Photoacoustic detection of circulating tumor cells

Abstract

Photoacoustics is one of the new branches in biomedical diagnostics that holds lot of new promises and advancements. It is a unique field that deals with the conversion of photons into ultrasound waves. It is only in the recent years has the full potential of photoacoustics been explored in cancer detection and imaging. This dissertation throws light on the process of development and validation of the photoacoustic based sensor and metastatic cell detection in mice. An optical photoacoustic sensor based on the change in refractive index was developed to detect individual melanoma cells. The sensitivity of the optical based detector was high and has the resolution to determine the presence of extremely low number of metastatic and cultured cells (2 cells) in the suspension containing a million white blood cells. A signal to noise ratio of 3:1 was achieved in detection of cultured melanoma cells. Both stationary and flow chambers were developed and integrated to the photoacoustic detection system. Single cell detection of both injected and induced metastatic melanoma cells was successfully obtained by using the probe of the ultrasound machine as the transducer. Dual wavelength study at 532 nm and 622 nm was adopted to rule out the possibility of detection of stray red blood cells in the illuminated volume of the photoacoustic flowsystem. Efforts were also made to detect single non melanotic cancer cells in flow chamber by tagging EGCG gold nanoparticles to PC-3 (human cultured prostate cancer cell line). 10 PC-3 cells tagged to gold nanoparticles were made to flow in 10 mL of the buffer and were detected at different time points of circulation. New flow chambers, based on polymerization of Loctite monomer were fabricated that are more economical, faster to make and also disposable. The new flow chambers added to the user friendly approach towards photoacoustic metastatic cancer cell detection. Finally, research and development of the new two phase flow system to break the cell suspension continuum into uniform slugs or bubbles of cells suspensions of 3 [Mu]L in volume, separated by equal volume air pockets was successfully integrated with the photoacoustic flow system. This new flow system opened up new avenues to capture and isolate the detected metastatic cells that can be further subjected to genetic and pharmacological analysis as an effective drug development tool. Hence, this dissertation explores the role of photoacoustics in a plethora of applications aimed towards isolation and detection of single metastatic cancer cells in blood.