Methacrylated Gelatin as a Scaffold for Mechanically Isolated Stromal Vascular Fraction for Cutaneous Wound Repair

Mechanically processed stromal vascular fraction (mSVF) is a highly interesting cell source for regenerative purposes, including wound healing, and a practical alternative to enzymatically isolated SVF. In the clinical context, SVF benefits from scaffolds that facilitate viability and other cellular properties. In the present work, the feasibility of methacrylated gelatin (GelMA), a stiffness-tunable, light-inducible hydrogel with high biocompatibility is investigated as a scaffold for SVF in an in vitro setting. Lipoaspirates from elective surgical procedures were collected and processed to mSVF and mixed with GelMA precursor solutions. Non-encapsulated mSVF served as a control. Viability was measured over 21 days. Secreted basic fibroblast growth factor (bFGF) levels were measured on days 1, 7 and 21 by ELISA. IHC was performed to detect VEGF-A, perilipin-2, and CD73 expression on days 7 and 21. The impact of GelMA-mSVF on human dermal fibroblasts was measured in a co-culture assay by the same viability assay. The viability of cultured GelMA-mSVF was significantly higher after 21 days (p < 0.01) when compared to mSVF alone. Also, GelMA-mSVF secreted stable levels of bFGF over 21 days. While VEGF-A was primarily expressed on day 21, perilipin-2 and CD73-positive cells were observed on days 7 and 21. Finally, GelMA-mSVF significantly improved fibroblast viability as compared with GelMA alone (p < 0.01). GelMA may be a promising scaffold for mSVF as it maintains cell viability and proliferation with the release of growth factors while facilitating adipogenic differentiation, stromal cell marker expression and fibroblast proliferation

Supramolecular Reinforcement of Polymer – Nanoparticle Hydrogels for Modular Materials Design

Moldable hydrogels are increasingly used as injectable or extrudable materials in biomedical and industrial applications owing to their ability to flow under applied stress (shear-thin) and reform a stable network (self-heal). Nanoscale components can be added to dynamic polymer networks to modify their mechanical properties and broaden the scope of applications. Viscoelastic polymer–nanoparticle (PNP) hydrogels comprise a versatile and tunable class of dynamic nanocomposite materials that form via reversible interactions between polymer chains and nanoparticles. However, PNP hydrogel formation is restricted to specific interactions between select polymers and nanoparticles, resulting in a limited range of mechanical properties and constraining their utility. Here, a facile strategy to reinforce PNP hydrogels through the simple addition of α-cyclodextrin (αCD) to the formulation is introduced. The formation of polypseudorotoxanes between αCD and the hydrogel components resulted in a drastic enhancement of the mechanical properties. Furthermore, supramolecular reinforcement of CD–PNP hydrogels enabled decoupling of the mechanical properties and material functionality. This allows for modular exchange of structural components from a library of functional polymers and nanoparticles. αCD supramolecular binding motifs are leveraged to form CD–PNP hydrogels with biopolymers for high-fidelity 3D (bio)printing and drug delivery as well as with inorganic NPs to engineer magnetic or conductive materials.ISSN:0935-9648ISSN:1521-409

Building block properties govern granular hydrogel mechanics through contact deformations

Granular hydrogels have been increasingly exploited in biomedical applications, including wound healing and cardiac repair. Despite their utility, design guidelines for engineering their macroscale properties remain limited, as we do not understand how the properties of granular hydrogels emerge from collective interactions of their microgel building blocks. In this work, we related building block features (stiffness and size) to the macroscale properties of granular hydrogels using contact mechanics. We investigated the mechanics of the microgel packings through dynamic oscillatory rheology. In addition, we modeled the system as a collection of twobody interactions and applied the Zwanzig and Mountain formula to calculate the plateau modulus and viscosity of the granular hydrogels. The calculations agreed with the dynamic mechanical measurements and described how microgel properties and contact deformations define the rheology of granular hydrogels. These results support a rational design framework for improved engineering of this fascinating class of materials.ISSN:2375-254

