Colloidal gold particles - (Feb/25/2011 )
Dear forum members,
does anyone know a kit to conjugate colloidal gold particles to proteins (more specifically, to antibodies)?
Because I will use these nanoparticles for microscopy, I need them to have a size of 5 nm.
The best would be any complete kit providing all the reagents and materials to do the conjugation.
Thank you a lot in anticipation!
If you make your own reagents it will cost much less then the $500 (kit). Although SPI provides some information there is no detailed instructions on their web site. If you obtain the article by Slot and Geuze you can increase the concentrations of the reactants to make a high concentration (ODU) particle suspension. the key is clean glassware, highly purified water, filtered buffers.
For adsorption (they refer to it as "conjugation") you must know the pI of your ab, adjust the pH of the colloid with high pH buffer such as carbonate or MES to just above the pI, and adsorp the protein. Determination of the correct pH and protein concentrations are referred to as 'pH isotherm and protein conc isotherm'. Upon pH adjustment and protein adsorption, 'challenge' the colloid with 1M NaCl or to be more rigorous 1M CaCl2. Suboptimum conditions result in the colloid flocculating (turning purple/black/ pelletting) optimal conditions the colloid will remain red-burgundy in color (depending upon the diameter particle you use). Scan the particles before and after coating and you will see a change in the lambd max.
mdfenko on Fri Feb 25 15:02:23 2011 said:
Thank you, mdfenko. I know these kits already but the minimun available size is 20nm. I need 5nm particles, unfortunately.