用于检测重金属离子的磁性荧光复合微球

采用静电逐层自组装的方法,首先将PSS和PAH聚电解质交替沉积在CaCO₃中空微球表面,然后将Fe₃O₄磁性纳米粒子与CdSe量子点负载在中空微球表面不同的聚电解质层中,制备出具有磁性和荧光双重功能的复合微球,并将其作为荧光离子探针,研究了其对Cu²⁺和Pb²⁺离子检测的灵敏度、选择性及可行性。结果表明,复合微球显示出良好的磁性和荧光性能,对Cu²⁺和Pb²⁺离子的检测具有较高的灵敏度和选择性。尤为重要的是,可通过磁分离的方法将微球快速地从待测液中回收,从而能够避免量子点对环境造成的二次污染。     

碲化镉量子点自组装膜的构建及其对溶菌酶的界面传感

利用自组装膜(SAMs)技术在石英片表面构建了碲化镉量子点SAMs.考察了组装液浓度、组装时间和聚电解质组装层数等组装条件对膜发光性能的影响,并用紫外可见吸收光谱仪、荧光光谱仪、共聚焦荧光显微镜和原子力显微镜对其进行了表征.基于溶菌酶对该SAMs的荧光具有猝灭效应,建立了一种快速灵敏测定痕量溶菌酶的界面荧光分析法,线性...     

Multifunctional nanoparticles/silica microsphere assemblies using polyglycidyl methacrylate shells as supports

A general method to prepare functional (or multifunctional) nanoparticles/silica microsphere assemblies is reported in this article. A thin shell of polyglycidyl methacrylate is grafted on the surface of silica through surface-initiated atom transfer radical polymerization technique. And then, various types of nanoparticles, including water-soluble CdTe quantum dots, Au nanoparticles and oil-soluble Fe₃O₄ nanoparticles are assembled on silica microspheres, respectively, or simultaneously. The properties of the assembled nanoparticles are well retained in the nanocomposite assemblies, and the controllable integration of magnetic and fluorescent properties can be achieved through varying the proportion of different nanoparticles assembled on nanoparticle/silica microsphere.     

Spontaneous formation of nanoparticle vesicles from homopolymer polyelectrolytes

Nanoparticle vesicles were spontaneously assembled from homopolymer polyamine polyelectrolytes and water-soluble, citrate-stabilized quantum dots. The further addition of silica nanoparticles to a solution of quantum dot vesicles generated stable micrometer-sized hollow spheres whose walls were formed of a thick, inner layer of close-packed quantum dots followed by an outer layer of silica. The method employed here to assemble both the nanoparticle vesicles and the hollow spheres is in direct contrast to previous syntheses that use either tailored block copolymers or oil-in-water emulsion templating. We propose that the formation of charge-stabilized hydrogen bonds between the positively charged amines of the homopolymer polyelectrolytes and the negatively charged citrate molecules stabilizing the quantum dots is responsible for the macroscopic phase separation in this completely aqueous system. The ease and processibility of the present approach gives promise for the production of a diverse array of materials ranging in applications from drug delivery to catalysis to micrometer-scale optical devices.     

Silanized quantum dots as labels in lateral flow test strips for C-reactive protein

The paper describes the first use of silanized semiconductor core-shell quantum dots as fluorescent labels for macromolecule, C-reactive protein determination in blood plasma. The controlled synthesis of CdSe cores, with successive shells of CdS, CdZnS, ZnS and coating with transparent, stable, and inert silica shell, provides quantum dots with a narrow emission band, high quantum yield, and prolonged signal stability. Finally, the quantum dots were conjugated with specific antibodies via carboxylic groups on the silica surface. The method was further used for the immunochromatographic assay of C-reactive protein, a diagnostically important inflammatory biomarker. Assays with both the fluorescent QDs and a widely used colloidal gold label were developed in parallel and compared. The silanized quantum dots provide a more sensitive assay with a detection limit of 1?ng/mL for C-reactive protein in standard solutions, whereas the common assay has a detection limit of 10?ng/mL. The possibility of quantitative evaluation of analyte content by a portable device was demonstrated; the accuracy of the measurements was in the range of 5%–10%. The tests were used to determine C-reactive proteins in human plasma samples. The selected optimized protocol for these samples is based on a 4-fold dilution. The final working range of the assay, 4–1,200?ng/mL, covers practically all important interval of C-reactive protein values for the characterization of acute, chronic, and local inflammatory processes. Due to their high physical stability and inertness as well as intense, stable, and reproducible fluorescence, silanized quantum dots may be applied for high-sensitive assays for different analytes.     

