Detection of SARS-CoV-2

The accurate and effective detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential to preventing the spread of infectious diseases and ensuring human health. Herein, a nanobody-displayed whole-cell biosensor was developed for colorimetric detection of SARS-CoV-2 spike proteins. Serving as bioreceptors, yeast surfaces were genetically engineered to display SARS-CoV-2 binding of llama-derived single-domain antibodies (nanobodies) with high capture efficiency, facilitating the concentration and purification of SARS-CoV-2. Gold nanoparticles (AuNPs) employed as signal transductions were functionalized with horseradish peroxidase (HRP) and anti-SARS monoclonal antibodies to enhance the detection sensitivity. In the presence of SARS-CoV-2 spike proteins, the sandwiched binding will be formed by linking engineered yeast, SARS-CoV-2 spike proteins, and reporter AuNPs. The colorimetric signal was generated by the enzymatic reaction of HRP and its corresponding colorimetric substrate/chromogen system. At the optimal conditions, the developed whole-cell biosensor enables the sensitive detection of SARS-CoV-2 spike proteins in a linear range from 0.01 to 1 μg/mL with a limit of detection (LOD) of 0.037 μg/mL (about 4 × 108 virion particles/mL). Furthermore, the whole-cell biosensor was demonstrated to detect the spike protein of different SARS-CoV-2 variants in human serum, providing new possibilities for the detection of future SARS-CoV-2 variants.

Multifunctionalized flower-like gold nanoparticles with high chemiluminescence for label-free sensing of the hepatitis C virus core protein

Developing functionalized nanomaterials with strong chemiluminescence (CL) properties is highly significant for ultrasensitive bioanalysis. Here, we report chitosan (CS), luminol, and Co²⁺-functionalized flower-like gold nanoparticles (Co²⁺/CS/Lum/AuNFs) with strong CL for the label-free sensing of the HCV core protein (HCVcp). The Co²⁺/CS/Lum/AuNFs exhibited a greatly enhanced CL emission at around 425 nm, which is 50 times stronger than that of CS/Lum/AuNFs, and is superior to other commonly reported CL nanomaterials. The HCVcp aptamer (HCVcp-apt) further functionalized the surface of the Co²⁺/CS/Lum/AuNFs through electrostatic interactions blocked the Co²⁺ catalytic site, depressing the CL. Owing to the high affinity of HCVcp for the HCVcp-apt, the presence of HCVcp predominated its binding and effectively separated the HCVcp-apt from the surface of the Co²⁺/CS/Lum/AuNFs, so that the CL intensity was significantly enhanced. As the results showed, the HCVcp-apt/Co²⁺/CS/Lum/AuNFs were successfully used to detect the HCVcp in human serum samples with a linear range from 0.50 ng mL^-1 to 1.00 μg mL^-1, a detection limit of 0.16 ng mL^-1 and an excellent selectivity over other analogs. The strategy is universal for the development of the ultrasensitive detection of other proteins in the field of early disease diagnostics.

Biomedical applications of solid-binding peptides and proteins

Over the past decades, solid-binding peptides (SBPs) have found multiple applications in materials science. In non-covalent surface modification strategies, solid-binding peptides are a simple and versatile tool for the immobilization of biomolecules on a vast variety of solid surfaces. Especially in physiological environments, SBPs can increase the biocompatibility of hybrid materials and offer tunable properties for the display of biomolecules with minimal impact on their functionality. All these features make SBPs attractive for the manufacturing of bioinspired materials in diagnostic and therapeutic applications. In particular, biomedical applications such as drug delivery, biosensing, and regenerative therapies have benefited from the introduction of SBPs. Here, we review recent literature on the use of solid-binding peptides and solid-binding proteins in biomedical applications. We focus on applications where modulating the interactions between solid materials and biomolecules is crucial. In this review, we describe solid-binding peptides and proteins, providing background on sequence design and binding mechanism. We then discuss their application on materials relevant for biomedicine (calcium phosphates, silicates, ice crystals, metals, plastics, and graphene). Although the limited characterization of SBPs still represents a challenge for their design and widespread application, our review shows that SBP-mediated bioconjugation can be easily introduced into complex designs and on nanomaterials with very different surface chemistries.

