Interactions of inertial cavitation bubbles with stratum corneum lipid bilayers during low-frequency sonophoresis

Low-frequency ultrasound alleviates pulmonary inflammation induced by Klebsiella pneumoniae in mice by inhibiting the TNFR1/NF-κB pathway

BACKGROUND

Therapeutic ultrasound has been found to promote tissue healing and reduce inflammation in non-infectious diseases, but its efficacy in infectious inflammation remains unclear. Here, we employ the mice pneumonia model to explore the anti-inflammatory effects of low-frequency ultrasound (LFU) and elucidate its potential molecular mechanisms.

METHODS

Pneumonia in mice was induced by intratracheal instillation of 100 μL of a 4.5 × 108 CFU/mL Klebsiella pneumoniae (Kp) bacterial suspension. A single LFU treatment (29.36 kHz, 270 mW/cm2, 10 min) was applied to the chest of mice at 6 or 48 h after infection. Biological samples were collected for gene, protein, and cellular experiments.

RESULTS

LFU demonstrated good anti-inflammatory effects in mice during the recovery phase of Kp infection (48 h after infection). Although LFU alone had no bactericidal effects, it slightly reduced the pathological score of lung injury and significantly decreased the infiltration of CD45+ leukocytes. Additionally, the protein levels of TNF-α, GM-CSF and COX-2 in the bronchoalveolar lavage fluid were significantly reduced. Bulk RNA-sequencing results showed that the TNF receptor (TNFR)/NF-κB pathway was up-regulated after Kp infection, which was suppressed after LFU treatment. Western blot and immunofluorescence revealed LFU significantly reduced the protein levels of TNFR1, p-p65, and nuclear p65. The anti-inflammatory effect of LFU was comparable to a 20 mg/kg NF-κB inhibitor and superior to a 15 mg/kg TNFR antagonist.

CONCLUSION

LFU exerts anti-inflammatory effects by inhibiting the TNFR1/NF-κB pathway during the recovery period of Kp infection, reducing inflammatory transcription and thereby decreasing the release of inflammatory factors.

Development of a dual-frequency sonophoresis for enhanced skin permeability and efficient drug delivery

Effective transdermal drug delivery has long been a research focus, constrained by the skin's selective permeability, which limits the passage of drugs larger than 500 Daltons. Sonophoresis, employing low-frequency ultrasound waves, enhances skin permeability through transient cavitation, but its application faces two significant challenges: delivering large molecules and reducing prolonged treatment durations. This study introduces a novel dual-frequency sonophoresis designed to address these limitations. Through the integration of high-frequency ultrasound with low-frequency waves, a synergistic effect was generated, enhancing transient cavitation process. In few studies on dual-frequency systems, there has been challenges of large system size and long treatment duration. In our novel proposed system, the size was reduced by utilizing a piezoelectric disc operating at high frequency, and through a precise positioning relative to low-frequency ultrasonic horn, the synergistic effect was maximized, thus the treatment time was reduced. Initial tests employed single-frequency setup on aluminum foil, utilizing a two-level experimental design to maximize transient cavitation effects. The resulting optimal operating conditions were then applied to the dual-frequency system. Subsequent experiments were carried out on both aluminum foil and ex vivo guinea pig skin samples. It was observed that integration of high- and low- frequency ultrasound resulted in a remarkable 51-fold increase in skin permeation. Meanwhile, the penetration time was significantly reduced to four minutes in comparison with twenty minutes using single-frequency system. The obtained results highlighted the potential of our newly proposed dual-frequency sonophoresis to improve transdermal drug delivery efficiency by enhancing molecule transfer rates and minimizing treatment durations.

Transdermal administration of macromolecular drugs by multi-frequency sequential ultrasonic irradiation

Administration methods of macromolecular drugs with high efficacy and minimal side effects are generally limited to highly invasive injections due to their components and large molecular weight. Here, we propose a sequential ultrasonic irradiation method using multi-frequency for minimally invasive administration of macromolecular drugs. In this demonstration, low-frequency ultrasound (kHz band) and high-frequency ultrasound (MHz band) were sequentially irradiated onto the porcine skin to evaluate the dosing efficiency using fluorescence-modified ovalbumin (Mw = 45 kDa), a macromolecular drug model. Quantitative evaluation of the transdermal dosage by fluorescence intensity measurement shows that the proposed method significantly increased the transdermal dosage by almost double that of the conventional method. In particular, the distance of MHz ultrasonic irradiation is indicated to influence the dosing efficiency. In addition, the evaluation of transdermal permeability by confocal observation of skin sections shows that the macromolecular drug model penetrates through the epidermis of porcine skin, including the stratum corneum, to the dermis layer with the proposed method. The proposed method permeated the drug model with a behavior correlated to the intensity of the MHz ultrasonic beam, as opposed to the discrete penetration of the drug model in the conventional method. Our results provide a minimally invasive method of administering macromolecular drugs as an alternative to injection.

Microbubble-Enhanced Transdermal Drug Delivery Sonoelectric Patch

Transdermal drug delivery systems are highly appealing as a convenient drug delivery manner applicable to a wide variety of drugs. While most delivery relies on only passive diffusion and suffers low transdermal efficiencies. Ultrasound motivation promotes drug transdermal penetration but still calls for improvement, because only a thin proportion of the ultrasound energy is applied on the drug delivery patch and most ultrasound energy is wasted in deeper portions of biotissues. In this work, we develop a transdermal patch for enhanced drug delivery. The combination of microsized air pockets and the piezoelectric soft structure enable the conversion of an intended proportion of ultrasound energy into electric energy. The intensified drug flow and synergistic ultrasound pressure and electric field function simultaneously to enhance drug transdermal delivery. The delivery efficacy is related to the power of the ultrasound motivation, the size of the microscopic air pockets, and the chemical structure of the drug molecules. The temperature of the patch within the delivery process remains in the safe range, and the mild temperature elevation causes color changes of the thermochromic patch, used to indicate effective ultrasound-patch matching. A model delivery patch for pain release is constructed, and animal experiments indicate that the drug blood concentrations are 100% higher than the delivery using only ultrasound and even more remarkably enhanced when compared to only electric-field-motivated delivery or static delivery without external motivations.

A Promising Therapeutic Strategy of Combining Acoustically Stimulated Nanobubbles and Existing Cancer Treatments

In recent years, ultrasound-stimulated microbubbles (USMBs) have gained great attention because of their wide theranostic applications. However, due to their micro-size, reaching the targeted site remains a challenge. At present, ultrasound-stimulated nanobubbles (USNBs) have attracted particular interest, and their small size allows them to extravasate easily in the blood vessels penetrating deeper into the tumor vasculature. Incorporating USNBs with existing cancer therapies such as chemotherapy, immunotherapy, and/or radiation therapy in several preclinical models has been demonstrated to have a profound effect on solid tumors. In this review, we provide an understanding of the composition and formation of nanobubbles (NBs), followed by the recent progress of the therapeutic combinatory effect of USNBs and other cancer therapies in cancer treatment.

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.

Breaking barriers: Innovative approaches for skin delivery of RNA therapeutics

RNA therapeutics represent a rapidly expanding platform with game-changing prospects in personalized medicine. The disruptive potential of this technology will overhaul the standard of care with reference to both primary and specialty care. To date, RNA therapeutics have mostly been delivered parenterally via injection, but topical administration followed by intradermal or transdermal delivery represents an attractive method that is convenient to patients and minimally invasive. The skin barrier, particularly the lipid-rich stratum corneum, presents a significant hurdle to the uptake of large, charged oligonucleotide drugs. Therapeutic oligonucleotides need to be engineered for stability and specificity and formulated with state-of-the-art delivery strategies for efficient uptake. This review will cover various passive and active strategies deployed to enhance permeation through the stratum corneum and achieve effective delivery of RNA therapeutics to treat both local skin disorders and systemic diseases. Some strategies to achieve selectivity between local and systemic administration will also be discussed.

