Fast and easy measurements of the blood alcohol content are needed, e.g., in law enforcement. The detection of alcohol levels also has applications in food chemistry. Alcohol can be quantified in the lab, but simple methods for use in the field, such as breath analyzers, can be particularly useful. However, existing breath analyzers that measure alcohol levels have limited reliability and are usually complemented by blood analyses. Biosensors based on alcohol-specific enzymes such as alcohol oxidase (ALOx) could be an alternative.

Silvana Andreescu, Clarkson University, Potsdam, NY, USA, and colleagues have developed a low-cost 3D-printed device with an enzyme- and nanoparticle-based biosensor immobilized on paper. The team used paper that was modified with the enzyme alcohol oxidase (ALOx), cerium oxide nanoparticles (CeNPs), and poly(ethyleneimine) (PEI) as a colorimetric sensor. The sensor is place in 3D-printed holder made from polylactic acid that the user can blow into.

The oxidation of ethanol with ALOx produces H₂O₂ as a byproduct. PEI layers are used to immobilize the enzyme on the paper. CeNPs react with the produced H₂O₂, leading to a color change that depends on the H₂O₂ concentration. The color change can be seen with the naked eye or captured using a smartphone camera. The sensor provides high selectivity, good stability, and low cost. According to the researchers, the sensor could be adapted to measure alcohol levels in other types of samples

• A 3D-Printed Breath Analyzer Incorporating CeO₂ Nanoparticles for Colorimetric Enzyme-Based Ethanol Sensing,
  Fatima Mustafa, Megan Carhart, Silvana Andreescu,
  ACS Appl. Nano Mater. 2021.
  https://doi.org/10.1021/acsanm.1c01826