Fabrication of quantum dots-encoded microbeads with a simple capillary fluidic device and their application for biomolecule detection

Monodispersed quantum dots (QDs)-encoded polymer microbeads were generated using a simple capillary fluidic device (CFD). The polymer and QDs solution was emulsified into monodispersed microdroplets by the CFD and obtained droplets were solidified via solvent evaporation. Polymer microbeads can be fabricated in a range of different sizes through changing the flow rates of the two immiscible phases, and have a highly narrow size distribution and uniform shape. QDs-encoding capacity of the microbeads was investigated through adjusting the concentrations and ratios of QDs in the polymer solution. Mono-color encoded microbeads with five intensities and a dual-color QDs-encoded 5×5 microbeads array were obtained, and the spectral profiles of the microbeads were examined by a fluorescent microscope coupled with a spectral imaging system. QDs-tagged microbeads prepared with this method were more stable than the porous beads swollen with QDs in the buffer with various pH and crosslinking chemicals. Finally, the application of such microbeads for biomolecule detection was demonstrated by conjugation of rabbit IgG molecules on the surface of the microbeads via carboxyl groups, which were then detected by fluorophores-labeled goat-anti-rabbit IgG antibodies.     

A polymeric chiral surface functionality immobilized on uniformly sized macroporous polymer beads

Uniformly sized functionalized macroporous polymer beads were prepared by either a classical copolymerization method or recently reported in situ surface modification method utilizing chiral methacrylamide as a functional modifier. To evaluate conformational and/or specific differences in their surface chiral functionality, we applied chromatographic evaluation techniques. The prepared modified beads were utilized as chiral stationary phase in high-performance liquid chromatography (HPLC). Those prepared by the in situ surface modification method tended to show higher chiral recognition ability than those by the classical copolymerization method, even if the equivalent amount of the chiral functional group was involved within polymer beads. Detailed chromatographic studies exhibited the in situ surface modification method could lead to polymeric methacrylamide functionality on the surface within relatively large pore size regions of the macroporous polymer beads, while the classical copolymerization method tended to form less polymeric surface functionality. The difference in the chiral surface functionality on both of macroporous polymer beads afforded drastic change in chromatographic chiral recognition ability. Complete resolution of a drug, thalidomide could be achieved on the chiral stationary phase with the polymeric chiral surface functionality, while no resolution was found on that with the monomeric one even if the same chiral methacrylamide was used as a modifier to prepare the chiral stationary phases. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2747–2757, 1997     

Preparations and properties of uniform size macroporous polymer beads prepared by two-step swelling and polymerization method utilizing divinyl succinate or divinyl adipate as a crosslinking agent

Uniform size macroporous polymer beads were prepared through a typical two-step swelling and polymerization method utilizing divinyl succinate or divinyl adipate as well as ethylene dimethacrylate as crosslinking agents. Stable macroporous polymer beads with good size monodispersity and a slightly nonspherical shape were obtained by homopolymerization of divinyl succinate in cyclohexanol as porogen. BET measurements indicated that the beads prepared by homopolymerization of divinyl succinate and copolymerization of divinyl succinate with vinyl p-tert-butylbenzoate, as well as homopolymerization of ethylene dimethacrylate had relatively large specific surface area. In contrast, copolymerization of divinyl succinate with methyl methacrylate afforded beads having a very small specific surface area. Similarly, all the beads prepared using divinyl adipate had very small specific surface area, while size exclusion chromatography in tetrahydrofuran suggested that these beads acquired a porous structure as a result of swelling. When used as packing materials for high-performance liquid chromatography, the beads prepared with divinyl adipate showed unexpected molecular recognition toward flat solutes in reversed phase liquid chromatography in contrast to those prepared with ethylene dimethacrylate. Copolymerizations with methyl methacrylate led to a decrease in molecular recognition, while those with vinyl p-tert-butylbenzoate enhanced the selectivity. © 1996 John Wiley & Sons, Inc.     

