Immobilized Saccharomyces cerevisiae viable cells for electrochemical biosensing of Cu(II)

Abstract

Electrodes functionalised with weak electroactive microorganisms offer a viable alternative to conventional chemical sensors for detecting priority pollutants in bioremediation processes. Biofilm-based biosensors have been proposed for this purpose. However, biofilm formation and maturation require 24-48 h, and the microstructure and coverage of the electrode surface cannot be controlled, leading to poorly reproducible signal and sensitivity. Alternatively, semiconductive biocompatible coatings can be used for viable cell immobilization, achieving reproducible coverage and resulting in a stable biosensor response. In this work, we use a polydopamine (PDA)-based coating to immobilize Saccharomyces cerevisiae yeast viable cells on carbon screen printed electrodes (SPE) for Cu(II) detection, with potassium ferricyanide (K₃[Fe (CN)₆]) as a redox mediator. Under these conditions, the current output correlates with Cu (II) concentration, reaching a limit of detection of 2.2 µM, as calculated from the chronoamperometric response. The bioelectrochemical results are supported by standard viability assays, microscopy, and electrochemical impedance spectroscopy. The PDA coatings can be functionalised with different mutant strains, thus expanding the toolbox for biosensor design in bioremediation.

Keywords: Saccharomyces cerevisiae; Bioremediation; Biosensors; Extracellular electron transfer; Polydopamine.

Fig. 1

(a) Bare surface of WE, (b) PDA-coated WE, (c) S. cerevisiae cells immobilized in PDA on the WE.

Fig. 2

Viability of WT, ∆hap4 and ∆rtg2 S. cerevisiae strains incubated for 18 h in YPD medium supplemented with 10—100 µM CuSO₄.

Fig. 3

(a) Nyquist plot; (b) Bode phase plot; (c) DRT plot of Sample 1 between −100 and 400 mV with a step potential of 50 mV; (d) Schematic of the equivalent circuit.

Fig. 4

(a) Interfacial resistance for all samples. (b) Effective capacitance for all samples.

Fig. 5

CA of PDA coating with S. cerevisiae WT cells with glucose, glycerol, and ethanol as the carbon source at 0.4 V, with different concentration of CuSO₄ (0, 10, 50, 100 µM) under aerobic conditions.

Fig. 6

Current density of PDA coating with S. cerevisiae WT cells with glucose, glycerol, and ethanol as the carbon source with different concentration of CuSO₄ (0, 10, 50, 100 µM) under aerobic conditions after 2500 s of incubation at E = 0.4 V.

Fig. 7

CA of Current density of PDA coating with S. cerevisiae WT, Δhap4 and Δrtg2 cells at 0.4 V with different concentration of CuSO₄ (0, 10, 50, 100 µM) under aerobic conditions.

Fig. 8

Current density of PDA coating with S. cerevisiae WT, Δhap4 and Δrtg2 cells at 0.4 V with different concentration of CuSO₄ (0, 10, 50, 100 µM) under aerobic conditions after 2500 s of incubation.