基于双色荧光传感器的癌细胞成像及microRNA定量检测

癌细胞中microRNA(miRNA)的灵敏成像对于疾病的诊断治疗具有重要意义,其中miRNA-21通常在多种癌细胞中异常表达.本文将DNA功能化的金纳米颗粒与发射波长分离的荧光染料FAM和Cy5. 5修饰的DNA通过含有光控基团PC-linker的DNA4作为桥梁进行自组装,构建了纳米传感器GDC.将302 nm紫外光作为启动开关,用其照射该体系时,Cy5. 5修饰的DNA3被释放,其荧光强度可作为内参比信号,用于标定进入细胞的组装体含量;细胞中miRNA-21作为催化分子,与外加燃料Fuel DNA共同作用下可实现催化放大,FAM修饰的DNA2被释放且被猝灭的荧光信号得以恢复,并作为检测信号.通过2种荧光信号强度(FL)的检测及FL_FAM/FL_{Cy5. 5}比值的计算,达到定量分析细胞中miRNA含量的目的.该体系可扣除因细胞内组装体含量不同造成的背景信号误差,不仅能显著提高检测准确度,还因存在催化循环而大大降低了检出限,比传统方法至少降低了3个数量级.该传感器的检出限为23. 1 pmol/L,通过定量计算得出He La细胞中miRNA的...     

Optical nanosensors--an enabling technology for intracellular measurements

Optical nanosensors have been designed to utilise the sensitivity of fluorescence for making quantitative measurements in the intracellular environment, using devices that are small enough to be inserted into living cells with a minimum of physical perturbation. Advantages over widely used fluorescence dye based methods are observed because the nanosensor matrix imparts two key benefits; (1) protection of the sensing component from interfering species within the intracellular environment and (2) protection of the intracellular environment from any toxic effects of the sensing component. This Highlight article discusses the recent developments in nanosensor technology and investigates the use of more complex sensing schemes that will expand the range of analytes that can be detected and quantified.     

Optical nanosensor design with uniform pore geometry and large particle morphology

Appropriate design of nanosensors for optically selective, sensitive sensing systems is needed for naked-eye detection of pollutants for environmental cleanup of toxic heavy-metal ions. Mesostructured materials with two- or three-dimensional (2D or 3D) geometries and large particle morphologies show promise as probe carriers, and can therefore be used to reproducibly fabricate uniformly packed nanosensors. This is the first report on the effects of significant key properties of the mesostructured carriers, such as morphology, geometry, and pore shape, on the functionality of optical nanosensor designs. Such mesostructured sensors with superior physical characteristics can be used as components in sensing systems with excellent stability and sensitivity, and with rapid detection response. The nanosensor design can enhance the selectivity even at low concentrations of the pollutant target ions (nanomolar level). Among the nanosensors developed here, the large pore-surface grains of highly ordered 3D monoliths (HOM) exhibited a high adsorption capability of the Pyrogallol Red probe and high accessibility to analyte ion transport, leading to possible naked-eye detection of Sb(III) ions at concentrations as low as 10(-9) mol dm(-3) and at a wide detection range of 0.5 ppb to 3 ppm. A key finding in our study was that our mesostructured nanosensor designs retained highly efficient sensitivity without a significant increase in kinetic hindrance, despite the slight decrease of the specific activity of the electron acceptor/donor strength of the probe functional group after several regeneration/reuse cycles. The results, in general, indicate that large-scale reversibility of optical nanosensors is feasible in such metal-ion sensing systems.     

