Finding the optimal source-detector separation of the spatially offset Raman spectroscopy free-space system for implantable biosensing device




Mekha, Sarah

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Prostate-specific antigen (PSA) levels in the interstitial fluid can be monitored to signal the recurrence of prostate cancer after treatment. Spatially offset Raman spectroscopy (SORS) offers a minimally invasive way to track interstitial fluid to receive crucial information comfortably and quickly. SORS aims to extract the Raman spectra of biomarkers near an implantable hydrogel underneath the skin, which contains surface-enhanced Raman spectroscopy (SERS) nanoparticles. By changing the source-detector separation (SDS) of the system, we can isolate different depths of information by tracking the intensities of the Raman spectra at each offset. Using a two-layer phantom sample to represent the skin and hydrogel – PDMS and PTFE, respectively – there is a larger offset needed to obtain a larger percent contribution from the bottom layer, which also increases as the thickness of PDMS increases. There is a linear relationship between the thickness of the skin covering the implantable hydrogel and the optimal offset needed to reach the targeted information while minimizing the weakening of the signal intensity.


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