用于检测重金属离子的磁性荧光复合微球

采用静电逐层自组装的方法,首先将PSS和PAH聚电解质交替沉积在CaCO3中空微球表面,然后将Fe3O4磁性纳米粒子与CdSe量子点负载在中空微球表面不同的聚电解质层中,制备出具有磁性和荧光双重功能的复合微球,并将其作为荧光离子探针,研究了其对Cu2+和Pb2+离子检测的灵敏度、选择性及可行性。结果表明,复合微球显示出良好的磁性和荧光性能,对Cu2+和Pb2+离子的检测具有较高的灵敏度和选择性。尤为重要的是,可通过磁分离的方法将微球快速地从待测液中回收,从而能够避免量子点对环境造成的二次污染。     

Fabrication of Multiresponsive Bioactive Nanocapsules through Orthogonal Self‐Assembly

Multifunctional self‐assembled systems present platforms for fundamental research and practical applications as they provide tunability of structure, functionality, and stimuli responsiveness. Pragmatic structures for biological applications have multiple design requirements, including control of size, stability, and environmental response. Here we present the fabrication of multifunctional nanoparticle‐stabilized capsules (NPSCs) by using a set of orthogonal supramolecular interactions. In these capsules, fluorescent proteins are attached to quantum dots through polyhistidine coordination. These anionic assemblies interact laterally with cationic gold nanoparticles that are anchored to the fatty acid core through guanidinium–carboxylate interactions. The lipophilic core then provides a reservoir for hydrophobic endosome‐disrupting agents, thereby generating a system featuring stimuli‐responsive release of a payload into the cytosol with fluorescence monitoring.     

可控异质不对称微粒的制备与组装

以聚合物薄膜作为掩模层来掩蔽有序的单层二氧化硅微粒阵列, 通过等离子体刻蚀控制二氧化硅微粒暴露面积, 并在其上进行可控的化学修饰或可控气相沉积, 利用异质区域选择性组装碲化镉荧光量子点, 得到了具有稳定荧光功能的异质不对称微粒. 利用此方法, 还可以通过引入官能团或粒子进一步得到更高级的多功能不对称微粒.     

A Reversible Dual‐Response Fluorescence Switch for the Detection of Multiple Analytes

This paper reports a reversible dual fluorescence switch for the detection of a proton target and 2,4,6‐trinitrotoluene (TNT) with opposite‐response results, based on fluorophore derivatization of silica nanoparticles. Fluorescent silica nanoparticles were synthesized through modification of the surface with a nitrobenzoxadiazole (NBD) fluorophore and an organic amine to form a hybrid monolayer of fluorophores and amino ligands; the resultant nanoparticles showed different fluorescence responses to the proton target and TNT. Protonation of the amino ligands leads to fluorescence enhancement due to inhibition of photoinduced electron transfer (PET) between the amine and fluorophore. By contrast, addition of TNT results in fluorescence quenching because a fluorescence resonance energy transfer (FRET) happens between the NBD fluorophore and the formed TNT–amine complex. The fluorescence signal is reversible through washing with the proper solvents and the nanoparticles can be reused after centrifugal separation. Furthermore, these nanoparticles were assembled into chips on an etched silicon wafer for the detection of TNT and the proton target. The assembled chip can be used as a convenient indicator of herbicide (2,4‐dichlorophenoxyacetic acid) and TNT residues with the use of only 10 μL of sample. The simple NBD‐grafted silica nanoparticles reported here show a reversible signal and good assembly flexibility; thus, they can be applied in multianalyte detection.     

Size‐Tunable Polymeric Nanoreactors for One‐Pot Synthesis and Encapsulation of Quantum Dots

Hydrophilic polymeric nanoparticles are synthesized through a Bergman cyclization‐ mediated intramolecular chain collapse of structurally well‐defined linear polymers, and then used as size‐tunable nanoreactors to fabricate and encapsulate quantum dots in a one‐pot reaction. Crystalline quantum dots are formed in all of these nanoreactors and visualized by transmission electron microscopy. Smaller nanoreactors produce one quantum dot each while larger nanoreactors form a number, resulting in fluorescence quenching. By controlling the molecular weight of the linear polymer precursor, a variable number of nanocrystals are fabricated and assembled in a single nanoreactor.     

硅壳包被的核壳型量子点荧光纳米颗粒的制备及其细菌计数的应用

以氧化镉和硬脂酸锌为前驱体,合成了CdSe/ZnS核壳型量子点(QDs).采用反相微乳液技术,在温和条件下实现了硅壳包被的CdSe/ZnS荧光纳米颗粒的成功制备.在戊二醛的交联作用下,以金黄色葡萄球菌(S.aureus)为目标细菌、荧光纳米颗粒为荧光探针,建立了一种高灵敏的、简单快速的细菌计数的方法,并借助荧光显微镜成功地进行成像探测研究.通过考察荧光纳米颗粒与细菌的孵育时间、包入硅壳的核壳量子点质量等多种因素的影响.在最优化条件下,本方法的线性范围为5×102～5×107 CFU/mL;检出限为500 CFU/mL;线性回归方程为Y=494.96749X- 1194.25738(R=0.9960).本方法操作简单,检测时间短,有效克服了传统平板计数方法和基于有机染料的荧光检测方法存在的缺陷,提高了灵敏度.将此法用于6种实际样品的细菌数量测定,检测结果与平板计数方法基本一致,相对标准偏差在3.1％～8.2％之间,结果令人满意.     