Fluorescent polyacrylamide nanoparticles for naproxen recognition

We present the synthesis of fluorescent acrylamide nanoparticles (FANs) capable of recognizing non-steroidal anti-inflammatory drugs (NSAIDs) in buffered aqueous solutions. Within this important group, we selected naproxen, one of the 2-arylpropionic acids (profens), due to its use for the treatment of moderate pain, fever, and inflammation. The nanosensors were prepared under mild conditions of inverse microemulsion polymerization using aqueous acrylamide as the monomer and N,N′-methylenebisacrylamide as the cross-linker, employing the surfactants polyoxyethylene-4-lauryl ether (Brij?30) and sodium bis(2-ethylhexyl)sulfosuccinate in hexane. Furthermore, a fluorescent monomer, (E)-4-[4-(dimethylamino)styryl]-1-[4-(methacryloyloxymethyl)benzyl]pyridinium chloride (mDMASP) has been synthesized and incorporated into the nanoparticles. The nanosensors exhibit a broad absorbance at around 460 nm and a structureless fluorescence band with maximum at 590 nm in 0.5 M phosphate buffer (pH = 7.2). The recognition process is performed on the basis of ionic interactions which are monitored by the fluorescence increase at 590 nm upon addition of different concentrations of naproxen. The FANs show a size distribution in the range of 20–80 nm, with a hydrodynamic diameter of 34 nm. In order to assess the selectivity of the FANs, a systematic study was conducted on the effect produced by drugs and biomolecules that could interfere with the analysis of naproxen.     

Development of molecularly ımprınted polymer based quartz crystal mıcrobalance nanosensor for the determınatıon of tryptophan

ABSTRACT

In this study, a quartz crystal microbalance (QCM) nanosensor was prepared to detect tryptophan. QCM nanosensor was prepared through the formation of tryptophan memories on the gold surface of QCM electrode using Methacryloylamidohistidine-Cu(II)-tryptophan ([MAH-Cu(II)]-tryptophan) pre-organised monomer system. The designed pre-organised monomer system was characterised by use of Fourier Transform Infrared (FTIR) and Atomic Force Microscope (AFM) was used to characterise the QCM nanosensors. After the characterisation studies, imprinted and non-imprinted sensors were connected to QCM system to determine the binding of the target molecule, selectivity and the detection of the amount of target molecule in real samples. The results showed that the imprinted QCM nanosensor had high selectivity for tryptophan.     

A chloride ion nanosensor for time-resolved fluorimetry and fluorescence lifetime imaging

In this work, the first CdSe/ZnS quantum dot (QD) photoluminescence lifetime based chloride ion nanosensor is reported. The acridinium dication lucigenin was self-assembled on the surface of negatively charged mercaptopropionic acid capped QDs to achieve QD-lucigenin conjugates. Upon attachment, a drastic decrease of the photoluminescence lifetime of both QD nanoparticles and lucigenin is observed by virtue of a charge transfer mechanism. Since lucigenin is a chloride-sensitive indicator dye, the photoluminescence decay of QD-lucigenin conjugates changes by adding chloride ion. The photoluminescence lifetime of the QDs in the conjugate increases after reacting with Cl(-), but also shows a concomitant decrease in the lucigenin lifetime immobilized on the surface. The photoluminescence lifetime of QD-lucigenin nanosensors shows a linear response in the Cl(-) concentration range between 0.5 and 50 mM. Moreover, the ratio τ(ave)(QD)/τ(ave)(luc) can be used as an analytical signal since the lifetime ratio presents a linear response in the same Cl(-) concentration range. The system also shows good selectivity towards most of the main anions and molecules that can be found in biological fluids. These nanosensors have been satisfactorily applied for Cl(-) determination in simulated intracellular media with high sensitivity and high selectivity. Finally, we demonstrate the potential application of the proposed nanosensor in confocal fluorescence lifetime imaging (FLIM). These results show the promising application of the QD-lucigenin nanosensors in FLIM, particularly for intracellular sensing, with the invaluable advantages of the time-resolved fluorescence techniques.     

