Low-cost paper-based platforms for immunodiagnostic and enzymatic testing

Author(s)

Thiago Mazzú do Nascimento

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2016-12-09

Examining board members

Emanuel Carrilho; Fernanda Canduri; Daniel Sivieri Cordeiro

• Advisor: Emanuel Carrilho

Abstract

Immunoassays and bioassays are broadly used in clinical medicine. Paper-based devices are ideal to be used in remote regions due to their low-cost, portability and the possibility of in loco manufacture. Paper-based immunoassays are extremely versatile, capable of detecting distinct analytes: initially we have developed an immunochromatographic assay to detect rabbit IgG in a paper-based device fabricated using wax printing technology, and we have shown that this prototype has potential to be applied in distinct immunoassays. The second developed paper-based device was an enzymatic colorimetric assay for the detection of a potential prostate cancer biomarker - sarcosine (sarcosine oxidase, peroxidase and redox indicator (ABTS)), obtaining good figures or merit (LOD = 0.21 mmol L-1; LOQ = 0.61 mmol L-1, r² = 0.890). The third developed paper-based device was capable of detecting toxoplasmosis (IgG against Toxoplasma gondii in human serum samples). The performance evaluation showed a cut-off = 21.73 A.U., sensitivity = 0.96, specificity = 0.87, AUC = 0.97, besides defining the gray zone as the zone comprehended in-between 15% over the cut-off value. We also have developed a Microsoft Excel® macro to calculate diagnostic test\'s accuracy - m-Accuracy - that is a new way to calculate accuracy with great innovation for clinical medicine, which resulted in an accuracy of 0.88. for toxoplasmosis assay. The fourth developed paper-based device was used to detect CEA tumor biomarker using a sandwich ELISA assay, with a cut-off = 68.28 A.U., sensitivity = 0.86, specificity = 1.0, AUC = 0.97. The defined gray zone to this test was the zone comprehended in-between 12% over the cut-off value, with an accuracy of 0.90. To the best of our knowledge, this is the first complete statistical evaluation of paper-based diagnostic devices, which showed the great potential of this technology to be used as a new point-of care diagnostic tool. (AU)

• FAPESP's process: 11/13997-8 - Paper-based platforms for noninvasive detection of tumor biomarkers and cultive neoplastic cells
• Grantee: Thiago Mazzu Do Nascimento
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)