Colorimetric Detection (colorimetric + detection)

Distribution by Scientific Domains


Selected Abstracts


Specific Colorimetric Detection of Proteins Using Bidentate Aptamer-Conjugated Polydiacetylene (PDA) Liposomes

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
Yun Kyung Jung
Abstract The development of a bidentate aptamer-functionalized polydiacetylene (PDA) liposome sensor that is capable of specific colorimetric detection of proteins, directly in complex mixtures (e.g., serum), at sub-micromolar concentrations within 15 min, is reported. In comparison to sensors fabricated with a single aptamer reagent, the conjugation of bidentate aptamer pairs that recognize two distinct exosites of the target protein (thrombin) to the liposome results in significant enhancements of the sensitivity and the specificity. To elucidate the mechanism behind this enhancement, experimental evidence is presented that suggests that the liposomic aggregation triggered by specific, multi-site binding to the target protein is responsible for the improved colorimetric response. Since the colorimetric protein sensor does not require any power or instrumentation, it offers a promising approach towards molecular diagnostics at point-of-care (POC), especially in low-resource settings. [source]


Label-Free Colorimetric Detection of Lead Ions with a Nanomolar Detection Limit and Tunable Dynamic Range by using Gold Nanoparticles and DNAzyme,

ADVANCED MATERIALS, Issue 17 2008
Zidong Wang
In the presence of Pb2+, a cleaved enzyme,substrate complex releases ssDNA that adsorbs onto and stabilizes gold nanoparticles (AuNPs) against salt-induced aggregation. In the absence of Pb2+, the uncleaved complex can not stabilize the AuNPs, resulting in purple,blue AuNP aggregates (see figure). The sensor has a low detection limit of 3,nM, a high selectivity, and a tunable dynamic range. [source]


Colorimetric Detection of Glucose in Rat Brain Using Gold Nanoparticles,

ANGEWANDTE CHEMIE, Issue 28 2010
Ying Jiang
Ein Rattenhirn, das Goldes wert ist: Die einzigartigen optischen Eigenschaften von Goldnanopartikeln (AuNPs) und Reaktionskaskaden mit Glucose wurden genutzt, um Glucose im Rattenhirn auf einfache, aber effektive Weise direkt kolorimetrisch abzubilden. GOD=Glucoseoxidase. [source]


Silver-Ion-Mediated DNAzyme Switch for the Ultrasensitive and Selective Colorimetric Detection of Aqueous Ag+ and Cysteine

CHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2009
Tao Li
Abstract Two states, two applications! An Ag+ -mediated DNAzyme switch has been designed to detect Ag+ and cysteine with high sensitivity and selectivity. In the closed state, Ag+ turns on the switch through the formation of cytosine,Ag+,cytosine base pairs, whereas adding cysteine turns off the open switch because it competitively binds to Ag+. This feature endows the DNAzyme switch with two sensing applications. [source]


Specific Colorimetric Detection of Proteins Using Bidentate Aptamer-Conjugated Polydiacetylene (PDA) Liposomes

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
Yun Kyung Jung
Abstract The development of a bidentate aptamer-functionalized polydiacetylene (PDA) liposome sensor that is capable of specific colorimetric detection of proteins, directly in complex mixtures (e.g., serum), at sub-micromolar concentrations within 15 min, is reported. In comparison to sensors fabricated with a single aptamer reagent, the conjugation of bidentate aptamer pairs that recognize two distinct exosites of the target protein (thrombin) to the liposome results in significant enhancements of the sensitivity and the specificity. To elucidate the mechanism behind this enhancement, experimental evidence is presented that suggests that the liposomic aggregation triggered by specific, multi-site binding to the target protein is responsible for the improved colorimetric response. Since the colorimetric protein sensor does not require any power or instrumentation, it offers a promising approach towards molecular diagnostics at point-of-care (POC), especially in low-resource settings. [source]


Direct analysis of single leaf disks for chemopreventive glucosinolates

PHYTOCHEMICAL ANALYSIS, Issue 3 2002
Qiaomei Wang
Abstract Natural isothiocyanates, produced during plant tissue damage from methionine-derived glucosinolates, are potent inducers of mammalian phase 2 detoxification enzymes such as quinone reductase (QR). A greatly simplified bioassay for glucosinolates based on induction and colorimetric detection of QR activity in murine hepatoma cells is described. It is demonstrated that excised leaf disks of Arabidopsis thaliana (ecotype Columbia) can directly and reproducibly substitute for cell-free leaf extracts as inducers of murine QR, which reduces sample preparation to a minimum and maximizes throughput. A comparison of 1 and 3,mm diameter leaf disks indicated that QR inducer potency was proportional to disk circumference (extent of tissue damage) rather than to area. When compared to the QR inducer potency of the corresponding amount of extract, 1,mm leaf disks were equally effective, whereas 3,mm disks were 70% as potent. The QR inducer potency of leaf disks correlated positively with the content of methionine-derived glucosinolates, as shown by the analysis of wild-type plants and mutant lines with lower or higher glucosinolate content. Thus, the microtitre plate-based assay of single leaf disks provides a robust and inexpensive visual method for rapidly screening large numbers of plants in mapping populations or mutant collections and may be applicable to other glucosinolate-producing species. Copyright © 2002 John Wiley & Sons, Ltd. [source]


