Gold nanoparticles, 20nm, supplied in 0.1mM PBS, 95%, OD1, 524 nm absorption - FAQs

I am using Gold nanoparticles, 20 nm, supplied in 0.1 mM PBS, 95%, OD1, 524 nm absorption (Cat. No. J67318.xx). How do I ensure my gold nanoparticle conjugation reaction was successful?

We recommend using immunoblotting (dot-blot) to test a gold conjugate for the presence of the conjugated antibody (or antigen). Another alternative is to directly use the gold conjugate in the downstream application and compare its performance to a negative control gold conjugate.

I have the Gold nanoparticles, 20 nm, supplied in 0.1 mM PBS, 95%, OD1, 524 nm absorption (Cat. No. J67318.xx). Why does the gold nanoparticle solution turn violet when I add salt-containing buffer?

The normal color of the gold nanoparticles is red. Due to repulsive forces arising from the surface charge of gold nanoparticles, an energy barrier must be overcome for individual particles to interact. When no, or a small, amount of electrolytes such as NaCl are present, this energy barrier is too strong for interaction to occur between particles. However, once NaCl is added, this energy barrier is reduced and allows the gold nanoparticles to interact and aggregate. This aggregation causes a phenomenon called "surface-plasmon coupling" which changes the adsorption maximum of light to a higher wavelength, resulting in a change in color of the solution.

At what temperature should I store my Gold nanoparticles, 20 nm, supplied in 0.1 mM PBS, 95%, OD1, 524 nm absorption (Cat. No. J67318.xx)?

Gold nanoparticles should be stored at 4-25° Celsius. Do not store gold nanoparticles in the freezer since this cause irreversible aggregation.

My Gold nanoparticles, 20 nm, supplied in 0.1 mM PBS, 95%, OD1, 524 nm absorption (Cat. No. J67318.xx) settles out of solution upon storage. Is this normal?

Settling of gold nanoparticles on the bottom of the bottle is normal and is especially common for larger sized particles, which settle at a greater speed. Settling does not affect the performance of the particles. Prior to use, we recommend swirling the solution to properly disperse your gold nanoparticles.

How do I wash my Gold nanoparticles, 20 nm, supplied in 0.1 mM PBS, 95%, OD1, 524 nm absorption (Cat. No. J67318.xx)?

For most applications, our gold nanoparticles can be used without any additional washing steps. If you have a sensitive application that requires additional washing, we recommend centrifuging the gold nanoparticles. The easiest way to remove possible contaminants in the nanoparticle solution is by centrifugation. We recommend the following protocol:

1. Place 1 mL aliquot of colloidal gold in a 1.5 mL micro centrifuge tube.
2. Centrifuge the gold nanoparticles for 30 minutes at 10,000 RPM.
3. Remove the supernatant and re-suspend in an appropriate volume of ultra-pure water.
4. Vortex to re-disperse the particles.