Immobilization of Recombinant Human Catalase on Gold and Silver Nanoparticles

Human catalase cDNA was cloned into a pEX-C-His vector. Purified recombinant catalase was immobilized on nanoparticles. Gold and silver nanoparticles were synthesized in a variety of sizes by chemical reduction; no agglomerates or aggregates were observed in any of the colloids during dynamic light scattering or scanning transmission electron microscopy analysis. After immobilization on gold nanoparticles, recombinant catalase activity was found to be lower than that of the same amount of enzyme in aqueous solution. However, after 10 days of storage at room temperature, the activity of catalase immobilized on gold nanoparticles (AuNPs) of 13 and 20 nm and coverage of 133% was 68 and 83% greater than catalase in aqueous solution, respectively. During 10 days of experiment, percentage activity of catalase immobilized on those gold nanoparticles was higher in comparison to CAT in aqueous solution. Catalase immobilized on silver nanoparticles did not lose activity as significantly as catalase immobilized on AuNPs. Those results confirm the ability to produce recombinant human enzymes in a bacterial expression system and its potential use while immobilized on silver or gold nanoparticles.     

亲水梳状环氧聚合物载体柔性固定化脂肪酶

以氯乙酰化聚苯乙烯微球载体为大分子引发剂,以甲基丙烯酸缩水甘油酯和亲水性丙烯酰胺为共聚接枝单体,以氯化亚铜及2,2'-联吡啶为催化体系,采用原子转移自由基聚合法接枝合成了具有柔性链的亲水梳状环氧聚合物载体PS-acyl-P(AM-co-GMA),并将其用于耐有机溶剂YCJ01脂肪酶的共价柔性固定化.结果表明,固定化酶催...     

聚六亚甲基碳酸酯二醇增韧环氧树脂的固化动力学

The kinetics of the cure reaction for the system consisting of bisphenol-A diglycidyl ether, No.70 anhydride, Polyhexamethylene Carbonate Diol(PHMCD) and DMP-30 has been studied. By use of differential scanning calorimetry(DSC) under isothermal condition, the reaction is found to proceed first via autocatalytic mechanism up to a conversion of 0.3 and then become a first order reaction over a temperature range of 130~160 ℃. The kinetic parameters of the curing reaction have also been determined with both E1 = 63.74 kJ.mol-1, lnA1=13, lnA2 = -3for the autocatalytic mechanism and E =64.68 kJ•mol-1, lnA = 13.8 for the first order mechanism.     

Nylon Based Nanocomposites: Influence of Calcium Carbonate Nanoparticles on the Thermal Stability

In this paper thermal and thermo-oxidative stability of nylon 6 based nanocomposites containing up to 5% by weight of fatty acid coated calcium carbonate (CaCO₃) nanoparticles is studied. Thermal stability of compression-moulded samples was evaluated by thermogravimetric analysis (TG) under air and nitrogen atmosphere. Kinetic analysis of TG data was performed by using the Flynn-Wall-Ozawa method. Results show that the presence of coated nanoparticles adversely affects the thermal and thermo-oxidative stability of nylon 6. Kinetic analysis shows that a complex, multi-step decomposition process occurs. Moreover, the presence of nanoparticles do not affect the rate limiting step of nylon 6 decomposition in air, while under nitrogen atmosphere the decomposition process occurs through a diffusion-driven regime in presence of high amounts of CaCO₃.     

模拟生物矿化过程原位合成活性纳米碳酸钙

生物矿化是一种广泛而复杂的固液之间、有机物和无机物间的物理化学过程．以少量有机质为模板,进行分子操作,高度有序地组合成无机材料．有机基质能作为构造支持的惰性底质或矿物沉淀的局限空间和核化作用的表面,确定矿物质点的形态大小、空间排列、结晶取向和同质多晶类型,并与生物晶体一起确定生物矿物硬体的机械性质．     

The Control of Thermal and Radiation Stability of Polypropylene Containing Calcium Carbonate Nanoparticles

Thermal and γ radiation stability of iPP containing CaCO₃ nanoparticles were investigated by oxygen uptake procedure at 190 °C. The loading of iPP matrix was maximum 25% (w/w). The behavior on thermal oxidation was investigated for two formulations of iPP compounds differing by the surface characteristics of nanoparticles (i.e. uncoated and stearic acid-coated filler). Three irradiation doses (5, 15 and 25 kGy) were applied. The efficient protection of stabilizers that are present in the as-prepared formulations was emphasized by proper values of the kinetic parameters obtained for oxidation. The contribution of CaCO₃ nanoparticles to the oxidative process of iPP is discussed.     

