Calcification resistance of polyisobutylene and polyisobutylene-based materials

Abstract

Calcification of implanted biomaterials is highly undesirable and limits clinical applicability. Experiments were carried out to assess the calcification resistance of polyisobutylene (PIB), PIB-based polyurethane (PIB-PU), PIB-PU reinforced with (CH3)(3)N+CH2CH2CH2NH2 I--modified montmorillonite (PIB-PU/nc), PIB-based polyurethane urea (PIB-PUU), PIB-PU containing S atoms (PIBS-PU), PIBS-PU reinforced with (CH3)(3)N+CH2CH2CH2NH2 I--modified montmorillonite (PIBS-PU/nc), and poly(isobutylene-b-styrene-b-isobutylene) (SIBS), relative to that of a clinically widely implanted polydimethylsiloxane (PDMS)-based PU, Elast-Eon (the "control"). Samples were incubated in simulated body fluid for 28 days at 37 degrees C, and the extent of surface calcification was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and Fourier-transform-infrared (FT-IR) spectroscopy. Whereas the PDMS-based PU showed extensive calcification, PIB and PIB-PU containing 72.5% PIB, ie, a polyurethane whose surface is covered with PIB, were free of calcification. PIBS-PU and PIB-PUU, ie, polyurethanes that contain S or urea groups, respectively, were slightly calcified. The amine-modified montmorillonite-reinforcing agent reduced the extent of calcification. SIBS was found slightly calcified. Evidently, PIB and materials fully coated with PIB are calcification resistant.