Gold Nanoparticles

Our standard citrate stabilized spherical gold nanoparticles are prepared using a modified proprietary citrate reduction protocol, are optimized for high protein binding efficiency, and are ideal for use in applications such as conjugate development, lateral flow, dark field microscopy, Localized Surface Plasmon Resonance (LSPR)-based assays and Surfaced Enhanced Raman Spectroscopy (SERS).

The high shape uniformity of our colloidal gold nanoparticles minimizes the variability within your assay by e.g. allowing control over the available surface area while adsorbing proteins to the gold nanoparticles. This translates into higher performance and reduced costs for your specific assay.

Figure 1. Transmission electron microscopy (TEM) images (top) and UV-Vis spectrum (bottom) of Cytodiagnostics gold nanoparticles of different sizes.

Cytodiagnostics Standard Gold Nanoparticles are supplied in 0.1mM phosphate buffered saline (PBS) surface stabilized with citrate and are available with diameters from 5nm to 400nm.

These particles are also available pre-functionalized with a variety of functional groups for easy conjugation of bio-recognition molecules.

Applications

• Conjugate Development (see our gold nanoparticle conjugation kits)
• Immunostaining
• Lateral Flow Assays
• Biological Sensor Development (e.g. LSPR-based assays)
• Electron Microscopy
• Dark Field Microscopy
• Surface Enhanced Raman Spectroscopy (SERS)

Cytodiagnostics Reactant Free Gold Nanoparticles are supplied in 0.1mM phosphate buffered saline (PBS) and are extensively purified to be 99% free of residual reactants from manufacturing. These particles have the same high protein binding efficiency as our standard gold nanoparticle preparations for use in applications such as conjugate development, lateral flow and Surface Enhanced Raman Spectroscopy (SERS) with the added benefit of being reactant free for more sensitive applications such as cell work and nanotoxicology studies.

Applications

• Cell Work
• Conjugate Development
• Immunostaining
• Immunochromatography
• Lateral Flow Assays
• Biological Sensor Development (e.g. LSPR-based assays)
• Electron Microscopy
• Surface Enhanced Raman Spectroscopy (SERS)
• Nanotoxicology

Cytodiagnostics Surfactant Stabilized Gold Nanoparticles are supplied in a citrate buffer supplemented with a proprietary stabilizing solution for prolonged stability, higher salt tolerance and temperature stability.

Our surfactant stabilized preparations have been optimized for adsorption of thiolated ligands such as oligonucleotides and polyethylene glycols and are ideal for use applications requiring harsher conditions (i.e. higher salt concentrations) than those tolerated by standard gold nanoparticles.

Our extensively purified endotoxin free gold nanoparticles are ideal for sensitive applications requiring a minimal amount of contaminants, such as cellular toxicity studies, immunological studies, and aseptic assays. This product is well suited for conjugate development by passive adsorption of proteins and other ligands to the gold nanoparticle surface. The resulting conjugate can then be used in downstream applications.

All of our batches go through stringent quality control prior to shipment to our customers using dynamic light scattering to guarantee size and monodispersity and lot specifications are supplied with each product. The endotoxin levels of all batches are validated by the Limulus amebocyte lysate (LAL) test and do not exceed 0.5EU/mL.

Figure 1. Transmission electron microscopy (TEM) images (top) and UV-Vis spectrum (bottom) of Cytodiagnostics gold nanoparticles of different sizes.

Cytodiagnostics alkylthiol (dodecanethiol) stabilized gold nanoparticles are soluble in a wide range of organic solvents (see table below) and are available both dried and as a suspension in hexane.

Flow cytometry is a commonly used technique in many biological and clinical assays to evaluate cells and particles with sizes of 1μm and above. However, more advanced flow cytometers are now capable of analyzing small molecules down within the nanometer range. This allows for the study, and use of engineered nanoparticles, viruses and small bacteria not traditionally possible.

Cytodiagnostics Size Reference Gold Nanoparticles are specifically designed for the optimization of flow cytometer settings, performance and evaluation of particles or organisms in the 50nm – 400nm range.

Custom Conjugation Services – Nanoparticles

Cytodiagnostics provides an array of options for customers to do their own conjugations. Our gold and silver nanoparticles, and gold nanourchins are optimally designed for efficient passive adsorption of a multitude of proteins, antibodies, thiolated oligos, and more. For covalent conjugates, Cytodiagnostics also provides ready-to-use kits: Gold Conjugation Kits, Silver Conjugation Kits, NanoUrchin Conjugation Kits.

Let Us Do It For You!

Cytodiagnostics custom conjugation services help design and produce your very own custom conjugate. This includes most ligands ranging from proteins to enzymes to oligonucleotides, and this service extends to all the nanoparticles in our expansive catalog. You as a customer tell us the parameters and end-goal you need met, and our team of experts will work out the rest for you.

Cytodiagnostics gold nanoparticle protein conjugates are manufactured to the highest specifications resulting in conjugates with a low size coefficient of variation and excellent sensitivity.

Due to the versatility of gold nanoparticle conjugates, they can be used in a broad range of applications including Western blots, dot-blots, electron microscopy, light microscopy, in situ hybridizations and in lateral flow/vertical flow rapid tests.

