Biomechanical properties of mammalian bones, such as strength, toughness, and plasticity, are essential for understanding how microscopic-scale mechanical features can link to macroscale bones’ strength and fracture resistance. We employ Brillouin light scattering (BLS) microspectroscopy for local assessment of elastic properties of bones under compression and the efficacy of the tissue engineering approach based on heparin-conjugated fibrin (HCF) hydrogels, bone morphogenic proteins, and osteogenic stem cells in the regeneration of the bone tissues. BLS is noninvasive and label-free modality for probing viscoelastic properties of tissues that can give information on structure-function properties of normal and pathological tissues. Results showed that MCS and BPMs are critically important for regeneration of elastic and viscous properties, respectively, HCF gels containing combination of all factors had the best effect with complete defect regeneration at week nine after the implantation of bone grafts and that the bones with fully consolidated fractures have higher values of elastic moduli compared with defective bones.
Biomechanical properties of mammalian bones, such as strength, toughness and plasticity, are essential for understanding how microscopic scale mechanical features can link to macroscale bones’ strength and fracture resistance. We employ Brillouin light scattering (BLS) micro-spectroscopy for local assessment of elastic properties of bones under compression and the efficacy of the tissue engineering approach based on heparin-conjugated fibrin (HCF) hydrogels, bone morphogenic proteins (BMPs) and osteogenic stem cells in the regeneration of the bone tissues. BLS is noninvasive and label-free imaging modality for probing mechanical properties of hard tissues that can give information on structure-function properties of normal and pathological tissues. Results showed that HCF gels containing combination of all factors had the best effect with complete defect regeneration at week 9 and that the bones with fully consolidated fractures have higher values of elastic moduli compared to the bones with defects.
Raman and Brillouin spectroscopic provide with a powerful way to non-invasively assess both chemical and physical (viscoelastic) properties. In this report, Brillouin microspectroscopy was used for real time analysis of elastic properties of Populus and Geranium leaves, while Raman spectroscopy and imaging were employed for assessment of their chemical variation during drying. When used together, those techniques can improve our understanding of mechanochemical changes of plants in response to environmental stress and pathogens at microscopic (cellular) level. Our results have demonstrated for the first time the ability of multimodal assessment of elasticity modulus, hydraulic conductance and interatomic vibrational modes in plants as emerging new markers for real time quantitative assessment of agricultural crops.
Brillouin spectroscopy is a powerful tool for elasticity-sensitive non-invasive optical imaging. However, its relatively weak signal strength usually results long acquisition time and poor spectral quality. In this study, enhancements of Brillouin scattering at 532 nm was observed from various acoustic modes of alkaline-earth boroaluminosilicate glass coated with periodic arrays of gold nanodisks. The similar enhancements were also observed from the bulk phonons within the various liquids (including methanol and water) covered on the gold nanodisks. This enhancement is considered to be attributed by the surface plasmons generated by the nanostructures, and is found to be dependent on their geometries (i.e., aspect ratio and diameter) of the golden nanodisks. When employing the recent advances in virtually imaged phased array (VIPA) based background-free Brillouin spectrometers, the acquisition time could even be further optimized. The results of this study suggest that nanodisk arrays can provide a platform for practical implementation of surface-enhanced Brillouin scattering analogous to other surface-enhanced spectroscopies, and suggest an approach for further reduce the integration time for Brillouin spectroscopy.
Distributions of electric fields in two-dimensional arrays of gold nanodisks on Si3N4 membranes are modeled by
use of the discrete-dipole approximation as a function of nanodisk diameter (20 nm to 50 nm), height (10 nm to
100 nm), ratio of the array spacing to diameter (1.3 to 4.7), and angle of incident light. The primary focus is on
fields in a plane near the circular gold/vacuum interface with light of 532 nm wavelength incident through the
membrane, a configuration that is particularly relevant to potential applications in plasmon-mediated Brillouin
light scattering, nanolithography, and photovoltaics. The height/diameter ratio for maximum intensities over this
plane is between 0.7 and 1.5 and not strongly dependent on the spacing for a given angle. The average intensity
increases with decreasing array spacing and incident angle relative to the substrate normal. This dependence is
attributed primarily to a combination of fractional coverage area of the gold and increased excitation of a dipolar
contribution to the fields. The incident light at 532 nm simultaneously excites dipolar and quadrupolar surface-plasmon
modes. Because the quadrupolar mode has a peak close to 532 nm, its excited fields are approximately
out of phase with the incident light.
Enhancement of Brillouin light scattering (BLS) at the wavelength of 532 nm was observed from Rayleigh-like and
Sezawa-like acoustic modes of alkaline-earth boro-aluminosilicate glass covered with periodic arrays of gold nanodisks.
This enhancement is attributed to mediation of surface plasmons of the nanodisks. For nanodisks with diameters of 71
nm to 90 nm, heights of 30 nm, and periodicity of 100 nm, the maximum measured surface-plasmon enhancement of
BLS intensity was, respectively, ~ 2.4 and ~ 5.6 for Rayleigh-like and Sezawa-like modes, relative to the intensity from a
gold film with the same fractional coverage area but without surface-plasmon coupling. The maximum for the Rayleigh-like
modes occurs with the smallest-diameter nanodisks, and that for the Sezawa-like modes occurs with the largest-diameter
nanodisks. The angular dependence is relatively broad. Calculations employing the discrete dipole
approximation were used to predict the electric-field intensities in the gold disks and nearby glass as a function of
nanodisk diameter. The average calculated intensity at the top surface of the gold increases with decreasing diameter,
consistent with the experimental results for Rayleigh-like modes and the expectation that surface ripple is the dominant
scattering mechanism for such modes. The results of this study suggest that nanodisk arrays can provide a platform for
practical implementation of surface-enhanced BLS analogous to other surface-enhanced spectroscopies, and suggest the
additional possibility of substantially extending the range of wave numbers in BLS through plasmonic-crystal band
folding.
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