Abstract
The aim of the present study was to test the hypothesis that sandblasted and acid etched titanium surfaces can be functionalised with vascular endothelial growth factor (VEGF) using oligonucleotides for anchorage and slow release. rhVEGF165 molecules were conjugated to strands of 30-mer non-coding DNA oligonucleotides (ODN) and hybridised to complementary ODN anchor strands which had been immobilised to the surface of sandblasted/acid etched (SAE) Ti specimens. Specimens with non-conjugated VEGF adsorbed to ODN anchor strands and to blank SAE surfaces served as controls. Specific binding of conjugated VEGF exhibited the highest percentage of immobilised VEGF (71.0 %), whereas non-conjugated VEGF only achieved 53.2 and 30.7 %, respectively. Cumulative release reached 54.0 % of the immobilised growth factor in the group of specifically bound VEGF after 4 weeks, whereas non-conjugated VEGF adsorbed to ODN strands released 78.9% and VEGF adsorbed to SAE Ti surfaces released 97.4 %. Proliferation of human umbilical vein endothelial cells (HUVECs) was significantly increased on the surfaces with specifically bound VEGF compared to the control surfaces and SAE Ti surfaces without VEGF. Moreover, the released conjugated VEGF exhibited biological activity by induction of von Willebrand Factor (vWF) in mesenchymal stem cells. It is concluded that the angiogenic functionalisation of SAE titanium surfaces can be achieved by conjugation of VEGF to ODN strands and hybridisation to complementary ODN strands that are anchored to the titanium surface. The angiogenic effect is exerted both through the immobilised and the released portion of the growth factor.
Highlights
The aim of the present study was to test the hypothesis that sandblasted and acid etched titanium surfaces can be functionalised with vascular endothelial growth factor (VEGF) using oligonucleotides for anchorage and slow release. rhVEGF165 molecules were conjugated to strands of 30-mer non-coding DNA oligonucleotides (ODN) and hybridised to complementary ODN anchor strands which had been immobilised to the surface of sandblasted/acid etched (SAE) Ti specimens
The release after the first week showed that the surface loaded with conjugated VEGF hybridised to nano-anchored oligonucleotides had a significantly higher release from day 10 to the end of the observation period than the surface loaded with non-conjugated VEGF (Fig. 2a)
Calculation of the cumulative release showed that the rapid desorption of non-conjugated rhVEGF165 from the SAE surfaces has led to an almost complete release after one week (95.3 %, SD: 0.2) which did hardly change until the end of the observation period (97.4 %, SD: 0.01) The release of non-conjugated rhVEGF165 from ODN equipped SAE surfaces was identical in the first three days where after it slowed down reaching a plateau at 77.6 % (SD: 0.07) after one week, too, with almost no change until day 28 (78.9 %, SD: 0.01)
Summary
The aim of the present study was to test the hypothesis that sandblasted and acid etched titanium surfaces can be functionalised with vascular endothelial growth factor (VEGF) using oligonucleotides for anchorage and slow release. rhVEGF165 molecules were conjugated to strands of 30-mer non-coding DNA oligonucleotides (ODN) and hybridised to complementary ODN anchor strands which had been immobilised to the surface of sandblasted/acid etched (SAE) Ti specimens. RhVEGF165 molecules were conjugated to strands of 30-mer non-coding DNA oligonucleotides (ODN) and hybridised to complementary ODN anchor strands which had been immobilised to the surface of sandblasted/acid etched (SAE) Ti specimens. Specimens with non-conjugated VEGF adsorbed to ODN anchor strands and to blank SAE surfaces served as controls. Cumulative release reached 54.0 % of the immobilised growth factor in the group of bound VEGF after 4 weeks, whereas non-conjugated VEGF adsorbed to ODN strands released 78.9 % and VEGF adsorbed to SAE Ti surfaces released 97.4 %. It is concluded that the angiogenic functionalisation of SAE titanium surfaces can be achieved by conjugation of VEGF to ODN strands and hybridisation to complementary ODN strands that are anchored to the titanium surface. The angiogenic effect is exerted both through the immobilised and the released portion of the growth factor
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