Polyelectrolyte Based Sensors as Key to Achieve Quantitative Electronic Tongues: Detection of Triclosan on Aqueous Environmental Matrices.

Cátia Magro,Maria Raposo,Eduardo Pires Mateus,Paulo Ribeiro,Paulo Zagalo,João Pereira-Da-Silva,Alexandra Branco Ribeiro

doi:10.3390/nano10040640

Abstract

Triclosan (TCS) is a bacteriostatic used in household items that promotes antimicrobial resistance and endocrine disruption effects both to humans and biota, raising health concerns. In this sense, new devices for its continuous monitoring in complex matrices are needed. In this work, sensors, based on polyelectrolyte layer-by-layer (LbL) films prepared onto gold interdigitated electrodes (IDE), were studied. An electronic tongue array, composed of (polyethyleneimine (PEI)/polysodium 4-styrenesulfonate (PSS))5 and (poly(allylamine hydrochloride/graphene oxide)5 LbL films together with gold IDE without coating were used to detect TCS concentrations (10−15–10−5 M). Electrical impedance spectroscopy was used as means of transduction and the obtained data was analyzed by principal component analysis (PCA). The electronic tongue was tested in deionized water, mineral water and wastewater matrices showing its ability to (1) distinguish between TCS doped and non-doped solutions and (2) sort out the TCS range of concentrations. Regarding film stability, strong polyelectrolytes, as (PEI/PSS)n, presented more firmness and no significant desorption when immersed in wastewater. Finally, the PCA data of gold IDE and (PEI/PSS)5 sensors, for the mineral water and wastewater matrices, respectively, showed the ability to distinguish both matrices. A sensitivity value of 0.19 ± 0.02 per decade to TCS concentration and a resolution of 0.13 pM were found through the PCA second principal component.

Highlights

Triclosan (5-chloro-2-(2,4-dichlorophenoxy) phenol) (TCS) is widely used as an antimicrobial, antibacterial and preservative agent in different personal care and consumer products [1]
TCS was spiked to the aqueous matrices and measured using thin-films sensors based on polyethyleneimine (PEI), poly(sodium 4-styrenesulfonate) (PSS), poly(allylamine hydrochloride) (PAH), and graphene oxide (GO; Figure 1), which have been prepared with the LbL technique onto solid supports with deposited gold electrodes
As demonstrated by Taylor and Macdonald [47], the electrical properties of each thin-film, deposited on the interdigitate electrodes (IDE), when immersed in the aqueous sample, are dependent on the characteristics of the thin-film used as a sensitive layer, of the double layer formed on the surface of all the thin-films and of the bulk electrolyte

Summary

Introduction

Triclosan (5-chloro-2-(2,4-dichlorophenoxy) phenol) (TCS) is widely used as an antimicrobial, antibacterial and preservative agent in different personal care and consumer products [1]. Recent studies [34,35,36,37,38] have reported well succeeded applications with sensors composed of layer-by-layer (LbL) thin-films, which were produced with polyelectrolytes and used to detect organic compounds (in ultrapure water matrices and methanol) using impedance measurements. TCS was spiked to the aqueous matrices and measured using thin-films sensors based on polyethyleneimine (PEI), poly(sodium 4-styrenesulfonate) (PSS), poly(allylamine hydrochloride) (PAH), and graphene oxide (GO; Figure 1), which have been prepared with the LbL technique onto solid supports with deposited gold electrodes. An array of sensor devices without and with different polyelectrolyte thin-films deposited onto IDE surface was used to detect the TCS in aqueous solutions. The ANOVA was performed at 95% of confidence (p < 0.05), concerning the Table 1 data, to prove that they are statistically different

Impedance Spectroscopy Measurements

Principal Component Analysis

Electronic Tongue—Sensor Sensitivity and Resolution

Conclusions