Enhanced biomineralization of shape memory composite scaffolds from citrate functionalized amorphous calcium phosphate for bone repair

Traditional shape memory polymers (SMPs) could avoid large volume trauma during implantation; however, for bone repair, scaffolds with high porosity and biomineralization are essential to promote bone regeneration. A novel porous composite scaffold with high biomineralization activity was developed by sequential gas foaming and a freeze-drying method. The results showed that the cross-linked block structure of the polymer matrix presented excellent shape memory properties, and osteogenesis was promoted by citrate functionalized amorphous calcium phosphate (CCACP). CCACP improved the mechanical strength of the scaffold, and the synergistic effect of CCACP and PEG promotes hydrophilicity and further promoted cell adhesion. Bending experiments indicated that the shape-memory effect of the scaffolds could be varied by varying the CCACP content. In addition, hydroxyapatite deposition was sped up as CCACP accelerated the mineralization of the scaffolds. Moreover, the result of the CCK-8 assessment suggested that composite scaffolds exhibited high biocompatibility, and the cells extended out abundant filopodia to adhere onto the scaffolds. In rat bone defect models, the obtained scaffolds promoted new bone formation compared to the control group. The developed composite scaffolds show potential for minimally invasive bone repair application.

New Star-Shaped Polyether-Pentols (PEPOs) for Fabrication of Crosslinked Polyurethanes-Synthesis and Characterization

Polyether-pentols (PEPOs) were synthesized from glycidyl ethers and butylene oxide with the application of tripotassium salts of 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol (HMCH) activated 18C6 for ring-opening polymerization (ROP). The construction of the applied initiator system reflects the ability of crown ether to influence the degree of ion-pair separation with an increased activating effect. As a result formation of bi- or trimodal polymers was observed with molar masses in the range of (Mn = 1200-6000). The observed multi-fraction composition is prescribed to the formation of ionic aggregates with different reactivities during polymerization. The mechanism of the studied processes is discussed. The obtained PEPOs served for a crosslinked PUR synthesis, for which the hydrogen bond index for coupling of hard segments was calculated. Additionally, the range of phase separation was calculated that was higher for PUR-containing aromatic rings as the substituent.

Biomimetic Polyurethane 3D Scaffolds Based on Polytetrahydrofuran Glycol and Polyethylene Glycol for Soft Tissue Engineering

In this study, a novel polyurethane porous 3D scaffold based on polyethylene glycol (PEG) and polytetrahydrofuran glycol (PTMG) was developed by in situ polymerization and freeze drying. Aliphatic hexamethylene diisocyanate (HDI) as a nontoxic and safe agent was adopted to produce the rigid segment in polyurethane polymerization. The chemical structure, macrostructure, and morphology—as well as mechanical strength of the scaffolds—were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and tensile tests. The results show that the HDI can react mildly with hydroxyl (–OH) groups of PEG and PTMG, while gas foaming action caused by the release of CO₂ occurred simultaneously in the reactive process, resulting in a uniform porous structure of PU scaffold. Moreover, the scaffolds were soaked in water and freeze dried to obtain higher porosity and more interconnective microstructures. The scaffolds have a porosity of over 70% and pore size from 100 to 800 μm. The mechanical properties increased with increasing PEG content, while the hydrophilicity increased as well. After immersion in simulated body fluid (SBF), the scaffolds presented a stable surface structure. The gas foaming/freezing drying process is an excellent method to prepare skin tissue engineering scaffold from PTMG/PEG materials with high porosity and good inter connectivity.