Enzyme biosensors screen-printed sensors

Biosensors based on enzymes have high sensitivity and selectivity. A variety of microbial biosensors have also been developed. However, it still remains a great challenge to develop a rapid, inexpensive but sensitive method for real samples. Compared to enzymatic biosensors, development of a highly satisfactory microbial biosensor is still hampered because they suffer from long response time, low sensitivity, and poor selectivity. The trends for the development of biosensors lie in miniaturization of the devices, nanotechnology, and biotechnology. Disposable screen-printed sensors have been developed for industrial wastes or natural water. Metal nanoparticles can enhance the electron transfer between redox center in proteins and electrode surface and show promise for detection... 

Biosensors ai e widely used to the detection of hazardous contaminants in foodstuffs, soil and fresh waters. Due to high sensitivity, simple design, low cost and real-time measurement mode biosensors ai e considered as an alternative to conventional analytical techniques, e.g. GC or HPLC. Although the sensitivity and selectivity of contaminant detection is mainly determined by a biological component, i.e. enzyme or antibodies, the biosensor performance can be efficiently controlled by the optimization of its assembly and working conditions. In this report, the prospects to the improvement of pesticide detection with cholinesterase sensors based on modified screen-printed electrodes are summarized. The following opportunities for the controlled improvement of analytical characteristics of anticholinesterase pesticides ai e discussed ... 

Levels of lactate in buttermilk and yoghurt (and blood) were estimated using disposable sensors formed from screen-printed graphite laminated between two polymer sheets [18]. Platinum (deposited by sputter-coating) was the transducing surface. Layers of Nation were added to reduce interference and were surmounted by lactate oxidase in a mixture of polyethyleneimine and poly (carbamoyl) sulphonate hydrogel. The samples were measured in stirred buffer. A good correlation between biosensor results and those obtained with an enzyme kit was claimed but the data had a considerable amount of scatter—if the enzyme kit is taken as the reference method then a more severe analysis of the biosensor results [33] would not have shown them in a... 

As mediators different molecules can be applied, e.g. ferrocene, mthenium (111) hexamine or tetrathiafulvalene, which are reoxidized on an electrochemical electrode, preferably carbon (Cass et al. 1984). Such electrochemical working principle allows the miniaturization of a biosensor using screen-printed or thin-film electrodes with adsorbed or immobilized enzymes also facilitating mass production for creating disposable glucose sensors with revenues of several million euros per anno. 

Abstract. The biosensors described in this work, for the monitoring of pesticides, are based on acetylcholinesterase immobilized on the surface of screen-printed electrodes. The principle of the biosensor is that the degree of inhibition of an enzyme sensor by a pesticide is dependent on the concentration of that pesticide. The DPV technique was used as a detection method and methyl-paraoxon as a reference pesticide for sensor calibration. 

Most biosensors based on AChE have the enzymes immobilized on the surface of the sensor. The inhibition reaction being irreversible, the membrane with immobilized enzyme has to be replaced after several measurements or the biosensor can be use for only one determination. Due to this fact, the researchers tried to realize pesticide biosensors with a renewable surface or disposable biosensors based on screen-printed electrodes (SPE). The screen-printing technology provides a simple, fast and inexpensive method for mass production of disposable biosensors for different biomolecules starting with glucose, lactate and finishing with environmental contaminants as pesticides (Kulys et al., 1991) and herbicides (Skladal, 1992). 

HPLC with UV-based diode array detection (DAD-UV) or electrochemical detection is normally used to determine ascorbic acid. Many types of electrochemical determinations of ascorbic acid have been proposed. Although the electrochemical determinations using enzyme-based biosensors exhibited high specificity and sensitivity, these methods suffer in the fabrication of the electrodes and in automatic analysis. Recently, chemically modified screen-printed electrodes have been constructed for the determination of ascorbic acid. This is one of the most promising routes for mass production of inexpensive, reproducible, and reliable electrochemical sensors. 

Tliis work demonstrates the potential for application of potentiometric enzyme electrodes based on mediatorless enzyme electrocatalysis for fast and sensitive assay of organophosphorus pesticides. The sensing element based on screen-printed carbon material pomits mass fabrication of the electrodes at a low cost which is essential for the disposable sensor concept. The biosensor does not require any low-molecular weight mediator and can be arranged as an all-solid-state device. Such electrodes. 

A sensor array for monitoring indicators of mannnalian cell metabolic status has been reported by Pemberton et al. [33], and is based on both enzyme-modified elements and chemical sensors for temperature, pH, and dissolved oxygen. The array, fabricated in a silicon platform using MEMS technology, consists of five-well sensor strips with a multipotentiostat to switch between potentiometric and amperometric measurement modes. Screen-printed biosensors for glucose and lactate were grafted onto two of the weUs. The authors envision applications to cell culture and cytotoxicity studies. 

The following is a short list of some of these potential applications for graphene electronics—touch-screens, conductive ink for electronic printing, transparent conductors, transistors, heat sinks energy—polymer solar cells, catalysts in fuel cells, battery electrodes, supercapacitors medicine/biotechnology —artificial muscle, enzyme and DNA biosensors, photoimaging aeronautics—chemical sensors (for explosives) and nanocomposites for aircraft structural components (Section 16.16). 

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