Preparation And Properties Of Bioactive Functional Tissue Regenerative Biomaterials

The regenerative material is crucial for tissue regeneration and repair. Preparation of bioactive functional material is the prerequisite for modulating cell behaviors, e.g. survival, adhesion, proliferation and differentiation, etc. Traditional biodegradable aliphatic polyesters are challenged by their hydrophobicity and absence of reactive sites for further immobilization of bioactive molecules. The bioactivity of natural materials is also inadequate. In this dissertation, the synthesis, structure and properties of bioactive functional materials were studied for nerve tissue engineering. The influence of bioactive peptide and biomimetic moiety on neuron adhesion and neurite outgrowth wa studied. These works had great significance in designing bioactive functional material and nerve tissue regeneration material.In order to prepare biodegradable aliphatic polyesters with reactive groups, a furan-maleimide functionalized trimethylene carbonate (FMTMC) monomer was synthesized and ring-opening copolymerized with L-lactide, the copolymers obtained were activated by retro Diels-Alder reaction to get the maleimide-functionalized poly(ester carbonate)s. The maleimide groups on poly(ester carbonate)s were amenable to Michael addition with thiol-containing molecules such as 3-mercapto-l-propanol,2-aminoethanethiol hydrochloride and mercaptoacetic acid under mild conditions, enabling the biodegradable materials with various functional groups (e.g., hydroxyl, amine and carboxyl). In particular, the maleimide-functionalized poly(ester carbonate) was clicked with a laminin-derived peptide CQAASIKVAV. In vitro culture of PC 12 cells showed that the maleimide-functionalized polymers, especially the CQAASIKVAV-grafted one, could support cell proliferation and neurite outgrowth. The maleimide-functionalized poly(ester carbonate)s provide a versatile platform for diverse functionalization and have comprehensive potentials in biomedical engineering.As a neurotransmitter, acetylcholine has been proved to enhance neuron adhesion and outgrowth. We synthesized a biodegradable poly(ester-carbonate) with pendant acetylcholine analog. The acetylcholine (Ach)-functionalized poly(ester-carbonate) (Ach-P(LA-CITMC)) was prepared by copolymerizing L-lactide (LA) and 5-methyl-5- chloroethoxycarbonyl trimethylene carbonate (ClTMC), and followed by quaternization with trimethylamine. The content of acetylcholine analog could be modulated by changing the molar feeding fraction of C1TMC. The incorporation of acetylcholine analogs improved the hydrophilicity of the films. The content of acetylcholine analogs did not significantly influence the surface morphology of the acetylcholine-functionalized films. The results of PC12 cell culture showed that the acetylcholine analog promoted cell viability and neurite outgrowth in a concentration-dependent manner. The longest length of neurite and the percentage of cells bearing neurites were obtained on the Ach-P(LA-ClTMC)-10 film. All the results indicate that the integration of the acetylcholine analog with an appropriate fraction could be an effective strategy to optimize the existing biodegradable polyesters for nerve regeneration applications.Injectable hydrogel is a kind of attractive materials in regenerative medicine because it can be injected in a liquid form and transform in situ into the gel state. In order to improve neuron adhesion and neurite outgrowth on in situ crosslinked hyaluronic hydrogel, furan and methacrylate groups were grafted on HA (HA-FM) successively by reacting with the carboxyl and hydroxyl groups, respectively, onto which a laminin-derived peptide CQAASIKVAV was covalently immobilized via Michael addition. The furan and peptide modified HA (HA-FP) was then in situ crosslinked by mixing with bismaleimide poly(ethelene glycol) (PEG-(MI)2) at 37? in aqueous solution. The HA derivatives were characterized by 1H NMR and FTIR. The gelation, swelling, mechanical property and morphology of the hydrogels were analyzed. The modulus of the hydrogel could be tuned by changing the substitution degree of furan group, while the peptide concentration could be changed by the ratio of HA-FP with HA-Furan. The influence of modulus and peptide concentration on cell adhesion and neurite outgrowth were studied by seeding PC 12 cells on the HA-PEG hydrogels. The increase of the modulus and peptide concentration could improve neurite outgrowth. The longest neurite outgrowth of PC 12 cells appeared on the HA-PEG hydrogel with the substitution degree of furan and peptide of 29.2% and 23%, respectively. The furan and methacrylate-functionalized HA provides a versatile platform for diverse functionalization and could be used for other cell behavior modulation.