Office paper and laser printing: a versatile and affordable approach for fabricating paper-based analytical devices with multimodal detection capabilities.

Multiple protocols have been reported to fabricate paper-based analytical devices (PADs). However, some of these techniques must be revised because of the instrumentation required. This paper describes a versatile and globally affordable method to fabricate PADs using office paper as a substrate and a laser printing technique to define hydrophobic barriers on paper surfaces. To demonstrate the feasibility of the alternatives proposed in this study, the fabrication of devices for three types of detection commonly associated with using PADs was demonstrated: colorimetric detection, electrochemical detection, and mass spectrometry associated with a paper-spray ionization (PSI-MS) technique. Besides that, an evaluation of the type of paper used and chemical modifications required on the substrate surface are also presented in this report. Overall, the developed protocol was suitable for using office paper as a substrate, and the laser printing technique as an efficient fabrication method when using this substrate is accessible at a resource-limited point-of-need. Target analytes were used as a proof of concept for these detection techniques. Colorimetric detection was carried out for acetaminophen, iron, nitrate, and nitrite with limits of detection of 0.04 μg, 4.5 mg mL -1 , 2.7 μmol L -1 , and 6.8 μmol L -1 , respectively. A limit of detection of 0.048 fg mL -1 was obtained for the electrochemical analysis of prostate-specific antigen. Colorimetric and electrochemical devices revealed satisfactory performance when office paper with a grammage of 90 g m -2 was employed. Methyldopa analysis was also carried out using PSI-MS, which showed a good response in the same paper weight and behavior compared to chromatographic paper.