Interactions of methacryloylated gelatin and heparin modulate physico-chemical properties of hydrogels and release of vascular endothelial growth factor

Osteogenic effect and mechanism of IL-10 in diabetic rat jaw defect mode

OBJECTIVE

The aim of this study was to investigate the effect of IL-10 on the phenotype polarization of macrophages and osteogenesis in diabetes mellitus type 2 (T2DM) rat jaw defects.

METHODS

Lipopolysaccharide (LPS) and interleukin-10 (IL-10) were chosen to induce the polarization of macrophages. In vitro assessment included wound-healing assay, western blotting, and alizarin red staining after co-culture of the bone marrow-derived mesenchymal stem cells (BMSCs) and induced macrophages. For in vivo study, IL-10 was loaded on GelMA-Heparin and applied to bone defects of the alveolar ridge in diabetic rats, while Bio-Oss Collagen, simple GelMA-Heparin, and blank control groups were set for contrast experiment. The mandibles of rats were processed for micro-computed tomography, histology, and immunohistochemistry 1 week and 4 weeks after the operation.

RESULTS

IL-10 induced expression of arginase 1, TGF-β1, EGR2, and Mannose Receptor (CD206), whereas LPS induced expression of iNOS, TNF-α, IL-6, CD80. The BMSCs co-cultured with macrophages induced by IL-10 showed increased migration, osteogenic differentiation, and mineralization in vitro. Notably, the IL-10-laden GelMA-Heparin group showed quicker new bone formation and a higher M2/M1 ratio of macrophages in the jawbone defect area compared with the control groups.

CONCLUSIONS

IL-10 can stably induce macrophages to M2 type, thereby influencing BMSCs and improving the osteogenesis of jaw bone defects.

Soft Sub-Structured Multi-Material Biosensor Hydrogels with Enzymes Retained by Plant Viral Scaffolds

An all-soft multi-material combination consisting of a hydrogel based on poly(ethylene glycol) (PEG) coated with spatially defined spots of gelatin methacryloyl (GM) containing selectively addressable viral nanorods is presented, and its basic application as a qualitative biosensor with reporter enzymes displayed on the tobacco mosaic virus (TMV) bioscaffolds within the GM is demonstrated. Biologically inert PEG supports are equipped with GM spots serving as biological matrix for enzymes clustered on TMV particles preventing diffusion out of the gel. For this multi-material combination, i) the PEG-based hydrogel surface is modified to achieve a clear boundary between coated and non-coated regions by introducing either isothiouronium or thiol groups. ii) Cross-linking of the GM spots is studied to achieve anchoring to the hydrogel surface. iii) The enzymes horseradish peroxidase or penicillinase (Pen) are conjugated to TMV and integrated into the GM matrix. In contrast to free enzymes, enzyme-decorated TMVs persist in GM spots and show sustained enzyme activity as evidenced by specific color reaction after 7 days of washing, and for Pen after 22 months after dry storage. Therefore, the integration of enzyme-coupled TMV into hydrogel matrices is a promising and versatile approach to obtaining reusable and analyte-specific sensor components.

Preparation of multifunctional hydrogels with accessible isothiouronium groups via radical cross-linking copolymerization

Hydrogels can be equipped with functional groups for specific purposes. Isothiouronium groups can enhance adsorptivity, or allow coupling of other functional groups through mild reactions after transformation to thiol groups. Here we present a method to prepare multifunctional hydrogels by introducing isothiouronium groups into poly(ethylene glycol) diacrylate (PEGDA) hydrogels, and convert them into thiol-functionalized hydrogels by the reduction of the isothiouronium groups. For this purpose, the amphiphilic monomer 2-(11-(acryloyloxy)-undecyl)isothiouronium bromide (AUITB), containing an isothiouronium group, was synthesized and copolymerized with PEGDA. In this convenient way, it was possible to incorporate up to 3 wt% AUITB into the hydrogels without changing their equilibrium swelling degree. The successful functionalization was demonstrated by surface analysis of the hydrogels with water contact angle measurements and increased isoelectric points of the hydrogel surfaces from 4.5 to 9.0 due to the presence of the isothiouronium groups. The hydrogels showed a suitability as an adsorbent, as exemplified by the pronounced adsorption of the anionic drug diclofenac. The potential of the functionalization for (bio)conjugation reactions was demonstrated by the reduction of isothiouronium groups to thiols and subsequent immobilization of the functional enzyme horseradish peroxidase on the hydrogels. The results show that fully accessible isothiouronium groups can be introduced into radically cross-linked hydrogels.

