A comparative study of polyethylene terephthalate surface carboxylation techniques: Characterization, in vitro haemocompatibility and endothelialization

Surface functionalization of polymers is crucial for improving biocompatibility and haemocompatibility, which correlates to improved performance of medical devices. Here, we have evaluated the effect of four PET surface carboxylation techniques on the antifouling property, haemocompatibility, and endothelialization. Surface carboxylation was achieved by formaldehyde + bromoacetic acid treatment (PET-1[COOH]), methacrylic acid grafting (PET-2[COOH]), NaOH hydrolysis + KMnO4 oxidation (PET-3[COOH]), and oxygen plasma treatment + acrylic acid grafting (PET-4[COOH]). The carboxyl densities on these surfaces were 0.4, 23.2, 31.9, 16.4 nmol/cm2, respectively. XPS and FTIR spectroscopy confirmed the introduction of carboxyl groups. Water contact angle results showed that hydrophilicity increased with an increase in surface carboxyl density. SEM images confirmed that these modifications didn't cause any surface deterioration. AFM studies showed an increase in surface roughness of the carboxylated PET. Tensile testing showed that these modifications did not affect the bulk properties. Compared to control, PET-3[COOH] has a 9-fold reduction in BSA adsorption. Haemocompatibility studies showed significantly reduced %hemolysis and platelet adhesion on the carboxylated PET. Cell culture studies revealed that endothelial cell (EA.hy926) attachment increased with increase in surface carboxyl density. PET-3[COOH] showed the most improved haemocompatibility and endothelial cell attachment. These results clearly show that the method of functionalization has a significant impact on the haemocompatibility and cell attachment.