Polarization-resolved hyperspectral stimulated Raman scattering microscopy for label-free biomolecular imaging of the tooth

Abstract

We report the development and implementation of a rapid polarization-resolved hyperspectral stimulated Raman scattering (SRS) microscopy technique for label-free biomolecular imaging of the tooth. The hyperspectral SRS imaging technique developed covers both fingerprint (800–1800 cm−1) and high-wavenumber (2800–3600 cm−1) regions for tooth Raman imaging without fluorescence background interference with an imaging speed of <0.3 s per frame of 512 × 512 pixels (∼1 μs per pixel), that is, >106 faster than confocal Raman imaging. Significant differences of hyperspectral SRS spectra among different tooth locations (e.g., dentin, enamel, and dentin-enamel junction) are observed, revealing the biochemical distribution differences across the tooth. Further polarization-resolved SRS imaging shows different polarization dependences related to the molecular orientation differences of various tooth locations. This work demonstrates the potential of polarization-resolved hyperspectral SRS imaging technique developed in rapidly characterizing biochemical structures and compositions as well as biomolecule organizations/orientations of the tooth without labeling.

Hyper‐spectral Raman imaging correlating chemical substitution and crystallinity in biogenic hydroxyapatite: Dentin and enamel in normal and hypoplastic human teeth

“…Micro‐Raman imaging has been widely employed to identify the dentin–enamel junction (DEJ) separating the hard outer enamel from the soft inner dentin region . Of particular interest has been the width of the DEJ, spatial variations within the dentin and enamel regions, and modifications associated to different tooth diseases . In particular, to gain insight into structural changes across the DEJ, spatial variations in lineshape of the phosphate Raman mode have been analyzed, yet without the relationship of the Raman response to chemical and structural parameters of the apatite.…”

Characterizing biochemical and morphological variations of clinically relevant anatomical locations of oral tissue in vivo with hybrid Raman spectroscopy and optical coherence tomography technique

“…Figure A shows the mean in vivo FP/HW Raman spectra ± 1SD measured from the oral cavity under the OCT imaging guidance. Prominent FP Raman peaks were identified in the oral cavity as follows: 853 cm −1 ( v (C─C) proteins), 1004 cm −1 ( ν s (C─C) ring breathing of phenylalanine), 960 cm −1 ( ν s (P─O) of hydroxyapatite), 1078 cm −1 ( ν (C─C) of lipids), 1265 cm −1 (amide III v (C─N) and δ(N─H) of proteins), 1302 cm −1 (CH 2 twisting and wagging of lipids), 1445 cm −1 ( δ (CH 2 ) deformation of proteins and lipids) and 1655 cm −1 (amide I v (C═O) of proteins) in the FP range . In the HW range, intense Raman peaks are also observed: that is, 2850 and 2885 cm −1 (symmetric and asymmetric CH 2 stretching of lipids), 2940 cm −1 (CH 3 stretching of proteins) and the broad Raman band of water (OH stretching vibrations peaking at ~3250 and ~3400 cm −1 ) that are related to the local conformation and interactions of OH‐bonds in the intracellular and extracellular space of oral tissue .…”

Multimodal nonlinear microscope based on a compact fiber-format laser source

“…The complexity of the excitation laser is one reason why, after its early demonstration in 1982 [23], the development of CRS microscopy has stopped for nearly two decades. Following its revival, initial CRS implementations were based on two electronically synchronized picosecond Ti:sapphire oscillators [24][25][26], while the current "gold standard" is represented by an optical parametric oscillator synchronously pumped by a picosecond Nd:YVO4 oscillator [27][28][29]. Such systems are complex, expensive, and they all critically require a synchronization between two independent laser sources, which must be maintained over time.…”