An Os^II–Bisbipyridine–4‐Picolinic Acid Complex Mediates the Biocatalytic Growth of Au Nanoparticles: Optical Detection of Glucose and Acetylcholine Esterase Inhibition

Abstract

The complex Os(II)-bisbipyridine-4-picolinic acid, [Os(bpy)(2)PyCO(2)H](2+) (1), mediates the biocatalyzed growth of Au nanoparticles, Au NPs, and enables the spectroscopic assay of biocatalyzed transformations and enzyme inhibition by following the Au NP plasmon absorbance. In one system, [Os(bpy)(2)PyCO(2)H](2+) mediates the biocatalyzed oxidation of glucose and the growth of Au NPs in the presence of glucose oxidase, GOx, AuCl(4) (-), citrate and Au NP seeds. The mechanism of the Au NPs growth involves the oxidation of the [Os(bpy)(2)PyCO(2)H](2+) complex by AuCl(4) (-) to form [Os(bpy)(2)PyCO(2)H](3+) and Au(I). The [Os(bpy)(2)PyCO(2)H](3+) complex mediates the GOx biocatalyzed oxidation of glucose and the regeneration of the mediator 1. Citrate reduces Au(I) and enlarges the Au seeds by the catalytic deposition of gold on the Au NP seeds. In the second system, the enzyme acetylcholine esterase, AChE, is assayed by the catalytic growth of the Au NPs. The hydrolysis of acetylcholine (2) by AChE to choline is followed by the [Os(bpy)(2)PyCO(2)H](3+) mediated oxidation of choline to betaine and the concomitant growth of the Au NPs. The mediated growth of the Au NPs is inhibited by 1,5-bis(4-allyldimethylammonium-phenyl)pentane-3-one dibromide (3). A competitive inhibition process was demonstrated (K(M)=0.13 mM, K(I)=2.6 microM) by following the growth of the Au NPs.

Growing Metal Nanoparticles by Enzymes

“…This system was used to follow the inhibition of AChE through blocking the enlargement of the Au NPs. [27] …”

“…5A). [27] It was reported that in a mixture consisting of GOx, glucose, the electron-transfer mediator [Os(bpy) 2 -…”

Use of an Osmium Complex as a Universal Luminescent Probe for Enzymatic Reactions

“…[16] The study of the fluorescence properties of this complex showed a difference in the emission spectra of the reduced and oxidised forms. This phenomenon has allowed us to use this complex as a novel fluorescent probe for the detection of any biomolecule able to oxidise or reduce the Os complex.…”

Advanced Nanoparticles in Medical Biosensors

“…The electron transfer turnover rate was also exceptionally high (around 11 800 s − 1 ). Some other enzymes, such as alcohol dehydrogenase (NAD(P) + -dependent enzyme) [19,20] , acetylcholinesterase [21] , and tyrosinase [22] , have been successfully applied to the enzyme/nanoparticle hybrid system.…”