|Abstract:||Hyperbranched polyglycerols (HPGs) are a versatile and biocompatible class of polymers that have garnered considerable attention within the scientific community, because of their facile synthesis and chemical adaptability. HPGs are used in a number of areas of research, including live cell encapsulation, cell surface decoration, and antifouling coatings. The wide range of uses exemplify their modularity and utility. Herein, we report two distinct amphiphilic HPG materials designed for applications in nanomedicine and industry.
Theranostic agents have the potential to provide solutions for the detection, targeting and treatment of cancer and cardiovascular disease, two of the most prevalent medical conditions of developed nations. These agents have been produced from polymers, nanoparticles, and vesicles that are conjugated with small molecules and biomacromolecules to gain specify selectivity and function.
Harnessing the adaptability of HPGs, an amphiphilic material with a Janus architecture was generated for the assembly of superparamagnetic iron oxide nanoparticle (SPION) clusters to serve as MRI contrast agents. The Janus HPGs (HPG-R) were synthesized by initiation of ring-opening multi-branching polymerization (ROMBP) of glycidol using resorcinarene cavitand. The resorcinarene, a cyclic macrocycle of resorcinol, has eight phenolic hydroxyls on one side and four aliphatic “feet” in the opposite side, providing a hydrophobic base for HPG-R. Using HPG-R as an emulsifying agent, SPION clusters with diameters between 89 - 96 nm were formed, imaged via transmission electron microscopy (TEM), and their T2 relaxivities (r2) were measured. The SPION clusters assembled with HPG-R had r2 = 525 - 595 mM-1s-1 and were comparable to previously reported SPION clusters of this size.
Throughout industry, surface active agents, also known as surfactants, are the most multipurpose chemical substance. These additives serve to stabilize the interface of mixtures with incompatible properties in detergents, coatings, cosmetics, and medical formulations. Nonionic surfactants are often used in aqueous rich mixtures because they tolerate the presence of metal ions and variations in pH but are sensitive to high temperature and salinity. The surfactant properties of nonionic amphiphilic HPGs prepared with hydrophobic initiators of varying size and structure were investigated. The cloud points for all HPG surfactants were found to be >80 °C in deionized water with >1 wt% NaCl. The HPG surfactants with hydrophiliclipophilic balance (HLB) values between 16-18 were found to form stable octanol/water (o/w) emulsions within a 24 h period. Several surface properties, including critical micelle concentration (CMC), efficiency of surface tension reduction (pC20), effectiveness of surface tension reduction (γCMC), surface excess concentration at the CMC (Γmax), minimum area/molecule at the interface (Amin), and the CMC/C20 ratio of all the HPG surfactants were measured in deionized water at 22.6 °C. In general, increasing HPG size was marked by an increase in minimum surface area per molecule (Amin) at the aqueous liquid/air interface. This increase in size also led to lower CMC and greater pC20 values in the Tergitol 15-S-7 series of surfactants.