The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a “polyether universe” may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.

The number of patients suffering from allergic asthma and rhinoconjunctivitis has increased dramatically within the last decades. Allergen‐specific immunotherapy (AIT) is the only available cause‐oriented therapy so far. AIT reduces symptoms, but has also a disease‐modifying effect. Disadvantages are a long‐lasting procedure, and in a few cases potential systemic adverse reactions. Encapsulation of allergens or DNA vaccines into nanostructures may provide advantages compared to the conventional AIT with noncapsulated allergen extracts: The protein/DNA molecule can be protected from degradation, higher local concentrations and targeted delivery to the site of action appear possible, and most importantly, recognition of encapsulated allergen by the immune system, especially by IgE antibodies, is prevented. AIT with nanoparticles (NPs) may offer a safer and potentially more efficient way of treatment for allergic diseases. In this review, we summarize the use of biodegradable NPs consisting of synthetic or natural polymers, liposomes, and virus‐like particles as well as nonbiodegradable NPs like dendrimers, and carbon‐ or metal‐based NPs for AIT. More or less successful applications of these NPs in prophylactic as well as therapeutic vaccination approaches in rodents or other animals as well as first human clinical trials are discussed in detail.

Biomimetic materials have been gaining increasing importance for use as bone biomaterials, because they may provide regenerative alternatives for the use of autologous tissues for bone regeneration. We demonstrate a promising alternative for the use of biomimetic materials based on a biodegradable PEG hydrogel loaded with vaterite nanoparticles as mineral storage. Vaterite, the least stable CaCO₃ polymorph, is stable enough to ensure the presence of a potential ion buffer for bone regeneration, but still has sufficient reactivity for the transformation from CaCO₃ to hydroxyapatite (HA). A combination of powder X-ray diffraction (PXRD), electron microscopy, and Fourier-transform infrared (FT-IR) and Raman spectroscopy showed the transformation of vaterite nanoparticles incorporated in a PEG-acetal-DMA hydrogel to hydroxycarbonate apatite (HCA) crystals upon incubation in simulated body fluid at human body temperature within several hours. The transformation in the PEG-acetal-DMA hydrogel scaffold in simulated body fluid or phosphate saline buffer proceeded significantly faster than for free vaterite. The vaterite-loaded hydrogels were free of endotoxin and did not exhibit an inflammatory effect on endothelial cells. These compounds may have prospects for future applications in the treatment of bone defects and bone degenerative diseases.