Electrochemical detection of vascular endothelial growth factors (VEGFs) using VEGF antibody fragments modified Au NPs/ITO electrode

Organic electrochemical transistor-based immuno-sensor using platinum loaded CeO2 nanosphere-carbon nanotube and zeolitic imidazolate framework-enzyme-metal polyphenol network

This work demonstrates an organic electrochemical transistor (OECT) immuno-sensor with a detection limit down to fg mL^-1. The OECT device transforms the antibody-antigen interaction signal by using the zeolitic imidazolate framework-enzyme-metal polyphenol network nanoprobe, which can produce electro-active substance (H₂O₂) through the enzyme-catalytic reaction. The produced H₂O₂ is subsequently electrochemically oxidized at the platinum loaded CeO₂ nanosphere-carbon nanotube modified gate electrode, resulting in an amplified current response of the transistor device. This immuno-sensor realizes the selective determination of vascular endothelial growth factor 165 (VEGF₁₆₅) down to the concentration of 13.6 fg mL^-1. It also shows good applicable capacity for determining the VEGF₁₆₅ that human brain microvascular endothelial cells and U251 human glioblastomas cells secreted in the cell culture medium. The ultrahigh sensitivity of the immuno-sensor is derived from excellent performances of the nanoprobe for enzyme loading and the OECT device for H₂O₂ detection. This work may provide a general way to fabricate the OECT immuno-sensing device with high performances.

Synthesis and electrochemical study of enzymatic graphene oxide-based nanocomposite as stable biosensor for determination of bevacizumab as a medicine in colorectal cancer in human serum and wastewater fluids

This work's goal was the fabrication of a graphene oxide-based nanocomposite biosensor for the determination of bevacizumab (BVZ) as a medicine for colorectal cancer in human serum and wastewater fluids. For the fabrication electrode, graphene oxide was electrodeposited on GCE (GO/GCE), and then DNA and monoclonal anti-bevacizumab antibodies were immobilized on the GO/GCE surface, respectively (Ab/DNA/GO/GCE). Structural characterization using XRD, SEM, and Raman spectroscopy confirmed the binding of DNA to GO nanosheets and the interaction of Ab with the DNA/GO array. Electrochemical characterization of Ab/DNA/GO/GCE using CV and DPV indicated immobilization of antibodies on DNA/GO/GCE and sensitive and selective behavior of modified electrodes for determination of BVZ. The linear range was obtained 10-1100 μg/mL, and the sensitivity and detection limit values were determined to be 0.14575 μA/μg.mL^-1 and 0.02 μg/mL, respectively. To verify the applicability of the planned sensor for determination of BVZ in human serum and wastewater fluid specimens, the outcomes of DPV measurements using Ab, DNA, GO, and GCE and the results of the Bevacizumab ELISA Kit for determination of BVZ in prepared real specimens showed good conformity between the outcomes of both analyses. Moreover, the proposed sensor showed considerable assay precision with recoveries ranging from 96.00% to 98.90% and acceptable relative standard deviations (RSDs) below 5.11%, illustrating sufficiently good sensor accuracy and validity in the determination of BVZ in prepared real specimens of human serum and wastewater fluids. These outcomes demonstrated the feasibility of the proposed BVZ sensor in clinical and environmental assay applications.

Selection of Specific Aptamer against Rivaroxaban and Utilization for Label-Free Electrochemical Aptasensing Using Gold Nanoparticles: First Announcement and Application for Clinical Sample Analysis

