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)3N+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)3N+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°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.

Design, development, testing at ISO standards and in vivo feasibility study of a novel polymeric heart valve prosthesis

“…However, a recent study shows that a styrenic block copolymer is significantly less prone to calcification in vitro than is a polyurethane valve. 36 Hydrodynamic testing is subject to considerable variation depending on the details of geometry and testing conditions used, i.e. the same valve can give different results when tested in different pulse duplicators under ostensibly similar conditions; for example the shape and flexibility of the outflow pipe affect the EOA measured.…”

The use of polyisobutylene-based polymers in ophthalmology

“…At present, researchers developing medical devices utilizing polyisobutylene-based polymers (stents, glaucoma drainage devices, IOLs, and heart valves [ 9 ]) have found the following: (1) SIBS does not substantially activate platelets in the vascular system [ 9 ]; (2) PMNs in large numbers are not commonly observed around SIBS implants subcutaneously in the vascular system [ 12 ], in implants, or in the eye [ 23 ]; (3) myofibroblasts, scarring, and encapsulation are not clinically significant with SIBS implanted in the eye [ [23] , [24] , [25] , [26] , [27] ]; (4) embrittlement has not been observed in any implant location [ 27 ]; (5) insignificant calcification has been observed within this polymer during in vitro studies [ 52 ] with no reports of calcification of any device from the clinical field; and (6) degradation has not been observed nor reported in any living system to date. Areas where SIBS is deficient include areas in direct contact with fat, where the lipids can absorb into the polymer to plasticize and weaken it.…”

Synthesis of High‐Molecular‐Weight and Strength Polyisobutylene‐Based Polyurethane and Its Use for the Development of a Synthetic Heart Valve

“…We obtained PUs that are likely bioinert, calcification resistant, and whose protein adsorption is less than that of silicone–rubber‐based PUs. [ 3,8 ] These PIB–PUs are designed for biomaterial applications and can be used where earlier PIB–PUs could not be employed, for example, for a fully synthetic heart valve.…”