Blood response to plasticized poly(vinyl chloride): dependence of fibrinogen adsorption on plasticizer selection and surface plasticizer level

The high level of plasticizer in plasticized poly(vinyl chloride) (PVC) ensures that plasticizer selection has an important influence on the suitability of PVC to function in blood-contacting applications. In this study, three types of plasticized PVC in sheet form, with di-(2-ethylhexyl)phthalate (DEHP), tri-(2-ethylhexyl)trimellitate (TEHTM) and n-butyryltri-n-hexyl citrate (BTHC) as plasticizer, were selected for assessment and single solute fibrinogen adsorption was utilized as an initial index of interactions with blood components. Fibrinogen adsorption behavior shows a strong dependence on the plasticizer selection, plasticizer level at the surface and the adsorption conditions, such as adsorption time and fibrinogen solution concentration. Results indicate that BTHC plasticized PVC possesses the lowest adsorption capacity in the three types of plasticized PVC, while TEHTM plasticized PVC seems to have the strongest reactivity in certain fibrinogen solution concentrations. The alteration of surface plasticizer level was achieved by a methanol-cleaning treatment with a variety of cleaning times and the fibrinogen adsorption on plasticized PVC decreases with the reduction of surface plasticizer level. The migration behavior of two phthalate esters (DEHP and TEHTM) was evaluated using UV-Spectrophotometer to determine the plasticizer level at the surfaces. In addition, the fibrinogen adsorption mechanism was examined with Freundlich adsorption modeling