For the first time, a novel aptamer was designed and utilized for the selective detection of rivaroxaban (RIV) using the integration of bioinformatics with biosensing technology. The selected aptamer with the sequence 5'-TAG GGA AGA GAA GGA CAT ATG ATG ACT CAC AAC TGG ACG AAC GTA CTT ATC CCC CCC AAT CAC TAG TGA ATT-3' displayed a high binding affinity to RIV and had an efficient ability to discriminate RIV from similar molecular structures. A novel label-free electrochemical aptasensor was designed and fabricated through the conjugation of a thiolated aptamer with Au nanoparticles (Au-NPs). Then, the aptasensor was successfully applied for the quantitative determination of RIV in human plasma and exhaled breath condensate (EBC) samples with limits of detection (LODs) of 14.08 and 6.03 nM, respectively. These valuable results provide ample evidence of the green electrogeneration of AuNPs on the surface of electrodes and their interaction with loaded aptamers (based on Au-S binding) towards the sensitive and selective monitoring of RIV in human plasma and EBC samples. This bio-assay is an alternative approach for the clinical analysis of RIV and has improved specificity and affinity. As far as we know, this is the first time that an electrochemical aptasensor has been verified for the recognition of RIV and that allows for the easy, fast, and precise screening of RIV in biological samples.

Design of highly stabilized nanocomposite inks based on biodegradable polymer-matrix and gold nanoparticles for Inkjet Printing

Nowadays there is a worldwide growing interest in the Inkjet Printing technology owing to its potentially high levels of geometrical complexity, personalization and resolution. There is also social concern about usage, disposal and accumulation of plastic materials. In this work, it is shown that sugar-based biodegradable polyurethane polymers exhibit outstanding properties as polymer-matrix for gold nanoparticles composites. These materials could reach exceptional stabilization levels, and demonstrated potential as novel robust inks for Inkjet based Printing. Furthermore, a physical comparison among different polymers is discussed based on stability and printability experiments to search for the best ink candidate. The University of Seville logo was printed by employing those inks, and the presence of gold was confirmed by ToF-SIMS. This approach has the potential to open new routes and applications for fabrication of enhanced biomedical nanometallic-sensors using stabilized AuNP.

Biosensors for Detection of Human Placental Pathologies: A Review of Emerging Technologies and Current Trends

Substantial growth in the biosensor research has enabled novel, sensitive and point-of-care diagnosis of human diseases in the last decade. This paper presents an overview of the research in the field of biosensors that can potentially predict and diagnosis of common placental pathologies. A survey of biomarkers in maternal circulation and their characterization methods is presented, including markers of oxidative stress, angiogenic factors, placental debris, and inflammatory biomarkers that are associated with various pathophysiological processes in the context of pregnancy complications. Novel biosensors enabled by microfluidics technology and nanomaterials is then reviewed. Representative designs of plasmonic and electrochemical biosensors for highly sensitive and multiplexed detection of biomarkers, as well as on-chip sample preparation and sensing for automatic biomarker detection are illustrated. New trends in organ-on-a-chip based placental disease models are highlighted to illustrate the capability of these in vitro disease models in better understanding the complex pathophysiological processes, including mass transfer across the placental barrier, oxidative stress, inflammation, and malaria infection. Biosensor technologies that can be potentially embedded in the placental models for real time, label-free monitoring of these processes and events are suggested. Merger of cell culture in microfluidics and biosensing can provide significant potential for new developments in advanced placental models, and tools for diagnosis, drug screening and efficacy testing.

An epoxysilane modified indium tin oxide electrode for the determination of PAK 2: Application in human serum samples

In this study, a sensitive immunosensor was developed for the first time for p21-activated kinase 2 (PAK 2) detection. In the design of the immunosensor, 3-glycidoxypropyltrimethoxysilane (GPTMS) was utilized as an ITO electrode modification material for anti-PAK 2 antibody immobilization. This molecule had epoxy group, which was reactive to amino groups of antibodies. Anti-PAK 2 antibodies were also used as biomolecules for sensitive interaction for PAK 2 antigen. In the presence of PAK 2 antigens, high impedance signal was observed when the process followed by using Electrochemical Impedance Spectroscopy technique (EIS). Apart from EIS technique, Cyclic Voltammetry (CV), Square Wave Voltammetry (SWV) and Single Frequency Impedance (SFI) techniques were utilized. Microscopic surface characterizations of immunosensor fabrication steps were performed by using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The immunosensor exhibited good sensitivity and selectivity for PAK 2 antigen detection. A linear calibration curve between EIS response and PAK 2 concentration was obtained in the range of 0.005-0.075 pg/mL with the detection limit of 1.5 fg/mL. It had good repeatability, excellent reproducibility and high stability. Additionally, this immunosensor can be reused by simple application protocol. Furthermore, it had good recovery for PAK 2 antigen detection in human serum samples. The good recovery illustrated that the developed immunosensor was a promising tool for PAK 2 detection in practical applications.

