Molecular imprinting polymers

Different classifications for the chiral CSPs have been described. They are based on the chemical structure of the chiral selectors and on the chiral recognition mechanism involved. In this chapter we will use a classification based mainly on the chemical structure of the selectors. The selectors are classified in three groups (i) CSPs with low-molecular-weight selectors, such as Pirkle type CSPs, ionic and ligand exchange CSPs, (ii) CSPs with macrocyclic selectors, such as CDs, crown-ethers and macrocyclic antibiotics, and (iii) CSPs with macromolecular selectors, such as polysaccharides, synthetic polymers, molecular imprinted polymers and proteins. These different types of CSPs, frequently used for the analysis of chiral pharmaceuticals, are discussed in more detail later. 

Application of MIP chemosensors imprinted with two different templates can also improve detectability. For instance, polycyclic aromatic hydrocarbons (PAHs) have been determined using polymers molecularly imprinted with two different PAH templates [155]. Compared with MIPs of a single-template imprint, the detection signal of the resonant frequency change was enhanced by a factor of five and LOD for pyrene was as low as 60 pg L 1. This two-template largely improved detectability can be attributed to easier accessibility of the recognition sites through different diffusion pathways. 

Very recently Mosbach et al. [156] have reported their latest results on p-elimination reactions catalysed by polymers molecularly imprinted with transition state analogues similar in structure to the haptens used in closely related work on catalytic antibodies [157]. There seems little doubt that this approach is likely to gather momentum, and run in parallel with the work on abzymes . 

Similar adsorption data have also been reported for the adsorption isotherms of many compounds in various systems. For example, the adsorption data of several jS-blockers, particularly those of propranolol acquired in a 1 to 7000 relative concentration range, on an immobilized cellulase. Cel 7A, fit very well to the bi-Langmuir model, as illustrated in Figure 3.13 [47,55]). The enantioselective site was identified as a pair of amino acid residues in the tunnel formed by the main chain of the protein. The parameters of the isotherm depend on the pH as illustrated in Figure 3.14. A bi-Langmuir model was also found to accoimt well for the separation of pairs of enantiomers on polymers molecularly imprinted with one of the enantiomers [56]. Note, however, that there are also many systems in which the adsorption isotherms of enantiomers are not accounted for by a bi-Langmuir model showing that enantioselectivity is often achieved by a complex... 

Many compounds have now been used as template molecules in molecular imprinting. Basically, imprinted polymers can be used directly as separation media. Since all separation applications cannot be described here, some studies recently reported are bsted in Table 7.1. In this chapter, only selected topics, including sensor applications, signaling polymers, molecularly imprinted sorbent assays, molecularly imprinted membranes, affinity-based solid phase extraction, in situ preparation of imprinted polymers, and molecularly imprinted catalysts are discussed. For the reader requiring information on other applications, there are many review articles dealing with these, Recent review articles and books are summarized in Table 7.1. For further development of molecular imprinting techniques, newly designed functional monomers would be desirable. Various functional monomers have been reported and many applications have been conducted. These are summarized in Table 7.2. 

Templated synthesis of polymers -molecularly imprinted materials for recognition and catalysis Wulff, G. Templated Org. Synth. (2000), 39-73. Editor Diederich, F. Stang, P. J. Publisher Wiley-VCH Verlag GmbH, Weinheim, Germany. 

Templated Synthesis of Polymers - Molecularly Imprinted Materials for Recognition and Catalysis... 

Molecularly Imprinted Polymers Molecular imprinting technique was recently used to prepare highly selective tailor-made synthetic affinity media used mainly in chromatographic resolution of racemates or artificial antibodies [158-161]. A complex between the template molecule and the functional monomer is first formed in solution by covalent or noncovalent interactions (Figure 6.12). 

Wulff, G. Templated synthesis of polymers— molecularly imprinted materials for recognition and catalysis. In Templated Organic Synthesis, Diederich, F., Stang, P.J., Eds. Wiley-VCH Weinheim, 1999, 39-73 pp. 

It is well known that a polymer is a big molecule or macromolecule formed from hundreds or thousands of molecules called monomers. The number of bonds that a monomer can form is called its functionality. In this chapter we focus on the properties, technology and applications of sensors doped or embedded in tetraethyl orthosilicate (TEOS) as a polymer, molecular imprinted polymer and polymethylmethacrylate (PMMA) for detecting pharmaceutical drugs. 

C. Alvarez-Lorenzo and A. Concheiro, Handbook of Molecularly Imprinted Polymers, Molecular Imprinting A Historical Perspective, C. Alvcuez-Lorenzo and A. Concheiro, eds., Smithers Rapra Publishing, 1 1-22,2013. 

K.C. Hua, L. Zhang, Z.-H. Zhang, Y. Guo and T.Y Guo, Surface hydrophihc modification with a sugar moiety for a uniform-sized polymer molecularly imprinted for phenobarbital in serum, Acta Biomater., 1 (8) 3086-3093,2011. 

SENSORS BASED ON FREE-STANDING MOLECULARLY IMPRINTED POLYMER MEMBRANES. COMPUTATIONAL MODELLING OF SYNTHETIC MIMICKS OF BIORECEPTORS... 

SENSORS WITH RESPONSE ON SOME XANTHENE DYES BASED ON MOLECULARLY IMPRINTED ELECTROSYNTHESIZED POLYMERS... 

The development of highly selective chemical sensors for complex matrixes of medical, environmental, and industrial interest has been the object of greate research efforts in the last years. Recently, the use of artificial materials - molecularly imprinted polymers (MIPs) - with high recognition properties has been proposed for designing biomimetic sensors, but only a few sensor applications of MIPs based on electrosynythesized conductive polymers (MIEPs) have been reported [1-3]. 

METAL-LOADED SORBENTS AND MOLECULARLY IMPRINTED POLYMERS IN SPE-LC... 

Recently, molecularly imprinted polymers (MIPs) have gained attention as new, selective sorbents for chromatography and SPE. The cavities in the polymer... 

The sorbents that are most frequently used in environmental analysis are Cig-silica based sorbents, polymeric sorbents (usually styrenedivinilbenzene) and graphitized carbon. In order to increase the selectivity of these sorbents, immunosorbents (35, 36) have been developed and used with good results, while recently, molecularly imprinted polymers have started be to used (35, 36). 

Fig. 5-5. Schematic representation of the preparation procedure of molecular imprinted polymers (MIP).

Molecularly imprinted polymers (MIPs) can be prepared according to a number of approaches that are different in the way the template is linked to the functional monomer and subsequently to the polymeric binding sites (Fig. 6-1). Thus, the template can be linked and subsequently recognized by virtually any combination of cleavable covalent bonds, metal ion co-ordination or noncovalent bonds. The first example of molecular imprinting of organic network polymers introduced by Wulff was based on a covalent attachment strategy i.e. covalent monomer-template, covalent polymer-template [12]. 

Some restrictions of this molecular imprinting technique are obvious. The template must be available in preparative amounts, it must be soluble in the monomer mixture, and it must be stable and unreactive under the conditions of the polymer-... 

Gel materials are utilized in a variety of technological appUcations and are currently investigated for advanced exploitations such as the formulation of intelligent gels and the synthesis of molecularly imprinted polymers. 

Toth E, Hehn L, Merbach AE (2002) Relaxivity of MRI Contrast Agents. 221 61-101 Tovar GEM, Krauter I, Gruber C (2003) Molecularly Imprinted Polymer Nanospheres as Fully Affinity Receptors. 227 125-144... 

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