Biomaterial surface modifications

The surface can be modified in many ways, including plasma modification and applying coatings to the substrate.

Teflon is a hydrophobic polymer composed of a carbon chain saturated with fluorine atoms.

The dipole prevents Teflon from being susceptible to Van der Waals forces, so other materials will not stick to the surface.

[2] Teflon is commonly used to reduce friction in biomaterial applications such as in arterial grafts, catheters, and guide wire coatings.

PEEK is known for having good physical properties including high wear resistance and low moisture absorption [3] and has been used for biomedical implants due to its relative inertness inside of the human body.

Additional methods include applying a large (~1KV) DC voltage across electrodes engulfed in a gas.

This is the result of physical collisions or chemical reactions of the excited gas molecules with the surface.

[4] Abbreviations used in table: PC: polycarbonate, PS: polystyrene, PP: polypropylene, PET: poly (ethylene terephthalate), PTFE: polytetrafluoroethylene, UHMWPE: ultra high molecular weight PE, SiR: silicone rubber The surface energy is equal to the sum of disrupted molecular bonds that occur at the interface between two different phases.

Surface modification techniques have been extensively researched for the application of adsorbing biological molecules.

Covalent attachment to a substrate is necessary to immobilize polysaccharides, otherwise they will rapidly desorb in a biological environment.

This can be a challenge due to the fact that the majority of biomaterials do not possess the surface properties to covalently attach polysaccharides.

This reaction converts anhydroglucopyranoside subunits to cyclic hemiacetal structures, which can be reacted with amine groups to form a Schiff base linkage (a carbon-nitrogen double bond).

Contamination layers are usually limited to a monolayer or less of atoms and are thus only detectable by surface analysis techniques, such as XPS.

Glow discharge plasma treatment is a technique that is used for cleaning contamination from biomaterial surfaces.

Coatings are used in many applications to improve biocompatibility and alter properties such as adsorption, lubricity, thrombogenicity, degradation, and corrosion.

In general, the lower the surface tension of a liquid coating, the easier it will be to form a satisfactory wet film from it.

[10] More specifically whether a liquid coating will spread across a solid substrate can be determined from the surface energies of the involved materials by using the following equation:

Up until ~1950 it was thought that coatings act as a physical barrier which disallows moisture and oxygen to contact the metallic substrate and form a corrosion cell.

It has since been discovered that corrosion protection of steel depends greatly upon the adhesion of a noncorrosive coating when in the presence of water.

[13] Guide wires are commonly made from stainless steel or Nitinol and require polymer coatings as a surface modification to reduce friction in the arteries.

Hydrophilic coatings can reduce friction in the arteries by up to 83% when compared to bare wires due to their high surface energy.

[14] When the hydrophilic coatings come into contact with bodily fluids they form a waxy surface texture that allows the wire to slide easily through the arteries.

[15] The thrombogenicity is due to the proteins in the blood adapting to the hydrophobic environment when they adhere to the coating.

Because most guide wires' core materials are stainless steel they are not capable of being imaged with an MRI.

An alternative that is being examined is to replace contemporary guide wires with PEEK cores, coated with iron particle embedded synthetic polymers.