Biological activities investigated by single cell analysis at nanoscales

Single cell analysis is required to decipher a myriad of cellular processes; however, it is very challenging to develop a single cell analysis method with high sensitivity, excellent selectivity and high spatiotemporal resolution. This PhD research project focuses on the innovation of a unique optical and electrical single cell sensing platform to understand the physico-chemical fundamentals involved in the detection schemes and to investigate physiological processes in single cells for cell biology studies as well as disease diagnosis. An optical fiber based nanobiosensor has been first constructed to detect the over-expression of a general cancer biomarker, telomerases in single cancer cells. The antibody-immobilized nanoprobe inserted into MCF-7 cell nucleus shows significantly higher average (F-F0)/F0 ratio than that of the negative control human mesenchymal stem cell (hMSC) nucleus. The average (F-F0)/F0 ratio in the MCF-7 cytoplasm is significantly smaller than that in the nucleus to clearly verify the nuclear localization of telomerase. The nanobiosensor may provide a potential method for cancer detection, and also demonstrate a universal approach to detect other low expression proteins in a single living cell. To study tumor metabolism at single cell level, a unique nanoscale optical fiber lactate sensor has been developed to successfully distinguish the higher extracellular lactate concentrations of cancer cells from that of normal cells, which supports Warburg hypothesis. Furthermore, lactate efflux inhibition profiles after exposure to a monocarboxylate transporter (MCT) inhibitor are different for HeLa and MCF-7 cancer cells demonstrating the nanosensor’s potential to evaluate the effect of metabolic agents on cancer metabolism and survival. A bifunctional electro-optical nanoprobe with integrated nanoring electrode and optical nanotip has also been designed to simultaneously detect both electrical and optical signals in real-time with high spatial resolution.DOCTOR OF PHILOSOPHY (SCBE