Self-assembled Monolayer Films of Phosphonates for Bonding RGD to Titanium

Abstract

Modification of the implant surface with the Arg-Gly-Asp tripeptide (RGD) putatively facilitates osteoblast attachment for improved implant fixation in the laboratory. We compared the histomorphometric and mechanical performance of titanium implants coated with RGD using a novel interface of self-assembled monolayers of phosphonates (RGD/SAMP) and implants coated with RGD using the more conventional thiolate-gold interface (RGD/thiolate-gold). We hypothesized RGD/SAMP-coated implants would show greater bone ongrowth and implant fixation than RGD/thiolate-gold-coated ones. We implanted an RGD/SAMP-coated implant in one femur and an RGD/thiolate-gold-coated in the contralateral femur of 60 rats. At 2, 4, and 8 weeks after implantation, 10 rats were sacrificed for histologic evaluation and another 10 for biomechanical testing. Bone-implant ongrowth and implant force-to-failure of the two implants were similar at all times. Although RGD/SAMP-coated implants did not show superior bone ongrowth and implant fixation, RGD/SAMP-coated implants have at least equally good histomorphometric and mechanical in vivo performance as RGD/thiolate-gold-coated ones. Additional in vivo characterization of self-assembled monolayer films of phosphonates as interface to bond RGD to titanium is needed to explore its full potential and seems justified based on the results of this study.

Immobilized antibiotics to prevent orthopaedic implant infections

“…The cell adhesion peptide RGD has been immobilized to glass [149], quartz [150–152], gold [153], silicone [154], silica [155] and titanium [156–158]. Different linkages have been used on titanium surfaces including diphosphonic acids [159–160], plasma amination [161], silanization to reveal active amines [145, 156, 162], surface photopolymerization of PEG-acrylamide groups [163], reaction with p-nitrophenyl chloroformate to activate the surface [164] and interestingly, titanium-binding peptides to allow PEGylation [165]. Antimicrobial peptides have also been grafted onto surfaces with successful bacterial killing for the cationic LL-37 on Ti [166], and the pore forming toxin maiganin I on thiol-gold [167].…”

Vascular endothelial growth factor attachment to hydroxyapatite via self-assembled monolayers promotes angiogenic activity of endothelial cells

“…SAMs have been shown to be biocompatible [42][43][44][45], and the use of growth factors to promote angiogenesis has been addressed thoroughly in recent literature [15,[46][47][48]. Surface wettability and SAM functional groups have been shown to affect HUVEC and HeLa cell attachment, with preference towards moderate contact angles (40-60°) and methyl and hydroxyl groups [49].…”

Peptide‐modified bone repair materials: Factors influencing osteogenic activity

“…66 In order to achieve covalent binding, the matrix surface must be modified specific chemical functional groups first through copolymerization, blending, and other chemical or physical methods, which results in the formation of an intermediate layer that is anchored onto the matrix surface. Specific examples to improve the extent of covalent binding include the use of collagen 67,68 or coupling reagents 69 , self-assembled monolayers of phosphonates or thiols 70 , electrodeposition, poly(L-lysine)grafted-poly(ethylene glycol) coatings, 71 and Au-thiolate species. 72 However, the weak binding of peptides to the intermediate layer or the rapid dissolution of the intermediate layer can affect the extent of maximal biological activity.…”