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PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring‐opening copolymerization of ethylene oxide with 3,4‐epoxy‐1‐butene (EPB) and subsequent modification to introduce acid‐degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross‐linking. Copolymers with different molar ratios of EPB, molecular weights (M n) up to 10 000 g mol−1 and narrow dispersities (Đ, Responsive gels: P(EG‐co‐isoEPB)MA, a PEG copolymer with acidic degradability under physiologically relevant pH is employed for hydrogels. The attached methacrylate units enable radical cross‐linking to form protein‐loaded hydrogels. Both the P(EG‐co‐isoEPB)MA copolymer as well as the respective hydrogels show rapid and tailorable hydrolysis at physiologically relevant pH (pH 5–6), despite excellent storage stability at neutral pH (pH 7.4).

The generation of hydrogel droplets using droplet microfluidics has emerged as a powerful tool with many applications in biology and medicine. Here, a microfluidic system to control the position of particles (beads or astrocyte cells) in hydrogel droplets using bulk acoustic standing waves is presented. The chip consisted of a droplet generator and a 380 µm wide acoustic focusing channel. Droplets comprising hydrogel precursor solution (polyethylene glycol tetraacrylate or a combination of polyethylene glycol tetraacrylate and gelatine methacrylate), photoinitiator and particles were generated. The droplets passed along the acoustic focusing channel where a half wavelength acoustic standing wave field was generated, and the particles were focused to the centre line of the droplets (i.e. the pressure nodal line) by the acoustic force. The droplets were cross-linked by exposure to UV-light, freezing the particles in their positions. With the acoustics applied, 89 ± 19% of the particles (polystyrene beads, 10 µm diameter) were positioned in an area ± 10% from the centre line. As proof-of-principle for biological particles, astrocytes were focused in hydrogel droplets using the same principle. The viability of the astrocytes after 7 days in culture was 72 ± 22% when exposed to the acoustic focusing compared with 70 ± 19% for samples not exposed to the acoustic focusing. This technology provides a platform to control the spatial position of bioparticles in hydrogel droplets, and opens up for the generation of more complex biological hydrogel structures.

The generation of hydrogel droplets using droplet microfluidics has emerged as a powerful tool with many applications in biology and medicine. Here, a microfluidic system to control the position of particles (beads or astrocyte cells) in hydrogel droplets using bulk acoustic standing waves is presented. The chip consisted of a droplet generator and a 380 µm wide acoustic focusing channel. Droplets comprising hydrogel precursor solution (polyethylene glycol tetraacrylate or a combination of polyethylene glycol tetraacrylate and gelatine methacrylate), photoinitiator and particles were generated. The droplets passed along the acoustic focusing channel where a half wavelength acoustic standing wave field was generated, and the particles were focused to the centre line of the droplets (i.e. the pressure nodal line) by the acoustic force. The droplets were cross-linked by exposure to UV-light, freezing the particles in their positions. With the acoustics applied, 89 ± 19% of the particles (polystyrene beads, 10 µm diameter) were positioned in an area ± 10% from the centre line. As proof-of-principle for biological particles, astrocytes were focused in hydrogel droplets using the same principle. The viability of the astrocytes after 7 days in culture was 72 ± 22% when exposed to the acoustic focusing compared with 70 ± 19% for samples not exposed to the acoustic focusing. This technology provides a platform to control the spatial position of bioparticles in hydrogel droplets, and opens up for the generation of more complex biological hydrogel structures. These authors contributed equally: Anna Fornell and Hannah Pohlit

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.

This review article describes microfabrication techniques to define chemical, mechanical and structural patterns in hydrogels and how these can be used to prepare in vivo like, i.e. biomimetic, cell culture scaffolds. Hydrogels are attractive materials for 3D cell cultures as they provide ideal culture conditions and they are becoming more prominently used. Single material gels without any modifications do however have their limitation in use and much can be gained by in improving the in vivo resemblance of simple hydrogel cell culture scaffolds. This review article discusses the most commonly used cross-linking strategies used for hydrogel-based culture scaffolds and gives a brief introduction to microfabrication methods that can be used to define chemical, mechanical and structural patterns in hydrogels with micrometre resolution. The review article also describes a selection of literature references using these microfabrication techniques to prepare organ and disease models with controlled cell adhesion, proliferation and migration. It is intended to serve as an introduction to microfabrication of hydrogels and an inspiration for novel interdisciplinary research projects.

We have previously described a promising alternative to conventional synthetic bone biomaterials using vaterite, a metastable CaCO3 polymorph that increases the local Ca2+ concentration in vitro and leads to an oversaturation of phosphate, the primary bone mineral. This stimulates a natural bone-like mineralisation in a short period of time. In this study, sterile and endotoxin-free vaterite particles were synthesised in a nearly quantitative yield. The 500-1,000 nm vaterite particles did not exhibit any cytotoxic effects as measured by MTS, lactate dehydrogenase, or crystal violet assays on the human osteoblast cell line (MG-63) exposed to concentrations up to 500 μg/ml vaterite up to 72 hr. MG-63, primary human osteoblasts or human umbilical vein endothelial cells in the presence of vaterite up to 500 μg/ml for 7 days exhibited typical growth patterns. Endothelial cells exhibited a normal induction of E-selectin after exposure to LPS and MG-63 cells in osteogenic differentiation medium showed an increased expression of alkaline phosphatase compared with the respective control cells without vaterite. MG-63 cultured on a vaterite-containing degradable poly(ethylene glycol)-hydrogel exhibited strong adhesion and proliferation, similar to cells on cell culture plates. Cells did not attach to gels without vaterite. Our results demonstrate that vaterite particles are biocompatible, do not influence cell gene expression, and that vaterite in hydrogels may be able to serve for adhesion of osteoblasts and as a mineral substrate for natural bone formation by osteoblasts. These characteristics make vaterite particles a highly favourable compound for use in bone regeneration applications.

