Comparative studies of different signal acquisition systems in microfluidic paper-based analytical devices developed for accurate point-of-care analysis

The exponential growth of small, on-hand devices/sensors has been aligned with the increasing use of smartphones as detectors. However, smartphone detection may result in high variability of signal acquisition, due to differences in lighting conditions, consequently compromising accurate and reliable quantification. The use of smartphones for qualitative assessment (“yes/no” response) has been widely employed; however, their use in quantitative assessment has been less reported. For point of care (POC) analysis, the use of smartphones as detectors can be an exceptional advantage; however, it is crucial to ensure that the accuracy of the analysis is not compromised. A critical and structured evaluation of image acquisition systems was performed to evaluate the impact on POC biomarkers quantification with microfluidic paper-based devices (μPADs). Different image acquisition systems were tested for a μPAD to properly evaluate the impact of lighting conditions when using a smartphone in a specially designed box. The decrease in intensity counts was about 30% from the scanner to the smartphone, but it did not affect the calculated absorbance. We proved that smartphones can be used as reliable detection systems, providing accurate and precise quantification when appropriate attention is given to exterior lighting conditions. When quantifying iodide and nitrite in a sample, a relative error of 5% was observed for both image-acquiring systems, a scanner and a smartphone.