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Stable oligomeric clusters of gold nanoparticles: preparation, size distribution, derivatization, and physical and biological properties.

Smithies O, Lawrence M, Testen A, Horne LP, Wilder J, Altenburg M, Bleasdale B, Maeda N, Koklic T - Langmuir (2014)

Bottom Line: The crude oligocluster preparations have narrow size distributions, and for most purposes do not require fractionation.The oligoclusters do not aggregate after ∼300-fold centrifugal-filter concentration, and at this high concentration are easily derivatized with a variety of thiol-containing reagents.Unlike conventional glutathione-capped nanoparticles of comparable gold content, large oligoclusters derivatized with glutathione do not aggregate at high concentrations in phosphate-buffered saline (PBS) or in the circulation when injected into mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, and ‡Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.

ABSTRACT
Reducing dilute aqueous HAuCl4 with NaSCN under alkaline conditions produces 2-3 nm diameter yellow nanoparticles without the addition of extraneous capping agents. We here describe two very simple methods for producing highly stable oligomeric grape-like clusters (oligoclusters) of these small nanoparticles. The oligoclusters have well-controlled diameters ranging from ∼5 to ∼30 nm, depending mainly on the number of subunits in the cluster. Our first ["delay-time"] method controls the size of the oligoclusters by varying from seconds to hours the delay time between making the HAuCl4 alkaline and adding the reducing agent, NaSCN. Our second ["add-on"] method controls size by using yellow nanoparticles as seeds onto which varying amounts of gold derived from "hydroxylated gold", Na(+)[Au(OH4-x)Clx](-), are added-on catalytically in the presence of NaSCN. Possible reaction mechanisms and a simple kinetic model fitting the data are discussed. The crude oligocluster preparations have narrow size distributions, and for most purposes do not require fractionation. The oligoclusters do not aggregate after ∼300-fold centrifugal-filter concentration, and at this high concentration are easily derivatized with a variety of thiol-containing reagents. This allows rare or expensive derivatizing reagents to be used economically. Unlike conventional glutathione-capped nanoparticles of comparable gold content, large oligoclusters derivatized with glutathione do not aggregate at high concentrations in phosphate-buffered saline (PBS) or in the circulation when injected into mice. Mice receiving them intravenously show no visible signs of distress. Their sizes can be made small enough to allow their excretion in the urine or large enough to prevent them from crossing capillary basement membranes. They are directly visible in electron micrographs without enhancement, and can model the biological fate of protein-like macromolecules with controlled sizes and charges. The ease of derivatizing the oligoclusters makes them potentially useful for presenting pharmacological agents to different tissues while controlling escape of the reagents from the circulation.

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Related in: MedlinePlus

TEM determinationof core sizes of oligoclusters and analysis oftheir distributions. (A and B) Representative TEM image of particlesprepared with 15 and 135 s delay times. (C and D) Histograms of numberof particles versus Feret diameters. The size distribution of the15 s oligoclusters is close to log-normal (−). The 135 s oligoclustersare distributed close to normally (− – −).
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fig2: TEM determinationof core sizes of oligoclusters and analysis oftheir distributions. (A and B) Representative TEM image of particlesprepared with 15 and 135 s delay times. (C and D) Histograms of numberof particles versus Feret diameters. The size distribution of the15 s oligoclusters is close to log-normal (−). The 135 s oligoclustersare distributed close to normally (− – −).

Mentions: The general shapes and sizedistributions of the oligoclusters madewith different delay times were determined by transmission electronmicroscopy (TEM). Figure 2 illustrates imagesobtained with GSH-derivatized preparations made with delay times of15 and 135 s. Figure 2A and B shows the mostobvious difference, that the shorter delay-time preparation consistslargely of monomers while the longer delay-time preparation consistsof clusters of subunits (oligoclusters). As illustrated in Figure 2C and D, the mean diameters of the clusters increasedabout 3-fold when the delay time increased 9-fold. Interestingly,the distribution of core sizes in the largely monomeric 15 s preparationis close to log-normal, while the distribution of sizes in the oligo-clustered135 s preparation is close to normal. This difference suggests thatthe reactions determining the sizes of the monomers are differentfrom those determining the number of monomers in a cluster.


