Use of two-step grafting to fabricate dual-functional films and site-specific functionalized scaffolds.

Polycaprolactone (PCL) is a widely utilized bioresorbable polymer in tissue engineering applications. However, the absence of intrinsic functional groups in the polymer backbone necessitates the incorporation of functional chemistries to enable the further addition of bioactive molecules to PCL-based surfaces and scaffolds. The current study aimed to incorporate two different functional groups, amine and carboxylate, first on two-dimensional (2D) spin-coated PCL films and, thereafter, throughout all surfaces within three-dimensional (3D) porous PCL-based scaffolds, produced using the thermally induced phase separation (TIPS) method, but in a spatially separated manner. Specifically, gamma irradiation induced grafting of acrylic acid (AA) and 2-aminoethyl methacrylate hydrochloride (AEMA) onto PCL was performed in selected solvents and the resulting substrates were characterized using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements to determine the surface free energy. Results demonstrated that stepwise graft copolymerization of AEMA and AA allows the fabrication of dual-functional surfaces, with chemistry depending on the order of grafting of the two monomers. In addition, 3D scaffolds could be decorated exclusively with carboxylate groups in the interior, while the outer surface displayed dual-functionality. This simple surface modification methodology, with the ability to create spatially separated surface functional groups throughout 3D porous scaffolds post their fabrication, has the potential to be applied to many current and future scaffold systems being investigated in the field of tissue engineering.

Electrospinning and mechanical properties of P(TMC-co-LLA) elastomers.

P(TMC-co-LLA) elastomers have shown great potential for various biomaterial and tissue engineering applications. This study systematically investigated properties key to such applications. Three P(TMC-co-LLA) copolymers with 9 to 32 mol% TMC were synthesised and processed into 3D fibrous scaffolds using solution electrospinning. A range of fiber diameters (0.5-5.9 µm) and pore sizes (3.5-19.8 µm) were achieved simply by adjusting the voltage, collector distance and feed rate during electrospinning. The morphological features of the electrospun scaffolds were affected by the copolymer composition such that the average fiber diameters decreased in the order of P(TMC20-co-LLA80) > P(TMC32-co-LLA68) > P(TMC9-co-LLA91), which suggests inherent properties of the copolymers influence the electrospinning process. In addition, the specific parameter combinations applied during electrospinning did not affect the thermal properties of the scaffolds, however, it was confirmed that rapid solidification of the fibers occurred during electrospinning which lowered the inherent crystallinity and caused deviations of the thermodynamic state from equilibrium. Mechanical testing revealed that the Young's modulus and ultimate tensile strength were dependent on the morphology of the fibrous scaffolds, while in contrast, the ductility and toughness were strongly composition dependent with P(TMC20-co-LLA80) scaffolds displaying lower ductility and toughness than P(TMC32-co-LLA68) scaffolds.

Tensile properties and in vitro degradation of P(TMC-co-LLA) elastomers.

P(TMC-co-LLA) elastomers have shown great potential for various biomaterials applications. This study investigated properties key to such applications. Six statistical copolymers with 16 to 49 mol% TMC were synthesized and it was found that the LLA sequence length changed from 14 to 3 for the copolymer series while the M[combining macron]n decreased from 63 to 31 kg mol-1 with increasing TMC content. The thermal properties showed lower Tg values with increasing TMC content which agreed with the Fox equation. Solvent cast films exhibited Young's modulus values between 2.8 and 271 MPa, ultimate tensile strength of 0.6-15.5 MPa and elongation at failure from 356 to 1287%. In vitro degradation in PBS at 37 °C over 34 weeks demonstrated an induction period of 9 weeks during which the water content was minimal for all copolymers. Copolymer films with 21 or greater mol% TMC were found to undergo homogeneous bulk degradation, while films with 16 mol% TMC underwent heterogeneous bulk degradation.