Brillouin and Raman scattering spectroscopy are established techniques for the nondestructive contactless and label-free readout of mechanical, chemical, and structural properties of condensed ...matter. Brillouin-Raman investigations currently require separate measurements and a site-matched approach to obtain complementary information from a sample. Here, we demonstrate a new concept of fully scanning multimodal microspectroscopy for simultaneous detection of Brillouin and Raman light scattering in an exceptionally wide spectral range, from fractions of GHz to hundreds of THz. It yields an unprecedented 150-dB contrast, which is especially important for the analysis of opaque or turbid media such as biomedical samples, and spatial resolution on a subcellular scale. We report the first applications of this new multimodal method to a range of systems, from a single cell to the fast reaction kinetics of a curing process, and the mechanochemical mapping of highly scattering biological samples.
Brillouin-Raman microspectroscopy is presented as an innovative label-free all-optical investigation approachable to characterize the chemical composition and the mechanical properties of human ...tissues at micrometric resolution. Brillouin maps unveil mechanical heterogeneities in a human femoral diaphysis, showing a ubiquitous co-existence of hard and soft components, even in the most compact sections. The novel correlative analysis of Brillouin and Raman maps shows that the relative intensity of Brillouin peaks is a good proxy for the fraction of mineralized fibers and that the stiffness (longitudinal elastic modulus) of the hard component is linearly dependent on the hydroxyapatite concentration. For the soft component, a gradient of composition is found, ranging from an abundance of proteins in the more compact, external, bone to abundance of lipids, carotenoids, and heme groups approaching the trabecular, inner, part of the diaphysis. This work unveils the strong potential of correlative mechano-chemical characterization of human tissues at a micrometric resolution for both fundamental and translational research.
Abstract Brillouin light scattering (BLS), a non-destructive and non-contact technique, offers a powerful tool for probing the micromechanical properties of biological tissues. However, the inherent ...heterogeneity of biological tissues can pose significant challenges in interpreting BLS spectra. In this study, we introduce a novel method that harnesses the intensity information within a single BLS spectrum to directly estimate the Voigt average of the longitudinal modulus. Additionally, we use a method to determine the ratio of the squared Pockels coefficients for photoelastically heterogeneous samples, based on global analysis of a 2D BLS map. This method is shown to effectively determine the photoelastic ratio of soft and hard components of human bone tissues, enabling the calculation of the average elastic moduli. Furthermore, it has the remarkable ability to generate maps of the filling factor of the scattering volume, shedding valuable light on the intricate structure and topography of rough surfaces under BLS mapping.
This multicenter study evaluated three candidate microRNAs (miRNAs) (miR-21, miR-155 and miR-101) as potential biomarkers in intraductal papillary mucinous neoplasms (IPMNs) of the pancreas.
miRNA ...expression was quantified by quantitative RT-PCR in 86 laser-microdissected specimens, including 65 invasive IPMNs, 16 non-invasive IPMNs and 5 normal pancreatic ductal tissues. Univariate and multivariate analyses compared miRNAs and clinical parameters with overall (OS) and disease-free survival (DFS).
miR-21 and miR-155 were up-regulated in invasive IPMNs compared with non-invasive IPMNs, as well as in non-invasive IPMNs compared with normal tissues. Conversely, miR-101 levels were significantly higher in non-invasive IPMNs and normal tissues compared with invasive IPMNs. High levels of miR-21 were associated with worse OS hazard ratio (HR) = 2.47, 95% confidence interval (CI) = 1.37–5.65, P = 0.0047. Patients with high-miR-21 expression also had a shorter median DFS (10.9 versus 29.9 months, P = 0.01). Multivariate analysis confirmed miR-21 as independently prognostic for mortality and disease progression (death risk: HR = 3.3, 95% CI = 1.5–7.0, P = 0.02; progression risk: HR = 2.3, 95% CI = 1.2–4.8, P = 0.02), as well as positive lymph-node status (death risk: HR = 2.6, 95% CI = 1.1–6.3, P = 0.03; progression risk: HR = 2.2, 95% CI = 1.0–4.8, P = 0.04).
miR-21, miR-155 and miR-101 showed significant differences in invasive versus non-invasive IPMNs. miR-21 emerged as an independent prognostic biomarker in invasive IPMNs and should be validated in prospective studies.
