Low-Intensity Amplitude Modulated Ultrasound Increases Osteoblastic Mineralization

The purpose of this study was to assess the effect of pulsed amplitude modulated ultrasound (pAMUS) on the level of mineralization in osteoblast cell in comparison to cells stimulated with low-intensity pulsed ultrasound (LIPUS). To make the ultrasound effects more enhanced and targeted at region of interest, this study uses a novel approach of applying pulsed amplitude modulated ultrasound to osteoblast cells. The pAMUS signal was generated using two signal generators. Pulsed signal was amplified through a power amplifier and drove two identical focused ultrasound probes, focusing at the same point in the culture dish. The effects of pAMUS were evaluated using a pAMUS signal of 45 kHz and 100 kHz with 20% duty cycle. The hydrophone verified the formation of a focal point at equal distances (16 mm) from the surface of both transducers. Intensity profile using computer controlled 2D scanner showed circular focal point with a diameter of approximately 10 mm. The effect of the signal was studied using MC3T3-E1 cells cultured in osteogenic medium at time points Day 7, 12 and 18. The cells were analyzed for ALP activity and calcium mineralization. The pAMUS significantly increased the ALP activity and matrix calcification in comparison with LIPUS stimulated cultures.