Antibody Conjugation
Antibody conjugated gold nanoparticle probes allow for the study and visualization of cellular and molecular processes in vitro and in vivo; a critical tool for both basic science researchers and clinicians.
Many investigators spend excessive time and energy synthesizing these conjugates themselves with varying degrees of success and inconsistent results. Most find that while performing conjugations on their own, they suffer from inconsistent antibody-to-particle attachment and non-reproducible cell labeling efficiency.
Solving the first problem of inconsistent antibody-to-particle attachment requires both:
(1) creation of a stable linkage between the particle and the antibody and
(2) Proper characterization of the antibody attachment.
To create a stable linkage, antibodies should be covalently linked to the surface. The scheme below shows several different methods of antibody conjugation.
The physical adsorption method is the least stable. It relies on the affinity of certain functional groups on proteins such as amines and thiols to be attracted via non-covalent interactions to the particle surface. In an in vivo environment, or even in cell media, antibodies that are physically adsorbed can be easily displaced.
Thus, the covalent conjugation method is the most widely used regime. It provides a stable linkage between the gold nanoparticle and the antibody and several different chemistries such as N-Hydroxysuccinimide (NHS) coupled with 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) can be employed. However, while this method produces a stable attachment, it still must be characterized.
Directional Conjugation for Better Efficiency
Characterization of antibody conjugated gold nanoparticles usually involves estimating the antibody to particle ratio by comparing fluorescence measurements of fluorophore-labeled antibody conjugated particles to known fluorophore-labeled antibody standards. The measurement itself can be complicated by the fluorophore quenching at the metal nanoparticle surface. Furthermore, researchers also must prepare the fluorophore-conjugated antibody and its standards.
NanoHybrids can employ a directional conjugation method which alleviates many of these problems.
To enable directional attachment, one end of a heterobifunctional crosslinker molecule is bound to the Fc region of the antibody. The other end of the linker binds directly to the gold nanoparticle surface, providing a directional linkage between the antibody and the particle. Using this method, a stable linkage between the particle and the antibody is realized while leaving the variable region (Fv), or antigen interacting site, sterically unhindered and available for binding.
The directional nature of the attachment makes characterization of the antibody-to-particle ratio more consistent and also enhances cell labeling efficiency and molecular targeting. Labeling efficiency can be increased by 7 to 10 fold using a directional versus non-directional attachment method. Using directionally conjugated gold nanoparticles can yield significant cost savings, enhance productivity, and accelerate scientific discovery.
Custom Antibody Conjugation Services
We can conjugate our gold nanoparticles to antibodies, proteins, or any other moeities of your choice. We also provide technical support for researchers who would like to purchase our gold nanoparticles and work on the conjugations. Contact us today for your custom conjugation requirements.
