免标记比色核酸适配体传感器同步快速检测孔雀石绿和无色孔雀石绿

研究以双特异性核酸适配体A3作为传感探针、纳米金（AuNPs）为指示剂、NaCl溶液为聚集诱导剂,构建了一种新型的免标记AuNPs比色生物传感器,可实现水产品中孔雀石绿（MG）和无色孔雀石绿（LMG）的同步、快速、可视化检测。该方法的检测原理是核酸适配体A3对MG和LMG有双特异性识别能力,可作为MG和LMG理想的识别受体。它可通过静电作用吸附到AuNPs表面,保护AuNPs并抑制高盐溶液诱导的聚集,AuNPs溶液颜色不变,即为红色;当加入靶标MG或LMG后,该核酸适配体能够与靶标特异性结合,并从AuNPs表面上解离,AuNPs失去保护作用而在高盐溶液诱导下发生聚集,溶液颜色由红变蓝。根据颜色变化,可通过肉眼定性或通过光谱仪定量分析MG和LMG的残留量。该方法首先将50 μL的核酸适配体A3（终浓度150 nmol/L）与150 μL的AuNPs（终浓度1.25 nmol/L）混合,室温孵育6 min。随后加入50 μL待测液,室温孵育30 min。最后加入50 μL NaCl（终浓度150 mmol/L）,4 min后观察溶液颜色变化,并分别测定MG和LMG在520 nm和650 nm下的吸光度值。结果表明,在最佳反应条件下,该方法能够特异性检测MG和LMG,而对磺胺嘧啶（SDZ）和硝基呋喃妥因（NFT）无交叉反应;当MG、LMG的浓度为0~17.5 μmol/L时,吸光度比值与靶标浓度呈现良好的线性关系,相关系数（R ² ）分别为0.9938和0.9715。MG和LMG的检出限分别为6.93 nmol/L和6.38 nmol/L,加标回收率分别为88.60%~93.30%和101.80%~107.00%,相对标准偏差（RSD）分别为2.27%~3.55%和2.62%~3.75%。该方法操作简单,快速和灵敏,可为水产品中MG和LMG的同步快速检测提供一种新方法。     

基于金纳米粒子探针比色法检测乙基谷硫磷

基于乙基谷硫磷在酸性条件下可以诱导金纳米粒子（AuNPs）发生聚集,建立了以AuNPs为探针、结合比色和分光光度法检测乙基谷硫磷的方法。通过改变氯金酸和还原剂柠檬酸钠的比例,制备了不同粒径的AuNPs。酸性溶液中乙基谷硫磷分子中-P=S键发生质子化,形成的-SH与Au形成S-Au键,使AuNPs发生聚集,溶液颜色由红色转变为蓝色。考察了乙酸-乙酸钠缓冲溶液的pH和浓度以及乙基谷硫磷与AuNPs的作用时间对AuNPs聚集程度的影响。在优化条件下,吸光度比值（A694 nm/A524 nm）与乙基谷硫磷浓度在0.392～0.603μmol/L范围内具有良好的线性关系,检出限为0.0782μmol/L。     

基于纳米金颗粒团聚反应的分光光度法测定牛奶中三聚氰胺的含量北大核心CSCD

用0.1g·L^(-1)氯金酸溶液100mL与10g·L^(-1)柠檬酸三钠溶液2mL反应制成红色纳米金颗粒(AuNPs)溶液,AuNPs粒径约为12nm,AuNPs溶液在波长518nm处有特征吸收峰。当三聚氰胺与AuNPs同处于一溶液中时,三聚氰胺的诱导作用使AuNPs团聚,其溶液的颜色由原来的红色变成蓝色(即在波长680nm附近出现新的吸收带)。三聚氰胺的检测范围为0.1～28.0μmol·L^(-1),测定下限(3σ)为0.1μmol·L^(-1)。据此,提出了测定牛奶中三聚氰胺含量的分光光度法。用标准加入法进行回收试验,回收率在99.0%～108%之间。     

