Impact of Porosity and Electrolyte Composition on the Surface Charge of Hydroxyapatite Biomaterials

Abstract

The success or failure of a material when implanted in the body is greatly determined by the surface properties of the material and the host tissue reactions. The very first event that takes place after implantation is the interaction of soluble ions, molecules and proteins from the biological environment with the material surface leading to the formation of an adsorbed protein layer that will later influence cell attachment. In this context, the particular topography and surface charge of a material become critical as they influence the nature of the proteins that will adsorb. However, very limited information is available on the surface charge of porous substrates. Only until very recently the determination of the zeta potential on porous membranes has been accurately determined. The goal of this work was to implement the previous findings for the determination of the zeta potential of a series of porous hydroxyapatite (HA) substrates and to assess how porosity affects the measurements. In addition, studies using various electrolytes were also performed to prove how the specific affinity of certain ions for HA can further impact surface charge. The results showed that all materials exhibited very similar external surface charge (~ -23 mV), consistent with their almost identical topographies.However, the presence of interconnected pores underneath the sample surface resulted in an additional internal zeta potential that varied with the porosity content. Measurements with different electrolytes confirmed the selectivity of divalent ions for HA underlying the importance of testing biomaterials using relevant electrolytes.3

Characterization of pulp derived nanocellulose hydrogels using AVAP® technology

“…Understanding and manipulating surface charge is critical for most applications involving material-aqueous interfaces, such as protein adsorption, biofilm formation, drug delivery and biodistribution. In the biomaterials context, surface charge at the solid/water interface determines the electrostatic interaction between the biomaterial surface and the soluble ions, molecules and proteins from the biological environment, leading to the formation of an adsorbed protein layer that influences cell adhesion (Espanol, Mestres, Luxbacher, Dory, & Ginebra, 2016). Negatively charged biomaterials are less likely to be internalized by cells than those that are neutral or positively charged when other parameters such as shape and size of the nanoparticles are comparable (L. Chen, McCrate, Lee, & Li, 2011).…”

Applicability of electro-osmotic flow for the analysis of the surface zeta potential

“…Surface zeta potential (SZP) analysis is a vital method for qualifying important features of new materials in technical (e.g., effects of fouling and cleaning of membranes used for water treatment, 3,4 textile industry [5][6][7] ) and biomedical applications (e.g. biolm formation, haemocompatible implants [8][9][10][11] ). Furthermore, it enables to gain insights into modication processes that result from surface treatment or surface interactions with biological or natural environments under near-ambient conditions.…”

Fabrication of Biocompatible Potassium Sodium Niobate Piezoelectric Ceramic as an Electroactive Implant

“…Polarized HA works like a capacitor that charged by applying a high level electric field (kV/mm) at elevated temperature (>200 °C) [15,16,17]. Polarized HA has, in some cases, a positive effect on biological responses, as several studies have reported that the polarized HA exhibited favorable bio-mineralization property and protein adsorption behavior [15,18,19,20,21]. However, its non-piezoelectricity and extremely low depolarization, current density below 200 °C [15] limited its application in environment in vivo.…”