Silk fibroin is a promising biomaterial for tissue engineering due to its valuable mechanical and biological properties. However, being a natural product and a protein, it lacks the processability and uniform quality of an advanced synthetic material. Here we propose a way to overcome this contradiction using novel fibroin photocrosslinkable derivative (FBMA). FBMA was synthesized by methacrylation of native fibroin nucleophilic side groups. It was dissolved in either formic acid (FA) or hexafluoroisopropanol (HFIP), and the obtained solutions were photocrosslinked into hydrogel scaffolds of various structural forms including films, micropatterns, pads and macroporous sponges. UV-exposition of dry FBMA films through a photomask created complex microscaled patterns of the polymer. The nature of the solvent affected the properties of resulting hydrogels. When HFIP was used as the solvent, the resulting hydrogels had a storage modulus ∼4 times higher than that of hydrogels fabricated using FA and ∼20 times higher compared to the reference hydrogel obtained from pristine fibroin. Both FBMA-based hydrogels were biocompatible and supported fibroblast adhesion and growth in vitro . Cells cultivated on FBMA scaffolds produced with HFIP exhibited more spread phenotype at 4 and 24 h of cultivation, consistent with increased stiffness of the hydrogel. Hence, FBMA is an attractive material for fabrication of micropatterned scaffolds of centimeter-scale size with minutely tunable physico-chemical properties via convenient and reproducible technological processes, applicable for rapid prototyping.

We use serial section scanning probe nanotomography to study the 3D structure, nanoporosity and pore interconnectivity of biocompatible scaffolds made of fibroin and recombinant spidroin 1 (rS1/9). Significant nanoporosity (24%) and pore percolation is detected for rS1/9 scaffolds. It is assumed to contribute to higher in vivo tissue regeneration efficiency of rS1/9 scaffolds.

Microcarriers generated from recombinant spidroin 1F9 are suitable for use as an injection material. The microcarriers were a heterogeneous mixture of microgel particles ranging from 50 to 300 µm in size with the predominance of particles of 50-150 µm. The surface of these microparticles had a complex topography and ensured efficient cultivation of primary and immortalized fibroblasts. Intradermal injections of microgel suspensions into the area of full-thickness skin wounds did not lead to the development of acute inflammation in mice; instead, they accelerated the recovery of skin tissue and stimulated neurogenesis and angiogenesis.

Previously, we have described the preparation of a novel fibroin methacrylamide (FbMA), a polymer network with improved functionality, capable of photocrosslinking into Fb hydrogels with elevated stiffness. However, it was unclear how this new functionality affects the structure of the material and its beta-sheet-associated crystallinity. Here, we show that the proposed method of Fb methacrylation does not disturb the protein’s ability to self-aggregate into the stable beta-sheet-based crystalline domains. Fourier transform infrared spectroscopy (FTIR) shows that, although the precursor ethanol-untreated Fb films exhibited a slightly higher degree of beta-sheet content than the FbMA films (46.9% for Fb-F-aq and 41.5% for FbMA-F-aq), both materials could equally achieve the highest possible beta-sheet content after ethanol treatment (49.8% for Fb-F-et and 49.0% for FbMA-F-et). The elasticity modulus for the FbMA-F-et films was twofold higher than that of the Fb-F-et as measured by the uniaxial tension (130 ± 1 MPa vs. 64 ± 6 MPa), and 1.4 times higher (51 ± 11 MPa vs. 36 ± 4 MPa) as measured by atomic force microscopy. The culturing of human MG63 osteoblast-like cells on Fb-F-et, FbMA-F-et-w/oUV, and FbMA-F-et substrates revealed that the photocrosslinking-induced increment of stiffness increases the area covered by the cells, rearrangement of actin cytoskeleton, and vinculin distribution in focal contacts, altogether enhancing the osteoinductive activity of the substrate.