Protease-degradable microgels for protein delivery for vascularization

Abstract

Degradable hydrogels to deliver bioactive proteins represent an emerging platform for promoting tissue repair and vascularization in various applications. However, implanting these biomaterials requires invasive surgery, which is associated with complications such as inflammation, scarring, and infection. To address these shortcomings, we applied microfluidics-based polymerization to engineer injectable poly(ethylene glycol) microgels of defined size and crosslinked with a protease degradable peptide to allow for triggered release of proteins. The release rate of proteins covalently tethered within the microgel network was tuned by modifying the ratio of degradable to non-degradable crosslinkers, and the released proteins retained full bioactivity. Microgels injected into the dorsum of mice were maintained in the subcutaneous space and degraded within 2 weeks in response to local proteases. Furthermore, controlled release of VEGF from degradable microgels promoted increased vascularization compared to empty microgels or bolus injection of VEGF. Collectively, this study motivates the use of microgels as a viable method for controlled protein delivery in regenerative medicine applications.

The Influence of Hyaluronic Acid and Glioblastoma Cell Coculture on the Formation of Endothelial Cell Networks in Gelatin Hydrogels

“…The methacrylamide groups on the GelMA backbone, in addition to being essential for photopolymerization, provide a reaction site to covalently tether biomolecules to the GelMA hydrogel matrix. Here, we were motivated by the known significance of VEGF in GBM‐associated angiogenesis and the typical requirement that VEGF be available continuously to promote vascularization . For extended culture times, continuous media supplementation can be expensive; further, it is difficult to control where in a hydrogel VEGF is available, a critical consideration in cases where nonuniform endothelial cell networks may be desirable.…”

Designing Microgels for Cell Culture and Controlled Assembly of Tissue Microenvironments

“…Incorporation of degradable crosslinks can be key for in vivo applications, where scaffold degradation allows for tissue in growth and remodeling. This is often achieved through the incorporation of protease degradable [33][34][35] crosslinks within the microgels. Microgel degradation can also be utilized to achieve drug release in response to specific stimuli (e.g., redox conditions [36] or enzymatic activity [37] ).…”

Parallel droplet microfluidics for high throughput cell encapsulation and synthetic microgel generation

“…Synthetic polymers provide tuneable release rates of encapsulated proteins that can be tailored based on diffusion through the hydrogel network or hydrolytic/enzymatic degradation of microgels [2][3][4] . These injectable microgels can be implanted in a minimally invasive manner for extended local delivery of therapeutic proteins, such as growth factors and cytokines.…”

“…Maleimides efficiently react with free thiols to form covalent bonds, allowing any cysteine containing peptide or thiolated ligand to be tethered to microgels. This versatile chemistry enables local and sustained presentation of bioactive molecules in microgels, as well as enzyme-mediated active release of therapeutic proteins when microgels are crosslinked with protease-sensitive crosslinks 2 . Crosslinking PEG-4MAL macromers can be accomplished with dithiol molecules and does not require free radical initiators, which are detrimental to encapsulated cell health 13 .…”