可视化辅助碳点荧光比色法检测水中痕量汞离子

利用巯基功能化碳点(M-CDs)构建用于检测水中Hg^2+的荧光探针。红外光谱证实M-CDs被巯基(-SH)成功修饰,透射电镜显示M-CDs的平均粒径约为4.88 nm。XRD晶型表征显示M-CDs具有类石墨烯结构。由于银硫醇盐的团聚作用,M-CDs溶液中加入Ag^+可快速形成M-CDs/Ag的棕色沉淀,并引起M-CDs的荧光猝灭。用PBS缓冲液(0.01 mol/L,pH 7.4)溶解沉淀物而形成检测Hg^2+的荧光传感器。在传感体系中加入Hg^2+后,M-CDs荧光明显恢复。在Hg^2+浓度为0.01~0.55 nmol/L范围内,检测体系荧光恢复强度与Hg^2+浓度成良好线性关系,检测限(LOD,3σ/k)4.2 pmol/L。该探针对Hg^2+表现出良好的选择性,同时可以通过可视化辅助判断探针的选择性。该传感器可用于对实际水样的检测,为Hg^2+污染监测提供技术依据。     

Quantum dot photoluminescence lifetime-based pH nanosensor

The first CdSe/ZnS quantum dot photoluminescence lifetime-based pH nanosensor has been developed. The average lifetime of mercaptopropionic acid-capped QD nanosensors showed a linear response in the pH range of 5.2-6.9. These nanosensors have been satisfactorily applied for pH estimation in simulated intracellular media, with high sensitivity and high selectivity toward most of the intracellular components.     

Fluorescence quenching of TMR by guanosine in oligonucleotides

Nucleotide-specific fluorescence quenching in fluorescently labeled DNA has many applications in biotechnology. We have studied the inter- and intra-molecular quenching of tetramethylrhodamine (TMR) by nucleotides to better understand their quenching mechanism and influencing factors. In agreement with previous work, dGMP can effectively quench TMR, while the quenching of TMR by other nucleotides is negligible. The Stern-Volmer plot between TMR and dGMP delivers a bimolecular quenching constant of K _s = 52.3 M⁻¹. The fluorescence of TMR in labeled oligonucleotides decreases efficiently through photoinduced electron transfer by guanosine. The quenching rate constant between TMR and guanosine was measured using fluorescence correlation spectroscopy (FCS). In addition, our data show that the steric hindrance by bases around guanosine has significant effect on the G-quenching. The availability of these data should be useful in designing fluorescent oligonucleotides and understanding the G-quenching process.     

Design and preparation of imprinted surface plasmon resonance (SPR) nanosensor for detection of Zn(II) ions

A novel Zn(II) ions imprinted poly (2-hydroxyethyl Methacrylate-N-methacryloyl-(L)-histidine methyl ester) poly(HEMAH) surface plasmon resonance (SPR) nanosensor were designed for detection of Zn(II) ions in aqueous solution and artificial plasma providing a low cost, rapid and reliable results compared to other techniques such as atomic absorption spectroscopy, inductively coupled plasma-mass spectrometer, X-ray fluorescence with synchrotron radiation. Zn(II) ions imprinted nanofilm on the SPR chip surface was synthesized by bulk polymerization. Characterization of Zn(II) ions imprinted nanosensor was performed by contact angle measurement, atomic force microscopy (AFM), ellipsometry and Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR). Designed nanosensor was applied for selective detection of Zn(II) ions in aqueous solution within the range of 0.5–1.0?µg/mL. The limit of detection (LOD) and limit of quantification (LOQ) were calculated as 0.19 and 0.64?ng/mL, respectively. Association kinetics analysis, Scatchard, Langmuir, Freundlich, Langmuir–Freundlich, Tempkin and Dubinin-Radushkevich isotherms were analyzed to the experimental data in order to identify the adsorption behavior. The selectivity of the SPR nanosensor was examined by using competitive metal ions such as Cd(II), Cu(II), Pb(II), and Fe(II). To evaluate the imprinting effect of Zn(II) ions imprinted (MIP) and non-imprinted (NIP) nanosensor was also prepared as the control. Repeatability of the response signal was tested by four times adsorption–desorption–regeneration cycle.     

