Translating optics to clinics : ultra-large-scale single-cell biophysical phenotyping for cancer pre-screening

Abstract

Liquid biopsy has long been widely used in clinics for medical diagnosis. Since the discovery of the circulating tumor cell (CTC) which appears starting from the early stage of cancer, liquid biopsy for cancer pre-screening becomes plausible. However, the extreme rarity of CTCs in the heterogeneous blood cell population imposes a grand challenge on its accurate detection in the early stage. Though biomolecular technologies provide promising measurements of CTCs, its high-cost in labelling them impedes its widespread usage in a general population-wise cancer pre-screening. To this end, a cost-effective CTC detection approach is necessitated for an early cancer diagnosis. In this thesis, a label-free approach, termed ultra-large-scale single-cell biophysical phenotyping, is presented. Based on the combination of ultrafast optics, microfluidics and high-speed reconfigurable computing, it critically addresses the need for high throughput, high sensitivity and high specificity in the CTC detection. In the first chapter, an overview of cancer diagnostic techniques and the challenge of CTC detection are covered. The next three chapters encompass three essential technological advancements in enabling the label-free assay. It starts with the speed advancement of a quantitative phase imaging (QPI) modality for single-cell imaging of a large cell population in a short time. Then, it is followed by the translation of this high-speed QPI imaging module to a high-throughput imaging flow cytometry. With a wealth of biophysical phenotypes of cells from QPI, specific identification of cancer cells without relying on any exogenous contrast agent is demonstrated. Finally, it comes to a newly developed hydrodynamic focusing scheme which is able to precisely control cell stream in the cytometer and boost the sensitivity of this label-free assay for rare cell detection. By rendering all these elements, the ultra-large-scale single-cell biophysical phenotyping for CTC detection is enabled. In the following two chapters, the work on validating this label-free assay is presented. By integrating with the immunofluorescence detection, a cytometer which can deliver both the biophysical phenotyping and biomolecular measurement is developed. Based on this instrumentation, an in-vivo CTC detection on mouse xenograft is demonstrated which sheds light on the potential use of this label-free assay in the clinical CTC detection. With all these works, I conclude our group achieved a milestone of the label-free CTC detection, which shows high potential in giving a population-wise cancer pre-screening to improve the survival rate of cancer patients.