Microwave-based microfluidic biosensors: from the design and implementation to real-time sensing.

• Ano de defesa: 2022
• Autor(a) principal: Shahri, Atena Amanati
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Alterações na permissividade relativa; Biosensors; Biossensor de micro-ondas; Biossensores; Célula viva única; changes in relative permittivity; Dielectric spectroscopy; Espectroscopia dielétrica; Glicose; Glucose; Microwave biosensor; Single living cell; Tecnologia de micro-ondas
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/3/3140/tde-31032023-081427/

Observing biological matters is a crucial step in medical applications. Conventional techniques of cell study are very well established and effective. However, their detection method is based on fluorescence imaging techniques and staining that can be invasive to cells. Microwave dielectric spectroscopy is a novel and non-destructive analytical methodology to investigate biological matters without chemical binding or prior preparation and manipulation that eliminates the modification of the content. Furthermore, it provides the attractive advantage of real-time monitoring. This thesis aimed to develop microfluidic integrated microwave-based biosensors capable of measuring the dielectric properties of biological matters such as glucose and cell suspensions for cell characterization. After reviewing the current state of art analysis methods, we focused on developing high-sensitivity microwave biosensors to investigate biological matters. During the development, the microwave components, design structures, and fabrication processes were optimized to improve the performance of the biosensors regarding sensitivity and repeatability. First, the evolution of the biosensor performance was assessed by measuring the amplitude, phase, and frequency shifts at the absorption peak as a function of glucose concentrations in water solutions. Our sensing device distinguishes the variation of glucose concentrations around 5.2 GHz and is considered to be simple, easy to operate and highly sensitive (0.32 MHz/(mg/dL). Then the research followed by investigating more complex biological structures, and single living cells in culture medium were detected in their flow stream for cell quantification purposes. The changes in the S-parameter were measured over time at the resonant frequency to conduct the dielectric measurement of cell suspensions. The device proposed in the present work distinguished cells from the medium measuring a difference of approximately 23º in the phase of the transmitted signal. This biosensor could detect rapid flowing cells in their biological medium in real-time and hence can be used as an early diagnosis and monitoring tool for diseases.