Supracolloidal Assemblies as Sacrificial Templates for Porous Silk-Based Biomaterials

Abstract

Tissues in the body are hierarchically structured composite materials with tissue-specific properties. Urea self-assembles via hydrogen bonding interactions into crystalline supracolloidal assemblies that can be used to impart macroscopic pores to polymer-based tissue scaffolds. In this communication, we explain the solvent interactions governing the solubility of urea and thereby the scope of compatible polymers. We also highlight the role of solvent interactions on the morphology of the resulting supracolloidal crystals. We elucidate the role of polymer-urea interactions on the morphology of the pores in the resulting biomaterials. Finally, we demonstrate that it is possible to use our urea templating methodology to prepare Bombyx mori silk protein-based biomaterials with pores that human dermal fibroblasts respond to by aligning with the long axis of the pores. This methodology has potential for application in a variety of different tissue engineering niches in which cell alignment is observed, including skin, bone, muscle and nerve.

Sacrificial crystal templating of hyaluronic acid-based hydrogels

“…3B), imparted by the potassium dihydrogen phosphate crystals; and the urea crystals imparted elongated voids spaces of 10s to 100s of µm in width and lengths of over 1000 µm in the hydrogels (Fig. 3C), with some evidence of urea crystal alignment (in line with our previous reports) [22,23,40,41,42,43]. The macropore structures resemble the negative imprint of the sacrificial crystals inside the hydrogel matrix, and crystal templated hydrogels possess a larger void volume than comparable hydrogels without the sacrificial porogen, and the pores imparted to the hydrogels using our methodology should be cell-permeable by virtue of their size.…”

“…It is noteworthy that the templating methodology would be applicable to a broad range of water soluble polymers (e.g. polyethylene glycols, proteins) [22,23,40,41,42,43]. The void regions within the hydrogel samples were imaged by cryoSEM ( Fig.…”

Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering

“…Silk protein-based materials are also candidates for the generation of tissue scaffolds [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. The natural silk fibroin of the domesticated Bombyx mori silkworm is the most commonly investigated for such applications [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]; however, recombinantly-produced silk-inspired proteins represent interesting alternatives because it is possible to produce large quantities of such silks with designed primary sequences [ 33 , 34 , 35 , 36 , 37 ]. Silk-based composites are also widely investigated for application as tissue scaffolds [ 37 , 38 , 39 , 40 ], and preclinical trials in animal models are promising [ 35 , 36 , 41 ].…”