Fluorescence-based implantable biosensors: Monte Carlo modeling for optical probe design

Implantable fluorescent sensors may be an attractive solution to the monitoring of many parameters of biomedical interest. A Monte Carlo simulation of photon propagation through human skin and interaction with a subcutaneous fluorescent sensing layer is presented. Results pre analyzed with respect to output light intercity as a function of distance from source, input-to-output characteristics, and single-photon versus dual-photon excitation. The results indicate that radial fluorescence emission profile is broad compared to the diffusely reflected input light. Response intensity has an approximately logarithmic relationship with sensor thickness. Estimated values for tissue autofluorescence quantum yield lead to an approximately inverse relationship between sensor signal-to-noise ratio. One-photon excitation exhibits higher per-photon yield than two-photon excitation