In vivo effect of immobilisation of bone morphogenic protein 2 on titanium implants through nano-anchored oligonucleotides

Abstract

The aim of the present study was to test the hypothesis that immobilisation of bone morphogenic proteins on the surface of titanium implants through nano-anchored oligonucleotides can enhance peri-implant bone formation. Non-coding 60-mer DNA oligonucleotides (ODN) were anchored to the surface of custom made sandblasted acid etched (SAE) titanium screw implants through anodic polarisation, gamma-sterilised with a standard dose of 25 kGy, and were hybridised with complementary 30-mer strands of DNA oligonucleotides conjugated to rhBMP2. Blank SAE implants, SAE implants with nano-anchored ODN and SAE implants with nano-anchored ODN and non-conjugated rhBMP2 served as controls. The implants were inserted into the tibiae of 36 Sprague Dawley rats. Perforations at the head and the tip of the implants allowed for bone ingrowth. Bone ingrowth into perforations and bone implant contact (BIC) as well as bone density (BD) at a distance of 200 µm from the implant surface were assessed after 1 , 4 and 13 weeks. Implants with nano-anchored ODN strands hybridised with conjugated rhBMP2 exhibited enhanced bone ingrowth into the perforations and increased BIC after 1 week as well as increased BIC after 4 weeks compared to controls. No difference was seen after 13 weeks. Bone density around the outer implant surface did not differ significantly at any of the intervals. It is concluded that rhBMP2 immobilised on the surface of titanium implants through nano-anchored oligonucleotide strands can enhance bone implant contact. The conditions of sterilisation tested allowed for handling under clinically relevant conditions.

Utilizing DNA for functionalization of biomaterial surfaces

“…No differences in the ALP induction between CSconjugated rhBMP-2 and native rhBMP-2 were observed for C2C12 cells, indicating full biological activity of the conjugated BMP-2 [78,96,97]. CS-BMP-2 conjugates hybridized to AS-containing titanium surfaces significantly increased the proliferation of human bone marrow stroma cells (hBMSC) at days 7 and 14 (see Fig.…”

“…In both cases, hybridized growth factors were the most stably bound [77,78,97] (Fig. Steric hindrance of the enzyme due to close proximity of the short ODN to the substrate surface is discussed as a potential reason [96]. The release of such CS-BAM constructs from AS-coated surfaces is highly probable due to double-strand dissociation, as experiments in cell culture medium did not show any signs of endonuclease activity.…”

“…1(II) and 1(III) and chapters 'Using specific substrate binding ligands and Partial incorporation into anodic oxide layers') has been used for the immobilization of four BAMs with varying structural complexity. As the different length of the propyl-or hexyl-linker did not have any significant cell biological effect, further work used exclusively 5 0 aminomodified 31mers for coupling the parathyroid hormone (PTH) N-terminal fragment 1-34 [19], recombinant human VEGF [79,95], and recombinant human BMP-2 [78,79,96,97]. As the different length of the propyl-or hexyl-linker did not have any significant cell biological effect, further work used exclusively 5 0 aminomodified 31mers for coupling the parathyroid hormone (PTH) N-terminal fragment 1-34 [19], recombinant human VEGF [79,95], and recombinant human BMP-2 [78,79,96,97].…”

“…One is the hexapeptide GRGDSP that was coupled to a 25mer CS modified at the 5 0 -terminus either with an aminopropyl or an aminohexyl group using the disuccinimidyl suberate approach [20,70]. As the different length of the propyl-or hexyl-linker did not have any significant cell biological effect, further work used exclusively 5 0 aminomodified 31mers for coupling the parathyroid hormone (PTH) N-terminal fragment 1-34 [19], recombinant human VEGF [79,95], and recombinant human BMP-2 [78,79,96,97].…”

“…The release of such CS-BAM constructs from AS-coated surfaces is highly probable due to double-strand dissociation, as experiments in cell culture medium did not show any signs of endonuclease activity. Steric hindrance of the enzyme due to close proximity of the short ODN to the substrate surface is discussed as a potential reason [96].…”