Long-term accurate and continuous monitoring of nitrate (NO3 –) concentration in wastewater and groundwater is critical for determining treatment efficiency and tracking contaminant transport. Current nitrate monitoring technologies, including colorimetric, chromatographic, biometric, and electrochemical sensors, are not feasible for continuous monitoring. This study addressed this challenge by modifying NO3 – solid-state ion-selective electrodes (S-ISEs) with poly­(tetrafluoroethylene) (PTFE, (C2F4) n ). The PTFE-loaded S-ISE membrane polymer matrix reduces water layer formation between the membrane and electrode/solid contact, while paradoxically, the even more hydrophobic PTFE-loaded S-ISE membrane prevents bacterial attachment despite the opposite approach of hydrophilic modifications in other antifouling sensor designs. Specifically, an optimal ratio of 5% PTFE in the S-ISE polymer matrix was determined by a series of characterization tests in real wastewater. Five percent of PTFE alleviated biofouling to the sensor surface by enhancing the negative charge (−4.5 to −45.8 mV) and lowering surface roughness (R a: 0.56 ± 0.02 nm). It simultaneously mitigated water layer formation between the membrane and electrode by increasing hydrophobicity (contact angle: 104°) and membrane adhesion and thus minimized the reading (mV) drift in the baseline sensitivity (“data drifting”). Long-term accuracy and durability of 5% PTFE-loaded NO3 – S-ISEs were well demonstrated in real wastewater over 20 days, an improvement over commercial sensor longevity.

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Periprosthetic infections are one of the most serious complications in orthopedic surgeries, and those caused by Staphylococcus aureus (S. aureus) are particularly hard to treat due to their tendency to form biofilms on implants and their notorious ability to invade the surrounding bones. The existing prophylactic local antibiotic deliveries involve excessive drug loading doses that could risk the development of drug resistance strains. Utilizing an oligonucleotide linker sensitive to micrococcal nuclease (MN) cleavage, we previously developed an implant coating capable of releasing covalently tethered vancomycin, triggered by S. aureus-secreted MN, to prevent periprosthetic infections in the mouse intramedullary (IM) canal. To further engineer this exciting platform to meet broader clinical needs, here, we chemically modified the oligonucleotide linker by a combination of 2′-O-methylation and phosphorothioate modification to achieve additional modulation of its stability/sensitivity to MN and the kinetics of MN-triggered on-demand release. We found that when all phosphodiester bonds within the oligonucleotide linker 5′-carboxy-mCmGTTmCmG-3-acrydite, except for the one between TT, were replaced by phosphorothioate, the oligonucleotide (6PS) stability significantly increased and enabled the most sustained release of tethered vancomycin from the coating. By contrast, when only the peripheral phosphodiester bonds at the 5′and 3′-ends were replaced by phosphorothioate, the resulting oligonucleotide (2PS) linker was cleaved by MN more rapidly than that without any PS modifications (0PS). Using a rat femoral canal periprosthetic infection model where 1000 CFU S. aureus was inoculated at the time of IM pin insertion, we showed that the prophylactic implant coating containing either 0PS-or 2PS-modified oligonucleotide linker effectively eradicated the bacteria by enabling the rapid on-demand release of vancomycin. No bacteria were detected from the explanted pins, and no signs of cortical bone changes were detected in these treatment groups throughout the 3 month follow-ups. With an antibiotic tethering dose significantly lower than conventional antibiotic-bearing bone cements, these coatings also exhibited excellent biocompatibility. These chemically modified oligonucleotides could help tailor prophylactic antiinfective coating strategies to meet a range of clinical challenges where the risks for S. aureus prosthetic infections range from transient to long-lasting.

Artificial muscles are soft actuators with the capability of either bending or contraction/elongation subjected to external stimulation. However, there are currently no artificial muscles that can accomplish these actions simultaneously. We found that the single layered, latticed microstructure of onion epidermal cells after acid treatment became elastic and could simultaneously stretch and bend when an electric field was applied. By modulating the magnitude of the voltage, the artificial muscle made of onion epidermal cells would deflect in opposing directions while either contracting or elongating. At voltages of 0–50 V, the artificial muscle elongated and had a maximum deflection of −30 μm; at voltages of 50–1000 V, the artificial muscle contracted and deflected 1.0 mm. The maximum force response is 20 μN at 1000 V.