A microfluidic competitive immuno-aggregation assay for high sensitivity cell secretome detection

We report a high-sensitivity cell secretome detection method using competitive immuno-aggregation and a micro-Coulter counter. A target cell secretome protein competes with anti-biotin-coated microparticles (MPs) to bind with a biotinylated antibody (Ab), causing decreased aggregation of the functionalized MPs and formation of a mixture of MPs and aggregates. In comparison, without the target cell secretome protein, more microparticles are functionalized, and more aggregates are formed. Thus, a decrease in the average volume of functionalized microparticles/aggregates indicates an increase in cell secretome concentration. This volume change is measured by the micro-Coulter counter, which is used to quantitatively estimate the cell secretome concentration. Vascular endothelial growth factor (VEGF), one of the key cell secretome proteins that regulate angiogenesis and vascular permeabilization, was used as the target protein to demonstrate the sensing principle. A standard calibration curve was generated by testing samples with various VEGF concentrations. A detection range from 0.01 ng/mL to 100.00 ng/mL was achieved. We further demonstrated the quantification of VEGF concentration in exogenous samples collected from the secretome of human mesenchymal stem cells (hMSCs) at different incubation times. The results from the assay agree well with the results of a parallel enzyme-linked immunoabsorbent assay (ELISA) test, indicating the specificity and reliability of the competitive immuno-aggregation assay. With its simple structure and easy sample preparation, this assay not only enables high sensitivity detection of VEGF but also can be readily extended to other types of cell secretome analysis as long as the specific Ab is known.

A label-free electrochemical biosensor for direct detection of RACK 1 by using disposable, low-cost and reproducible ITO based electrode

In this study we designed an ultrasensitive electrochemical immunosensor for RACK 1 detection using 11-cyanoundecyltrimethoxysilane (11-CUTMS) as a immobilization matrix to immobilize biorecognition element. The used silane agent (11-CUTMS) provides a favorable platform for efficient loading of anti-RACK 1 antibody. The effective loading of the biorecognition element on the 11-CUTMS matrix was monitored by scanning electron microscopy (SEM), atomic force microscopy (AFM) images and fourier transform infrared spectroscopy (FTIR) spectra. The electrochemical characterization of the immunosensor was performed by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Moreover, biorecognition interaction between anti-RACK1 antibodies and RACK1 antigens was monitored by using single frequency technique (SFI). The operating conditions, calibration curves obtained during optimization of experiments and reproducibility of the proposed impedimetric RACK1 biosensor are also investigated and discussed. The electrochemical immunosensor illustrated a sensitive response to RACK 1 antigen with detection limit of 10.8 fg/mL and in the linear range of 0.036-2.278 pg/mL (R² = 0.999). Owing to high specificity, good reproducibility, long stability and reusability, the fabricated immunosensor will provide a sensitive, selective approach to RACK 1 detection. Furthermore, the practical applicability in human serum samples were investigated with a satisfactory result.

