Biosensors commercially available

Much of the motivation for the study of XO electrochemistry is the development of amperometric biosensors. Commercially available bovine XO is invariably the enzyme of choice used in these applications. High levels of hypoxanthine are linked with asphyxia in newborns, SIDS and hypoxia in general. Coupled with other enzymes, such as purine nucleoside phos-phorylase, XO can be used to determine phosphate coneentrations in clinical, food and waste samples. Purine nueleoside phosphorylase catalyzes the phosphorylation of inosine liberating hypoxanthine and ribose-l-phosphate (Scheme 5.5). In the presence of XO, hypoxanthine is oxidized to xanthine and produces one equivalent of H2O2. Thus due to the stoichiometry of the reaction one equivalent of H2O2 is produced for every phosphate anion present. ... 

Few potentiometric biosensors are commercially available. As shown in Figures 11.16 and 11.17, however, available ion-selective and gas-sensing electrodes may be easily converted into biosensors. Several representative examples are described in Table 11.5, and additional examples can be found in several reviews listed in the suggested readings at the end of the chapter. 

This experiment describes the use of a commercially available amperometric biosensor for glucose that utilizes the enzyme glucose oxidase. The concentration of glucose in artificial... 

Commercially available kits for monitoring blood-glucose use an amperometric biosensor incorporating the enzyme glucose oxidase. This experiment describes how such monitors can be adapted to the quantitative analysis of glucose in beverages. 

Several biosensors are commercially available. One of the most useful is the glucose sensor. The standard sensor determines glucose concentration based on the glucose oxidase enzyme. The chemical reaction for oxidation of glucose is ... 

New developments in immobilization surfaces have lead to the use of SPR biosensors to monitor protein interactions with lipid surfaces and membrane-associated proteins. Commercially available (BIACORE) hydrophobic and lipophilic sensor surfaces have been designed to create stable membrane surfaces. It has been shown that the hydrophobic sensor surface can be used to form a lipid monolayer (Evans and MacKenzie, 1999). This monolayer surface can be used to monitor protein-lipid interactions. For example, a biosensor was used to examine binding of Src homology 2 domain to phosphoinositides within phospholipid bilayers (Surdo et al., 1999). In addition, a lipophilic sensor surface can be used to capture liposomes and form a lipid bilayer resembling a biological membrane. 

Main types of biomolecular recognition elements used in affinity biosensors based on spectroscopy of guided modes include antibodies, nucleic acids and biomimetic materials. Antibodies are used most frequently because of their high affinity, versatility, and commercial availability. 

SOD comprises a family of metalloproteins primarily classified into four groups copper, zinc-containing SOD (Cu, Zn-SOD), manganese-containing SOD (Mn-SOD), iron-containing SOD (Fe-SOD) and nickel-containing SOD (Ni-SOD). In the following studies, we will only focus on the uses of the former three kinds of SODs to construct SOD-based 02 biosensors since the last one, Ni-SOD, is not commercially available. 

More than 90% of commercially available enzyme-based biosensors and analytical kits contain oxidases as terminal enzymes responsible for generation of analytical signal. These enzymes catalyze oxidation of specific analyte with molecular oxygen producing hydrogen peroxide according to the reaction ... 

Biosensors fabricated on the Nafion and polyion-modified palladium strips are reported by C.-J. Yuan [193], They found that Nafion membrane is capable of eliminating the electrochemical interferences of oxidative species (ascorbic acid and uric acid) on the enzyme electrode. Furthermore, it can restricting the oxidized anionic interferent to adhere on its surface, thereby the fouling of the electrode was avoided. Notably, the stability of the proposed PVA-SbQ/GOD planar electrode is superior to the most commercially available membrane-covered electrodes which have a use life of about ten days only. Compared to the conventional three-dimensional electrodes the proposed planar electrode exhibits a similar... 

Table 1.1. Selected commercially available biosensor systems ... 

Most of the amperometric flow-through biosensors based on commercially available enzymes are employed to measure consumed or released oxygen by using a Clark electrode or a solid-state electrode to monitor the hydrogen peroxide formed or an enzymatically reduced acceptor. 

Fiber optic biosensor is one of the first commercially available optical biosensors, marketed by Research International (Monroe, WA) for the detection of foodborne as well as pathogens of biosecurity importance. The manual version of the instrument is called Analyte 2000 and the portable semiautomated version is called RAPTOR . ... 

Very few immunosensors are commercially available. The commercial immunosensors are either the detector or bioanalyzer types. The PZ 106 immunosensor from Universal Sensors Inc. (New Orleans, LA) has been used as a detector to measure antibody-antigen reaction. Ohmicron (Newtown, PA) developed a series of pesticide immuno-bioanalyzers that have been used in field tests. Pharmacia Biosensor USA (Piscataway, NJ) recently introduced BIAcore immunodetection system. A combination of a unique flow injection device and surface plasmon resonance (SPR) detection technique provides a real time analysis. A carboxylmethyldextran layer added to plasmon generating gold film is a hydrophobic, activatable, and flexible polymer that provides high antibody and low non-specific bindings. System demonstration at the Institute of Food Technologists (IFT) 1994 meeting in Atlanta drew attention of food scientists. It should easily be adapted for food protein characterization. 

In general, the commercially available biosensors in the food industry are based on a very similar technology, either an oxygen electrode or a hydrogen peroxide electrode in conjunction with an immobilised oxidase. They are available in several forms, such as autoanalysers, manual laboratory instruments and portable devices. Nevertheless,... 

NADH can be readily monitored electrochemically, and can be used as a simple and effective method to monitor metal ion concentrations. Such an approach has been recently utilised by Rodriguez et al. [149] for an SPCE-based biosensor for the amperometric detection of Hg2+, Cu2+, Cd2+, Zn+ and Pb2+. Devices used in this study were printed onto 250 pm thick polyester sheet. The working electrode (planar area 0.16 cm2) was fabricated from a commercially available carbon powder containing 5% rhodium plus promoters, which was made into a screen-printable paste by mixing 1 4 in 2.5% (w/v) hydroxyethyl cellulose in water. The reference electrode ink contained 15% silver chloride in silver paste. The counter electrode and basal tracks were fabricated... 

Fig. 23.7. Commercially available (AET, Ltd., UK) screen-printed NH4 amperometric biosensors. The diagram on the left shows the shape of the counter/ reference electrode and working electrode (area 0.28 cm2) the diagram on the right shows the complete biosensor with the mesh in position (After Ref [208]).

Tschmelak, J., M. Kumpf, N. Kappel, et al. 2006. Total internal reflectance fluorescence (TIRF) biosensor for environmental monitoring of testosterone with commercially available immunochemistry Antibody characterization, assay development and real sample measurements. Talanta 69 343-350. 

Integrated optical devices combine microelectronic production technology with the inherent advantages of optical sensing. Many of these developments are in an early state of research but a variety of optical biosensors can be realized in principle. Integrated optical device manufacturing is nowadays commercially available (IOT) and nearly all optical elements can be integrated and miniaturized on chip [24]. 

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