Microchanneling and ultrasonic delivery of gold and platinum nanoparticles for selective photothermolysis of sebaceous follicles in the treatment of acne: a pilot study using porcine skin

PURPOSE

Several treatment options for acne vulgaris are limited by their associated adverse effects. An innovative approach involves introducing light-absorbing nanoparticles into sebaceous follicles before destroying the follicles using selective photothermolysis. We aimed to investigate efficient methods for introducing gold and platinum nanoparticles into sebaceous follicles and to identify suitable laser equipment and parameters for the effective destruction of these follicles.

METHODS

We used porcine skin as the experimental model. We compared the efficacies of a thulium laser, ultrasound, and manual massage and evaluated the optimal method for delivering nanoparticles in close proximity to sebaceous follicles. Subsequently, a 1064-nm-wavelength neodymium-doped yttrium aluminum garnet (Nd: YAG) laser was employed to induce selective photothermolysis. We compared different parameters to identify the optimal pulse duration and fluence of the Nd: YAG laser. The extent of penetration and destruction of sebaceous follicles was assessed using hematoxylin and eosin (H&E) staining, and a numerical evaluation was conducted.

RESULTS

H&E staining showed that irradiation with a long-pulsed Nd: YAG laser following a combination of thulium laser and sonophoresis effectively destroyed sebaceous follicles, with destruction rates exceeding 50%. These results were valid with a long pulse duration and a high fluence of the Nd: YAG laser.

CONCLUSION

This study demonstrated that sebaceous follicles can be effectively destroyed through a mixture of gold and platinum nanoparticle delivery by a combination of microchanneling and sonophoresis, followed by selective thermal damage induced by a 1064-nm long-pulsed high-fluence Nd: YAG laser.

A Systematic Study on Long-acting Nanobubbles: Current Advancement and Prospects on Theranostic Properties

Delivery of diagnostic drugs via nanobubbles (NBs) has shown to be an emerging field of study. Due to their small size, NBs may more easily travel through constricted blood vessels and precisely target certain bodily parts. NB is considered the major treatment for cancer treatment and other diseases which are difficult to diagnose. The field of NBs is dynamic and continues to grow as researchers discover new properties and seek practical applications in various fields. The predominant usage of NBs in novel drug delivery is to enhance the bioavailability, and controlled drug release along with imaging properties NBs are important because they may change interfacial characteristics including surface force, lubrication, and absorption. The quick diffusion of gas into the water was caused by a hypothetical film that was stimulated and punctured by a strong acting force at the gas/water contact of the bubble. In this article, various prominent aspects of NBs have been discussed, along with the long-acting nature, and the theranostical aspect which elucidates the potential marketed drugs along with clinical trial products. The article also covers quality by design aspects, different production techniques that enable method-specific therapeutic applications, increasing the floating time of the bubble, and refining its properties to enhance the prepared NB's quality. NB containing both analysis and curing properties makes it special from other nano-carriers. This work includes all the possible methods of preparing NB, its application, all marketed drugs, and products in clinical trials.

Advancements in Skin-Mediated Drug Delivery: Mechanisms, Techniques, and Applications

Skin-mediated drug delivery methods currently are receiving significant attention as a promising approach for the enhanced delivery of drugs through the skin. Skin-mediated drug delivery offers the potential to overcome the limitations of traditional drug delivery methods, including oral administration and intravenous injection. The challenges associated with drug permeation through layers of skin, which act as a major barrier, are explored, and strategies to overcome these limitations are discussed in detail. This review categorizes skin-mediated drug delivery methods based on the means of increasing drug permeation, and it provides a comprehensive overview of the mechanisms and techniques associated with these methods. In addition, recent advancements in the application of skin-mediated drug delivery are presented. The review also outlines the limitations of ongoing research and suggests future perspectives of studies regarding the skin-mediated delivery of drugs.

Low-frequency ultrasound for pulmonary hypertension therapy

BACKGROUND

Currently, there are no reliable clinical tools that allow non-invasive therapeutic support for patients with pulmonary arterial hypertension. This study aims to propose a low-frequency ultrasound device for pulmonary hypertension therapy and to demonstrate its potential.

METHODS

A novel low-frequency ultrasound transducer has been developed. Due to its structural properties, it is excited by higher vibrational modes, which generate a signal capable of deeply penetrating biological tissues. A methodology for the artificial induction of pulmonary hypertension in sheep and for the assessment of lung physiological parameters such as blood oxygen concentration, pulse rate, and pulmonary blood pressure has been proposed.

RESULTS

The results showed that exposure of the lungs to low-frequency ultrasound changed physiological parameters such as blood oxygen concentration, pulse rate and blood pressure. These parameters are most closely related to indicators of pulmonary hypertension (PH). The ultrasound exposure increased blood oxygen concentration over a 7-min period, while pulse rate and pulmonary blood pressure decreased over the same period. In anaesthetised sheep exposed to low-frequency ultrasound, a 10% increase in SpO2, a 10% decrease in pulse rate and an approximate 13% decrease in blood pressure were observed within 7 min.

CONCLUSIONS

The research findings demonstrate the therapeutic efficiency of low-frequency ultrasound on hypertensive lungs, while also revealing insights into the physiological aspects of gas exchange within the pulmonary system.

Current evidence for non-pharmaceutical, non-surgical treatments of canine osteoarthritis

Osteoarthritis is a progressive degenerative disease process that affects a significant proportion of the canine population, impacting these animals' quality of life. Currently, there is no cure and treatment consists of managing the clinical signs of pain and reduced mobility. There are many treatments for canine osteoarthritis and in this review we discuss the evidence base behind non-pharmaceutical, non-surgical treatments of this disease. These treatments include weight management, nutraceuticals, acupuncture, physiotherapies such as therapeutic exercise, hydrotherapy as well as other therapeutic modalities including photobiomodulation therapy, electromagnetic field therapy and others.

Sonosensitive Cavitation Nuclei-A Customisable Platform Technology for Enhanced Therapeutic Delivery

Ultrasound-mediated cavitation shows great promise for improving targeted drug delivery across a range of clinical applications. Cavitation nuclei-sound-sensitive constructs that enhance cavitation activity at lower pressures-have become a powerful adjuvant to ultrasound-based treatments, and more recently emerged as a drug delivery vehicle in their own right. The unique combination of physical, biological, and chemical effects that occur around these structures, as well as their varied compositions and morphologies, make cavitation nuclei an attractive platform for creating delivery systems tuned to particular therapeutics. In this review, we describe the structure and function of cavitation nuclei, approaches to their functionalization and customization, various clinical applications, progress toward real-world translation, and future directions for the field.

A Conformable Ultrasound Patch for Cavitation-Enhanced Transdermal Cosmeceutical Delivery

Increased consumer interest in healthy-looking skin demands a safe and effective method to increase transdermal absorption of innovative therapeutic cosmeceuticals. However, permeation of small-molecule drugs is limited by the innate barrier function of the stratum corneum. Here, a conformable ultrasound patch (cUSP) that enhances transdermal transport of niacinamide by inducing intermediate-frequency sonophoresis in the fluid coupling medium between the patch and the skin is reported. The cUSP consists of piezoelectric transducers embedded in a soft elastomer to create localized cavitation pockets (0.8 cm² , 1 mm deep) over larger areas of conformal contact (20 cm² ). Multiphysics simulation models, acoustic spectrum analysis, and high-speed videography are used to characterize transducer deflection, acoustic pressure fields, and resulting cavitation bubble dynamics in the coupling medium. The final system demonstrates a 26.2-fold enhancement in niacinamide transport in a porcine model in vitro with a 10 min ultrasound application, demonstrating the suitability of the device for short-exposure, large-area application of sonophoresis for patients and consumers suffering from skin conditions and premature skin aging.

