Protein adsorption onto diethylaminoethyl dextran modified anion exchanger:Effect of ionic strength and column behavior

Our previous studies on bovine serum albumin （BSA） adsorption to diethylaminoethyl dextran （DEAE dextran, DexD, grafting-ligand） and DEAE （D, surface-ligand） modified Sepharose FF resins found that all the grafted resins （FF-DexD and FF-D-DexD） exhibited extremely fast uptake rate （effective diffusivity, De, De/Do 〉 1.4）, which was six times greater than the ungrafted resins （De/Do 〈 0.3）. In this work, the influence of ionic strength （IS） on 6 typical DEAE dextran-grafted resins was investigated. Bath adsorption equilibria and kinetics, breakthrough, and linear gradient elution experiments were conducted. Commercial DEAE Sepharose FF was used for comparison. It is found that protein adsorption capacities on DEAE dextran-FF resins and the commercial resin decreased with increasing IS, but DEAE dextran-FF resins exhibited much higher capacity sensitivity to salt concentration. Besides, steeper decrease of adsorption capacities could be obtained at higher graftingligand or surface-ligand density. It is worth noting that the facilitating role of surface-ligand to the ＂chain delivery＂ effect was weakened after adding salt, leading to the less improvement in uptake rate by increasing surface-ligand density at higher IS. Although the uptake rates of the DEAE dextran-FF resins increased first and then decreased with increasing fS, they kept the extremely high level of De values （De/Do 〉 1.1 ） at the their working/binding IS range. Moreover, the DEAE dextran-FF resin displayed much higher adsorption capacities and De values than commercial ungrafted resin in their working condition. Furthermore, the column results of DEAE dextran-FF resins presented higher dynamic binding capacities than and similar elution ISs with DEAE Sepharose FF to achieve similar （or even higher） recoveries suggest the excellent chromatographic column performance of the DEAE dextran-FF resins. Finally, both high recovery and purity of BSA and γ-globulin could be easily achieved using the typical DEAE dextran-FF column, FF-D60-DexD160, to separate their binary mixtures, by step gradient elution. The research has provided new insights into the practical application of the series of DEAE-dextran grafted resins in protein chromatography and proved their superiority.

Production and Purification of Antioxidant Peptides from Flatfish Skin Protein Hydrolysates

Antioxidant peptides of flatfish skin protein hydrolyzed by four enzymes （Papain, Pepsin, Trypsin and Neutrase, respectively）were investigated. The Trypsin hydrotysate obtained by hydrolysis exhibited the highest 1,1- dipheny-l-2-picrylhydrazyl（DPPH） radical scavenging activity （DRSA） compared with other hydrolysates. Re- sponse surface method ology （RSM）, based on Box-Behnken design, was used to study the influence of hydrolysis conditions on the DRSA. The optimal hydrolysis conditions were as follows： pH 7.38, temperature 48.2~C and en- zyme/substrate （E/S）ratio 2 840 U/g. Under these conditions, the maximum DRSA was （22.85 ＋ 0.57）%. The experimental values agreed with the value （23.09%） predicted by the model within a 95% confidence interval. By using gel filtration chromatography and reversed-phase high performance liquid chromatography （RP-HPLC）, anti- oxidant peptide （D2-P）was isolated from flatfish skin protein hydrolysates （FSPH）and could exhibit a （54.28 ± 1.37） % scavenging activity on DPPH radical at the concentration of 5 mg/mL. This is the first report of a scientific basis for the preparation of antioxidant peptides from flatfish skin. The results suggested that the antioxidant pep- tides can be exploited into functional foods or used as a novel source of nutraceuticals.

Fabrication of three-dimensional porous La-doped SrTiO3 microspheres with enhanced visible light catalytic activity for Cr（VI） reduction

In recent years, much effort has been focused on the development of the photocatalysts with high performance under visible light irradiation. In this paper, three-dimensional porous La-doped SrTiO3 （LST） micro- spheres were prepared by a modified sol-gel method, in which the agarose gel/SrCO3 microsphere and La2O3 were employed as the template and the La resource, respectively. The as-prepared LST microspheres exhibit a porous structure with a diameter of about 10 μm and a surface pore size of about 100 nm. The La element was doped into the crystal lattice of SrTiO3 by the substitution of La^3＋ for Sr^2＋. Therefore, the absorption edge of LST samples shifts toward the visible light region, and their photocatalytic activity for the Cr（VI） reduction is enhanced under visible light. Among all LST samples, LST-0.5 （the La^3＋ doping content is 0.5 wt-%） exhibited the highest visible-light photocatalytic activity, which can reduce 84% Cr（VI） within 100 rain. This LST materials may become a promising photocatalyst for the facile treatment of waste- water containing poisonous heavy metal ions.