Many of our secondary antibody conjugates are also available pre-adsorbed to minimize species cross-reactivity.

Can’t find the conjugate you need in the categories? Contact us and we would be happy to provide you with a custom solution.

Cytodiagnostics NHS-activated Gold Nanoparticle Conjugation Kits have been optimized for high efficiency one-step conjugation of proteins and other primary amine-containing ligands to gold nanoparticles.

The kits contains ready-to-use pre-made mixtures. No activation or manipulation of the gold nanoparticles is required prior to conjugation, which often results in poor performing conjugates. Simply mix your protein with the pre-activated NHS ester gold nanoparticles supplied in the kit to generate your conjugate.

The precisely engineered gold surface on our NHS ester-activated gold nanoparticles results in high conjugation efficiency and stable conjugates while minimizing non-specific binding in your assay.

For quality control of antibody and antigen conjugation our Conjugation QC Lateral Flow Dipstick Kit can be used.

Features & Benefits of NHS-Activated Gold Nanoparticles

• Results in covalently bound ligand and more stable conjugate.
• Fast and convenient one-step conjugation reaction with no pre-activation requirements.
• Spacer between the gold nanoparticle surface and conjugated ligand minimizes effects on the tertiary protein structure, which can lead to poor performing conjugates, a common problem seen in conjugates prepared by passive adsorption.
• Precisely engineering surface coating that reduces non-specific protein binding in biological assays.

Cytodiagnostics Maleimide-Activated Gold Nanoparticle Conjugation Kits have been optimized for high efficiency one-step conjugation of thiol-containing ligands such as oligonucleotides to gold nanoparticles.

The kits contains ready-to-use pre-made mixtures. No activation or manipulation of the gold nanoparticles is required prior to conjugation, which often results in poor performing conjugates. Simply mix your protein with the pre-activated maleimide gold nanoparticles supplied in the kit to generate your conjugate.

The precisely engineered gold surface coat on our maleimide-activated gold nanoparticles results in high conjugation efficiency and stable conjugates while minimizing non-specific binding in your assay.

Features & Benefits of Maleimide-Activated Gold Nanoparticles

• Results in covalently bound ligand and more stable conjugate.
• Fast and convenient one-step conjugation reaction with no pre-activation requirements.
• Spacer between the gold nanoparticle surface and conjugated ligand minimizes effects on the tertiary protein structure, which can lead to poor performing conjugates, a common problem seen in conjugates prepared by passive adsorption.
• Precisely engineered surface coating that reduces non-specific protein binding in biological assays.

Gold Conjugation Kits for Thiolated Oligonucleotides

Cytodiagnostics unique OligoREADY™ gold conjugation kits have been optimized for high efficiency one-step conjugation of thiolated oligonucleotides directly to the gold surface of particles with diameters up to 100nm.

The kit contains ready-to-use pre-made mixtures. No activation, manipulation, or time consuming “salt-aging” steps are require for conjugation. Simply mix your reduced thiol-modified oligonucleotide with the pre-activated gold nanoparticles supplied with the kit. Conjugation of the oligonucleotide is achieved by the formation of a strong and stable gold-thiol bond without any additional linkers.

Features & Benefits

• Allows conjugation of oligonucleotides to gold nanoparticles with sizes between 5nm-100nm.
• Fast and convenient one-step conjugation reaction with no pre-activation requirements or manipulation of the gold nanoparticles.
• Does not require time-consuming “salt-aging” procedures.
• Results in a thiol-oligo conjugated directly to the gold surface without any linkers

Cytodiagnostics unique AptamerREADY™ gold conjugation kits have been optimized for high efficiency one-step conjugation of thiolated aptamers directly to the gold surface of particles with diameters up to 100nm.

The kit contains ready-to-use pre-made mixtures. No activation, manipulation, or time consuming “salt-aging” steps are require for conjugation. Simply mix your reduced thiol-modified aptamer with the pre-activated gold nanoparticles supplied with the kit. Conjugation of the aptamer is achieved by the formation of a strong and stable gold-thiol bond without any additional linkers.

Features & Benefits

• Allows conjugation of aptamers to gold nanoparticles with sizes between 5nm-100nm.
• Fast and convenient one-step conjugation reaction with no pre-activation requirements or manipulation of the gold nanoparticles.
• Does not require time-consuming “salt-aging” procedures.
• Results in a thiol-aptamer conjugated directly to the gold surface without any linkers.

Working with oligonucleotides? Check out our OligoREADY™ gold nanoparticle kits for easy and improved conjugation!

Cytodiagnostics carboxyl functionalized gold nanoparticles have precisely engineered surface chemistry that enables coupling to various moieties that react with carboxylic acids. One of the most popular applications of this interaction is EDC/NHS coupling. The EDC activates the carboxylic acid so that it can react with NHS and acquire new functionality. The introduction of the NHS group then allows it to react with primary amines, which enables covalent coupling to proteins and antibodies with exposed amine-containing residues such as lysine. This permanent linkage has thus provided a gold nanoparticle label to the molecule in question and allows easier monitoring and localization within cells.

