Sensors and analytical chemistry Sensitivity versus quality

Abstract

Instrumental analytical chemistry and chemical sensors, especially biosensors have made remarkable progress in the last decade. With respect to the analytical chemical performance characteristics the sensitivities could be increased drastically. However, the very important comparability of trace and ultra-trace analytical data produced in different laboratories has not been improved to the same degree. The analytical chemical performance characteristics of chemical and biochemical sensors must be judged with those facts in mind when they are validated using such traditional instrumental reference methods. Biosensors based on immune-chemical principles are more versatile in allowing nearly every analyte to be determined and are therefore chosen for this progress report. A recently developed calibration free optical single-use “immuno-chip” is described. This low-cost chip is based on an evanescence field fluorescence detection. The same technique and can also be used for a real-time recording of DNA hybridisation and dissociation events. Multi-analyte devices and DNA-arrays based on this technological platform were developed using a fast kinetic evaluation method. This offers certain advantages to methods detecting only the endpoint of a molecular association reaction especially concerning the detection of mismatches (SNP detection). Finally, a novel and relatively simple micro-electrochemical method based on a microelectrode array in combination with receptor-functionalized magnetic latex beads and an indicating redox system is described which bears in it an alternative to atomic force microscope binding forces measurements. Depending of the numer of individually addressable microelectrodes this method allows the simultaneous study of several hundred to thousands of molecule–molecule interactions within seconds. In addition, a single molecule detection and nearly unlimited multi-analyte, ultra-trace immuno-chemical sensing capabilities seem possible.