Morphology of Elastic Poly(l-lactide-co-ε-caprolactone) Copolymers and in Vitro and in Vivo Degradation Behavior of Their Scaffolds

Abstract

Very elastic PLCL [poly(L-lactide-co-epsilon-caprolactone), 50:50] copolymers were synthesized and extruded into porous tubular scaffolds (pore size 150 +/- 50 microm, porosity 90%) for the application to tissue engineering. The copolymers were basically random and amorphous. However, two T(g)'s (glass transition temperatures) were observed in dynamic mechanical thermal analysis and also in differential scanning calorimetry thermograms. Furthermore, microdomains (about 17 nm in size) were indicated on the small-angle X-ray scattering profile and finally confirmed by transmission electron microscopy. Therefore, the PLCL copolymer was probably composed of a soft matrix of mainly epsilon-caprolactone moieties and hard domains containing more L-lactide units to exhibit a rubberlike elasticity in virtue of the physically cross-linked structure. The smooth muscle cells seeded scaffolds were implanted into nude mice subcutaneously for up to 15 weeks to monitor the in vivo degradation. In addition, they were degraded in vitro in phosphate buffer solution (pH 7.4) for up to 1 year to compare the results each other. All the scaffolds degraded slowly in vivo and in vitro even in the form of a highly porous thin membrane. However, the degradation rate was somewhat faster for in vivo than for in vitro. This should be explained by enzymes that might have played a certain role in the degradation in the body. In addition, the epsilon-caprolactone moieties degraded faster than the L-lactide units did in these PLCL scaffolds, although their hydrophilicities are in the opposite order. This behavior appeared more prominently in the in vivo case. This should result from that the amorphous regions composed of mainly epsilon-caprolactone units might have been first attacked by water because water can penetrate into the amorphous regions easier than the hard domains containing more L-lactides.

Microstructure and properties of nano-fibrous PCL-b-PLLA scaffolds for cartilage tissue engineering

“…PCL is in a rubbery state at room temperature due to a low T g (glass transition temperature) and suffers a very slow degradation in vivo. Therefore, PLC or PGC might be promising materials for cartilage reconstruction because the incorporation of PCL could enhance the flexibility of the scaffold, and the degradation could be Nano-fibrous PCL-B-PLLA scaffolds modulated by changing the composition of the copolymer (Jeong et al, 2004;Zhao et al, 2007;Kister et al, 2000;Li et al, 1996). It was also documented that biodegradable polyurethanes based on the PCL and PLLA segments were alternative candidates for cartilage tissue engineering, and that they were degraded to nontoxic by-products in vivo (Gorna et al, 2006).…”

Effect of the Configuration of the Active Center on Comonomer Reactivities: The Case of ε‐Caprolactone/ l,l‐Lactide Copolymerization

“…[1] Thus, CL/LA copolymerization enables the properties of the resulting polyester to be tuned by varying its total composition and the distribution of the comonomer repeat units along the copolymer chain. [3][4][5][6] The homopolymerization rates of CL and LA can also be substantially different. For example, the ratio of the absolute rate constants of propagation, k p (CL)/k p (LA), on aluminum trisalkoxide active species can be as high as 6.…”

“…Prior to the copolymerization studies, we compared the rates of CL and LA homopolymerization initiated with Al(OiPr) 3 and carried out in the presence of an equimolar amount (with regard to Al(OiPr) 3 ) of (S)-2. The corresponding plots in Figure 1 showing the kinetics of CL and LA consumption reveal that the presence of the bulky bidentate ligand on the aluminum alkoxide species results in a decrease in the k p (CL)/k p (LA) ratio to 16.7.…”

“…The described kinetic behavior can be expressed quantitatively in terms of the corresponding reactivity ratios (r CL = k clCL /k clLA and r LA = k lalLA /k laCL , Scheme 1) determined by using the numerical integration method (see the Experimental Section): r CL = 7.2 and r LA = 112. On the other hand, Teyssie et al determined the reactivity ratios r CL = 0.58 and r LA = 17.9 some time ago for the copolymerization initiated with bare Al(OiPr) 3 .…”

Lipase-Catalyzed Ring-Opening Copolymerization of ε-Caprolactone and β-Lactam

“…20,21 It has been utilized in different fields, for instance, in scaffolds for tissue engineering, sutures, orthopedics, microelectronics, drug delivery systems, as adhesive, and in packaging. 21,22 Poly(ε-CL) displays miscibility with other polymers, such as poly(vinyl chloride), poly(styreneco-acrylonitrile), poly(acrylonitrile-co-butadiene-co-styrene), poly(bisphenol A), polycarbonates, nitrocellulose, and cellulose butyrate, and also displays mechanical compatibility with polyethylene, natural rubber, and poly(vinyl acetate). 22 Therefore, copolymerization of ε-caprolactone will be an interesting approach to synthesize new materials with potentially improved thermal or physical properties compared to poly(ε-CL) homopolymer.…”