A novel oxazolidine based acid-labile monomer N -acryloyl-2,2-dimethyl-1,3-oxazolidine (ADMO) was synthesized and polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization using poly(ethylene glycol) based chain transfer agent (PEG-CTA). The diblock copolymers PEG- b -PADMO were composed of hydrophilic PEG with fixed length and hydrophobic PADMO with different lengths, which formed core-shell micelles in water. Morphologies and sizes of micelles were obtained by transmission electron microscopy (TEM) and dynamic light scattering (DLS), which showed that the shapes of polymeric aggregates developed from small spherical micelles, worm-like micelles to larger size of vesicles, as the length of PADMO increased. The hydrolysis kinetics of the micelles was studied using 1 H NMR, DLS and release of loaded Nile Red dye, whose rate strongly depended on pH and micellar structure . It led to the disruption of polymeric micelles and concomitant release of the guest molecules, due to the transformation of hydrophobic PADMO into hydrophilic poly(2-hydroxyethyl acrylamide) (PHEAM).
Periosteum, a membrane covering the surface of the bone, plays an essential role in maintaining the function of bone tissue—and especially in providing nourishment and vascularization during the bone regeneration process. Currently, most artificial periostea have relatively weak mechanical strength and a rapid degradation rate, and they lack integrated angiogenesis and osteogenesis functions. In this study, a bi-layer, biomimetic, artificial periosteum composed of a methacrylated gelatin–nano-hydroxyapatite (GelMA-nHA) cambium layer and a poly (N-acryloyl 2-lycine) (PACG) -GelMA-Mg 2+ fibrous layer was fabricated via 3D printing. The GelMA-nHA layer is shown to undertake the function of improving osteogenic differentiation of rat bone marrow mesenchymal stem cells with the sustainable release of Ca 2+ from nHA nanoparticles. The hydrogen-bonding-strengthened P(ACG-GelMA-L)-Mg 2+ hydrogel layer serves to protect the inner defect site and prolong degradation time (60 days) to match new bone regeneration. Furthermore, the released magnesium ion exhibits a prominent effect in regulating the polarization phenotype of macrophage cells into the M2 phenotype and thus promotes the angiogenesis of the human umbilical vein endothelial cells in vitro. This bi-layer artificial periosteum was implanted into a critical-sized cranial bone defect in rats, and the 12-week post-operative outcomes demonstrate optimal new bone regeneration. Graphic abstract
危险品化学品经营许可证（带存储）