Tetragonal barium titanate nanoparticles (BTNPs) have been exploited as nanotransducers owing to their piezoelectric properties, in order to provide indirect electrical stimulation to SH-SY5Y neuron-like cells. Following application of ultrasounds to cells treated with BTNPs, fluorescence imaging of ion dynamics revealed that the synergic stimulation is able to elicit a significant cellular response in terms of calcium and sodium fluxes; moreover, tests with appropriate blockers demonstrated that voltage-gated membrane channels are activated. The hypothesis of piezoelectric stimulation of neuron-like cells was supported by lack of cellular response in the presence of cubic nonpiezoelectric BTNPs, and further corroborated by a simple electroelastic model of a BTNP subjected to ultrasounds, according to which the generated voltage is compatible with the values required for the activation of voltage-sensitive channels.

The identification of brown adipose deposits in adults has led to significant interest in targeting this metabolically active tissue for treatment of obesity and diabetes. Improved methods for the direct measurement of heat production as the signature function of brown adipocytes (BAs), particularly at the single cell level, would be of substantial benefit to these ongoing efforts. Here, we report the first application of a small molecule-type thermosensitive fluorescent dye, ERthermAC, to monitor thermogenesis in BAs derived from murine brown fat precursors and in human brown fat cells differentiated from human neck brown preadipocytes. ERthermAC accumulated in the endoplasmic reticulum of BAs and displayed a marked change in fluorescence intensity in response to adrenergic stimulation of cells, which corresponded to temperature change. ERthermAC fluorescence intensity profiles were congruent with mitochondrial depolarisation events visualised by the JC-1 probe. Moreover, the averaged fluorescence intensity changes across a population of cells correlated well with dynamic changes such as thermal power, oxygen consumption, and extracellular acidification rates. These findings suggest ERthermAC as a promising new tool for studying thermogenic function in brown adipocytes of both murine and human origins.

Plasmonic oligomers composed of metallic nanoparticles are one class of the most promising platforms for generating Fano resonances with unprecedented optical properties for enhancing various linear and nonlinear optical processes. For efficient generation of second-harmonic emissions at multiple wavelength bands, it is critical to design a plasmonic oligomer concurrently having multiple Fano resonances spectrally matching the fundamental excitation wavelengths and multiple plasmon resonance modes coinciding with the harmonic wavelengths. Thus far, the realization of such a plasmonic oligomer remains a challenge. This study demonstrates both theoretically and experimentally that a plasmonic nonamer consisting of a gold nanocross surrounded by eight nanorods simultaneously sustains multiple polarization-independent Fano resonances in the near-infrared region and several higher-order plasmon resonances in the visible spectrum. Due to coherent amplification of the nonlinear excitation sources by the Fano resonances and efficient scattering-enhanced outcoupling by the higher-order modes, the second-harmonic emission of the nonamer is significantly increased at multiple spectral bands, and their spectral positions and radiation patterns can be flexibly manipulated by easily tuning the length of the surrounding nanorods in the nonamer. These results provide us with important implications for realizing ultrafast multichannel nonlinear optoelectronic devices.

Mild heat stimulation of muscle cells within the physiological range represents an intriguing approach for the modulation of their functions. In this work, photothermal conversion was exploited to remotely stimulate striated muscle cells by using gold nanoshells (NSs) in combination with near-infrared (NIR) radiation. Temperature increments of approximately 5 °C were recorded by using an intracellular fluorescent molecular thermometer and were demonstrated to efficiently induce myotube contraction. The mechanism at the base of this phenomenon was thoroughly investigated and was observed to be a Ca-independent event directly involving actin-myosin interactions. Finally, chronic remote photothermal stimulations significantly increased the mRNA transcription of genes encoding heat shock proteins and sirtuin 1, a protein which in turn can induce mitochondrial biogenesis. Overall, we provide evidence that remote NIR + NS muscle excitation represents an effective wireless stimulation technique with great potential in the fields of muscle tissue engineering, regenerative medicine, and bionics.

7807wileyonlinelibrary.com respectively from the interaction of circularly or linearly polarized light with structurally chiral media in nature, such as chiral (bio)molecules and solids without any mirror symmetry. From the viewpoint of classical electrodynamics, the degeneracy between the helicity eigenmodes of light, i.e., left and right circularly polarized (LCP and RCP) waves, is broken due to cross coupling between the electric and magnetic dipoles in a chiral medium, leading to differential extinction (CD) or transmission (optical activity) for LCP/ RCP waves. These chiroptical effects provide an effective approach for manipulating polarization states of light in various optical and photonic applications, and also for sensing enantiomers of chemical molecules and determining structural conformation of biological molecules. However, these effects induced by magnetoelectric coupling in natural materials, particularly in biomolecules like amino acids, sugars, proteins, and viruses, are often very weak. [1] This unfavorable feature not only limits the ability of naturally occurring materials to effectively manipulate light polarization at the nanoscale, particularly for nanophotonics applications, but also severely restricts the application of chirality-sensitive spectroscopic techniques to samples at the microgram level. [1][2][3] Recently, plasmonic chiral metamaterials (PCMs) made of subwavelength metal nanostructures, artificially engineered chiral resonators that cannot be superimposed on their mirror images, have attracted a considerable amount of research interest. Compared with naturally occurring materials, they often have significantly enhanced chirality and thus enable many fascinating phenomena such as pronounced linear [4][5][6][7] and nonlinear chiroptical effects, [8,9] negative refraction, [10][11][12] manipulating Casimir effect, [13][14][15] unusual spin Hall effect of light, [16] and chiral-selective nonlinear imaging. [17,18] Depending on their spatial dimensions, the PCMs developed thus far can be either 2D (or planar) or 3D. The planar 2D PCMs are composed of periodic arrays of plasmonic resonators such as gold gammadions, [5,7] fish-scale, [19][20][21] and G-shape nanostructures, [22] and their chiroptical effects are generally asymmetric with respect Low-cost and large-scale fabrication of 3D chiral metamaterials is highly desired for potential applications such as nanophotonics devices and chiral biosensors. One of the promising fabrication methods is to use glancing angle deposition (GLAD) of metal on self-assembled dielectric microsphere array. However, structural handedness varies locally due to long-range disorder of the array and therefore large-scale realization of the same handedness is impossible. Here, using symmetry considerations a two-step GLAD process is proposed to eliminate this longstanding problem. In the proposed scheme, the unavoidable long-range disorder gives rise to microscale domains of the same handedness but of slightly different structural geometries and ultima...