Hyper-Raman spectroscopy of biomolecules.

The hyper-Raman scattering (HRS) spectra of biologically significant molecules (D-glucose, L-alanine, L-arabinose, L-tartaric acid) in aqueous solutions are reported. The HRS spectra were measured using a picosecond laser at 532 nm operating at a MHz repetition rate. High signal to noise spectra were collected with a commercial spectrometer and CCD without resonant, nanoparticle, or surface enhancement. The HRS peak frequencies, relative intensities, band assignments, and depolarization ratios are examined. By comparing HRS to Raman scattering (RS) and infrared absorption spectra we verify that the IR-active vibrational modes of the target molecules are observed in HRS spectra but come with substantially different peak intensities. The HRS of the biomolecules as well as water, dimethyl sulfoxide, methanol, and ethanol were deposited into a data repository to support the development of theoretical descriptions of HRS for these molecules. Depositing the spectra in a repository also supports future dual detection RS, HRS microscopes which permit simultaneous high-spatial-resolution vibrational spectroscopy of IR-active and Raman-active vibrational modes.

Porcine vocal fold elasticity evaluation using Brillouin spectroscopy.

Significance: The vocal folds are critically important structures within the larynx which serve the essential functions of supporting the airway, preventing aspiration, and phonation. The vocal fold mucosa has a unique multilayered architecture whose layers have discrete viscoelastic properties facilitating sound production. Perturbations in these properties lead to voice loss. Currently, vocal fold pliability is inferred clinically using laryngeal videostroboscopy and no tools are available for in vivo objective assessment. Aim: The main objective of the present study is to evaluate viability of Brillouin microspectroscopy for differentiating vocal folds' mechanical properties against surrounding tissues. Approach: We used Brillouin microspectroscopy as an emerging optical imaging modality capable of providing information about local viscoelastic properties of tissues in noninvasive and remote manner. Results: Brillouin measurements of the porcine larynx vocal folds were performed. Elasticity-driven Brillouin spectral shifts were recorded and analyzed. Elastic properties, as assessed by Brillouin spectroscopy, strongly correlate with those acquired using classical elasticity measurements. Conclusions: These results demonstrate the feasibility of Brillouin spectroscopy for vocal fold imaging. With more extensive research, this technique may provide noninvasive objective assessment of vocal fold mucosal pliability toward objective diagnoses and more targeted treatments.