Molecular Weight Controllable Degradation of Laminaria japonica Polysaccharides and Its Antioxidant Properties

In this study, molecular weight controllable degradation of algal Laminaria japonica polysaccharides(LPS) was investigated by ultrasound combined with hydrogen peroxide. Three main factors, i.e., ultrasonic power(A), ultrasonic time(B), and H_2O_2 concentration(C) were chosen for optimizing parameters by employing three-factors, three-levels BBD. The influence of degradation on structure change and antioxidant activities was also investigated. A second-order polynomial equation including molecular weight(Y) of Laminaria japonica polysaccharides and each variable parameter, i.e., ultrasonic power(A), ultrasonic time(B), and H_2O_2 concentration(C), was established: Y=20718.67-4273.13A-4000.38B-1438.75C+2333.25AB+1511.00AC+873.00BC+2838.29A^2 + 2490.79B^2+873.04C^2. The equation regression coefficient value(R^2 = 0.969) indicated that this equation was valid. The value of the adjusted determination coefficient(adjusted R^2 = 0.914) also confirmed that the model was highly significant. The results of selected experimental degradation conditions matched with the predicted value. FT-IR spectra revealed that the structures of LPS before and after degradation were not significantly changed. Antioxidant activities of LPS revealed that low Mws possessed stronger inhibitory than the original polysaccharides. The scavenging effects on superoxide radicals was the highest when IC50 of crude LPS was 4.92 mg mL^(-1) and IC50 of Mw 18.576 KDa was 1.02 mg mL^(-1), which was fourfold higher than initial polysaccharide.

Preparation of polysaccharides in different molecular weights from Ulva pertusa Kjellm (Chorophyta)

As molecular weight controls the biological activities of polysaccharides, screening the optimal molecular weight of polysaccharides is important in drug research and application. In this study, hydrogen peroxide was employed as oxidant, and temperature, reaction time, and concentration of polysaccharides and hydrogen peroxide were examined for their effects on the preparation of polysaccharides in different molecular weights from Ulva pertusa. Our experiment suggested that the optimal degradation concentrations for polysac-charides and hydrogen peroxide were 2.5% (w/v) and 8.0% (v/v), respectively. The range of degradation measured by relative viscosity was mainly controlled by temperature and time. Results revealed that 35℃ was the optimal temperature for obtaining low-degradation samples, and 50℃ was the most favorable temperature to accelerate the reaction to yield highly-degraded samples. Four samples in different molecular weights A, B, C and D were finally prepared. The controllability was evaluated by the relative standard deviation (RSD) of relative viscosity, and the peak molecular weights and the polydispersity indexes (Mw/Mn) of molecular weights were measured by high performance gel permeation chromatography (HPGPC).

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.

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.