Biomaterial Surface Modifications

Biomaterials exhibit various degrees of compatibility with the harsh environment within a living organism. They need to be nonreactive chemically and physically with the body, as well as integrate when with tissue. The extent of compatibility varies based on the application and material required. Often modifications to the surface of a biomaterial system are required to maximize performance. The surface can be modified in many ways, including plasma modification and applying coatings to the substrate. Surface modifications can be used to affect surface energy, adhesion, biocompatibility, chemical inertness, lubricity, sterility, asepsis, thrombogenicity, susceptibility to corrosion, degradation, and hydrophilicity.

Teflon is a hydrophobic polymer composed of a carbon chain saturated with fluorine atoms. The fluorine-carbon bond is largely ionic producing a strong dipole. The dipole prevents Teflon from being susceptible to Van der Waals forces, so other materials will not stick to the surface. Teflon is commonly used to reduce friction in biomaterial applications such as in arterial grafts, catheters, and guide wire coatings.

PEEK is a semicrystalline polymer composed of benzene, ketone, and ether groups. PEEK is known for having good physical properties including high wear resistance and low moisture absorption and has been used for biomedical implants due to its relative inertness inside of the human body.

Plasma modification is one way to alter the surface of biomaterials to enhance their properties. During plasma modification techniques, the surface is subjected to high levels of excited gases that alter the surface of the material. Plasma's are generally generated with a radio frequency (RF) field. Additional methods include applying a large (~1KV) DC voltage across electrodes engulfed in a gas. The plasma is then used to expose the biomaterial surface, which can break or form chemical bonds. This is the result of physical collisions or chemical reactions of the excited gas molecules with the surface. This changes the surface chemistry and therefore surface energy of the material which affects the adhesion, biocompatibility, chemical inertness, lubricity, and sterilization of the material. The table below shows several biomaterial applications of plasma treatments.

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