Heterobifunctional poly(ethylene glycol)s (PEGs) are key structures for bioconjugation in the context of the “PEGylation” strategy to enhance blood circulation times of, for example, peptide drugs or “stealth” liposomes. The formation of heterobifunctional PEGs from symmetric PEG diols is challenging because of limited yields of the targeted monofunctional product and difficulties associated with separation steps. On the basis of a detailed comparison of reaction conditions, we have investigated a “polymer desymmetrization” strategy to maximize the yields of monofunctional PEG tosylate. The tosylation reaction in the presence of the heterogeneous catalyst silver oxide and potassium iodide in a specific stoichiometric ratio proved to be highly efficient, resulting in 71–76% yield of monofunctional PEG depending on molecular weight, exceeding the expected value of 50% in a statistical reaction without addition of a catalyst. For characterization as well as for the preparative separation of monotosylated PEG...

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.

In the last decades, the number of allergic patients has increased dramatically. Allergen-specific immunotherapy (SIT) is the only available cause-oriented therapy so far. SIT reduces the allergic symptoms, but also exhibits some disadvantages; that is, it is a long-lasting procedure and severe side effects like anaphylactic shock can occur. In this work, we introduce a method to encapsulate allergens into nanoparticles to avoid severe side effects during SIT. Degradable nanocarriers combine the advantage of providing a physical barrier between the encapsulated cargo and the biological environment as well as responding to certain local stimuli (like pH) to release their cargo. This work introduces a facile strategy for the synthesis of acid-labile poly(ethylene glycol) (PEG)-macromonomers that degrade at pH 5 (physiological pH inside the endolysosome) and can be used for nanocarrier synthesis. The difunctional, water-soluble PEG dimethacrylate (PEG-acetal-DMA) macromonomers with cleavable acetal units were analyzed with 1H NMR, SEC, and MALDI-ToF-MS. Both the allergen and the macromonomers were entrapped inside liposomes as templates, which were produced by dual centrifugation (DAC). Radical polymerization of the methacrylate units inside the liposomes generated allergen-loaded PEG nanocarriers. In vitro studies demonstrated that dendritic cells (DCs) internalize the protein-loaded, nontoxic PEG-nanocarriers. Furthermore, we demonstrate by cellular antigen stimulation tests that the nanocarriers effectively shield the allergen cargo from detection by immunoglobulins on the surface of basophilic leucocytes. Uptake of nanocarriers into DCs does not lead to cell maturation; however, the internalized allergen was capable to induce T cell immune responses.

We have previously described a promising alternative to conventional synthetic bone biomaterials using vaterite, a metastable CaCO

The authors introduce poly(ethylene glycol) (PEG) based macromonomers containing acid-labile ketal moieties as well as terminal methacrylate units that are amenable to radical polymerization. The synthesis of PEGs of different molecular weights (ranging from 2000 to 13 000 g mol-1 with polydispersities

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.

In this work, we present a method to fabricate a hyaluronic acid (HA) hydrogel with spatially controlled cell-adhesion properties based on photo-polymerisation cross-linking and functionalization. The approach utilises the same reaction pathway for both steps meaning that it is user-friendly and allows for adaptation at any stage during the fabrication process. Moreover, the process does not require any additional cross-linkers. The hydrogel is formed by UV-initiated radical addition reaction between acrylamide (Am) groups on the HA backbone. Cell adhesion is modulated by functionalising the adhesion peptide sequence arginine–glycine–aspartate onto the hydrogel surface via radical mediated thiol–ene reaction using the non-reacted Am groups. We show that 10 × 10 µm2 squares could be patterned with sharp features and a good resolution. The smallest area that could be patterned resulting in good cell adhesion was 25 × 25 µm2 squares, showing single-cell adhesion. Mouse brain endothelial cells adhered and remained in culture for up to 7 days on 100 × 100 µm2 square patterns. We see potential for this material combination for future use in novel organ-on-chip models and tissue engineering where the location of the cells is of importance and to further study endothelial cell biology.

Confocal microscopy offers a mean to extract quantitative data on spatially confined subcellular structures. Here, we provide an imaging dataset of confocal z-stacks on endothelial cells spatially confined on lines with different widths, visualizing the nucleus, F-actin, and zonula occludens-1 (ZO-1), as well as the lines. This dataset also includes confocal images of spatially confined endothelial cells challenged with different glucose conditions. We have validated the image quality by established analytical means using the MeasureImageQuality module of the CellProfilerTM software. We envision that this dataset could be used to extract data on both a population and a single cell level, as well as a learning set for the development of new image analysis tools., Measurement(s)nucleus • F-actin • zonula occludens 1Technology Type(s)confocal microscopyFactor Type(s)line width • medium glucose concentrationSample Characteristic - OrganismMus musculus Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.17129021