Mustafa Kemal Sezgintürk

Applications of commercial biosensors in clinical, food, environmental, and biothreat/biowarfare analyses.

The lack of specific, low-cost, rapid, sensitive, and easy detection of biomolecules has resulted in the development of biosensor technology. Innovations in biosensor technology have enabled many biosensors to be commercialized and have enabled biomolecules to be detected onsite. Moreover, the emerging technologies of lab-on-a-chip microdevices and nanosensors offer opportunities for the development of new biosensors with much better performance. Biosensors were first introduced into the laboratory by Clark and Lyons. They developed the first glucose biosensor for laboratory conditions. Then in 1973, a glucose biosensor was commercialized by Yellow Springs Instruments. The commercial biosensors have small size and simple construction and they are ideal for point-of-care biosensing. In addition to glucose, a wide variety of metabolites such as lactate, cholesterol, and creatinine can be detected by using commercial biosensors. Like the glucose biosensors (tests) other commercial tests such as for pregnancy (hCG), Escherichia coli O157, influenza A and B viruses, Helicobacter pylori, human immunodeficiency virus, tuberculosis, and malaria have achieved success. Apart from their use in clinical analysis, commercial tests are also used in environmental (such as biochemical oxygen demand, nitrate, pesticide), food (such as glutamate, glutamine, sucrose, lactose, alcohol, ascorbic acid), and biothreat/biowarfare (Bacillus anthracis, Salmonella, Botulinum toxin) analysis. In this review, commercial biosensors in clinical, environmental, food, and biowarfare analysis are summarized and the commercial biosensors are compared in terms of their important characteristics. This is the first review in which all the commercially available tests are compiled together.

Development of an impedimetric aflatoxin M1 biosensor based on a DNA probe and gold nanoparticles.

The present work describes the construction and application of a new DNA biosensor for detection of aflatoxin M1. In order to immobilize a thiol-modified single stranded DNA (ss-HSDNA) probe that specifically bound aflatoxin M1, a self-assembled monolayer of cysteamine and gold nanoparticles on the SAM were prepared on gold electrodes, layer-by-layer. The assembly processes of cysteamine, gold nanoparticles, and ss-HSDNA were monitored with the help of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. K3[Fe(CN)6]/K4[Fe(CN)6] solution was used as a redox probe for electrochemical measurements. The biosensor provided a linear response to aflatoxin M1 over the concentration range of 1-14 ng/mL with a standard deviation of ±0.36 ng/mL. Finally, the biosensor was applied to a series of real milk samples.

Applications of electrochemical immunosensors for early clinical diagnostics

Cancer and cardiovascular diseases are the major threats to global health. Hence, there is a growing demand for a range of portable, rapid and low cost biosensing devices for the detection of these diseases. Electrochemical immunosensors are simple, rapid, reliable and inexpensive devices and they have sensitive detection limits to monitor both levels of the biomarkers in normal and patient serum. Due to the specific binding of antibody to its corresponding antigen, immunosensors based on antibody-antigen interaction are one of the most widely used analytical techniques in the quantitative detection of these diseases. The changed levels of markers in patients are associated with diseases. In this article the biosensors and biomarkers, which were commonly used in terms of monitoring the diagnosis and treatment of cancer and cardiac diseases, are reviewed. In addition, the developed biosensors are compared in terms of precision, reproducibility, regeneration, stability and specificity.

Electrochemical biosensors for hormone analyses.

Electrochemical biosensors have a unique place in determination of hormones due to simplicity, sensitivity, portability and ease of operation. Unlike chromatographic techniques, electrochemical techniques used do not require pre-treatment. Electrochemical biosensors are based on amperometric, potentiometric, impedimetric, and conductometric principle. Amperometric technique is a commonly used one. Although electrochemical biosensors offer a great selectivity and sensitivity for early clinical analysis, the poor reproducible results, difficult regeneration steps remain primary challenges to the commercialization of these biosensors. This review summarizes electrochemical (amperometric, potentiometric, impedimetric and conductometric) biosensors for hormone detection for the first time in the literature. After a brief description of the hormones, the immobilization steps and analytical performance of these biosensors are summarized. Linear ranges, LODs, reproducibilities, regenerations of developed biosensors are compared. Future outlooks in this area are also discussed.

A new impedimetric biosensor utilizing VEGF receptor-1 (Flt-1): early diagnosis of vascular endothelial growth factor in breast cancer.

A new impedimetric biosensor, based on the use of vascular endothelial growth factor receptor-1 (VEGF-R1), was developed for the determination of vascular endothelial growth factor (VEGF). VEGF-R1 was immobilized through covalent coupling with 3-mercaptopropionic acid which formed a self-assembled monolayer on gold electrodes. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy techniques were employed to characterize the immobilization process and to detect VEGF. To successfully construct the biosensor current, experimental parameters were optimized. Kramers-Kronig Transform was performed on the experimental impedance data. The obtained results provided a linear response range from 10 to 70 pg/mL human VEGF. The applicability of the developed biosensor in the determination of VEGF in a spiked artificial human serum sample was experienced, yielding average recovery of 101%, in that order, with an average relative deviation value less than 5%.