A sensitive and disposable electrochemical immunosensor for detection of SOX2, a biomarker of cancer

A novel, sensitive, disposable indium tin oxide (ITO)-based electrochemical immunosensor was developed firstly for simple, rapid determination of Sex-determining region Y-box 2 (SOX2). SOX2 is a cancer biomarker and used for detecting small cell lung cancer, lung adenocarcinoma, squamous cell carcinoma, skin cancer, prostate cancer, and breast cancer. In this study, a disposable ITO thin film based electrode was used as working electrode for biosensing the interaction between SOX2 antigen and anti-SOX2 antibody. In this study, carboxyethylsilanetriol (CTES) was also utilized for electrode modifying so as to obtain self-assembled monolayers. The formed self-assembled monolayers were activated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) chemistry and they were used as a heterobifunctional crosslinker and activator, respectively. Anti-SOX2 antibody was used as a biorecognition molecule and was covalently immobilized onto the ITO thin film modified with CTES. Immobilization steps were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optimum immobilization conditions such as antibody concentration, antibody and antigen incubation times were examined for the best sensitivity of the immunosensor. Under optimal conditions, this immunosensor had a wide linear detection range (25fg/mL-2pg/mL) with a detection limit as low as 7fg/mL SOX2. Furthermore, the developed SOX2 immunosensor had good storage stability (79.36% of initial activity after 9 weeks), repeatability (3.88% of RSD) and reproducibility (4.25% of RSD). Our developed immunosensor has an acceptable performance for detection of SOX2 antigen, exhibits low detection limit, and has selective and reproducible results in immunoreaction analysis.

Prospects of electrochemical immunosensors for early diagnosis of preeclampsia

Preeclampsia is a vascular multisystem disorder that accounts for varying degree of morbidity and mortality of mother and the fetus. This can be significantly averted if diagnosed at an early (18-20 weeks) stage of gestation, as there is no known way to prevent preeclampsia. In spite of extensive work on biomarker discovery, the existing method for its detection is mostly based on colorimetric immunoassays whose sensitivity is ranging in nanomolar range. Further, it has also been observed that change in the expression of a single biomarker is not sufficient to diagnose this condition. So, for early diagnosis (by 18-20 weeks), an immuno-diagnostic platform with detection limits in picomolar range and beyond along with the ability to do simultaneous detection of multiple analyte would be of great importance. A nano-immunosensors with an electrochemical readout system can be a potential alternative that promises for the ultrasensitive detection of analyte with high specificity as well as suitability for on-site analysis. Coupling the lateral flow technology with immunosensors would make it feasible to detect more than one biomarker simultaneously on a microchip. This review intends to summarize the potential preeclampsia biomarkers, limitations of existing diagnostic methods along with the recent advancements, and prospects to develop electrochemical immunosensors for early clinical diagnosis.

Label-free, ITO-based immunosensor for the detection of a cancer biomarker: Receptor for Activated C Kinase 1

A new, quite sensitive disposable immunosensor, based on the anti-RACK1 antibody, was developed for the determination of Receptor for Activated C Kinase 1 (RACK1) for the first time.

Emotion-on-a-chip (EOC): evolution of biochip technology to measure human emotion using body fluids

Recent developments in nano/micro technology have made it possible to construct small-scale sensing chips for the analysis of biological markers such as nucleic acids, proteins, small molecules, and cells. Although biochip technology for the diagnosis of severe physiological diseases (e.g., cancer, diabetes, and cardiovascular disease) has been extensively studied, biochips for the monitoring of human emotions such as stress, fear, depression, and sorrow have not yet been introduced, and the development of such a biochip is in its infancy. Emotion science (or affective engineering) is a rapidly expanding engineering/scientific discipline that has a major impact on human society. The growing interest in the integration of emotion science and engineering is a result of the recent trend of merging various academic fields. In this paper we discuss the potential importance of biochip technology in which human emotion can be precisely measured in real time using body fluids such as blood, saliva, urine, or sweat. We call these biochips emotion-on-a-chip (EOC). The EOC system consists of four parts: (1) collection of body fluids, (2) separation of emotional markers, (3) detection of optical or electrical signals, and (4) display of results. These techniques provide new opportunities to precisely investigate human emotion. Future developments in EOC techniques will combine social and natural sciences to expand their scope of study.