Facile synthesis of fluorescent quantum dot‐polymer nanocomposites via frontal polymerization

We report an available approach for quickly fabricating CdS QD‐polymer nanocomposites via frontal polymerization (FP). First, we synthesized (3‐mercaptopropyl)‐1‐trimethoxysilane (MPS)‐capped CdS quantum dots (QDs). With these MPS‐capped CdS QDs containing mercapto groups, MPS‐capped CdS QDs can be easily incorporated into a poly(N‐methylolacrylamide) (PNMA) matrix via FP. A variety of features for preparing QD‐polymer nanocomposites, such as initiator concentration and CdS concentration, were thoroughly investigated. The fluorescence properties of QD‐polymer nanocomposites prepared via FP are comparatively investigated on the basis of ultraviolet–visible (UV–vis) spectra and photoluminescence (PL) spectra. Results show that the PL intensity of QD‐polymer nanocomposites prepared via the FP method is superior to that obtained by the traditional batch polymerization (BP) method. In addition, by measuring the changes of PL intensity of the samples immersed in different concentrations of copper acetate solution, we found the QD‐polymer nanocomposites can be ultrasensitive to copper ions. This FP process can be exploited as a facile and rapid way for synthesis QD‐polymer nanocomposites on a large scale, avoiding the fluorescence quenching of nanocrystals during incorporation nanocrystals into polymer matrices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2170–2177, 2010     

Preparation of bovine hemoglobin-imprinted polymer beads via the photografting surface-modified method

Molecularly imprinted polymers (MIPs), based on photografting surface-modified polystyrene beads as matrices, were prepared with acrylamide as the functional monomer, bovine hemoglobin as the template molecule and N, N′-methylene bisacrylamide as the crosslinker in a phosphate buffer. The results of IR, scanning electron microscope (SEM) and elemental analyses demonstrated the formation of a grafting polymer layer on the polystyrene-bead surface. Subsequent removal of the template left behind cavities on the surface of the polymer matrix with a shape and an arrangement of functional groups having complementary binding sites with the original template molecule. The adsorption studies showed that the imprinted polymers have a good adsorption capacity and specific recognition for bovine hemoglobin as the template molecule. Our results demonstrated that the polymer prepared via the photografting surface-modified method exhibited better selectivity for the template. Attempts to employ the new method in molecular imprinting techniques may introduce new applications for MIPs and facilitate probable protein separation and purification. __________ Translated from Chemical Journal of Chinese Universities, 2008, 29(1): 64–70     

Efficient incorporation of quantum dots into porous microspheres through a solvent-evaporation approach

Quantum dot (QD)-encoded microspheres play an important role in suspension arrays by acting as supports for various reactions between biomolecules. With regard to QD-encoded microspheres utilized in suspension arrays, three key requirements are controllable size, abundant surface functional groups, and especially excellent fluorescence properties. In this paper, narrowly dispersed poly(styrene-co-divinylbenzene-co-methylacrylic acid) (PSDM) microspheres with specific size, surface carboxyl groups, and porous structures were synthesized by seeded copolymerization. In order to improve the incorporation efficiency of QDs within microspheres, we developed a swelling-evaporation approach in which the swelling process was combined with gradual evaporation of the solvent and thus gradual concentration of QDs in the dispersion solution. This approach was demonstrated to be an efficient method for improving the fluorescence intensity of resultant microspheres compared with the use of swelling alone. Moreover, the porous structure was shown to aid the penetration of QDs into the interiors of the microspheres. Through this approach, microspheres encoded with either single or multiple wavelength-emitting QDs were fabricated effectively. The suspension immunoassays were then founded based on the QD-encoded microspheres, by coating mouse antihuman chorionic gonadotropin as the probe for goat antimouse IgG detection. The positive results determined by Luminex 100 and the low cytotoxicity of the QD-encoded microspheres demonstrated their great potential in suspension arrays.     

载有量子点的介孔二氧化硅微球的制备与性能研究

采用自组装方法制备了一种磁核/介孔二氧化硅壳的微球, 调节体系中C₁₈TMS的加入量可控制介孔硅球的比表面积; 并通过化学修饰的方法对介孔微球表面进行巯基功能化修饰. 利用巯基与量子点之间的相互作用可将一定尺寸的量子点吸附于介孔二氧化硅球的孔中, 令介孔微球具有荧光效应; 同时可以利用吸附不同粒径的量子点的荧光光谱对介孔二氧化硅微球孔径的大小进行近似考察.     

