Innovative label-free microspectroscopy, which can simultaneously collect Brillouin and Raman signals, is used to characterize the viscoelastic properties and chemical composition of living cells with sub-micrometric resolution. The unprecedented statistical accuracy of the data combined with the high-frequency resolution and the high contrast of the recently built experimental setup permits the study of single living cells immersed in their buffer solution by contactless measurements. The Brillouin signal is deconvoluted in the buffer and the cell components, thereby revealing the mechanical heterogeneity inside the cell. In particular, a 20% increase is observed in the elastic modulus passing from the plasmatic membrane to the nucleus as distinguished by comparison with the Raman spectroscopic marker. Brillouin line shape analysis is even more relevant for the comparison of cells under physiological and pathological conditions. Following oncogene expression, cells show an overall reduction in the elastic modulus (15%) and apparent viscosity (50%). In a proof-of-principle experiment, the ability of this spectroscopic technique to characterize subcellular compartments and distinguish cell status was successfully tested. The results strongly support the future application of this technique for fundamental issues in the biomedical field.

The photoluminescence properties of a silicate glass coactivated with silver and erbium ions were studied. Absorption and photoluminescence spectra allowed to distinguish in the glasses several active species related to the silver, whose ratio depends on heat treatment and silver concentration. The broad emission of silver related species in the visible region of the spectrum has been studied in correlation with the nonresonant excitation of the erbium ions. The comparison of the excitation spectra of silver and erbium shows that the erbium ions are excited through radiative and nonradiative energy transfer from small silver aggregates.

The process in which locally confined epithelial malignancies progressively evolve into invasive cancers is often promoted by unjamming, a phase transition from a solid-like to a liquid-like state, which occurs in various tissues. Whether this tissue-level mechanical transition impacts phenotypes during carcinoma progression remains unclear. Here we report that the large fluctuations in cell density that accompany unjamming result in repeated mechanical deformations of cells and nuclei. This triggers a cellular mechano-protective mechanism involving an increase in nuclear size and rigidity, heterochromatin redistribution and remodelling of the perinuclear actin architecture into actin rings. The chronic strains and stresses associated with unjamming together with the reduction of Lamin B1 levels eventually result in DNA damage and nuclear envelope ruptures, with the release of cytosolic DNA that activates a cGAS–STING (cyclic GMP-AMP synthase–signalling adaptor stimulator of interferon genes)-dependent cytosolic DNA response gene program. This mechanically driven transcriptional rewiring ultimately alters the cell state, with the emergence of malignant traits, including epithelial-to-mesenchymal plasticity phenotypes and chemoresistance in invasive breast carcinoma.

The huge number of electronic devices called the Internet of Things requires miniaturized, autonomous and ecologically sustainable power sources. A viable way to power these devices is by converting mechanical energy into electrical through electro-active materials. The most promising and widely used electro-active materials for mechanical energy harvesting are piezoelectric materials, where the main one used are toxic or not biocompatible. In this work, we focus our attention on biocompatible and sustainable piezoelectric materials for energy harvesting. The aim of this work is to facilitate and expedite the effort of selecting the best piezoelectric material for a specific mechanical energy harvesting application by comprehensively reviewing and presenting the latest progress in the field. We also identify and discuss the characteristic property of each material for each class to which the material belong to, in terms of piezoelectric constants and achievable power.

Low wavenumber Raman scattering of the acoustic vibrational modes of nanoparticles was used for the determination of the size distribution of free dielectric and semiconductor nanoparticles and of nanoparticles embedded in matrices. The theoretical background as well as the experimental results for the free noninteracting nanoparticles and for the nanoparticles in strong interaction with a surrounding matrix is described. The approach is based on a 1/ν dependence of the Raman light‐to‐vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its eigenfrequency ν ∼ 1/D. The model calculation considers the inhomogeneous broadening due to contribution from the particles of different sizes, and homogeneous broadening due to interaction of particles with the matrix. The comparison of the calculated and experimental low wavenumber Raman spectra are presented for SnO₂, TiO₂ and CdS free nanoparticles and TiO₂, CdS_xSe_1−x and HfO₂ nanoparticles embedded in a glass matrix. The particle‐size distributions determined by Raman scattering were compared to those found by TEM measurements. Raman spectroscopy proved to be a simple, fast and reliable method for size‐distribution measurements. By an inverse procedure, starting from the Raman spectra and known particle‐size distribution, a new method for the determination of the mean sound velocities of longitudinal and transverse phonons of nanoparticles is described. Copyright © 2007 John Wiley & Sons, Ltd.