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Physical stimulations and their osteogenesis-inducing mechanisms

way referred to place the injury sites in an electric 5.3 The Mechanical Stimulation Systems
field or place the electrodes on the surface of the
treatment sites [152,153] . It had been widely accepted by Low intensity pulsed ultrasound treatment had received
patients owing to the small trauma. In vitro studies, widespread attention in treatment bone fracture due to
some researchers placed electrodes on top and bottom the advantages of safety, non-invasive, no infection and
[155]
surfaces of each well and then connected the electric less complication . The ultrasonic stimulation used
field device to stimulate cells [154] . Many researchers used by most researchers was usually generated by the Sonic
sinusoidal alternating electric field which consisted of Accelerated Fracture Healing System, which could
[81,156,157]
function generator and parallel electrodes to expose pro duce different frequencies and intensities .
[14]
bone cells [49,79] . Kim et al. designed a biphasic electric Different devices were used to carry out different
current system to stimulate osteoblasts which consisted mechanical stimulations for bone cells and tissues. The
of Teflon® culture dish, two evaporated Au plates, BiopressTM system was used by many researchers to
media and biphasic current stimulator. The anodes apply compressive loads. It could control load magnitude
and cathodes of each well were connected to form an to compress osteoblasts membrane to investigate the
[137,158]
electrical shunt configuration and all electrodes were effects of compression stress on osteoblasts .
[159]
connected to the biphasic electric current stimulator chip Zhong et al. designed a cellular cyclic tension and
[75]
(Figure 8D). Banks et al. customized an ibidi device compression apparatus to investigate the biological
to create an electric field stimulation system which response of osteoblasts under stretching or compressing.
allowed to simultaneously stimulate six cell migration The apparatus could control the carrier rod to precisely
chambers, and 6 pairs of agar bridges in physiologic shift up and down. Many researchers used a parallel-
buffered saline connected cell migration channels to plate flow chamber to induce fluid flow over the cells
[93,94,160,161]
[162–164]
reservoirs of physiologic buffered saline, in which Ag- to construct fluid shear stress . You et al.
AgCl electrodes were immersed (Figure 8E). established a flow system which was driven by an
electromagnetic actuator.

A B C

D E F

G H

Figure 8. The schematic of the physical stimulation systems. (A) static magnetic field exposure system [120] . (B) pulse electromagnetic field
exposure system [136] . (C) Magnetic stimulation on artificial bone . (D) Biphasic electric current stimulation system . (E) Direct current
[14]
[66]
electric stimulation system . (F) Electric stimulation consisted of a parallel electrode used to stimulate cells seeded on scaffold . (G)
[75]
[79]
Flexercell compression plus system was used to compress osteoblasts membrane [137] . (H) Mechanical stimulation bioreactor system was
[22]
used to perfuse scaffolds seeded with cells .
12 International Journal of Bioprinting (2018)–Volume 4, Issue 2