Hydrophilic polymer supports for solid-phase synthesis: hydroxyl-functional beads of poly(vinylpyrrolidone)

Poly(vinylpyrrolidone) (PVP) has solubility properties that make it an attractive material for polymer-assisted synthesis applications; however, the naked polymer lacks reactive groups upon which to do chemistry. Furthermore, large differences in radical reactivity between 1-vinylpyrrolidin-2-one (NVP) and most other monomers lead to compositional drift during copolymerization, further complicating the introduction of functional groups into the polymer using this method. Monomers that are derivatives of NVP itself are expected to show smaller differences in radical reactivity and therefore provide a way of preparing PVP with adjustable properties. Three monomers introducing hydroxyl-functional groups and a new cross-linker, all derivatives of NVP, were synthesized and used in the preparation of a new type of hydrophilic polymer beads by aqueous suspension polymerization. These lightly cross-linked beads contain hydroxyl groups at a functional loading of 0.21-0.29 mmol/g and swell extensively in a broad range of solvents.     

Synthesis of amphiphilic triblock copolymers as multidentate ligands for biocompatible coating of quantum dots

One barrier to apply current tri-octylphosphine oxide (TOPO) based quantum dots (QDs) to biomedical imaging is that the TOPO on TOPO-QDs can be replaced by the proteins in living system, which may cause the degradation of QDs and/or deactivation of protein. In order to develop biocompatible optical imaging agents, a novel triblock copolymer, designed as a multidentate ligand, was synthesized to coat quantum dot nanocrystals (QDs). The copolymer consists of a polycarboxylic acid block at one end and a polythiol block at the other end with an intervening cross-linked poly(styrene-co-divinylbenzene) block bridging the ends. The multiple mercapto groups from the polythiol block act as multidentate ligands to stabilize QDs, while the polycarboxylic acid block improves the water solubility of QDs and offers reaction sites for surface modification or conjugation with bimolecules. The cross-linked poly(styrene-co-divinylbenzene) block provides a densely compacted hydrophobic shell. This shell will act as a barrier to inhibit the degradation of QDs by preventing the diffusion of ions and small molecules into the core of QDs. This new multidentate polymer coating facilitates the transfer of QDs from organic solvent into aqueous phase. The QDs directly bound to multidentate mercapto groups instead of TOPO are less likely to be affected by the mercapto or disulfide groups within proteins or other biomolecules. Therefore, this research will provide an alternative coating material instead of TOPO to produce QDs which could be more suitable for in vivo use under complex physiological conditions.     

Synthesis of highly monodisperse quantum dot‐loaded polymer beads by impregnation and precipitation techniques

A novel approach to the synthesis of highly monodisperse quantum dot‐loaded polymer beads by combining impregnation and precipitation techniques was reported. The monodisperse poly(glycidyl methacrylate) (PGMA) beads were first synthesized by dispersion polymerization. Then, the PGMA beads were chemically modified to generate carboxyl groups, and impregnation of cadmium ions (Cd²⁺) inside the beads. Subsequently, the cadmium ions were reacted with thioacetamide to form cadmium sulfide (CdS) quantum dots within the polymer beads. The morphology, structure, and properties of CdS quantum dot‐loaded polymer beads were studied by field emission scanning electron microscope (SEM), transmission electron microscope, fluorescence spectrophotometer, fluorescence microscope, Fourier transform infrared spectroscopy, powder X‐ray diffraction, and thermogravimetric analysis. The results indicated that the CdS quantum dot‐loaded polymer beads had an average size of 1.4 μm, and were highly monodisperse. More interestingly, the CdS quantum dots distributed evenly within the polymer beads, which provide very strong fluorescence intensity. The existence of carboxyl groups on the quantum dot‐loaded polymer beads was measured quantitatively, and was found to be 0.2 mmol/g. These CdS quantum dot‐loaded polymer beads involving functional carboxyl groups would have potential applications in biological immunoassay and photoelectronic fields. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Molecularly Imprinted Polymer Coated Quantum Dots for Multiplexed Cell Targeting and Imaging

