Improved biosensors towards accessible health care diagnostics

Author(s)

Amanda Hikari Imamura

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2022-03-18

Examining board members

Emanuel Carrilho; William Reis de Araujo; Michelle Khine; Juliane Renata Sempionatto Moreto; Álvaro José dos Santos Neto

• Advisor: Emanuel Carrilho

Abstract

Point-of-care (POC) testing provides diagnostic tools centered on the patient rather than dispersed in different locations (hospitals, clinics, doctor\'s offices). POC biosensors are often integrated into miniaturized systems and consist of portable and cheaper devices with fast output than conventional clinical analysis. However, significant challenges still exist in the miniaturization field, addressed in this dissertation. In Chapter II, the immobilization of biomolecules on paper was optimized by oxidating the cellulose with NaIO4. The oxidation was extensively characterized since it affected the physicochemical properties of the paper. Moreover, the oxidized paper was applied to quantify protein in urine, detecting early cases of microalbuminuria. Chapter III describes an alternative fabrication method for wearable microfluidic devices using the toy Shrinky-Dinks (SD). As a proof-of-concept, a wearable colorimetric device for glucose and lactate was demonstrated. Although the assays lacked detectability and sensitivity to detect glucose and lactate in sweat, the SD-based microfluidic channels demonstrated the capability of continuously collecting sweat without disturbing the user. Chapter IV describes a sensitive and stretchable electrode fabricated by the same premise of SD wearable devices. The stretchable wrinkled electrodes quantified glucose at a concentration range from 0.1 µmol L-1 to 0.1 mmol L-1 in physiological pH, demonstrating the applicability for sensing in sweat. Finally, Chapter V describes two electrochemical biosensors for faster and more accessible diagnosis tools for widespread testing for COVID-19. Although they present different approaches, both biosensors were portable and detected the S protein of SARS-CoV-2 in microliters of saliva without requiring chemical supplies. The improvements described in this dissertation on immobilization, fabrication process, and detection will hopefully contribute to further works on the development of biosensors to finally reach commercial ends and broaden access to health care. (AU)

• FAPESP's process: 17/05362-9 - Development of wearable biosensor based on microfluidic paper-based analytical devices (uPAD) for cortisol analysis in sweat
• Grantee: Amanda Hikari Imamura
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)