arXiv subjects

Silvia Caponi

Publications and source records attributed to Silvia Caponi.

6 recordsLinked to original sources

arXiv2024

Consensus Statement on Brillouin Light Scattering Microscopy of Biological Materials

Brillouin Light Scattering (BLS) spectroscopy is a non-invasive, non-contact, label-free optical technique that can provide information on the mechanical properties of a material on the sub-micron scale. Over the last decade it has seen increased applications in the life sciences, driven by the observed significance of mechanical properties in biological processes, the realization of more sensitive BLS spectrometers and its extension to an imaging modality. As with other spectroscopic techniques, BLS measurements not only detect signals characteristic of the investigated sample, but also of the experimental apparatus, and can be significantly affected by measurement conditions. The aim of this consensus statement is to improve the comparability of BLS studies by providing reporting recommendations for the measured parameters and detailing common artifacts. Given that most BLS studies of biological matter are still at proof-of-concept stages and use different--often self-built--spectrometers, a consensus statement is particularly timely to assure unified advancement.

physics.optics↗

arXiv2021

Brillouin imaging in turbid samples: the removal of multiple scattering contribution

We provide a new analytic expression and an innovative experimental method to isolate the effect of multiple scattering (MS) in Brillouin investigation of highly turbid media. On the one hand, an analytic model is given to describe the spectrum in case of ill-defined exchanged wave-vector. On the other hand, a new experimental method, named Polarization Gated Brillouin Spectroscopy (PG-BS), is proposed for selecting the MS contribution through light polarization. Both experimental and analytic methods are tested against a benchmark material, milk, demonstrating their capability to extract reliable micro-mechanical parameters even in highly turbid materials till now inaccessible to in-depth Brillouin scattering investigation.

physics.optics↗

arXiv2020

Monitoring the refractive index of tissue models using light scattering spectroscopy

In this work, we report the application of Raman microspectroscopy for analysis of the refractive index of a range of tissue phantoms. Using both a custom-developed setup with visible laser source and a commercial micro-spectrometer with near infrared laser, we measured the Raman spectra of gelatin hydrogels at various concentrations. By building a calibration curve from measured refractometry data and Raman scattering intensity for different vibrational modes of the hydrogel, we determined the refractive indices of the gels from their Raman spectra, with approximately the same accuracy as that of refractometry measurements with an Abbe refractometer. This work highlights the importance of a correlative approach through Brillouin-Raman microspectroscopy for the mechano-chemical analysis of biologically relevant samples.

physics.bio-ph↗

arXiv2020

On the actual spatial resolution of Brillouin Imaging

Brillouin imaging is an emerging optical elastography technique able to generate maps of the mechanical properties at microscale, with great potential in biophysical and biomedical fields. A key parameter is its spatial resolution, which is usually identified with that of the confocal microscope coupled to the Brillouin interferometer. Conversely, here we demonstrate that the mean free path of acoustic phonons plays a major role in defining the resolution, especially for high numerical aperture confocal setups. Surprisingly, the resolution of elastography maps may even deteriorate when decreasing the scattering volume.

physics.optics↗

arXiv2019

Brillouin-derived viscoelastic parameters of hydrogel tissue models

Many problems in mechanobiology urgently require characterisation of the micromechanical properties of the fibrous proteins of cells and tissues. Brillouin light scattering has been proposed as a new optical elastography technique to meet this need, but the information contained in the Brillouin spectrum is still a matter of debate. Here we investigate this question using gelatin as a model system in which the macroscopic physical properties can be manipulated to mimic all the relevant biological states of matter, ranging from the liquid to the gel and the glassy phase. We demonstrate that Brillouin spectroscopy is a powerful tool to reveal both the elastic and viscous properties of biomaterials that are central to their biological functions.

physics.bio-ph↗

arXiv2013

Stress-induced modification of the boson peak scaling behavior

The scaling behavior of the so-called boson peak in glass-formers and its relation to the elastic properties of the system remains a source of controversy. Here, the boson peak in a binary reactive mixture is measured by Raman scattering (i) on cooling the unreacted mixture well below its glass transition temperature and (ii) after quenching to very low temperature the mixture at different times during isothermal polymerization. These different paths to the glassy phase are able to generate glasses with different amounts of residual stresses, as evidenced by the departure of the elastic moduli from a Cauchy-like relationship. We find that the scaling behavior of the boson peak with the properties of the elastic medium --- as measured by the Debye frequency --- holds for states in which the system is able to release internal stress and breaks down in the presence of residual stresses. These findings provide new insight into the boson peak behavior and are able to reconcile the apparently conflicting results presented in literature.

cond-mat.soft↗