Cyclosilicate nanocomposite: a novel resorbable bioactive tissue engineering scaffold for BMP and bone-marrow cell delivery.

Abstract

Porous bioactive resorbable silica-calcium phosphate nanocomposite (SCPC) was prepared by a sintering technique. XRD analyses showed that the main crystalline phases of the SCPC are Na(3)CaPSiO(7) (clinophosinaite), beta-NaCaPO(4) (rhenanite), Na(2)CaSiO(4), and beta-quartz (SiO(2)). The clinophosinaite is a novel cyclosilicate bioactive mineral that enhanced the mechanical and bioactivity properties of the SCPC. TEM analysis showed that the grain sizes of the multiphase SCPC are in the nanometer scale. Moreover, the SCPC was engineered with nano- and microscale porosity. The SCPC had significantly higher compressive strength than porous hydroxyapatite (HA). FTIR analyses revealed the formation of biological hydroxyapatite layer on the SCPC surface after 4 days of immersion in SBF. When SCPC was loaded with rhBMP-2, it provided a superior release profile of biologically active rhBMP-2 compared to porous HA. Bone-marrow cells incubated with medium treated with the rhBMP-2 released from the SCPC-rhBMP-2 hybrid expressed significantly higher alkaline phosphatase activity than that expressed by cells incubated with media treated with rhBMP-2 released from HA-rhBMP-2. In addition, cells attached to the SCPC-rhBMP-2 hybrid produced mineralized extracellular matrix (ECM) and bone-like tissue that covered the material surface and filled pores in the entire thickness of the template after 3 weeks in culture. In contrary, cells attached to the HA-rhBMP-2 produced limited amount of unmineralized ECM after the same time period. Results of the study strongly suggest that the porous bioactive silica-calcium phosphate nanocomposite can serve as a delivery system for cells and biological molecules. The SCPC-rhBMP-2-marrow cell hybrid may serve as an alternative to autologous bone grafting.