Polymers are widely utilized in medical devices due to their low cost, biological and chemical stability, and processability. The polymer material is typically chosen based on its mechanical properties rather than surface chemistry. Surface chemistry, however, plays a significant part in terms of interactions with the human tissue.
One of the properties closely associated with material-tissue interactions is the wettability of the material. The surface hydrophobicity is linked to poor protein resistance which in turn initiates a thrombosis cascade and bacterial infection [1]. Reduced protein fouling of a surface is likely to reduce both bacterial and mammalian cell adhesion [2]. Hydrophilicity will also help the water to wet the surface better which is especially important in applications like catheters as the water layer present can act as a lubricant. Unfortunately, many of the most used polymers are hydrophobic and thus prone to nonspecific protein adsorption.
One commonly used method to modify the surface of the polymer is hydrophilic coatings. The most utilized techniques are physical adsorption, hydrogel network formation, surface grafting, and layer-by-layer deposition (LbL). Poly(ethylene glycol) (PEG) and poly(ethylene oxide) (PEO) are examples of commonly used coating materials. Physisorption is the simplest coating strategy but is not stable enough in long-term applications. Techniques relying on covalent bonding offer more long-term stability.
The hydrophilicity of the material can be determined by water contact angle measurements. Typically, a small, around a few microliters drop, is placed on the sample surface, and the contact angle is optically determined. The measurement is very simple to conduct and takes only a few minutes starting from sample placement to the results.
If you would like to read more about contact angle measurements on biomedical applications, please download the white paper through the link below.
Susanna is an Application Scientist at Biolin Scientific. In her PhD thesis, she developed fabrication methods for a new type of inorganic-organic polymers. Microfabricated polymer chips were utilized as tool for biomolecule separation in analytical chemistry.
