Hydrogels have been widely used for therapeutic delivery applications due to their tunability and biocompatibility, although delivery of small molecules is difficult due to high burst release and rapid diffusion from the device. Nanosilicate clays (nanoclays) have shown the adsorption potential of small molecules, offering a lever to prolong the release kinetics of hydrogel delivery devices. However, further characterization of small molecule–nanoclay interactions and their effect on molecule release is needed to allow for the custom design of tunable nanocomposite hydrogel delivery devices. Here, we have characterized the adsorption of small molecules onto three nanoclays, Laponite, montmorillonite, and halloysite, and monitored their release in various conditions. The layered structures of Laponite and montmorillonite led to cationic exchange of the small molecules into the interlayer space, whereas the small molecules were adsorbed onto the surface of the tubular halloysite. The addition of nanoclays to polyethylene glycol (PEG) hydrogels significantly slowed the release of small molecules, especially from Laponite (500-fold decrease) and montmorillonite (∼3000-fold decrease) composite gels. Cationic small molecules were shown to be released significantly slower from nanocomposite hydrogels than anionic ones. The incubation time of small molecules with nanoclays prior to hydrogel encapsulation also played a key role in determining their release rate, with montmorillonite showing near-immediate adsorption while halloysite exhibited a higher dependence on incubation time due to slower adsorption kinetics. Release buffer salt concentration and pH were shown to affect release kinetics due to modulation of nanoclay–small molecule interactions. These results show the potential for formation of a highly tunable nanocomposite hydrogel delivery device for a greatly prolonged release of small molecules compared to traditional hydrogels.

A cobalt (II) oxide/carboxylic acid functionalized multiwalled carbon nanotube (CoO/COOH-MWNT) composite was fabricated for the biochemical detection of dopamine (DA). CoO particles were tethered to COOH-MWNTs by sonication. The current response versus different concentration was measured using cyclic voltammetry. Various parameters, including sonication time, pH, and loading were varied for the best current response. The composite with optimum current response was formed using a 30-min sonication time, at pH 5.0 and a 0.89 µg/mm2 loading onto the glassy carbon electrode surface. Good sensitivity with a limit of detection of 0.61 ± 0.03 μM, and dynamic range of 10–100 µM for DA is shown, applicable for neuroblastoma screening. The sensor was selective against ascorbic and uric acids.

Microcomputed tomography is an important technique for distinguishing the vascular network from tissues with similar X-ray attenuation. Here, we describe a composite of barium sulfate (BaSO4) nanoparticles, calcium carbonate (CaCO3) nanoparticles, and alginate that provides improved performance over microscale BaSO4 particles, which are currently used clinically as X-ray contrast agents. BaSO4 and CaCO3 nanoparticles were synthesized using a polyol method with tetraethylene glycol as solvent and capping agent. The nanoparticles show good colloidal stability in aqueous solutions. A deliverable nanocomposite gel contrast agent was produced by encapsulation of the BaSO4 and CaCO3 nanoparticles in an alginate gel matrix. The gelation time was controlled by addition of d-(+)-gluconic acid δ-lactone, which controls the rate of dissolution of the CaCO3 nanoparticles that produce Ca2+ which cross-links the gel. Rapid cross-linking of the gel by Ba2+ was minimized by producing BaSO4 nanoparticles with an excess of surface sulfate. The resulting BaSO4–CaCO3 nanoparticle alginate gel mechanical properties were characterized, including the gel storage modulus, peak stress and elastic modulus, and radiodensity. The resulting nanocomposite has good viscosity control and good final gel stiffness. The nanocomposite has gelation times between 30 and 35 min, adequate for full body perfusion. This is the first nanoscale composite of a radiopaque metal salt to be developed in combination with an alginate hydrogel and designed for medical perfusion and vascular imaging applications.

A method is described for activation of the reaction of room temperature water with micron-scale aluminum particles (μAl) by the addition of poly(epoxyhexane)-capped aluminum nanoparticles (Al NPs). By themselves, Al NPs react vigorously and completely with water at ambient temperatures to produce H2. While pure μAl particles are unreactive toward water, mixtures of the μAl particles comprising 10 to 90% (by mass) of Al NPs, demonstrated appreciable hydrolytic activation. This activation is attributed to the reaction of the Al NPs present with water to produce a basic solution. Speciation modelling, pH studies, and powder X-ray diffraction analysis of the hydrolysis product confirm that the pH change is the key driver for the activation of μAl rather than residual heat from the exothermicity of Al NP hydrolysis. A mechanism is proposed by which the nonreactive aluminum oxide layer of the μAl is eroded under basic conditions. Mixtures 10% by mass of Al NPs can be used to produce the optimal quantity of H2.

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