SPAIN – The detection of toxic pollutants is an essential element in the analysis and control of water quality. This is necessary in an increasingly urbanized and industrialized world. Chemical analysis techniques are useful for identifying specific substances, but they have limitations when analyzing complex samples that may contain multiple pollutants.  In this regard, appropriate use of biosensors, with the effect that a sample on a biological element such as enzymes or protein- or a vital parameter of an indicator organism is measured.

According to graduate student Ferran Pujol from University of Barcelona, who has done work as part of their doctoral thesis, the innovation of the sensor lies in the fact that it is using matrices absorbent incorporated with bacteria to make a colorimetric measurement of toxicity. To make matrices, researchers have used the Escherichia coli (E. coli) as model bacteria.

The detection technique proposed and validated by researchers is simple and fast.  In fact, it used similar strips of paper to measure the water pH. Samples to be tested are added to the matrix with a dye, ferricyanide, which turns from yellow to colorless when transformed into ferrocyanide after being e breathed by microorganisms.

The paper changes color depending on the intensity of cellular metabolism of bacteria inversely proportional to the toxicity of the sample. So, the more color change occurs is detected means less contamination.  This change can be measured by optical techniques, image analysis or the eye.

Bioassay, for which researchers have applied for a patent, detects any pollutant that is toxic to microorganisms in the testing time -after about 15-30 minutes of contact with cell-, such as heavy metals and hydrocarbons such as oil or benzene.  The technique is applicable to both natural waters, urban and industrial waste.

The fact that the technology is using a material such as paper and does not require complex instrumentation makes this biosensor a simple, low cost effective technique and a good candidate for the detection of toxicity in the context of economic constraint in developing countries, according to the authors.

The work has been published in Analytica Chimica Acta.