Biodegradable polyurethanes for implants. II. In vitro degradation and calcification of materials from poly(ϵ‐caprolactone)–poly(ethylene oxide) diols and various chain extenders

Abstract

Linear, biodegradable, aliphatic polyurethanes with various degrees of hydrophilicity were synthesized in bulk at 50-100 degrees C. The ratios between the hydrophilic and hydrophobic segments were 0:100, 30:70, 40:60, 50:50, and 70:30, respectively. The hydrophilic segment consisted of poly(ethylene oxide) (PEO) diol (molecular weight = 600 or 2000) or the poly(ethylene-propylene-ethylene oxide) (PEO-PPO-PEO) diol Pluronic F-68 (molecular weight = 8000). The hydrophobic segment was made of poly(epsilon-caprolactone) diol (molecular weight = 530, 1250, or 2000). The chain extenders were 1,4-butane diol and 2-amino-1-butanol. The diisocyanate was aliphatic hexamethylene diisocyanate. The polymers absorbed water in an amount that increased with the increasing content of the PEO segment in the polymer chain. The total amount of absorbed water did not exceed 2% for the poly(ester urethane)s and was as high as 212% for some poly(ester ether urethane)s that behaved in water like hydrogels. The polymers were subjected to in vitro degradation at 37 +/- 0.1 degrees C in phosphate buffer solutions for up to 76 weeks. The poly(ester urethane)s showed 1-2% mass loss at 48 weeks and 1.1-3.8% mass loss at 76 weeks. The poly(ester ether urethane)s manifested 1.6-76% mass loss at 48 weeks and 1.6-96% mass loss at 76 weeks. The increasing content and molecular weight of the PEO segment enhanced the rate of mass loss. Similar relations were also observed for polyurethanes from PEO-PPO-PEO (Pluronic) diols. Materials obtained with 2-amino-1-butanol as the chain extender degraded at a slower rate than similar materials synthesized with 1,4-butane diol. All the materials already manifested a progressive decrease in the molecular weight in the first month of in vitro aging. The rate of molecular weight loss was higher for poly(ester ether urethane)s than for poly(ester urethane)s. For poly(ester ether urethane)s, the rate of molecular weight loss was higher for materials containing Pluronic than for those containing PEO segments. All polymers calcified in vitro. The susceptibility to calcification increased with material hydrophilicity. The progressive deposition of calcium salt on the film surfaces resulted in the formation of large crystal aggregates, the structure of which depended on the chemical composition of the calcified material. Needle-like aggregates, resembling brushite, formed on the hydrophobic polyurethane, and plate-like crystals formed on the highly hydrophilic material. The calcium-to-phosphorus atomic ratio of the crystals growing on the samples was dependent on the chemical composition of the material and varied from 0.94 to 1.55.

Synthesis of bio-based thermoplastic polyurethane elastomers containing isosorbide and polycarbonate diol and their biocompatible properties

“…At the same time, the peak around 3324 cm -1 also decreased with decreasing molar ratio of isorsobide. Much attention has been paid to the surface structure and property of polymeric materials, because the functional groups on the surface play an important role in the interactions among materials with biological molecules and cells [29,30]. As shown in Table 2, most of the PUs showed water contact angles < 57°.…”

Poly(butylene 2,5-furandicarboxylate-ε-caprolactone): A new bio-based elastomer with high strength and biodegradability

“…It has been proposed that the ensuing aliphatic ester linkages are vulnerable to enzyme attacks due to increased water uptake. Among aliphatic moieties, ε-caprolactone polyester diol can act as promising soft segments for chain mobility and nontoxicity [21]. It should be noted that the incorporation of ε-caprolactone polyester diol can be simply achieved by using easily-accessible monomer ε-caprolactone, instead of high-price ε-caprolactone polyester diol.…”

Ascorbic Acid in Polyurethane Systems for Tissue Engineering

“…Biodegradable, porous polyurethane (PUR) scaffolds prepared from LDI or lysine-derived components [51][52][53][54][55][56][57][58][59][60][61] and aliphatic isocyanates [62][63][64][65][66][67] [46,[68][69][70][71]. From chemical point of view, by careful selection of diisocyanate, chain extender and macrodiol components, a broad range of polyurethane physical properties can be achieved [46].…”