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In recent decades, mechanobiology has emerged as a novel perspective in the context of basic biomedical research. It is now widely recognized that living cells respond not only to chemical stimuli (for example drugs), but they are also able to decipher mechanical cues, such as the rigidity of the underlying matrix or the presence of shear forces. Probing the viscoelastic properties of cells and their local microenvironment with sub-micrometer resolution is required to study this complex interplay and dig deeper into the mechanobiology of single cells. Current approaches to measure mechanical properties of adherent cells mainly rely on the exploitation of miniaturized indenters, to poke single cells while measuring the corresponding deformation. This method provides a neat implementation of the everyday approach to measure mechanical properties of a material, but it typically results in a very low throughput and invasive experimental protocol, poorly translatable towards three-dimensional living tissues and biological constructs. To overcome the main limitations of nanoindentation experiments, a radical paradigm change is foreseen, adopting next generation contact-less methods to measure mechanical properties of biological samples with sub-cell resolution. Here we briefly introduce the field of single cell mechanical characterization, and we concentrate on a promising high resolution optical elastography technique, Brillouin spectroscopy. This non-contact technique is rapidly emerging as a potential breakthrough innovation in biomechanics, but the application to single cells is still in its infancy.

Determining the thickness of a few-layer 2D material is a tough task that often involves complex and time consuming measurements. Here we discuss a rapid method for determining the number of layers of molybdenum disulfide, MoS$$_2$$ 2 , flakes based on microscopic transmission imaging. By analyzing the contrast of the red, blue and green channels of the flake image against the background, we show that it is possible to unequivocally determine the number of layers. The presented method is based on the light absorption properties of MoS$$_2$$ 2 and its validity is confirmed by micro-Raman measurements. The main advantage of this method against traditional methods is to quickly determine the thickness of the material in the early stages of the experimental process with low cost apparatus.

This work is focused on the preparation and multi-technique characterization of potentially biocompatible reactive interfaces obtained by combining layered double hydroxides (LDHs) and hydroxyapatite (HA). Antimicrobial and osteoinductive metallic ions as Zn2+ and Ga3+ were chosen as intralayer constituents of LDH to obtain ZnAl and ZnAlGa systems. These LDHs, exchanged with dihydrogenphosphate anions, promoted the precipitation of HA on the LDH surface yielding HA@LDH composites. X-ray diffraction quantitative analysis, through the Rietveld refinement method, coupled with elemental analysis and micro-Raman spectroscopy showed the formation of a mixed Ca-Zn HA phase. Scanning electron microscopy revealed that HA, in the presence of LDH, grew preferentially along its a-axis, thus crystallizing mainly in the form of flake crystals. LDH and HA@LDH composites showed antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa at not cytotoxic concentrations for human osteoblasts (hFob 1.19), especially when Ga cations were present in the LDH structure. The effect of the presence of HA in the composites on the bone-bonding ability and on human osteoblast proliferation was also investigated. The HA seemed to reduce the toxicity of the LDH toward human osteoblast while did not affect the bone-bonding ability. This multidisciplinary study provides the bio-chemical, structural characterization of new LDH and HA@LDH composites, evaluating also their bioactivity to be potentially applicable to titanium-based prostheses.

The recovery of the protein component and its transformation into protein hydrolysates, generally carried out chemically, gives great added value to waste biomasses. The production of protein hydrolysates through enzymatic catalysis would guarantee to lower the environmental impact of the process and raise product quality, due to the reproducible formation of low molecular weight peptides, with interesting and often unexplored biological activities. The immobilization of the enzymes represents a good choice in terms of stability, recyclability and reduction of costs. In this context, we covalently linked proteases from Aspergillus oryzae to polylactic acid an eco-friendly biopolymer. The hydrolytic efficiency of immobilized enzymes was assessed testing their stability to temperature and over time, and checking the hydrolysis of model biomasses (casein and bovine serum albumin). Soybean waste extracts were also used as proof of principle.