金纳米粒子比色法检测卡那霉素的研究

运用金纳米粒子(AuNPs)比色法,构建了两种简单、快速、灵敏测定卡那霉素(KM)的新方法。方法一基于荷负电AuNPs与质子化的KM阳离子结合,AuNPs由酒红色变为蓝紫色,紫外吸收波长红移,吸光度降低。结果表明,吸光度比值(A620/A520)与KM的浓度在0.1~4.0μmol/L范围内存在良好的线性关系,其检出限(S/N=3)为33nmol/L。方法二基于核酸适配体AuNPs比色法测定KM。当不含KM时,核酸适配体与互补链形成稳定的双链DNA,高浓度NaCl溶液导致AuNPs团聚,颜色从酒红色变为蓝紫色。加入KM,适配体与KM结合,释放出单链DNA吸附于AuNPs表面使其保持稳定,颜色不发生变化。结果表明,吸光度比值((A0-A)/A)与KM的浓度在0.02~0.3μmol/L范围呈良好的线性,其检出限(S/N=3)为8nmol/L。建立的两种方法均可用于牛奶样品中KM的检测。方法一操作简单,但选择性较差;方法二检测KM的线性范围、检出限和选择性均较方法一更好。这两种方法可望用于其他抗生素的快速检测。     

金纳米粒子比色探针检测牛奶及鸡蛋中的三聚氰胺

三聚氰胺能诱导金纳米粒子(AuNPs)团聚,溶液颜色由酒红色变为紫色或蓝灰色.以AuNPs作为比色探针,建立了快速检测牛奶和鸡蛋中三聚氰胺的方法.实验优化得最佳反应条件为:AuNPs粒径13 min、pH=7、反应时间10 min和温度为室温.对样品中常见物质进行了干扰实验.样品经10％三氯乙酸和氯仿提取、离心分离后可...     

过渡金属配合物透视色原理

很多过渡金属配合物溶液都有特定的颜色,常见水溶液中金属离子的颜色一般就是水分子为配体的金属配合物的颜色,如绿色的[Ni（H2O）6]2+离子,粉色的[CO（H2O）6)2+离子等。这些配合物的颜色是怎样产生的呢?     

胆酸和柠檬酸根共同修饰的银纳米粒子对H_2PO_4~-的比色识别

本文合成胆酸和柠檬酸根共同修饰的银纳米粒子(CA+C-Ag NPs),通过银纳米粒表面的配体胆酸与H_2PO_4~-阴离子之间的络合作用,诱导CA+C-Ag NPs团聚,溶液由黄色变为酒红色,因而该银纳米探针可以选择性识别H_2PO_4~-。该银纳米粒探针检测H_2PO_4~-的线性范围为2×10~(-6)~1×10~(-5)mol·L~(-1),比色检测限为7×10~(-7)mol·L~(-1),具有较高的灵敏度。     

基于纳米金和脱氧核酶荧光探针检测铅离子

本文以"8-17"脱氧核酶为识别靶标的配体,设计了一种基于纳米金(AuNPs)和脱氧核酶的荧光信号放大法检测Pb2+的探针。"8-17"脱氧核酶由一条底物链(17DS)和一条酶链(17E)组成。在底物链的一端修饰荧光基团6-羧基荧光素(FAM),而酶链通过巯基修饰到AuNPs表面。当底物链与酶链相混合时,酶链与底物链杂交,AuNPs与FAM靠近,导致FAM的荧光被AuNPs猝灭。当向该体系加入Pb2+时,"8-17"脱氧核酶被Pb2+激活,酶链将底物链剪切为两段,破坏了杂交的刚性结构,从而使得FAM的荧光恢复。基于此原理,构建了一种定量检测Pb2+的高灵敏传感器,该传感器对Pb2+的检测限达0.6nmol/L。     

基于C3v对称性的杯[6]芳烃对Hg2+的荧光选择性识别

合成了一系列具有C3v对称性、下缘分别利用Se、Te和S杂原子连接蒽环发光基团的杯[6]芳烃衍生物1-3.通过紫外-可见光谱和荧光光谱研究了它们对各种碱金属离子和过渡态金属离子的化学传感识别行为. 结果表明,含有Se杂原子的主体1在CH2Cl2溶液中对Hg2+表现出良好的选择性. 并且,通过肉眼可以直接观察到溶液颜色由无色变为黄色.通过荧光光谱的连续滴定实验,主体1-Hg2+体系的稳定常数可达（1.12 ? 0.08) ? 105 M-1. 因此,化合物1有望成为一种用于检测Hg2+的新型化学传感器.     