On-Surface Bottom-Up Construction of COF Nanoshells towards Photocatalytic H_(2)Production

The rational design of an outer shell is of great significance to promote the photocatalytic efficiency of core-shell structured photocatalysts.Herein,a covalent organic framework(COF)nanoshell was designed and deposited on the cadmium sulfide(CdS)core surface.A typical COF material,TPPA,featuring exceptional stability,was synthesized through interfacial polymerization using 1,3,5-triformylphloroglucinol(TP)and p-phenylenediamine(PA)as monomers.The nanoshell endows the CdS@TPPA nanosphere with ordered channels for unimpeded light-harvesting and fast diffusion of reactants/products and well-defined modular building blocks for spatially charge separation.Moreover,the heterojunction formed between CdS and TPPA can further facilitate the effective charge separation at the interface via lower exciton binding energy compared with that of pristine TPPA.By modulating the thickness of TPPA nanoshell,the CdS@TPPA nanosphere photocatalyst with the nanoshell thickness of about 8±1 nm exhibits the highest photocatalytic H2 evolution of 194.1μmol h^(-1)(24.3 mmol g^(-1)h^(-1),8 mg),which is superior to most of the reported COF-based photocatalysts.The framework nanoshell in this work may stimulate the thinking about how to design advanced shell architecture in the core-shell structured photocatalysts to achieve coordinated charge and molecule transport.

Layered Double Hydroxide Modified by PEGylated Hyaluronic Acid as a Hybrid Nanocarrier for Targeted Drug Delivery

In recent years, organic-inorganic hybrid nanocarriers are explored for effective drug delivery and preferable disease treatments. In this study, using 5-fluorouracil(5-FU)as electronegative model drug, a new type of organic-inorganic hybrid drug delivery system(LDH/HA-PEG/5-FU)was conceived and manufactured by the adsorption of PEGylated hyaluronic acid(HA-PEG)on the surface of layered double hydroxide(LDH, prepared via hydrothermal method)and the intercalation of 5-FU in the interlamination of LDH via ion exchange strategy. The drug loading amount of LDH/HA-PEG/5-FU achieved as high as 34.2%. LDH, LDH/5-FU and LDH/HA-PEG/5-FU were characterized by FT-IR, XRD, TGA, laser particle size analyzer and SEM. With the benefit of p Hdegradable feature of LDH and enzyme-degradable feature of HA, LDH/HA-PEG/5-FU showed p H-degradable and enzyme-degradable capacity in in vitro drug release. Moreover, the drug carrier LDH/HA-PEG contained biocompatible PEG and tumor-targeted HA, resulting in lower cytotoxicity and better endocytosis compared with LDH in vitro. It was suggested that the organic-inorganic hybrid drug delivery system, which was endowed with the properties of controlled release, low toxicity and tumor-targeting delivery for ameliorative cancer therapy, was advisable and might be applied further to fulfill other treatments.

Nano-hydroxyapatite formation via co-precipitation with chitosan-g-poly（N-isopropylacrylamide） in coil and globule states for tissue engineering application

With the excellent biocompatibility and osteo- conductivity, nano-hydroxyapatite （nHA） has shown significant prospect in the biomedical applications. Con- trolling the size, crystallinity and surface properties of nHA crystals is a critical challenge in the design of HA based biomaterials. With the graft copolymer of chitosan and poly（N-isopropylacrylamide） in coil and globule states as a template respectively, a novel composite from chitosan-g-poly（N-isopropylacrylamide） and nano-hydro- xyapatite （CS-g-PNIPAM/nHA） was prepared via co- precipitation. Zeta potential analysis, thermogravimetric analysis and X-ray diffraction were used to identify the formation mechanism of the CS-g-PNIPAM/nHA compo- site and its morphology was observed by transmission electron microscopy. The results suggested that the physical aggregation states of the template polymer could induce or control the size, crystallinity and morphology of HA crystals in the CS-g-PNIPAM/nHA composite. The CS-g-PNIPAM/nHA composite was then introduced to chitosan-gelatin （CS-Gel） polyelectronic complex and the cytocompatibility of the resulting CS- Gel/composite hybrid film was evaluated. This hybrid film was proved to be favorable for the proliferation of MC 3T3-E1 cells. Therefore, the CS-g-PNIPAM/nHA compo- site is a potential biomaterial in bone tissue engineering.