Gelatin as It Is: History and Modernity

The data concerning the synthesis and physicochemical characteristics of one of the practically important proteins-gelatin, as well as the possibilities of its practical application, are systematized and discussed. When considering the latter, emphasis is placed on the use of gelatin in those areas of science and technology that are associated with the specifics of the spatial/molecular structure of this high-molecular compound, namely, as a binder for the silver halide photographic process, immobilized matrix systems with a nano-level organization of an immobilized substance, matrices for creating pharmaceutical/dosage forms and protein-based nanosystems. It was concluded that the use of this protein is promising in the future.

3D Bioprinting Using Hydrogels: Cell Inks and Tissue Engineering Applications

3D bioprinting is transforming tissue engineering in medicine by providing novel methods that are precise and highly customizable to create biological tissues. The selection of a "cell ink", a printable formulation, is an integral part of adapting 3D bioprinting processes to allow for process optimization and customization related to the target tissue. Bioprinting hydrogels allows for tailorable material, physical, chemical, and biological properties of the cell ink and is suited for biomedical applications. Hydrogel-based cell ink formulations are a promising option for the variety of techniques with which bioprinting can be achieved. In this review, we will examine some of the current hydrogel-based cell inks used in bioprinting, as well as their use in current and proposed future bioprinting methods. We will highlight some of the biological applications and discuss the development of new hydrogels and methods that can incorporate the completed print into the tissue or organ of interest.

Recent Progress on Polysaccharide-Based Hydrogels for Controlled Delivery of Therapeutic Biomolecules

A plethora of applications using polysaccharides have been developed in recent years due to their availability as well as their frequent nontoxicity and biodegradability. These polymers are usually obtained from renewable sources or are byproducts of industrial processes, thus, their use is collaborative in waste management and shows promise for an enhanced sustainable circular economy. Regarding the development of novel delivery systems for biotherapeutics, the potential of polysaccharides is attractive for the previously mentioned properties and also for the possibility of chemical modification of their structures, their ability to form matrixes of diverse architectures and mechanical properties, as well as for their ability to maintain bioactivity following incorporation of the biomolecules into the matrix. Biotherapeutics, such as proteins, growth factors, gene vectors, enzymes, hormones, DNA/RNA, and antibodies are currently in use as major therapeutics in a wide range of pathologies. In the present review, we summarize recent progress in the development of polysaccharide-based hydrogels of diverse nature, alone or in combination with other polymers or drug delivery systems, which have been implemented in the delivery of biotherapeutics in the pharmaceutical and biomedical fields.

The choice of biopolymer is crucial to trigger angiogenesis with vascular endothelial growth factor releasing coatings

Bio-based coatings and release systems for pro-angiogenic growth factors are of interest to overcome insufficient vascularization and bio-integration of implants. This study compares different biopolymer-based coatings on polyethylene terephthalate (PET) membranes in terms of coating homogeneity and stability, coating thickness in the swollen state, endothelial cell adhesion, vascular endothelial growth factor (VEGF) release and pro-angiogenic properties. Coatings consisted of carbodiimide cross-linked gelatin type A (GelA), type B (GelB) or albumin (Alb), and heparin (Hep), or they consisted of radically cross-linked gelatin methacryloyl-acetyl (GM5A5) and heparin methacrylate (HepM5). We prepared films with thicknesses of 8-10 µm and found that all coatings were homogeneous after washing. All gelatin-based coatings enhanced the adhesion of primary human endothelial cells compared to the uncoated membrane. The VEGF release was tunable with the loading concentration and dependent on the isoelectric points and hydrophilicities of the biopolymers used for coating: GelA-Hep showed the highest releases, while releases were indistinguishable for GelB-Hep and Alb-Hep, and lowest for GM5A5-HepM5. Interestingly, not only the amount of VEGF released from the coatings determined whether angiogenesis was induced, but a combination of VEGF release, metabolic activity and adhesion of endothelial cells. VEGF releasing GelA-Hep and GelB-Hep coatings induced angiogenesis in a chorioallantoic membrane assay, so that these coatings should be considered for further in vivo testing.

