Abstract
The preparation of redox-active coatings is a key step in fabricating electrochemical biosensors. To this goal, a variety of coating materials have been used in combination with redox-active compounds. In this study, alizarin red S (ARS) was confined in layer-by-layer (LbL) films composed of poly(ethyleneimine) (PEI) and carboxymethylcellulose (CMC) to study the redox properties. A gold (Au) disc electrode coated with PEI/CMC LbL film was immersed in an ARS solution to uptake ARS into the film. ARS was successfully confined in the LbL film through electrostatic interactions. The cyclic voltammogram (CV) of ARS-confined PEI/CMC film-coated electrodes thus prepared exhibited redox waves in the potential range from −0.5 to −0.7 V originating from 9,10-anthraquinone moiety in ARS, demonstrating that ARS preserves its redox activity in the LbL film. An additional oxidation peak appeared around −0.4 V in the CV recorded in the solution containing phenylboronic acid (PBA), due to the formation of a boronate ester of ARS (ARS-PBA) in the film. The oxidation peak current at −0.4 V decreased upon addition of 3,4-dihydroxyphenylalanine (L-dopa) to the solution. Thus, the results suggest a potential use of the ARS-confined PEI/CMC films for constructing voltammetric sensors for L-dopa.
Highlights
Layer-by-layer (LbL) polyelectrolyte films have been widely used for the development of biosensors [1,2], surface coatings [3,4,5], drug delivery systems [6], and so forth
LbL films composed of PEI and CMC were coated on the surface of the Au disc electrode, which had been polished with alumina slurry and thoroughly rinsed in deionized water
Polyelectrolyte LbL films are often used as scaffold to immobilize small ions and molecules for constructing functional surface coatings [21]
Summary
Layer-by-layer (LbL) polyelectrolyte films have been widely used for the development of biosensors [1,2], surface coatings [3,4,5], drug delivery systems [6], and so forth. ARS-PBA-modified electrodes are useful for the development of electrochemical devices. We report here a facile protocol for the preparation of ARS-immobilized LbL films and their use. We report here a facile protocol for the preparation of ARS-immobilized LbL films and their use for the electrochemical determination of L-dopa. To this goal, we used an Au disc electrode coated for the electrochemical determination of L-dopa. The ARS-confined PEI/CMC film-coated electrodes prepared exhibited a pair prepared exhibited a pair of redox peaks in the CV, showing that ARS is redox active even in the of redox peaks in the CV, showing that ARS is redox active even in the LbL films. Electrode as a voltammetric sensor for the determination of L-dopa
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