Energy transfer mediated fluorescence from blended conjugated polymer nanoparticles

Nanoparticles consisting of a derivative of the blue-emitting conjugated polymer polyfluorene doped with green-, yellow-, and red-emitting conjugated polymers were prepared by a reprecipitation method. The nanoparticles can be described as a system of densely packed chromophores that exhibit efficient energy transfer from the host to the dopant polymers. Fluorescence quenching analysis of the host polymer as a function of the dopant concentration indicates that one energy acceptor molecule can effectively quench 90% of the fluorescence of a nanoparticle consisting of 100-200 host conjugated polymer molecules. A nanoparticle energy transfer model was developed that successfully describes the quenching behavior of a small number of highly efficient energy acceptors per nanoparticle. The fluorescence brightness of the blended polymer nanoparticles was determined to be much higher than that of inorganic quantum dots and dye-loaded silica particles of similar dimensions. The combination of high fluorescence brightness and tunable fluorescence of these blended nanoparticles is promising for ultrasensitive fluorescence-based assays.     

水溶性CdSe/CdS量子点的合成及其与牛血清蛋白的共轭作用

用巯基乙酸(TGA)作为稳定剂，合成了水溶性的CdSe和核壳结构的CdSe/CdS半导体量子点。吸收光谱和荧光光谱研究表明，核壳结构的CdSe/CdS半导体量子点比单一的CdSe量子点具有更优异的发光特性。用TEM、电子衍射(ED)和XPS分别表征了CdSe和CdSe/CdS纳米微粒的结构、形貌及分散性。红外光谱和核磁共振谱证实了巯基乙酸分子中的硫原子和氧原子与纳米微粒表面的金属离子发生了配位作用。在pH值为7.4的条件下，将合成的CdSe和CdSe/CdS量子点直接与牛血清白蛋白(BSA)相互作用。实验发现，两种量子点均对BSA的荧光产生较强的静态猝灭作用；而BSA对两种量子点的荧光则具有显著的荧光增敏作用，存在BSA时CdSe/CdS量子点的荧光增强是不存在BSA时体系荧光强度的3倍。     

PEGylated liposome coated QDs/mesoporous silica core-shell nanoparticles for molecular imaging

This paper describes the synthesis and application of PEGylated liposome-coated quantum dots (QDs)/mesoporous silica core-shell nanoparticles (NPs) for molecular imaging. This system increases biocompatibility and stability of QDs, thus improving the imaging effects in labeling of cancer cells.     

Preparation of strongly fluorescent silica nanoparticles of polyelectrolyte-protected cadmium telluride quantum dots and their application to cell toxicity and imaging

Based on the polyelectrolyte-protected CdTe quantum dots (QDs), which were prepared by self-assembling of QDs and poly-diallyldimethylammonium chloride (PDADMAC) in the help of electrostatic attraction, the strong fluorescence silica nanoparticles (QDs-PDADMAC@SiO₂) have been prepared via a water-in-oil reverse microemulsion method. Transmission electron microscopy and Zeta potential analysis were used to characterize the as-prepared nanoparticles. All of the particles were almost spherical and there is a uniform distribution of the particle size with the average diameter about 25 nm. There is a large Zeta potential of −35.07 mV which is necessary for good monodispersity of nanoparticles solution. As compared with the QDs coated by SiO₂ (QDs@SiO₂), the QDs-PDADMAC@SiO₂ nanoparticles have much stronger fluorescence, and their fluorescence stability could be obviously improved. Moreover, QDs-PDADMAC@SiO₂ exhibits good biological compatibility which promotes their application in cellular imaging.     

Chondroitin Sulfate Fluorescence Biosensor Based on Graphere Quantum Dots Aggregating on CMC/CS Polyelectrolyte Microspheres

