Polyisobutylene-Based Thermoplastic Elastomers for Manufacturing Polymeric Heart Valve Leaflets: In Vitro and In Vivo Results

Abstract

Superior polymers represent a promising alternative to mechanical and biological materials commonly used for manufacturing artificial heart valves. The study is aimed at assessing poly(styrene-block-isobutylene-block-styrene) (SIBS) properties and comparing them with polytetrafluoroethylene (Gore-texTM, a reference sample). Surface topography of both materials was evaluated with scanning electron microscopy and atomic force microscopy. The mechanical properties were measured under uniaxial tension. The water contact angle was estimated to evaluate hydrophilicity/hydrophobicity of the study samples. Materials’ hemocompatibility was evaluated using cell lines (Ea.hy 926), donor blood, and in vivo. SIBS possess a regular surface relief. It is hydrophobic and has lower strength as compared to Gore-texTM (3.51 MPa vs. 13.2/23.8 MPa). SIBS and Gore-texTM have similar hemocompatibility (hemolysis, adhesion, and platelet aggregation). The subcutaneous rat implantation reports that SIBS has a lower tendency towards calcification (0.39 mg/g) compared with Gore-texTM (1.29 mg/g). SIBS is a highly hemocompatible material with a promising potential for manufacturing heart valve leaflets, but its mechanical properties require further improvements. The possible options include the reinforcement with nanofillers and introductions of new chains in its structure.

Aspects of the Synthesis of Poly(styrene-block-isobutylene-block-styrene) by TiCl4-Co-initiated Cationic Polymerization in Open Conditions

“…In a previous work [8], we have demonstrated that for the synthesis of triblock copolymer of isobutylene and styrene (SIBS, M n = 33,000 g mol −1 , Ð = 1.30) in open conditions (without using of glovebox), the slightly higher concentrations of TiCl 4 (59 mM vs. 40 mM [20]) and proton trap (5.8 mM vs. 3.8 mM) need to be used for providing comparable reaction rate and crossover efficiency during block copolymer preparation. This could be explained by a much higher amount of adventitious H 2 O in the system when the preparation of block copolymer is performed in open conditions as compared to the glovebox technique.…”

“…Besides good mechanical properties, SIBS also has the advantage of a completely saturated polyisobutylene mid-block that yields superior thermal, oxidative stability, and gas barrier properties [1][2][3][4]. Moreover, SIBS is biostable as well as bio-and hemocompatible that makes it perfect candidate for medical applications [3,[5][6][7][8]. Particularly, SIBS was used as coatings on metallic stents [5,7], carrier for a drug-eluting coronary stents [5,7], ophthalmic implants [5][6][7], artificial vascular graft [6,9], etc.…”

Biocompatible Nanocomposites Based on Poly(styrene-block-isobutylene-block-styrene) and Carbon Nanotubes for Biomedical Application

“…The polymerization was conducted under inert argon according to [ 17 ]. Then, 38.6 mg dicumyl chloride (initiator, 0.167 mmol) was dissolved in 107 mL methylcyclohexane/methylene chloride mixture (3:2) followed by the addition of 0.161 mL (1.39 mmol) 2,6-dimethylpyridin.…”

“…Here, we synthesized poly(styrene- block -isobutylene- block -styrene) (SIBS), a biomaterial demonstrating high biocompatibility [ 16 ] yet limited tensile strength [ 17 ], to further modify its structure with CNTs at different concentrations. The resulting nanocomposite films were subjected to a uniaxial tension test followed by analyses of hydrophobicity, electric conductivity, and cytotoxicity.…”

Block Copolymer Synthesis by the Combination of Living Cationic Polymerization and Other Polymerization Methods

“…In 1997, Coca and Matyjaszewski reported block copolymers preparation of styrene (St) and IB, i.e., P(St-b-IB-b-St) ( P1 ) by combination of cationic and ATRP, where both St and IB monomers are capable of undergoing polymerization by living cationic techniques. A recent study proves P(St-b-IB-b-St) ( P1 ) is highly hemocompatible and can be used as heart valve leaflets in near future ( Table 1 ) ( Ovcharenko et al, 2019 ). Researchers have also studied surface mobility of heparin by synthesizing functional dendritic PIB-based thermoplastic elastomer by styrene (St) and IB copolymer ( Wu et al, 2018 ).…”