## 2 Molecular Imprinting Process
### Optimization of MIPs Synthesis  
In the synthesis of MIPs, many parameters have to be assessed since they can influence morphology, properties and performance of the polymers. Even if many authors have tried to investigate and understand the role of different parameters in MIPs preparation, a rational comprehension of all of them is still quite difficult to achieve and represents a critical point in MIP field; however, some remarks in MIPs synthesis can be highlighted [8]. Today, the most common method used to obtain MIPs is the free radical polymerization. Generally, the synthesis procedure is performed under mild reaction conditions (e.g., temperature lower than 80 \({}^{\circ}\)C and atmospheric pressure) in bulk or in solution, and it is tolerant for a wide range of functional groups and template structures. The polymerization reaction is normally very rapid; it is started by an azo-initiator, commonly azo _N_-_N_-bis isobutyronitrile (AIBN) and by thermal or photochemical initiation. Data in literature demonstrate that photo-initiated polymerization at low temperature decreases the kinetic energy of the prepolymerization complex increasing its stability and allowing greater binding capacity and specificity than thermal initiated polymerization which requires temperatures higher than 40 \({}^{\circ}\)C [16, 44, 46]. Recently [PERSON] _et al_. [44] attempted to prepare MIPs for nitrofuranotin recognition by thermal initiation, but was unsuccessful. The author, according to the assumption of other papers [16, 46], used a photo initiation at low temperature (4 \({}^{\circ}\)C) with Irgacure 127 as initiator to synthesize MIPs by using a non-covalent approach. Thus, two different polymers were obtained with carboxyphenyl aminohydantoin as template and DMSO/acetonitrile (67/33) as the porogen and for these polymers interesting imprinting factors for carboxyphenyl aminohydantoin (3.38 and 3.53) and also for nitrofuranotin (2.27 and 2.49) were calculated. In the synthesis of MIPs, the choice of the chemical reagents is of primary importance in order to obtain efficient functional MIPs. A wide range of template molecules such as drugs, amino acids, carbohydrates, proteins, nucleotide bases, hormones, pesticides and co-enzymes have been successfully used [10, 11, 12, 13, 14, 15, 16, 17]. The choice of monomer is very important in order to create highly specific cavities designed for the template molecule. Typical functional monomers (Figure 4) are carboxylic acids (acrylic acid, methacrylic acid, vinylbenzoic acid), sulphonic acids (2-acrylamido-2-methylpropane sulphonic acid),heteroaromatic bases (vinylpyridine, vinylimidazole). In the non-covalent approach they are normally used in excess compared to the template to favor the formation of template-monomer assemblies. In fact, association between the monomer and the template is governed by an equilibrium, and the functional monomers normally have to be added in excess, relative to the number of moles of the template to favor the formation of the complex, with template:functional monomer ratios typically of 1:4. Consequently, this led to a number of different configurations of the template-functional monomer complex, which produced a heterogeneous binding site distribution in the final MIP, with a range of affinity constants. The extensive use of methacrylic acid (MAA) is due to its capability to act both as hydrogen bond and proton donor and as hydrogen bond acceptor. Moreover, more strong functional monomers were developed via metal coordination interactions to bind specific amino acid sequences [47]. New functional monomers, based on polymerizable amidines and ureas, have been developed for stoichiometrically imprinted polymeric receptor of \(\beta\)-lactam antibiotics, reducing non-specific adsorption [48]. The best monomers for synthesizing imprinted materials are selected considering strength and nature of template-monomer interactions as discussed in the previous paragraph. In imprinted polymers synthesis, the cross-linker also fulfils important functions.