In recent years, increasing interest has focused on the preparation of magnetic latex particles for diagnostic applications. The pioneer work in this field was performed by Ugelstad (Prog. Polym. Sci. 1992) by reporting the preparation and the biomedical of polystyrene based magnetic microspheres. Then, several approaches have been investigated as evidenced from the numerous reported papers. The elaborated and manufactured magnetic latexes are not totally suitable in some specific biomedical applications such as nucleic acids detection and amplification or basically to be used in automated systems. The selected magnetic colloids should be compatible with the desired application. For instance, in the case of nucleic acid area, the cationic character of the particle surface is favorable for the adsorption but dramatic for enzymatic amplification process. The objective of this work is to present recent works on the elaboration, the colloidal characterization of magnetic colloids and there use for specific and non-specific capture, extraction and concentration of biomolecules. The magnetic colloids were prepared from well controlled oil in water submicronic magnetic emulsion.