Flash Nanoprecipitation Fabrication of PEI@Amorphous Calcium Carbonate Hybrid Nanoparticles for siRNA Delivery

RNA interference (RNAi) is a promising approach for disease treatments. But the development of safe and effective delivery carriers remains a major challenge. Organic–inorganic hybrid nanoparticles (NPs), with the integration of functions from distinct materials, show great potential in small interfering RNA (siRNA) delivery. Herein, pH responsive amorphous calcium carbonate NPs (ACC NPs) are prepared using flash nanoprecipitation and hybrid NPs are constructed by coating ACC NPs with polyethyleneimine (PEI) for efficient siRNA delivery. PEI/ACC NPs show robust pH responsiveness and stability as well as effective siRNA loading and protection. Furthermore, siRNA-loaded PEI/ACC NPs demonstrate enhanced cellular uptake and efficient endosomal escape, mediating improved siRNA delivery compared to pure PEI. These findings suggest that PEI/ACC NPs may have great potential in siRNA delivery for RNAi-based therapy.     

Calcium Carbonate Dissolution from the Laboratory to the Ocean: Kinetics and Mechanism

The ultimate fate, over the course of millennia, of nearly all of the carbon dioxide formed by humankind is for it to react with calcium carbonate in the world's oceans. Although, this reaction is of global relevance, aspects of the calcite dissolution reaction remain poorly described with apparent contradictions present throughout the expansive literature. In this perspective we aim to evidence how a lack of appreciation of the role of mass-transport may have hampered developments in this area. These insights have important implications for both idealised experiments performed under laboratory conditions and for the measurement and modelling of oceanic calcite sediment dissolution.     

Enzymatic Protein Immobilization on Amino-Functionalized Nanoparticles

The immobilization of proteins on nanoparticles has received much attention in recent years. Among different approaches, enzymatic protein immobilization shows unique advantages because of its site-specific connection. OaAEP1 is a recently engineered peptide ligase which can specifically recognize an N-terminal GL residue (NH₂–Gly–Leu) and a C-terminal NGL amino acid residue (Asn–Gly–Leu–COOH) and ligates them efficiently. Herein, we report OaAEP1-mediated protein immobilization on synthetic magnetic nanoparticles. Our work showed that OaAEP1 could mediate C-terminal site-specific protein immobilization on the amino-functionalized Fe₃O₄ nanoparticles. Our work demonstrates a new method for site-specific protein immobilization on nanoparticles.     

Calcium Carbonate Deposition on Cellulose

Cellulose powder was found to be a substrate favoring the deposition of calcite crystals from stable supersaturated solutions at pH 8.50 and at 25 degrees C. Kinetic analysis of the initial rates showed that they were proportional with the relative supersaturation with respect to calcite. Analysis of the dependence of the induction periods on the initial solution conditions showed that the number of ions forming the critical nucleus was 5. The second-order dependence of the rate of precipitation of calcite on cellulose on the solution supersaturation suggested a surface controlled mechanism. The surface energy of the calcite nuclei growing on cellulose was calculated to be 46 mJ m(-2) from the dependence of the induction time on the solution supersaturation. The overgrowth of calcite on cellulose was done selectively on the macromolecules possibly through active sites formation at ionizable functional groups (-OH). The nucleating capability of cellulose was found to be comparable with that of sulfonated polystyrene and significantly lower in comparison with sulfonated polystyrene divinyl benzene copolymer on which vaterite was formed. This fact together with the selective growth of the most stable calcite suggested that stereochemical factors are very important in determining both the kinetics and the nature of the polymorph formed. Copyright 2000 Academic Press.     

iPP Based Nanocomposites Filled with Calcium Carbonate Nanoparticles: Structure/Properties Relationships

Isotactic polypropylene (iPP) based nanocomposites filled with calcium carbonate nanoparticles (CaCO₃) were prepared by melt mixing and structure-properties relationships of the nanomaterials were studied. Elongated CaCO₃ nanopowders coated with two different coating agents, polypropylene-maleic anhydride graft copolymer (iPP-g-MA) and fatty acids (FA), were tested as nanoreinforced phases. The influence of surface treatment of the nanoparticles on the polymer/nanofillers interfacial adhesion and on the final materials properties was investigated. Morphological analysis showed that the selected coating agents induce different iPP/nanofiller adhesion degrees. Young's modulus increases as a function of the nanoparticles content and the coating agent nature. Finally, all the prepared nanocomposites showed a significant improvement of iPP barrier properties either to oxygen or to carbon dioxide.     

