A Clean and Simple Route to Soft, Biocompatible Nanocapsules via UV-Cross-Linkable Azido-Hyperbranched Polyglycerol

The development of a simple, low-cost, and robust route to soft nanocapsules is an ever-present hurdle and requirement for their promising use in drug encapsulation and delivery. To date, several elegant strategies for nanocapsule formation have emerged. However, some of them fall short of one or several of the requirements including stability, biocompatibility, antifouling, and low cost which ultimately limit their potential impact. Owing to its inherent biocompatibility, low cost, and high functionalization characteristics, hyperbranched polyglycerol (HPG) derivatives may offer a possible solution. Through esterification and azidation of HPG hydroxyl groups, an intriguing UV-cross-linkable HPG-azidomethylbenzoyl ester (denoted HPG-4-N₃-MBE) is yielded. Over short irradiation periods, fairy uniform wholly polymeric HPG nanocapsules with diameters less than 100 nm can be formed which exhibit good stability due to abundant cross-linking primarily though nitrene-nitrene coupling to produce azo linkages rather than potentially reactive azidirine ring linkages. This work demonstrates the simple, low-cost, and robust type of chemistry needed for the practical development of polymer nanocapsule-based drug delivery/encapsulation, waste remediation, and surface antifouling strategies.