Novel crosslinkable polyester resin–based composites as injectable bioactive scaffolds

Injectable hydrogels for bone and cartilage tissue engineering: a review

Tissue engineering, using a combination of living cells, bioactive molecules, and three-dimensional porous scaffolds, is a promising alternative to traditional treatments such as the use of autografts and allografts for bone and cartilage tissue regeneration. Scaffolds, in this combination, can be applied either through surgery by implantation of cell-seeded pre-fabricated scaffolds, or through injection of a solidifying precursor and cell mixture, or as an injectable cell-seeded pre-fabricated scaffold. In situ forming and pre-fabricated injectable scaffolds can be injected directly into the defect site with complex shape and critical size in a minimally invasive manner. Proper and homogeneous distribution of cells, biological factors, and molecular signals in these injectable scaffolds is another advantage over pre-fabricated scaffolds. Due to the importance of injectable scaffolds in tissue engineering, here different types of injectable scaffolds, their design challenges, and applications in bone and cartilage tissue regeneration are reviewed.

Hema-Functionalized Graphene Oxide: a Versatile Nanofiller for Poly(Propylene Fumarate)-Based Hybrid Materials

Poly(propylene fumarate) (PPF) is a linear unsaturated polyester which has been widely investigated for tissue engineering due to its good biocompatibility and biodegradability. In order to extend the range of possible applications and enhance its mechanical properties, current approaches consist in the incorporation of various fillers or obtaining blends with other polymers. In the current study we designed a reinforcing agent based on carboxylated graphene oxide (GO-COOH) grafted with 2-hydroxyethyl methacrylate (GO@HEMA) for poly(propylene fumarate)/poly(ethylene glycol) dimethacrylate (PPF/PEGDMA), in order to enhance the nanofiller adhesion and compatibility with the polymer matrix, and in the same time to increase the crosslinking density. The covalent modification of GO-COOH was proved by Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Raman spectroscopy. The mechanical properties, water uptake capacity, morphology, biodegradability, mineralization and in vitro cytotoxicity of PPF/PEGDMA hybrid materials containing GO@HEMA were investigated. A 14-fold increase of the compressive modulus and a 2-fold improvement in compressive strength were observed after introduction of the nanofiller. Moreover, the decrease in sol fraction and solvent swelling in case of the hybrid materials containing GO@HEMA suggests an increase of the crosslinking density. SEM images illustrate an exfoliated structure at lower nanofiller content and a tendency for agglomeration at higher concentrations. Finally, the synthesized hybrid materials proved non-cytotoxic to murine pre-osteoblast cells and induced the formation of hydroxyapatite crystals under mineralization conditions.

Lysine-derived, pH-sensitive and biodegradable poly(beta-aminoester urethane) networks and their local drug delivery behaviour

In this study, a series of covalently crosslinked, l-lysine based poly(beta-aminoester urethane) (LPBAEU) networks with good biodegradability and pH sensitivity was reported. The effect of hydrophilic/hydrophobic characteristics and diacrylate/amine molar ratio on the structure, swelling and degradation behaviour of the networks was investigated. The water transport mechanism and dynamic swelling behavior of the LPBAEU networks were strongly affected by medium pH, and swelling amounts up to 252.2% and 148.7% were observed at pH 5.6 and pH 7.4, respectively. It was found that water diffusion within the networks followed a non-Fickian mechanism. The LPBAEU network with the highest diacrylate/amine molar ratio exhibited the highest tensile strength and Young's modulus. In vitro mass losses of networks showed that the degradation rate of LPBAEU networks can be adjusted from 4 to 14 days. LPBAEU networks also supported loading of doxycycline hyclate (DH) and in vitro release studies demonstrated that release of DH from the networks was substantially hindered in the neutral pH environment, with 20.9-56.2% DH release, whereas DH release was accelerated under mild acidic conditions, with a release percentage of 36.6-99.6%. The release data were fitted to different mathematical models and the obtained results confirmed that these networks released DH in a non-Fickian mechanism. The results of this research support the idea that pH-responsive LPBAEU networks may find potential applications in local drug delivery.