Microfluidic devices for single-cell Raman spectroscopy of irradiated cancer cells

Raman spectroscopy exploits inelastic scattering of monochromatic light via transitions in molecular vibrational modes to yield a spectrum of chemical information. Since it is non-invasive and label-free, Raman spectroscopy is being considered for application in monitoring and predicting radiosensitivity of cancer cells, with the ultimate goal of achieving personalized radiotherapy in a clinical setting. Recent studies have begun to investigate the integration of microfluidic devices with single-cell Raman spectroscopy to increase its low throughput, however, spectral features governing radiosensitivity have yet to be resolved in this manner. Herein, four microfluidic devices, with integrated optical traps were designed, fabricated, and tested. In addition, Raman spectra were acquired to characterize the materials and microscope objectives used, three flow controllers were tested, and calculations were performed to estimate maximum volumetric flow rates to achieve optical trapping. Two of the devices consisted of quartz capillaries – square or round – mounted on an in-house microscope stage. The round capillary device was further refined with a three dimensional (3D) printed casing to allow for concentric flow focusing. The other two devices consisted of patterned polymer layers – structured by ultraviolet 8-epoxy-based negative photoresist (SU-8) or polydimethylsiloxane (PDMS) – between two glass cover slips. The SU-8 device was fabricated via standard photolithography and the PDMS device was fabricated via soft lithography. Both featured cross junctions for flow focusing and insertion of optical fibres for the optical trap. The square capillary device failed as optical trapping could not be achieved, the SU-8 device failed as it could not be sealed, and the PDMS device failed as the optical fibres could not be inserted. To date, the round capillary device has been the most successful, with demonstrated flow focusing and optical trapping capabilities using syringe pumps at μL/min and μL/hr rates, respectively. Acquiring spectra from trapped polystyrene divinylbenzene (PS DVB) microspheres with a 100× dry objective has resulted in aberrant peaks that are uncharacteristic of PS DVB microspheres, requiring further investigation. Further refining will be needed as the transition from PS DVB microspheres to live cells is made.Science, Irving K. Barber Faculty of (Okanagan)Computer Science, Mathematics, Physics and Statistics, Department of (Okanagan)Graduat