Mineralized biomimetic collagen/alginate/silica composite scaffolds fabricated by a low-temperature bio-plotting process for hard tissue regeneration: fabrication, characterisation and in vitro cellular activities

Abstract

The natural biopolymers, collagen and alginate, have been widely used in various tissue regeneration procedures. However, their low mechanical and osteoinductive properties represent major limitations of their usage as bone tissue regenerative scaffolds. To overcome these deficiencies, biomimetic composite scaffolds were prepared using a mixture of collagen and alginate as a matrix material, and various silica weight fractions as a coating agent. The composite scaffolds were highly porous (porosity > 78%) and consisted of interconnected pores, with a mesh-like structure (strut diameter: 342–389 μm; average pore size: 468–481 μm). After incubation in a simulated body fluid, various levels of bone-like hydroxyapatite (HA) on the surface of the composite scaffolds developed in proportion to the increase in the silica content coating the scaffolds, indicating that the composite scaffolds have osteoinductive properties. The composite scaffolds were characterised in terms of various physical properties (water absorption, biodegradation and mechanical properties, etc.) and biological activities (cell viability, live/dead cells, DAPI/phalloidin analysis, osteogenic gene expression, etc.) using pre-osteoblasts (MC3T3-E1). The mechanical improvement (compressive modulus) of a composite scaffold in compressive mode was ∼2.4-fold in the dry state compared to the collagen/alginate scaffold. Cell proliferation on the composite scaffold was significantly improved by ∼1.3-fold compared to the mineralised collagen/alginate scaffold (control). Osteocalcin levels of the composite scaffold after 28 days in cell culture were significantly enhanced by 3.2-fold compared with the control scaffold. These results suggest that mineralised biomimetic composite scaffolds have potential for use in hard tissue regeneration.