Galvanic microcells as control agent of indoor microorganisms

Abstract

Today, fungicides are part of the basic tool kit for indoor surface maintenance. However, fungi develop resistance to fungicides, which consequently accelerates the evolution of virulence. Fungicides also carry the risk of adverse effects in humans. Galvanic microcells are a new tool for fungal control on indoor surfaces. We used two types of electrodes, Zn and Cu, with two potential anti-fungal mechanisms: the oligodynamic action of the metal ions themselves and the electricidal effect of the current between the electrodes. The size of the inhibition zone is related to the distance between the electrodes. We hypothesized that the unique geometric properties of the observed inhibition zone could be modelled using multi foci curve Cassini ovals. Moreover, the size of the inhibition zone possessed two maximum values, while the shape of the observed inhibition zones correlated with the shape of the electric field strength. The control activity of the galvanic microcells correlated with decreasing water content in building materials. Thus, this acute antifungal system works the best in damp building environments where the risk of fungal contamination is highest.

Figure 1. Inhibition zones (IZs) of copper-zinc galvanic cells for Cladosporium cladosporoides.

(A) Proposed correlation of IZ overhead views with the shapes of Cassini ovals; (B) A Cassini oval with foci F1 and F2 on the x-axis defined by the equation d₁d₂ = b²; (C) A disturbed Cassini oval defined by the equation d₁^αd₂^β = b²; (D) Schematic of a Petri dish with metal bar zinc and copper electrodes used in the experiments.

Figure 2. Correlation of the observed inhibition zones with the geometry of the electric field generated by zinc-copper galvanic cells.

(A) IZ of Ulocladium atrum, electric field strength and disturbed Cassini oval equation d₁^1.49312d₂^0.50688 = 14.43225² calculated from experimentally measured points from the IZ margin; (B) Colours show the energy density and electric field; (C) Cladosporium cladosporioides, (D) Ulocladium atrum, (E) Rhodotorula mucilginosa IZ shape and corresponding electric field generated by galvanic cell copper-zinc with micrographs of mycelium.

Figure 3. Barrier protection by copper-zinc galvanic microcells against fungal colonization (Penicillium spinulosum).

(A) styrene blister with copper-zinc microcells; (B) pure styrene blister of the same size and thickness; (C) Petri plate showing the inhibition effect of the zinc-copper galvanic microcells.