Electrochemical deoxyribonucleic acid biosensor based on carboxyl functionalized graphene oxide and poly-l-lysine modified electrode for the detection of tlh gene sequence related to vibrio parahaemolyticus

A carboxyl functionalized graphene oxide (GO-COOH) and electropolymerized ploy-l-lysine (PLLy) modified glassy carbon electrode (GCE) was fabricated and used for the construction of an electrochemical deoxyribonucleic acid (DNA) biosensor. The NH₂ modified probe ssDNA sequences were immobilized on the surface of GO-COOH/PLLy/GCE by covalent linking with the formation of amide bonds, which was stable and furthur hybridized with the target ssDNA sequence. Differential pulse voltammetry (DPV) was used to monitor the hybridization events with methylene blue as electrochemical indicator, which gave a sensitive reduction peak at −0.287 V (vs. SCE). Under the optimal conditions the reduction peak current was proportional to the concentration of tlh gene sequence in the range from 1.0 × 10⁻¹² to 1.0 × 10⁻⁶ mol L⁻¹ with a detection limit as 1.69 × 10⁻¹³ mol L⁻¹ (3σ). The polymerase chain reaction products of tlh gene from oyster samples were detected with satisfactory results, indicating the potential application of this electrochemical DNA sensor.     

Effect of Exogenous Carboxyl and Hydroxyl Groups on Pyrolysis Reaction of High Molecular Weight Poly(L-Lactide) under the Catalysis of Tin

The effect of exogenous hydroxyl, carboxyl groups and/or Sn~(2+) on pyrolysis reactions of poly(L-lactide)(PLLA) was investigated by thermogravimetric analysis(TGA). The activation energy(E_a) of pyrolysis reactions was estimated by the Kissinger-Akahira-Sunose method. The kinetic models were also explored by the Malek method, and the random degradation behavior was determined by comparing the plots of ln{-ln[1-(1-w)~(0.5)]} versus 1/T for experimental data from TGA with model reactions. The pyrolysis reaction rate of PLLA was affected slightly by exogenous hydroxyl and carboxyl groups at lower levels of Sn with 65-70 mg·kg~(-1) but increased appreciably in the presence of extraneous Sn~(2+), ―COOH/Sn~(2+), or ―OH/Sn~(2+). The E_a values for the pyrolysis reactions of the PLLAs that provided lactide were different under the catalysis of Sn~(2+) in different chemical environments because Sn~(2+) can form the new Sn-carboxylate and Sn-alkoxide with exogenous carboxyl and hydroxyl groups, which were different in steric hindrance for the formation of activated complex between Sn~(2+) and PLLA. Under the catalysis of Sn~(2+), a lactide molecule can be directly eliminated selectively at a random position of PLLA molecular chains, and the molecular chain of PLLA cannot change two PLLA fragments at the elimination site of lactide. However, it was regenerated into a new PLLA molecule with the molecular weight reduced by 144 g·mol~(-1).     

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Soap-free hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate(MMA),butyl acrylate(BA), methacrylic acid(MAA),styrene(St)and ethylene glycol dimethacrylate(EGDMA)as monomers,and the influences of MMA content used in the core preparation on polymerization,particle size and morphology were investigated by transmission electron microscopy,dynamic light scattering and conductometric titration.The results showed that the seeded emulsion polymerization could be carried out smoothly using "starved monomer feeding process" when MAA content in the core preparation was equal to or less than 24 wt%,and the encapsulating efficiency of the hydrophilic P(MMA-BA-MAAEGDMA) core with the hydrophobic PSt shell decreased with the increase in MAA content.When an interlayer of P(MMAMAA -St)with moderate polarity was inserted between the P(MMA-BA-MAA-EGDMA)core and the PSt shell,well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt%MAA content in the core preparation were obtained.     

高Fe3O4含量微米尺寸磁性复合微球的合成及其在化学发光免疫检测中应用初探

 采用种子乳液聚合方法制得了微米尺度的高磁性物质含量的磁性复合微球.聚合体系中,以0.7~0.8 μm的Fe₃O₄磁性聚集体细乳液作为种子,将苯乙烯,二乙烯基苯作为聚合单体加入到磁性聚集体细乳液中,对Fe₃O₄磁性聚集体进行溶胀后进行聚合.研究了聚合过程中,溶胀时间对复合微球形貌和磁性物质含量的影响,获得系列形貌微球.通过透射电镜(TEM)、热重分析(TGA)、红外分析(FTIR)、振动样品磁强计(VSM)等表征手段对所制备的磁性聚合物微球进行分析表征.结果显示,所得到的磁性聚合物微球粒度为0.7~1 μm,尺寸分布较均一,具有超顺磁性,磁性物质含量为29 wt%~57 wt%.然后又通过丙烯酸和苯乙烯共聚对微球表面羧基功能化后,得到了表面羧基密度为0.92 mmol/g的微球,再将所制备的微球与生物分子偶联后（以hCG作为模式待检分子）,在化学发光免疫检测上进行了初步的应用,取得到了较好的应用结果.     

