Enhanced osteoinductivity and osteoconductivity through hydroxyapatite coating of silk‐based tissue‐engineered ligament scaffold

Abstract

Hybrid silk scaffolds combining knitted silk fibers and silk sponge have been recently developed for use as ligament-alone grafts. Incorporating an osteoinductive phase into the ends of a ligament scaffold may potentially generate an integrated "bone-ligament-bone" graft and improve graft osteointegration with host bone. To explore the possible application of hydroxyapatite (HA) coating in the fabrication of osteoinductive ends of silk-based scaffold, HA was coated on the hybrid silk scaffold and the effects to the bone-related cells were evaluated. HA could be coated in a uniform and controlled manner on the silk sponge, using an alternate soaking technology, with the amount deposited being dependent on the number of soaking cycles. HA coating also progressively reduced the hydrophobicity of silk surface (decreasing water contact angle from 87° to 42-76°, after 1-3 soaking cycles), making the HA-coated silk scaffold less favorable for initial cell attachments; but the attached cells showed viability and sustained proliferation on the HA-coated scaffold. As demonstrated by real-time polymerase chain reaction and alkaline phosphatase assay, the osteoinductivity of HA-coated silk scaffolds resulted in the osteogenic differentiation of bone marrow mesenchymal stem cells, and the osteoconductivity of HA-coated silk scaffolds supported osteoblasts growth and maintained the properties of mature osteoblasts. These properties of HA-coating demonstrated its possible application in fabricating osteoinductive ends of the silk-based ligament graft to potentially enhance graft-to-host bone integration.

Effects of preparation methods on the bone formation potential of apatite-coated chitosan microspheres

“…[36] He and coworkers further clarified that hydroxyapatite could act as nucleation sites for mineralization and promote further deposition of apatite crystals from cells, thus enhancing the formation of a mineral structure. [37] Several methods, including mass change method, scratch method, and alizarin red-based assay have been tried out to quantify the mineral contents. However, we were not successful since the microspheres were small, spherical, and the content of mineral was low.…”

Biopolymer/Calcium Phosphate Scaffolds for Bone Tissue Engineering

“…[ 66 ] Another report also showed that HAp coating on the silk scaffold resulted in an osteogenic differentiation of the seeded BMSCs in a normal culture medium, and this effect was further enhanced by culturing in osteogenic medium, indicating enhanced osteoinductivity of the HAp-coated silk scaffold. [ 128 ] Furthermore, recent in vivo studies also revealed the positive role of HAp incorporation in bone regeneration in defect models from small to large animals. [ 154,155 ] For instance, Liu et al demonstrated that nanofi brous hydroxyapatite/ chitosan (nHAp/CTS) scaffolds can promote bone regeneration by supporting the adhesion, proliferation, and activating integrin-BMP/Smad signaling pathway of BMSCs, when compared with the CTS group without HAp.…”

Spatially and temporally controlled hydrogels for tissue engineering

“…Such constructs have been explored for the engineering of tendon and ligaments tissue constructs [88]. Knitted scaffolds coated with hydroxyapatite have been utilized for engineering bone tissue and have shown excellent osteoconductivity [90]. Braided scaffolds formed from intertwined fibers offer the highest construct density and axial mechanical strength in comparison to those fabricated using other textile techniques.…”