Electrostatic interactions as a predictor for osteoblast attachment to biomaterials

Abstract

The present study utilizes zeta (zeta)-potential analysis as an indicator of bonding of osteoblasts and whole bone to various biomaterials. Common metal alloys (316L stainless steel, CoCrMo, and Ti6Al4V) and bioceramics (hydroxyapatite and beta-tricalcium phosphate) used in orthopedic applications were suspended in particulate form in physiologic saline, both as-received and supplemented with bovine serum albumin (BSA). Metal alloys were also treated with NaOH washing to study the effect of such a surface treatment on the zeta-potential. The NaOH wash was found to increase the zeta-potential for CoCrMo and Ti6Al4V, but there was a decrease in the magnitude of the zeta-potential for 316L stainless steel. When the metal alloy powders were suspended in BSA-supplemented physiologic saline, the zeta-potential as a function of pH increased, thereby increasing the electronegativity gap and increasing the propensity for bonding between each of the metal alloys and bone. This increase is likely due to matrix proteins in the BSA, which adsorb onto the metal alloy surfaces, promoting bone growth. With the addition of BSA to each bioceramic system, a uniform decrease in zeta-potential was observed. However, the electronegativity gap remained large in each case, maintaining the anticipation of bonding. zeta-Potential analysis is an effective predictor of biomaterial attraction to osteoblasts and bone, providing a useful in vitro method for predicting such interactions.

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

“…If that were true, the process would be diffusion-or surface-reaction-controlled and consequently highly dependent on temperature and pH, which has indeed been experimentally confirmed. It was also shown that washing the precipitate at the stage where it is still amorphous increases the final Ca/P ratio because of removing the acidic layers of H x PO xÀ3 4 ions surrounding the growing particles (as already mentioned, it appears that H x PO xÀ3 4 ions are more effectively absorbed onto HAP particles than Ca 2þ , and can be therefore used for manipulating their f-potential 202,203 and thus controlling the efficiency of adsorption of biomolecules and cells thereto 204 ), thereby validating the effect of exchange of ions between the solution and the precipitate on the final identity of the latter.…”

Silicon addition to hydroxyapatite increases nanoscale electrostatic, van der Waals, and adhesive interactions

“…The larger adhesion forces observed for SiHA could be due to its larger Hamaker constant versus HA and could play a role in the bone-biomaterial bonding. The greater attractive van der Waals force for SiHA could help overcome the electrostatic double-layer repulsion of osteoblasts with negatively charged cell membrane surfaces (e.g., surface potentials of MC3T3-E1 mouse osteoblasts suspended in physiological saline were measured through ultrasonic attenuation spectroscopy to vary from Ϫ29.4 to Ϫ52.4 mV at pH 7.3-7.5) 47 and the net negative charge of most serum proteins. 48 In general, adhesion interactions have contributions from surface forces such as van der Waals, surface charge, and hydrophobicity as well as surface topology, which can be difficult to deconvolute.…”

Adhesion of osteoblasts to a nanorough titanium implant surface

“…16,23,24 Since osteoblasts are negatively charged, 25 they are electrostatically repelled by the negatively charged titanium surface as long as some other attractive forces are not present in the system. Recently, a possible mechanism of osteoblast adhesion to the implant surface was proposed on the assumption that positively charged proteins 25,26 or proteins with positively charged tips, ie, a quadrupolar internal charge distribution 15 attached to the negatively charged implant surface, serve as a substrate for the subsequent attachment of negatively charged osteoblasts. In order to predict the orientation of proteins with positively charged tips near a charged implant surface, Monte Carlo simulations of the distribution and the orientation of charged spheroidal proteins in the vicinity of a charged titanium surface were performed.…”