Wettable phosphorylcholine-containing polymers useful in blood filtration.

The use of phosphorylcholine (PC)-containing polymers has long been acknowledged as a method to improve the haemocompatibility of blood contacting devices. Such polymers were investigated for coating leukocyte filters, as a means of preserving precious platelet numbers and function. It was demonstrated that by use of such coated filters, the platelet recovery could be significantly increased by some 30%. This was however, balanced by a decrease in the leukocyte removal efficiency of the filter. More problematic however, was the poor critical wetting surface tension (CWST) of the filter (45 mNm(-1)). This was due to the surface expression of the hydrophobic groups of the polymer in air. In order to obtain a filter that could be immediately wetted by the blood and hence remove the need for any detrimental priming of the filter, the PC polymer was modified in order to reduce its hydrophobic content. A series of new cross-linkable polymers was developed that contained other hydrophilic monomers, yet could film-form to produce a coating stable to fluid contact. These materials demonstrated the required wetting characteristics (a CWST of >78 mNm(-1)), whilst retaining the excellent blood-contacting properties.