Objective: To compare the mechanical and biological features of a polymethylmethacrylate (PMMA) disc for CAD/CAM prostheses (test samples, TG) with a traditional resin (control samples, CG). Methods: Mechanical analysis was performed using Dynamic Mechanical Analysis (DMA) and Brillouin's micro-spectroscopy. Human keratinocyte morphology and adhesion were analyzed by scanning electronic microscopy (SEM), cytotoxicity by the MTT assay, apoptosis by flow cytometry and p53, p21 and bcl2 gene expression by real time PCR. Results: TG exhibited a higher elastic modulus than CG (range 5100-5500 ± 114.3 MPa vs 3000-3300 ± 99.97 MPa). The Brillouin frequency was found at ?= (15.50 ± 0.05) GHz for TG and at ? = (15.50 ± 0.05) GHz and ? = (15.0 ± 0.1) GHz for CG where two peaks were always present independently of the sample point. SEM analysis revealed that keratinocytes on TG disks appeared to be flattened with lamellipodia. Keratinocytes on CG disks rose above the substrate with cytoplasmatic filaments. MTT viability data at 3 h and 24 h showed TG was significantly less cytotoxic than CG (p < 0.001). No significant differences emerged in apoptosis on CG and TG. Real-time PCR showed p53 expression increased after 3 h by about 9-fold in keratinocytes on TG (p < 0.001) and about 5-fold in those on CG (p < 0.001). High p53 expression persisted after 24 h on both disks. No significant variations were observed in p21 and bcl2 expression at any time-point. Significance: PMMA resins, as used in CAD/CAM technology, displayed suitable biocompatible and mechanical properties for removable prostheses.

Brillouin and Raman imaging are powerful techniques for the investigation of complex materials and they are widely used in material science and biophysics [1], [2], [3], [4], [5], [6], [7]. When dealing with microstructures, the results interpretation requires an accurate understanding of the interaction processes in presence of acoustic and chemical boundaries between different materials [8], [9], [10], [11], [12], [13], [14], [15]. The data here reported are obtained while scanning with sub-micron resolution the sharp interfaces between vitreous-SiO2/Water and Polyethylene (PET)/Glycerol. Molecular and acoustic vibrations were observed by means of a recently developed micro-spectrometer, which acquires simultaneously Raman and Brillouin spectra on the same point with high spatial and spectral resolution [3]. Two external optic configurations were adopted in order to evidence the dependency of the measurements on the optical scattering volume. The evolution of the detected phonon modes, propagating and not propagating, is obtained by a direct observation of the raw data for the two interfaces, which present different acoustic mismatch. These experimental records can be exploited by researchers employing Raman and Brillouin imaging to discuss the resolution limit of the techniques and to compare the effect of different experimental set-ups. Moreover, thanks to their high spectral resolution they can be useful to researchers working on acoustic phonon transport at interfaces to model the dependency of transmission of long wavelength phonons on the acoustic mismatch.

Recent advances in photonics technologies pushed optical microscopy towards new horizons in materials characterization. In this framework, Brillouin microscopy emerged as an innovative method to provide images of materials with mechanical contrast without any physical contact, but exploiting the light-matter interaction. Brillouin imaging holds a great promise; to allow mechanical analysis inside soft and heterogeneous materials, addressing the pivotal role played by viscoelastic properties in the physiology and pathology of living tissues and cells. Nevertheless, extending the approach of Brillouin imaging to characterize elastic heterogeneities of micro and nanostructured samples is especially challenging, and it poses a critical question about the actual spatial resolution reachable in the mechanical characterization. We focus this critical review on the key quantities that define the spatial resolution in the Brillouin scattering process, and we highlight that not only the optical focalization of the light, but also the acoustic excitations present in the material, influence the information collected from a sample by Brillouin imaging. Referring to the body of knowledge gained in the field of material science, we review new results and recently obtained progresses in the more unexplored context of life science. In future developments, a comprehensive strategy to tackle both the acoustic and optical aspects of the measurement will be required to maximize the efficacy of the technique.