Nanomaterials for Cortisol Sensing

Space represents one of the most dangerous environments for humans, which can be affected by high stress levels. This can lead to severe physiological problems, such as headaches, gastrointestinal disorders, anxiety, hypertension, depression, and coronary heart diseases. During a stress condition, the human body produces specific hormones, such as dopamine, adrenaline, noradrenaline, and cortisol. In particular, the control of cortisol levels can be related to the stress level of an astronaut, particularly during a long-term space mission. The common analytical methods (HPLC, GC-MS) cannot be used in an extreme environment, such as a space station, due to the steric hindrance of the instruments and the absence of gravity. For these reasons, the development of smart sensing devices with a facile and fast analytical protocol can be extremely useful for space applications. This review summarizes the recent (from 2011) miniaturized sensoristic devices based on nanomaterials (gold and carbon nanoparticles, nanotubes, nanowires, nano-electrodes), which allow rapid and real-time analyses of cortisol levels in biological samples (such as saliva, urine, sweat, and plasma), to monitor the health conditions of humans under extreme stress conditions.

MIP-based electrochemical sensor for direct detection of hepatitis C virus via E2 envelope protein

Hepatitis C is the most common liver disease caused by Hepatitis C virus (HCV), and can evolve into serious health problems e.g. cirrhosis and hepatocellular carcinoma. Nowadays, the initial stage of the disease cannot be practically diagnosed, representing thus an extremely important problem of modern public health care. This study is aimed at the development of a sensor for direct detection of HCV. The sensor utilizes a synthetic recognition element prepared by the technology of molecular imprinting and representing a molecularly imprinted polymer (MIP) having molecular recognition sites of HCV envelope protein E2 (E2-MIP). E2-MIP integrated into an electrochemical sensor platform allows quantitative evaluation of binding of free E2 protein as well as HCV-mimetic particles (HCV-MPs) in human plasma with LOD value of 4.6 × 10^-4 ng/mL (for HCV-MPs). The developed electrochemical HCV sensor represents a simple, fast and inexpensive alternative for the existing methods of HCV detection and paves the way for the point-of care diagnostics of Hepatitis C.

Cortisol Detection in Undiluted Human Serum Using a Sensitive Electrochemical Structure-Switching Aptamer over an Antifouling Nanocomposite Layer

There is a strong and growing need to monitor stress biomarkers in vivo for real-time emotional and wellness assessment. Toward this, we report a reagent-free electrochemical aptasensor with a nanocomposite antifouling layer for sensitive and continuous detection of cortisol in human serum. A thiolated, methylene blue (MB)-tagged conformation-switching aptamer was immobilized over a gold nanowire (AuNW) nanocomposite to capture cortisol and generate a signal proportional to the cortisol concentration. The signal is recorded through differential pulse voltammetry (DPV) and chronoamperometry. The aptasensor exhibited a sensitive response with 0.51 and 0.68 nM detection limits in spiked buffer and undiluted serum samples, respectively. Interference from other structurally similar analogs, namely, epinephrine and cholic acid, was negligible (<10%). The developed nanocomposite-based aptasensor showed excellent stability in undiluted human serum, outperforming several other nanocomposite materials even after prolonged exposure. This work lays the foundation for new biosensor formats such as implantable and wearable sensors.

Nano-engineered screen-printed electrodes: A dynamic tool for detection of viruses

There is a growing interest in the development of portable, cost-effective, and easy-to-use biosensors for the rapid detection of diseases caused by infectious viruses: COVID-19 pandemic has highlighted the central role of diagnostics in response to global outbreaks. Among all the existing technologies, screen-printed electrodes (SPEs) represent a valuable technology for the detection of various viral pathogens. During the last five years, various nanomaterials have been utilized to modify SPEs to achieve convincing effects on the analytical performances of portable SPE-based diagnostics. Herein we would like to provide the readers a comprehensive investigation about the recent combination of SPEs and various nanomaterials for detecting viral pathogens. Manufacturing methods and features advances are critically discussed in the context of early-stage detection of diseases caused by HIV-1, HBV, HCV, Zika, Dengue, and Sars-CoV-2. A detailed table is reported to easily guide readers toward the "right" choice depending on the virus of interest.

