The use of poly(styrene-block-isobutylene-block-styrene) and analogs for long-term implant applications

The use of polyisobutylene-based polymers in ophthalmology

“…Both in vitro and in vivo testing confirmed the biocompatibility and biostability of SIBS [ 10 , 11 , 23 , 30 ]. At the time of this writing, a drug-eluting coronary stent (TAXUS® Boston Scientific Corporation, Natick, Massachusetts, USA) and a glaucoma device (PRESERFLO® MicroShunt) are the only commercialized implantable medical devices made from SIBS [ 9 ]. TAXUS was the largest product launch in the history of medical devices with sales exceeding $3 billion USD in the first year alone.…”

“…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.…”

“…Similarly, contact with ointments containing parabens should be avoided as they, too, soften the polymer, and SIBS exhibits creep deformation under high static and/or dynamic load. The crosslinked forms of xPIB and xSIBS are not as affected by lipid and paraben absorption, and their static and dynamic creep behavior are much improved [ 9 ]. Polyisobutylene-based polymers have been investigated in other areas of the eye including scleral buckles [ 53 ] and as orbital tissue expanders [ 54 ].…”

“…Preclinical bench testing of the MicroShunt was intensive, as would be expected for a long-term implant and is presented in detail in the literature [ 9 , 22 ]. Briefly, sterilized MicroShunt samples were incubated in distilled water at 37 °C for 14 days.…”

“…The first use of SIBS in medicine was for Boston Scientific Corporation's (Natick, Massachusetts, USA) TAXUS® Drug-Eluting Coronary Stent. The development of TAXUS® is well-documented in the literature [ [9] , [10] , [11] , [12] ] and will not be repeated here.…”