Research progress of physical transdermal enhancement techniques in tumor therapy

The advancement and popularity of transdermal drug delivery (TDD) based on the physical transdermal enhancement technique (PTET) has opened a new paradigm for local tumor treatment. The drug can be directly delivered to the tumor site through the skin, thus avoiding the toxic side effects caused by the first-pass effect and achieving high patient compliance. Further development of PTETs has provided many options for antitumor drugs and laid the foundation for future applications of wearable closed-loop targeting drug delivery systems. In this highlight, the different types of PTETs and related mechanisms, and applications of PTET-related tumor detection and therapy are highlighted. According to their type and characteristics, PTETs are categorized as follows: (1) iontophoresis, (2) electroporation, (3) ultrasound, (4) thermal ablation, and (5) microneedles. PTET-related applications in the local treatment of tumors are categorized as follows: (1) melanoma, (2) breast tumor, (3) squamous cell carcinoma, (4) cervical tumor, and (5) others. The challenges and future prospects of existing PTETs are also discussed. This highlight will provide guidance for the design of PTET-based wearable closed-loop targeting drug delivery systems and personalized therapy for tumors.

Systematic Review of Complementary and Alternative Veterinary Medicine in Sport and Companion Animals: Therapeutic Ultrasound

BACKGROUND

To explore the scientific evidence for therapeutic ultrasound (TU), we conducted a systematic review of the literature on TU in dogs, horses, donkeys, and cats.

METHODS

In three major databases, relevant articles published in 1980-2020 were identified. The risk of bias in each article was evaluated.

RESULTS

Twenty-four relevant articles on the effects of TU in dogs, nine in horses, two in donkeys, and one in cats were identified. TU usually involved 2-6 treatments weekly for up to 4 weeks. Articles on tendon, ligament, and bone healing, acute aseptic arthritis, osteoarthritis, paraparesis, hindquarter weakness, and back muscle pain were identified. In experimental bone lesions in dogs, there is moderate scientific evidence for enhanced healing. For the treatment of other musculoskeletal conditions, the scientific evidence is insufficient due to the high risk of bias. There is substantial evidence that continuous TU increases tissue temperature in muscles and tendons by up to 5 °C in healthy animals. For disorders in tendons, ligaments, muscles, and joints in sport and companion animals, there is insufficient evidence for the clinical effects of TU.

Sonophoresis with ultrasound-responsive liquid-core nuclei for transdermal drug delivery

BACKGROUND

Sonophoresis can increase the delivery efficiency of various drugs into the skin. A recent advance in sonophoresis is the use of ultrasound-responsive liquid-core nuclei (URLN) to increase the probability of cavitation. In this study, we developed a URLN and ultrasound device, and demonstrated its effectiveness through in vitro and clinical tests.

MATERIALS AND METHODS

Three types of experiments were designed to evaluate the efficiency of sonophoresis with URLN. First, a Franz diffusion cell with cosmetic ingredients was used to analyze quantitatively the amount of drug delivered to the porcine skin. Second, after the application of sonophoresis with URLN, the porcine skin surface was examined using scanning electron microscopy (SEM) to see the changes in morphology. Finally, a clinical test was performed to verify the utility of sonophoresis with URLN.

RESULTS

The results indicate that sonophoresis with URLN can increase the amount of compound delivered by approximately 11.9-fold over 6 h for niacinamide and by 7.33-fold over 6 h for adenosine. In addition, we observed approximately 20-30 μm sized pores on porcine skin in SEM images. In clinical testing, the application of sonophoresis with cosmetics containing URLN for 3 min improved the efficiency of transdermal drug delivery by 1.9-fold, the depth of absorption by 2.0-fold, and the speed of absorption by 2.0-fold at 30 min after application.

CONCLUSION

We expect that sonophoresis with specialized URLN in transdermal drug delivery could be used widely for various skin-related applications.

Effect of air pockets in drug delivery via jet injections

Needle-free jet injections are actuated by a pressure impulse that can be delivered by different mechanisms to generate high-speed jets (V_j~O10² m/s). During filling and transportation of disposable cartridges and ampoules, bubbles can form, which can be problematic especially for viscous fluids. Here, we report on the effect of location and size of entrapped air pockets in cartridges used in spring-powered jet injections. As air bubbles pass through the orifice, they undergo depressurization, which results in intermittent atomization and spray formation, temporarily increasing the jet dispersion. Atomization and dispersion of the jet can lead to product loss during an injection. We find that the effect of bubble location on the jet exit speed, delivery efficiency, and the projected area of the blebs formed after the injection was statistically significant (p<0.05). The findings of this study have implications for the development of pre-filled cartridges for jet injection applications.

Wearable patch delivery system for artificial pancreas health diagnostic-therapeutic application: A review

The advanced stimuli-responsive approaches for on-demand drug delivery systems have received tremendous attention as they have great potential to be integrated with sensing and multi-functional electronics on a flexible and stretchable single platform (all-in-one concept) in order to develop skin-integration with close-loop sensation for personalized diagnostic and therapeutic application. The wearable patch pumps have evolved from reservoir-based to matrix patch and drug-in-adhesive (single-layer or multi-layer) type. In this review, we presented the basic requirements of an artificial pancreas, surveyed the design and technologies used in commercial patch pumps available on the market and provided general information about the latest wearable patch pump. We summarized the various advanced delivery strategies with their mechanisms that have been developed to date and representative examples. Mechanical, electrical, light, thermal, acoustic and glucose-responsive approaches on patch form have been successfully utilized in the controllable transdermal drug delivery manner. We highlighted key challenges associated with wearable transdermal delivery systems, their research direction and future development trends.

Characterization of focused ultrasound-mediated brainstem delivery of intranasally administered agents

Focused ultrasound-mediated intranasal (FUSIN) delivery is a recently proposed technique that bypasses the blood-brain barrier to achieve noninvasive and localized brain drug delivery. The goal of this study was to characterize FUSIN drug delivery outcome in mice with regard to its dependency on several critical experimental factors, including the time interval between IN administration and FUS sonication (Tlag1), the FUS pressure, and the time for sacrificing the mice post-FUS (Tlag2). Wild-type mice were treated by FUSIN delivery of near-infrared fluorescent dye-labeled bovine serum albumin (800CW-BSA, used as a model agent). 800CW-BSA was intranasally administered to the mice in vivo, followed by intravenous injection of microbubbles and FUS sonication at the brainstem. Fluorescence imaging of ex vivo mouse brain slices was used to quantify the delivery outcomes of 800CW-BSA. Major organs, along with the nasal tissue and trigeminal nerve, were harvested to assess the biodistribution of 800CW-BSA. The delivery outcome of 800CW-BSA was the highest at the brainstem when Tlag1 was 0.5 h, which was on average 24.5-fold, 5.4-fold, and 21.6-fold higher than those of the IN only, Tlag1 = 1.5 h, and Tlag1 = 4.0 h, respectively. The FUSIN delivery outcome at the lowest pressure level, 0.43 MPa, was on average 1.8-fold and 3.7-fold higher than those at 0.56 MPa and 0.70 MPa, respectively. The mean concentration of 800CW-BSA in the brainstem after FUSIN delivery decreased from 0.5 h to 4.0 h post-FUS. The accumulation of 800CW-BSA was low in the heart, lung, spleen, kidneys, and liver, but high in the stomach and intestines. This study revealed the unique characteristics of FUSIN as a noninvasive, efficient, and localized brain drug delivery technique.