Cytodiagnostics carboxyl gold nanoparticles are available with diameters ranging from 5nm – 100nm and are also available with 2 different spacer lengths (3 kDa and 5 kDa). This provides the customer with the necessary tools fully optimize their experiment.

Cytodiagnostics biotin functionalized gold nanoparticles are available with diameters in the range of 5nm – 100nm.  These particles have a precisely engineered surface for optimal streptavidin binding while minimizing non-specific binding to other proteins present in your sample.

The gold nanoparticle label allows for convenient binding and detection of streptavidin in applications such as TEM, ELISA and Immuno dot-blots among others.

Figure 1. Cytodiagnostics Biotin gold nanoparticles bound to an avidin-coated surface substrate. Courtesy of Trevor Olsen, University of Alberta. Images taken at the NINT Electron Microscopy Facility.

Cytodiagnostics amine functionalized gold nanoparticles have precisely engineered surface chemistry that allows for simple and efficient binding to moieties that react with primary amines. An example of such a reaction would be a conjugation to a protein or antibody that has been tagged NHS, which would yield a covalent link between the gold nanoparticle surface and the protein. This permanent linkage allows for further downstream applications such as monitoring the distribution of the now-tagged molecule.

Cytodiagnostics amine gold nanoparticles are available with diameters ranging from 5nm – 100nm and are also available with 2 different spacer lengths (3 kDa and 5 kDa). This provides the customer with the necessary tools to fully optimize their experiment.

Cytodiagnostics Ni-NTA gold nanoparticles have precisely engineered surface chemistry consisting of a PEG spacer terminated with a nitrilotriacetic acid (NTA) group chelated to a Ni²⁺ ion. This specific functionality binds to His tags, which are a common modification added to the terminal end of proteins or antibodies, consisting of 6 sequential histidine residues. The interaction between Ni-NTA and His tags enables many applications when coupled to our gold nanoparticles: preparation of gold conjugates, protein purification and isolation, cell localization and uptake studies, use in assays, and more.

Cytodiagnostics Ni-NTA gold nanoparticles are available in 12 different sizes ranging from 5nm – 100nm, are more than 95% spherical and have a uniform size distribution (CV <12%). Products are provided as suspensions at 50 OD.

Cytodiagnostics azide functionalized gold nanoparticles are precisely engineered for covalent conjugation to any molecule tagged with an alkyne group. With the use of a copper(I) catalyst, the azide group on the gold and the alkyne-tagged molecule undergo a cycloaddition to form a stable and permanent linkage. The reaction between these 2 functional groups typically occurs rapidly, in high yield, and with no by-products, meaning that the customer will always have a stable conjugate and enough of it to use in subsequent downstream applications such as lateral flow assays and imaging. These reactions are also especially useful in applications involving oligonucleotides due to the higher prevalence of alkyne modifications.

Cytodiagnostics azide functionalized gold nanoparticles are available in 12 different sizes ranging from 5nm – 100nm, are more than 95% spherical and have a uniform size distribution (CV <12%). Products are provided as suspensions at 50 OD.

Cytodiagnostics alkyne functionalized gold nanoparticles are precisely engineered for covalent conjugation to any molecule tagged with an azide group. With the use of a copper(I) catalyst, the alkyne group on the gold and the azide-tagged molecule undergo a cycloaddition to form a stable and permanent linkage. The reaction between these 2 functional groups typically occurs rapidly, in high yield, and with no by-products, meaning that the customer will always have a stable conjugate and enough of it to use in subsequent downstream applications such as lateral flow assays and imaging. These reactions are also especially useful in applications involving oligonucleotides due to the higher prevalence of azide modifications.

Cytodiagnostics alkyne functionalized gold nanoparticles are available in 12 different sizes ranging from 5nm – 100nm, are more than 95% spherical and have a uniform size distribution (CV <12%). Products are provided as suspensions at 50 OD.

Cytodiagnostics methoxy gold nanoparticles have precisely engineered surface chemistry that renders them inert in most applications. This inert property allows these nanoparticles to be used as excellent control samples when in combination with one of our many other functionalized nanoparticles. In applications where the nanoparticles are not being used as controls, the surface chemistry enables them to be used in solutions with much higher salt concentrations relative to the corresponding standard or stabilized nanoparticles.
Cytodiagnostics methoxy gold nanoparticles are available with diameters ranging from 5nm – 100nm and are also available with 2 different spacer lengths (2 kDa and 5 kDa), allowing for better optimization.

Cytodiagnostics dibenzocyclooctyne (DBCO) functionalized gold nanoparticles are suitable for covalent conjugation of any azide-tagged molecule through click chemistry. The rigid structure of the DBCO allows for quick reactions under more moderate conditions, and eliminates the need for a copper catalyst. This chemistry confers higher stability in aqueous conditions and the lack of copper greatly increases its overall biocompatibility, enabling a multitude of biological applications.

Our DBCO functionalized gold nanoparticles are available in 9 different sizes ranging from 20 – 100nm, are more than 95% spherical and have uniform size distribution (CV <12%).

For custom sizes, formulations or bulk quantities please contact our customer service department, info@stratech.co.uk.