Label-free optical detection of anthrax-causing spores

An optical biosensor integrated with short peptide ligands for detection of Bacillus anthracis spores is described. A short peptide that can bind specifically to B. anthracis spores was synthesized and used as the ligand. With this approach, a minimum of 34 spores of B. anthracis, specifically captured on the sensor, were detected by measuring the laser light transmission intensity and verified by laser scanning confocal fluorescence microscopy. The differential nature of measurement reduces the incidence of false positives. The detection process, from capturing B. anthracis spores on the sensor surface to laser transmission intensity measurements, required a short time of 35 min. This biosensor, with its simple instrumentation, ease of use, and short detection time, can enable the development of a portable device for rapid, label-free, specific, and uantitative detection of anthrax-causing spores