Stability of Engineered Micro or Nanobubbles for Biomedical Applications

A micro/nanobubble (MNB) refers to a bubble structure sized in a micrometer or nanometer scale, in which the core is separated from the external environment and is normally made of gas. Recently, it has been confirmed that MNBs can be widely used in angiography, drug delivery, and treatment. Thus, MNBs are attracting attention as they are capable of constructing a new contrast agent or drug delivery system. Additionally, in order to effectively use an MNB, the method of securing its stability is also being studied. This review highlights the factors affecting the stability of an MNB and the stability of the MNB within the ultrasonic field. It also discusses the relationship between the stability of the bubble and its applicability in vivo.

Damage characteristics and surface description of near-wall materials subjected to ultrasonic cavitation

For the analysis of ultrasonic cavitation erosion on the surface of materials, the ultrasonic cavitation erosion experiments for AlCu4Mg1 and Ti6Al4V were carried out, and the changes of surface topography, surface roughness, and Vickers hardness were explored. Cavitation pits gradually expand and deepen with the increase of experiment time, and Ti6Al4V is more difficult to erode by cavitation than AlCu4Mg1. After experiments, the cavitation damage characteristics such as the single pit, the rainbow ring area, the fisheye pit, and some small pits were observed, which can be considered to be induced by a single micro-jet impact, ablation effect caused by the high temperature, micro-jet impingement with a sharp angle, and multibeam micro-jets coupling impact or negative pressure in the local area produced by micro-jet impact, respectively. The surface roughness and Vickers hardness of the material increase slowly after rapid growth at different points in time as the experiment time increases. With the increase of the ultrasonic amplitude, both of them first increase and then decrease after the ultrasonic amplitude is greater than 10.8 μm. The increases in surface roughness and Vickers hardness tend to decrease as the viscosity coefficient increases. Ultrasonic cavitation can cause submicron surface roughness and increase surface hardness by 20.36%, so it can be used as a surface treatment method.

Clinical and Microbiological Effects of Weekly Supragingival Irrigation with Aerosolized 0.5% Hydrogen Peroxide and Formation of Cavitation Bubbles in Gingival Tissues after This Irrigation: A Six-Month Randomized Clinical Trial

Introduction

The study investigated the effect of weekly supragingival irrigation with aerosolized 0.5% hydrogen peroxide (H₂O₂) solution as a maintenance periodontal therapy on clinical and microbiological parameters in patients with chronic periodontitis. The other purpose was to investigate whether cavitation bubbles can penetrate not only into periodontitis-damaged tissues but also into ex vivo porcine healthy periodontal tissues.

Materials and Methods

The study included 35 systemically healthy patients with chronic periodontitis (CP). After nonsurgical periodontal debridement (NSPD), all patients were randomized into two groups: the Control group (NSDP alone, n = 18) and the Test group (NSDP plus supragingival irrigation, n = 17). Clinical (Approximal Plaque Index (API), Bleeding Index (BI), and Modified Gingival Index (MGI)) and microbiological (Polymerase Chain Reaction technology (using a micro-IDent® kit)) measurements were performed at the initial time point, 3 months, and 6 months after NSPD. The impact of supragingival irrigation on diseased gingival tissues of CP patients (n = 5) and on ex vivo porcine healthy gingival tissue samples (n = 3) was evaluated to estimate morphological changes in healthy and diseased gingival tissues.

Results

Morphological data revealed that supragingival irrigation caused the formation of cavitation bubbles in diseased gingival tissue of CP patients and in healthy porcine gingival tissues. The decrease in API, BI, and MGI scores after 6 months in the Test group significantly (p ≤ 0.01, p ≤ 0.05, and p ≤ 0.01, respectively) exceeded that in the Control group. Test group patients demonstrated a decrease in periodontal sites showing Pocket Probing Depth > 4 mm and, after 6 months, a statistically significant decrease in the proportion of periopathogenic bacteria.

Conclusion

The effectiveness of mechanical periodontal treatment combined with weekly supragingival irrigation with aerosolized 0.5% H₂O₂ solution on clinical and microbiological parameters of periodontal tissues of periodontitis patients is reliably higher than that of mechanical periodontal debridement alone. It has been found that cavitation bubbles as a result of irrigation with the aerosolized 0.5% hydrogen peroxide solution can form not only in periodontal tissues of periodontitis patients but also in ex vivo porcine healthy gingival tissues.

Ultrasound-mediated topical delivery of econazole nitrate with potential for treating Raynaud's phenomenon

The study aims to assess the ultrasound-assisted econazole nitrate (EN) permeation from topically applied formulations with potential for treating Raynaud's phenomenon. Optimization of ultrasound parameters such as the distance of the horn, application time and amplitude were performed. In vitro percutaneous absorption studies were performed using econazole formulations (F2_HPMC dispersion, F4_Lipoderm® Activemax™ Cream) across the ultrasound-treated porcine skin and were compared with the control group (skin samples without ultrasound). Histology and ATR-FTIR studies were performed on treated skin samples. A constant frequency (20 kHz) ultrasound application with 40% amplitude, 0.5 cm distance between ultrasound horn and the skin surface for 2 min was optimized. The permeation of EN was found to be higher from ultrasound-treated skin samples than the control group. Drug permeation from F2_HPMC dispersion was found to be higher as compared to the other formulations and the marketed EN cream. Histological evaluation confirmed that F2_HPMC dispersion showed no signs of toxicity. ATR-FTIR studies revealed a slight increase in the CH₂ stretching vibrations (~2920 cm^-1 and 2850 cm^-1) in ultrasound-treated skin samples as compared with the control. In conclusion, the ultrasound-assisted transdermal delivery of F2_HPMC dispersion could be further studied as a new therapy for Raynaud's phenomenon.

Effect of Ultrasound Intensity and Mode on Piroxicam Transport Across Three-Dimensional Skin Equivalent Epiderm™

BACKGROUND

Transdermal drug delivery has many advantages compared to other routes. However, the barrier function of the stratum corneum limits the use of the skin as an administrative route for medications. Different methods were investigated to alter the barrier function of the stratum corneum and it was found that applying different ultrasound waves could enhance the skin's permeability.

OBJECTIVE

The aim of this work is to study the effect of ultrasonic waves on the alteration of skin natural barrier function, to improve the permeability of the skin to Piroxicam using three-dimension skin (EpiDermTM) as a skin model for the investigation.

METHOD

The effect of ultrasound at 1 MHz and 20 kHz on the permeation of Piroxicam across the three-dimensional skin equivalent using a Franz diffusion cell, was evaluated and the concentration of Piroxicam in the receiving compartment was determined using liquid chromatography method.

RESULTS

The permeation of Piroxicam enhanced by 199% when therapeutic ultrasound at 1 MHz frequency was used. Significant permeation enhancement was also found upon utilizing low frequency sonophoresis at 20 kHz (427%) with no apparent damage to the membrane.

CONCLUSION

Sonophoresis has a positive effect on enhancing skin permeability. The enhancement level was largely dependent on the sonication factors; frequency, intensity and length of treatment. Multiple mechanisms of action might be involved in permeation improvement of the piroxicam molecule. Those mechanisms are largely dependent on the ultrasonic conditions.

