How active are the microorganisms in your yogurt? New cardboard sensor to study probiotic activity

Juliana L. M. Gongoni (a), George Chumanov (b), Thiago R. L. C. Paixão (a) and Carlos D Garcia (b)

(a) University of Sao Paulo (Brazil), (b) Clemson University

A simple and fast (<15 min), two-step laser scribing of cardboard substrates is described as a method for fabricating carbon electrodes modified with metallic nanoparticles. The first scribing step patterned a cardboard substrate (promoting the formation of porous carbon electrodes). The second step was included to produce metallic nanoparticles via a chemical reduction process of cations from an aqueous solution. For these experiments, the effects of copper, silver, nickel, cobalt, zinc, and gold were evaluated considering their effect on the electrical properties and the composition of the carbon materials produced. These experiments revealed that, despite significant changes in resistance (from 138±7 Ω for plain electrodes to just 53±3 Ω for Au-modified electrodes), only marginal changes were observed in the morphology or composition of the material produced (I_G/I_D ranged from 1.2±0.3 for the plain cardboard to 1.8±0.3 for the cobalt-modified electrodes). To demonstrate the applicability of the proposed strategy, Au-modified electrodes were assembled into electrochemical sensors and applied to measure the metabolic activity of live microorganisms in various commercial samples, requiring only 100 μL of sample and 10 min of incubation time.