Fiber Optic Sensors: Recent Developments

Detection of botulinum toxin using an evanescent wave immunosensor

Using fluorescein isothiocyanate (FITC)-streptavidin, quartz fibre-immobilized antibody (FiAb) and the evanescent wave component of a light beam, detection of Botulinum Toxin-B (BoTX) is described. Exposure of 3-aminopropyltriethoxysilane/glutaraldehyde (APTS/GA) treated quartz fibres to increasing amounts of anti-BoTX Ab indicated toxin binding to increase in a linear fashion up to approximately 125 ng added Ab. Quantitation of bound BoTX and FiAb by Dot-Blot analysis using avidin-Horseradish peroxidase (HRP) conjugation indicated the presence of 0.27 and 0.67 pmoles, respectively. Inclusion of nonbiotinylated BoTX in sampling mixtures reduced fluorescence in a dose-dependent manner over a narrow concentration range (0-300 ng). Exposure of FiAb to a variety of venoms resulted in no reduction of BoTX binding suggesting detection of BoTX via immobilized anti-BoTX Ab to be very specific.

Software FIACRE: bioprocess monitoring on the basis of flow injection analysis using simultaneously a urea optode and a glucose luminescence sensor

Various computer programs for large-scale bioprocess control and optimization have been developed as well as software for simple laboratory routine analysis. In comparison, software can hardly be found that works on laboratory scale and provides the control of complex flow injection analysis (FIA) systems, multisubstrate determination, data evaluation as well as minimal process control abilities. The sensors applied can be of different type (luminometric or other optical as well as electrochemical biosensors). The development of such a software may be very helpful for the transfer of FIA/biosensor systems from the state of development to industrial processes. Hence, each analysing system--even a well established biosensor--has to be individually adapted to the process, a task which is best done under laboratory conditions. Such a flexible, computer-controlled FIA system for research level based on the software FIACRE is presented. Five FIA/(bio)sensor system can be controlled simultaneously. Additionally, common temperature and pH recordings are possible. Determinations of substrate concentrations are performed by means of calibration curves which can be recorded at different times. This allows supervising the activities of the sensors during a cell cultivation and controlling the bioprocess, e.g. by adding substrate to a cell culture. The automated monitoring of the degradation of glucose and urea by two different optical sensing principles during a cell cultivation under the control of one microcomputer is presented for the first time. For this purpose, already well examined biosensors (a urease optode and a luminometric glucose sensor) were employed and their properties discussed under the aspect of working in real cultivation media. It will also be shown that substrates being of interest for bioprocess control can be detected by slight modifications of known reactions. For example, substrates of NADH-dependent enzymatic reactions can be detected by the luminol chemiluminescence system, and optodes can be employed for pH, penicillin and glucose determination.

Biosensors for process control

Biosensors have been extensively studied during the last 20 years, and a myriad of laboratory biosensors have been developed. Improvements are required in biosensor design and performance before they become widely accepted in industrial process monitoring. However, as the biotechnology industry expands, biosensors may become more acceptable because, despite their limitations, they are the only devices capable of delivering the information required.