Advanced tools for cell imaging are of great interest for the detection, localization, and quantification of molecular biomarkers of cancer or infection. We describe a novel photopolymerization method to coat quantum dots (QDs) with polymer shells, in particular, molecularly imprinted polymers (MIPs), by using the visible light emitted from QDs excited by UV light. Fluorescent core–shell particles specifically recognizing glucuronic acid (GlcA) or N‐acetylneuraminic acid (NANA) were prepared. Simultaneous multiplexed labeling of human keratinocytes with green QDs conjugated with MIP‐GlcA and red QDs conjugated with MIP‐NANA was demonstrated by fluorescence imaging. The specificity of binding was verified with a non‐imprinted control polymer and by enzymatic cleavage of the terminal GlcA and NANA moieties. The coating strategy is potentially a generic method for the functionalization of QDs to address a much wider range of biocompatibility and biorecognition issues.     

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。     

Encapsulation of emitting CdTe QDs within silica beads to retain initial photoluminescence efficiency

Highly luminescent silica beads (30 nm-2 mum slashed circle) incorporating CdTe quantum dots (QDs) were prepared via a two-step preparation procedure, namely a modified St?ber synthesis and a subsequent reverse micelle route. In the modified St?ber synthesis, the silica molecules are deposited on the surface of the QDs. After this first step, these coated QDs were incorporated into silica beads via a reverse micelle route. Inductively coupled plasma analysis revealed a red-emitting silica bead of 30 nm in diameter thus prepared encapsulated roughly 14 CdTe QDs. These glass beads (30-40 nm slashed circle) retained the initial photoluminescence (PL) efficiencies of the colloidal QDs (27 and 65% for the green- and red-emitting beads, respectively). The protection of QDs by a silica layer at the first step, together with the short total reaction time, is the main reason for the retention of the PL efficiency. The size of the glass beads can be easily controlled over the wide range by adjusting the injection speed and the ratio of chemicals used for the reverse micelle preparation. Since the original efficiency was maintained in the beads and is the highest ever reported for QD-containing silica beads, the method presented here is of significant importance for applications of silica beads to biological probes.     

Focus on quantum dots as potential fluorescent probes for monitoring food toxicants and foodborne pathogens

Water-soluble quantum dots (QDs) are fluorescent semiconductor nanoparticles with narrow, very specific, stable emission spectra. Therefore, the bioconjugation of these QDs for biological fluorescent labeling may be of interest due to their unique physical and optical properties as compared to organic fluorescent dyes. These intrinsic properties of QDs have been used for the sensitive detection of target analytes. From the viewpoint of ensuring food safety, there is a need to develop rapid, sensitive and specific detection techniques to monitor food toxicants in food and environmental samples. Even trace levels of these toxicants can inadvertently enter the food chain, creating severe health hazards. The present review emphasizes the application of water-soluble bioconjugated QDs for the detection of food contaminants such as pesticides, pathogenic bacterial toxins such as botulinum toxin, enterotoxins produced by Staphylococcus aureus, Escherichia coli, and for the development of oligonucleotide-based microarrays. This review also emphasizes the application of a possible resonance energy transfer phenomenon resulting from nanobiomolecular interactions obtained through the bioconjugation of QDs with biomolecules. Furthermore, the utilization of significant changes in the spectral behavior of QDs (attributed to resonance energy transfer in the bioconjugate) in future nanobiosensor development is also emphasized.     

Introduction of Quantum Dots into PNIPAM microspheres by precipitation polymerization above LCST

Amphiphilic polymers having different polymerizable functional groups were synthesised and investigated as coatings for semiconductor nanoparticles (Quantum Dots, QDs). QDs coated with hydrophobic ligands were successfully transferred into water using these polymers and the assemblies were co-polymerized with N-isopropylacrylamide (NIPAM) by a precipitation polymerization method. In the resulting hybrid microspheres, QDs were uniformly distributed within the PNIPAM matrix. The influence of different polymerizable groups and counter ions of the amphiphilic polymer on the copolymerization process were investigated.     

