Atomically thin transition-metal dichalcogenides (TMDs) have attracted considerable interest because of their unique combination of properties, including photoluminescence, high lubricity, flexibility, and catalytic activity. These unique properties suggest future uses for TMDs in medical applications such as orthodontics, endoscopy, and optogenetics. However, few studies thus far have investigated the biocompatibility of mechanically exfoliated and chemical vapor deposition (CVD)grown pristine two-dimensional TMDs. Here, we evaluate pristine molybdenum disulfide (MoS 2 ) and tungsten disulfide (WS 2 ) in a series of biocompatibility tests, including live−dead cell assays, reactive oxygen species (ROS) generation assays, and direct assessment of cellular morphology of TMD-exposed human epithelial kidney cells (HEK293f). Genotoxicity and genetic mutagenesis were also evaluated for these materials via the Ames Fluctuation test with the bacterial strain S. typhimurium TA100. Scanning electron microscopy of cultured HEK293f cells in direct contact with MoS 2 and WS 2 showed no impact on cell morphology. HEK293f cell viability, evaluated by both live−dead fluorescence labeling to detect acute toxicity and ROS to monitor for apoptosis, was unaffected by these materials. Exposure of bacterial cells to these TMDs failed to generate genetic mutation. Together, these findings demonstrate that neither mechanically exfoliated nor CVD-grown TMDs are deleterious to cellular viability or induce genetic defects. Thus, these TMDs appear biocompatible for future application in medical devices.

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Reliable cerebrospinal fluid (CSF) draining methods are needed to treat hydrocephalus, a chronic debilitating brain disorder. Current shunt implant treatments are characterized by high failure rates that are to some extent attributed to their length and multiple components. The designed valve, made of hydrogel, steers away from such protracted schemes and intends to provide a direct substitute for faulty arachnoid granulations, the brain's natural CSF draining valves, and restore CSF draining operations within the cranium. The valve relies on innate hydrogel swelling phenomena to strengthen reverse flow sealing at idle and negative pressures thereby alleviating common valve failure mechanisms. In vitro measurements display operation in range of natural CSF draining (cracking pressure, PT ~ 1-110 mmH2O and outflow hydraulic resistance, Rh ~ 24-152 mmH2O/mL/min), with negligible reverse flow leakage (flow, QO > -10 µL/min). Hydrodynamic measurements and over-time tests under physically relevant conditions further demonstrate the valve's operationally-reproducible properties and strengthen its validity for use as a chronic implant.

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