Advances in Ultrasound Mediated Transdermal Drug Delivery

Low frequency ultrasound-assisted drug delivery has been widely investigated as a non-invasive method to enhance the transdermal penetration of drugs. Using this technique, a brief application of ultrasound is used to permeabilize skin for a prolonged time. In this review, an overview on ultrasound is detailed to help explain the parameters that could be modulated to obtain the desired ultrasound parameters for enhanced transdermal drug delivery. The mechanisms of enhancement and the latest developments in the area of ultrasound-assisted transdermal drug delivery are discussed. Special emphasis is placed on the effects of ultrasound when used in combination with microneedles, electroporation and iontophoresis, and penetration enhancers. Further, this review summarizes the effect of ultrasound on skin integrity and the regulatory requirements for commercialization of the ultrasound based transdermal delivery instruments.

Circulation Cooling in Continuous Skin Sonoporation at Constant Coupling Fluid Temperatures

Exposure of the skin to low-frequency ultrasound in the Franz diffusion cell has been found to increase the permeability of the skin to molecular transport. In many cases, significant heating of the coupling fluid requires the use of duty cycles that extend the total experimental time. This is a methodological study in which the coupling fluid is circulated between a modified Franz diffusion cell and a heat exchanger to allow for the continuous application of low-frequency ultrasound while the coupling fluid temperature is held constant. Dermatomed porcine skin was exposed to continuous ultrasound at 20 kHz for 10 min at an intensity of 55 W/cm² while the coupling fluid was maintained at one of three target temperatures (13°C, 33°C or 46°C). Foil pitting and passive cavitation detection revealed that inertial cavitation activity decreased with increasing coupling fluid target temperature. Transport measurements revealed an increase in mean donor calcein concentration with increasing coupling fluid temperature, though these were not statistically significant. Taken together these findings suggest that the weakened stratum corneum lipid structure at higher temperatures is more susceptible to the introduction of defects from the jetting of cavitation.

Nano-Enhanced Drug Delivery and Therapeutic Ultrasound for Cancer Treatment and Beyond

While ultrasound is most widely known for its use in diagnostic imaging, the energy carried by ultrasound waves can be utilized to influence cell function and drug delivery. Consequently, our ability to use ultrasound energy at a given intensity unlocks the opportunity to use the ultrasound for therapeutic applications. Indeed, in the last decade ultrasound-based therapies have emerged with promising treatment modalities for several medical conditions. More recently, ultrasound in combination with nanomedicines, i.e., nanoparticles, has been shown to have substantial potential to enhance the efficacy of many treatments including cancer, Alzheimer disease or osteoarthritis. The concept of ultrasound combined with drug delivery is still in its infancy and more research is needed to unfold the mechanisms and interactions of ultrasound with different nanoparticles types and with various cell types. Here we present the state-of-art in ultrasound and ultrasound-assisted drug delivery with a particular focus on cancer treatments. Notably, this review discusses the application of high intensity focus ultrasound for non-invasive tumor ablation and immunomodulatory effects of ultrasound, as well as the efficacy of nanoparticle-enhanced ultrasound therapies for different medical conditions. Furthermore, this review presents safety considerations related to ultrasound technology and gives recommendations in the context of system design and operation.

Monitoring the topical delivery of ultrasmall gold nanoparticles using optical coherence tomography

BACKGROUND

Optical coherence tomography (OCT) is a promising imaging modality for skin cancer diagnosis. However, this capability has been hindered by the low contrast between normal and neoplastic tissue. To overcome this limitation, gold nanoparticles have been used to enhance the contrast in OCT images and are topically administered to reduce the risk of systematic side effects associated with intravenous injection. To ensure efficient penetration and distribution of the nanoparticles, an enhanced delivery strategy is required. In this porcine study, we assessed two delivery methods: (a) using dimethyl sulfoxide (DMSO) and (b) via sonophoresis.

MATERIALS AND METHODS

The gold nanoparticles were topically applied on pig skin before evaluating DMSO and sonophoresis as penetration enhancers in topical administration. The OCT images were taken from the same locations to monitor signal change.

CONCLUSION

The combination of DMSO and sonophoresis is an effective method to enhance the penetration and diffusion rate of nanoparticles during topical administration.

SIGNIFICANCE

Topical administration of nanoparticles is advantageous in dermatological applications. Nevertheless, efficient topical delivery remains a challenge. DMSO and sonophoresis can be used as two effective approaches to enhance topical delivery of nanoparticles.

Progress in ultrasonic oil-contaminated sand cleaning: a fundamental review

Steady efforts in using ultrasonic energy to treat oil-contaminated sand started in the early 2000s until today, although pilot studies on the area can be traced to even earlier dates. Owing to the unique characteristics of the acoustic means, the separation of oil from sand has been showing good results in laboratories. This review provides the compilation of researches and insights into the mechanism of separation thus far. Related topics in the areas of oil-contaminated sand characterizations, fundamental ultrasonic cleaning, and cavitation effects are also addressed. Nevertheless, many of the documented works are only at laboratory or pilot-scale level, and the comprehensive interaction between ultrasonic parameters towards cleaning efficiencies may not have been fully unveiled. Gaps and opportunities are also presented at the end of this article.

Study on the tissue clearing process using different agents by Mueller matrix microscope

In this paper, we monitor the in vitro tissue clearing process of mouse dorsal skin immersed into two types of agents using Mueller matrix microscope. By Mueller matrix polar decomposition, we can see that the major difference between polarization changes due to two kinds of agents is the opposite trend of phase retardance with clearing. For the insight of the connection between different agents with the microstructural and optical changes of cleared tissues, we establish various models to mimic the dynamic process of microphysical features of tissues with clearing time. The mechanisms considered include refractive index matching, collagen shrinkage, more orderly fibers and birefringence variation. We compare the experimental results with simulations based on a single mechanism model and a combined model, respectively, which confirms that an individual possible mechanism cannot explain the polarization phenomena due to clearing. Also by simulations of various clearing models involving two possible mechanisms, we can speculate that formamide and saturated sucrose as agents have respective impacts on tissue features and then cause different polarization changes with clearing. Specifically, collagen shrinkage plus birefringence reduction can better explain the tissue cleared by formamide, and refractive index match plus increased birefringence model is likely to be a proper description of tissue cleared by sucrose. Both simulations and experiments also validate the potential of Mueller matrix microscope as a good tool to understand the interaction between clearing agents and tissues.

Methods for Optical Skin Clearing in Molecular Optical Imaging in Dermatology

This short review describes recent progress in using optical clearing (OC) technique in skin studies. Optical clearing is an efficient tool for enhancing the probing depth and data quality in multiphoton microscopy and Raman spectroscopy. Here, we discuss the main mechanisms of OC, its safety, advantages, and limitations. The data on the OC effect on the skin water content are presented. It was demonstrated that 70% glycerol and 100% Omnipaque^TM 300 reduce the water content in the skin. Both OC agents (OCAs) significantly affect the strongly bound and weakly bound water. However, Omnipaque^TM 300 causes considerably less skin dehydration than glycerol. In addition, the results of examination of the OC effect on autofluorescence in two-photon excitation and background fluorescence in Raman scattering at different skin depths are presented. It is shown that Omnipaque^TM 300 is a promising OCA due to its ability to reduce background fluorescence in the upper skin layers. The possibility of multimodal imaging combining optical methods and OC technique is discussed.

