This article introduces a novel inkjet printing method for the fabrication of a microfluidic paper-based analytical device (μPADs) with improved analytical performance for colorimetric measurements. Firstly, a hydrophobic boundary was created by wax printing on chromatography paper. Then, chitosan (CHI), 3,3',5,5'-Tetramethylbenzidine (TMB) and enzymatic mixture solvent (glucose oxidase (GOx) and horseradish peroxidase (HRP)) were sequentially printed in the sensing zone. Polyethylene glycol (PEG6000) was mixed with the bienzymatic solution to act as an enzyme stabilizer, forming the printable ink. The resulting μPADs exhibited a linear relationship between color intensity and glucose concentration from 0.0 25 mg/ml to 0 .5mg/ml. The detectable glucose concentration was in a clinically relevant range from 0.01 mg/ml to 4 mg/ml. The limit of detection (LOD) was achieved at 0.01 mg/ml. After 60-day storage under 4 °C, the color intensity at the testing zone retained over 80% of the original intensity. In addition, a smartphone application was developed for in situ colorimetric image processing, and the colorimetric analysis results were compared with those from the use of a scanner followed by processing using ImageJ. Furthermore, the development of this ink printing method also provides a point of care (POC) platform for other substances detection purposes.
Keywords: Colorimetric detection; Glucose; Inkjet printing; Smartphone-based assay; μPAD.