What is the advantage of gold nanoparticle conjugation via adsorption?
This is an easy and straight forward method for the conjugation of high molecular weight macromolecules. The flocculation test that tests the effect of a high salt concentration on the stability of the complex makes it easy to check if adsorption to the gold nanoparticle surface is successful or not.
Can you give me more information on gold nanoparticle conjugation strategy?
First check if conjugation via adsorption is feasible. If yes, check bio activity e.g., via a dot spot test. Biomolecules that are too small to be conjugated via the classic adsorption method can be covalently linked to functionalized gold nanoparticles as an alternative. A prerequisite for successful conjugation to Carboxyl-functionalized gold nanoparticles is the presence of primary amine(s) in the target molecule. As a rule of thumb conjugation via classic adsorption to conventional gold nanoparticles is possible with macromolecules having a MW > 40 kDa.
What is the conjugation principle behind covalent conjugation using carboxyl-functionalized gold nanoparticles?
The conjugation relies on the well known and proven EDC/sulfo-NHS chemistry. EDC/sulfo-NHS activation at pH 5 results in an amine reactive ester, immediately followed by binding to free amine on the target molecule.