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Cerium oxide nanoparticles (or nanoceria) have demonstrated great potential as antioxidants in various cell culture models. Despite such promise for reducing reactive oxygen species and ability for surface functionalization, nanoceria has not been extensively studied for cancer applications to date. Herein, we engineered the surface of nanoceria with dextran and observed its activity in the presence bone cancer cells (osteosarcoma cells) at different pH values resembling the cancerous and non-cancerous environment. We found that dextran coated nanoceria was much more effective at killing bone cancer cells at slightly acidic (pH=6) compared to physiological and basic pH values (pH=7 and pH=9). In contrast, minimal toxicity was observed for healthy (noncancerous) bone cells when cultured with nanoceria at pH=6 after one day of treatment in the concentration range of 10-1000 µg/mL. Although healthy bone cancer cell viability decreased after treatment with high ceria nanoparticle concentrations (250-1000 µg/mL) for longer time periods at pH=6 (3 days and 5 days), approximately 2-3 fold higher healthy bone cell viabilities were observed compared to osteosarcoma cell viability at similar conditions. Very low toxicity was observed for healthy osteoblasts cultured with nanoceria for any concentration at any time period at pH=7. In this manner, this study provides the first evidence that nanoceria can be a promising nanoparticle for treating bone cancer without adversely affecting healthy bone cells and, thus, deserves further investigation.

Nanomeshed forms of metal have emerged as a promising biocompatible electrode material for future soft bioelectronics. However, metal/electrolyte interfaces are intrinsically capacitive, severely limiting their electrochemical performance, especially for scaled electrodes, which are essential for highresolution brain mapping. Here, an innovative bilayer nanomesh approach is demonstrated to address this limitation while preserving the nanomesh advantage. Electroplating low-impedance coatings on a gold nanomesh template achieves an impedance < 30 kΩ at 1 kHz and a charge injection limit of 1 mC cm −2 for 80 × 80 µm 2 microelectrodes, a 4.3× and 12.8× improvement over uncoated electrodes, respectively, while maintaining a transparency of ≈70% at 550 nm. Systematic characterization of transmittance, impedance, charge injection limits, cyclic charge injection, and light-induced artifacts reveal an encouraging performance of the bilayer nanomesh microelectrodes. The bilayer nanomesh approach presented here is expected to enable next-generation large-scale transparent bioelectronics with broad utility in biology.

Since implants often fail due to infection and uncontrolled inflammatory responses, we designed an in vitro study to investigate the antibacterial and anti-inflammatory properties of titanium dioxide nanotubes (TNTs) incorporated with selenium nanoparticles (SeNPs). Selenium incorporation was achieved by the reaction of sodium selenite (Na2SeO3) with glutathione (GSH) under a vacuum in the presence of TNTs. Two types of bacteria and macrophages were cultured on the samples to determine their respective antibacterial and anti-inflammatory properties. The results showed that the TNT samples incorporating SeNPs (TNT-Se) inhibited the growth of Escherichia coli and Staphylococcus aureus compared to unmodified TNTs, albeit the SeNP concentration still needs to be optimized for maximal effect. At their maximum effect, the TNT-Se samples reduced the density of E. coli by 94.6% and of S. aureus by 89.6% compared to titanium controls. To investigate the underlying mechanism of this effect, the expression of six E. coli genes were tracked using qRT-PCR. Results indicated that SeNPs weakened E. coli membranes (ompA and ompF were down-regulated), decreased the function of adhesion-mediating proteins (csgA and csgG were progressively down-regulated with increasing SeNP content), and induced the production of damaging reactive oxygen species (ahpF was up-regulated). Moreover, TNT-Se samples inhibited the proliferation of macrophages, indicating that they can be used to control the inflammatory response and even prevent chronic inflammation, a condition that often leads to implant failure. In conclusion, we demonstrated that SeNP-TNTs display antibacterial and anti-inflammatory properties that are promising for improving the performance of titanium-based implants for numerous orthopedic and dental applications.

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