Atrazine-imprinted polymers

Fig. 6-5 Scatchard plot for the binding of atrazine by the atrazine-imprinted polymer [1]...

Using the above-described automated system, several functional monomers have been screened for the development of molecularly imprinted polymers for the herbicides atrazine and ametryn [54]. According to the results, MAA appears to be more effective for developing the affinity in the atrazine-imprinted polymers. In contrast, 2-(trifluo-romethyl)acrylic acid is more effective for ametryn imprinting. 

Sergeyeva TA, Piletsky SA, Brovko AA, Slinchenko EA, Sergeeva LM, El skaya AV. Selective recognition of atrazine by molecularly imprinted polymer membranes. Development of conductometric sensor for herbicides detection. Anal Chim Acta 1999 392 105-111. 

The first work in this field was probably that of Piletsky et al. [84] that described a competitive FILA for the analysis of triazine using the fluorescent derivative 5-[(4,6-dichlorotriazin-2-yl)amino]fluorescein. The fluorescence of the supernatant after incubation was proportional to the triazine concentration and the assay was selective to triazine over atrazine and simazine. The same fluorescent triazine derivative was applied to competitive assays using atrazine-imprinted films [70]. To this end an oxidative polymerization was performed in the presence of the template, the monomer(s) 3-thiopheneboronic acid (TBA) or mixtures of 3-amino-phenylboronic acid (APBA) and TBA (10 1) in ethanol-water (1 1 v/v) where the template is more soluble. The polymers were grafted onto the surface of polystyrene microplates. The poly-TBA polymers yielded a detection limit of 8 pM atrazine whereas for the poly-TBA-APBA plates it was lowered to 0.7 pM after 5 h of incubation. However, a 10-20% decrease in the polymer affinity was observed after 2 months. 

Takeuchi et al. reported the preparation of an imprinted polymer for the conversion of the herbicide atrazine (100) in atraton (101), a less toxic compound, by conversion of an atrazine chloride into methoxy [59, 60]. After polymerisation and removal of the template, analysis of the imprinted polymer showed saturation kinetics, suggesting an enzyme-like behaviour of the polymer. 

Shoji, R., T. Takeuchi, and I. Kubo (2003). Atrazine sensor based on molecularly imprinted polymer-modified gold electrode. Anal. Chem., 75(18) 4882-4886. 

Siemann, M., L.I. Andersson, and K. Mosbach (1996). Selective recognition of the herbicide atrazine by noncovalent molecularly imprinted polymers. J. Agric. Food Chem., 44 141-145. 

Fig. 13.9. Binding of the original template species in atrazine-imprinted (A) and ametryn-imprinted (B) polymers.

Takeuchi, T. Fukuma, D. Matsui, J. Mukawa, T., Combinatorial molecular imprinting for formation of atrazine decomposing polymers, Chem. Lett. 2001, 1, 530-531... 

Another example of new sorbents is the molecular imprinted polymers (MIP) from the work of Siemann and co-workers (1996). They synthesized a methacrylic acid-ethylene glycol dimethacrylate copolymer with atrazine as an imprint molecule. Imprint synthesis entails polymerization around an imprint species with monomers that are selected for their ability to form specific and definable interactions with the imprint molecule. The atrazine is chemically removed from the polymer leaving holes or cavities. The cavities are formed in the polymer matrix whose size and shape are complementary to that of the imprint molecule (Siemann et al., 1996). These recognition sites enable the polymer to rebind the imprint species selectively from a mixture of closely related compounds, in many instances with binding affinities approaching those demonstrated by antigen-antibody systems. 

High selectivity can be obtained by imprinting polymers with neutral molecules.80 In this process, a cross-linked polymer is prepared in the presence of a template. Then the template is removed by solvent extraction. The extracted polymer is then used to pick up the template molecules from other sources. Among the examples in the literature are some that deal with atrazine (an herbicide), cholesterol, other sterols, dipeptides, TV-acetyltryptophane resolution (L-isomer favored by a factor of 6), adenine, and barbiturates.81 The polymerizations in the first two examples, are shown in (7.16) (The cross-linking comonomer with the cholesterol-containing monomer was ethylenebis-methacrylate. The cholesterol was cleaved from the polymer with sodium hydroxide in methanol.)... 

Svenson J, Ning Z, Fohrman U, Nicholls IA (2005) The role of functional monomer-template complexation on the performance of atrazine molecularly imprinted polymers. Anal Lett 38(l) 57-69... 

Molecularly imprinted sorbent assays represent one of the most typical applications of biomimetic use, where imprinted polymers are used as substitutes of natural antibodies in immunoassays. The assays usually involve competitive binding of an analyte with a certain quantity of labeled ligands, in which the labeled ligand unbound is proportional to the analyte added. Because dissociation constants of common imprinted polymers are around 10 6-10 9 M, competitive binding assays could easily be performed. In practice, many molecularly imprinted sorbent assays have been developed for biologically active compounds, including theophylline, diazepam [26], S-propranolol [27], morphine, Leu-enkephalin [28], cyclosporin A [29], yohimbine [30], methyl-a-glucoside [31], corticosteroid [32], atrazine [33, 34], and 2,4-D [35]. 

Atrazine MAA 2-sulfoethylaminomethacrylate EDMA CHCI3 Combinatorial molecular imprinting for atrazine-decomposing polymers [177]... 

Matsui, J., Dobihoff-Dier, O., and Takeuchi, T., Atrazine-selective polymer prepared by molecular imprinting technique, Chem. Lett., 24, 489-496, 1995. 

The imprinted polymers demonstrated not only equal but better specificity than the natural receptors and antibodies and also with excellent affinity (MIP for atrazine- Kd =1.5 nM) and stability (no changes in polymer performance were observed for a variety of polymers over 2 years of storage and use). 

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