No abstract

A novel self-cross-linkable and biodegradable macromer, poly(caprolactone fumarate) (PCLF), has been developed for guided bone regeneration. This macromer is a copolymer of fumaryl chloride, which contains double bonds for in-situ cross-linking, and poly(epsilon-caprolactone), which has a flexible chain to facilitate self-cross-linkability. PCLF was characterized with Fourier transform infrared spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Porous scaffolds were fabricated with sodium chloride particles as the porogen and a chemical initiation system. The PCLF scaffolds were characterized with scanning electron microscopy and micro-computed-tomography. The cytotoxicity and in vivo biocompatibility of PCLF were also assessed. Our results suggest that this novel copolymer, PCLF, is an injectable, self-cross-linkable, and biocompatible macromer that may be potentially used as a scaffold for tissue engineering applications.

In an effort to develop various controllable biomaterials, a series of novel cross-linkable and biodegradable multiblock poly(propylene fumarate-co-caprolactone) [P(PF-co-CL)] copolymers have been synthesized via a three-step polycondensation of oligomeric polypropylene fumarate (PPF) with polycaprolactone (PCL) diols. The chemical structures of 15 copolymers with various PCL compositions and segment lengths were further characterized by FTIR, 1 H NMR, and 13 C NMR spectra. Their physical and rheological properties have been determined extensively. The composition dependences of various characteristic temperatures such as glass transition temperature T g, melting temperature Tm, and thermal degradation temperature Td were demonstrated using a phase diagram. Together with DSC results, polarized optical microscopical graphs of several copolymers with high PCL compositions show spherulite crystalline structure. Particularly a banded spherulite has been found for a copolymer with a PCL composition of 87% when it crystallizes at room temperature. When the PCL composition in these copolymers is lower than 70%, the copolymers are amorphous with a reduced T g. This is critical for an enhanced rate of biodegradation. Because of the flexibility of PCL segments in the copolymers, P(PF-co-CL) can be either self-cross-linked or photocross-linked without using any cross-linker. The unentangled characteristics have been verified by the melt viscosity's molecular weight dependence and the master curves of storage modulus G′ and loss modulus G′′. The introduction of PCL into the copolymer chain enhances the solubility in toluene. Dilute solution viscometry shows the effect of microstructure in intrinsic viscosity while this effect is insignificant in melt viscosity. Therefore, the physical properties of such a copolymer can be modulated by the composition and segment length to satisfy the needs in a variety of tissue engineering applications such as bone, cartilage, and nerve tube regenerations.

In an effort of achieving suitable biomaterials for peripheral nerve regeneration, we present a material design strategy of combining a crystallite-based physical network and a crosslink-based chemical network. Biodegradable polymer disks and conduits have been fabricated by photo-crosslinking three poly(ε-caprolactone fumarate)s (PCLF530, PCLF1250, and PCLF2000), which were synthesized from the precursor poly(ε-caprolactone) (PCL) diols with nominal molecular weights of 530, 1250, and 2000 g.mol −1 , respectively. Thermal properties such as glass transition temperature (T g ), melting temperature (T m ), and crystallinity of photo-crosslinked PCLFs were examined and correlated with their rheological and mechanical properties. Furthermore, in vitro degradation of uncrosslinked and crosslinked PCLFs in PBS crosslinked PCLFs in 1 N NaOH aqueous solution at 37 °C was studied. In vitro cytocompatibility, attachment, and proliferation of Schwann cell precursor line SPL201 cells on three PCLF networks were investigated. Crosslinked PCLF2000 with the highest crystallinity and mechanical properties was found to best support cell attachment and proliferation. Using a new photocrosslinking method, single-lumen crosslinked PCLF nerve conduits without defects were fabricated in a glass mold. Crosslinked PCLF2000 nerve conduits were selected for evaluation in a 1-cm gap rat sciatic nerve model. Histological evaluation demonstrated that the material was biocompatible with sufficient strength to hold sutures in place after 6 and 17 weeks of implantation. Nerve cable with myelinated axons was found in the crosslinked PCLF2000 nerve conduit.

We present a material design strategy of combining crystallinity and crosslinking to control the mechanical properties of polymeric biomaterials. Three polycaprolactone fumarates (PCLF530, PCLF1250, and PCLF2000) synthesized from the precursor polycaprolactone (PCL) diols with nominal molecular weights of 530, 1250, and 2000 g.mol -1 , respectively, were employed to fabricate polymer networks via photo-crosslinking process. Five different amounts of photo-crosslinking initiator were applied during fabrication in order to understand the role of photoinitiator in modulating the crosslinking characteristics and physical properties of PCLF networks. Thermal properties such as glass transition temperature (T g ), melting temperature (T m ), and degradation temperature (T d ) of photo-crosslinked PCLFs were examined and correlated with their rheological and mechanical properties.