A Zwitterionic Polyurethane Nanoporous Device with Low Foreign-Body Response for Islet Encapsulation

Encapsulation of insulin-producing cells is a promising strategy for treatment of type 1 diabetes. However, engineering an encapsulation device that is both safe (i.e., no cell escape and no breakage) and functional (i.e., low foreign-body response (FBR) and high mass transfer) remains a challenge. Here, a family of zwitterionic polyurethanes (ZPU) with sulfobetaine groups in the polymer backbone is developed, which are fabricated into encapsulation devices with tunable nanoporous structures via electrospinning. The ZPU encapsulation device is hydrophilic and fouling-resistant, exhibits robust mechanical properties, and prevents cell escape while still allowing efficient mass transfer. The ZPU device also induces a much lower FBR or cellular overgrowth upon intraperitoneal implantation in C57BL/6 mice for up to 6 months compared to devices made of similar polyurethane without the zwitterionic modification. The therapeutic potential of the ZPU device is shown for islet encapsulation and diabetes correction in mice for ≈3 months is demonstrated. As a proof of concept, the scalability and retrievability of the ZPU device in pigs and dogs are further demonstrated. Collectively, these attributes make ZPU devices attractive candidates for cell encapsulation therapies.

A Self-Healable and Recyclable Zwitterionic Polyurethane Based on Dynamic Ionic Interactions

Polyurethanes with self-healing and reprocessing capabilities are promising in eco-friendly applications. Here, a self-healable and recyclable zwitterionic polyurethane (ZPU) was developed by introducing ionic bonds between protonated ammonium groups and sulfonic acid moieties. The structure of the synthesized ZPU was characterized by FTIR and XPS. The thermal, mechanical, self-healing and recyclable properties of ZPU were also investigated in detail. Compared with cationic polyurethane (CPU), ZPU shows similar thermal stability. The physical cross-linking network formed between zwitterion groups can dissipate strain energy as a weak dynamic bond, endowing ZPU with outstanding mechanical and elastic recovery properties, including the high tensile strength of 7.38 MPa, high elongation at a break of 980%, and fast elastic recovery ability. Additionally, ZPU exhibits a healing efficiency of over 93% at 50 °C for 1.5 h as a result of the dynamic reconstruction of reversible ionic bonds. Furthermore, ZPU can be well reprocessed by solution casting and hot-pressing with a recovery efficiency above 88%. The excellent mechanical properties, fast repairing capability, and good recyclability not only enable polyurethane with a promising application in protective coatings for textiles and paints but also make it a superior candidate as stretchable substrates for wearable electronic devices and strain sensors.

Functional Zwitterionic Polyurethanes: State-of-the-Art Review

Recent advancements in bioengineering and medical devices have been greatly influenced and dominated by synthetic polymers, particularly polyurethanes (PUs). PUs offer customizable mechanical properties and long-term stability, but their inherent hydrophobic nature poses challenges in practically biological application processes, such as interface high friction, strong protein adsorption, and thrombosis. To address these issues, surface modifications of PUs for generating functionally hydrophilic layers have received widespread attention, but the durability of generated surface functionality is poor due to irreversible mechanical wear or biodegradation. As a result, numerous researchers have investigated bulk modification techniques to incorporate zwitterionic polymers or groups onto the main or side chains of PUs, thereby improving their hydrophilicity and biocompatibility. This comprehensive review presents an extensive overview of notable zwitterionic PUs (ZPUs), including those based on phosphorylcholine, sulfobetaine, and carboxybetaine. The review explores their wide range of biomedical applications, from blood-contacting devices to antibacterial coatings, fouling-resistant marine coatings, separation membranes, lubricated surfaces, and shape memory and self-healing materials. Lastly, the review summarizes the challenges and future prospects of ZPUs in biological applications.