Simultaneous nano- and microscale structural control of injectable hydrogels via the assembly of nanofibrous protein microparticles for tissue regeneration

Biomaterials. 2019 Dec;223:119458. doi: 10.1016/j.biomaterials.2019.119458. Epub 2019 Aug 29.


Injectable hydrogels are advantageous as tissue regeneration scaffolds, as they can be delivered through a minimally invasive injection and seamlessly integrate with the target tissues. However, an important shortcoming of current injectable hydrogels is the lack of simultaneous control over their micro- and nanoscale structures. In this article, the authors report a strategy for developing injectable hydrogels that integrate a fibrous nanostructure and porous microstructure. The hydrogels are prepared by using novel nanofibrous microparticles as the building blocks. The protein based nanofibrous microparticles, fabricated by a spray freezing technology, can be injected through a syringe-needle system. A cell-compatible photocuring process can be deployed to connect the microparticles and form a mechanically robust hydrogel scaffold. The inter-particle voids combined to form the interconnected micropores and the diameter of the nanofibers (100-300 nm) closely mimics that of the native extracellular matrix. Compared to the non-porous hydrogels and non-fibrous hydrogels, the microparticle annealed nanofibrous (MANF) hydrogels potently enhance the osteogenic-marker expression (ALP, Runx2, OCT and BSP) and mineralization of human mesenchymal stem cells in vitro. MANF hydrogels also facilitate cell infiltration and enhance neovasculization in a subcutaneous implantation model in vivo. The capacity of MANF hydrogels to promote bone regeneration is investigated in a calvarial bone repair model. MANF hydrogels demonstrate significant higher bone regeneration after 8 weeks, indicating the significant role of microporosity and nanofibrous architecture in bone regeneration.

Keywords: Extracellular matrix; Hydrogels; Microparticle; Nanofiber; Regenerative medicine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biocompatible Materials / chemistry
  • Bone Regeneration*
  • Cell Adhesion
  • Cell-Derived Microparticles*
  • Cross-Linking Reagents
  • Extracellular Matrix / chemistry
  • Gelatin
  • Humans
  • Hydrogels / chemistry*
  • Injections
  • Mesenchymal Stem Cells
  • Microscopy, Electron, Scanning
  • Nanofibers / chemistry*
  • Nitrogen / chemistry
  • Osteogenesis
  • Polymers / chemistry
  • Rats
  • Rats, Sprague-Dawley
  • Regenerative Medicine / methods
  • Stress, Mechanical
  • Tissue Engineering / instrumentation*
  • Tissue Engineering / methods
  • Tissue Scaffolds / chemistry*
  • Wound Healing
  • X-Ray Microtomography


  • Biocompatible Materials
  • Cross-Linking Reagents
  • Hydrogels
  • Polymers
  • Gelatin
  • Nitrogen