Gelatin hydrogels cover a wide range of microenvironments that are relevant for bioapplications of Brillouin elastography., Many problems in mechanobiology urgently require characterization of the micromechanical properties of cells and tissues. Brillouin light scattering has been proposed as an emerging optical elastography technique to meet this need. However, the information contained in the Brillouin spectrum is still a matter of debate because of fundamental problems in understanding the role of water in biomechanics and in relating the Brillouin data to low-frequency macroscopic mechanical parameters. 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 able to reveal both the elastic and viscous properties of biopolymers that are central to the structure and function of biological tissues.

Tissue morpho-mechanics is gaining an increasing relevance in various fields, including biology, medicine, pathology, tissue engineering, and regenerative medicine, since it targets the relationship between morphological features and mechanical properties in biological tissues, which plays an important role in various biological processes including metastasis, wound healing and tissue regeneration. In particular, in every biological tissue, morphological, biochemical and mechanical properties are tightly connected and they influence each other in a correlative manner. For this reason, a correlative approach employing multiple techniques is ideal for targeting tissue morpho-mechanics with an optical approach. Here we report a correlative study performed by optical microscopies, disclosing the supramolecular collagen morphology correlated with its biomechanical and biochemical analyses. In particular, using human corneal tissue as a benchmark, we correlate Second-Harmonic Generation maps with mechanical and biochemical imaging obtained by Brillouin and Raman micro-spectroscopy, demonstrating that the peculiar mechanical functionality of so-called sutural lamellae originates from their distinctive supramolecular organization. A theoretical model based on the ultrastructural symmetry of corneal lamellar domains provides the interpretation of the experimental data at the molecular scale. The proposed methodology opens the way to the non-invasive assessment of tissue morpho-mechanics and holds the potential to be applicable to a broad range of biological and synthetic materials.

Tissue morpho-mechanics is gaining increasing in various fields, because it targets the relationship between morphological features and mechanical properties in biological tissues, which plays an important role in various fields including biology, medicine, pathology, tissue engineering, and regenerative medicine. The intimate connection between morphological, biochemical and mechanical properties in biological tissues requires a multimodal correlative approach for their exhaustive investigation. In this study, we used Second-Harmonic Generation in combination with Brillouin and Raman micro-spectroscopy in order to correlate collagen morphology at the ultrastructural level with its biomechanical and biochemical features. In particular, by imaging human corneal tissue samples with our multimodal approach, we demonstrated that the peculiar mechanical properties of corneal lamellae in the anterior portion of the corneal stroma are due to a different supramolecular organization, rather than to a different biochemical composition. This result opens new insights in the study and interpretation of corneal biomechanics thanks to the possibility of non-invasively correlating lamellar morphology with visco-elastic properties. The proposed method opens the way to the non-invasive assessment of corneal morpho-mechanics and holds the potential to be used for both diagnostic and follow-up purposes in pathologies that affect corneal biomechanics.

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.

Tissue morpho-mechanics is gaining an increasing relevance in various fields, including biology, medicine, pathology, tissue engineering, and regenerative medicine, since it targets the relationship between morphological features and mechanical properties in biological tissues, which plays an important role in various biological processes including metastasis, wound healing and tissue regeneration. In particular, in every biological tissue, morphological, biochemical and mechanical properties are tightly connected and they influence each other in a correlative manner. For this reason, a correlative approach employing multiple techniques is ideal for targeting tissue morpho-mechanics with an optical approach. Here we report a correlative study performed by optical microscopies, disclosing the supramolecular collagen morphology correlated with its biomechanical and biochemical analyses. In particular, using human corneal tissue as a benchmark, we correlate Second-Harmonic Generation maps with mechanical and biochemical imaging obtained by Brillouin and Raman micro-spectroscopy, demonstrating that the peculiar mechanical functionality of so-called sutural lamellae originates from their distinctive supramolecular organization. A theoretical model based on the ultrastructural symmetry of corneal lamellar domains provides the interpretation of the experimental data at the molecular scale. The proposed methodology opens the way to the non-invasive assessment of tissue morpho-mechanics and holds the potential to be applicable to a broad range of biological and synthetic materials.

Brillouin imaging is an emerging optical elastography technique that is 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.

