A Novel Fluorescent Biosensor for Detection of Silver Ions Based on Upconversion Nanoparticles

In this paper, we report a simple and sensitive fluorescent biosensor for the quantitative analysis of silver ions (Ag⁺) by using NaYF₄:Yb³⁺, Tm³⁺ upconversion nanoparticles (UCNPs). Ag⁺ could oxidize o-phenylenediamine (OPD) to the oxidized OPD (oxOPD) directly. The fluorescence of UCNPs can be significantly quenched by oxOPD through inner filter effects (IFE). Under the optimized conditions, the Ag⁺ concentration is proportional to the changes of the fluorescence intensity of UCNPs. The proposed method shows high selectivity and Ag⁺ could be quantitatively detected in the range of 0 to 0.5 mM with a low detection limit of 33 nM for Ag⁺. The selectivity and sensitivity of the detection can also be satisfactory. More importantly, this method has potential in practical application to detect Ag⁺ in real samples without interference.     

A FRET Fluorescent Sensor for Ratiometric and Visual Detection of Sulfide Based on Carbon Dots and Silver Nanoclusters

In this work, the fluorescent sensor based on fluorescence resonance energy transfer (FRET) and electrostatic interaction (EI) was prepared for the ratiometric and visual detecting S^2–. The FRET fluorescent sensor consists of two fluorophores, with carbon dots (CDs) as energy donors and silver nanoclusters (Ag NCs) as acceptors. At 390 nm excitation, CDs and Ag NCs showed two well-separated peaks at 445 nm and 660 nm, separately. The existence of S^2– caused the red fluorescence at 660 nm to be quenched, whereas the blue fluorescence at 445 nm was restored, and the fluorescence color of the ratiometric sensor changed from pink to blue. It could be employed in ratiometric and visual detecting S^2–. The linear range of quantitative detection S^2– was 0.5–100 μM, and its detection limit was 0.35 μM. CDs-Ag NCs could be used for detecting S^2– in mineral water and tap water. The results showed that the FRET ratiometric fluorescent sensor exhibits good anti-interference and high selectivity for detecting S^2– in environmental water samples.

     

A BODIPY Based Fluorescent Probe for the Rapid Detection of Hypochlorite

A new boron-dipyrromethene (BODIPY) fluorescent dye aimed at sensitively detecting hypochlorite anion (ClO^?) has been designed, synthesized and characterized. The probe is comprised of a BODIPY fluorophore unit and a ClO^? specific reactive group of amidoxime. The addition of hypochlorite results in a red-shift of absorption and emission spectra of the probe accompanied by a decrease of intensity and spectra changes (A₅₀₀ and 1/I₅₁₂) of the probe can achieve a good linearity to the concentration of ClO^?. The fluorescence probe can react to ClO^? rapidly (within 60 s) in a wide pH range (4–10) with high sensitivity (detection limit of 6.81 μM) and selectivity. The reaction mechanism has been proposed and confirmed by MS analysis, ClO^? anion oxidizes amidoxime moiety to hydroxyl group and hydroxyl group is further oxidized to formyl group in the formation of a corresponding aldehyde compound. In addition, the probe has also been successfully applied to detect ClO^? in tap water and river water samples by spiking a known amount of standard ClO^?.     

A Colorimetric and Fluorescent Probe Based on Michael Acceptor Type Diketopyrrolopyrrole for Cyanide Detection

A new probe 1 was synthesized by incorporating an α,β-unsaturated ketone to a diketopyrrolopyrrole fluorophore. The probe exhibited a selective and sensitive response to cyanide against other anions. Addition of CN^? aqueous solution to 1 resulted in a rapid color change from pink to light yellow together with a blue shift from 518 to 421 nm, while other anions did not induce any significant color change. Furthermore, the Michael addition of cyanide to 1 elicited 98% fluorescence quenching at 608 nm, which constituted the fluorescence signature for cyanide detection. The detection limit was 0.67 μM using the fluorescence spectra changes, which was far lower than the WHO guideline of 1.9 μM. Moreover, 1-based test strips could successfully detect CN^? solutions.     

