Experimental validation of theoretical method for prediction of acoustic streaming around a resonantly-excited cancer cell

摘要

In a recent research paper. "Acoustic streaming around a spherical microparticle/cell under ultrasonic wave excitation" by Liu and Kim, a theoretical method was proposed to computationally-efficiently and accurately predict acoustic streaming around a resonantly-excited human cancer cell. It was also predicted that small microparticles around the cell could be circulating along the acoustic streaming lines. This theoretical phenomenon can be applied to identify the resonance frequencies of the cell. In addition, the identified resonance frequencies are expected to accurately infer the mechanical properties, of the cell, such as density and compressibility due to the high sensitivity of the resonance frequencies to these properties. Here, the acoustic streaming around MCF-7 human breast cancer cells was observed experimentally to validate the theoretical method. A microfluidic device fabricated with a photolithography technique and the cancer cells cultured with a sub-culturing process were used for this experiment. The cancer cells and 2 μm Carboxylate microparticles suspended in the cell culture medium were injected into the microfluidic device. The device was then excited by a piezoelectric actuator with a sine wave in the frequency range of 20 kHz to 130 kHz. The resonance frequency range of 28.7 kHz to 42.0 kHz was then identified experimentally when the microparticles were in circulatory motion around a cancer cell. The predicted resonance frequency range from a simulation was 26.24 kHz to 35.30 kHz, which is slightly lower than the experimental one due to potential minor errors in estimating the cell modeling parameters. Since the acoustic streaming velocity was generated at much lower frequency than cell's resonance frequencies, an inexpensive camera at 20-30 frames/second could be used to capture the motion of the microparticles. Along with the simple, inexpensive microfluidic chip and actuator, this experiment could be set up more inexpensively than existing cell resonance measurement methods.