  Chiral molecule sensing is currently performed using chromatography,
electrophoresis, enzymatic-assays, mass spectrometry, and chiroptical sensing
techniques. Currently polarimetry is the only method having in-vivo sensing
capabilities, while other techniques analyze chiral molecules in body fluids.
Polarimetry demonstrated in-vivo performance upto depths of 1 mm while using
UV-Visbile light, beyond which light scattering tends to be dominant. We
hypothesize that photoacoustic sensing while operating at the Near-Infrared
(NIR)-II window can allow for deep-tissue sensing, due to reduced
scattering/autofluorescence effects. Herein, a Photoacoustic based Polarization
Enhanced Optical Rotation Sensing (PAPEORS) system was developed for the first
time to estimate optical rotation parameter using the recorded PA signals at
larger depths. This optical rotation was then used to correlate with the chiral
molecular concentration at depths of about 3.5 mm. Experimental evaluations
were performed with aqueous glucose solution, naproxen drug, and serum-based
glucose samples. PAPEORS has achieved a detection limit of 80 mg/dL using
circular incidence polarization with serum-based glucose samples. Further
ex-vivo experiments were performed to demonstrate the ability of PAPEORS for
deep-tissue sensing, which can be extended for in-vivo chiral molecular
sensing. PAPEORS uses single wavelength for sensing chiral biomolecules, hence
can be miniaturized, allowing for many point-of-care applications.
