Cytokine detection methodologies on optical fiber substrate

Sensitive and localized measurements of cytokines are important in biomedicine, medical research and clinical applications. The classic cytokine detection methods including ELISA, ELISPOT, and Western blot are reliable but with limited sensitivity, and they are only applicable to accessible biological fluids such as blood plasma. However, the cytokines are locally released (i.e. at the site of injury or disease), and measurements of their systemic levels in body fluids provide only a limited insight into the undergoing processes. Thus, to understand the role of the immune system in disease or multiple health conditions which lead to immunoreactivity and the expression of cytokines, the development of a method with sufficient sensitivity that can directly measure the locally released cytokine is highly desirable. The focus of my Ph.D. research program is the development of sensitive cytokine immunosensors based on optical fiber allowing localized and spatially resolved cytokines detection. Specifically, my research project aims to advance the sensitivity of the cytokine immunosensor and explore the biological application of the designed immunosensor from in vitro to in vivo. The first paper (Chapter 2) demonstrated a cytokine detection device based on aminopropyltriethoxysilane-gold nanoparticle-6-mercaptohexanoic acid modified silica optical fiber for the monitoring of locally variable cytokine interleukin-6 concentrations using a sandwich immunoassay scheme. In the second paper (Chapter 3), we further extended the application of the way for fabrication immunosensor in the first paper and designed an optical fiber-based immunosensing device for repeated monitoring of spatially localized cytokine interleukin-1beta release in the rat brain. To further enhance the performance of the immuosensor, in the third paper (Chapter 4), a more sensitive and robust immunosensing system was designed based on biotin-streptavidin coupling for spatially localized femtogram mL−1 level detection of interleukin-6 in serum samples, then in the fourth paper (Chaper5), we further extended the application of the immunosensor that prepared by the biotin-streptavidin system in the rat spinal cord.