Synthesis, characterization and kinetics of catalytically active molecularly imprinted polymers for the selective recognition of 4-aminophenol

Abstract

No presente trabalho um polímero com impressão molecular (MIP) seletivo para 4-aminofenol (4-APh) foi sintetizado através de técnica de polimerização em bulk. A polimerização foi realizada em tubo de vidro contendo 4-APh, Fe(III)protoporfrina(IX) (hemina, Fe(III)PPIX), ácido metacrílico (MAA), etileno glicol dimetacrilato (EGDMA) e 2,2'-azo-bis-iso-butironitrila (AIBN). O bloco de polímero foi moído e peneirado (106 µm) e o 4-APh foi removido das partículas do polímero pela extração com solução de metanol/ácido acético (4:1, v/v), deixando uma cavidade nas partículas do polímero. A hemina foi usada como um material sintético para imitar o centro ativo da peroxidase, criando um polímero com impressão molecular cataliticamente ativo. Os polímeros foram caracterizados por espectroscopia no infravermelho, análises termogravimétricas, microscopia eletrônica de varredura e análise do tamanho das partículas. O desempenho enzimático do polímero impresso foi avaliado baseado em parâmetros cinéticos incluindo V max e constante de Michaelis-Menten obtidas pelo gráfico de Lineweaver-Burk.In the present work a selective molecularly imprinted polymer (MIP) for 4-aminophenol (4-APh) was synthesized by the bulk polymerization technique. Polymerization was carried out in a glass tube containing 4-APh, Fe(III)protoporphyrin(IX) (hemin, Fe(III)PPIX), methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA) and 2,2′-azo-bis-iso-butyronitrile (AIBN). The polymer block was ground and sieved (106 µm) and the 4-APh was removed from the polymer particles by leaching with a methanol/acetic acid (4:1, v/v) solution, which leaves a cavity in the polymer particles. Hemin was used as a synthetic material to mimic the active center of peroxidase creating a catalytically active molecularly imprinted polymer. The polymers were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and particle size analysis. The enzymatic performance of the imprinted polymer was evaluated based on kinetic parameters including V max and the Michaelis-Menten constant obtained from Lineweaver-Burk plots. Keywords: molecularly imprinted polymers (MIP), hemin, 4-aminophenol, MichaelisMenten IntroductionMolecular imprinting is a useful technique for the preparation of ligand-selective cavities in synthetic polymer matrices. [1][2][3] Recently, the technique has attracted significant interest from a large number of areas within chemistry and the analytical sciences due to the relative ease with which these polymers may be prepared, the range of template structures that are amenable for use and the apparent mechanical and chemical stability of the types of polymers generally synthesized.Briefly, the technique may be described as follows. A template molecule is allowed to form reversible interactions (covalent or non-covalent) with suitable functionalized monomers in the presence of a cross-linking monomer. Polymerization affords a highly cross-linked macroporous polymer containing cavities with sites varying complementari...

A hemin-based molecularly imprinted polymer (MIP) grafted onto a glassy carbon electrode as a selective sensor for 4-aminophenol amperometric

“…MIP was synthesized using a larger amount of solution than that used in the traditional polymerization [14], with hemin as the catalytic center to mimic the active site of peroxidase. The procedure was possible due to the unique structural features of the hemin molecule, as well as the controlled interactions between the functional monomer (MAA) and the template (4-APh).…”

“…In this sense, MIPs were recently synthesized in our laboratory for use as catalytic recognition centers [13][14][15] in the detection of phenolic compounds of biological and environmental interests. In order to improve the detection process, the preparation of an amperometric sensor for 4-aminophenol detection employing a hemin-based MIP grafted onto a glassy carbon (GC) electrode surface using Nafion ® is proposed.…”

Direct use of superparamagnetic nanoparticles as electrode modifiers for the analysis of mercury ions from aqueous solution and crude petroleum samples

“…Among the large variety of chemically modified electrodes, self assembled supramolecular porphyrin films [12][13][14] have been successfully employed as electrode coatings, providing effective electrochemical gates for the detection of analytes such as sulphite, nitrite, ascorbic acid, dopamine and several drugs. Nafion films and polymers have also been extensively employed as electrode modifiers, for many different purposes [15], including molecular imprinting [16]. Analogously, immobilized enzymes have been applied in selective redox catalysis [17], and more recently, metal nanoparticles [18][19][20] and carbon nanotubes [21] have also been explored as versatile electrode modifiers.…”

Superparamagnetic Carbon Electrodes: A Versatile Approach for Performing Magnetic Coupled Electrochemical Analysis of Mercury Ions

“…Molecular species, such as the self assembled supramolecular porphyrin films [5][6][7] have been successfully employed as electrode coatings, providing effective electrochemical gates for the detection of analytes such as sulfite, nitrite, ascorbic acid, dopamine and several drugs. Nafion films and polymers have also been extensively employed as electrode modifiers [8,9]. Immobilized enzymes have been applied in selective redox catalysis [10] and more recently, metal nanoparticles [11][12][13] and carbon nanotubes [14] have also been explored as versatile electrode modifiers.…”