The standard series of AURION gold nanoparticle conjugated immunoreagents is intended for the two and three step detection of antigens. Although these approaches cover the majority of applications there may occasionally exist a need for a direct label where the gold nanoparticles are coupled directly to the primary antibody or, more commonly, to a protein or peptide with specific binding properties. An example is found in working with specimens where substantial amounts of homologous immunoglobulins are present. A further example is found in the detection of receptors through labeled ligand molecules.
To fulfill these needs AURION offers a custom labeling service for antibodies, antibody fragments, proteins, and peptides with a variety of gold nanoparticle diameters, including ultra small gold particles. AURION selects the optimal conjugation strategy and designs and manufactures such custom conjugates in close co-operation and in agreement with the principal investigator.
Conjugation of high molecular weight molecules (e.g., antibodies) to conventional gold nanoparticles is best suited to the adsorption method. With this technique the immunoreactive molecule is directly linked to the gold nanoparticle surface. The combination of chemisorption via thiol groups, hydrophobic interaction and electrostatic binding of a single layer of proteins on the surface of the gold nanoparticles ensures optimum stability and activity of the conjugate.
In general this conjugation strategy can be used for macromolecules with a molecular weight > 30kDalton.
As an alternative, Aurion can prepare the requested gold nanoparticle conjugate using a covalent conjugation strategy. As a first step gold nanoparticles are stabilized with thiolated functional groups using chemisorprtion.
This conjugation strategy is in general favored for conjugating low molecular weight molecules.
More information on the different conjugation strategies can be found in Newsletter 6.
Starting material and quality control criteria
Our custom labeling service is based on the coupling of up to 1 mg of protein or ligand*.
The custom prepared product is initially quality controled by AURION according to our in-house standards for instance with respect to size distribution and clustering. In agreement with the principal investigator the binding substance’s specific quality control criteria are determined. These are tailored for each individual assignment. As a matter of course the custom conjugate is approved only when both sets of quality control criteria have been met.
A few examples
AURION successfully conjugated a number of polyclonal antibodies, mouse monoclonal antibodies, F(ab’)2 and F(ab) fragments, high and low density lipoproteins, as well as peptides such as an Angiotensin derivative (octapeptide), Interleukin II, Tumor Necrosis Factor and a number of peptide hormones. So far the efficiency of coupling for the above mentioned custom conjugates has been greater than 70% on all occasions, while efficiencies up to 90% are no exception.
No cure, no pay
The custom labeling service is on the basis of “no cure, no pay”, with the exception that a small intake fee applies to each actual laboratory attempt. We invite you to contact us if you request information which is more tailored to your specific research applications.
* Our custom labeling is based on the conjugation of 1 mg of antibody molecule (complete IgG). For other macro molecules, e.g., antibody fragments, a molar equivalent applies. For low molecular weight ligands please contact our Product Specialist. As a rule AURION will only accept pure substances as starting material, either lyophilized or dissolved in a medium of known chemical composition. Interfering substances must not be present. Current gold nanoparticle diameters available for custom conjugation: Ultra-small-2nm-6nm-10nm-15nm-20nm-25nm and 40nm.