Facile Preparation of Polystyrene Grafted Calcium Carbonate Nanoparticles Via Surface-Initiated Atom Transfer Radical Polymerization

Polystyrene grafted calcium carbonate nanoparticles (PS-CaCO₃) were successfully prepared by the surface-initiated atom transfer radical polymerization (SI-ATRP) of styrene from the chloroactic acid modified calcium carbonate nanoparticles (CA-CaCO₃), with Cu(I)Br/1,10-phenanthroline as catalytic system in toluene. The percentage of grafting (PG%) was found to be 230% after a polymerizing time of 24 hours with the conversion of monomer (C%) of 25%, calculated from the TGA results. The PS-CaCO₃ nanoparticles had been characterized by Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), and transmission electron microscope (TEM).     

Curing Kinetics Modeling of Epoxy Modified by Fully Vulcanized Elastomer Nanoparticles Using Rheometry Method

In this study, the curing kinetics of epoxy nanocomposites containing ultra-fine full-vulcanized acrylonitrile butadiene rubber nanoparticles (UFNBRP) at different concentrations of 0, 0.5, 1 and 1.5 wt.% was investigated. In addition, the effect of curing temperatures was studied based on the rheological method under isothermal conditions. The epoxy resin/UFNBRP nanocomposites were characterized via Fourier transform infrared spectroscopy (FTIR). FTIR analysis exhibited the successful preparation of epoxy resin/UFNBRP, due to the existence of the UFNBRP characteristic peaks in the final product spectrum. The morphological structure of the epoxy resin/UFNBRP nanocomposites was investigated by both field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) studies. The FESEM and TEM studies showed UFNBRP had a spherical structure and was well dispersed in epoxy resin. The chemorheological analysis showed that due to the interactions between UFNBRP and epoxy resin, by increasing UFNBRP concentration at a constant temperature (65, 70 and 75 °C), the curing rate decreases at the gel point. Furthermore, both the curing kinetics modeling and chemorheological analysis demonstrated that the incorporation of 0.5% UFNBRP in epoxy resin matrix reduces the activation energy. The curing kinetic of epoxy resin/UFNBRP nanocomposite was best fitted with the Sestak–Berggren autocatalytic model.     

CaCO3纳米微粒的层状液晶模板法制备及其生长过程中的形貌演变

在Triton X-100/n-C₁₀H₂₁OH/H₂O体系中，低角X射线衍射测试表明层状液晶的溶剂层厚度小于3 nm。利用层状液晶为模板制备了CaCO₃纳米微粒，并用透射电子显微镜(TEM)、X射线衍射(XRD)和选区电子衍射(SAED)进行了表征。TEM结果表明所得CaCO₃纳米粒子的形貌为球形，粒径在2～8 nm，分布较窄。XRD表明CaCO₃纳米微粒的物相为方解石型和球霰石型混合结构。在制备过程中，Ca(OH)₂的加入和CaCO₃纳米微粒的析出并未破坏层状液晶的对称性和长程有序性。此外，在Triton X-100/CH₃CH₂OH体系中，研究了CaCO₃纳米微粒的生长行为，发现小的纳米微粒先通过导向聚集生长成小的梭状物，然后小的梭状物继续生长，最后发生Ostwald陈化形成较为均一的两头尖的带状纳米结构，其宽度在50～200 nm，长度约为2 μm。     

含环氧基团的聚合物载体合成方法的改进及其固定化青霉素酰化酶

 以 Span-60 和 Tween-20 为复合分散剂, 以 N,N′-亚甲基双丙烯酰胺为交联剂, 以甲基丙烯酸缩水甘油酯和烯丙基缩水甘油醚为功能性单体, 用反相悬浮聚合技术成功制备了含环氧基团的聚合物载体, 并用红外光谱和低温氮吸附对聚合物载体进行了表征. 以 Span-60 和 Tween-20 为复合分散剂, 替代原有的 Span-60 和硬脂酸钙复合分散剂, 大幅度减少了后处理过程中所需的时间和溶剂用量, 使固定化青霉素酰化酶的活性从 215 U/g 提高到 320 U/g. 与游离酶相比, 该固定化酶具有较好的操作稳定性, 在 pH = 5~11 和不高于 50 oC 的环境中具有较好的稳定性. 固定化酶的水解反应动力学过程与游离酶相同, 均遵循米氏反应动力学, 而且活性与底物浓度密切相关. 当底物浓度为 6.5% 时, 固定化酶的活性最高, 达到 353 U/g.     