纳米金颗粒增强信号的电化学生物传感器用于谷胱甘肽和半胱氨酸的检测

构建了一种高灵敏检测谷胱甘肽(GSH)和半胱氨酸(Cys)的新型电化学生物传感器. 先将富含T碱基的DNA1和DNA2探针分别修饰在金电极和纳米金颗粒(AuNPs)上, 再加入Hg²⁺, 通过形成T-Hg²⁺-T结构使AuNPs结合到金电极表面. 当加入GSH(或Cys)后, GSH(或Cys)可以竞争结合T-Hg²⁺-T结构中的Hg²⁺, 使AuNPs离开电极表面. 由于AuNPs上修饰的DNA探针能够静电吸附大量电活性物质六氨合钌(RuHex), 因此该过程可引起计时电量信号的显著变化, 据此实现了GSH(或Cys)的高灵敏检测. 该传感器的检出限达10 pmol/L, 比荧光法或比色法降低了2~3个数量级. 实验结果表明, 该传感器具有较好的选择性.     

Coordination of mercury(II) to gold nanoparticle associated nitrotriazole towards sensitive colorimetric detection of mercuric ion with a tunable dynamic range

A simple colorimetric assay with high sensitivity, excellent selectivity and a tunable dynamic range is reported for detecting trace amounts of mercuric ion in aqueous solution based on the coordination of Hg(2+) to the gold nanoparticle (AuNP)-associated 3-nitro-1H-1,2,4-triazole (NTA). The NTA can stabilize the AuNPs against tris-induced aggregation through capping the AuNPs. In the presence of Hg(2+), the NTA is released from the AuNP surface via the formation of a NTA-Hg(2+) coordination complex, leading to the aggregation of AuNPs in tris. This detection strategy is unique in terms of high sensitivity and excellent selectivity, a tunable dynamic range, and simplicity of probe preparation. Low detection limits of 7 nM (1.4 ppb) and 50 nM (10 ppb) can be achieved by spectrophotometer and by direct visualization, respectively, under the optimized conditions. No noticeable colour changes are observed towards other metal ions (Ag(+), Zn(2+), Ni(2+), Cr(3+), Mg(2+), Cu(2+), Co(2+), Cd(2+), Pb(2+), Fe(2+)) at concentrations up to 100 μM without the need of any other masking agents. In addition, the dynamic range of the assay can be easily tuned by adjusting the amount of NTA in the NTA-AuNP probes. More importantly, the NTA-AuNP probes can be simply prepared by mixing NTA with as-synthesized citrate-capped AuNPs. This not only avoids complicated surface modifications and tedious separation processes, but also is cost-effective.     

Colorimetric assay for parallel detection of Cd2+, Ni2+ and Co2+ using peptide-modified gold nanoparticles

A colorimetric assay has been developed for parallel detection of Cd(2+), Ni(2+) and Co(2+) utilizing peptide-modified gold nanoparticles (P-AuNPs) as a sensing element based on its unique surface plasmon resonance properties. The functional peptide ligand, CALNNDHHHHHH, was self-assembled on gold nanoparticles (AuNPs) to produce P-AuNPs probe. The P-AuNPs probe could be used to simultaneously detect and showed different responses to the three ions Cd(2+), Ni(2+) and Co(2+) in an aqueous solution based on the aggregation-induced color change of AuNPs. The method showed good selectivity for Cd(2+), Ni(2+) and Co(2+) over other metal ions, and detection limit as low as 0.05 μM Cd(2+), 0.3 μM Ni(2+) or 2 μM Co(2+). To simultaneously (or parallel) detect the three metal ions coexisting in a sample, EDTA and imidazole were applied to mask Co(2+) and Ni(2+) for detecting Cd(2+), glutathione and EDTA were applied to mask Cd(2+) and Co(2+) for detecting Ni(2+), and glutathione and imidazole were applied to mask Cd(2+) and Ni(2+) for detecting Co(2+). Finally, the simple and cost-effective probe could be successfully applied for simultaneously detecting Cd(2+), Ni(2+), and Co(2+) in river water. Because this novel P-AgNPs-based probe design offers many advantages, including simplicity of preparation and manipulation compared with other methods that employ specific strategies, the sensing system shows potential application in the developing region for monitoring water quality.     