The combination of the antitumoural pyridyl cyanoguanidine CHS 828 and etoposide in vitro,from cytotoxic synergy to complete inhibition of apoptosis

BRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2002
P Martinsson
The present study was aimed at elucidating the apoptosis inhibitory properties of the cyanoguanidine CHS 828. CHS 828 exhibits impressive cytotoxic activity in vitro and in vivo. Apoptosis is not its main mode of cytotoxic effect, and we have previously proposed a dual mechanism, where CHS 828 inhibits its own cell death pathways. Etoposide on the other hand, is a well-established anticancer agent with documented effect in a number of malignancies, induces apoptosis through extensively studied caspase dependent pathways. Here we studied the combined effect of the two drugs in the human lymphoma cell line U-937 GTB. Cytotoxicity was evaluated as total viability measured by the fluorometric microculture cytotoxicity assay (FMCA). Caspase activity was assessed by colorimetric detection of specific cleavage products for caspases 3, 8 and 9, respectively. Morphology was evaluated in May-Grünwald/Giemsa stained preparations. Interaction analysis based on FMCA results of simple combination exposure revealed impressive synergistic effect on cell kill. Detailed investigations of the kinetics involved showed that short pre-exposure (0,12 h) to CHS 828 enhanced caspase activation by etoposide, while longer pre-exposure (18,48 h) inhibited both caspase activation and apoptotic morphology otherwise induced by etoposide. The present results support the theory that CHS 828 block specific cell death pathways. The synergistic results are promising for future combination trials in animals, however, different dosing schedules should be considered, in order to investigate whether the above findings translate into the in vivo setting. British Journal of Pharmacology (2002) 137, 568,573. doi:10.1038/sj.bjp.0704888 [source]


Mesoporous Hybrid Materials Containing Nanoscopic "Binding Pockets" for Colorimetric Anion Signaling in Water by using Displacement Assays

CHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2009
María Comes
Abstract Mesoporous solids functionalized with anion-binding groups have proved to be suitable anion hosts and have been used in selective colorimetric displacement assays. The material UVM-7, a mesoporous MCM41-type support characterized by the presence of nanometric mesoporous particle conglomerates, was selected as inorganic scaffolding. Reaction of the template-free UVM-7 solid with 3-aminopropyltriethoxysilane (1) yielded solid S1, from which the derivatives S2 and S3 were obtained by reaction with 2-methylthio-2-imidazoline hydroiodide (2) and butyl isocyanate (3), respectively. Solids S4 and S5 were prepared by reaction of the starting mesoporous UVM-7 scaffolding with N -methyl- N,-propyltrimethoxysilyl imidazolium chloride (4) and with 3-(trimethoxysilyl)propyl- N,N,N -trimethylammonium chloride (5), respectively. The solids synthesized contain mesoporous binding pockets that can interact with anions through electrostatic attractive forces (S1, S2, S4, S5) and hydrogen-bonding interactions (S1, S2, S3, S4). These functionalized solids were loaded with a dye (d) capable of interacting coordinatively with the anchored binding sites, in our case 5-carboxyfluorescein, to yield the hybrid materials S1d, S2d, S3d, S4d and S5d. These dye-containing solids are the signaling reporters. Their sensing ability towards a family of carboxylates, namely acetate, citrate, lactate, succinate, oxalate, tartrate, malate, mandelate, glutamate and certain nucleotides, has been studied in pure water at pH,7.5 (Hepes, 0.01,mol,dm,3). In the sensing protocol, a particular analyte may be bonded preferentially by the nanoscopic functionalized pocket, leading to delivery of the dye to the solution and resulting in colorimetric detection of the guest. The response to a given anion depends on the characteristics of the binding pockets and the specific interaction of the anion with the binding groups in the mesopores. We believe that the possibility of using a wide variety of mesoporous supports that can easily be functionalized with anion-binding sites, combined with suitable dyes as indicators, make this approach significant for opening new perspectives in the design of chromogenic assays for anion detection in pure water. [source]