Automated Detection and Characterization of Multiple Sclerosis Lesions in Brain MR Images

In the present study an automatic algorithm for detection and contouring of multiple sclerosis (MS) lesions in brain magnetic resonance (MR) images is introduced. This algorithm automatically detects MS lesions in axial proton density, T₂-weighted, gadolinium enhanced, and fast fluid attenuated inversion recovery (FLAIR) brain MR images. Automated detection consists of three main stages: (1) detection and contouring of all hyperintense signal regions within the image; (2) partial elimination of false positive segments (defined herein as artifacts) by size, shape index, and anatomical location; (3) the use of an artificial neural paradigm (Back-Propagation) for final removal of artifacts by differentiating them from true MS lesions. The algorithm was applied to 45 images acquired from 14 MS patients. The algorithm’s sensitivity was 0.87 and the specificity 0.96. In 34 images, 100% of the lesions were detected. The algorithm potentially may serve as a useful preprocessing tool for quantitative MS monitoring via magnetic resonance imaging.     

基于无标记荧光共振能量转移的microRNA检测方法研究

利用以阳离子共轭聚合物为能量供体的荧光共振能量转移(FRET)策略和滚环扩增放大技术,建立了一种新型的microRNA(miRNA)检测方法。阳离子共轭聚合物采用聚[(9,9-双(6’-N,N,N-三乙基铵)己基)亚芴基亚苯基二溴化物](PFP)。PFP是一种由大量吸光单元共轭而成的阳离子聚合物,具有独特的光捕获和荧光增强性能,可以和带有负电荷的DNA通过静电作用相互结合。SG是一种能够结合于所有双链DNA双螺旋小沟区域的染料,其在游离状态下,荧光微弱,但一旦与双链DNA结合后,荧光会大大的增强。首先,设计了一条可与目标分子特异性杂交的锁式探针和与RCA产物序列互补的DNA链。当体系中存在miRNA时,在T4 DNA连接酶作用下,锁式探针连接成环;随后,在phi29 DNA聚合酶和dNTPs共同作用下,在miRNA的3’端滚环扩增出一条与锁式探针序列互补的长单链DNA,所得产物与互补DNA链杂交形成双链DNA(dsDNA)。此时SG作为FRET受体掺入其中,形成SG-dsDNA共同体。随后, SG-dsDNA与PFP因静电相互作用而紧密接近,由于PFP的发射光谱与SG的激发光谱有重叠,因此二者之间可以发生FRET现象。反之,当体系中不存在miRNA时,挂锁探针则无法连接成环,阻止了扩增反应的进行及其产物与互补DNA链的杂交反应。加入SG后,由于SG与单链DNA的结合能力很弱, SG则游离于溶液中,不会与PFP发生有效的FRET。因此目标分子的浓度与体系的FRET效率直接相关。以let 7a作为待测miRNA分子,在0.05~5 nmol·L-1的范围内, let 7a的浓度与从反应体系测得的FRET效率(I520/I423)成正比。同时以无PFP参加的检测方案作为对比实验,证明了PFP确实具有提高灵敏度的作用。另外,以四种同族miRNA分子及两种其他miRNA分子作为干扰物质对方法的特异性进行了考察,发现除了两种与目标分子序列高度相似的物质存在干扰外,其他物质几乎不产生信号。利用该方法对细胞总RNA提取液中let 7a的含量及其加标含量进行了检测,测量所得回收率基本令人满意。所建立的方案不需要荧光标记探针,有效降低了检测成本,简化了操作步骤,在与miRNA相关的疾病诊断领域具有一定的应用前景。     

A Highly Selective Fluorescent Probe for the Detection of Nitroreductase Based on a Naphthalimide Scaffold

