Development of osteogenic chitosan/alginate scaffolds reinforced with silicocarnotite containing apatitic fibers

Abstract

Porous composite scaffolds of chitosan-alginate (CH-AL) reinforced by biphasic calcium phosphate fibers containing silicon (Si) were prepared using the freeze-drying method. The fibers were synthesized using a homogenous precipitation method with differing reaction times and were characterized by XRD, FTIR, SEM, and ICP-OES. Fibers produced with no Si incorporation using two different reaction times of 4 d and 8 d comprised two phases of hydroxyapatite (similar to 93-96 wt%) and beta-tricalcium phosphate (beta-TCP). No new phases were observed by adding 0.8 wt% of Si during 4 d of precipitation. However, the addition of Si to fibers synthesized within 8 d under reflux conditions produced biphasic fibers with 1.9 wt% Si which consisted of a new phase of silicocarnotite (similar to 94 wt%) associated with the beta-TCP phase. The whisker-like fibers were 10-200 mu m in length and 0.2-5 mu m in width. The physicochemical, mechanical, and biological properties of composite scaffolds fabricated by adding different fiber contents and types were investigated. The scaffolds exhibited favorable microstructures with a high porosity (66-88%) and the interconnected pores varied in size between 40 and 250 mu m. Scaffolds containing silicocarnotite showed a significant improvement in their mechanical properties andin vitrobioactivity (using SBF testing and characterization of the apatite layer by ATR-FTIR and SEM/EDS) as well as proliferation, mineralization and adhesion of MG63 cells, when evaluated by MTT assay, alkaline phosphatase, and SEM. Scaffolds reinforced with silicocarnotite fibers also exhibited better mechanical properties and water uptake, compared to ones containing incorporated fibers made of Si. Composite scaffolds reinforced by 50 wt% fibers precipitated after 8 d were superior in terms of their mechanical properties and achieved a compressive strength and modulus of 272 kPa and 4.9 MPa, respectively, which is 400% greater than CH-AL scaffolds. The results indicate that the addition of Si into biphasic fibers, leading to the formation of silicocarnotite, makes silicocarnotite a potential candidate for the bioactive reinforcement of composite scaffolds for bone tissue engineering.