Mechanical damage induced by the appearance of rectified bubble growth in a viscoelastic medium during boiling histotripsy exposure

In boiling histotripsy, the presence of a boiling vapour bubble and understanding of its dynamic behaviour are crucially important for the initiation of the tissue fractionation process and for the control of the size of a lesion produced. Whilst many in vivo studies have shown the feasibility of using boiling histotripsy in mechanical fractionation of solid tumours, not much is known about the evolution of a boiling vapour bubble in soft tissue induced by boiling histotripsy. The main objective of this present study is therefore to investigate the formation and dynamic behaviour of a boiling vapour bubble which occurs under boiling histotripsy insonation. Numerical and experimental studies on the bubble dynamics induced in optically transparent tissue-mimicking gel phantoms exposed to the field of a 2.0 MHz High Intensity Focused Ultrasound (HIFU) transducer were performed with a high speed camera. The Gilmore-Zener bubble model coupled with the Khokhlov-Zabolotskaya-Kuznetsov and the Bio-heat Transfer equations was used to simulate bubble dynamics driven by boiling histotripsy waveforms (nonlinear-shocked wave excitation) in a viscoelastic medium as functions of surrounding temperature and of tissue elasticity variations. In vivo animal experiments were also conducted to examine cellular structures around a freshly created lesion in the liver resulting from boiling histotripsy. To the best of our knowledge, this is the first study reporting the numerical and experimental evidence of the appearance of rectified bubble growth in a viscoelastic medium. Accounting for tissue phantom elasticity adds a mechanical constraint on vapour bubble growth, which improves the agreement between the simulation and the experimental results. In addition the numerical calculations showed that the asymmetry in a shockwave and water vapour transport can result in rectified bubble growth which could be responsible for HIFU-induced tissue decellularisation. Strain on liver tissue induced by this radial motion can damage liver tissue while preserving blood vessels.

Transdermal Drug Delivery using a Specialized Cavitation Seed for Ultrasound

GOAL

The Sonophoresis, which utilizes ultrasound for transdermal drug delivery (TDD), can improve the efficiency of drug delivery for a variety of drugs predominantly due to caviation effect. In order to increase the efficacy of sonophoresis, we propose an alternative cavitation seed specialized for sonophoresis, which can be concentrated on the skin surface by gravity adapting perfluorohexane as core.

METHODS

An in vitro and in vivo experiments were conducted to assess the effect of the specialized cavitation seed. High performance liquid chromatography was used for in vitro experiments on porcine skin with ferulic acid and an optical imaging system was used for in vivo experiments on rat model with fluorescein isothiocyanate-dextran (FD, 150 kDa), respecitively.

RESULTS

The amount of ferulic acid delivered by sonophoresis with the proposed cavitation seed was approximately 1,700 times greater than the amount delivered by diffusion. FD could be delivered to a depth of 500 ¼m under the skin, and the average total flux in the region of interest was increased 6.4-fold for the group using sonophoresis with the cavitation seed compared to the group using diffusion.

CONCLUSION

Conclusively, sonophoresis with the proposed cavitation seed demonstrated significant improvement in TDD and the possibility of macromolecule delivery into the skin.

SIGNIFICANCE

This approach has potential to be a main TDD method for variety of applications including medicine and cosmetics.

Electrically and Ultrasonically Enhanced Transdermal Delivery of Methotrexate

In this study, we used sonophoresis and iontophoresis to enhance the in vitro delivery of methotrexate through human cadaver skin. Iontophoresis was applied for 60 min at a 0.4 mA/sq·cm current density, while low-frequency sonophoresis was applied at a 20 kHz frequency (2 min application, and 6.9 W/sq·cm intensity). The treated skin was characterized by dye binding, transepidermal water loss, skin electrical resistance, and skin temperature measurement. Both sonophoresis and iontophoresis resulted in a significant reduction in skin electrical resistance as well as a marked increase in transepidermal water loss value (p < 0.05). Furthermore, the ultrasonic waves resulted in a significant increase in skin temperature (p < 0.05). In permeation studies, the use of iontophoresis led to a significantly higher drug permeability than the untreated group (n = 4, p < 0.05). The skin became markedly more permeable to methotrexate after the treatment by sonophoresis than by iontophoresis (p < 0.01). A synergistic effect for the combined application of sonophoresis and iontophoresis was also observed. Drug distribution in the skin layers revealed a significantly higher level of methotrexate in the sonicated skin than that in iontophoresis and untreated groups. Iontophoresis and low-frequency sonophoresis were found to enhance the transdermal and intradermal delivery of methotrexate in vitro.

Early steps of cryopreservation of day one honeybee (Apis mellifera) embryos treated with low-frequency sonophoresis

Honeybees, major providers of pollination, are endangered in many areas. Embryo cryopreservation may be a very useful tool to maintain their genetic diversity. However, it is complex in insects, because embryos are chill sensitive and are surrounded by two protectant membranes, the chorion and vitelline. These membranes prevent penetration of cryoprotectant in the embryos. This study aimed to test different conditions of embryo preparation before cryopreservation, including low-frequency sonophoresis, a physical method of permeabilization, and passages through cryoprotectant solutions. Apis mellifera ligustica embryos were collected in artificial cell plugs 7.5 h after queens had been caged, in two different seasons (winter, spring) and were then incubated in vitro overnight (16.5 h). Embryos were individually sonicated and then incubated in three cryoprotectant baths (B1 = 10%, B2 = 20% and B3 = 40% of cryoprotectant) and quenched in liquid nitrogen. Artificial cell plugs and in vitro incubation device were efficient in producing future embryos hatching. Embryos stained ruby red with rhodamine B after sonophoresis treatment indicated that low-frequency ultrasound had permeabilized embryos. According to the treatment, different significant hatching rates were obtained after sonophoresis (up to 25%). After three cryoprotectant incubations, best hatching rates were obtained after 10 min in B1 and B2, and 40 s in B3. These results show that sonophoresis is an efficient tool to permeabilize the chorion and vitelline membrane of the day one honeybee embryo allowing a hatching rate of more than 20%. They also show that the season is an important variability factor.

Recent progress in tissue optical clearing for spectroscopic application

This paper aims to review recent progress in optical clearing of the skin and over naturally turbid biological tissues and blood using this technique in vivo and in vitro with multiphoton microscopy, confocal Raman microscopy, confocal microscopy, NIR spectroscopy, optical coherence tomography, and laser speckle contrast imaging. Basic principles of the technique, its safety, advantages and limitations are discussed. The application of optical clearing agent on a tissue allows for controlling the optical properties of tissue. Optical clearing-induced reduction of tissue scattering significantly facilitates the observation of deep-located tissue regions, at the same time improving the resolution and image contrast for a variety of optical imaging methods suitable for clinical applications, such as diagnostics and laser treatment of skin diseases, mucosal tumor imaging, laser disruption of pathological abnormalities, etc.

Efficiency of the combination of physical therapy modalities with topical nonsteroidal anti-inflammatory drugs for treatment of pain in rheumatology

Pain is the most common syndrome in rheumatology. NSAIDs are often used in its treatment. But they have limitations associated with side effects. An advantage of topical drugs and physical factors (electrophoresis, phonophoresis) combination is the use of low doses of the drug and a decrease in time, to achieve a therapeutic effect, reduce the risk of adverse reactions, increase the concentration of the drug in the inflammation focus, prolonged action (creating a drug depot in tissues). Ketoprofen gel (“Artrocol gel”) is one of the representatives of this pharmacological group. Physicochemical properties help ketoprofen to penetrate easily through the skin and create a therapeutic concentration in the underlying tissues. Objective. To assess the effectiveness of ketoprofen gel (“Arthrocol gel”) electrophonophoresis in the treatment of pain in rheumatological patients. Materials and methods. The study was carried out on the basis of Physiotherapy Department of Vinnytsia Regional Clinical Hospital named after M. I. Pirogov. All patients treated according to the unified clinical protocols were divided into experimental group (EG) and control group (CG). Patients of EG (98 persons) underwent electrophonophoresis with ketoprofen gel once a day for a week. In CG (43 persons) ketoprofen gel was used without electrophonophoresis. The intensity of the pain syndrome is monitored using a visual analog scale (VAS) of Huskisson at rest and during movement. A week later, the patient and the doctor evaluated satisfaction with the results of treatment on the scale: not effective, insufficient, satisfactory, good, excellent. Results. There was a persistent decrease in the intensity of pain syndrome in patients of both groups. The VAS scores were lower in the EG starting from the 3rd day of treatment. The intensity of the acute pain syndrome after 1-week treatment at rest (t = 4.71, p < 0.001) and during the movement (t = 3.84,  p < 0.001) more decrease in EG. Satisfaction with the results of treatment was higher in EG.