Stable oligomeric clusters of gold nanoparticles: preparation, size distribution, derivatization, and physical and biological properties.

Smithies O, Lawrence M, Testen A, Horne LP, Wilder J, Altenburg M, Bleasdale B, Maeda N, Koklic T - Langmuir (2014)

TEM determinationof core sizes of oligoclusters and analysis oftheir distributions. (A and B) Representative TEM image of particlesprepared with 15 and 135 s delay times. (C and D) Histograms of numberof particles versus Feret diameters. The size distribution of the15 s oligoclusters is close to log-normal (−). The 135 s oligoclustersare distributed close to normally (− – −).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230385&req=5

fig2: TEM determinationof core sizes of oligoclusters and analysis oftheir distributions. (A and B) Representative TEM image of particlesprepared with 15 and 135 s delay times. (C and D) Histograms of numberof particles versus Feret diameters. The size distribution of the15 s oligoclusters is close to log-normal (−). The 135 s oligoclustersare distributed close to normally (− – −).
Mentions: The general shapes and sizedistributions of the oligoclusters madewith different delay times were determined by transmission electronmicroscopy (TEM). Figure 2 illustrates imagesobtained with GSH-derivatized preparations made with delay times of15 and 135 s. Figure 2A and B shows the mostobvious difference, that the shorter delay-time preparation consistslargely of monomers while the longer delay-time preparation consistsof clusters of subunits (oligoclusters). As illustrated in Figure 2C and D, the mean diameters of the clusters increasedabout 3-fold when the delay time increased 9-fold. Interestingly,the distribution of core sizes in the largely monomeric 15 s preparationis close to log-normal, while the distribution of sizes in the oligo-clustered135 s preparation is close to normal. This difference suggests thatthe reactions determining the sizes of the monomers are differentfrom those determining the number of monomers in a cluster.

Bottom Line: The crude oligocluster preparations have narrow size distributions, and for most purposes do not require fractionation.The oligoclusters do not aggregate after ∼300-fold centrifugal-filter concentration, and at this high concentration are easily derivatized with a variety of thiol-containing reagents.Unlike conventional glutathione-capped nanoparticles of comparable gold content, large oligoclusters derivatized with glutathione do not aggregate at high concentrations in phosphate-buffered saline (PBS) or in the circulation when injected into mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, and ‡Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.

ABSTRACT
Reducing dilute aqueous HAuCl4 with NaSCN under alkaline conditions produces 2-3 nm diameter yellow nanoparticles without the addition of extraneous capping agents. We here describe two very simple methods for producing highly stable oligomeric grape-like clusters (oligoclusters) of these small nanoparticles. The oligoclusters have well-controlled diameters ranging from ∼5 to ∼30 nm, depending mainly on the number of subunits in the cluster. Our first ["delay-time"] method controls the size of the oligoclusters by varying from seconds to hours the delay time between making the HAuCl4 alkaline and adding the reducing agent, NaSCN. Our second ["add-on"] method controls size by using yellow nanoparticles as seeds onto which varying amounts of gold derived from "hydroxylated gold", Na(+)[Au(OH4-x)Clx](-), are added-on catalytically in the presence of NaSCN. Possible reaction mechanisms and a simple kinetic model fitting the data are discussed. The crude oligocluster preparations have narrow size distributions, and for most purposes do not require fractionation. The oligoclusters do not aggregate after ∼300-fold centrifugal-filter concentration, and at this high concentration are easily derivatized with a variety of thiol-containing reagents. This allows rare or expensive derivatizing reagents to be used economically. Unlike conventional glutathione-capped nanoparticles of comparable gold content, large oligoclusters derivatized with glutathione do not aggregate at high concentrations in phosphate-buffered saline (PBS) or in the circulation when injected into mice. Mice receiving them intravenously show no visible signs of distress. Their sizes can be made small enough to allow their excretion in the urine or large enough to prevent them from crossing capillary basement membranes. They are directly visible in electron micrographs without enhancement, and can model the biological fate of protein-like macromolecules with controlled sizes and charges. The ease of derivatizing the oligoclusters makes them potentially useful for presenting pharmacological agents to different tissues while controlling escape of the reagents from the circulation.

Show MeSH
Related in: MedlinePlus