Immunoassay: recent developments and future directions

Abstract

All analytical techniques employed in the biological sciences rely on recognition of the shape and structure of molecules of the substance of interest (the analyte). Such molecular recognition and sensing usually relies on the use other molecules possessing a complementary structure, implying a specific lock and key relationship between the two. Antibodies comprise a class of recognition molecules evolved by nature for the purpose of bodily defence, and are clearly of particular utility in this context. However techniques of increasing sophistication (including the techniques of molecular biology) are currently being developed which enable the artificial construction of antibody-like molecules possessing improved molecular recognition properties which can be harnessed for microanalytical purposes. Oligonucleotide probes likewise exhibit the property of binding to complementary nucleotide sequences, and the techniques of, for example, in situ hybridisation therefore share many features with immunoassay techniques. Microanalytical techniques relying on binding reactions between substances possessing complementary lock and key molecular structures are unlikely to be superseded within the foreseeable future, only the labels used to monitor such reactions, and the means of production of "recognition molecules", being subject to further development. Such techniques already enter into all areas of life, including medicine, agriculture, etc, and are likely to increase further in importance with increasing concern regarding chemically complex contaminants in food, the environment, etc. Developments in this field are clearly directed to slightly differing objectives as indicated in this presentation. These include methodological simplification (making the techniques cheaper and more widely available), improvements in sensitivity (to enable the detection and measurement of substances beyond the reach of current methods) and the construction of transducer-based sensor methods (permitting, inter alia, the monitoring of changing analyte concentrations). However the combination of the "ultrasensitivity" of current single analyte assay methods with the ability simultaneously to determine multiple analytes in the same sample represents, in my view, the next major methodological challenge in this field, and--if successfully addressed--will constitute a quantum advance on present analytical methods. Indeed the development of miniaturised multianalyte binding assay techniques may ultimately comes to be seen as analagous to, for example, the introduction of the word processor, and other similar major technological advances of the past decade.