Using a porous silicon photonic crystal for bacterial cell-based biosensing

This work demonstrates a method for non-invasively monitoring the growth and 06 virus infection of Pseudomonas syringae bacteria using a 1-D porous silicon photonic crystal and a white-light source coupled to a CCD spectrometer. Bacteria growth on porous Si leads to increased scattering efficiency that can be measured as a change in intensity of light reflected from a 1-D porous Si photonic crystal. A linear relationship between bacteria concentration and intensity of light at the photonic resonance is observed, and detection limits are similar to those obtained from optical density measurements. Upon infection with virus, decreases in scattered light intensity are observed at times that correlate with cell lysis caused by viral replication and subsequent bursting of bacteria cells. It is shown that measurements can be performed in real-time and in an incubator where cells remain in their ideal environment throughout the experiment. This method is well-suited for cell-based biosensing, because bacteria cells can be monitored remotely without the need for sampling cells for plating or optical density measurements. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.