SERS nanosensors that report pH of endocytic compartments during FcεRI transit

Recently, the development of an IgE receptor (FcεRI)-targeted, pH-sensitive, surface-enhanced Raman spectroscopy (SERS) nanosensor has been demonstrated by Nowak-Lovato and Rector (Appl Spectrosc 63:387–395, 2009). The targeted nanosensor enables spatial and temporal pH measurements as internalized receptors progress through endosomal compartments in live cells. Trafficking of receptor-bound nanosensors was compared at physiological temperature (37 °C) versus room temperature (25 °C). As expected, we observed markedly slower progression of receptors through low-pH endocytic compartments at the lower temperature. We also demonstrate the utility of the nanosensors to measure directly changes in the pH of intracellular compartments after treatment with bafilomycin or amiloride. We report an increase in endosome compartment pH after treatment with bafilomycin, an H⁺ ATPase pump inhibitor. Decreased endosomal luminal pH was measured in cells treated with amiloride, an inhibitor of Na⁺/H⁺ exchange. The decrease in amiloride-treated cells was transient, followed by a recovery period of approximately 15–20 min to restore endosomal pH. These experiments demonstrate the novel application of Raman spectroscopy to monitor local pH environment in live cells with the use of targeted SERS nanosensors.     

Protamine/heparin optical nanosensors based on solvatochromism

Optical nanosensors for the detection of polyions, including protamine and heparin, have to date relied upon ion-exchange reactions involving an analyte and an optical transducer. Unfortunately, due to the limited selectivity of the available ionophores for polyions, this mechanism has suffered from severe interference in complex sample matrices. To date no optical polyion nanosensors have demonstrated acceptable performance in serum, plasma or blood. Herein we describe a new type of nanosensor based on our discovery of a “hyper-polarizing lipophilic phase” in which dinonylnaphthalenesulfonate (DNNS⁻) polarizes a solvatochromic dye much more than even an aqueous environment. We have found that the apparent polarity of the organic phase is only modulated when DNNS⁻ binds to large polyions such as protamine, unlike singly charged ions that lack the cooperative binding required to cause a significant shift in the distribution of the polarizing DNNS⁻ ions. Our new sensing mechanism allows solvatochromic signal transduction without the transducer undergoing ion exchange. The result is significantly improved sensitivity and selectivity, enabling for the first time the quantification of protamine and heparin in human plasma using optical nanosensors that correlates with the current gold standard analysis method, the anti-Xa factor assay.

Novel optical nanosensors for the selective detection of the polycationic protamine based on solvatochromic signal change allow one to detect heparin in plasma.     

Ion-pair high-performance liquid chromatography with diode array detection coupled to dual electrospray atmospheric pressure chemical ionization time-of-flight mass spectrometry for the determination of nucleotides in baby foods

A liquid chromatography with diode array detection coupled to dual electrospray atmospheric pressure chemical ionization time-of-flight mass spectrometry (HPLC/ESI-APCI-TOF-MS) method is described for the rapid determination of five monophosphate nucleotides (cytidine 5′-monophosphate, uridine 5′-monophosphate, adenosine 5′-monophosphate, inosine 5′-monophosphate and guanosine 5′-monophosphate) in baby foods. The method is based on the deproteinisation of foods and direct analysis of nucleotides by ion-pair HPLC using isocratic elution with a mobile phase of 5% (v/v) methanol and 95% (v/v) 0.1 M formate buffer (pH 5.5) containing 0.01 M N,N-dimethylhexylamine (DMHA) at a flow-rate of 0.7 mL min⁻¹. The HPLC was hyphenated with two different detection systems, photodiode-array (DAD) and ESI-APCI-TOF-MS in negative mode. The method was validated for linearity, detection and quantitation limits, selectivity, accuracy and precision. The recoveries obtained for spiked samples were satisfactory for all the analytes. The method was successfully applied to the analysis of nucleotides in different baby and/or functional food samples, as cereals, purees and dairy products. A study was also carried out on the stability of nucleotides in acidified dairy infant food with pasteurized yoghourt and follow-on formulae samples stored at room temperature and at 30 °C.     

