Layer-by-Layer Engineered Microreactors for Bio-Polymerization of 4-(2-aminoethyl) phenol hydrochloride
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A5.43.1
Layer-by-Layer Engineered Microreactors for Bio-Polymerization of 4-(2-aminoethyl) phenol hydrochloride R. Ghan1, T.Shutava1, A.Patel1, V.John2, Y.Lvov1* 1 Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA, 71270 2 Department of Chemical Engineering, Tulane University, New Orleans, LA 70118 ABSTRACT This study presents the results of polymerization of phenol to yield fluorescent polymer encapsulated within shells fabricated via layer-by-layer (L-b-L) assembly. Hollow polyelectrolyte microcapsules (shells) were prepared using weakly cross-linked melamine formaldehyde (MF) particles. Dissolution of the MF cores was achieved by changing the pH of the solution. Horseradish peroxidase (HRP), the catalyzing enzyme, was loaded in these capsules by taking advantage of the “open/close” mechanism of the capsules by altering the pH. The empty shells were then suspended in a concentrated solution of monomer. Since the monomer is a low molecular weight species, it freely permeates through the polyion wall into the shells. Addition of aliquots of hydrogen peroxide initiated the polymerization reaction and the polymer formed from the ensuing reaction was confined in the shells due to its high molecular weight. The model used for demonstrating this synthesis is polymerization of 4-(2-aminoethyl) phenol hydrochloride commonly known as tyramine hydrochloride to its corresponding polymeric form by reacting it with hydrogen peroxide. Fluorescence spectrometry (FS), confocal laser scanning microscopy (CLSM), and atomic force microscopy (AFM) were the characterization methods employed to confirm polymerization in situ shells. INTRODUCTION Chemical synthesis in micron and submicron confined volumes are now under intensive investigation. Applications of reversed micellar systems [1], porous materials [2], and zeolite cages [3] for organic and inorganic synthesis have recently been shown. A layer-by-layer (L-b-L) assembly of oppositely charged polyelectrolytes, proteins, and nanoparticles allows creation of thin multilayered films with nanometer thickness [4]. Application of L-b-L assembly to micronsized cores results in the formation of hollow micron sized capsules after dissolution of the cores [5]. Until now several different approaches for encapsulation of proteins inside polyelectrolyte capsules have been proposed [6-8]. Urease [6-8], peroxidase [7], α-chymotrypsin [8], and glucose oxidase [9] have been encapsulated and high-activity retention of encapsulated enzyme has been proven. It has been shown that capsules with protein posses good stability and little or no release of encapsulated enzyme takes place during their storage [10]. The polyelectrolyte capsules provide interesting possibilities to design catalyst-rich micro-volumes in bulk water phase. Unique permeability properties of the walls of the hollow capsules allow the retention of proteins and polymers, but low molecular weight substrates can easily permeate in and out through the walls making these microcapsules unique “reactors” for biocataly
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