Desenvolvimento de tecnologias alternativas para fabricação de dispositivos microfluídicos em papel

Abstract

This current study describes the development of alternative technologies for the fabrication of microfluidic paper-based analytical devices (μPADs). The first technology refers to the manufacturing of a metal stamp for rapid prototyping of μPADs. Basically, the method uses the heating process to transfer wax to the paper surface. The wax is required to create a hydrophobic barriers thus delimiting microfluidic channels for the fluid transport through lateral flow effect. Some remarkable advantages of the metal stamping process include robustness, portability and simplicity. Paraffin is a hydrophobic and thermoplastic material that can be easily molded. Furthermore, it shows high chemical resistance when exposed to different aqueous and organic solutions. The stamping-based technology allows the fabrication of μPADs at very low cost. The proposed approach exhibited great reproducibility. The relative standard deviation (RSD) for the channel widths measured on 50 independent μPADs revealed a value of 3.5%. The analytical performance of the paper-based device associated with colorimetric detection was tested for the nitrite analysis in clinical, food and environmental samples. The limit of detection (LD) nitrite assays without preconcentration was 11.3 μM. In order to access the nitrite concentration in environmental samples, a preconcentration method was developed allowing to achieve a LD of 5.6 μM. The results obtained were compared to the spectrophotometric technique and the statistical test demonstrated no significant difference between both methodologies. The stamping process have demonstrated high potential to produce μPADs in laboratories with none or minimal instrumentation. Besides the stamping process, another fabrication approach based on the spraying of white glue mixed with a sensitizing agent was also proposed to produce μPADs. To create effective hydrophobic barriers, the white glue was first sprayed on the paper surface though a magnetic mask. Afterwards, the device was exposed to visible light for polymerization of the glue. In order to evaluate the fabrication methodology, 25 devices were produced and the RSD value achieved for the channel widths was 5.7%. The analytical feasibility of the μPADs fabricated with white glue was successfully demonstrated for qualitative assays dedicated to urinalysis (glucose, uric acid, nitrite, pH, BSA, urea, ketones bodies and bilirubin) and pancreatitis assay (amylase and lipase). Both alternative methods based on stamping and spraying has exhibited great potential to be used for production in mass. Moreover, the proposed devices revealed high potential to be broadly explored in biological/clinical, food and environmental applications.