Enzymatically crosslinked SF/SF-β-TCP scaffolds incorporating Sr- and Zn-ions as hierarchical structures for osteochondral tissue engineering applications

Introduction. Bilayeredscaffolds consisting of a cartilage-like layer and an underlying bone-like layer have been proposed for osteochondral (OC) tissue applications. Silk fibroin (SF) exhibit high biocompatibility and tunable mechanical propertiesfor OC scaffolding strategies [1].Bioresorbable inorganic materials, such as β-tricalcium phosphate(β-TCP)combined with SF have shown to increase osteogenesis[2]. Herein, the development of novel monolithic and hierarchical scaffoldscombining enzymatically crosslinked SF (HRP-SF) and ZnSr-doped β-TCP, is reported for OC tissue repair/regeneration.

Experimental. The bilayered scaffolds were prepared with 80/20 (w/w) HRP-SF/undoped and ZnSr-doped β-TCP for the bone-like layers, and HRP-SF as cartilage-like layer. Salt-leaching and freeze-drying technologies were applied to induce macro-/micro-porosity to the scaffolds. Physicochemical characterization, structural integrity, and bioactivity of the scaffolds were evaluated. The in vitrocell adhesion, proliferation and extracellular matrix (ECM) production were evaluated by co-culturing human chondrocytes and human osteoblasts in the scaffolds up to 14 days.

Results and Discussion. The results showed an interconnected porosity and homogeneous β-TCP distribution into the subchondral bone layer (Fig.1a and b).The mechanical properties of ZnSr-doped scaffolds were superior than the undoped scaffolds. Co-cultured cells adhered and proliferated on the bilayered scaffolds (Fig. 1c), showing the formation of a mineralized ECM and GAGs deposition in the respective bone and cartilage-like layers.

Conclusions. The structural adaptability and suitable mechanical properties of the proposed engineered OC scaffolds, combined with the biological performance achieved using a co-culturing system, make these scaffolds a viable strategy for OC defects regeneration.

References.

[1] L.-P. Yan, J. Silva-Correia, M. Oliveira, et al., Acta biomaterialia  2015;12:227-241,2015.

[2] S. Pina, R. Canadas, G. Jiménez, et al., Cells Tissues Organs2017;204:150.