A novel degradable polycaprolactone networks for tissue engineering
Introduction
Polycaprolactone (PCL), a semi-crystalline linear resorbable aliphatic polyester, is subjected to biodegradation because of the susceptibility of its aliphatic ester linkage to hydrolysis. The products generated are either metabolised via the tricarboxylic acid (TCA) cycle or eliminated by direct renal secretion. Extensive in vitro and in vivo biocompatibility and efficacy studies have been performed, resulting in US Food and Drug Administration approval of a number of medical and drug delivery devices [1], [2], [3], [4]. At present, PCL is regarded as a soft and hard-tissue compatible material including resorbable suture, drug delivery system, and recently bone graft substitutes. However, applications of PCL might be limited because degradation and resorption kinetics of PCL are considerably slower than other aliphatic polyester due to its hydrophobic character and high crystallinity.
PCL is one of biomaterial used in bone repair. Marra et al. [5] reported that PCL is a comparable substrate for supporting cell growth resulting from two-dimensional bone marrow stramal cell culture. And, PCL/PLA blend disc incorporated with hydroxyapatite is feasible as scaffolds for bone tissue engineering. Heath et al. [6] tested the coating effect of tissue transglutaminase on the surface of PCL to enhance biocompatibility of PCL. Tissue transglutaminase is a novel cell surface adhesion protein that binds with high affinity to fibronectin in pericellular matrix.
In this study, a novel PCL macromer was synthesized through the reaction of PCL diol with acryloyl chloride to enhance degradability. Three-dimensional gels were formed by photopolymerization of PCL macromer, which has the potential to be used as scaffold and drug delivery matrix. The synthesis of PCL macromer and PCL networks were confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). Differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) were performed. Degradation studies were performed in phosphate buffered saline (PBS). The mechanical properties and compressive recovery ratio were examined, too. Morphology of PCL networks was observed using scanning electron microscopy. The cell attachment onto PCL networks was examined by using osteoblast cell.
Section snippets
Materials
Hydroxyl end functionalized PCL diols with molecular weights of 530, 1250, and 2000, acryloyl chloride, triethylamine, and PCL (MW=65,000) supplied by Aldrich Chemical Corporation (Milwaukee, WI) were used. All other chemicals used were of reagent grade and were utilized without further purification.
Synthesis of PCL macromer and PCL networks
The procedure of PCL macromer synthesis was illustrated in Fig. 1. PCL diols, which were themselves α- and ω-terminated by hydroxyl groups, were end-capped with acrylated groups to form a
Results and discussion
PCL macromer was synthesized by the reaction of PCL diol with acryloyl chloride as shown in Fig. 1. The FTIR spectra of PCL diol and PCL macromer were shown in Fig. 2. PCL macromer showed absorption bands at 1635 and 813 cm−1 assigned to the CC due to acrylation of PCL diol. Those peaks were not observed in PCL diol itself (Fig. 2). The absorption bands at 1723 and 1110 cm−1, which were present in both PCL diol and PCL macromer, were attributed to ester and ether stretching peaks, respectively.
Conclusions
PCL diol was modified with acryloyl chloride to form a PCL macromer that was easily crosslinked via photopolymerization. Thermal stability of three-dimensional PCL networks was higher than that of PCL diol. However, weight average degree of crystallinity of PCL networks was much lower than that of PCL diol due to the increased crosslinking density. The compressive modulus and compressive recovery ratio of PCL networks showed 6.90 MPa and 66.7%, respectively, which were higher than those of PCL
Acknowledgements
This work was supported by Korea Research Foundation Grant (KRF-2001-042-E00062).
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