A paper-based point-of-care testing device for the colourimetric estimation of bilirubin in blood sample.

A paper-based colourimetric assay for the Point-of-Care Testing (PoCT) of bilirubin has been developed based on the formation of a green-coloured copper-bilirubin complex from a blue-coloured tetraamminecopper(II) sulphate complex. The reaction was studied and optimized by UV-Visible absorption spectroscopy and translated onto a paper strip. Hydrophobic circular well patterns on Whatman chromatography paper were created by wax printing. The tetraamminecopper(II) sulphate complex was drop cast and dried on the reagent zones in the wax-patterned paper. The images of reagent zones captured using a scanner were analyzed using ImageJ software. Bilirubin spiked blood serum was tested in the concentration range of 1.2 to 950 µM. The PAD exhibited sensitivities of 0.4197 a.u/µM and 0.1040 a.u/µM for concentration ranges of bilirubin 1.2 to 96 µM and 105 to 950 µM respectively and a low detection limit of 0.799 µM. The method is highly selective to bilirubin, even in the presence of other biomarkers in serum. A plasma separation membrane incorporated PAD was fabricated for the final testing and quantification of bilirubin from whole blood.

Paper based micro/nanofluidics devices for biomedical applications.

This chapter details the significance, fabrication and biomedical applications of paper-based microfluidic devices. The first part of the chapter describes the importance of paper diagnostic devices, highlighting pretreatment, dipsticks, lateral flow assays, and microPADs. Various methods followed for the fabrication of the paper analytical devices are discussed in the second part. The last part is about some of the important biomedical applications of paper analytical devices. Finally, the challenges and research gaps in the paper microfluidics for biomedical applications are presented.

Development of a paper-based analytical device for the colourimetric detection of alanine transaminase and the application of deep learning for image analysis.

A paper-based colourimetric assay for the detection of alanine transaminase has been developed. In the presence of alanine transaminase, 2,4-dinitrophenyl hydrazine changes to pyruvate hydrazone leading to a colour change from pale yellow to dark yellow. Reaction conditions were optimized using absorption spectroscopic studies. Hydrophobic patterns on the Whatman chromatographic paper were created by wax printing, and the reagents were drop cast at the reagent zone. On the paper device, the intensity of the yellow colour increases with ALT concentration in the range of 20-140 U/L in human serum. For the quantification of ALT, coloured images were captured using a digital camera and were processed with Image J software. The machine learning approach was also explored for the ALT analysis by training with colour images of the paper device and testing using a cross-validation procedure. The results obtained with real clinical samples on the paper device showed good accuracy of less than 5% relative error with the clinical lab results. Furthermore, the paper device shows high selectivity to ALT in the presence of various interfering species in blood serum with a sensitivity of 0.261 a.u/(U/L), a detection limit of 4.12 U/L, and precise results with an RSD of less than 7%. For the testing of whole blood, a plasma separation membrane was integrated with the patterned paper.