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- MSc, (2014-2016): Fabrication and characterization of injectable and porous bone cement based on laponite/Ca-P for treatment of bone defect
An increase in the number of bone injuries consisted of bone defects and development of minimally invasive surgeries have led to development of injectable biomaterials with enhanced bone regeneration ability. The aim of present study was to fabricate porous nanocomposite of laponite (LAP): dexamethasone (DEX)-calcium phosphate bone cement. In the first step, DEX was encapsulated with concentration of 2 mg/ml into LAP nanodisks at different pHs (3, 7 and 13) and the effects of pH changes were assessed on the DEX loading efficiency. Moreover, DEX release mechanism in both acidic and physiological environments was evaluated. As prepared nanohybrids were evaluated using X-ray diffraction, scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, zeta potential and UV spectroscopy. Moreover, effects of LAP/DEX nanohybrids on the MG63 cell line behavior were studied. In the second step, calcium phosphate cement based on α- three calcium phosphate (α-TCP-98 wt.%) and hydroxyapatite HA-2 wt.%) nanopowders as powder phase and a 2.5 wt.% Na2HPO4 aqueous solution as liquid phase was fabricated and characterized. In order to improve the mechanical properties of calcium phosphate cement, LAP/DEX nanohybrids at different concentrations (0.5, 1, 2 and 3 wt. %) was added into powder phase of cement, and after optimization of LAP concentration based on mechanical and biological properties, the nanocomposites were employed as drug delivery system for controlled release of DEX. In the last step, porous nanocomposite calcium phosphate cement was made using NaHCO3 as foaming agent, and the effects of its concentration on the mechanical and biological properties of cement were evaluated. Zeta potential and UV-vis results revealed that in acidic condition, DEX was loaded on the surface and interlayer space of LAP nanoplates through hydrogen bonds and electrostatic forces. Moreover, release of DEX from LAP nanoplates at both environments occurred in a sustained manner. Differently, in acidic condition, due to the protonation of LAP surfaces, the amount of released DEX was increased. On the other hand, the incorporation of LAP/DEX nanohybrids upon 2 wt.% led to significantly enhance in compression strength (1.4 times) and elastic modulus (2.5 times) compared to pure bone cement. Nevertheless, more increasing of LAP/DEX content led to reduce in mechanical properties of the nanocomposite cement. Moreover, incorporation of foaming agent to powder phase of cement containing 2 % LAP/DEX nanohybrid resulted in the development of porous nanocomposite cement consisting of 62.50±4.95 % macropores. Although macroporosity resulted a reduction in compression strength (10 times) and elastic modulus (4 times) of porous nanocomposite cement compared to those of bulk nanocomposite cement, they were still more than those of pure porous calcium phosphate cement. Cell culture was performed on the both bulk and porous nanocomposite cements. Results demonstrated that incorporation of LAP/DEX nanohybrids led to improvement of MG63 cell proliferation, adhesion and growth compared to free-LAP/DEX samples. Moreover, results of drug release from nanocomposite cements and porous nanocomposite cements displayed sustained release of DEX from these carriers. Finally, porous nanocomposite of LAP/DEX-calcium phosphate bone cement might be used as filler for bone defects and facilitate the regeneration of bone formation.
Outcome: 1st Paper, 2nd Paper, 3rd Paper, 4th Paper