Biosensor long-term

Over the last two decades, great enthusiasm has been observed in biosensor research. A key position for biosensors was predicted in analytical sciences allowing a sensitive, selective and, above all, a comparatively cheap determination of nearly all interesting substances. Therefore, Prognos AG, Basel, expected world-wide sales of about 2.3 Million DM in the year 2000, and many investors promoted R D on a large-scale. Nowadays, the enthusiastic discussion has mostly disappeared caused by disillusionment due to technical problems like biosensors long-term stability and economical aspects like the convincing benefits of biosensors. In most cases, a considerable need for R D was realised in order to fulfil customers requirements. 

Enzyme-based optical sensor applications will be further described in this book. They are still the most widespread optical biosensors but work is needed to overcome limitations such as shelf life, long term stability, in situ measurements, miniaturization, and the marketing of competitive devices. 

The fouling and microbial contamination of the surface during operation are main problems in the long-term use of enzyme biosensors. Wang et al. [121] reported for the first time a screen-printed electrode modified with GOD/HRP that was stable up... 

The application of biosensors for process monitoring has been dogged by problems with fouling, selectivity, degrading bioactivity and long-term stability. Recent developments in molecularly imprinted polymers (MIPs) show some promise as synthetic receptors and have been used for this purpose for assays and as HPLC stationary phases. Recent work has shown that MIPs show increased robustness, storage endurance and lower cost compared with biosensors, which... 

Carbon nanotubes are unique materials with specific properties [42]. There is a considerable application potential for using nanotubes in the biomedical field. However, when such materials are considered for application in biomedical implants, transport of medicines and vaccines or as biosensors, their biocompatibility needs to be established. Other carbon materials show remarkable long-term biocompatibility and biological action for use as medical devices. Preliminary data on biocompatibility of nanotubes and other novel nanostructured materials demonstrate that we have to pay attention to their possible adverse effects when then-biomedical applications are considered. 

F. Ricci, A. Amine, G. Palleschi and D. Moscone, Prussian Blue based screen printed biosensors with improved characteristics of long-term bfetime and pH stability, Biosens. Bioelectron., 18 (2003) 165-174. 

Yu B, Long N, Moussy Y, Moussy F. A long-term flexible minimally-invasive implantable glucose biosensor based on an epoxy-enhanced polyurethane membrane. Biosensors Bioelectronics 2006, 21, 2275-2282. 

Ballerstadt R, Polak A, Beuhler A, Frye J. In vitro long-term performance study of a near-infrared fluorescence affinity sensor for glucose monitoring. Biosensors Bioelectronics 2004, 19, 905-914. 

BOD was determined in wastewater using a microbial sensor based on an organic-inorganic hybrid material for immobilization of the biofilm. The biosensor response to the sample exhibited good reproducibility, long-term stability, and required only 10 min for each measurement.130 Near-infrared spectroscopy was used for the rapid determination of COD and BOD in wastewater.131... 

Long Term Performance of Sensors. The sensors showed excellent long term stability stored in buffer at 4 °C. Table 1 shows the long term performance of four typical biosensors. The usual current response to 6 mM glucose for a new biosensor is about 2 fiA. The precision of the absolute current response to 6 mM glucose remains within 15 % for up to four months. This level of precision is unusual for amperometric biosensors. Normally, variations in current are compensated by calibration. The sensitivity of the biosensors, as indicated by the slope of the response, is also stable. This stability is due to the film which maintains the ferrocene within the sensing layer. Biosensors with adsorbed mediator and immobilized enzyme but without film are not stable for any period of... 

Table 1. Long Term performance of glucose biosensors. Response at + 0.15 V vs SCE...

The construction of a biosensor, a biochip, or a bioreactor frequently requires the fixation of corresponding biomacromolecules, especially proteins, on an electrode without denaturation. Protein functions have been studied only in an aqueous medium. However, the aqueous medium is not the best matrix from in practical applications. The available temperature range of an aqueous system is not sufficiently wide, and it is scarcely possible to maintain long-term stability of the proteins in an aqueous medium. It is therefore important to find a nonaqueous medium in... 

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