环氧基修饰周期性介孔有机氧化硅对漆酶的固定化作用

以三嵌段共聚物P123为模板剂, 在酸性条件下通过1,2-三乙氧基硅基乙烷(BTESE)和3-含氧缩水甘油基-丙基-三甲氧基硅烷(GPTMS)共水解缩聚合成环氧基修饰的周期性介孔氧化硅(PMOs), 以修饰后的PMOs为载体对漆酶进行固定化, 研究了环氧基修饰对固定化酶稳定性的影响. 通过XRD、TEM、固态NMR和N₂吸附等手段表征材料的修饰效果、孔结构以及漆酶的固定化. 结果表明, 修饰后的材料保持良好的孔结构, 环氧基的修饰有利于提高固定化酶的活力, 基于环氧基修饰PMOs的固定化酶具有较高稳定性.     

Pre-Eutectic Densification of Calcium Carbonate Doped with Lithium Carbonate

Pressureless sintering of CaCO₃ was carried out, with Li₂CO₃ (from 0.5 to 8 wt%) as an additive, under different pressures of CO₂. Densification occurs between 600 and 700°C. Sintering above the eutectic temperature (T>662°C) leads to the decomposition of calcium carbonate and the materials become expanded. At 620° under 1 kPa of CO₂, a relative density of 96% is reached. Li₂CO₃ enhances the densification process and grain growth of calcium carbonate. CO₂ pressure slows down densification and grain growth kinetics. These results are explained by the influence of carbonate and calcium ion vacancies on the sintering mechanisms. This revised version was published online in August 2006 with corrections to the Cover Date.     

Calcium Carbonate Mineralized Nanoparticles as an Intracellular Transporter of Cytochrome c for Cancer Therapy

A new intracellular delivery system based on an apoptotic protein‐loaded calcium carbonate (CaCO₃) mineralized nanoparticle (MNP) is described. Apoptosis‐inducing cytochrome c (Cyt c) loaded CaCO₃ MNPs (Cyt c MNPs) were prepared by block copolymer mediated in situ CaCO₃ mineralization in the presence of Cyt c. The resulting Cyt c MNPs had a vaterite polymorph of CaCO₃ with a mean hydrodynamic diameter of 360.5 nm and exhibited 60 % efficiency for Cyt c loading. The Cyt c MNPs were stable at physiological pH (pH 7.4) and effectively prohibited the release of Cyt c, whereas, at intracellular endosomal pH (pH 5.0), Cyt c release was facilitated. The MNPs enable the endosomal escape of Cyt c for effective localization of Cyt c in the cytosols of MCF‐7 cells. Flow cytometry showed that the Cyt c MNPs effectively induced apoptosis of MCF‐7 cells. These findings indicate that the CaCO₃ MNPs can meet the prerequisites for delivery of cell‐impermeable therapeutic proteins for cancer therapy.     

牛血清白蛋白对碳酸钙结晶的作用

The crystal CaCO₃ with specific shapes was prepared by the biomimetic synthesis , using BSA as the matrix. The products were characterized by scanning electron microscopy (SEM), FTIR spectroscopy and TG. The results show that BSA have the effect on the shapes of CaCO₃ in the crystallization process. The probable mechanism of the effect was discussed。     

聚丙撑碳酸酯增韧环氧树脂的研究

研究了聚丙撑碳酸酯（ＰＰＣ）对环氧树脂（ＥＰ）的改性作用、加入２０～３０Ｐｈｒ的ＰＰＣ，环氧树脂力学性能可以大幅度提高，粘接剪切强度为１２３３ＭＰａ，冲击强度为１６．７８ｋＪ／ｍ２；而纯环氧树脂固化物，其剪切强度为９．３６ＭＰａ，冲击强度为９．９９ｋＪ／ｍ２。ＳＥＭ和ＤＳＣ观测表明ＰＰＣ／ＥＰ体系呈两相结构。