Orthopedic implant failure has been attributed mainly to loosening of the implant from host bone, which may be due to poor bonding of the implant material to bone tissue, as well as to bacterial infection. One promising strategy to enhance tissue integration is to develop a selective biointeractive surface that simultaneously enhances bone cell function while decreasing bacterial adhesion. In this in vitro study, the surfaces of titanium alloy substrates were functionalized by first covalently grafting carboxymethyl chitosan (CMCS), followed by the conjugation of bone morphogenetic protein-2 (BMP-2) to the CMCS-grafted surface. Bacterial adhesion on the substrates was assayed with Staphylococcus aureus and Staphylococcus epidermidis . Cell functions were investigated using osteoblasts and human bone marrow-derived mesenchymal stem cells. The results showed that bacterial adhesion on both the CMCS and CMCS-BMP-2 functionalized surfaces was significantly reduced compared to that on the pristine substrates. In addition, the CMCS-BMP-2 modified substrates significantly promoted attachment, alkaline phosphatase activity, and calcium mineral deposition of both osteoblast and human bone marrow-derived mesenchymal stem cells. The achievement of the dual functions of bacterial adhesion reduction and cell function promotion by the CMCS-BMP-2 modified titanium substrates illustrates the good potential of such surfaces for enhancement of tissue integration and implant longevity.
"Despite these excellent properties, Ti alone does not promote osseo-integration with the host bone at the implant surface. Poor bonding of Ti implants with the host bone can bring about unpredictable bone loosening over time, resulting in implant failure and patient discomfort  . To promote osseo-integration between the Ti surface and host bone, attempts have been made to modify and functionalize the Ti surface though calcium phosphate/hydroxyapatite (HAp) coating, biomolecule immobilization, and surface topography modification [4,6–9]. "
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to develop a lactoferrin (LF)-immobilized titanium (Ti) substrate to enhance the osteoblast activity of MG-63 cells. Ti substrates were first modified through heparin-dopamine (Hep-DOPA) anchorage. Then, LF was immobilized on the Hep-Ti substrates via electrostatic interactions. Hep-Ti substrates, with or without LF, were evaluated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Sustained release of LF on the Ti substrates was observed over a 28-day period. In vitro studies of osteoblast activity showed increased alkaline phosphatase activity and calcium deposition by MG-63 cells cultured on LF-immobilized Ti substrates as compared to those cultured on pristine Ti substrates, indicating that LF-immobilized Ti substrates were effective at enhancing osteoblast activity.
"ALP activity and calcium deposition are important markers for enhanced osseointegration. ALP activity is widely used as an early differentiation marker of osteoblast-cells (Shi et al., 2009a, 2009b; Turksen, Bhargava, Moe, & Aubin, 1992). We found no significant difference in ALP activity or calcium deposition between PLL grafted Ti and pristine Ti throughout 21 days of culture. "
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was to investigate the enhanced osteoblast activity of MG-63 cells cultured on titanium (Ti) with a heparin/BMP-2 (Hep/BMP-2) complex. The Ti substrates were initially modified by chemical grafting poly-l-lysine (PLL) using condensing agent, followed by immobilizing the heparin/BMP-2 complex to the PLL-grafted Ti substrate via electrostatic interactions. The surface modification of Ti substrates with PLL and/or Hep/BMP-2 complex were confirmed with scanning electron microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. Immobilized BMP-2 was released from the Hep/BMP-2/Ti substrate in a sustained manner. In vitro studies revealed that osteoblasts grown on Hep/BMP-2/Ti substrate increased ALP activity, calcium deposition, ALP and osteocalcin levels as compared to those grown on pristine Ti or PLL-Ti. These results indicated that heparin/BMP-2 complex immobilized Ti substrate can be useful to effectively improve osteoblast activity.
"Hu et al found that immobilized vascular endothelial growth factor (VEGF) on titanium via heparin-VEGF interactions, can preserve the growth factor bioactivity on both osseous and vascular components and can concomitantly reduce bacterial infection.23 Lee et al developed a novel gentamicin and bone morphogenic protein-2 for heparinized-titanium implants that enhanced osteoblast functions while simultaneously decreasing bacterial infections.24 Shi et al found that the surface functionalization of titanium with carboxymethyl chitosan and immobilized bone morphogenetic protein-2 can provide a selective biointeractive surface that simultaneously enhances bone cell function and decreases bacterial adhesion.25 Annunziata et al found that a titanium nitride coating significantly reduced bacterial adhesion and proliferation, while maintaining the prosthesis biological affinity for bone cell precursors.26 "
[Show abstract][Hide abstract] ABSTRACT: Competition occurs between the osteoblasts in regional microenvironments and pathogens introduced during surgery, on the surface of bone implants, such as joint prostheses. The aim of this study was to modulate bacterial and osteoblast adhesion on implant surfaces by using a nanotube array. Titanium oxide (TiO2) nanotube arrays, 30 nm or 80 nm in diameter, were prepared by a two-step anodization on titanium substrates. Mechanically polished and acid-etched titanium samples were also prepared to serve as control groups. The standard strains of Staphylococcus epidermidis (S. epidermidis, American Type Culture Collection [ATCC]35984) and mouse C3H10T1/2 cell lines with osteogenic potential were used to evaluate the different responses to the nanotube arrays, in bacteria and eukaryotic cells. We found that the initial adhesion and colonization of S. epidermidis on the surface of the TiO2 nanotube arrays were significantly reduced and that the adhesion of C3H10T1/2 cells on the surface of the TiO2 nanotube arrays was significantly enhanced when compared with the control samples. Based on a surface analysis of all four groups, we observed increased surface roughness, decreased water contact angles, and an enhanced concentration of oxygen and fluorine atoms on the TiO2 nanotube surface. We conclude that the TiO2 nanotube surface can reduce bacterial colonization and enhance C3H10T1/2 cell adhesion; multiple physical and chemical properties of the TiO2 nanotube surface may contribute to these dual effects.
International Journal of Nanomedicine 08/2013; 8:3093-105. DOI:10.2147/IJN.S48084 · 4.38 Impact Factor
Hyung-Mun Yun, Seok-Woo Chang, Kyung-Ran Park, Lan Herr, Eun-Cheol Kim
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