Covalent Nanoparticle Conjugation for Lateral Flow Assays
Covalent binding of antibodies to the surface of gold nanoparticles results in robust and reliable conjugates. There are a number of advantages to covalent binding including:
Less antibody is needed to maximize sensitivity, which reduces the overall cost of an assay.
High stability can be obtained with covalent conjugates, which solves challenges associated with difficult sample matrices.
Conjugates are easily prepared without requiring salt or pH optimizations, which saves time when performing antibody screening experiments.
The antibody-to-particle ratio can be precisely controlled, which is important for adjusting the dynamic range in competitive assays and optimizing sensitivity with antibodies with varying binding kinetics.
The BioReady™ line of products from nanoComposix are optimized for use in conjugations and lateral flow diagnostic assays. Carboxyl functionalized nanoparticles are recommended for covalent binding. For this surface, EDC and sulfo-NHS reactive groups are used for amide bond formation, linking the carboxylic acid on the nanoparticle to primary amines in the lysine residues of the antibody or protein. A typical IgG antibody will have 80–100 lysine residues of which 30–40 will be accessible for EDC/NHS binding.
It is important to understand that each antibody is unique and may exhibit different performance when conjugated under different conditions compared to other proteins. There is no one-size-fits all conjugation method. In this module we outline a series of experiments designed to quickly and effectively produce robust and reliable covalent conjugates. If these instructions are carefully followed you will have a high chance of success. Building great conjugates is not easy, but once it works, they will perform again and again.
Covalent Coupling of Antibodies to Carboxyl Gold Nanoparticles Tutorial