**1. Introduction**

602 Biomedical Science, Engineering and Technology

Vicent, M. J.; Dieudonne L.; Carbajo R. J. & Pineda-Lucena A. (2008). Polymer conjugates as

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therapeutics: future trends, challenges and opportunities. *Expert Opinion on Drug* 

Hydrophobic interaction chromatography (HIC) a powerful technique used for separation and purification of biomolecules. It was described for the first time by Shepard & Tiselius (1949), using the term "salting-out chromatography". Later, Shaltiel & Er-el (1973) introduced the term "hydrophobic chromatography". Finally, Hjerten (1973) described this technique as "hydrophobic interaction chromatography", based on the retention of proteins on weakly hydrophobic matrices in presence of salt. Owing of its high versatility and efficiency, HIC is widely used for the separation and purification of proteins in their native state (Porath et al., 1973), as well as for isolating protein complexes (Chaturvedi et al., 2000) and studying protein folding and unfolding (Bai et al., 1997).

HIC has been applied in separating homologous proteins (Fausnaugh & Regnier, 1986), receptors (Zhang et al., 2008), antibodies (Kostareva et al., 2008), recombinant proteins (Lienqueo et al., 2003) and nucleic acids (Savard & Schneider, 2007). HIC shows similar capacity to ion exchange chromatography (IEC) and a high level of resolution. Since it exploits a different principle than IEC and other separation techniques it can be used as an orthogonal method to achieve the purification of complex protein mixtures (Haimer et al., 2007). In this chapter, the theoretical principles underlying macromolecule retention in HIC are reviewed and discussed in sight of their application for predicting macromolecule behavior in HIC. Besides, novel applications of HIC are discussed regarding their suitability on Biomedical Engineering.