The development of fluorescent probes for nitroreductase (NTR) has received intense attention because of its biological significance and wide application. In this work, a novel fluorescent probe for the detection of NTR in aqueous solution was designed and synthesized on a 1,8-naphthalimide scaffold. In the presence of NTR and nicotinamide adenine dinucleotide (NADH) under physiological conditions, the probe was converted into a 4-hydroxy-1,8-naphthalimide derivative and exhibited a sharp fluorescence enhancement at 550 nm, with a high selectivity for NTR over various analytes. The detection limit for NTR was determined to be 9.8 ng/ml by this probe. Due to its low signal background, this probe showed?>?70-fold fluorescence enhancement. Theoretical calculations revealed that the reason for the fluorescence quenching of this probe is the photoinduced electron transfer (PET) from both the nitrobenzene and morpholine groups to the naphthalimide fluorophore.

     

A Sensitive Fluorescent Sensor for Highly Sensitive Detection of Water in Organic Solvents Based on Substituted Imidazole

Journal of Fluorescence - A novel substituted imidazole derivative 1a with carboxyl and quinoline structure has been designed and synthesized. And our initial discovery is that this compound can...     

DMF保护的荧光银纳米簇的制备及其对Hg~(2+)浓度的检测

采用N,N-二甲基甲酰胺(DMF)作为还原剂和保护剂,在140℃下回流反应,简便合成了荧光银纳米簇(DMF-Ag NCs)。通过高分辨率透射电镜(HRTEM)、紫外-吸收光谱、荧光光谱对DMF-Ag NCs进行了表征。研究发现,Hg~(2+)会使DMF-Ag NCs聚集而猝灭荧光。基于此,建立了一种快速、灵敏检测Hg~(2+)的新方法。在最佳实验条件下,Hg~(2+)溶液浓度与DMF-Ag NCs荧光强度在5.0×10-9~1.5×10-7mol/L范围内呈良好的线性关系,检测限为3.0×10-9mol/L,线性相关系数为0.995 8。该方法可用于环境水样中Hg~(2+)的检测。     

A Novel Fluorescence Nanobiosensor based on Modified Graphene Quantum dots-HTAB for Early Detection of Fetal Sexuality with Cell Free Fetal DNA

Journal of Fluorescence - Recently, prenatal diagnosis with non-invasive insight is a progressive approach in clinical medicine to prevent the birth of infants with genetic abnormalities. Cell free...     

A Significant Fluorescent Aptamer Sensor Based on Carbon Dots and Graphene Oxide for Highly Selective Detection of Progesterone

In this paper, a fluorescent aptamer sensor was constructed based on the carbon dots (CDs) and graphene oxide (GO). This sensor combines the excellent fluorescence performance of CDs with the high specificity of aptamer, which can detect progesterone (P₄) with high sensitivity and selectivity. In the absence of P₄, the CDs-aptamer system and GO form a fluorescence resonance energy transfer process (FRET), which quenches the fluorescence of the CDs. When P₄ is added, the aptamer specifically binds to it, resulting the fluorescence of the CDs is recovered. At optimal conditions, the fluorescence intensity recovered by the CDs has a linear relationship with the concentration of P₄ in the range of 0.1–120 nM and the detection limit is 3.3?×?10^–11 M. Besides, the sensor has satisfactory detection results of P₄ in milk, indicating that constructed method has enormous potential for application in food safety.

     

基于亚甲基蓝的近红外荧光探针用于HOCl的特异性检测

次氯酸(HOCl)是一种由过氧化氢和氯离子在髓过氧化物酶(MPO)催化作用下产生的活性氧。由于其在机体抵抗病原体的免疫防御中起着至关重要的作用,因此对HOCl的识别和检测具有非常重要的意义。目前,检测HOCl的方法有电分析法、色谱法、化学发光法和荧光分析法,其中荧光检测法以其简单、快速、高选择性、高灵敏度和实时检测等突出优点引起了许多研究者的兴趣。本文以亚甲基蓝(Methylene blue,MB)为荧光母核,设计合成了一种近红外荧光探针MB-1用于HOCl的特异性检测。该探针可在体外特异性检测HOCl,响应之后,荧光会有显著的增强,同时伴有溶液颜色从无色到蓝色的明显变化。该探针对HOCl具有较高的灵敏度,其检测限为8.2 nmol/L。此外,该探针具有较好的抗干扰能力,为在生理水平上检测HOCl提供了可能。     