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., Comment: 11 pages, 5 figures, 1 table

The distribution of chemical species and the mechanical modulation inside a single cell or tissue are of fundamental importance to characterize their physiological activity or their pathological conditions [1–4]. Here we analyse these properties by means of label free, non invasive, spectroscopic methods. In particular, we use a recently developed micro-spectrometer, which acquires simultaneously Raman and Brillouin spectra on the same point with subcellular resolution [5]. The techniques ability to analyse the chemical composition and the mechanical properties of single cells has been tested on NIH/3T3 murine fibroblast cells grown in adhesion on silicon substrates. Here we report the data acquired from fixed cells after their oncogenic transformation. Mechanical and chemical evolution is evident by direct inspection of raw data. Sharing our experimental records can be valuable for researchers interested in the analysis of single cells by Raman and Brillouin spectroscopy in order: i) to compare data acquired by different set-ups and ii) to correctly model the fitting functions. Keywords: Biophotonics, Brillouin spectroscopy, Raman spectroscopy, Cell mechanics

SH-SY5Y cell line is a model for neural diseases originating from neuroblastoma, a paediatric embryonal malignancy that may differentiate and regress to a benign state. By monitoring the differentiation in single living cells, it could be possible to reach a better understanding of the process and, consequently, to develop new therapeutic approaches. In this work, we investigated the potential of Raman microspectroscopy to monitor biochemical changes in single living SH-SY5Y cells treated with a combination of retinoic acid (RA) and brain-derived neurotrophic factor to stimulate the differentiation toward a neuronal phenotype. The results show that the spectroscopic analysis is able to detect biochemical alterations consistent with the differentiation process. Moreover, we investigated also the influence of the cell culture substrate on the treatment outcome. Silicon and aluminium are 2 materials suitable for the spectroscopic analysis and of interest in neuroscience applications. Even though silicon has an ensured biocompatibility, it is subject to alterations after the treatment with RA. Aluminium revealed to be a cost-effective cell culture substrate for the RA and brain-derived neurotrophic factor treatment of SH-SY5Y cells and particularly suitable for Raman microspectroscopy. Copyright © 2018 John Wiley & Sons, Ltd.

We report a comprehensive study of the biocompatibility and neurocompatibility of titanium dioxide films (TiO2) prepared by Pulsed Microplasma Cluster Source (PMCS). This technique uses supersonic pulsed beams seeded by clusters of the metal oxide synthesized in a plasma discharge. The final stoichiometry of the TiO2 thin films is tuned changing the gas mixture, achieving stoichiometric or oxygen overstoichiometric films. All the films showed consistent biocompatibility and a spontaneous absorption of poly-d-lysine (PDL) that favors the adhesion and growth of murine cortical neurons. Moreover, the bioelectrical activity of the neuronal culture grown on the TiO2 film can be modulated by changing the chemistry of the surface. This work paves the way to develop a bio-hybrid neuromorphic device, where viable nerve cells are grown directly over a titanium dioxide film showing a network of memristors.

In every biological tissue, morphological and topological properties strongly affect its mechanical features and behaviour, so that ultrastructure, composition and mechanical parameters are intimately connected. Overall, it is their correct interplay that guarantees the tissue functionality. The development of experimental methods able to correlate these properties would open new opportunities both in the biological and the biomedical fields. Here, we report a correlative study intended to map supramolecular morphology, biochemical composition and viscoelastic parameters of collagen by all-optical microscopies. In particular, using human corneal tissue as a benchmark, we correlate Second-Harmonic Generation maps with mechanical and biochemical imaging obtained by Brillouin and Raman micro-spectroscopy. The study highlights how subtle variations in supramolecular organization originate the peculiar mechanical behavior of different subtypes of corneal lamellae. The presented methodology paves the way to the non-invasive assessment of tissue morpho-mechanics in biological as well as synthetic materials., Raffaella Mercatelli et al. present a method incorporating Brillouin and Raman microscopy with Second-Harmonic-Generation microscopy. They examine human corneas, showing an unprecedented combination of viscoelastic, biochemical, and morphological properties of collagen.

