Interactions of ADP-stimulated human platelets with PEGylated polystyrene substrates prepared by surface amidation

A study primarily focused on the interactions between ADP-stimulated human platelets and PEGylated polystyrene substrates is described in this paper. The platelet–surface interactions were investigated using colorimetric acid phosphatase assay. Two types of amine-containing polymeric hydrogel materials based on poly(ethylene glycol) (PEG), H₂N–PEG–OCH₃ and H₂N–PEG–NH₂, were used to PEGylate polystyrene surfaces derivatized with maleic anhydride by amidation at alkaline pH. In addition, comparative studies using surfaces non-covalently adsorbed by bovine serum albumin (BSA) or fibrinogen (Fg) were also conducted. The assay results showed that no significant platelet adhesion was observed when PEGylated surfaces or BSA-coated surfaces were exposed to unstimulated gel-filtered platelets (GFP). However, upon ADP-stimulation, platelet adhesion to the surfaces under investigation in this study all increased to varying degrees. Most importantly, the results showed that polystyrene surfaces PEGylated using H₂N–PEG–NH₂ were most effective in resisting platelet adhesion when assays were performed using ADP-stimulated GFP. By PEGylating the surfaces of polystyrene microtiter wells via the amidation reaction described in this paper, it is demonstrated that (i) higher degree of surface PEGylation is favored at more alkaline pH and (ii) polystyrene substrates capable of more effectively resisting the adhesion of ADP-stimulated GFP can be obtained by the PEGylation reaction carried out at pH 9.1 using H₂N–PEG–NH₂.