2-Amino-5,7-dimethyl-1,8-naphthyridine as a fluorescent reagent for the determination of nitrite

A new fluorescent reagent 2-amino-5,7-dimethyl-1,8-naphthyridine (ADMND) was proposed for the determination of trace nitrite. The reaction is based on the diazotization of naphthyridine amine with nitrite to form a diazonium salt that hydrolyzed when boiling to give hydroxyl group substituted naphthyridine. Fluorescence quenching degree of ADMND by nitrite ion is linear in the nitrite concentration range of 1 x 10(-7) to 2.5 x 10(-6)mol l(-1) with a detection limit of 4.06 x 10(-8)mol l(-1). Reaction and determination acidity for nitrite is the same which made the method much simpler compared with the widely accepted fluorescence method with DAN as a fluorescence reagent.     

A functionalized gold nanoparticles and Rhodamine 6G based fluorescent sensor for high sensitive and selective detection of mercury(II) in environmental water samples

A gold-nanoparticles (Au NPs)-Rhodamine 6G (Rh6G) based fluorescent sensor for detecting Hg (II) in aqueous solution has been developed. Water-soluble and monodisperse gold nanoparticles (Au NPs) has been prepared facilely and further modified with thioglycolic acid (TGA). Free Rh6G dye was strongly fluorescent in bulk solution. The sensor system composing of Rh6G and Au NPs fluoresce weakly as result of fluorescence resonance energy transfer (FRET) and collision. The fluorescence of Rh6G and Au NPs based sensor was gradually recovered due to Rh6G units departed from the surface of functionalized Au NPs in the presence of Hg(II). Based on the modulation of fluorescence quenching efficiency of Rh6G-Au NPs by Hg(II) at pH 9.0 of teraborate buffer solution, a simple, rapid, reliable and specific turn-on fluorescent assay for Hg(II) was proposed. Under the optimum conditions, the fluorescence intensity of sensor is proportional to the concentration of Hg(II). The calibration graphs are linear over the range of 5.0 × 10⁻¹⁰ to 3.55 × 10⁻⁸ mol L⁻¹, and the corresponding limit of detection (LOD) is low as 6.0 × 10⁻¹¹ mol L⁻¹. The relative standard deviation of 10 replicate measurements is 1.5% for 2.0 × 10⁻⁹ mol L⁻¹ Hg(II). In comparison with conventional fluorimetric methods for detection of mercury ion, the present nanosensor endowed with higher sensitivity and selectivity for Hg(II) in aqueous solution. Mercury(II) of real environmental water samples was determined by our proposed method with satisfactory results that were obtained by atomic absorption spectroscopy (AAS).     

Synthesis of improved upconversion nanoparticles as ultrasensitive fluorescence probe for mycotoxins

Rare earth-doped upconversion nanoparticles (UCNPs) have promising potentials in biodetection due to their unique frequency upconverting capability and high detection sensitivity. This paper reports an improved UCNPs-based fluorescence probe for dual-sensing of Aflatoxin B1 (AFB1) and Deoxynivalenol (DON) using a magnetism-induced separation and the specific formation of antibody-targets complex. Herein, the improved UCNPs, which were namely NaYF₄:Yb/Ho/Gd and NaYF₄:Yb/Tm/Gd, were systematically studied based on the optimization of reaction time, temperature and the concentration of dopant ions with simultaneous phase and size controlled NaYF₄ nanoparticles; and the targets were detected using the pattern of competitive combination assay. Under an optimized condition, the advanced fluorescent probes revealed stronger fluorescent properties, broader biological applications and better storage stabilities compared to traditional UCNPs-based ones; and ultrasensitive determinations of AFB1 and DON were achieved under a wide sensing range of 0.001–0.1 ng ml⁻¹ with the limit of detection (LOD) of 0.001 ng ml⁻¹. Additionally, the applicability of the improved nanosensor for the detection of mycotoxins was also confirmed in adulterated oil samples.     

