Elif Burcu Bahadır

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.

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 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.

A comparative study of short chain and long chain mercapto acids used in biosensor fabrication: A VEGF-R1-based immunosensor as a model system

A novel impedimetric biosensor utilizing a biological receptor, vascular endothelial growth factor receptor-1 (VEGF-R1), was developed for the determination of vascular endothelial growth factor (VEGF). VEGF-R1 was covalently immobilized by coupling with 11-mercaptoundecanoic acid, which formed a self-assembled monolayer on gold electrodes. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were employed to characterize the immobilization process and to detect VEGF. To successfully construct the biosensor current, the experimental parameters were optimized. A Kramers–Kronig transform was performed on the experimental impedance data. The results obtained provided a linear response range from 1 to 6 ng/mL human VEGF. The applicability of the biosensor developed to determine VEGF in a spiked artificial human serum sample was tested. The important parameters related with the biosensors fabricated by using two different mercapto acids were compared in terms of the self-assembly processes, the activation conditions of –COOH ends, linear ranges obtained for VEGF, repeatabilities and reproducibilities, and cleaning procedures. The results of this study revealed that the length of the mercapto acids used for biosensor fabrication considerably affected the analytical performance and the practicability of the preparation of the biosensor.

Biosensor technologies for analyses of food contaminants

Consumption of safe food is very important for human health. The sensitive monitoring of contaminants, such as, chemical compounds, toxins, and pathogens is important for reducing diseases. Conventional methods, such as, chromatography and spectrophotometry for food analysis provides high reliability and very low detection limits but they are expensive, time consuming, and require specialized personnel and therefore they do not allow frequent monitoring of contaminants in food. For this reason, there is an increasing demand for robust, rapid, inexpensive alternative technologies for in situ, real-time monitoring. Owing to their high sensitivity, selectivity, biosensors have attracted attention for monitoring contaminants in food. Biosensors use enzymes, antibodies, nucleic acids, and phages as biorecognition elements. They use optic, electrochemical, and piezoelectric transduction mechanisms for the detection of contaminants. The objective of this chapter is to give a general overview about the possible application of biosensors in the food analysis field. In this chapter, the transduction principles, immobilization techniques, and analytical performances of these biosensors are summarized.

Ecotoxicological and inorganic chemicals' characterization of rainwater in an urban residential area

AbstractA survey of inorganic chemicals and acute ecotoxicity to Daphnia magna was performed in rain water samples collected in an urban area. Samples were collected from three types of origins namely ground surface contact, non-contact, collected directly from atmosphere, and roof contact. Chemical and ecotoxicological results varied with the locations and origins of the samples. Data were found to be distributed normally by means of Kolmogorov–Smirnov statistics test. All samples were found to be different from each other statistically (100% variance). None of the samples displayed any significant toxicity to Daphnia magna (<30% of immobilization after 48-h exposure time). Anyhow acute ecotoxicity data displayed statistically dependent parameters such as pH and EC, and performing chronic ecotoxicological tests would be useful to be able to assess the risk and to determine mitigation strategies for water quality control.

CHAPTER 20:Food Biosensors: Perspective, Reliability, Selectivity, Response Time, Quality Control, and Cost-Effectiveness

High-quality and safe food is very important for human health. As a consequence, accurate and sensitive detection of food contaminants has become essential. Conventionally, methods such as liquid and gas chromatography coupled with mass spectrometry and spectrophotometry are commonly used. But these methods require expensive instruments, complex pretreatment steps, specialized personnel, and large quantity of organic solvents. Such methods cannot be used to perform in situ assays. Biosensors are miniaturized analytical instruments with many merits such as simple preparation, good sensitivity, high selectivity, and portable construction. Stability, reproducibility and selectivity are key parameters that should be considered when developing and producing a biosensor. This chapter gives a general overview of the possible applications of biosensors in food analysis. Methods for the immobilization of electrodes are investigated and analytical performance criteria such as detection limit, reproducibility, stability, and response time are summarized in tables and compared in the main text.