Dexamethasone and doxycycline functionalized nanoparticles enhance osteogenic properties of titanium surfaces

Abstract

Objectives: To evaluate the effect of doxycycline and dexamethasone doped nanoparticles covering titanium surfaces, on osteoblasts proliferation and differentiation. Methods: Doxycycline and dexamethasone doped polymeric nanoparticles were applied on titanium discs (Ti- DoxNPs and Ti-DexNPs). Undoped NPs and uncovered Ti discs were used as control. Human MG-63 osteoblast- like cells were cultured. Osteoblasts proliferation was tested by MTT assay. Alkaline phosphatase activity was analyzed. Differentiation gene expression was assessed by real-time quantitative polymerase chain reaction. Scanning Electron Microscopy was performed to assess osteoblasts morphology. Mean comparisons were con- ducted by ANOVA and Wilcoxon or Tukey tests (p < 0.05). Results: No differences in osteoblasts proliferation were found. Osteoblasts grown on Ti-DoxNPs significantly increased alkaline phosphatase activity. Doxycycline and dexamethasone nanoparticles produced an over-ex- pression of the main osteogenic proliferative genes (TGF-β1, TGF-βR1 and TGF-βR2). The expression of Runx-2 was up-regulated. The osteogenic proteins (AP, OSX and OPG) were also overexpressed on osteoblasts cultured on Ti-DoxNPs and Ti-DexNPs. The OPG/RANKL ratio was the highest when DoxNPs were present (75-fold in- crease with respect to the control group). DexNPs also produced a significantly higher OPG/RANKL ratio with respect to the control (20 times higher). Osteoblasts grown on titanium discs were mainly flat and polygonal in shape, with inter-cellular connections. In contrast, osteoblasts cultured on Ti-DoxNPs or Ti-DexNPs were found to be spindle-shaped and had abundant secretions on their surfaces. Significance: DoxNPs and DexNPs were able to stimulate osteoblasts differentiation when applied on titanium surfaces, being considered potential inducers of osteogenic environment when performing regenerative proce- dures around titanium dental implants.