Gold nanoparticle-enabled real-time ligation chain reaction for ultrasensitive detection of DNA

A simple and ultrasensitive colorimetric DNA assay based on the detection of the product of a ligation chain reaction (LCR) and the use of gold nanoparticles (AuNPs) as signal generators has been developed. During LCR, the AuNPs were ligated together, resulting in a distinct color change in real time after a sufficient number of thermal cycles. The cumulative nature of the protocol produced a detection limit of 20 aM with a selectivity factor of 10(3).     

Colorimetric kinetic determination of potassium ions based on the use of a specific aptamer and catalytically active gold nanoparticles

We describe a simple, highly sensitive, and selective colorimetric kinetic assay for the determination of potassium(I) by exploiting the specific recognition capability of an appropriate aptamer and catalytic signal amplification by gold nanoparticles (AuNPs). Amplification is based on the reduction of 4-nitrophenol by borohydride which is catalyzed by AuNPs. This leads to a color change of the solution from yellow to colorless, and the color change can be recognized with bare eyes or via photometry. The K(I)-selective aptamer is placed on the AuNPs and forms a tightly bound G-quadruplex with K(I) which partially masks the surface of the AuNPs and prevents 4-nitrophenol to be reduced at the catalytically active surface of the AuNPs. Hence, the rate of decoloration is retarded. The assay displays high selectivity for K(I) over other cations, has a linear response in the 0.1 nM to 10 μM concentration range, and a detection limit as low as 0.06 nM. In addition, these findings pave the way to novel analytical methods based on the use of gold nanoparticle-catalyzed chemical reactions.

A simple, highly sensitive, and selective colorimetric kinetic assay for the determination of potassium(I) was represented.

     

Aptamer-wrapped gold nanoparticles for the colorimetric detection of omethoate

Organophosphorous pesticide(OP) contamination has serious adverse effects on human health and the environment. Due to the toxicity of OPs and the threat presented by their accidental or intentional release in populated areas, the determination and monitoring of these OPs in food products and environment is of great importance. OPs are present in very small quantities and therefore, methods for their detection need to be highly sensitive and selective. Here, we aimed to develop a simple and selective aptamer-based colorimetric assay for the detection of omethoate, which is one of the commonly used OPs. The principle of the assay is that single-stranded DNA(ss DNA)-wrapped gold nanoparticles(Au NPs) are resistant to salt-induced aggregation. By employing an "artificial antibody" organophosphorous pesticide-binding aptamer(OBA) as the recognition element, aptamer-wrapped Au NPs(Au-apta) show high selectivity towards omethoate, resulting in the disconnection of aptamers from Au NPs and the aggregation of Au NPs. As there is a significant color change from the interparticle plasmon coupling during the aggregation of Au NPs, the established assay showed good linearity between 0.1 and 10 μmol/L, with a low detection limit of 0.1 μmol/L. Other OPs such as profenofos, phorate, and isocarbophos would not interfere with the detection of omethoate despite having similar structures. Thus, the colorimetric method shows potential for use in the detection of omethoate in real soil samples.     

Visual chiral recognition of tryptophan enantiomers using unmodified gold nanoparticles as colorimetric probes

A simple protocol to distinguish enantiomers is extremely intriguing and useful. In this study, we propose a low-cost, facile, sensitive method for visual chiral recognition of enantimers. It is based on the inherent chirality of gold nanoparticles (AuNPs), and the unmodified AuNPs are used as chiral selector for d- and l-Tryptophan (Trp). In the presence of d-Trp, an appreciable red-to-blue color change of AuNPs solution can be observed, whereas no color change is found in the presence of l-Trp. The method can be used to detect d-Trp in the range of 0.2–10 μM, and the limit of detection is 0.1 μM. The chiral assay described in this work is easily readout with the naked eye or using a UV-vis spectrometer. Furthermore, the AuNPs can selectively adsorb d-Trp, and simple centrifugation can allow the precipitation of d-Trp with AuNPs and leave a net excess of the other enantiomer in solution, thus resulting in enantioseparation. In this method, AuNPs do not need any labeling or modifying with chiral molecules. The method is more attractive because of its high sensitivity, low cost, ready availability and simple manipulation.     

