Molecularly Imprinted Polymers (MIPs) in Biomedical Applications

Generations of scientists have been intrigued by the binding phenomena involved in interactions that occur between natural molecular species, and over the years, numerous approaches have been used to mimic these interactions. Complex formation between a host molecule and the guest involves recognition, which is the additive result of a number of binding forces. Within biological systems, these are usually dynamic and are the result of a mass of noncovalent interactions, which act collectively to form a very stable system. Molecular imprinting is a relatively new and rapidly evolving technique used to create synthetic receptors, having recognition properties comparable to the biological systems and it also possesses great potential in a number of applications in the life Sciences. Primarily, molecular imprinting aims to create artificial recognition cavities within synthetic polymers (Alvarez-Lorenzo & Concheiro, 2004; Ramström & Ansell, 1998; Mosbach & Ramström, 1996). It is a relatively simple concept, which involves the construction of sites of specific Biopolymers recognition, in synthetic polymers (Owens et al., 1999; Wulff, 1995; Caro et al., 2002; Joshi et al., 1998). The template of choice is entrapped in a pre-polymerization complex, consisting of functional monomers with good functionality, which chemically interact with the template. Polymerization in the presence of crosslinker serves to freeze these templatemonomer interactions and subsequent removal of the template results in the formation of a molecularly imprinted polymer matrix. Enormous interest has also been shown in imprinted materials as they mime biological receptors for the screening of new substances with potential pharmacological activity or to specifically detect drugs in biological fluids in screening assays for drugs of abuse. Such specificity is comparable with monoclonal antibodies used in immunoassay techniques (Pap et al., 2002; Chapuis et al., 2003; Caro et al., 2003; Vandevelde et al., 2007). Molecular imprinting is a well-developed tool in the analytical field, mainly for separating and quantifying very different substances, including drugs and bio-active molecules contained in relatively complex matrices. Moreover, the information generated about polymer synthesis procedures and the properties outlined for optimum performance in separation based technologies may be a good starting point to create imprinted polymers useful in biomedical applications such as drug delivery systems, polymeric traps for toxic metabolites, etc. (Cunliffe et al., 2005). The chapter will focus on the most representative applications of MIPs in the biomedical field.