Balasubramanian P (2016)
Publication Type: Thesis
Publication year: 2016
Bioactive glasses (BGs) continue to attract interest as promising materials for bone regeneration. In the broad family of BGs, boron containing systems, including B-doped silicate, borosilicate glasses and borate glasses, are being increasingly considered due to their attractive osteogenic and neovascularization properties. In this work, a new series of BGs based on the 13-93 composition (SiO2-CaO-Na2O-P2O5-K2O-MgO-B2O3) was prepared and three-dimensional scaffolds were produced by the polymer replica technique. The compressive strength of these scaffolds was found to be significantly higher than that of standard 45S5 Bioglass® scaffolds which is related to the higher densification rate of struts achieved by viscous flow during the sintering process. In vitro dissolution studies in cell culture medium were carried out over a period of 14 days and the formation of hydroxyapatite (HA) was confirmed using different characterization techniques such as Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The boron-based scaffolds immersed in cell culture medium exhibited a moderate release of B and Si ions which was measured using Inductively Coupled Plasma-Optical emission analyses. The effects of the ionic dissolution products (IDPs) of the boron-based BG scaffolds on mouse bone marrow stromal cells (ST2 cells) in vitro were ascertained, using an angiogenesis assay. The expression and secretion of angiogenic growth factor, vascular endothelial growth factor (VEGF) from ST2 cells were measured quantitatively using the VEGF ELISA Kit. Cellular response was found to be dependent on the boron content and the B release profile from the glasses corresponded to the positive/negative influence in their biological activity. Functionalizing the surfaces of these BG scaffolds with biologically active molecules or enzymes is a suitable strategy to enhance both the inorganic and biological responses of the biomaterial and to stimulate physiological tissue regeneration. Alkaline Phosphatase (ALP) is a metalloenzyme involved, significantly, in osteogenesis and is highly expressed in mineralized tissue cells. Silanization was performed, followed by ALP grafting on the surface of the BG scaffolds, which was confirmed by FTIR and enzymatic activity test, respectively. The ability of the boron-containing BG scaffolds, with and without ALP grafting, to stimulate VEGF from ST2 cells was determined. An in vitro osteogenic differentiation experiment, with and without the presence of osteogenic stimulating agents, was executed over a period of 14 days. It was determined that the ALP grafted to the surface of boron-containing scaffolds equated the performance of an osteogenic stimulating agent during the differentiation of ST2 cells. Cell viability and proliferation were determined using mitochondrial & LDH activity and BrdU (calorimetric) assay, respectively. Specific ALP activity and a mineralization assay revealed that the ALP-functionalized boron-containing scaffolds possess excellent capabilities to differentiate stromal cells into osteoblast-like phenotype. A preliminary subcutaneous implantation study in rats was carried out (by collaborators) to evaluate the performance of ALP-functionalized scaffolds in vivo. The influence of an enzyme (ALP) was established, in terms of ion release kinetics, directing better cell-matrix interactions, osteogenic differentiation and angiogenic potential, for bone regeneration applications. In summary, the combination of boron-containing BG scaffolds with the enzyme ALP has facilitated the inception of a promising strategy to enhance bone healing and regeneration.
Balasubramanian, P. (2016). Oberflächenmodifikation von bioaktiven Glasstützstrukturen.
Balasubramanian, Preethi. Oberflächenmodifikation von bioaktiven Glasstützstrukturen.2016.