Sensors for detection of calcium associated with bacterial endospore suspensions

We describe a method of detecting bacterial endospores via quantitation of calcium uniquely associated with spore suspensions. The sensor is created b y combining a fluorescent calcium-sensitive indicator, calcein, in a viscou s membrane on planar, silica glass coupons. The sensor coupon is affixed to the distal end of an optical fiber, which provides excitation light and co llects the fluorescence emission. Aqueous micro-droplets of bacterial spore s are added to the sensor and the resulting increase in fluorescence intens ity is monitored. This assay effectively exploits the high concentration of calcium ion found in the spore core and expressed on the surface, and fluo rescence spectroscopy, as an indirect method to detect and quantify spore c oncentration. This sensor technology is applicable to near real-time detect ion of calcium in bacterial spore suspensions without interference from lig ht scattering or other ambient biological materials such as bacteria, polle n, viruses, and fungal spores. (C) 2001 Elsevier Science B.V. All rights re served.