Qingpu Hou

Porous polymeric structures for tissue engineering prepared by a coagulation, compression moulding and salt leaching technique.

A technique for the preparation of porous polymeric structures involving coagulation, compression moulding and particulate leaching has been developed. The technique combines the advantages of thermal processing methods and particulate leaching. A high molecular weight polymer solution in an organic solvent containing dispersed water-soluble salt particles is precipitated into an excess of non-solvent. The polymer-salt composite is then processed by thermal processing methods into devices of varying shapes and sizes, which can subsequently be extracted to give the desired porous structures. The porosities of the scaffolds could be varied between 70% and 95% by adjusting the polymer to salt ratio and the pore size could be controlled independently by varying the leachable particle size. This versatility provides for the optimisation of scaffolds used in medicine and in tissue engineering. Compared with commonly used porosifying methods such as sintering, compression moulding combined with salt leaching, and freeze-drying, this process allows excellent control over pore size and porosity and yields scaffolds with a much more homogeneous pore morphology. We have prepared porous structures from several relevant polymers in the biomedical field: poly(D,L-lactide), poly(epsilon-caprolactone) and 1000PEOT70PBT30, a segmented poly(ether ester) based on polyethylene oxide and polybutylene terephthalate.

Creep-resistant elastomeric networks prepared by photocrosslinking fumaric acid monoethyl ester-functionalized poly(trimethylene carbonate) oligomers

Biodegradable elastomeric networks were prepared from ethyl fumarate-functionalized poly(trimethylene carbonate) oligomers. Photocrosslinkable macromers were synthesized by reacting three-armed, hydroxyl group-terminated poly(trimethylene carbonate) oligomers with fumaric acid monoethyl ester at room temperature using N,N-dicyclohexylcarbodiimide as a coupling agent and 4-dimethylamino pyridine as a catalyst. Poly(trimethylene carbonate) macromers with molecular weights ranging between 4500 and 13,900 were prepared and crosslinked by ultraviolet-initiated radical polymerization. The gel contents of the resulting transparent networks varied between 74% and 80%. All obtained networks had low glass transition temperatures, which varied between -18 and -13 degrees C. They showed rubber-like behavior and excellent mechanical properties, with tensile strengths and elongations at break of up to 17.5 MPa and 750%, respectively. Moreover, static- and dynamic creep experiments showed that these amorphous networks were highly elastic and resistant to creep. In cyclic tensile testing to 50% strain, the permanent deformation after 20 cycles was 0%, while static creep tests at 35% of the yield stress did not indicate creep or permanent deformation after removal of the load. Porous structures were prepared by photopolymerizing the macromers in the presence of salt particles, and subsequent leaching of the salt. Such networks, built up of non-toxic compounds and designed to release benign degradation products, may find application as tissue engineering scaffolds for dynamic cell culture.

Preparation of Porous Poly(ε-caprolactone) Structures

Porous poly(e-caprolactone) structures have been prepared by leaching of compression moulded salt-containing polymer precipitates. Coagulation takes place when a PCL solution containing dispersed water-soluble salt particles is precipitated into an excess of non-solvent. Porous scaffolds are obtained after leaching of the compression moulded polymer-salt precipitate. This process yields scaffolds with a very homogeneous pore morphology and independent control of pore size and porosity.

Methacrylate-Functionalized Oligomers Based On Lactide, E-Caprolactone And Trimethylene Carbonate For Application In Stereo-Lithography

Photo-curable biodegradable macromers were prepared by ring opening polymerization of D,L-lactide (DLLA), (similar to)-caprolactone (CL) and 1,3-trimethylene carbonate (TMC) in the presence of glycerol or sorbitol as initiator and stannous octoate as catalyst, and subsequent methacrylation of the terminal hydroxyl groups. These methacrylated macromers, ranging in molecular weight from approximately 700 to 6000 g/mol, were cross-linked using ultraviolet (UV) light to form biodegradable networks. Homogeneous networks with high gel contents were prepared. One of the resins based on PTMC was used to prepare three-dimensional structures by stereo-lithography using a commercially available apparatus.