基于多特征和FCM的图像边缘检测方法

提出了一种新的基于多特征和FCM的边缘检测算法.该方法根据边缘点附近灰度分布特点构造了多个反映边缘特性的特征分量,并利用输入图像提取该组特征分量,组成一个反映图像边缘特征的数据集.用FCM聚类算法将该数据集分为两类,即边缘点数据和非边缘点数据,实现边缘检测.该方法无需确定阈值,对弱边缘检测较敏感,在特征的选取上充分考虑了边缘和噪声的本质区别,因而具有优异的抗噪性能.     

A Hybrid Coumarin-Semifluorescein-Based Fluorescent Probe for the Detection of Cysteine

A new type of turn-on fluorescent probe CF-AC for the detection of Cys was firstly reported. The probe exhibited an excellent response to Cys with high selectively and sensitivity. In the presence of Cys, two fluorescence emission peaks at 525 nm and 650 nm appeared accompanied by the fluorescence color change from blue to red. Morever, the probe had good biocompatibility and could be successfully used for fluorescence imaging of Cys in MCF-7 cells.     

基于荧光光谱法与深度信念网络的稻种发芽率检测方法研究

针对传统稻种发芽率检测效率低、精度差、专业化要求高等问题,通过荧光光谱法结合深度信念网络(DBN)建立稻种发芽率预测模型。首先,将连粳7号和武运粳均分别老化0~7 d后,以5 min为间隔在纯净水中分别浸泡5~30 min。然后用荧光光谱仪检测浸泡液的荧光光谱,光谱数据经中心化后用集合经验模态分解(EEMD)去噪,并通过主成分分析法提取441.5 nm的特征荧光波长。最后,利用偏最小二乘回归(PLSR),反向传播神经网络(BPNN),径向基函数神经网络(RBFNN)和深度信念网络(DBN)建立水稻种子发芽预测模型。比较后得出,DBN模型在少数据、弱信号情况下的预测精度最高,预测集相关系数Rp和均方根误差RMSEP最大可达0.979 2和0.101。同时,通过分析混合稻种荧光数据R_p的变化趋势,得到最佳浸泡时间为22.1 min,实际上,精确度超过0.95(R_p)需要5 min左右。研究结果表明,结合荧光光谱法和EEMD-DBN模型,非破坏性地预测水稻种子发芽率具有可行性和高准确性,并且适用于不同颜色和污染水平的水稻种子的检测。     

基于酶剪切量子点荧光放大技术的双元miRNA定量检测

将量子点荧光特性与双链特异性核酸酶的DNA剪切特性相结合,提出一种高灵敏度、高特异性的双元miRNA定量检测方案.首先,将量子点和四氧化三铁磁性纳米粒子分别与捕获DNA链接形成捕获探针,再与待测miRNA互补配对形成异源双链杂合结构,随后双链特异性核酸酶对杂合结构中的捕获DNA进行特异性剪切,实现量子点和待测miRNA从捕获探针分离,且分离的待测miRNA与捕获探针上未配对的DNA开始新一轮杂交和再剪切.经过上述循环过程,量子点从捕获探针大量释放,荧光信号不断增强,实现肿瘤标志物miRNA的高灵敏检测.实验结果表明,基于酶剪切量子点荧光放大技术,在1fmol/L至100pmol/L的浓度范围内,同时实现了肿瘤标志物miRNA-141及循环miRNA内参miRNA-1228的特异性定量检测,其检出限分别达到0.69fmol/L和0.21fmol/L.与实时荧光定量多聚核苷酸链式反应方法相比,该方案获得了相同的检测结果,且具有更高灵敏度.