Development and validation of a 3D-printed spectral verification system for colorimetric-based biosensors: DOI 10.14622/JPMTR-2006

We propose a method to transfer colorimetric assays based on gold nanoparticle aggregation from the laboratory toclinics, practices, or even to an application at home, by creating printed biosensors. While colorimetric assays needlaboratory equipment and trained personnel, our printed biosensors (through manual pipetting) are storable, portableand usable from anyone anywhere. The method is verified using a model system for detection of the analyte aminoacid cysteine (cys) and a spectral experimental setup in transmission. The model system consists of dispersed goldnanoparticles, which aggregate after cys addition. The biosensor is created by pipetting droplets of a gold nanoparticlesolution onto the carrier Hostaphan GN 4600. Its functionality is sustained during the drying process throughan addition of glucose, which preserves the gold nanoparticles from aggregation through its amorphous state. Theglucose mixture can be kept amorphous over a long time by controlling the surrounding humidity with silica gel beadsin an airtight container. The sample mount for the experimental setup is 3D-printed and designed to measure thespectral transmittance of the biosensor before and after analyte addition. The characterization of the setup suggeststo expect coefficients of variation below 1 %, which validates its use. The biosensor and transmission spectrometerare tested with analyte concentrations between 10 mM and 50 mM. After a successful verification the printed biosensorwould be ready to be evaluated without special equipment, meaning visually or with commercially availableimaging techniques. Keeping in mind the possible application at home, the most obvious solution is using your owneyes or smartphone. These methods are discussed in the outlook.Keywords: spectrometer, gold nanoparticle aggregation, color change, ready to use, printed biosensor