Hierarchical biomaterials via photopatterning-enhanced direct ink writing

Recent advances in additive manufacturing (AM) technologies provide tools to fabricate biological structures with complex three-dimensional (3D) organization. Deposition-based approaches have been exploited to manufacture multimaterial constructs. Stimulus-triggered approaches have been used to fabricate scaffolds with high resolution. Both features are useful to produce biomaterials that mimic the hierarchical organization of human tissues. Recently, multitechnology biofabrication approaches have been introduced that integrate benefits from different AM techniques to enable more complex materials design. However, few methods allow for tunable properties at both micro- and macro-scale in materials that are conducive for cell growth. To improve the organization of biofabricated constructs, we integrated direct ink writing (DIW) with digital light processing (DLP) to form multimaterial constructs with improved spatial control over final scaffold mechanics. Polymer-nanoparticle hydrogels were combined with methacryloyl gelatin (GelMA) to engineer dual inks that were compatible with both DIW and DLP. The shear-thinning and self-healing properties of the dual inks enabled extrusion-based 3D printing. The inclusion of GelMA provided a handle for spatiotemporal control of cross-linking with DLP. Exploiting this technique, complex multimaterial constructs were printed with defined mechanical reinforcement. In addition, the multitechnology approach was used to print live cells for biofabrication applications. Overall, the combination of DIW and DLP is a simple and efficient strategy to fabricate hierarchical biomaterials with user-defined control over material properties at both micro- and macro-scale.ISSN:1758-5082ISSN:1758-509

Methacrylated Gelatin as a Scaffold for Mechanically Isolated Stromal Vascular Fraction for Cutaneous Wound Repair

Mechanically processed stromal vascular fraction (mSVF) is a highly interesting cell source for regenerative purposes, including wound healing, and a practical alternative to enzymatically isolated SVF. In the clinical context, SVF benefits from scaffolds that facilitate viability and other cellular properties. In the present work, the feasibility of methacrylated gelatin (GelMA), a stiffness-tunable, light-inducible hydrogel with high biocompatibility is investigated as a scaffold for SVF in an in vitro setting. Lipoaspirates from elective surgical procedures were collected and processed to mSVF and mixed with GelMA precursor solutions. Non-encapsulated mSVF served as a control. Viability was measured over 21 days. Secreted basic fibroblast growth factor (bFGF) levels were measured on days 1, 7 and 21 by ELISA. IHC was performed to detect VEGF-A, perilipin-2, and CD73 expression on days 7 and 21. The impact of GelMA-mSVF on human dermal fibroblasts was measured in a co-culture assay by the same viability assay. The viability of cultured GelMA-mSVF was significantly higher after 21 days (p < 0.01) when compared to mSVF alone. Also, GelMA-mSVF secreted stable levels of bFGF over 21 days. While VEGF-A was primarily expressed on day 21, perilipin-2 and CD73-positive cells were observed on days 7 and 21. Finally, GelMA-mSVF significantly improved fibroblast viability as compared with GelMA alone (p < 0.01). GelMA may be a promising scaffold for mSVF as it maintains cell viability and proliferation with the release of growth factors while facilitating adipogenic differentiation, stromal cell marker expression and fibroblast proliferation.ISSN:1422-006

Methacrylated Gelatin as a Scaffold for Mechanically Isolated Stromal Vascular Fraction for Cutaneous Wound Repair

Mechanically processed stromal vascular fraction (mSVF) is a highly interesting cell source for regenerative purposes, including wound healing, and a practical alternative to enzymatically isolated SVF. In the clinical context, SVF benefits from scaffolds that facilitate viability and other cellular properties. In the present work, the feasibility of methacrylated gelatin (GelMA), a stiffness-tunable, light-inducible hydrogel with high biocompatibility is investigated as a scaffold for SVF in an in vitro setting. Lipoaspirates from elective surgical procedures were collected and processed to mSVF and mixed with GelMA precursor solutions. Non-encapsulated mSVF served as a control. Viability was measured over 21 days. Secreted basic fibroblast growth factor (bFGF) levels were measured on days 1, 7 and 21 by ELISA. IHC was performed to detect VEGF-A, perilipin-2, and CD73 expression on days 7 and 21. The impact of GelMA-mSVF on human dermal fibroblasts was measured in a co-culture assay by the same viability assay. The viability of cultured GelMA-mSVF was significantly higher after 21 days (p p < 0.01). GelMA may be a promising scaffold for mSVF as it maintains cell viability and proliferation with the release of growth factors while facilitating adipogenic differentiation, stromal cell marker expression and fibroblast proliferation