Introducing a new method for evaluation of the interaction between an antigen and an antibody: Single frequency impedance analysis for biosensing systems

This paper illustrates the application of an antibody, anti-parathyroid hormone (anti-PTH), as a bioreceptor in a biosensor system for the first time, and demonstrates how this biosensor can be used in parathyroid hormone (PTH) determination. The interaction between the biosensor and parathyroid hormone was firstly investigated by a novel electrochemical method, single frequency impedance analysis. The biosensor was based on the gold electrode modified by cysteine self-assembled monolayers. Anti-PTH was covalently immobilized onto cysteine layer by using an EDC/NHS couple. The immobilization of anti-PTH was monitored by cyclic voltammetry and electrochemical impedance spectroscopy techniques. The performance of the biosensor was evaluated in terms of linearity, sensitivity, repeatability and reproducibility, after a few important optimization studies were carried out. In particular, parathyroid hormone was detected within a linear range of 10-60 fg/mL. Kramers-Kronig transform was also performed on the impedance data. The specificity of the biosensor was also evaluated. The biosensor was validated by using a complementary reference technique. Lastly the developed biosensor was used to monitor PTH levels in artificial serum samples.

Ultrasensitive electrochemical detection of cancer associated biomarker HER3 based on anti-HER3 biosensor

The development of a new impedimetric biosensor for the detection of HER3, based on self-assembled monolayers (SAMs) of 4-aminothiophenol on gold electrodes, is reported. Anti-HER3 was used as a biorecognition element for the first time in an impedimetric biosensor. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were applied to characterize the immobilization process and to detect HER3. To provide the best biosensor response all experimental parameters were optimized. In addition, Kramers-Kronigs transform was also performed on the immobilization and measurement processes successfully. The biosensor had a linear detection range of 0.4-2.4 pg/mL. The chrono-impedance technique to real time monitor the interaction between HER3 and anti-HER3 is also implemented. The biosensor has exhibited good repeatability and reproducibility. To demonstrate the feasibility of the biosensor in practical analysis, the artificial serum samples were experienced.

A review on impedimetric biosensors

Electrochemical impedance spectroscopy (EIS) is a sensitive technique for the analysis of the interfacial properties related to biorecognition events such as reactions catalyzed by enzymes, biomolecular recognition events of specific binding proteins, lectins, receptors, nucleic acids, whole cells, antibodies or antibody-related substances, occurring at the modified surface. Many studies on impedimetric biosensors are focused on immunosensors and aptasensors. In impedimetric immunosensors, antibodies and antigens are bound each other and thus immunocomplex is formed and the electrode is coated with a blocking layer. As a result of that electron transfer resistance increases. In impedimetric aptasensors, impedance changes following the binding of target sequences, conformational changes, or DNA damages. Impedimetric biosensors allow direct detection of biomolecular recognition events without using enzyme labels. In this paper, impedimetric biosensors are reviewed and the most interesting ones are discussed.

AuNPs modified, disposable, ITO based biosensor: Early diagnosis of heat shock protein 70.

This paper describes a novel, simple, and disposable immunosensor based on indium-tin oxide (ITO) sheets modified with gold nanoparticles to sensitively analyze heat shock protein 70 (HSP70), a potential biomarker that could be evaluated in diagnosis of some carcinomas. Disposable ITO coated Polyethylene terephthalate (PET) electrodes were used and modified with gold nanoparticles in order to construct the biosensors. Optimization and characterization steps were analyzed by electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Surface morphology of the biosensor was also identified by electrochemical methods, scanning electron microscopy (SEM), and atomic force microscopy (AFM). To interpret binding characterization of HSP70 to anti-HSP70 single frequency impedance method was successfully operated. Moreover, the proposed HSP70 immunosensor acquired good stability, repeatability, and reproducibility. Ultimately, proposed biosensor was introduced to real human serum samples to determine HSP70 sensitively and accurately.

Electrochemical biosensor based on self-assembled monolayers modified with gold nanoparticles for detection of HER-3.

We have developed a new immunological biosensor for ultrasensitive quantification of human epidermal growth factor receptor-3(HER-3). In order to construct the biosensor, the gold electrode surface was layered with, hexanedithiol, gold nanoparticles, and cysteamine, respectively. Anti-HER-3 antibody was covalently attached to cysteamine by glutaraldehyde and used as a bioreceptor in a biosensor system for the first time by this study. Surface characterization was obtained by means of electrochemical impedance spectroscopy and voltammetry. The proposed biosensor showed a good analytical performance for the detection of HER-3 ranging from 0.2 to 1.4 pg mL(-1). Kramers-Kronig transform was performed on the experimental impedance data. Moreover, in an immunosensor system, the single frequency impedance technique was firstly used for characterization of interaction between HER-3 and anti-HER-3. Finally the presented biosensor was applied to artificial serum samples spiked with HER-3.