Noninvasive methods for in situ electrical stimulation of human cells open new frontiers to future bioelectronic therapies, where controlled electrical impulses could replace the use of chemical drugs for disease treatment. Here, this study demonstrates that the interaction of living cells with piezoelectric nanogenerators (NGs) induces a local electric field that self-stimulates and modulates their cell activity, without applying an additional chemical or physical external stimulation. When cells are cultured on top of the NGs, based on 2D ZnO nanosheets, the electromechanical NG-cell interactions stimulate the motility of macrophages and trigger the opening of ion channels present in the plasma membrane of osteoblast-like cells (Saos-2) inducing intracellular calcium transients. In addition, excellent cell viability, proliferation, and differentiation are validated. This in situ cell-scale electrical stimulation of osteoblast-like cells can be extrapolated to other excitable cells such as neurons or muscle cells, paving the way for future bioelectronic medicines based on cell-targeted electrical impulses.

Remote microactuators are of great interest in biology and medicine as minimally-invasive tools for cellular stimulation. Remote actuation can be achieved by active magnetostrictive transducers which are capable of changing shape in response to external magnetic fields thereby creating controlled displacements. Among the magnetostrictive materials, Galfenol, the multifaceted iron-based smart material, offers high magnetostriction with robust mechanical properties. In order to explore these capabilities for biomedical applications, it is necessary to study the feasibility of material miniaturization in standard fabrication processes as well as evaluate the biocompatibility. Here we develop a technology to fabricate, release, and suspend Galfenol-based microparticles, without affecting the integrity of the material. The morphology, composition and magnetic properties of the material itself are characterized. The direct cytotoxicity of Galfenol is evaluated in vitro using human macrophages, osteoblast and osteosarcoma cells. In addition, cytotoxicity and actuation of Galfenol microparticles in suspension are evaluated using human macrophages. The biological parameters analyzed indicate that Galfenol is not cytotoxic, even after internalization of some of the particles by macrophages. The microparticles were remotely actuated forming intra- and extracellular chains that did not impact the integrity of the cells. The results propose Galfenol as a suitable material to develop remote microactuators for cell biology studies and intracellular applications.

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Saos‐2 cells are cultured on top of piezoelectric nanogenerators (NGs) based on ZnO nanosheets for electrical self‐stimulation by Gonzalo Murillo, Carme Nogués, and co‐workers in article number https://doi.org/10.1002/adma.201605048. Imaging by scanning electron microscopy (SEM) shows that the cells are firmly adhered to the nanosheets. The cells show excellent viability, proliferation, and differentiation. The NGs can be used to electrically self‐stimulate different types of cells, such as neurons or muscle cells, without applying a chemical or physical external stimulation, leading to future bioelectronic medicines based on cell‐targeted local electrical impulses.

Local electric stimulation of tissues and cells has gained importance as therapeutic alternative in the treatment of many diseases. These alternatives aim to deliver a less invasively stimuli in liquid media, making imperative the development of versatile micro- and nanoscale solutions for wireless actuation. Here, a simple microfabrication process to produce suspended silicon microphotodiodes that can be activated by visible light to generate local photocurrents in their surrounding medium is presented. Electrical characterization using electrical probes confirms their diode behavior. To demonstrate their electrochemical performance, an indirect test is implemented in solution through photoelectrochemical reactions controlled by a white-LED lamp. Furthermore, their effects on biological systems are observed in vitro using mouse primary neurons in which the suspended microphotodiodes are activated periodically with white-LED lamp, bringing out observable morphological changes in neuronal processes. The results demonstrate a simplified and cost-effective wireless tool for photovoltaic current generation in liquid media at the microscale.

This work presents a sensor composed of a differential arrangement of coils capable of measuring nanometric metallic film thickness. Experimental results achieved aluminium thickness measurements as low as 20 nm with a sensitivity of 3.8 mV/nm. This makes this sensor a flexible, nondestructive and cheap alternative for metallic thickness measurement down to nanometric scale.

In article number https://doi.org/10.1002/smll.201701920, by Carlos A. Saura, Jaume Esteve, and co‐workers, suspended silicon microphotodiodes are fabricated as a simple and cost‐effective microtool able to deliver photocurrent in liquid media. Electrical and electrochemical characterization under on/off illumination conditions was performed. Their effectiveness as remote photovoltaic cells for life science applications was evaluated in vitro with cultured neurons.