Implantable optical biosensor for in vivo molecular imaging

We present the design and fabrication of an implantable fluorescence biosensor suitable for continuously monitored, freely-moving in vivo rodent studies. The GaAs-based semiconductor sensor incorporates an un-cooled photodetector with a 670nm vertical-cavity surface-emitting laser (VCSEL) optimized for sensing fluorescent Cy5.5 dye. For filtering unwanted spectra, a combination of physical and spectral blocking layers yields OD5 excitation rejection at the detector. The sensor detects near-IR fluorescent Cy5.5 molecules in vitro at 100nM concentration (in a 100μL volume) with linear response for concentrations up to 25μM. In a preliminary study in a living mouse, subcutaneously injected dye (1μM Cy5.5 in 50μL) was detected. This technology has the potential to enable new studies of living systems in applications that require long-term, continuous fluorescence sensing.