Fluorescent nanodiamond based relaxometry for free radical sensing in live cells upon pathogen infections

This thesis explores the feasibility to apply nanodiamond-based relaxometry for free radical detection in viral and bacterial infection systems. Specifically, Chapter 2 evaluates and explains the interaction between the <100>, <110>, and <111> surfaces of the single crystal diamond with biomolecules, cell culture medium, mammalian cells, and bacteria. Chapter 3 offers an overview of different techniques for free radicals detection post-virus infection, including optical probes, ESR, lipid peroxidation and DNA damage detection, and evaluating of radical-related enzyme activities. The mechanism, advantages, and disadvantages of different methods are discussed. In Chapter 4, we elucidate the utility of diamond relaxometry for studying the free radical response of baby hamster kidney-21 cells upon Semliki Forest virus infection. The site-specific and time-resolved features of diamond relaxometry are emphasized by comparing the radical response at random locations and at pathogen sites via conjugating viruses to nanodiamond sensors. In Chapter 5, we utilize diamond-based quantum sensing for studying the alterations of the free radical response near S. aureus in macrophages using S. aureus-nanodiamond conjugates. The dynamic immuno-radical response from the host and microorganism’s antioxidant defense is investigated. Lastly, Chapter 6 discusses the importance and relevance of this thesis, as well as the future perspectives and potential applications of this research.