Bone has a sophisticated architecture characterized by a hierarchical organization, starting at the sub-micrometre level. Thus, the analysis of the mechanical and structural properties of bone at ...this scale is essential to understand the relationship between its physiology, physical properties and chemical composition. Here, we unveil the potential of Brillouin-Raman microspectroscopy (BRaMS), an emerging correlative optical approach that can simultaneously assess bone mechanics and chemistry with micrometric resolution. Correlative hyperspectral imaging, performed on a human diaphyseal ring, reveals a complex microarchitecture that is reflected in extremely rich and informative spectra. An innovative method for mechanical properties analysis is proposed, mapping the intermixing of soft and hard tissue areas and revealing the coexistence of regions involved in remodelling processes, nutrient transportation and structural support. The mineralized regions appear elastically inhomogeneous, resembling the pattern of the osteons' lamellae, while Raman and energy-dispersive X-ray images through scanning electron microscopy show an overall uniform distribution of the mineral content, suggesting that other structural factors are responsible for lamellar micromechanical heterogeneity. These results, besides giving an important insight into cortical bone tissue properties, highlight the potential of BRaMS to access the origin of anisotropic mechanical properties, which are almost ubiquitous in other biological tissues.
Mechanical mapping with chemical specificity of biological samples is now made possible by joint micro-Brillouin and micro-Raman measurements. In this work, thanks to the unprecedented contrast of a ...new tandem Fabry-Perot interferometer, we demonstrate simultaneous detection of Brillouin and Raman spectra from different Candida biofilms. Our proof-of-concept study reveals the potential of this label-free joint micro-spectroscopy technique in challenging microbiological issues. In particular, heterogeneous chemo-mechanical maps of Candida biofilms are obtained, without the need for staining or touching the sample. The correlative Raman and Brillouin investigation evidences the role of both extracellular polymeric substances and of hydration water in inducing a marked local softening of the biofilm.
Display omitted
•We present the potential of a new Brillouin-Raman spectroscopic setup to study the chemico-mechanical properties of biofilms•Variations of viscoelasticity between cells and species can be studied and related to molecular specificity•Local softening is found, corresponding to residual hydration water and to the presence of extracellular polymeric substance
Specifically designed samples have been analyzed to test the ability of Brillouin spectroscopy to provide reliable mechanical characterization of micro and nano-objects. The selected samples are ...polymeric films, whose transversal sizes from hundreds of nano- to some micro-meters cover the entire range of length-scales relevant in Brillouin scattering process. The experimental data highlight how, the size of the extended collective oscillation (acoustic phonons, in brief) is the lowest spatial resolution reachable in Brillouin mechanical characterization. Conversely, in the limit condition of phonon confinement, the technique provides the mechanical properties of nano-objects whose characteristic size is comparable with the phonon wavelength (⁓300 nm). Investigating acoustically heterogeneous materials, both size of heterogeneity and acoustic mismatch between adjacent regions are shown to be relevant in shaping the Brillouin response. In particular, a transition from a confined to a non-confined condition is obtained modulating the acoustic mismatch between the micro-objects and their local environment. The provided results and the derived analytic models for the data analysis will guide the interpretation of Brillouin spectra acquired in complex nano-structured samples such as cells, tissues or biomimetic materials. Our analysis can therefore generate new insights to tackle fundamental problems in mechanobiology or to characterize new bioengineered materials.
Display omitted
•Thin films of different traversals size are investigated as biomaterials models.•Brillouin spectroscopy measures the mechanical properties of micro and nano-objects.•Phonon confinement increases the spatial resolution of Brillouin spectroscopy.•Size and acoustic mismatch of heterogeneities alters Brillouin elastography.
Extended frequency range depolarized light scattering is a spectroscopic technique operating in the GHz–THz range that, applied to aqueous solutions of biomolecules, is able to disentangle the ...dynamics of the solute from that of water, and relaxation processes of bulk from those of hydration water. Experiments performed on aqueous solution of a variety of biological systems of different nature, such as small hydrophobic and hydrophilic molecules, amino acids, dipeptides, and proteins, have shown that a significant increase in the dynamical retardation and in the extent of the perturbation of water surrounding solute molecules occurs at increasing chemical complexity of the solute. The behavior of aqueous solutions of lysozyme is here analyzed in detail, as a function of solute concentration. Our results provide evidence of a dynamical perturbation extending over more than three water layers in diluted solutions. We find a strong reduction in the average hydration number at increasing solute concentration that cannot be explained by the random superposition of hydration layers among lysozyme molecules in close proximity. This behavior is consistent with the formation of clusters in solution.
•Biologic molecules strongly affect the dynamics of surrounding water molecules.•Depolarized Light Scattering is used to single out the dynamics of hydration water.•Diluted water-lysozyme solutions are studied.•A dynamical perturbation extending over more than three water layers is found.
PDF