Myofibroblast activation in synthetic fibrous matrices composed of dextran vinyl sulfone

Mechanical interactions between fibroblasts and their surrounding extracellular matrix (ECM) guide fundamental behaviors such as spreading, migration, and proliferation that underlie disease pathogenesis. The challenges of studying ECM mechanics in vivo have motivated the development of in vitro models of the fibrous ECM in which fibroblasts reside. Natural materials such as collagen hydrogels bear structural and biochemical resemblance to stromal ECM, but mechanistic studies in these settings are often confounded by cell-mediated material degradation and the lack of structural and mechanical tunability. Here, we established a new material system composed of electrospun dextran vinyl sulfone (DexVS) polymeric fibers. These fibrous matrices exhibit mechanical tunability at both the single fiber (80-340 MPa) and bulk matrix (0.77-11.03 kPa) level, as well as long-term stability in mechanical properties over a two-week period. Cell adhesion to these matrices can be either user-defined by functionalizing synthetic fibers with thiolated adhesive peptides or methacrylated heparin to sequester cell-derived ECM proteins. We utilized DexVS fibrous matrices to investigate the role of matrix mechanics on the activation of fibroblasts into myofibroblasts, a key step of the fibrotic progression. In contrast to previous findings with non-fibrous hydrogel substrates, we find that fibroblasts in soft and deformable matrices exhibit increased spreading, focal adhesion formation, proliferation, and myofibroblast activation as compared to cells on stiffer matrices with equivalent starting architecture. STATEMENT OF SIGNIFICANCE: Cellular mechanosensing of fibrillar extracellular matrices plays a critical role in homeostasis and disease progression in stromal connective tissue. Here, we established a new material system composed of electrospun dextran vinyl sulfone polymeric fibers. These matrices exhibit architectural, mechanical, and biochemical tunability to accurately model diverse tissue microenvironments found in the body. In contrast to previous observations with non-fibrous hydrogels, we find that fibroblasts in soft and deformable fibrous matrices exhibit increased spreading and focal adhesion formation as compared to those in stiffer matrices with equivalent architecture. We also investigated the role of matrix stiffness on myofibroblast activation, a critical step in the fibrotic cascade, and find that low stiffness matrices promote increased myofibroblast activation.

Formulation and polymerization of foamed 1,4-BDDMA-in-water emulsions

Emulsion and foam templating allow the synthesis of tailor-made polymer foams. A complementary templating route is foamed emulsion templating. The concept is based on the generation of a monomer-in-water emulsion which is subsequently foamed. After polymerization of the foamed emulsion, one obtains open-cell polymer foams with porous pore walls. In the paper at hand, we generated foamed emulsions and synthesized polymer foams which are based on the monomer 1,4-butanediol dimethacrylate (1,4-BDDMA). The main challenge was to find the optimal composition of the emulsion by varying the components systematically. We will discuss that the composition of the monomer-in-water emulsion is key for the stability of the foamed emulsion and thus for the structure of the resulting polymer foam. The final composition of the continuous phase was found to be 65 vol% 1,4-BDDMA, 30 vol% water and 5 vol% glycerol. We foamed and polymerized this emulsion to check the foamed emulsion's suitability as a template for solid polymer foams. We generated a foamed emulsion with a mean bubble diameter of 151 μm ± 90 μm and obtained a highly porous poly(1,4-BDDMA) foam with a pore mean diameter of 366 μm ± 91 μm. Furthermore, the polymer foam has a “sub-porosity” within the pore walls.

Emulsion and foam templating allow the synthesis of tailor-made polymer foams.