An increasing effort is currently devoted to developing Raman spectroscopy for identification of microorganisms. Micro-Raman setups are typically used for this purpose with the limit that the intra-species and inter-species spectral variability are comparable, thus limiting the identification capability. To overcome this limit a meso-Raman approach is here implemented. Thin films of planktonic cells are analyzed throughout the collection of back-scattered light providing a Raman signal already averaged over tens of cells. The collecting of unpolarized (VU) and depolarized (HV) Raman signals increased the spectral information obtainable from the data, demonstrating the ability of the principal component analysis to differentiate the most common Candida species, namely C. glabrata, C. albicans, C. parapsilosis and C. tropicalis. The proposed method can contribute to bring Raman spectroscopy closer to its potential clinical use for fast identification of yeast cells.

The interfacing of artificial devices with biological systems is a challenging field that crosses several disciplines ranging from fundamental research (biophysical chemistry, neurobiology, material and surface science) to frontier technological application (nanotechnology, bioelectronics). The memristor is the fourth fundamental circuit element, whose electrical properties favor applications in signal processing, neural networks, and brain-computer interactions and it represents a new frontier for technological applications in many fields including the nanotechnologies, bioelectronics and the biosensors. Using multidisciplinary approaches, covering surface science, cell biology and electrophysiology, we successfully implemented a living bio-hybrid system constituted by cells adhering to films of poly(aniline) (PANI), a semiconductor polymer having memristive properties assembled with polyelectrolytes. Here we tested whether the PANI devices could support survivor, adhesion and differentiation of several cell lines, including the neuron-like SHSY5Y cells. Moreover, we performed electrophysiology on these cells showing that the biophysical properties are retained with differences occurring in the recorded ion currents. Taken together, the cell viability here reported is the key requirement to design and develop a reliable functional memristor-based bio-hybrid able to mimic neuronal activity and plasticity.

International audience; Electret based smart materials have been attracting increasing attention for their versatility combined with easy fabrication. In particular, electret microparticles can be embedded in micro- and nano-electronic devices, enabling applications such as sensing, actuating, biological transducers and energy harvesting. In this work, silica micro-electrets are charged by electron injection in a SEM environment. The particle charge distribution is precisely controlled adjusting the energy of the primary beam. The surface potential, measured in the SEM chamber by the shift of the Duane–Hunt limit and by secondary electron spectroscopy reaches up to 200 V for 1 micron particles. The increase of the particle surface potential with the electron penetration depth is explained by a theoretical model, which also provides the value of about 0.1 C cm−3 for the charge concentration. The charge decay is studied in time monitoring the secondary electron emission by an in–lens SEM detector, showing that most of the charge injected deeper than 200 nm is retained in the particles for several months after the charging process. The capability to reach high values of surface potential stable over time on micrometric scale makes these materials as ideal candidates for applicative purposes and strategic elements in nanotechnology.

In this study, Fourier transform infrared, Raman and Brillouin spectroscopy have been used to study lipid phase behavior of hydrated as well as dried multilamellar l-α-phosphatidylcholine assemblies, in order to compare limitations and potentials of the different techniques. Dried lipid samples have been studied in the presence and absence of trehalose, which is known to affect the phase behavior of these systems. The methylene C-H stretching (2800–3000 cm−1) region in infrared (IR) and Raman spectra provided mutually consistent information on the rearrangement of lipid acyl chains occurring at the lipid melting temperature. IR spectra have a higher signal-to-noise ratio, thus permitting a more precise evaluation of the melting temperature. In the hydrated lipid samples, the C-H stretching region in the Raman spectra is less affected by the contribution of water compared with that in the IR spectra. Raman spectra are particularly suitable to simultaneously study both lipid and water contributions allowing to distinguish ice from non-frozen water below 0 °C. Brillouin light scattering was used to probe the collective dynamics, i.e. the propagation velocity and the attenuation of longitudinal acoustic modes in the lipid samples. Lipid phase transitions are evident from a change in the temperature behavior of the acoustic velocity. Moreover, a strong relaxation process with a characteristic time of 14 ps was observed in the sample dried without trehalose with a maximum in acoustic attenuation at about 45 °C, which likely reflects the rearrangement of acyl chains. Copyright © 2015 John Wiley & Sons, Ltd.