Effects of Extracorporeal Shock Wave-Mediated Transdermal Local Anesthetic Drug Delivery on Rat Caudal Nerves

Cavitation plays a substantial role in the clinical effects of extracorporeal shock wave therapy (ESWT). It is also generally accepted as a major mechanism in sonophoresis. To identify the enhancing effect of extracorporeal shock wave-mediated transdermal drug delivery, 24 Wistar rats were randomly assigned to four groups: (i) topical application of a eutectic mixture of local anesthetics (EMLA); (ii) 1-MHz ultrasound; (iii) ESWT pre-treatment combined with EMLA application; (iv) ESWT concurrent with EMLA application on rat tails. The degree of anesthesia was assessed using the amplitude and latency of sensory nerve action potentials within 5 min after a 60-min EMLA application. The results indicated that ESWT pre-treatment and concurrent ESWT accelerated the anesthetic effects of the EMLA cream on the tail nerve (p < 0.05). This finding might indicate that shock wave-mediated transdermal drug delivery is possible during the ESWT period.

Temperature and ultrasound sensitive gatekeepers for the controlled release of chemotherapeutic drugs from mesoporous silica nanoparticles

The copolymer chains were grafted onto the mesopores of silica nanoparticles and could act as stimuli responsive ‘smart’ gatekeepers. With the aid of a transdermal delivery route and ultrasound penetration, even malignant sites of internal organs can be set as targets.

Ultrasonic modulation of tissue optical properties in ex vivo porcine skin to improve transmitted transdermal laser intensity

BACKGROUND AND OBJECTIVE

Applications of light-based energy devices involving optical targets within the dermis frequently experience negative side-effects resultant from surface scattering and excess optical absorption by epidermal melanin. As a broadband optical absorber, melanin decreases the efficacy of light-based treatments throughout the ultraviolet, visible, and near-infrared spectra while also generating additional heat within the surface tissue that can lead to inflammation or tissue damage. Consequently, procedures may be performed using greater energy densities to ensure that the target receives a clinically relevant dose of light; however, such practices are limited, as doing so tends to exacerbate the detrimental complications resulting from melanin absorption of treatment light. The technique presented herein represents an alternative method of operation aimed at increasing epidermal energy fluence while mitigating excess absorption by unintended chromophores. The approach involves the application of continuously pulsed ultrasound to modulate the tissue's optical properties and thereby improve light transmission through the epidermis.

MATERIALS AND METHODS

To demonstrate the change in optical properties, pulsed light at a wavelength of 532 nm from a Q-switched Nd:YAG laser was transmitted into 4 mm thick samples of porcine skin, comprised of both epidermal and dermal tissue. The light was transmitted using an optical waveguide, which allowed for an ultrasonic transducer to be incorporated for simultaneous paraxial pulsation in parallel with laser operation. Light transmitted through the tissue was measured by a photodiode attached to an integrating sphere.

RESULTS

Increasing the driving voltage of ultrasonic pulsation resulted in an increase in mean transmitted optical power of up to a factor of 1.742 ± 0.0526 times the control, wherein no ultrasound was applied, after which the optical power increase plateaued to an average amplification factor of 1.733 ± 0.549 times the control.

CONCLUSIONS

The increase implies a reduction in light either back-scattered or absorbed within the tissue, which would allow for a greater proportion of incident energy to be delivered to the clinical target, thereby improving procedural efficacy and potentially reducing the severity of detrimental side-effects. Apparatus Lasers Surg. Med. 49:666-674, 2017. © 2017 Wiley Periodicals, Inc.

Thermal analyses of in vitro low frequency sonophoresis

As a type of transdermal drug delivery method, low frequency sonophoresis (LFS) has been investigated during the last twenty years and is currently being attempted in a clinical setting. However, the safety of low frequency ultrasound on humans has not been completely guaranteed with high-intensity ultrasound. Thermal damage, one of the challenges in the LFS process, e.g., burns, epidermal detachment and necrosis of tissues, hinders its widespread applications. To predict and impede the overheating problems in LFS, an acoustic-flow-thermal finite element method (FEM) based on COMSOL Multiphysics software is proposed in this paper to achieve thermal analyses. The temperature distribution and its rising curves in in vitro LFS are obtained by the FEM method and experimental measurements. Both simulated and experimental maximum temperatures are larger than the safety value (e.g., 42°C on human tissues) when the driving voltage is higher than 40V (5.5W input electric power), which proves that the overheating problem really exists in high-intensity ultrasound. Furthermore, the results show that the calculated temperature rising curves in in vitro LFS correspond to the experimental results, proving the effectiveness of this FEM method. In addition, several potential thermal influence factors have been studied, including a duty ratio and amplitude of the driving voltage, and liquid height in the donor, which may be helpful in restraining the temperature increase to limit thermal damage. According to the calculated and experimental results, the former two factors are sensitive to the rise in temperature, but a small scale of liquid volume increase can enhance the permeation of Calcein without obvious temperature change. Hence, the above factors can be synthetically utilized to restrain the rise in temperature with little sacrifice of permeation ability. So this acoustic-flow-thermal FEM method could be applied to an optimized LFS system design and simulating the thermal analyses of LFS in healthy human body in terms of safe thermal limits.

Effect of Supragingival Irrigation with Aerosolized 0.5% Hydrogen Peroxide on Clinical Periodontal Parameters, Markers of Systemic Inflammation, and Morphology of Gingival Tissues in Patients with Periodontitis

BACKGROUND Various studies have shown that non-surgical periodontal treatment is correlated with reduction in clinical parameters and plasma levels of inflammatory markers. The aim of this study was to evaluate the effect of long-term weekly supragingival irrigations with aerosolized 0.5% hydrogen peroxide as maintenance therapy followed by non-surgical periodontal treatment on clinical parameters, plasma levels of inflammatory markers, and morphological changes in gingival tissues of patients with periodontitis. MATERIAL AND METHODS In total, 43 patients with chronic periodontitis were randomly allocated to long-term maintenance therapy. The patients' periodontal status was assessed using clinical parameters of approximal plaque index, modified gingival index, bleeding index, pocket probing depth, and plasma levels of inflammatory markers (high-sensitivity C-reactive protein and white blood cell count) at baseline and after 1, 2, and 3 years. The morphological status of gingival tissues (immediately after supragingival irrigation) was assessed microscopically. RESULTS Complete data were obtained on 34 patients. A highly statistically significant and consistent reduction was observed in all long-term clinical parameters and plasma levels of inflammatory markers. Morphological data showed abundant spherical bubbles in gingival tissues. CONCLUSIONS 1. The present study showed that non-surgical periodontal treatment with long-term weekly supragingival irrigations with aerosolized 0.5% hydrogen peroxide improved clinical periodontal status and plasma levels of inflammatory markers and may be a promising method in periodontology. 2. We found that supragingival irrigation with aerosolized 0.5% hydrogen peroxide created large numbers of spherical bubbles in gingival tissues.

