Bioluminescent whole cell optical fiber sensor to genotoxicants: system optimization

An Escherichia coil strain, genetically modified to emit a luminescent sign al in the presence of genotoxic agents, was alginate-immobilized onto an ex posed core of a fiber-optic. The performance of this whole-cell optical fib er sensor system was examined as a function of several parameters, includin g gel probe matrix volume, bacterial cell density, numerical aperture of th e fiber core and working temperature. An optimal response to a model genoto xicant, mitomycin C, was achieved with six alginate/bacterial adlayers on a 1 cm exposed fiber-optic core. Total alginate volume per tip was about 100 mul, containing a bacterial suspension of around 1.5-3.0 x 10(7) cells. Wh en the core diameter was etched down to 270 mum, photon detection efficienc y significantly increased, although to a lesser extent than that expected f rom theoretical calculations. Further reduction in core diameter led to a r educed performance. Activity at 37 degreesC was superior to that at 26 degr eesC. Under these optimized conditions, optrode response was mitomycin C do se-dependent for at least 6 h, with a lower detection threshold of 25 mug/l . (C) 2001 Elsevier Science B.V. All rights reserved.