A novel electrochemiluminescence aptasensor for protein based on a sensitive N-(aminobutyl)-N-ethylisoluminol-functionalized gold nanoprobe

A novel electrochemiluminescence (ECL) aptasensor for platelet-derived growth factor B chain (PDGF-BB) assay was developed by assembling N-(aminobutyl)-N-ethylisoluminol functionalized gold nanoparticles (ABEI-AuNPs) with aptamers as nanoprobes. In the protocol, the biotinylated aptamer capture probes were first immobilized on a streptavidin coated gold nanoparticle (AuNPs) modified electrode, afterwards, the target PDGF-BB and the ABEI-AuNPs tagged aptamer signal probe were successively attached to the modified electrode by virtue of the dimer structure of PDGF-BB to fabricate a "sandwich" conjugate modified electrode, i.e. an aptasensor. ECL measurement was carried out with a double-step potential in carbonate buffer solution containing H(2)O(2). The aptasensor showed high sensitivity and selectivity toward PDGF-BB and specificity toward PDGF-BB aptamer. The detection limit was as low as 2.7 × 10(-14) M. In this work, the ABEI-AuNPs synthesized by a simple seed growth method have been successfully used as aptamer labels, which greatly amplified the ECL signal by binding numbers of ABEI molecules on the surface of AuNPs. The ABEI-AuNPs signal amplification is superior to other reported signal amplification strategies based on aptamer-related polymerase chain reaction or functionalized nanoparticles in simplicity, stability, labeling property and practical applicability. And the ABEI-AuNPs based nanoprobe is more sensitive than the luminol functionalized AuNPs based nanoprobe. Moreover, such an ultra-sensitive and low-cost assay can be accomplished with a simple and fast procedure by using a simple ECL instrumentation. The aptasensor was also applied for the detection of PDGF-BB in human serum samples, showing great application potential. Given these advantages, the ECL aptasensor is well suited for the direct, sensitive and rapid detection of protein in complex clinical samples.     

Iminodiacetic acid-functionalized gold nanoparticles for optical sensing of myoglobin via Cu2+ coordination

A novel gold nanoparticle (AuNP)-based optical sensing system has been developed for the detection of myoglobin (Mb), which is of significant importance for early disease diagnosis. Two thiol molecules containing an iminodiacetic acid moiety (IDA) were synthesized. This detection is based on the Mb-induced aggregation of IDA-functionalized AuNPs resulting from the structures of Mb sandwiched between the functionalized AuNPs via Cu(2+) bridges in the coordination interactions of IDA-Cu(2+)-histidine residues available on the Mb surface, which was confirmed by UV-vis spectroscopy, transmission electron microscopy, dynamic light scattering, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The induction aggregation resulted in a red shift in plasmon resonance band of the AuNPs concomitant with a change in solution color from red to purple. The qualitative and quantitative detections of Mb can be achieved by colorimetric observations and UV-vis spectral measurements, respectively. The selectivity of protein assay with the functionalized AuNPs was further investigated, and it is found that the optical sensing of histidine-rich proteins is closely related to number and distribution of surface histidine residues as well as size of proteins.     

A simple visual method for DNA detection based on the formation of gold nanoparticles

A simple visual method for DNA detection during the formation of gold nanoparticles (AuNPs) was developed based on different electrostatic properties of single strand DNA (ssDNA) and double strand DNA (dsDNA). Since the ssDNA is easy to bind to AuNPs due to its exposed bases which could prevent salt-induced aggregation of AuNPs. The dsDNA always present negative charge because its negatively charged phosphate backbone is exposed. In this case, the dsDNA could disturb the adsorption between dsDNA and AuNPs and result in non-aggregation of AuNPs. After hybridization, chloroauric acid and ascorbic acid were added to the mixture solution, and the solution changed to red immediately and turned to purple in 10 min in the present of target DNA. TEM results confirmed that the change of color stemed from aggregation of AuNPs. In order to obtain accurate results by naked eye, the DNA detection assay should be conducted under pH 7.0.     

A simple visual method for DNA detection based on the formation of gold nanoparticles

A simple visual method for DNA detection during the formation of gold nanoparticles (AuNPs) was developed based on different electrostatic properties of single strand DNA (ssDNA) and double strand DNA (dsDNA). It could identify target DNA in 10 min.