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Coacervation of poly(propylene oxide) and tannic acid, driven by hydrogen bonding, renders a tacky viscous material that provides an underwater adhesion strength of ∼350-550 kPa on aluminum substrates and also can bond other wet surfaces such as glass, metal, plastic, and porcelain. A curing functionality is achieved by designing a two-component system, using epoxidized poly(propylene oxide)/tannic acid coacervate as part A and amine-terminated poly(propylene oxide) as part B. Aside from underwater bonding, this adhesive can cure underwater through amine-epoxide reactions providing a commercially competitive and waterproof bonding.

In this study, dopamine-assisted deposition combined with layer-by-layer assembly was investigated as an efficient method for preparing coatings with tunable thickness, roughness, and functional properties. By this method, one can first benefit from the versatile chemistry of dopamine allowing the co-deposition of various functional materials, for example, polymers, ions, and nanoparticles, within the coating. Moreover, the layer-by-layer approach allows tuning the coating thickness and surface roughness, as well as varying the chemical composition of the coating in the vertical direction. Herein, we demonstrated the benefits of using this method in fabricating both single- and multi-component coatings.

The biggest challenge in oral delivery of anti-inflammatory drugs such as 5-aminosalicylic acid (5-ASA) is to (i) prevent rapid absorption in the small intestine and (ii) achieve localized release at the site of inflammation in the lower gut, i.e., the colon. Here, we present an advanced biopolymeric coating comprising of tannic-acid-functionalized zein protein to provide a sustained, colon-targeted release profile for 5-ASA and enhance the mucoadhesion of the dosage form via a mussel-inspired mechanism. To enable localized delivery and provide high local concentration, 5-ASA is loaded into the microfabricated drug carriers (microcontainers) and sealed with the developed coating. The functionality and drug release profile of the coating are characterized and optimized in vitro, showing great tunability, scalability, and stability toward proteases. Further, ex vivo experiments demonstrate that the tannic acid functionalization can significantly enhance the mucoadhesion of the coating, which is followed up by in vivo investigations on the intestinal retention, and pharmacokinetic evaluation of the 5-ASA delivery system. Results indicate that the developed coating can provide prolonged colonic delivery of 5-ASA. Therefore, the here-developed biodegradable coating can be an eco-friendly substitute to the state-of-the-art commercial counterparts for targeted delivery of 5-ASA and other small molecule drugs.

We report a facile and versatile approach to fabricate polyelectrolyte multilayer (PEM) films with a chemically modifiable outer surface. A PEM film was prepared by layer-by-layer assembly of poly (2-aminoethyl methacrylate) (PAMA) and polymethacrylic acid (PMAA), terminated with a partially tert-butyloxycarbonyl (Boc)-protected random copolymer (PAMA-co-PBocAMA) as the final layer. The obtained PEM film was then cross-linked and the free amino groups in the PEM film were quenched using EDC/NHS chemistry. The outer layer of the film was then treated via a deprotection reaction, affording free amino groups selectively located at the film surface. As a proof of concept study, these functional groups were used to modify the film surface with two model hydrophilic and hydrophobic compounds, which tuned the wettability of the PEM.

Polyelectrolyte brushes have received extensive attention due to their swelling behavior in aqueous solutions, which is a result of their ionic nature and nonelectrostatic (polymer-polymer and polymer-solvent) interactions. While the nonelectrostatic contributions are typically assumed to be negligible compared to the ion osmotic pressure, we present herein a systematic investigation of how the nonelectrostatic interactions dramatically affect the swelling behavior of polyelectrolyte brushes. Using a modular synthesis procedure, polyelectrolyte brushes with similar chain lengths, grafting densities, and charge densities but with various side chains were synthesized. The swelling behaviors of the brushes were then thoroughly investigated as a function of grafting density and ionic strength using ellipsometry. A theoretical mean-field approach was also developed to quantify the contributions of the ion osmotic and nonelectrostatic effects. Accordingly, it was both experimentally and theoretically demonstrated how fundamentally different swelling behaviors can exist depending on the relative contributions of ion osmotic and nonelectrostatic effects. This new insight reveals new opportunities for applications of polyelectrolyte brushes based on their tunable hydrophobicity and provides new ideas for fundamental investigations of these systems.

Bio-inspired polydopamine coatings offer vast possibilities for surface modification of materials. The thickness of such nanometric coatings is usually estimated based on ellipsometry measurements. However, the complex light-absorbing nature of polydopamine is often overlooked when analyzing such data, which can result in inaccurate estimations of the coating thickness as well as the optical properties. In this study, we prepared and characterized three polydopamine coatings where the film thickness and surface roughness are systematically varied. For each case, we developed suitable optical models and showed how an inappropriate optical model can provide inaccurate estimates of the coating properties. AFM height profiles were obtained from scratched areas of each sample to verify the thickness values estimated by ellipsometry. The results confirm that polydopamine coatings, depending on the oxidation conditions, can possess different structural and optical properties, and thus require unique optical models for the ellipsometry analysis.