Electronic and electrochemical viral detection for point-of-care use: A systematic review

Detecting viruses, which have significant impact on health and the economy, is essential for controlling and combating viral infections. In recent years there has been a focus towards simpler and faster detection methods, specifically through the use of electronic-based detection at the point-of-care. Point-of-care sensors play a particularly important role in the detection of viruses. Tests can be performed in the field or in resource limited regions in a simple manner and short time frame, allowing for rapid treatment. Electronic based detection allows for speed and quantitative detection not otherwise possible at the point-of-care. Such approaches are largely based upon voltammetry, electrochemical impedance spectroscopy, field effect transistors, and similar electrical techniques. Here, we systematically review electronic and electrochemical point-of-care sensors for the detection of human viral pathogens. Using the reported limits of detection and assay times we compare approaches both by detection method and by the target analyte of interest. Compared to recent scoping and narrative reviews, this systematic review which follows established best practice for evidence synthesis adds substantial new evidence on 1) performance and 2) limitations, needed for sensor uptake in the clinical arena. 104 relevant studies were identified by conducting a search of current literature using 7 databases, only including original research articles detecting human viruses and reporting a limit of detection. Detection units were converted to nanomolars where possible in order to compare performance across devices. This approach allows us to identify field effect transistors as having the fastest median response time, and as being the most sensitive, some achieving single-molecule detection. In general, we found that antigens are the quickest targets to detect. We also observe however, that reports are highly variable in their chosen metrics of interest. We suggest that this lack of systematisation across studies may be a major bottleneck in sensor development and translation. Where appropriate, we use the findings of the systematic review to give recommendations for best reporting practice.

An electrochemical biosensor for direct detection of hepatitis C virus

This paper is aimed at the development of a biosensor for direct detection of Hepatitis C virus (HCV) surface antigen: envelope protein (E2). A recombinant LEL fragment of biological cell receptor CD81 and two short synthetic peptides imitating the fragment of LEL sequence of CD81 (linear and loop-like peptides) capable of specific binding to E2 were tested as molecular recognition elements of the biosensor. For this purpose the selected ligands were immobilized to the surface of a screen-printed electrode utilized as an electrochemical sensor platform. The immobilization parameters such as the ligand concentration and the immobilization time were carefully optimized for each ligand. Differential pulse voltammetry used to evaluate quantitatively binding of E2 to the ligands revealed their similar binding affinity towards E2. Thus, the linear peptide was selected as a less expensive and easily prepared ligand for the HCV biosensor preparation. The resulting HCV biosensor demonstrated selectivity towards E2 in the presence of interfering protein, conalbumin. Moreover, it was found that the prepared biosensor effectively detected E2 bound to hepatitis C virus-mimetic particles (HC VMPs) at LOD value of 2.1∙10^-5 mg/mL both in 0.01 M PBS solution (pH 7.4) and in simulated blood plasma.

A novel HCV electrochemical biosensor based on a polyaniline@Ni-MOF nanocomposite

A novel label-free electrochemical biosensor constructed using a polyaniline@nickel metal–organic framework (Ni-MOF) nanocomposite for direct detection of HCV-RNA.

Plasmonic nanoplatform for point-of-care testing trace HCV core protein

Early diagnosis of hepatitis C virus (HCV) infection is still urgently desired as there is a global healthy burden and no vaccine available. In this work, a plasmonic nanoplatform was engineered with catalytic hairpin assembly (CHA) amplification reaction specifically of HCV core protein (HCVcp), G-quadruplex/hemin DNAzyme and nanofibrous membrane together. HCVcp was detected in whole serum at the ultralow concentration of 1.0 × 10^-4 pg/mL with naked eye. By testing serum samples from 30 donors with different viral loads, detection sensitivity of the plasmonic nanoplatform turned out to be much better than that of the commercial ELISA kit. In addition, the plasmonic nanoplatform exhibited high specificity, excellent reusability and long-term stability. Naked-eye detection based on the plasmonic nanoplatform is expected to have potential applications in point-of-care testing (POCT) and early diagnosis of hepatitis C and other infectious diseases.