Composite alcohol biosensors based on solid binding matrix

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.

Determination of serum alcohol using a disposable biosensor

This paper presents a disposable biosensor to detect serum alcohol concentration. The proposed biosensor is fabricated using the cross-linking method to immobilize Alcohol Dehydrogenase (ADH) and Nicotinamide Adenine Dinucleotide (NAD(+)) on the screen-printed electrode modified with Meldola's Blue (MB) absorbed on Nafion. It is based on the electrocatalytic properties of MB as an electron transfer mediator, which can catalyze the oxidation of NADH to NAD(+) at a low oxidizing potential, thus avoiding interferences due to the presence of oxidizable substances in the real serum samples. The biosensor response for alcohol is investigated in terms of pH, buffer solution, temperature and some interferents. It presents the good specificity, reproducibility, stability, accuracy and provides a fast response. The biosensor has been satisfactorily used for the measurement of serum alcohol.

Cofactor regeneration for sustainable enzymatic biosynthesis

Oxidoreductases are attractive catalysts for biosynthesis of chiral compounds and polymers, construction of biosensors, and degradation of environmental pollutants. Their practical applications, however, can be quite challenging since they often require cofactors such as nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These cofactors are generally expensive. Efficient regeneration of cofactors is therefore critical to the economic viability of industrial-scale biotransformations using oxidoreductases. The chemistry of cofactor regeneration is well known nowadays. The challenge is mostly regarding how to achieve the regeneration with immobilized enzyme systems which are preferred for industrial processes to facilitate the recovery and continuous use of the catalysts. This has become a great hurdle for the industrialization of many promising enzymatic processes, and as a result, most of the biotransformations involving cofactors have been traditionally performed with living cells in industry. Accompanying the rapidly growing interest in industrial biotechnology, immobilized enzyme biocatalyst systems with cofactor regeneration have been the focus for many studies reported since the late 1990s. The current paper reviews the methods of cofactor retention for development of sustainable and regenerative biocatalysts as revealed in these recent studies, with the intent to complement other reviewing articles that are mostly regeneration chemistry-oriented. We classify in this paper the methods of sustainable cofactor regeneration into two categories, namely membrane entrapment and solid-attachment of cofactors.

A sputtered thin film of nanostructured Ni/Pt/Ti on Al2O3 substrate for ethanol sensing

A novel thin film ethanol sensor using sputtered Ni/Pt/Ti on an Al2O3 substrate as the working electrode in an alkaline solution was developed. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the nanostructure of nickel films. Sputtering deposition conditions for maximum catalytic efficiency, electrode selectivity, and reproducibility were discussed. The results showed that ethanol oxidation was more efficient on the sputtered Ni/Pt/Ti on an Al2O3 substrate electrode than that on the conventional nickel electrode. The optimal operating conditions to generate the sputtered Ni/Pt/Ti on the Al2O3 substrate electrode were: 45 min of Ni sputtering deposition time, and 50 W of Ni sputtering power. The results also indicated that the response time of the prepared ethanol sensor is 27 s and the best sensitivity is 3.08 microA microM(-1) cm(-2).

Development of a disposable ethanol biosensor based on a chemically modified screen-printed electrode coated with alcohol oxidase for the analysis of beer

A disposable amperometric biosensor for the measurement of ethanol has been developed. It comprises a screen-printed carbon electrode doped with 5% cobalt phthalocyanine (CoPC-SPCE), and coated with alcohol oxidase; a permselective membrane on the surface acts as a barrier to interferents. The measurement of ethanol is based on the signal produced by H2O2, the product of the enzymatic reaction. Optimisation studies were performed using amperometry in stirred solution and the magnitude of the signal was found to be dependent on pH, enzyme loading, type of membrane and applied potential. The same technique was used to evaluate the biosensor for the determination of ethanol in samples. The results obtained compared well with the manufacturers specifications. In order to test the possibility of using the devices in the field, chronoamperometry was also used to determine ethanol in the same beer samples. The precision and recovery data again indicated that the biosensor should give reliable results under the conditions described.

Chemoselective biosensors

New opportunities for biosensors are now appearing in clinical and genetic diagnostics, genomics, environmental protection, food processing and safety, drug discovery and bioprocess monitoring. Concerns about the cost, stability and selectivity of previous sensor technologies are being addressed by developing new recognition systems and their integration into transducers, micro- and nanofabricated devices, array technologies and novel magnetic, acoustic and optical transduction systems.

Amperometric biosensors based on solid binding matrices applied in food quality monitoring

Solid binding matrix (SBM) based composite transducers have been used for development of series of multibiosensor systems applicable in various fields. Here we present two hybrid three-channel multibiosensors for simultaneous amperometric operation in food quality control, i.e. glucose/fructose/ethanol multibiosensor, based on glucose oxidase/fructose dehydrogenase/alcohol dehydrogenase surface-modified enzyme electrodes and L-lactate/L-malate/sulfite multibiosensor, based on L-lactate dehydrogenase/L-malate dehydrogenase/sulfite oxidase surface-modified enzyme electrodes. Different parameters have been studied in order to optimize the response of the multibiosensor systems. The multibiosensor showed a good sensitivity, linear range and storage stability. The multibiosensors were used for the determination of glucose, fructose, ethanol, L-lactate, L-malate and sulfite in samples of wine, resulting in a good agreement with data certified by the supplier. Comparison of various designs, surface-modified, bulk-modified and thick-cover, of SBM based biosensors is studied on the example of fructose biosensor.