温度对聚酰胺-胺树形分子模板法制备CdS量子点的影响

为了研究温度对聚酰胺-胺(PAMAM)树形分子的模板法制备硫化镉(CdS)量子点的影响, 以4.5代(G4.5, 64个甲酯端基)PAMAM树形分子为模板, 在－10～30 ℃的温度范围内制备了分散良好的CdS量子点. 用透射电子显微镜(TEM)表征了CdS量子点的形貌、尺寸; 用紫外-可见光谱(UV-Vis)和光致发光光谱(PL)表征了CdS量子点的光学性能. 发现在相同条件下, 制备温度从－10 ℃升高到30 ℃, CdS量子点粒径从1.8 nm增大到3.4 nm, 其中在10 ℃时制备的量子点的尺寸分布最窄; CdS量子点的吸收和发射光谱均随温度增大而红移, 其中10 ℃时制备的量子点的室温光致发光效率最高. 这表明制备温度决定了树形分子的配位基团与Cd^2＋的分离速度, 并影响了CdS量子点的成核和生长过程, 从而最终决定了CdS量子点的尺寸及尺寸分布、光致发光颜色和发光效率.     

硅胶表面亮菌甲素分子印迹聚合物的制备及其性能研究

采用光接枝印迹方法,在硅胶微球表面制备了以亮菌甲素为模板分子、2-乙烯基吡啶为功能单体的分子印迹聚合物,采用荧光法优选了功能单体及比例,进一步用荧光法对印迹聚合物的吸附特性和印迹效率进行评价.结果表明.该印迹聚合物对模板分子具有特异吸附性能,印迹效率为48.6%.     

光接枝表面修饰法制备牛血红蛋白的分子印迹微球

聚苯乙烯球载体表面经引发转移终止剂修饰后, 采用光接枝表面印迹方法制备了以牛血红蛋白(BHb)为模板分子、丙烯酰胺为功能单体和N,N′-亚甲基双丙烯酰胺为交联剂的分子印迹聚合物微球(MIP). 进一步采用红外光谱(IR)、扫描电子显微镜(SEM)和元素分析对聚合物微球进行了表征, 证实了载体表面成功地接枝了分子印迹层, 并研究了其吸附性能和分子识别选择性能. 结果表明, 采用光接枝表面修饰法制备的分子印迹微球对模板分子有着很好的吸附容量和识别选择性.     

Nanocomposites based on crosslinked polyacrylic latex/silver nanoparticles for waterborne high‐performance antibacterial coatings

Functional polymer/AgNPs nanocomposites have been prepared. Silver nanoparticles (NPs) were synthesized to which polyacrylamide, PAAm, was covalently bound. PAAm was synthesized via a RAFT reaction and carried thiol and carboxylic acid end groups. Thiol was used to bind the polymer to the metal surface and carboxyl for further reactions. The AgNPs were used in a post‐crosslinking reaction with a separately synthesized poly(butyl acrylate‐co‐methyl methacrylate)/polyglycidyl methacrylate core/shell latex bearing epoxy functional groups. Dynamic mechanical analysis showed that the functional AgNPs effectively crosslinked the latex polymer, and that the final product had excellent mechanical strength. Antibacterial tests revealed that the nanocomposite films had strong antibacterial activity against all types of the bacteria and the immobilization of silver NPs by crosslinking retarded the release of silver in comparison to the uncrosslinked ones. With the presented method, it is possible to obtain ductile antibacterial nanocomposites to be used as waterborne functional coatings. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1435–1447     

基于聚合物多齿配体的高性能CdTe量子点的微波水相合成

针对当前水相合成的量子点(QDs)光性能与稳定性等方面存在的不足,发展了基于聚合物多齿配体的水相制备策略.利用巯基修饰的聚丙烯酸(PAA-SH)作为多齿配体代替常用的巯基丙酸等单齿配体,结合微波辅助加热制备了CdTe量子点,研究了多齿配体对量子点的生长机制与荧光性能的影响.以PAA-SH为配体制备的CdTe量子点荧光性能优异(荧光量子效率(PLQY)可达75%),流体力学直径较小(~10 nm),稳定性也有明显提高.基于聚合物多齿配体的量子点制备技术有助于实现生物医学研究中急需的兼具高亮度、高稳定性、小尺寸等特征的高性能量子点生物探针的制备.