Here, we report an efficient fluorescence biosensor for chondroitin sulfate(CHS) based on polyelectrolyte microspheres of carboxymethyl cellulose(CMC) and chitosan(CS) composites inducing the aggregation of graphene quantum dots(GQDs), calling CMC/CS-GQDs. The polyelectrolyte microspheres(CMC/CS microspheres) were fabricated by using anioniccationic electrostatic attraction between CMC and CS by high voltage electrostatic spray technology. The aggregating process of GQDs was based on the anionic-cationic electrostatic attraction as well. After combing with the polyelectrolyte microspheres, the fluorescence of GQDs disappeared. CHS, which widely consists in the cell surface of human beings and animals, carries a large number of negative charges on the surface. The addition of CHS enabled CHS and GQDs to compete with each other to composite with the CMC/CS microshpheres. As a result of the higher surface charge density of CHS, CMC/CS-CHS formed accompanied by the release of GQDs, and the fluorescence of the system recovered. The CHS content was detected by analyzing the system's fluorescence recovery, which suggested that the obtained fluorescence biosensor can accurately detect the concentration of CHS. The test results showed that the linear range of the fluorescence recovery for this biosensor with respect to CHS was 0~12.00 mg/mL, and the detection limit was 10-8 M. Besides, to test the stability of the biosensor, the CMC/CS-GQDs micropsheres persisted for one month, with a low fluorescence quenching of 9.48%. These results suggested that CMC/CS-GQDs can be utilized as efficient fluorescence biosensor for the detection of CHS. Moreover, the detection method was simple and efficient, and could be widely popularized.     

Fluorescence energy transfer-based multiplexed hybridization assay using gold nanoparticles and quantum dot conjugates on photonic crystal beads

A multiplexed assay strategy was developed for the detection of nucleic acid hybridization. It is based on fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and multi-sized quantum dots (QDs) deposited on the surface of silica photonic crystal beads (SPCBs). The SPCBs were first coated with a three-layer primer film formed by the alternating adsorption of poly(allylamine hydrochloride) and poly(sodium 4-styrensulfonate). Probe DNA sequences were then covalently attached to the carboxy groups at the surface of the QD-coated SPCBs. On addition of DNA-AuNPs and hybridization, the fluorescence of the donor QDs is quenched because of the close proximity of the AuNPs. However, the addition of target DNA causes a recovery of the fluorescence of the QD-coated SPCBs, thus enabling the quantitative assay of hybridized DNA. Compared to fluorescent dyes acting as acceptors, the use of AuNPs results in much higher quenching efficiency. The multiplexed assay displays a wide linear range, high sensitivity, and very little cross-reactivity. This work, where such SPCBs are used for the first time in a FRET assay, is deemed to present a new and viable approach towards high-throughput multiplexed gene assays.

Biomolecule-quantum dot systems for bioconjugation applications

In the present work, it is reported for the first time the bioconjugation of CdS quantum dots (QDs) directly with bovine serum albumin (BSA) using a one-step procedure via aqueous route at room temperature by methods of colloidal chemistry. Essentially, the bioconjugates were developed based on BSA as capping ligand for the nucleation and stabilization of CdS nanoparticles using cadmium perchlorate and thioacetamide as precursors. UV-visible spectroscopy was used to characterize the kinetics and the relative stability of CdS nanoparticles. The CdS nanocrystals were produced with the calculated average particle size below 4.0 nm, indicating they were in the so-called "quantum-size confinement range". The results have clearly indicated that BSA was effective on nucleating and stabilizing the colloidal CdS quantum dots.     

Determination of the size of quantum dots by fluorescence spectroscopy

There has been a lack of quick, simple and reliable methods for determination of nanoparticle size. An investigation of the size of hydrophobic (CdSe) and hydrophilic (CdSe/ZnS) quantum dots was performed by using the maximum position of the corresponding fluorescence spectrum. It has been found that fluorescence spectroscopy is a simple and reliable methodology to estimate the size of both quantum dot types. For a given solution, the homogeneity of the size of quantum dots is correlated to the relationship between the fluorescence maximum position (FMP) and the quantum dot size. This methodology can be extended to the other fluorescent nanoparticles. The employment of evolving factor analysis and multivariate curve resolution-alternating least squares for decomposition of the series of quantum dots fluorescence spectra recorded by a specific measuring procedure reveals the number of quantum dot fractions having different diameters. The size of the quantum dots in a particular group is defined by the FMP of the corresponding component in the decomposed spectrum. These results show that a combination of the fluorescence and appropriate statistical method for decomposition of the emission spectra of nanoparticles may be a quick and trusted method for the screening of the inhomogeneity of their solution.     

Sizes of water-soluble luminescent quantum dots measured by fluorescence correlation spectroscopy

In this paper, fluorescence correlation spectroscopy (FCS) was applied to measure the size of water-soluble quantum dots (QDs). The measurements were performed on a home-built FCS system based on the Stokes-Einstein equation. The obtained results showed that for bare CdTe QDs the sizes from FCS were larger than the ones from transmission electron microscopy (TEM). The brightness of QDs was also evaluated using FCS technique. It was found that the stability of the surface chemistry of QDs would be significantly improved by capping it with hard-core shell. Our data demonstrated that FCS is a simple, fast, and effective method for characterizing the fluorescent quantum dots, and is especially suitable for determining the fluorescent nanoparticles less than 10 nm in water solution.