title: Dissolution kinetics of a Si-rich nanocomposite and its effect on osteoblast gene expression.
abstract: Silica-calcium phosphate nanocomposite (SCPC) has recently been proposed as a novel resorbable, bioactive, and mechanically compatible template for bone reconstruction. The effect of the physicochemical properties on the surface reactivity and dissolution kinetics of SCPC immersed in simulated body fluid (SBF) was investigated and compared to that of bioactive glass (BG). Moreover, the stimulatory effect on osteoblast gene expression of SCPC was determined using quantitative real-time polymerase chain reaction (qRT-PCR), and compared to that of hydroxyapatite (HA-200). Mercury porosimetry revealed that surface areas of SCPC particles containing 10 (SCPC10), 30 (SCPC30), and 50 (SCPC50) wt % Si-content were 14-, 18-, and 32-times higher than that of BG. Inductively coupled plasma analysis showed that after 192 h of immersion, Si-rich SCPC50 exhibited controlled bulk-dissolution and released 43.1 ppm Si, which was sixfold higher than that released from BG (7.7 ppm). Moreover, SCPC50 showed a rapid Ca-uptake from SBF and developed a surface apatite layer after only 2 h, whereas a similar layer was detected on BG after 8 days of immersion under the same experimental conditions. qRT-PCR revealed that osteopontin and osteocalcin mRNA expression by osteoblast-like cells attached to Si-rich SCPC50 was significantly higher than that on HA-200 or polystyrene after 2 days in culture. This suggested a role of dissolved Si in stimulating the differentiation and mineralization of osteoblast precursor cells. The favorable physiochemical and bioactivity properties of Si-rich SCPC nanocomposite indicate that SCPC can have wide applications as a synthetic bone graft for cell delivery applications in tissue engineering.
authors.affiliation: Center for Biomedical Engineering, Graduate School, University of Kentucky, Lexington, Kentucky 40506, USA.
authors.forename: Gautam
authors.initials: G
authors.lastname: Gupta
authors.forename: Sreenatha
authors.initials: S
authors.lastname: Kirakodu
authors.forename: Ahmed
authors.initials: A
authors.lastname: El-Ghannam
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001826:Body Fluids; D002113:Calcification, Physiologic; D002454:Cell Differentiation; D003188:Composite Resins / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D007700:Kinetics; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics; D053495:Osteopontin / Q000235:genetics; D016062:Porosity; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012825:Silicon; D012995:Solubility; D023822:Tissue Engineering / Q000379:methods
chemical_list: D003188:Composite Resins; D012333:RNA, Messenger; D015675:Osteocalcin; D053495:Osteopontin; D012825:Silicon