Light Scattering Spectroscopy of Tissue Phantoms for Applications in Biomedical Sciences

Inelastic light scattering reveals information on an analyte through interactions of atoms or molecules with photons. Micro-mechanical properties of samples are probed with Brillouin microscopy, through interactions of light with acoustic phonons (sound waves), and their chemical information is revealed with Raman microscopy, through interactions of light with molecular vibrations. Both techniques are non-contact, non-destructive, and label-free, which makes them valuable tools in diagnostics. Brillouin microscopy requires knowledge of refractive index and density on the micro-scale to unearth the longitudinal modulus, a material’s response to small, high-frequency (GHz) deformations. This is often difficult with biological samples displaying large amounts of heterogeneity. Interpretation of the origin of the Brillouin signal still sparks debate due to the dependence on sample properties and the different spatio-temporal scales when compared with traditional mechanical testing. In this work, oil-in-gelatin emulsions with a tunable protein and lipid content were investigated with Brillouin microscopy to reveal the extent to which changing sample properties affect the measured Brillouin spectrum and the longitudinal modulus, to obtain a deeper understanding of the origin of the spectrum in this biological context. Raman spectroscopy was used as a correlative technique to predict the refractive index of the phantoms based on a predetermined calibration curve. The results showed that when increasing the lipid content of phantoms, the change in Brillouin frequency shift is not proportional to the change in longitudinal mod- ulus, showing that knowledge of refractive index and density is necessary in this environment. A partial least squares regression algorithm was able to predict the lipid content to ±6.87%, enabling an accurate refractive index prediction. This will enable quantitative Brillouin microscopy measurements in more diverse environments, opening the door for micro-mechanical measurements of many different tissue types.<p></p>

Author dc:creator

• Steve Hill (21042638)

• Light Scattering Spectroscopy

Statement dc:rights

• All rights reserved
• Open Access after 2027-12-01

Identifier

10779/exe.32605263.v1

OAI identifier oai:identifier

oai:figshare.com:article/32605263