Graphene quantum dots with Zn2+ and Ni2+ conjugates can cleave supercoiled DNA

Graphene quantum dots (GQDs), inheriting the superb property of graphene oxide, possess smaller lateral size and high biocompatibility, thus having potential in biomedical applications. We previously discovered that GQDs, combining with Cu²⁺ ions, could cleave DNA primarily through an oxidative pathway; yet, oxidative DNA cleavage is not practically preferred in biology. In this work, we explore the DNA cleavage ability of GQDs with Zn²⁺ and Ni²⁺. Zn²⁺ and Ni²⁺ alone are incapable of cleaving supercoiled DNA, but when combining with the GQDs, Zn²⁺ and Ni²⁺ exhibit DNA cleavage activity. However, the activity of these two systems is much lower than that of GQDs/Cu²⁺, and GQDs/Ni²⁺ is less active than GQDs/Zn²⁺. The functional mechanism of GQDs/Ni²⁺ and GQDs/Zn²⁺ is different from that of GQDs/Cu²⁺. The GQDs play a key role in the two systems; the redox inactive Zn²⁺ and Ni²⁺ ions assist to generate the oxidative species that eventually lead to the DNA cleavage. The current results together with our previous result indicate that GQDs together with metal ions can cleave supercoiled DNA, and their cleavage activities depend on the properties of metal ions: for redox active metal ions, metal ions play key roles, for redox inactive metal ions, GQDs are dominant.     

A Novel Method for the Detection of Chlorpyrifos by Combining Quantum Dot-labeled Molecularly Imprinted Polymer with Flow Cytometry

Uniform-sized fluorescent molecularly imprinted polymers were prepared by one-step swelling and suspension polymerization, while chlorpyrifos, methacrylic acid, ethylene glycol dimethacrylate, and oil-soluble CdSe/ZnS quantum dots were used as the carrier, template molecule, functional monomer, cross-linker, and fluorophor, respectively. The morphology, adsorption dynamics, binding ability, and selectivity of quantum dot-labeled molecularly imprinted polymers were evaluated. The dosage of quantum dots for labeling the molecularly imprinted polymers was optimized. The results showed that the optimized dose of quantum dots was 200?µL using a concentration of 8.0?µM. The microsphere size was approximately 10?µm with a honeycombed surface. The quantum dot-labeled molecularly imprinted polymers had an even brightness and a high selectivity. In the presence of different concentrations of chlorpyrifos, a decrease in the fluorescence intensity of the quantum dot-labeled molecularly imprinted polymer was clearly identified by flow cytometry. The whole detection process was accomplished within 2?h including pretreatment. This method was used for the determination of chlorpyrifos in tap water samples.     

9,10-双-(对-(甲氧基二缩三乙二醇基)苯基乙炔基)蒽的合成、自组装及其光谱分析

通过Sonogashira偶联等反应,合成了三嵌段化合物9,10-双-(对-(甲氧基二缩三乙二醇基)苯基乙炔基)蒽,通过¹H NMR和基质辅助激光解吸电离时间飞行质谱(MALDI-TOF-MS)对其结构进行了表征。利用差示扫描量热仪(DSC)、偏光显微镜(POM)及小角X射线散射仪(SAXS)等技术手段对其本体自组装行为进行了研究,结果表明,化合物在固态相自组装成近晶A相(SmA相)。光谱分析表明,该化合物继承了二取代蒽类发光材料具有高荧光量子产率(Φ_f)的特点,是一种性能良好的光致发光材料。     

Molecularly engineered graphene surfaces for sensing applications: A review

Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis.     

Effect of Controlled Deposition of ZnS Shell on the Photostability of CdTe Quantum Dots as Studied by Conventional Fluorescence and FCS Techniques

The effect of one and two monolayers of ZnS shells on the photostability of CdTe quantum dots (QDs) in aqueous and nonaqueous media has been studied by monitoring the fluorescence behavior of the QDs under ensemble and single‐molecule conditions. ZnS capping of the CdTe QDs leads to significant enhancement of the fluorescence brightness of these QDs. Considerable enhancement of the photostability of the shell‐protected QDs, including the suppression of photoactivation, is also observed. Fluorescence correlation spectroscopy measurements reveal an increase in the number of particles undergoing reversible fluorescent on–off transitions in the volume under observation with increasing excitation power; this effect is found to be more pronounced in the case of core‐only QDs than for core–shell QDs.     

富镉离子CdS量子点电化学发光法检测L-半脐氨酸

采用一锅法,通过控制镉硫比合成了表面富镉离子的硫化镉量子点,利用L-半胱氨酸可与量子点表面Cd2+结合,使量子点表面钝化,从而增强其电化学发光信号的性质,实现了对L-半胱氨酸的选择性检测.对合成的量子点进行了表征,优化了检测条件.在优化的条件下,L-半胱氨酸在5.0×10-9~1.0×10-5 mol/L浓度范围内与ECL信号呈良好的线性关系,检出限为1.2×10-9 mol/L(S/N=3).本方法对L-半胱氨酸具有良好的选择性,用于实际样品中L-半胱氨酸的测定,结果令人满意.     

双靶向CdTe量子点的制备及其在细胞标记中的应用

以巯基乙酸和巯基乙酰肼为稳定剂,制备了酸度敏感型CdTe量子点。经与抗体链接,该量子点具备酸度敏感、免疫识别双重靶向功能。经荧光光谱分析、透射电镜图像及细胞免疫成像证明,抗体已成功链接于量子点表面,且该量子点具有酸度敏感及抗体识别的双重靶向功能,可以实现对肿瘤细胞的特异性标记。     

简易法制备高量子产率荧光材料及其应用

选用柠檬酸和三乙烯四胺作为原料,在相对低温下(80 ℃),制备量子产率高达78%的荧光材料。 通过紫外吸收、荧光、傅里叶变换红外光谱仪(FTIR)、核磁共振波谱仪(NMR)等技术手段对该体系进行表征。 结果表明,该荧光材料属于非典型性荧光材料,其强荧光性可能源于体系中大量羰基的聚集。 这种高量子产率材料满足制备隐形墨水的要求,在图案化、防伪和光电子设备等领域具有潜在的应用前景。     

新型荧光分子印迹膜特异性识别和检测目标蛋白质

制备了一种新型荧光分子印迹膜(L-半胱氨酸修饰的量子点嵌入的分子印迹膜(QDs@MIM)),并将其作为荧光人工受体用于目标蛋白质(溶菌酶)的特异性识别和检测。QDs@MIM以溶菌酶为模板分子、丙烯酰胺为功能单体、L-半胱氨酸修饰的量子点为辅助单体、N,N′-亚甲基双丙烯酰胺为交联剂,在预硅烷化的玻璃板上制备而成。在最佳条件下,QDs@MIM对溶菌酶检测的线性范围为0.1~1.0μmol/L,吸附平衡时间为4 min,选择性因子为6.2。该方法操作简单、吸附平衡时间短、选择性高,具备作为生物传感器快速分析样品中目标蛋白质的潜力。