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Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)-dipicolylamine complexes.

ABSTRACT: Gold nanoparticles covered with a mixture of ligands of which one type contains solubilizing triethylene glycol residues and the other peripheral zinc(II)-dipicolylamine (DPA) complexes allowed the optical detection of hydrogenphosphate, diphosphate, and triphosphate anions in water/methanol 1:2 (v/v). These anions caused the bright red solutions of the nanoparticles to change their color because of nanoparticle aggregation followed by precipitation, whereas halides or oxoanions such as sulfate, nitrate, or carbonate produced no effect. The sensitivity of phosphate sensing depended on the nature of the anion, with diphosphate and triphosphate inducing visual changes at significantly lower concentrations than hydrogenphosphate. In addition, the sensing sensitivity was also affected by the ratio of the ligands on the nanoparticle surface, decreasing as the number of immobilized zinc(II)-dipicolylamine groups increased. A nanoparticle containing a 9:1 ratio of the solubilizing and the anion-binding ligand showed a color change at diphosphate and triphosphate concentrations as low as 10 ?mol/L, for example, and precipitated at slightly higher concentrations. Hydrogenphosphate induced a nanoparticle precipitation only at a concentration of ca. 400 ?mol/L, at which the precipitates formed in the presence of diphosphates and triphosphates redissolved. A nanoparticle containing fewer binding sites was more sensitive, while increasing the relative number of zinc(II)-dipicolylamine complexes beyond 25% had a negative impact on the limit of detection and the optical response. Transmission electron microscopy provided evidence that the changes of the nanoparticle properties observed in the presence of the phosphates were due to a nanoparticle crosslinking, consistent with the preferred binding mode of zinc(II)-dipicolylamine complexes with phosphate anions which involves binding of the anion between two metal centers. This work thus provided information on how the behavior of mixed monolayer-protected gold nanoparticles is affected by multivalent interactions, at the same time introducing a method to assess whether certain biologically relevant anions are present in an aqueous solution within a specific concentration range.

SUBMITTER: Reinke L

PROVIDER: S-EPMC7607427 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)-dipicolylamine complexes.

Reinke Lena L Bartl Julia J Koch Marcus M Kubik Stefan S

Beilstein journal of organic chemistry 20201102

Gold nanoparticles covered with a mixture of ligands of which one type contains solubilizing triethylene glycol residues and the other peripheral zinc(II)-dipicolylamine (DPA) complexes allowed the optical detection of hydrogenphosphate, diphosphate, and triphosphate anions in water/methanol 1:2 (v/v). These anions caused the bright red solutions of the nanoparticles to change their color because of nanoparticle aggregation followed by precipitation, whereas halides or oxoanions such as sulfate, ...[more]

PMID: 33178359

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Project description:Monolayer-protected gold nanoparticles have great potential as novel building blocks for the design of new drugs and therapeutics based on the easy ability to multifunctionalize them for biological targeting and drug activity. In order to create nanoparticles that are biocompatible in vivo, polyethylene glycol functional groups have been added to many previous multifunctionalized particles to eliminate nonspecific binding. Recently, monolayer-protected gold nanoparticles with mercaptoglycine functionalities were shown to elicit deleterious effects on the kidney in vivo that were eliminated by incorporating a long-chain, mercapto-undecyl-tetraethylene glycol at very high loadings into a mixed monolayer. These long-chain PEGs induced an immune response to the particle presumably generating an anti-PEG antibody as seen in other long-chain PEG-ylated nanoparticles in vivo. In the present work, we explore the in vivo effects of high and low percent ratios of a shorter chain, mercapto-tetraethylene glycol within the monolayer using simple place-exchange reactions. The shorter chain PEG MPCs were expected to have better water solubility due to elimination of the alkyl chain, no toxicity, and long-term circulation in vivo. Shorter chain lengths at lower concentrations should not trigger the immune system to create an anti-PEG antibody. We found that a 10% molar exchange of this short-chain PEG within the monolayer met three of the desired goals: high water solubility, no toxicity, and no immune response as measured by white blood cell counts. However, none of the short-chain PEG mixed monolayer compositions enabled the nanoparticles to have a long circulation time within the blood as compared to mercapto-undecyl-ethylene glycol, which had a residence time of 4 weeks. We also compared the effects of a hydroxyl versus a carboxylic acid terminal functional group on the end of the PEG thiol on both clearance and immune response. The results indicate that short-chain-length PEGs, regardless of termini, increase clearance rates compared to the previous long-chain PEG studies, while carboxylated termini increase red blood cell counts at high loadings. Given these findings, short-chain, alcohol-terminated PEG, exchanged at 10%, was identified as a potential nanoparticle for further in vivo applications requiring short circulation lifetimes with desired features of no toxicity, no immune response, and high water solubility.

Dataset Information

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)-dipicolylamine complexes.

Publications

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)-dipicolylamine complexes.

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