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-matching approach to obtain complementary information from a sample. Here we demonstrate a new concept of fully scanning multimodal micro-spectroscopy 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 a spatial resolution on sub-cellular 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 mechano-chemical mapping of highly scattering biological samples., Comment: 18 pages, 4 figures

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.

We report a comprehensive study of the biocompatibility and neurocompatibility of titanium dioxide films (TiO

Brillouin spectroscopy is an emerging technique in the biomedical field. It probes the mechanical properties of a sample through the interaction of visible light with thermally induced acoustic waves or phonons propagating at a speed of a few km/sec. Information on the elasticity and structure of the material is obtained in a nondestructive contactless manner, hence opening the way to in vivo applications and potential diagnosis of pathology. This work describes the application of Brillouin spectroscopy to the study of biomechanics in elastin and trypsin-digested type I collagen fibers of the extracellular matrix. Fibrous proteins of the extracellular matrix are the building blocks of biological tissues and investigating their mechanical and physical behavior is key to establishing structure-function relationships in normal tissues and the changes which occur in disease. The procedures of sample preparation followed by measurement of Brillouin spectra using a reflective substrate are presented together with details of the optical system and methods of spectral data analysis.

A living bio-hybrid system has been successfully implemented. It is constituted by neuroblastic cells, the SH-SY5Y human neuroblastoma cells, adhering to a poly-anyline (PANI) a semiconductor polymer with memristive properties. By a multidisciplinary approach, the biocompatibility of the substrate has been analyzed and the functionality of the adhering cells has been investigated. We found that the PANI films can support the cell adhesion. Moreover, the SH-SY5Y cells were successfully differentiated into neuron-like cells for in vitro applications demonstrating that PANI can also promote cell differentiation. In order to deeply characterize the modifications of the bio-functionality induced by the cell-substrate interaction, the functional properties of the cells have been characterized by electrophysiology and Raman spectroscopy. Our results confirm that the PANI films do not strongly affect the general properties of the cells, ensuring their viability without toxic effects on their physiology. Ascribed to the adhesion process, however, a slight increase of the markers of the cell suffering has been evidenced by Raman spectroscopy and accordingly the electrophysiology shows a reduction at positive stimulations in the cells excitability.

Ionic surfactants such as sodium dodecyl sulfate (SDS) belong to the amphiphile family: they possess a long hydrophobic hydrocarbon chain and a polar hydrophilic headgroup. In a polar solvent and over the critical micellar concentration these molecules join to form micelles. The micellar solutions, in turn, if doped with various ligands tend to aggregate. Solid SDS, micelles of SDS in water and micelles of SDS doped with two types of macrocyclic ligands, Kryptofix 2.2.2 (K222) and crown ether 18-Crown-6 (18C6), at different concentrations are studied by Raman scattering, that represents a new approach to such systems. The experimental Raman spectrum, obtained on crystalline powders of SDS, is compared with the ab initio computed spectrum in order to assign the vibrational bands. After discriminating sensitive peaks by comparing the crystalline powders of the single components and their water solutions, the aggregation process and the action of the ligands are analyzed following the evolution of the intensity and wavenumber of these characteristic Raman peaks. This shows that Raman spectroscopy is sensitive to the aggregation dynamics and to the effects induced by the hydration layer on the molecules in solutions. A saturation effect in the aggregation process with the increase of the ligand concentration is observed. Copyright © 2012 John Wiley & Sons, Ltd.

An integrated experimental approach, based on inelastic light-scattering techniques, has been here employed for a multilength scale characterization of networking properties of cyclodextrin nanosponges, a new class of cross-linked polymeric materials built up from natural oligosaccharides cyclodextrins. By using Raman and Brillouin scattering experiments, we performed a detailed inspection of the vibrational dynamics of these polymers over a wide frequency window ranging from gigahertz to terahertz, with the aim of providing physical descriptors correlated to the cross-linking degree and elastic properties of the material. The results seem to suggest that the stiffness of cross-linked polymers can be successfully tuned by acting on the type and the relative amount of the cross-linker during the synthesis of a polymer matrix, predicting and controlling their swelling and entrapment properties. The proposed experimental approach is a useful tool for investigating the structural and physicochemical properties of polymeric network systems.

