Reducing Passive Drug Diffusion from Electrophoretic Drug Delivery Devices through Co-Ion Engineering.

Implantable electrophoretic drug delivery devices have shown promise for applications ranging from treating pathologies such as epilepsy and cancer to regulating plant physiology. Upon applying a voltage, the devices electrophoretically transport charged drug molecules across an ion-conducting membrane out to the local implanted area. This solvent-flow-free "dry" delivery enables controlled drug release with minimal pressure increase at the outlet. However, a major challenge these devices face is limiting drug leakage in their idle state. Here, a method of reducing passive drug leakage through the choice of the drug co-ion is presented. By switching acetylcholine's associated co-ion from chloride to carboxylate co-ions as well as sulfopropyl acrylate-based polyanions, steady-state drug leakage rate is reduced up to sevenfold with minimal effect on the active drug delivery rate. Numerical simulations further illustrate the potential of this method and offer guidance for new material systems to suppress passive drug leakage in electrophoretic drug delivery devices.

Design of Polymeric Corrosion Inhibitors Based on Ionic Coumarate Groups.

Efficient, environmentally friendly organic corrosion inhibitors are being sought to alleviate the financial loss caused by corrosion degradation of mild steel materials. Here, we show the synthesis and characterization of monomeric ionic coumarate corrosion inhibitors and their integration into polymeric acrylic UV coatings. For this purpose, we investigated the effect of including the coumarate corrosion inhibitors into the acrylic UV coating by three different means. The corrosion inhibitors could be added as a standalone ionic liquid additive, or they can be ionically attached or covalently attached to the acrylic polymer network. To achieve this, two methacrylic monomers and one nonpolymerizable ionic coumarate compound were synthesized. The anticorrosion properties of the three coumarate compounds when added to a chloride aqueous solution were investigated by various techniques. Next, the three ionic coumarate compounds were integrated into an acrylic UV polymer composition. Here, the UV coating, which shows the best anticorrosion performance, was the one where the coumarate group is attached covalently or ionically to the polymer. The UV coating, which included the coumarate compound as a nonreactive additive, presented leaching problems from the coating, limiting its anticorrosion effect. The work herein shows that the development of polymeric corrosion inhibitors that combine the barrier properties of the polymer coating and the anticorrosive identity of the organic inhibitor is a powerful strategy to prevent corrosion.

Cation Effect in the Corrosion Inhibition Properties of Coumarate Ionic Liquids and Acrylic UV-Coatings.

Chromate free corrosion inhibitors are searched for to mitigate the economic loss caused by mid-steel corrosion. Here, we show metal-free organic inhibitors having free coumarate anions that can be used either as direct corrosion inhibitors or incorporated into a polymer coating obtained by UV-curing. Four different ionic liquid monomers and polymer coatings with hexoxycoumarate anion and different polymerizable counter cations were investigated. Potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analyses have verified their corrosion inhibition performance on a mild steel AS1020 surface. In the case of the coumarate ionic liquid monomers, the most promising inhibitor is the one coupled with the ammonium cation, showing an inhibition efficiency of 99.1% in solution followed by the imidazolium, pyridinium, and anilinium. Next, the ionic liquid monomers were covalently integrated into an acrylic polymer coating by UV-photopolymerization. In this case, the barrier effect of the polymer coating is combined with the corrosion inhibitor effect of the pendant coumarate anion. Here, the best polymer coatings are those containing 20% imidazolium and pyridinium cations, presenting a greater impedance in the EIS (Electrochemical Impedance Spectroscopy) measurements and less evidence of corrosion in the scribe tests. This article shows that the cationic moiety of coumarate based ionic liquids and poly(ionic liquid)s has a significant effect on their excellent corrosion inhibition properties for a mild steel surface exposed to aqueous chloride solutions.

Ionic Hydrogel for Accelerated Dopamine Delivery via Retrodialysis.

Local drug delivery directly to the source of a given pathology using retrodialysis is a promising approach to treating otherwise untreatable diseases. As the primary material component in retrodialysis, the semipermeable membrane represents a critical point for innovation. This work presents a new ionic hydrogel based on polyethylene glycol and acrylate with dopamine counterions. The ionic hydrogel membrane is shown to be a promising material for controlled diffusive delivery of dopamine. The ionic nature of the membrane accelerates uptake of cationic species compared to a nonionic membrane of otherwise similar composition. It is demonstrated that the increased uptake of cations can be exploited to confer an accelerated transport of cationic species between reservoirs as is desired in retrodialysis applications. This effect is shown to enable nearly 10-fold increases in drug delivery rates from low concentration solutions. The processability of the membrane is found to allow for integration with microfabricated devices which will in turn accelerate adaptation into both existing and emerging device modalities. It is anticipated that a similar materials design approach may be broadly applied to a variety of cationic and anionic compounds for drug delivery applications ranging from neurological disorders to cancer.