Surface analysis of human plasma fibronectin adsorbed to commercially pure titanium materials

Abstract

Protein binding on metallic implant surfaces, such as titanium, is governed by the physico-chemical nature of the metallic surface. Human plasma fibronectin (HPF) is an important matrix glycoprotein that mediates cell and protein attachment to each other or to the extracellular matrix present during wound healing. The objective of this study was to investigate the adsorption of HPF onto polished commercially pure titanium (cpTi) by using atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA) and to measure the resultant surface contact angle before and after HPF binding. Two types of cpTi disks, one highly polished in our laboratory (HSS) and one commercially prepared (31), were reacted with HPF solutions of varying concentrations (1 microg/mL-10 ng/mL). ESCA survey spectra of samples coated with 1 microg/mL of fibronectin showed an increase in organic nitrogen and carbon compared with uncoated controls. Contact angle measurements of HSS and 31 cpTi disks showed no significant difference in average contact angle (36.3 degrees +/- 3.5 and 39.1 degrees +/- 3.1) despite differences in local root mean square (RMS) surface roughness (4.45 +/- 0.46 nm and 22.37 +/- 4.17 nm) as measured by AFM. Images obtained by AFM showed that 31 specimens were more irregular, with large parallel polishing grooves. Adsorbed HPF appeared in a globular form with an average length of 16.5 +/- 1.0 nm, a height of 2.5 +/- 0.5 nm, and a width of 9.6 +/- 1.2 nm. Fibronectin coating on both HSS and 31 cpTi specimens resulted in a significant increase in hydrophobicity compared to uncoated specimens. These results indicate the significance of HPF on cpTi and may explain how cpTi implants function in situ.

Exploiting fluorescence resonance energy transfer to probe structural changes in a macromolecule during adsorption and incorporation into a growing biomineral crystal

“…Fn has a diameter of 20–30 nm in its compact globular form and after complete arm separation, and approximate length of 120–160 nm with a diameter of 2.5–3 nm as probed here by AFM (Fig. 2D-G) and reported in the literature [59,63,64,72,73]. AFM measurements of the (–101) face of COM have revealed wide (≈200 nm) stepped terraces with an average step height of 0.65 ± 0.23 nm, a value within the range of the elemental step height (∼6Å) [62,74].…”

“…The residual acceptor peak at 8 M GdnHCL was due to direct excitation of the acceptor since the raw spectra as monitored on the microscope stage are reported uncorrected for residual cross-talk between the excitation and emission channel. As supported by circular dichroism spectra [35,41,44,63,64], Fig. 1D shows putative Fn conformations in solution [44], from the compact conformation in solution or the blood, to a partially extended structure that results when the intramolecular electrostatic interactions that stabilize the contact between the crossed-over dimer arms of Fn are broken by competing ions, to, finally, partially denatured states.…”

Surface oxide net charge of a titanium alloy: Modulation of fibronectin-activated attachment and spreading of osteogenic cells

“…Another important aspect of the behavior of proteins that may be affected by surface chemistry is their capacity to undergo structural rearrangements upon adsorption to a substrate. A number of environmental and surface variables, such as ionic strength, pH, temperature, surface charge and surface hydrophilicity have been shown to modulate the three-dimensional structure of fibronectin upon binding to a substrate [5,25,38-46]. The conformation of adsorbed proteins can be highly influenced by the hydrophobicity of the material surface, since protein binding to highly nonpolar surfaces results in drastic conformational changes and loss of activity due to severe unfolding of the protein [18-20].…”

In vitro comparison of two titanium dental implant surface treatments: 3M™ESPE™ MDIs versus Ankylos®

“…MacDonald et al have shown that wettability, i.e., hydrophilic surfaces support cell interactions and biological fluids better than the hydrophobic surfaces [38]. It has also been shown that roughening the titanium surface improves hydrophilicity [38].…”

“…It has also been shown that roughening the titanium surface improves hydrophilicity [38]. In addition, many authors have stated that rougher surfaces promote differentiation, growth and attachment of bone cells, and higher production of growth factors and augment mineralization [39–43].…”