Fructose-selective calorimetric biosensor in flow injection analysis

All-Organic Semiconductors for Electrochemical Biosensors: An Overview of Recent Progress in Material Design

Organic semiconductors remain of major interest in the field of bioelectrochemistry for their versatility in chemical and electrochemical behavior. These materials have been tailored using organic synthesis for use in cell stimulation, sustainable energy production, and in biosensors. Recent progress in the field of fully organic semiconductor biosensors is outlined in this review, with a particular emphasis on the synthetic tailoring of these semiconductors for their intended application. Biosensors ultimately function on the basis of a physical, optical or electrochemical change which occurs in the active material when it encounters the target analyte. Electrochemical biosensors are becoming increasingly popular among organic semiconductor biosensors, owing to their good detection performances, and simple operation. The analyte either interacts directly with the semiconductor material in a redox process or undergoes a redox process with a moiety such as an enzyme attached to the semiconductor material. The electrochemical signal is then transduced through the semiconductor material. The most recent examples of organic semiconductor biosensors are discussed here with reference to the material design of polymers with semiconducting backbones, specifically conjugated polymers, and polymer semiconducting dyes. We conclude that direct interaction between the analyte and the semiconducting material is generally more sensitive and cost effective, despite being currently limited by the need to identify, and synthesize selective sensing functionalities. It is also worth noting the potential roles of highly-sensitive, organic transistor devices and small molecule semiconductors, such as the photochromic and redox active molecule spiropyran, as polymer pendant groups in future biosensor designs.

Functionalized Vesicles by Microfluidic Device

In recent years, lipid vesicles have become popular vehicles for the creation of biosensors. Vesicles can hold reaction components within a selective permeable membrane that provides an ideal environment for membrane protein biosensing elements. The lipid bilayer allows a protein to retain its native structure and function, and the membrane fluidity can allow for conformational changes and physiological interactions with target analytes. Here, we present two methods for the production of giant unilamellar vesicles (GUVs) within a microfluidic device that can be used as the basis for a biosensor. The vesicles are produced from water-in-oil-in-water (W/O/W) double emulsion templates using a nonvolatile oil phase. To create the GUVs, the oil can be removed via extraction with ethanol, or by altering the interfacial tension between the oil and carrier solution causing the oil to retract into a cap on one side of the structure, leaving behind an exposed lipid bilayer. Methods to integrate sensing elements and membrane protein pores onto the vesicles are also introduced in this work.

Flow injection analysis biosensor for urea analysis in urine using enzyme thermistor

There is a need for analytical methods capable of monitoring urea levels in urine for patients under clinical monitoring to appraise renal function. Herein, we present a practical method to quantify levels of urea in human urine samples using flow injection analysis-enzyme thermistor (FIA-ET) biosensor. The biosensor comprises a covalently immobilized enzyme urease (Jack bean) on aminated silica support, which selectively hydrolyzes the urea present in the sample. Under optimized conditions, the developed biosensor showed a linear response in the range of 10-1,000 mM, R (2) = 0.99, and response time of 90 s in 100 mM phosphate buffer (PB) (flow rate of 0.5 mL/min, sample volume of 0.1 mL, and pH 7.2). The urea-spiked human urine samples showed minimal matrix interference in the range of 10-1,000 mM. Recoveries were obtained (92.26-99.80 %) in the spiked urine samples. The reliability and reproducibility of the developed biosensor were found satisfactory with percent relative standard deviation (% RSD) = 0.741. The developed biosensor showed excellent operational stability up to 30 weeks with 20 % loss in original response when used continuously at room temperature. These results indicate that the developed biosensor could be very effective to detect low and high levels of urea in urine samples.

Biosensors - classification, characterization and new trends

Biosensors represent promising analytical tools applicable in areas such as clinical diagnosis, food industry, environment monitoring and in other fields, where rapid and reliable analyses are needed. Some biosensors were successfully implemented in the commercial sphere, but majority needs to be improved in order to overcome some imperfections. This review covers the basic types, principles, constructions and use of biosensors as well as new trends used for their fabrication.