We report Raman scattering spectra for the network glass former vitreous germania (v-GeO2) measured in the 10–1200 K temperature range. The results show an interesting temperature dependence of the quasi-elastic scattering. Comparing this study with acoustical attenuation measured by ultrasonic absorption and Brillouin light scattering, we found that the mechanism giving rise to quasi-elastic scattering in this system seems to be the same as the one causing the acoustic attenuation.

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.

New inelastic Raman scattering experiments on the superionic glasses (AgI)(x)(AgPO3)((1-x)) were performed from room temperature up to the melting temperature. The results are compared with the acoustic attenuation measured in the frequency range between 8 and 9 GHz by Brillouin light scattering. This comparison shows that the quasielastic scattering intensity can be associated with the same mechanisms that cause sound attenuation, thereby demonstrating the same physical origin of these phenomena, in good agreement with suggested models.

The temperature dependence of the mean square displacement, 〈u2〉, calculated by elastic neutron scattering for two phosphate glasses, (AgI)x(AgPO3)1-x with x = 0.3, 0.55, is analysed. The studied samples are probed in a wide range of temperatures going from a few tens of K up to the glass transition temperature and well into the undercooled liquid state. In the low temperature regime a solid like behaviour appears, showing a linear temperature dependence of the Debye-Waller factor, while around Tg the onset of a pronounced increase of 〈u2〉 is observed. The temperature dependence of the normalized elastic intensity and the drawn out Debye-Waller factor are fitted and analyzed by the theoretical previsions of Mode Coupling Theory finding a good agreement. © 2006 Elsevier B.V. All rights reserved.

Brillouin light scattering (BLS) spectroscopy is a technique that is able to detect thermally excited phonons within a material. The speed of propagation of these phonons can be determined from the magnitude of the Brillouin frequency shift between incident and scattered light, thereby providing a measure of the mechanical properties of the material in the gigahertz range. The mechanical properties of the extracellular matrices of biological tissues and their constituent biopolymers are important for normal tissue function and disturbances in these properties are widely implicated in disease. BLS offers the prospect of measuring mechanical properties on a microscopic scale in living tissues, thereby providing insights into structure–function relationships under normal and pathological conditions. In this study, we investigated BLS in collagen and elastin—the fibrous proteins of the extracellular matrix (ECM). Measurements were made on type I collagen in rat tail tendon, type II collagen in articular cartilage and nuchal ligament elastin. The dependence of the BLS spectrum on fibre orientation was investigated in a backscattering geometry using a reflective substrate. Two peaks, a bulk mode arising from phonon propagation along a quasi-radial direction to the fibre axis and a mode parallel to the surface, depending on sample orientation relative to the fibre axis, could be distinguished. The latter peak was fitted to a model of wave propagation through a hexagonally symmetric elastic solid, and the five components of the elasticity tensor were combined to give axial and transverse Young's, shear and bulk moduli of the fibres. These were 10.2, 8.3, 3.2 and 10.9 GPa, and 6.1, 5.3, 1.9 and 8 GPa for dehydrated type I collagen and elastin, respectively. The former values are close to those previously reported. A microfocused BLS approach was also applied providing selection of single fibres. The moduli of collagen and elastin are much higher than those measured at lower frequency using macroscopic strains, and the difference between them is much less. We therefore believe, like previous investigators, that molecular-scale viscoelastic effects are responsible for the frequency dependence of the fibre biomechanics. Combining BLS with larger-scale mechanical testing methods therefore should, in the future, provide a means of following the evolution of mechanical properties in the formation of the complex structures found in the ECM.

Measurements of Raman scattering from vitreous silica (spectrosil) in the temperature range 12–1200 K are analyzed and compared with inelastic neutron scattering measurements done on the same sample. The results show a temperature dependence of the quasi-elastic scattering. Comparing this study with acoustical attenuation measured at 30 GHz by Brillouin light scattering, we found that the mechanism giving rise to quasi-elastic scattering in vitreous silica seems to be the same as the one causing the acoustic attenuation.