Synthesis and characterization of poly(p-dioxanone)-based degradable copolymers with enhanced thermal and hydrolytic stabilities

Herein, we presented a novel biodegradable copolymer via the chain extending reaction of poly(pdioxanone)-co-poly(2-(2-hydroxyethoxy) benzoate)(PPDO-co-PDHB) prepolymer with hexamethylene diisocyanate(HDI) as a chain extender. The structures and molecular weight of PPDO-co-PDHB prepolymer and PPDO-co-PDHB-PU chain-extended copolymer are characterized via hydrogen nuclear magnetic resonance spectroscopy(1 H NMR) and viscosity test. The relationship between the molecular structures and properties of the chain-extended copolymers is established. The PPDO-co-PDHB-PU copolymers possess a better thermal stability comparing with the PPDO homopolymer. The study of mechanical properties shows that the elongation-at-break of PPDO-co-PDHB-PU is much higher than that of PPDO. The investigation of hydrolytic degradation behaviors indicates the degradation rate of PPDO can be controlled by adjusting the PDHB compositions, and proves that chain-extended copolymers exhibit an excellent hydrolytic stability being better than that of PPDO.

Tuning filament composition and microstructure of 3D-printed bioceramic scaffolds facilitate bone defect regeneration and repair

It is still a challenge to optimize the component distribution and microporous structures in scaffolds for tailoring biodegradation(ion releasing)and enhancing bone defect repair within an expected time stage.Herein,the core–shell-typed nonstoichiometric wollastonite(4%and 10%Mg-doping calcium silicate;CSiMg4,CSiMg10)macroporous scaffolds with microporous shells(adding~μ10 μm PS microspheres into shell-layer slurry)were fabricated via 3D printing.The initial mechanical properties and bio-dissolution(ion releasing)in vitro,and osteogenic capacity in vivo of the bioceramic scaffolds were evaluated systematically.It was shown that endowing high-density micropores in the sparingly dissolvable CSiMg10 or dissolvable CSiMg4 shell layer inevitably led to nearly 30%reduction of compressive strength,but such micropores could readily tune the ion release behaviour of the scaffolds(CSiMg4@CSiMg10 vs.CSiMg4@CSiMg10-p;CSiMg10@CSiMg4 vs.CSiMg10@CSiMg4-p).Based on the in rabbit femoral bone defect repair model,the 3D μCT reconstruction and histological observation demonstrated that the CSiMg4@CSiMg10-p scaffolds displayed markedly higher osteogenic capability than the other scaffolds after 12weeks of implantation.It demonstrated that core–shell bioceramic 3D printing technique can be developed to fabricate single-phase or biphasic bioactive ceramic scaffolds with accurately tailored filament biodegradation for promoting bone defect regeneration and repair in some specific pathological conditions.

A pH-switched mesoporous nanoreactor for synergetic therapy

Zinc oxide nanoparticles （ZnO NPs）, as a new type of pH-sensitive drug carrier, have received much attention. ZnO NPs are stable at physiological pH, but can dissolve quickly in the acidic tumor environment （pH 〈 6） to generate cytotoxic zinc ions and reactive oxygen species （ROS）. However, the protein corona usually causes the non-specific degradation of ZnO NPs, which has limited their application considerably. Herein, a new type of pH-sensitive nanoreactor （ZnO-DOX@F-mSiO2-FA）, aimed at reducing the non-specific degradation of ZnO NPs, is presented. In the acidic tumor environment （pH 〈 6）, it can release cytotoxic zinc ions, ROS, and anticancer drugs to kill cancer cells effectively. In addition, the fluorescence emitted from fluorescein isothiocyanate （FITC）-labeled mesoporous silica （F-mSiO2） and doxorubicin （DOX） can be used to monitor the release behavior of the anticancer drug. This report provides a new method to avoid the non-specific degradation of ZnO NPs, resulting in synergetic therapy by taking advantage of ZnO NPs-induced oxidative stress and targeted drug release.