Implantable and Degradable Thermoplastic Elastomer

Abstract

Biodegradable and implantable materials having elastomeric properties are highly desirable for many biomedical applications. Here, we report that poly­(lactide)-co-poly­(β-methyl-δ-valerolactone)-co-poly­(lactide) (PLA-PβMδVL-PLA), a thermoplastic triblock poly­(α-ester), has combined favorable properties of elasticity, biodegradability, and biocompatibility. This material exhibits excellent elastomeric properties in both dry and aqueous environments. The elongation at break is approximately 1000%, and stretched specimens completely recover to their original shape after force is removed. The material is degradable both in vitro and in vivo; it degrades more slowly than poly­(glycerol sebacate) and more rapidly than poly­(caprolactone) in vivo. Both the polymer and its degradation product show high cytocompatibility in vitro. The histopathological analysis of PLA-PβMδVL-PLA specimens implanted in the gluteal muscle of rats for 1, 4, and 8 weeks revealed similar tissue responses as compared with poly­(glycerol sebacate) and poly­(caprolactone) controls, two widely accepted implantable polymers, suggesting that PLA-PβMδVL-PLA can potentially be used as an implantable material with favorable in vivo biocompatibility. The thermoplastic nature allows this elastomer to be readily processed, as demonstrated by the facile fabrication of the substrates with topographical cues to enhance muscle cell alignment. These properties collectively make this polymer potentially highly valuable for applications such as medical devices and tissue engineering scaffolds.

Understanding the Interfacial Adhesion between Natural Silk and Polycaprolactone for Fabrication of Continuous Silk Biocomposites

“…18 Compared with the glassy and rigid PLA at room temperature, PCL exhibits a softer rubbery consistency and much easier processability. 14 Screw-extrusion fabrication of PCL reinforced with 30 silk microparticles almost doubled the compressive modulus compared to that of unreinforced PCL. 15 Similar results have also been found for the effect of the silk content on the tensile/ flexural strength of reinforced PCL composites.…”

“…13 However, there are still concerns about the in vivo biomedical use of polyesters due to their insufficient mechanical properties and tissue compatibility. 14 Where silk fibers have been introduced as a dispersing phase to reinforce and toughen polyesters such as PLA, PCL, PBS, and PLA/CL, additional improvements in biocompatibility have also been reported. 15−20 There are examples in the literature where silk nanofibers, microfibers, and (0.5−12.7 mm long) chopped fibers have been used as reinforcements.…”

“…Where silk fibers have been introduced as a dispersing phase to reinforce and toughen polyesters such as PLA, PCL, PBS, and PLA/CL, additional improvements in biocompatibility have also been reported. − There are examples in the literature where silk nanofibers, microfibers, and (0.5–12.7 mm long) chopped fibers have been used as reinforcements. − In a PLA composite, for example, adding 5 wt % of ∼5 mm long silk fibers to PLA resulted in respective increases in the elastic modulus and tensile ductility by 53 and 39% . Compared with the glassy and rigid PLA at room temperature, PCL exhibits a softer rubbery consistency and much easier processability . Screw-extrusion fabrication of PCL reinforced with 30 wt % silk microparticles almost doubled the compressive modulus compared to that of unreinforced PCL .…”

“…For example, polyesters are a family of biopolymers with characteristic ester bonds that include a number of well-known commercialized and certified compounds for medical use . However, there are still concerns about the in vivo biomedical use of polyesters due to their insufficient mechanical properties and tissue compatibility . Where silk fibers have been introduced as a dispersing phase to reinforce and toughen polyesters such as PLA, PCL, PBS, and PLA/CL, additional improvements in biocompatibility have also been reported. − There are examples in the literature where silk nanofibers, microfibers, and (0.5–12.7 mm long) chopped fibers have been used as reinforcements. − In a PLA composite, for example, adding 5 wt % of ∼5 mm long silk fibers to PLA resulted in respective increases in the elastic modulus and tensile ductility by 53 and 39% .…”

Bio-Based Poly(lactic acid)/Poly(butylene sebacate) Blends with Improved Toughness

“…The copolymerization of L -lactide with different monomers emerged as another attractive technique to obtain PLA-based materials with increased flexibility and toughness [ 28 ]. In this sense, comonomers such as glycolide, ethylene glycol, ε-caprolactone, δ-valerolactone [ 29 ], β-methyl-δ-valerolactone [ 30 ], 1,5-dioxepan-2-one [ 31 ], 1,3-trimethylene carbonate [ 29 ], and ethylene carbonate [ 32 ] have been studied over time. The limitations of the copolymerization method are related to the long reaction times, high costs, difficulty in establishing and controlling the reaction conditions (reaction temperature and time, comonomer feed ratio, type of catalyst, amount of catalyst, etc.)…”