Ultrasound-mediated transdermal insulin delivery. A) In vitro transport profile of insulin across human skin in the presence of ultrasound (20 kHz, 100-ms pulses applied every second) at 12.5 (■), 62.5 (◆), 125 (●), and 225 mW/cm2 (▲) (n = 3 or 4). B) In vitro transdermal insulin permeability with different ultrasound intensity (20 kHz, 100-ms pulses applied every second) (n = 3 or 4). Adapted with permission from Ref [114].