A fractal analysis of pathogen detection by biosensors.

A fractal analysis is presented for the detection of pathogens such as Franscisela tularensis, Yersinia pestis (the bacterium that causes plague), Bacillus anthracis, Venezuelan equine encephalitis (VEE) virus, Vavcinia virus, and Escherichia coli using a cellular analysis and notification of antigens risks and yields (CANARY) biosensor [T.H. Rider, M.S. Petrovic, F.E. Nargi, J.D Harper, E.D. Schwoebel, R.H. Mathews, D.J. Blanchard, L.T Bortolin, A.M. Young, J. Chen, M.A. Hollis, A cell-based sensor for rapid identification of pathogens, Science 301 (2003, 11 July) 213-215, T.H. Rider, M.S. Petrovic, F.E. Nargi, J.D. Harper, E.D. Schwoebel, R.H. Mathews, D.J. Blanchard, L.T. Bortolin, A.M. Young, J. Chen, M.A. Hollis, A cell-based sensor for rapid identification of pathogens, Science 301 (2003, 11 July) 213-215. Science Online, www.sciencemag.org/cgi/content/full/031/5630/213/DC1]. In general, the binding and dissociation rate coefficients may be adequately described by either a single- or a dual-fractal analysis. An attempt is made to relate the binding rate coefficient to the degree of heterogeneity (fractal dimension value) present on the biosensor surface. Binding and dissociation rate coefficient values obtained are presented. Due to the dilute nature of the analyte(s) present, in some cases, a triple-fractal analysis is required to adequately describe the binding kinetics. It should be noted, and this is not entirely unexpected, that there is a lot of variation in the original experimental data when dilute concentrations of the analyte were analyzed by the CANARY biosensor [T.H. Rider, M.S. Petrovic, F.E. Nargi, J.D Harper, E.D. Schwoebel, R.H. Mathews, D.J. Blanchard, L.T Bortolin, A.M. Young, J. Chen, M.A. Hollis, A cell-based sensor for rapid identification of pathogens, Science 301 (2003, 11 July) 213-215, Science Online, www.sciencemag.org/cgi/content/full/031/5630/213/DC1]. The data analyzed in this manuscript appears smoother since only discrete points at different time intervals were analyzed. The kinetics aspects along with the affinity values presented are of interest and should along with the rate coefficients presented for the binding and the dissociation phase be of significant interest in help designing better biosensors for an application area that is bound to gain increasing importance in the future.