A novel ultrasonic stimulation system to enhance cell viability using piezoelectric micromachined ultrasonic transducers (pMUTs) with transwells

Abstract

A new ultrasonic cell stimulation system was designed and fabricated using 10 by 10 and 10 by 29 piezoelectric micromachined ultrasonic transducer (pMUT) arrays. The sizes of pMUT arrays are 2.5 by 2.5 mm and 2.27 by 6.84 mm. The diameter and pitch of pMUT arrays are 120 µm and the measured resonance frequency of each single pMUT element was 1.494 MHz in water. The acoustic peak pressures are 0.22 MPa and 0.18 MPa for 10 by 10 pMUT and 10 by 29 pMUT, respectively. The spatial average temporal average (SATA) intensity are 612.8 ± 183 mW/cm2 and 200 ± 22 mW/cm2 which are converted by the acoustic pressure of 10 by 10 and 10 by 29 pMUT array. The fabricated pMUT arrays were attached on print circuit boards (PCBs) and wire bonding was done for electrical connection. Each PCB and pMUT array was coated with parylene C for biocompatibility and waterproofing. For cell culturing, a twelve-well transwell was assembled one a PCB with ten pMUT arrays by epoxy. After curing the epoxy, polydimethylsiloxane (PDMS) was coated on the epoxy to enhance biocompatibility of the ultrasonic cell stimulation system. The size of the cell stimulation system is 13.4 ☓ 17.3 ☓ 2.5 cm and it is small enough to place the whole system in an incubator. The fabricated ultrasonic cell stimulation system was used for cell stimulation to characterize the effect of ultrasonic cell stimulation for proliferation of PC12 cells. Ultrasonic cell stimulations were performed for 16 groups in combination of stimulation time for 5 min, 10 min, 20 min, and 30 min and duty cycle for 15 %, 30 %, 50 % and 70 %. There was also a control group without ultrasonic stimulation. All of the stimulated groups showed positive effect on cell proliferation. For the most significant effect, the 5 min stimulation group showed more increased number of the cells as 238 %. Furthermore, the proliferation pattern was different along the stimulation time, not duty cycle. As a result, short stimulation time and long stimulation time occurred different tendency. Short stimulation groups showed 118 %, 122 %, and 134 % increase rate of cell number during stimulation, however long stimulation groups showed 117 %, 105 %, and 152 % increase rate of cell number during stimulation. Long time stimulation group has different increase pattern after last stimulation. In this thesis, new ultrasound cell stimulation system using the pMUT was developed for overcoming the limitation of conventional cell stimulation system using bulk ceramic transducer. After cell stimulation for PC12 cells, all stimulation group has averagely 150 % increase rate of cell number than control group. ⓒ 2015 DGIST