Molecular imprinting process

Molecular imprinting is a technique to synthesize highly cross-linked polymers capable of selective molecular recognition. In a molecular imprinting process, one needs  

Recently, a novel, highly sensitive, and selective electrochemical antibody-free cortisol sensor have been developed by using molecularly imprinted polymer (MIP) (Manickam et al., 2015). The general scheme for determination of analytes using MIP 

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Scheme 15.1 Schematic representation of the molecular imprinting process.

TABLE 15.1 Examples of Functional Monomers Used in Covalent Molecular Imprinting Process... 

Scheme 10.5 Synthesis of the UPy reversibly unfolding modular cross-linker. Scheme 15.1 Schematic representation of the molecular imprinting process.

It should be noted that the presence of cross-links results in the partial or complete loss of control over the size of the polymer molecules, even if the living character of the polymerization can sometimes be preserved. Incidently, one of the characteristics of MIPs is that they are cross-linked polymers. This cross-linking is necessary in order to maintain the conformation of the three-dimensional binding sites obtained through the molecular imprinting process, and thus the ability of the polymer to recognize specifically and selectively its target molecule. Nevertheless, even with cross-linked polymers, the use of CRP methods may be beneficial, as it can, up to a certain point, improve the structure of the polymer matrix. Indeed, all of the above CRP methods have been applied to MIPs. 

Figure 1 illustrates schematically the molecular imprinting process. The imprinting is performed using a template molecule (Fig. la), around which the functional... 

In practice, the molecular imprinting process involves the following steps. 

Fig. 1. Schematic diagram of the molecular imprinting process of specific cavities in a crosslinked polymer with the template (T) and functional monomers...

Fig. 3.1. A highly schematic representation of the molecular imprinting process. A monomer mixture with ehemical functionality complementary to that of the template is allowed to form solution adducts through the complementary interacting functionalities (reversible covalent or non-covalent interactions). Polymerisation in the presence of a cross-linking agent, followed by removal of the template, leads to the defining of recognition sites of complementary steric and functional topography to the template molecule.

It was quickly recognised that some elements involved in the molecular imprinting process are strongly analogous to the in vivo formation of antibod-... 

The aim of our work was to develop a fast, simple and selective CL imaging assay coupled with MIP for the chiral recognition of fluorescence labeled phenylalanine. The precipitation polymerization method was used for preparing MIP microspheres with uniform shape. Figure 2 shows the dansyl-L-phenylalanine molecular imprinting process. The average diameter of microspheres was about 0.7 pm. 

Molecular imprinting processes are composed of the following three steps ... 

Monomer-template conjugates are stable and stoichiometric, and thus the molecular imprinting processes (as well as the structure of guest-binding sites in the polymer) are relatively clear-cut. 

With regard to molecular imprinting, a significant hindrance to the development of anion-recognition MIPs has been the fact that anionic species are very often incompatible with apolar media. The molecular imprinting process involves the formation of a pre-polymerisation complex between the template molecule and functional monomers. This is typically based upon H-bonding... 

FIGURE 51.14 Schematic representation of a molecular imprinting process. (Reprinted from/nf. J. Pharm., 195(1-2), Allender, C.J., Richardson, C., Woodhouse, B., Heard, C.M., and Brain, K.R., Pharmaceutical applications for molecularly imprinted polymers, 39-43. Copyright 2000, with permission from Elsevier.)... 

Fig. 11 The molecular-imprinting process of cyclodextrin. (View this art in color, at www.dekker.com.)...

The "rational MIP design" involves better insights to the molecular imprinting process. An in-depth understanding of the molecular level events occurring in the MIPs is modeled mathematically. The earliest attempts to describe aspects of the molecular imprinting involved physical or mathematical formalism based on thermodynamic models [Pande et al., 1997 Sergeyeva et al., 1999 Nicholls et al., 1995]. 

Figure 7 Schematic of molecular imprint sorbent assay (MIA), (a) molecular imprinting process, (b) imprinted polymer containing trapped template-monomer complexes (c) extraction of template, (d) analyte and probe are added to the MIP, (e) analyte and probe compete for the available binding sites. In the conventional radiolabel MIA, the analyte is identical to the template, and the probe is the radiolabelled form of the analyte. In later, alternative MIA designs, template, analyte, and probe are not neeessarily identical.

Figure 1 Scheme of (A) molecular imprinting process and (B) recognition process. 

The efficiency of the molecular recognition in the molecular imprinting process is affected by many parameters. Some of the main characteristics of reagents that can be used for imprinting are listed in the following. 

Hgure 3 Schematic representation of molecular imprinting process T, template A, mixing and prearrangement B, polymerization C, template washing and Soxhiet extraction. (Reproduced with permission from Rao et al. (2004) Trends in Analytical Chemistry 23 24.)... 

Fig. 2.12 Schematic representation of the molecularly imprinting process the formation of reversible interactions between the template and polymerizable functionality may involve one or more of the following interactions (A) reversible covalent bond, (B) covalently attached polymerizable binding groups that are activated for nrai-covalent interaction by template cleavage, (C) electrostatic interactions, (D) hydrophobic or Van der Waals interactirais, (E) co-ordination with a metal center each kind of interaction occurs with complementary functional groups or structural elements of the template, (a-e), respectively. A subsequent polymerization in the presence of crosslinker(s) results in the formation of an insoluble matrix in which the template sites reside. Template is then removed from the polymCT through disruptirai of polymer-template interactions, and extraction from the matrix. (Reproduced fiom Ref. [97] with the permission of Wiley)...

Fig. 1. Schematic representation of Non-Covalent Molecular Imprinting Process. Adapted from Liu Z. et al., 2010.

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