Visual Detection of Copper(II) by Azide‐ and Alkyne‐Functionalized Gold Nanoparticles Using Click Chemistry

Gold nanoparticle-based colorimetric assay for selective detection of aluminium cation on living cellular surfaces

A colorimetric assay based on pentapeptide (CALNN) functionalized gold nanoparticles exhibits high sensitivity and selectivity for detection of aluminium cation (Al(3+)) both in aqueous solution and on living cellular surfaces under physiological condition.

Remarkable high-yielding chemical modification of gold nanoparticles using uncatalyzed click-type 1,3-dipolar cycloaddition chemistry and hyperbaric conditions

Azide-terminated alkyl thiolate monolayer-protected gold nanoparticles (1-C12MPN) with a core size of 1.8 ± 0.2 nm were prepared. 1-C12MPN was modified in high yields via an uncatalyzed 1,3-dipolar cycloaddition (click-type reaction) with a variety of terminal acyl–alkynes under hyperbaric conditions at 11 000 atm. The resulting 1,2,3-triazole modified MPNs (2-C12MPN) were characterized using 1H NMR spectroscopy and were verified by comparison of the spectra to those obtained for the products of the model reactions of 1-azidododecane with the same alkynes. TEM analysis showed that the high-pressure conditions did not affect the size of the gold core, suggesting that the only effect is to facilitate the chemical reaction on the particles.

Metal chelating systems synthesized using the copper(I) catalyzed azide-alkyne cycloaddition

The copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) is the premier example of a click reaction. The reaction is modular, reliable and easy to perform, providing easy access to molecular diversity. The majority of reported applications of the reaction employ the 1,2,3-triazole as a stable linkage to connect two chemical/biological components, while the potential for metal coordination of the heterocycle itself has received much less attention. In fact, 1,4-functionalized 1,2,3-triazoles are versatile ligands offering several donor sites for metal coordination, including N3, N2 and C5. In this article, we summarize the areas in which the CuAAC has been applied to the synthesis of novel triazole-containing ligands for transition metals.

Enhanced visual detection of pesticides using gold nanoparticles

The presence of parts per billion (ppb) levels of chlorpyrifos (O,O-Diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) and malathion (S-1,2-bis(ethoxycarbonyl) ethyl O,O-dimethyl phosphorodithioate), two common pesticides found in the surface waters of developing countries, have been visually detected using gold nanoparticles. Visual detection of the presence of pesticide is possible when the color change occurring by the adsorption of pesticides on gold nanoparticles is enhanced by sodium sulfate. The method presented here is simple and there is no need of sample preparation or preconcentration. The response occurs within seconds and the color change is very clear. The detection is possible if chlorpyrifos and malathion are present up to a concentration of 20 and 100 ppb, respectively. The method shows great potential for on-site pesticide monitoring. The method is also applicable as a qualitative technique for the performance evaluation of various household water filters, which claim pesticide removal.

Bioinspired colorimetric detection of calcium(II) ions in serum using calsequestrin-functionalized gold nanoparticles

Seeing is sensing: Calsequestrin (CSQ) functionalized gold nanoparticles undergo calcium-dependent CSQ polymerization, which results in a clear color change (see picture) together with precipitation. The sensing system is specific for Ca(2+) ions and the differences between normal and disease-associated abnormal (hypercalcemia) Ca(2+) ion levels in serum can be distinguished with the naked eye.

Combining nanosurface chemistry and microfluidics for molecular analysis and cell biology

Development of new tools catalyzes progress in biochemical sciences [G.M. Whitesides, E. Ostuni, S. Takayama, X.Y. Jiang, D.E. Ingber, Annual Review of Biomedical Engineering 3 (2001) 335]. Recent advances in micro-/nano-technology have resulted in an explosion of the number of new tools available for biochemical sciences. We have used surface chemistry, nano-structures and microfluidics to create a set of tools applicable for problems ranging from molecular to cellular analysis. These tools will promote the understanding of fundamental problems in cell biology, development and neurobiology, and become useful for real-world applications such as molecular diagnostics, food analysis and environmental monitoring.

Continuous colorimetric assay for acetylcholinesterase and inhibitor screening with gold nanoparticles

We report herein a new colorimetric assay method for acetylcholinesterase (AChE) activity and its inhibitor screening by making use of the following facts: (1) the aggregation of gold nanoparticles (Au-NPs) results in the red-shift of the plasmon absorption due to interparticle plasmon interactions and (2) AChE can catalyze the hydrolysis of acetylthiocholine into thiocholine which can induce the aggregation of Au-NPs. With this convenient method, the activity of AChE with a concentration as low as 0.6 mU/mL can be assayed. Moreover, this assay method is also useful for screening inhibitors of AChE. Given its simplicity and easy-operation, this method may extend to high-throughput screening of AChE inhibitors and relevant drug discovery.