Optical modeling of bioluminescence in whole cell biosensors

Bioluminescence-based whole cell biosensors are devices that can be very useful for environmental monitoring applications. The advantages of these devices are that they can be produced as a single-chip, low-power, rugged, inexpensive component, and can be deployed in a variety of non-laboratory settings. However, such biosensors encounter inherent problems in overall system light collection efficiency. The light emitted from the bioluminescent microbial cells is isotropic and passes through various media before it reaches the photon detectors. We studied the bioluminescence distribution and propagation in microbial whole cell biochips. Optical emission and detection were modeled and simulated using an optical ray tracing method. Light emission, transfer and detection were simulated and optimized with respect to two fundamental system parameters: system geometry and bacterial concentration. Optimization elucidated some of the optical aspects of the biochip, e.g. detector radius values between 300 and 750 microm, and bacterial fixation radius values between 800 and 1200 microm. Understanding theses aspects may establish a basis for future optimization of similar chips.