Injectable gelatin derivative hydrogels with sustained vascular endothelial growth factor release for induced angiogenesis

Abstract

Injectable biomaterials are attractive for soft tissue regeneration because they are handled in a minimally invasive manner and can easily adapt to complex defects. However, inadequate vascularization of the injectable constructs has long been a barrier, leading to necrosis or volume reduction after implantation. In this work, we developed a three-step process to synthesize injectable gelatin-derived hydrogels that are capable of controlling growth factor delivery to induce angiogenesis. In our approach, tyramine was first introduced into gelatin chains to provide enzymatical crosslinking points for gel formation after injection. Next, heparin, a polysaccharide with binding domains to many growth factors, was covalently linked to the tyramine-modified gelatin. Finally, vascular endothelial growth factor (VEGF) was incorporated into the gelatin derivative by binding with the heparin in the gelatin derivative, and an injectable gel with controlled VEGF release was formed by an enzymatic catalytic reaction with hydrogen peroxide (H2O2) and horseradish peroxidase (HRP). The gelation time, mechanical properties and degradation of the gel was readily tailored by the gelatin concentration and the ratio of H2O2/HRP. Binding VEGF to heparin stabilizes this growth factor, protects it from denaturation and proteolytic degradation, and subsequently prolongs the sustained release. An in vitro release study and bioactivity assay indicated that the VEGF was released in a sustained manner with high bioactivity for over 3 weeks. Furthermore, a chicken chorioallantoic membrane (CAM) assay and animal experiments were performed to evaluate in vivo bioactivity of the VEGF released from the hydrogels. After 5 days of incubation on CAM, the number of blood vessels surrounding the heparin-modified hydrogels was 2.4-fold increase than that of the control group. Deeper and denser cell infiltration and angiogenesis in the heparin-modified gelatin/VEGF gels were observed than in the controls after being subcutaneously injected in the dorsal side of the mice for 2 weeks. Interestingly, even without the incorporation of VEGF, the heparin-modified gelatin derivative still had the capability to induce angiogenesis to a certain degree. Our results suggest that the gelatin derivative/VEGF is an excellent injectable delivery system for induced angiogenesis of soft tissue regeneration.

Injectable and pH-Responsive Silk Nanofiber Hydrogels for Sustained Anticancer Drug Delivery

“…Therefore, biologically derived materials such as alginate, fibrin, gelatin or chitosan have gained increased interest because of these features. [25][26][27][28][29][30][31] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 However, these natural materials are limited as injectable hydrogels, due to challenging control over mechanics, degradation and constancy in properties. In contrast, silk proteins offer a uniquely tunable system to control mechanical properties, control degradation lifetime, provide biocompatibility and offer versatility to generate various material formats including films, gels, adhesives, scaffolds or composites under aqueous and mild processing conditions without chemical or photo crosslinking requirements.…”

Injectable scaffolds: Preparation and application in dental and craniofacial regeneration

“…We recently developed an approach to synthesize injectable gelatin-derived hydrogels that are capable of controlling growth factor delivery to enhance tissue regeneration [153], as shown in Fig. 4.…”

“…(c) The released VEGF from the gelatin-derived hydrogel showed high bioactivity using a chick chorioallantoic membrane (CAM) assay. Adapted with permission from [153]. Copyright 2015 Elsevier Ltd.…”

“…(b) A schematic diagram of the formation of the hydrogel from the peptide monomer. Adapted with permission from [153]. Copyright 2011 Elsevier Ltd.…”

In situ formation of silk-gelatin hybrid hydrogels for affinity-based growth factor sequestration and release

“…18 Gelatin can be chemically modified to provide additional features (e.g., heparinization 17 or PEGylation 19 ) or to provide covalently crosslinkable motifs (e.g., methacrylates 20 , norbornene 17,20 , etc.). For example, via carbodiimide chemistry 17,21,22 , the amino groups on gelatin can be conjugated with carboxyl groups on heparin, a sulfated glycosaminoglycan that binds to various growth factors for controlling their bioavailability and for protecting them from proteolysis. [23][24][25] Sequestering growth factors by heparin near the cell surface provides a mechanism for controllable amplification of specific growth factor signaling to direct cell fate.…”