Is it better to adsorb or covalently link proteins to the surface?
Although adsorbed preparations are capable of excellent stability covalent is very much to be preferred. With adsorbed preparations it is necessary to be very cautious about additives for adjusting the reactivity and preventing autoagglutination. For example, as shown in the Microparticle Optimization Manual, detergents such as Tween 20 can cause considerable desorption from the particle. Even salt can cause desorption during storage. With covalent coupling there is much greater freedom in the formualtion. In one case where I directly compared the sensitivity of an assay for a hapten I was able to get much better sensitivity of detection and better stability with covalently couple reagents than with adsorbed.