Integration of carboxyl modified magnetic particles and aqueous two-phase extraction for selective separation of proteins

Both of the magnetic particle adsorption and aqueous two-phase extraction (ATPE) were simple, fast and low-cost method for protein separation. Selective proteins adsorption by carboxyl modified magnetic particles was investigated according to protein isoelectric point, solution pH and ionic strength. Aqueous two-phase system of PEG/sulphate exhibited selective separation and extraction for proteins before and after magnetic adsorption. The two combination ways, magnetic adsorption followed by ATPE and ATPE followed by magnetic adsorption, for the separation of proteins mixture of lysozyme, bovine serum albumin, trypsin, cytochrome C and myloglobin were discussed and compared. The way of magnetic adsorption followed by ATPE was also applied to human serum separation.     

One-pot synthesis,characterization, and drug loading of polysaccharide-based nanoparticles with carboxy functional groups

Herein, various polysaccharide-based nanoparticles were synthesized from dextran, hydroxypropyl cellulose, and hydroxyethyl cellulose, respectively, by a self-assembly assisted approach. This approach enables us to prepare stable polysaccharide-based nanoparticles with carboxy functional groups directly from monomers without using any surfactant and organic solvent. The existence of abundant carboxyls in these polysaccharide-based nanoparticles provides them obvious pH sensitivity as verified by ¹H nuclear magnetic resonance as well as the potential in loading cationic drug.     

Influence of hydrophilic–lipophilic balance of nonionic emulsifiers on emulsion copolymerization of styrene and methacrylic acid

Emulsion copolymerizations of styrene and methacrylic acid (MAA) with various nonionic emulsifiers having a hydrophilic–lipophilic balance (HLB) range of 13.7–17.2 were performed to clarify the influence of emulsification state on polymerization. The emulsification state with a lower-HLB value emulsifier was worse than that with a higher one. In the lowest HLB value, MAA was predominantly polymerized over styrene in the early stage of the copolymerization, resulting in predominant (heterogeneous) distribution of MAA units in the inside of the final polymer particles. In the higher-HLB emulsifiers, styrene and MAA were simultaneously copolymerized, resulting in a homogeneous MAA distribution. The percentage of incorporation of the nonionic emulsifier inside the particles was the highest (49% based on the total amount of the emulsifier) in the lowest HLB, whereas it was 1% in the highest HLB. Part CCLXXXIV of the series “Studies on suspension and emulsion”.     

磁性多孔γ-Fe_2O_3/P(St-DVB-MAA)聚合物微球的制备及其表征

以油酸包裹的γ-Fe2O3为磁性来源,选用苯乙烯(St)、二乙烯苯(DVB)和甲基丙烯酸(MAA)为共聚单体,通过改进的悬浮聚合法,制备了表面含有羧基的多孔磁性高分子微球.利用红外光谱(FTIR)、扫描电子显微镜(SEM)、光学显微镜以及热重分析仪(TG)等对聚合物进行了性能表征.FTIR和光学显微镜结果分析表明,苯乙烯、二乙烯苯和甲基丙烯酸在磁性粒子的表面发生了聚合反应,生成了聚合物包埋磁粉的磁性聚合物复合微球,且微球表面含有羧基;SEM和光学显微镜分析测试结果显示合成的磁性γ-Fe2O3/P(St-DVB-MAA)复合粒子呈球形,微球具有多孔结构,且微球之间不发生团聚,微球粒子粒径分布均匀,大多数粒子粒径分布在0.4~0.9mm之间;TG测试的结果表明,磁性γ-Fe2O3被包覆在聚合物微球之中,且磁性粒子在微球中的包覆率达到12.12%.     

羧基化氧化石墨烯的血液相容性

氧化石墨烯的官能团修饰可促进氧化石墨烯与生物体液、聚合物基体等不同环境的融合. 通过超声法制备了氧化石墨烯, 并利用化学改性的方法, 将氧化石墨烯表面的羟基和环氧基转变为羧基. 红外图谱上羧基化氧化石墨烯(GeneO-COOH)的羧基振动明显, 峰强增大. GeneO-COOH的主要失重表现为羧基官能团缩合以一个水分子的形态释放失去结构水[OH2]. 复钙动力学曲线随着GeneO-COOH的浓度增加, 曲线上升趋势由陡峭趋于平缓, 当浓度为1.25 μg/mL时复钙时间延长了11 min, 平台期OD值降低了8.14 %; 在0.5~100 μg/mL浓度范围内溶血率均<5 %. GeneO-COOH比GeneO在同等低浓度下的抗凝血性能有一定程度的改善, 主要是因为带负电的羧基可直接络合凝血因子. 因此, 羧基修饰氧化石墨烯是提高血液相容性的有效手段, 羧基化氧化石墨烯可作为潜在的生物医用材料的填料.     

纳米碳管表面羧基化及其电还原性能

应用红外吸收光谱、扫描电子显微镜分别对纳米碳管和硝化后的纳米碳管进行表征,将其制备成粉末微电极,并在碱性溶液中测试它对对硝基苯酚的电还原性能.实验表明:经硝化处理后,碳管表面修饰了羰基,其电还原性能明显提高.依据实验结果探讨了硝化后纳米碳管于对硝基苯酚电还原过程中的反应机理.