Thermoresponsive Poly(N-isopropylacrylamide) Gel for Immobilization of Laccase on Indium Tin Oxide Electrodes

Abstract

We report on the properties of hydrogel matrix for the immobilization of laccase on conductive supports. The poly(N-isopropylacrylamide) gel is attached firmly to the indium-tin oxide (ITO) electrode, following its silanization with dimethylethoxyvinylsilane. The enzyme entrapped in the gel structure remained active longer than in the solution, and its redox and catalytic properties could be investigated by voltammetric methods. The reduction signals of the active sites, T1 and T2, of the Cerrena unicolor laccase were determined to be 0.79 and 0.38 V, respectively. The laccase catalytic activity toward oxygen in poly(N-isopropylacrylamide) was found to depend strongly on temperature. Reversible swelling/shrinking of the matrix was studied at 30 and 35 degrees C. Shrinking of the gel at higher temperature considerably decreased the efficiency of the catalytic reaction, however, interestingly, did not lead to irreversible changes in the enzyme structure. At temperatures below that corresponding to volume phase transition, the catalytic properties of the film were fully restored. High catalytic efficiency of the gel immobilized enzyme made it possible to employ the gel covered electrode for monitoring oxygen in solutions.

Enzyme immobilization: an update

“…The most studied example is the thermo-responsive and biocompatible polymer, poly-Nisopropylacrylamide (polyNIPAM) [58]. Aqueous solutions of polyNIPAM exhibit a critical solution temperature (LCST) around 32°C, below which the polymer readily dissolves in water while, above the LCST it becomes insoluble owing to expulsion of water molecules from the polymer network.…”

Biocathodes for Dioxygen Reduction in Biofuel Cells

“…These interactions have more recently been explored to form osmium polymer laccase electrode by layer-by-layer self-assembling on Au modified with 3-mercaptopropyl sulfonate [104]. The use of nonfunctionalized thermoresponsive poly (N-isopropylacrylamide) gel for stable laccase immobilization should be mentioned in this context [148].…”

“…In the former case this mediator was found to be superior to other water-soluble mediators in terms of current density [56]. The catalytic effect is also observed with laccase encapsulated in porous material such as dialysis membrane [195], sol-gel processed silicate [91,139,169,173,176,199], lipid cubic phases [179,180,182], and poly(N-isopropylacrylamide) gel [148] or bilirubin oxidase encapsulated in the sol-gel processed film modified with CNTs [171,172]. The pores formed by the sol-gel processed polymer (silicate) or peptide assembly--like cubic phases (Fig.…”

Quartz crystal microbalance electrode modified with thermoresponsive crosslinked and non-crosslinked N-isopropylacrylamide polymers. Response to changes in temperature

“…Because of their environmental sensitivity and unique structure, these polymeric hydrogels have been employed in a variety of fields, e.g., in controlled drug release systems, artificial muscles, sensors, molecular recognition systems, and as specific sorbents. Their attachment to the surface of an electrode improves their usefulness in, e.g., surface patterning, construction of switchable sensors/biosensors and more [8][9][10][11][12][13][14][15][16].…”