SPDP Coupling to Amine Particles

Unlike the use of homobifunctional crosslinkers, heterobifunctional compounds usually don t have to be used in large excess with amine particles to prevent aggregation. This is due to the fact that only one of the ends of the crosslinker can react with the amines on the particles. 

Wash 10 mg of amine particles into 10 mM sodium phosphate, pH 7.2, using centrifugation. Resuspend the particles in 1 ml of the same buffer. 

Dissolve SPDP in dimethylformamide (DMF) at a concentration of 6.2 mg/ml (makes a 20 mM stock solution). Add 50 pi of the SPDP solution to the 1 ml particle suspension and mix to dissolve. Note The small quantity of DMF in a polymeric particle suspension should not affect particle stability, even if the polymer type is susceptible to swelling in pure DMF. Other particle types, such as metallic or silica based, usually are not affected by organic solvent addition, unless their surfaces are non-covalently coated with a dissolvable polymer. 

React for 30 minutes at room temperature with mixing. 

Wash particles with coupling buffer at least 3 times using centrifugation and resuspend in the same buffer using a sonic probe to disperse fully the particles. 

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