Chemical sensors and biosensors for fluoride: current status and developing technologies

Portable sensors for bioanalytes are becoming of increasing interest, because their development will permit analyses of biological samples at the point of sampling, i.e., at the time when an individual is being examined by a health professional. In this paper, the design requirements for a fluoride sensor are outlined. Currently, commercially available fluoride sensors, ion-selective electrodes, do provide the capability to measure fluoride content in samples directly. However, the sensitivity of these devices is lower than the normal content of fluoride in plasma, and thus, samples must be concentrated before measurement. Recent progress in improving the sensitivity of chemical sensors for fluoride shows sensitivities up to 0.1 mumol/L, which is within the range of interest. In addition, the use of biological systems for developing sensors (biosensors) is expanding rapidly, because of the potential of achieving high selectivity and sensitivity through the use of the amplification power of enzymes. However, relatively few enzyme systems have been discovered that are affected by fluoride--thus the need for expanded research to find appropriate enzymes for this purpose. The characteristics of some enzymes, such as adenylate cyclase, that could be used in the development of a fluoride biosensor are discussed.