Gas phase biosensors

Abstract

The last two decades have shown an enormous interest and research efforts on the use of biological activity in analysis, mainly for direct or on line monitoring of chemical compounds. The core work has emphasised on the detection of analytes in aqueous solutions. However, the rapid progress of enzymatic applications on low water environments in recent years is considered to be of high potential for the development of biosensors applicable to compounds present in the gas phase. This review describes the principles that underline the operation of gas phase biosensors and the potential areas of impact in the forthcoming years with examples that illustrate its applicability. A distinct advantage is identified for the direct interaction of gaseous compounds with biological targets that originate a detectable and measurable signal applicable at the field or site of interest, as opposed to preparative steps like the solubilization of volatiles in water, sampling and transportation to the laboratory for further analysis. This is illustrated by enzyme systems based on dehydrated alcohol oxidase for the determination of ethanol or formaldehyde vapors. Current knowledge on the phenomena that control the performance of gas phase enzymatic conversions is also discussed.

The two approaches that have predominated for gas phase biosensors are covered, one based on a biochemical reaction mediated by enzymes or whole cells, and other based on the formation of complexes of biological molecules via adsorption, an alternative in which the use of antibodies has been specially fruitful when coated on piezolectric crystals. The later is unique for environmental applications as in the case of pesticides. Other areas of impact include food related applications and the control of bio-processes.