Incorporation of a Photosensitizer Core within Hyperbranched Polyether Polyols: Effect of the Branched Shell on the Core Properties

End-Chain Fluorescent Highly Branched Poly(l-lactide)s: Synthesis, Architecture-Dependence, and Fluorescent Visible Paclitaxel-Loaded Microspheres

A facile method in combination of "grafting from" and "end-functionalization" was developed for the synthesis of fluorescent highly branched poly(l-lactide)s (PLLA-COU) via ring opening polymerization (ROP) and esterification end-capping. These resulting PLLA-COU with four kinds of architectures, including linear, star, linear-comb, and star-comb structures, were subjected to characterization and application as fluorescent visible paclitaxel-loaded microspheres. The mutual effects of architecture and end-groups on thermal and fluorescence properties, enzymatic degradation, and drug release behaviors were focused. Contrast to linear and star PLLA-COU, two comb-shaped analogues demonstrated higher fluorescence quantum yield, faster drug release, and lower enzymatic degradation rate. All the fluorescent microspheres could maintain fluorescence traceability. The fluorescent PLLA-COU displayed negligible toxicity and good biocompatibility. This work highlights that the fluorescent highly branched poly(l-lactide)s are properties-tailored and used as fluorescent visible drug delivery systems (DDS) for potential theranostic applications.

Hyperbranched polyglycerols: from the controlled synthesis of biocompatible polyether polyols to multipurpose applications

Dendritic macromolecules with random branch-on-branch topology, termed hyperbranched polymers in the late 1980s, have a decided advantage over symmetrical dendrimers by virtue of typically being accessible in a one-step synthesis. Saving this synthetic effort once had an unfortunate consequence, though: hyperbranching polymerization used to result in a broad distribution of molecular weights (that is, very high polydispersities, often M(w)/M(n) > 5). By contrast, a typical dendrimer synthesis yields a single molecule (in other words, M(w)/M(n) = 1.0), albeit by a labor-intensive, multistep process. But 10 years ago, Sunder and colleagues reported the controlled synthesis of well-defined hyperbranched polyglycerol (PG) via ring-opening multibranching polymerization (ROMBP) of glycidol. Since then, hyperbranched and polyfunctional polyethers with controlled molar mass and low polydispersities (M(w)/M(n) = 1.2-1.9) have been prepared, through various monomer addition protocols, by ROMBP. In this Account, we review the progress in the preparation and application of these uniquely versatile polyether polyols over the past decade. Hyperbranched PGs combine several remarkable features, including a highly flexible aliphatic polyether backbone, multiple hydrophilic groups, and excellent biocompatibility. Within the past decade, intense efforts have been directed at the optimization of synthetic procedures affording PG homo- and copolymers with different molecular weight characteristics and topology. Fundamental parameters of hyperbranched polymers include molar mass, polydispersity, degree of branching, and end-group functionality. Selected approaches for optimizing and tailoring these characteristics are presented and classified with respect to their application potential. Specific functionalization in the core and at the periphery of hyperbranched PG has been pursued to meet the growing demand for novel specialty materials in academia and industry. A variety of fascinating synthetic approaches now provide access to well-defined, complex macromolecular architectures based on polyether polyols with low polydispersity. For instance, a variety of linear-hyperbranched block copolymers has been reported. The inherent attributes of PG-based materials are useful for a number of individual implementation concepts, such as drug encapsulation or surface modification. The excellent biocompatibility of PG has also led to rapidly growing significance in biomedical applications, for example, bioconjugation with peptides, as well as surface attachment for the creation of protein-resistant surfaces.