Sonophoresis Using Ultrasound Contrast Agents: Dependence on Concentration

Sonophoresis can increase skin permeability to various drugs in transdermal drug delivery. Cavitation is recognized as the predominant mechanism of sonophoresis. Recently, a new logical approach to enhance the efficiency of transdermal drug delivery was tried. It is to utilize the engineered microbubble and its resonant frequency for increase of cavitation activity. Actively-induced cavitation with low-intensity ultrasound (less than ~1 MPa) causes disordering of the lipid bilayers and the formation of aqueous channels by stable cavitation which indicates a continuous oscillation of bubbles. Furthermore, the mutual interactions of microbubble determined by concentration of added bubble are also thought to be an important factor for activity of stable cavitation, even in different characteristics of drug. In the present study, we addressed the dependence of ultrasound contrast agent concentration using two types of drug on the efficiency of transdermal drug delivery. Two types of experiment were designed to quantitatively evaluate the efficiency of transdermal drug delivery according to ultrasound contrast agent concentration. First, an experiment of optical clearing using a tissue optical clearing agent was designed to assess the efficiency of sonophoresis with ultrasound contrast agents. Second, a Franz diffusion cell with ferulic acid was used to quantitatively determine the amount of drug delivered to the skin sample by sonophoresis with ultrasound contrast agents. The maximum enhancement ratio of sonophoresis with a concentration of 1:1,000 was approximately 3.1 times greater than that in the ultrasound group without ultrasound contrast agent and approximately 7.5 times greater than that in the control group. These results support our hypothesis that sonophoresis becomes more effective in transdermal drug delivery due to the presence of engineered bubbles, and that the efficiency of transdermal drug delivery using sonophoresis with microbubbles depends on the concentration of microbubbles in case stable cavitation is predominant.

Intraparenchymal ultrasound application and improved distribution of infusate with convection-enhanced delivery in rodent and nonhuman primate brain

OBJECT

Convection-enhanced delivery (CED) is an effective drug delivery method that delivers high concentrations of drugs directly into the targeted lesion beyond the blood-brain barrier. However, the drug distribution attained using CED has not satisfactorily covered the entire targeted lesion in tumors such as glioma. Recently, the efficacy of ultrasound assistance was reported for various drug delivery applications. The authors developed a new ultrasound-facilitated drug delivery (UFD) system that enables the application of ultrasound at the infusion site. The purpose of this study was to demonstrate the efficacy of the UFD system and to examine effective ultrasound profiles.

METHODS

The authors fabricated a steel bar-based device that generates ultrasound and enables infusion of the aqueous drug from one end of the bar. The volume of distribution (Vd) after infusion of 10 ml of 2% Evans blue dye (EBD) into rodent brain was tested with different frequencies and applied voltages: 252 kHz/30 V; 252 kHz/60 V; 524 kHz/13 V; 524 kHz/30 V; and 524 kHz/60 V. In addition, infusion of 5 mM gadopentetate dimeglumine (Gd-DTPA) was tested with 260 kHz/60 V, the distribution of which was evaluated using a 7-T MRI unit. In a nonhuman primate (Macaca fascicularis) study, 300 μl of 1 mM Gd-DTPA/EBD was infused. The final distribution was evaluated using MRI. Two-sample comparisons were made by Student t-test, and 1-way ANOVA was used for multiple comparisons. Significance was set at p < 0.05.

RESULTS

After infusion of 10 μl of EBD into the rat brain using the UFD system, the Vds of EBD in the UFD groups were significantly larger than those of the control group. When a frequency of 252 kHz was applied, the Vd of the group in which 60 V was applied was significantly larger than that of the group in which 30 V was used. When a frequency of 524 kHz was applied, the Vd tended to increase with application of a higher voltage; however, the differences were not significant (1-way ANOVA). The Vd of Gd-DTPA was also significantly larger in the UFD group than in the control group (p < 0.05, Student t-test). The volume of Gd-DTPA in the nonhuman primate used in this study was 1209.8 ± 193.6 mm3. This volume was much larger than that achieved by conventional CED (568.6 ± 141.0 mm3).

CONCLUSIONS

The UFD system facilitated the distribution of EBD and Gd-DTPA more effectively than conventional CED. Lower frequency and higher applied voltage using resonance frequencies might be more effective to enlarge the Vd. The UFD system may provide a new treatment approach for CNS disorders.

Effects of Microbubble Size on Ultrasound-Induced Transdermal Delivery of High-Molecular-Weight Drugs

The transdermal delivery of a wide range of high-molecular-weight drugs is limited by the stratum corneum layer of the epidermis representing a significant barrier to penetration across the skin. This study first determined the different effects of different-size ultrasound (US) contrast agents and microbubbles (MBs) for enhancing the transdermal delivery of high-molecular-weight drugs. The effects of US-mediated different-size (1.4, 2.1, and 3.5 μm) MBs (as a contrast agent) and ascorbyl tetraisopalmitate (VC-IP) on enhancing skin transdermal delivery were demonstrated both in vitro and in vivo. The results indicated that at a power density of 3 W/cm² the penetration depth in group US combined with 3.5-μm MBs and penetrating VC-IP (U+3.5) was 34% and 14% higher than those in groups US combined with 1.4-μm MBs and penetrating VC-IP (U+1.4) and US combined with 2.1-μm MBs and penetrating VC-IP (U+2.1), respectively, for the agarose phantoms, while the corresponding increases for pigskin were 37% and 19%.In terms of the skin permeation of VC-IP, the VC-IP concentration in group U+3.5 was 23% and 10% higher in than those in groups U+1.4 and U+2.1, respectively. The whitening effect (luminosity index) of mice skin in group U+3.5 had increased (significantly) by 28% after 1 week, by 34% after 2 weeks, and tended to stabilize after 3 weeks (45%) in C57BL/6J mice over a 4-week experimental period. The results obtained in this study indicate that combining US with MBs of different sizes can produce different degrees of skin permeability so as to enhance the delivery of VC-IP to inhibit melanogenesis, without damaging the skin in mice.

Influence of sonophoresis and chemical penetration enhancers on percutaneous transport of penbutolol sulfate

The effect of ultrasound and chemical penetration enhancers on transcutaneous flux of penbutolol sulfate across split-thickness porcine skin was investigated. Penbutolol sulfate is a potent, noncardioselective beta-blocker, which is used for the management of hypertension. The drug is one of the most lipid soluble of the β-adrenoceptor antagonists used clinically. It has an n-octanol/pH 7.4 buffer partition coefficient of 179 compared to a value of 22 for propranolol. The amount of penbutolol sulfate transported across the skin is low. In this project, we studied the effect of sonophoresis and chemical penetration enhancers on transdermal delivery of penbutolol sulfate. Low-frequency sonophoresis at a frequency of 20 kHz increased transcutaneous flux of penbutolol sulfate by 3.5-fold (27.37 ± μg cm^-2 h^-1) compared to passive delivery (7.82 ± 1.72 μg cm^-2 h^-1). We also investigated the effect of 50% ethanol, 1% limonene and 2% isopropyl myristate (IPM) on transcutaneous permeation of penbutolol sulfate. IPM, ethanol and limonene at the concentration of 1%, 50% and 2%, respectively, increased the steady-state flux values of penbutolol sulfate 2.2- (17.07 ± 3.24 μg cm^-2 h^-1), 2.6 - (19.40 ± 6.40 μg cm^-2 h^-1) and 3.4-times (26.38 ± 5.01 μg cm^-2 h^-1) compared to passive delivery (7.76 ± 2.9 μg cm^-2 h^-1). The results demonstrate that although there were slight increases in flux values, ultrasound, ethanol, limonene and IPM did not significantly enhance the transdermal delivery of penbutolol sulfate. Future studies will examine ways of optimizing sonophoretic and chemical enhancer parameters to achieve flux enhancement.