Race for the Surface: Surface Zeta Potential Analysis of Implants

Modern medicine uses countless implants every day. For the body to accept the implant, the material’s biocompatibility is important. Depending on the surfaces’ properties, either the body's own cells or microorganisms win the "race for the surface". This application report focuses on how the surface treatment of titanium affects the streaming potential and protein adsorption.

In biomedical applications, solid materials need to be characterized in terms of their functional groups at the outermost surface. Mainly four properties influence the biocompatibility:

  • Charge in aqueous environment (surfacecharge)
  • Hydrophilicity (wettability)
  • Roughness
  • Chemical composition

The interface between the biomaterial’s surface and the surrounding physiological fluid determines the compatibility with its environment. However, the seinterfacial properties are difficult to characterize and are commonly derived from separate analyses of solid surface and liquid phase. A method that allows biomaterial analysis under real life conditions is surface zeta potential analysis by means of streaming potential or current measurement.

For investigating the streaming potential or streaming current, the surface gets contact with an electrolyte solution, which is typically a diluted salt solution (e.g.1 mmol/l KCl). Due to acidic or basic interactions charges are formed, which lead to a dissociation of acidic surface groups and a protonation of basic groups on the surface. Negative surface charge leads to a negative zeta potential, and positive surface charge leads to a positive zeta potential. However, the zeta potential is a parameter that cannot be measured directly, but an electrokinetic effect needs to be used which is called the streaming potential.

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