Dispersive solid-phase extraction for in-sorbent Fourier-transform infrared detection and identification of nerve agent simulants in analysis for verification of chemical weapon convention

The combination of dispersive solid-phase extraction (DSPE) and Fourier-transform infrared (FTIR) spectroscopy is presented for detection and quantification of markers and simulants of nerve agents. Hydrophilic–lipophilic balance (HLB) sorbent was used for extraction and enrichment of organophosphonates from water. When the extraction efficiency of DSPE was compared with that of conventional solid-phase extraction (SPE), DSPE was more efficient. Extraction conditions such as extraction time, and type and quantity of sorbent material were optimized. In DSPE, extracted analytes are detected and quantified on the sorbent using FTIR as analytical technique. Absorbance in FTIR due to P–O–C stretching was used for detection and quantification. Infrared absorbance of different analytes were compared by determining their molar absorptivities (ε _max). Quantitative analyses were performed employing modified Beer’s law, and relative standard deviations (RSDs) for intraday repeatability and interday reproducibility were found to be in the range 0.30–0.90% and 0.10–0.80% respectively. The limit of detection (LOD) was 5–10 μg mL⁻¹. The applicability of the method was tested with an unknown sample prepared by mimicking the sample obtained in an international official proficiency test.     

Sensitive determination of nucleotides and polynucleotides based on the fluorescence quenching of the Tb3+-Tiron complex

 A sensitive method using fluorescence quenching for the determination of nucleotides (ATP, ADP, AMP, CTP, UTP) and polynucleotides[poly(A), poly(I), poly(U)] is proposed. It is based on the ability of nucleotides and polynucleotides to inhibit the formation of a strongly fluorescent complex of Tb³⁺ ion with Tiron. The possibilities of spectrofluorimetric measurements of these systems were studied under optimal conditions (pH 6.9 in hexamethylene tetramine-HCl buffer, 1.2×10^-6 mol/L of Tb³⁺, 4.0×10^-6 mol/L of Tiron, λ_ex=317 nm, λ_em=546 nm). The results showed that the Tb³⁺-Tiron complex could be used as a fluorescence test for the phosphate moieties of nucleotides and polynucleotides. The detection limits are 0.3, 1.2, 3.7, 0.2, 0.3, 1.1, 0.6 and 0.9 ng/mL for ATP, ADP, AMP, CTP, UTP, poly(A), poly(I), and poly(U), respectively. The relative standard deviations (6 replicates) are within 4.0% in the middle of the linear range. The fluorescence quenching mechanism of these systems is also discussed. Received: 16 July 1996 / Revised: 13 November 1996 / Accepted: 13 November 1996     

Opto-electrochemical nanosensor array for remote DNA detection

A high-density array of opto-electrochemical nanosensors is presented for remote DNA detection. It was fabricated by chemical etching of a coherent optical fibre bundle to produce a nanotip array. The surface of the etched bundle was sputter-coated with a thin ITO layer which was eventually insulated by an electrophoretic paint. The fabrication steps produced a high-density array of electrochemical nanosensors which retains the optical fibre bundle architecture and its imaging properties. A DNA probe was then immobilized on the nanosensor array surface in a polypyrrole film by electropolymerisation. After hybridisation with the complementary sequence, detection of the strepavidin-R-phycoerythrin label is performed by fluorescence imaging through the optical fibre bundle itself. Control experiments and regeneration steps have also been successfully demonstrated on this nanostructured opto-electrochemical platform.     

A fluorescent PEBBLE nanosensor for intracellular free zinc

The development and characterisation of a fluorescent optical PEBBLE (Probe Encapsulated By Biologically Localised Embedding) nanosensor for the detection of zinc is detailed. A ratiometric sensor has been fabricated that incorporates two fluorescent dyes; one is sensitive to zinc and the other acts as a reference. The sensing components are entrapped within a polymer matrix by a microemulsion polymerisation process that produces spherical sensors that are in the size region of 20 to 200 nm. Cellular measurements are made possible by the small sensor size and the biocompatibility of the matrix. The effects of reversibility, photobleaching and leaching have been examined, as well as the selectivity towards zinc over other cellular ions such as Na+, Ca2+, K+, and Mg2+. The dynamic range of these sensors was found to be 4 to 50 microM Zn2+ with a linear range from 15 to 40 microM. The response time for the PEBBLE is less than 4 s and the sensor is reversible. In addition, the nanosensors are photostable and leaching from the matrix, determined using a novel method, is minimal. These sensors are capable of real-time inter- and intra-cellular imaging and are insensitive to interference from proteins.