Feasibility of using focused acoustic vortex for enhancing transdermal delivery

Area of Science:

• Biomedical Engineering
• Acoustics
• Dermatology

Background:

• Transdermal drug delivery offers a convenient, noninvasive administration route.
• Skin's stratum corneum presents a significant barrier to drug penetration.
• Existing ultrasound methods for enhancing transdermal delivery raise safety concerns due to high energy and cavitation.

Purpose of the Study:

• To introduce and evaluate a novel 1-MHz focused acoustic vortex (FAV) approach for transdermal drug delivery.
• To overcome the safety limitations associated with conventional ultrasound-enhanced transdermal delivery methods.

Main Methods:

• Utilized phase dislocations to generate a 1-MHz focused acoustic vortex (FAV) with spiral wave motion.
• Induced localized vortical flow with high shear stress.
• Measured streaming velocity and assessed penetration enhancement of hydrophilic dyes (Evans blue, dextran) in porcine and rat skin models.

Main Results:

• FAV instantaneously induced stable vortical flow (2.4 mm diameter) within 10 seconds.
• Optimal parameters (1 MPa, 60% duty cycle) yielded peak streaming velocity (1.6 ± 0.4 mm/s).
• Sonication (3 min) with FAV significantly enhanced dye penetration (3.3-fold for EB, 2.1-fold for dextran in porcine skin) compared to conventional focused ultrasound.
• FAV doubled EB penetration in rat skin without adverse effects like temperature elevation or inertial cavitation.

Conclusions:

• The FAV approach effectively enhances transdermal drug penetration by permeabilizing the stratum corneum.
• FAV offers a safer alternative to conventional ultrasound methods, avoiding cavitation and thermal risks.
• This technique holds promise for improving the efficacy of transdermal drug delivery systems.