A study published last monday at Scientific Reports: Nature Publishing Group concludes that office paper can be used as a sensor for electrochemically active bacteria detection.

Electrochemically active bacteria have the ability to transfer electrons to cell exterior towards insoluble electron acceptors. “This feature has been currently explored in the development of sustainable technologies in bioremediation field, specifically to remove polluting compounds from the environment, and in the bioenergy field, specifically for production of electrical current from the bacterial metabolism in microbial fuel cells”, explains Carlos Salgueiro, head of the Biochemistry and Bioenergetics of Heme Proteins Research Group at UCIBIO@requimte, specialized on the characterization of extracellular transfer processes on these bacteria. However, the number of isolated and characterized electrochemically active bacteria species is still very limited regarding their abundance in nature. “The detection methods currently available are slow, expensive and complex”, explains Elvira Fortunato, director of I3N, therefore “it is critical to develop a rapid, inexpensive and simple detection method is critical for the optimization of the applications mentioned above”. Elvira Fortunato, co-inventor of the paper electronics concept worldwide, says that “main goal of this work was the development of a paper-based colorimetric sensor that uses an electrochromic material, tungsten trioxide, as the active layer for the detection of electrochemically active bacteria”.

The design of the sensor was defined by printing and diffusing a wax layer that generated the solution wells delimited by hydrophobic barriers onto the paper (lab-on-paper technology). The tungsten trioxide nanoparticles, synthesized through a microwave assisted hydrothermal method, were deposited in the wells by drop casting. The nanoparticles with hexagonal crystallographic structure were able to successfully detect an electrochemically active bacteria, Geobacter sulfurreducens, from an early growth stage to a late-exponential growth stage. The authors of the article describe for the first time the development of a paper-based sensor and colorimetric detection method that revealed sensibility and specificity for detection of these bacteria, in a rapid, simple and inexpensive way. Ana Carolina Marques, the first author of the article, obtained her Master degree on Biochemistry at FCT, last December.

The research work results from a collaboration between the research team led by Elvira Fortunato at I3N and the research team led by Carlos Salgueiro at UCIBIO@requimte. Both research units classified were classified with Exceptional in the recent research unit evaluation (2014) delivered by the European Science Foundation and by the Portuguese Foundation for Science and Technology. 

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