A Thermoelectric Device for Coupling Fluid Temperature Regulation During Continuous Skin Sonoporation or Sonophoresis

A compact and low-frequency drive ultrasound transducer for facilitating cavitation-assisted drug permeation via skin

Low-frequency sonophoresis has emerged as a promising minimally invasive transdermal drug delivery method. However, effectively inducing cavitation on the skin surface with a compact, low-frequency ultrasound transducer poses a significant challenge. This paper presents a modified design of a low-frequency ultrasound transducer capable of generating ultrasound cavitation on the skin surfaces. The transducer comprises a piezoelectric ceramic disk and a bowl-shaped acoustic resonator. A conical slit structure was incorporated into the modified transducer design to amplify vibration displacement and enhance the maximum sound pressure. The FEM-based simulation results confirmed that the maximum sound pressure at the resonance frequency of 78 kHz was increased by 1.9 times that of the previous design. Ultrasound cavitation could be experimentally observed on the gel surface. Moreover, 3 min of ultrasound treatment significantly improved the caffeine permeability across an artificial membrane. These results demonstrated that this transducer holds promise for enhancing drug permeation by generating ultrasound cavitation on the skin surface.

Biomechanical Sensing Using Gas Bubbles Oscillations in Liquids and Adjacent Technologies: Theory and Practical Applications

Gas bubbles present in liquids underpin many natural phenomena and human-developed technologies that improve the quality of life. Since all living organisms are predominantly made of water, they may also contain bubbles-introduced both naturally and artificially-that can serve as biomechanical sensors operating in hard-to-reach places inside a living body and emitting signals that can be detected by common equipment used in ultrasound and photoacoustic imaging procedures. This kind of biosensor is the focus of the present article, where we critically review the emergent sensing technologies based on acoustically driven oscillations of bubbles in liquids and bodily fluids. This review is intended for a broad biosensing community and transdisciplinary researchers translating novel ideas from theory to experiment and then to practice. To this end, all discussions in this review are written in a language that is accessible to non-experts in specific fields of acoustics, fluid dynamics and acousto-optics.

Physical triggering strategies for drug delivery

Physically triggered systems hold promise for improving drug delivery by enhancing the controllability of drug accumulation and release, lowering non-specific toxicity, and facilitating clinical translation. Several external physical stimuli including ultrasound, light, electric fields and magnetic fields have been used to control drug delivery and they share some common features such as spatial targeting, spatiotemporal control, and minimal invasiveness. At the same time, they possess several distinctive features in terms of interactions with biological entities and/or the extent of stimulus response. Here, we review the key advances of such systems with a focus on discussing their physical mechanisms, the design rationales, and translational challenges.

Percutaneous Delivery of Antihypertensive Agents: Advances and Challenges

Hypertension remains a significant risk factor for several cardiovascular disorders including coronary artery disease and heart failure. Despite the large armamentarium of drugs available for the management of high blood pressure, low oral availability is an ongoing challenge. Researchers are constantly developing alternative drug delivery systems. This review focuses on the transcutaneous delivery of antihypertensive agents. The use of diverse technologies for the delivery of specific antihypertensive agents is emphasized. The advances made and the challenges encountered are highlighted. Several transdermal drug delivery strategies are employed for the transport of this group of therapeutic agents across the skin and the most widely used techniques include microneedles, iontophoresis, sonophoresis, and chemical penetration enhancers. Each of these methods has benefits and limitations, and there are ongoing attempts by scientists to address the shortcomings. For instance, skin irritation continues to be a major challenge with iontophoretic transport while the quantity of a medication that can be incorporated into dissolving microneedles is limited. With skin permeation enhancers, concerns relating to cytotoxicity and irritation are common. Even though the use of ultrasound is exciting, this mode of delivery is also accompanied by challenges such as the design of a battery system that is potent enough to drive a low-frequency sonophoretic cymbal array, while still being portable enough to function as a wearable device. Although most researchers report enhanced drug delivery with the aforementioned methods, it is important to deliver therapeutically useful doses of these medications.