This article discusses the application of photoacoustic flow cytometry (PAFC) for analyzing ovarian cancer cells. The method leverages the absorption of laser light by nanoparticles within the cells to generate acoustic signals, which are then detected and processed for data acquisition.
Photoacoustic flow cytometry, or PAFC, utilizes the ability of biological samples to absorb laser light of a specific wavelength and emit acoustic sound waves. Begin by taking a suspension of the desired nanoparticle-bearing ovarian cancer cells in one syringe and air in a second syringe. Load the two syringes onto two separate syringe pumps set to their respective flow rates. The pumps deliver their contents through flexible tubes that merge to administer small volumes of sample trapped between alternating air bubbles to a pre-assembled flow chamber.
As the sample passes through the flow chamber, irradiate the cells using a short-pulsed laser of an appropriate wavelength. Localized absorption of laser energy by the nanoparticles within the cancer cells generates heat, causing thermoelastic expansion that produces acoustic sound waves. A pre-assembled transducer detects the acoustic signals and transmits them to a receiver. The receiver amplifies the signals and relays them to an oscilloscope for data acquisition. The oscilloscope processes the data and transfers them to a computer that displays information relating to the detected cancer cells.
Use the provided three-dimensional STL file to 3D-print the flow tank with either ABS thermoplastic or PLA plastic. After printing the tank, clean and assemble the system for use. Place glass coverslips over the 1 millimeter by 3 millimeter slot and the 1-centimeter hole in the flow system and carefully seal with silicone to prevent leakage. Next, fit the capillary tube into the silicone cured tubes. Insert the tubes into the flow chamber through the side of the flow tank such that the glass capillary tube is directly above and in front of the 3-millimeter slot and the 1-centimeter hole.
Seal the tubing with silicone. Then, connect the transducer to an ultrasound pulser and receiver. Amplify the signal with a 59 decibel gain. Connect the output of the filter to a multipurpose reconfigurable oscilloscope equipped with a built-in field-programmable gate array. Connect one of the tubes coming from the flow chamber to a T-junction that is connected to two syringe pumps at each branch. Fill one of the syringe pumps with air and the other pump with the sample to be analyzed.
Set the pump containing air to a flow rate of 40 microliters per minute, and set the pump containing the sample to a flow rate of 20 microliters per minute. Next, connect the remaining tube exiting the flow system to a container of 10% bleach to dispose off cells after they exit the flow system. Place the section of the quartz capillary tube in direct alignment with the transducer in the field view of the microscope to allow for careful placement of the optical fiber above the sample such that it illuminates the entire width of the tube. Irradiate the sample using an optical fiber channeling a diode-pumped solid-state laser operating at a wavelength of 1,053 nanometers. Use a microscope-mounted camera to record the flow, the firing of the laser, and the passage of samples through the flow system.
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