Hydroxylapatite binds more serum proteins, purified integrins, and osteoblast precursor cells than titanium or steel

Abstract

The implant material hydroxylapatite (HA) has been shown in numerous studies to be highly biocompatible and to osseointegrate well with existing bone; however, the molecular mechanisms at work behind this osseointegration remain largely unexplored. One possibility is that the implant, exposed to the patient's blood during surgery, adsorbs known cell adhesive proteins such as fibronectin and vitronectin from the serum. Osteoblast precursors could then adhere to these proteins through integrin-mediated mechanisms. In the present study, we have used a quantitative ELISA assay to test the hypothesis that hydroxylapatite will adsorb more fibronectin and vitronectin from serum than two commonly used hard-tissue materials, commercially pure titanium, and 316L stainless steel. We further used the ELISA, as well as a standard cell adhesion assay, to test the hypothesis that increased protein adsorption will lead to better binding of purified integrins alpha5beta1 and alpha(v)beta3 and osteoblast precursor cells to the HA than to the metals. Our results show that fibronectin, vitronectin, alpha5beta1, alpha(v)beta3, and osteoblast precursor cells do indeed bind better to HA than to the metals, suggesting that improved integrin-mediated cell binding may be one of the mechanisms leading to better clinical bone integration with HA-coated implants.

Osteoblast compatibility of materials depends on serum protein absorbability in osteogenesis

“…The results of QCM measurement shown in Fig.7 indicated that hydroxyapatite can absorb more serum proteins than titanium. Our results also conformed to a report that hydroxyapatite absorbed more cell attachment proteins such as fi bronectin, and vitronectin than pure titanium of the same roughness 30) . Because hydroxyapatite has stronger absorbability than titanium, the Ap disk could have gathered cell adhesion molecules on its surface even it was in serum-free medium, so that more cells adhered on the Ap disk than on the ti disk.…”

Biomimetic modification of synthetic hydrogels by incorporation of adhesive peptides and calcium phosphate nanoparticles: in vitro evaluation of cell behavior

“…The major advantage for developing a composite material is the possibility of combining multiple properties associated with the natural tissue. While the polymeric network resembles the architecture of natural ECM, and hence acts as a supportive environment for cell functions (Drury and Mooney, 2003), homogeneously dispersed CaP nanoparticles render the resulting composite osteoconductive, encourage protein adsorption (Kilpadi et al, 2001) and increase matrix stiffness, thereby exerting strong effects on lineage specifi cation and commitment of naive mesenchymal stem cells (Engler et al, 2006).…”

Osseointegration and Bioscience of Implant Surfaces - Current Concepts at Bone-Implant Interface

“…Besides, the rutile-type oxide, which is formed on titanium as a titanium dioxide, is described as a stable crystalline form similar to ceramics in its bioreactive behaviour (Zhao et al, 2005). Although titanium has superior characteristics compared to other implant metals, the ostoconductivity of titanium is lower than calcium phosphate (CaP) based bioceramics (Kilpadi et al, 2001). Therefore, CaP based ceramics are referred to be bone-bonding materials, whereas titanium is a nonbonding material to bone (Hench & Wilson, 1984).…”

“…It has been well established that the Ca-P based coating of titanium favours the bone response compared with the uncoated titanium (Chang et al, 1999a;Wheeler, 1996). Additionally, Ca-P based surfaces bind more attachment proteins, such as fibronectin and vitronectin, for the integrin mediated binding action of osteoprogenitors compared to titanium surfaces (Kilpadi et al, 2001). Several techniques were described for the deposition of Ca-P coatings on titanium implants, including ion beam deposition, plasma spraying, sol-gel methods, laser deposition, radiofrequency sputtering, biomimetic deposition and electrostatic spray deposition (Ong & Chan 2000).…”