The synaptic linearity of resistive random-access memory (RRAM) based on TiO x /HfO2 improved by inserting an ultrathin Al2O3 layer is investigated. A gradual bipolar switching with a positive set and a negative reset is observed for devices with an Al2O3 layer after an electroforming process. The devices with a 1 nm Al2O3 layer exhibit acceptable reliability with >400 cycles DC endurance with no decrement of the on/off ratio after 104 sec. A remarkable enhancement in the synaptic linearity of potentiation 2.15 and depression 1.52 is achieved in this device. The conduction mechanisms at different current regions of the optimized device are studied. The presence of the Al2O3 layer is confirmed by x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy analyses. About 42% of the oxygen vacancy concentration calculated from the XPS spectra is responsible for the synaptic properties. This synaptic RRAM structure is suitable for upcoming neuromorphic computing devices.

A remote optogenetic device for analyzing freely moving animals has attracted extensive attention in optogenetic engineering. In particular, for peripheral nerve regions, a flexible device is needed to endure the continuous bending movements of these areas. Here, a remote optogenetic optical transducer device made from a gold inverse opaline skeleton grown with a dendrite-like gold nanostructure (D-GIOF) and chemically grafted with upconversion nanoparticles (UCNPs) is developed. This implantable D-GIOF-based transducer device can achieve synergistic interaction of the photonic crystal effect and localized surface plasmon resonance, resulting in considerable UCNP conversion efficiency with a negligible thermal effect under low-intensity 980 nm near-infrared (NIR) light excitation. Furthermore, the D-GIOF-based transducer device exhibits remarkable emission power retention (≈100%) under different bending states, indicating its potential for realizing peripheral nerve stimulation. Finally, the D-GIOF-based transducer device successfully stimulates neuronal activities of the sciatic nerve in mice. This study demonstrates the potential of the implantable device to promote remote NIR stimulation for modulation of neural activity in peripheral nerve regions and provides proof of concept for its in vivo application in optogenetic engineering.

The potential clinical application of gadolinium-neutron capture therapy (Gd-NCT) for glioblastoma multiforme (GBM) treatment has been compromised by the fast clearance and nonspecific biodistribution of gadolinium-based agents. We have developed a stem cell–nanoparticle system (SNS) to actively target GBM for advanced Gd-NCT by magnetizing umbilical cord mesenchymal stem cells (UMSCs) using gadodiamide-concealed magnetic nanoparticles (Gd-FPFNP). Nanoformulated gadodiamide shielded by a dense surface composed of fucoidan and polyvinyl alcohol demonstrates enhanced cellular association and biocompatibility in UMSCs. The SNS preserves the ability of UMSCs to actively penetrate the blood brain barrier and home to GBM and, when magnetically navigates by an external magnetic field, an 8-fold increase in tumor-to-blood ratio is achieved compared with clinical data. In an orthotopic GBM-bearing rat model, using a single dose of irradiation and an ultra-low gadolinium dose (200 μg kg−1), SNS significantly attenuates GBM progression without inducing safety issues, prolonging median survival 2.5-fold compared to free gadodiamide. The SNS is a cell-based delivery system that integrates the strengths of cell therapy and nanotechnology, which provides an alternative strategy for the treatment of brain diseases.

An optimized mixture of polydopamine (PDA) and polyvinyl alcohol (PVA) is employed as the surface functionalizing agent and reducing agent to encapsulate individual polypropylene (PP) fibers of polypropylene micromembrane (PPMM). The functionalized PPMM becomes hydrophilic to allow the formation of Au nuclei for subsequent electroless Au deposition. The metalized PPMM is further deposited with IrO2 nanoparticles, and evaluated as a flexible and porous pH sensor. Images from scanning electron microscope confirms the uniform formation of IrO2 nanoparticles on Au-coated PP fibers. For pH-sensing performance, the IrO2-decorated metalized PPMM reveals a super-Nernstian response for a sensing slope of -74.45 mV/pH in aqueous solutions with pH value ranging between 2 and 12. In addition, the pH-sensing performance is properly maintained after 5000 bending cycles and hysteresis is modest in an acidic environment. The cell viability test indicates a negligible bio-toxicity. Our strategy of using a conductive polymeric membrane decorated with IrO2 nanoparticles enables possible sensing applications in wearable and implantable electronics.

A Na–IrOx(OH)y cell using body fluid as the electrolyte demonstrates large charge storage capacity and long lifetime.