Emerging technologies in therapeutic ultrasound: Thermal ablation to gene delivery

Ultrasound is used today in medicine as a modality for diagnostic imaging. Recently, there have been numerous reports on the application of thermal and nonthermal ultrasound energy for treating various diseases. In addition to thermal ablation of tumors, non-thermal ultrasound combined with drugs and genes have led to much excitement especially for cancer treatment, vascular diseases, and regenerative medicine. Ultrasound energy can enhance the effects of thrombolytic agents such as urokinase for treatment of stroke and acute myocardial infarction. New ultrasound technologies have resulted in advanced devices such as a) ultrasound catheters, b) Non-invasive methods as high intensity focused ultrasound (HIFU) in conjunction with MRI and CT is already being applied in the clinical field, c) Chemical activation of drugs by ultrasound energy for treatment of tumors is another new field recently termed “Sonodynamic Thew”, and d) Combination of genes and microbubble have induced great hopes for ideal gene therapy (sonoporation). Various examples of ultrasound combined modalities are under investigation which could lead to revolutionary therapy.     

Ultrasonic therapy: physiological basis and clinical application

Ultrasound is a relatively new but fairly well accepted physical modality. Therapeutically, ultrasonic energy is employed empirically, but the present trend is to utilize low and medium intensities, 0.5 to 2.0 watts per square centimeter, rather than high intensities, over 2.0 watts per square centimeter, for medical purposes. The important physiological effects of ultrasonic energy on living tissue are thermal, mechanical, chemical and biological. Which one of these effects is dominant is not clearly understood. However, the intensity of the ultrasound field and the duration of application determines the extent to which the thermal or the mechanical effect prevails. From a clinical point of view ultrasonic energy has been most effective in the treatment of painful conditions involving the musculoskeletal and neuromuscular structures. More recently, studies have been directed toward the use of ultrasound as a neurosurgical tool.     

ULTRASONIC THERAPY—Physiological Basis and Clinical Application

Ultrasound is a relatively new but fairly well accepted physical modality. Therapeutically, ultrasonic energy is employed empirically, but the present trend is to utilize low and medium intensities, 0.5 to 2.0 watts per square centimeter, rather than high intensities, over 2.0 watts per square centimeter, for medical purposes.The important physiological effects of ultrasonic energy on living tissue are thermal, mechanical, chemical and biological. Which one of these effects is dominant is not clearly understood. However, the intensity of the ultrasound field and the duration of application determines the extent to which the thermal or the mechanical effect prevails.From a clinical point of view ultrasonic energy has been most effective in the treatment of painful conditions involving the musculoskeletal and neuromuscular structures. More recently, studies have been directed toward the use of ultrasound as a neurosurgical tool.     

Assisted ultrasound applications for the production of safe foods

Ultrasound requires high power and longer treatment times to inactivate micro‐organisms when compared to ultrasound combined with other technologies. Previous reports have shown that the effectiveness of ultrasound as a decontamination technology can be increased by combining it with another treatment such as pressure, heat and antimicrobial solutions. Assisted ultrasound, the combination of ultrasound with another technology, is more energy efficient, and it has less impact on the food properties. In this review paper, the power ultrasound antimicrobial mechanisms of action, the antimicrobial effects of ultrasound in combination with other physical processes and antimicrobial solutions are comprehensively discussed. Furthermore, the present interest on using these technologies as alternative processing and decontamination methods is presented. Research outputs on the application of ultrasound combined with physical processes are showcased including applications of thermosonication, manosonication, manothermosonication and osmosonication. Antimicrobial efficacy, energy requirements and optimal operation conditions of the different assisted ultrasound technologies are critically discussed, and their impact on the food industry for future applications is presented. Overall, this review paper highlights the importance and recent developments of assisted ultrasound for enhancing food safety.     

Spatial and Temporal Control of Hyperthermia Using Real Time Ultrasonic Thermal Strain Imaging with Motion Compensation,Phantom Study

Mild hyperthermia has been successfully employed to induce reversible physiological changes that can directly treat cancer and enhance local drug delivery. In this approach, temperature monitoring is essential to avoid undesirable biological effects that result from thermal damage. For thermal therapies, Magnetic Resonance Imaging (MRI) has been employed to control real-time Focused Ultrasound (FUS) therapies. However, combined ultrasound imaging and therapy systems offer the benefits of simple, low-cost devices that can be broadly applied. To facilitate such technology, ultrasound thermometry has potential to reliably monitor temperature. Control of mild hyperthermia was previously achieved using a proportional-integral-derivative (PID) controller based on thermocouple measurements. Despite accurate temporal control of heating, this method is limited by the single position at which the temperature is measured. Ultrasound thermometry techniques based on exploiting the thermal dependence of acoustic parameters (such as longitudinal velocity) can be extended to create thermal maps and allow an accurate monitoring of temperature with good spatial resolution. However, in vivo applications of this technique have not been fully developed due to the high sensitivity to tissue motion. Here, we propose a motion compensation method based on the acquisition of multiple reference frames prior to treatment. The technique was tested in the presence of 2-D and 3-D physiological-scale motion and was found to provide effective real-time temperature monitoring. PID control of mild hyperthermia in presence of motion was then tested with ultrasound thermometry as feedback and temperature was maintained within 0.3°C of the requested value.     

Grey-Scale Ultrasound in the Imaging of Urinary Tract Disease

Grey-scale ultrasound defines smaller renal lesions that had previously been appreciated and is able to define associated lesions of the liver such as metastases and cysts. The appropriate technique to delineate the normal anatomy of the kidney is described. Ultrasound plays a central role in the identification and characterization of renal mass lesions thus leading to appropriate further work up. In renal transplant evaluation ultrasound is useful as a complementary modality to other imaging studies permitting the recognition of pelvic fluid collections, rejection, and hydronephrosis. Specific findings are present in renal abscess, perirenal abscess, and in several of the renal cystic diseases. Adrenal lesions can be identified and clarified. In the lower urinary tract, ultrasound can identify bladder and prostatic tumors.Ultrasound provides a rapid, safe and non-invasive modality which is complementary to other imaging techniques in the diagnosis of urinary tract disease.     

Ultrasound scatter-spacing based diagnosis of focal diseases of the liver

Ultrasound returns from liver shows periodicity arising from periodic scattering centers within tissue. Focal diseases such as tumors interrupt this structure. In this paper, we propose the use of a wavelet transform based technique to estimate the inter-scatterer-distribution (ISS) in diagnosing focal diaseases of the liver. The efficacy of the method is illustrated with simulated and clinical ultrasound images. The mean value (MSS) of the ISS has been proposed as a signature for focal diseases, but its effectiveness has not been established yet. We show that the ISS distribution may function as a feature to characterize focal diseases even when its mean value MSS fails. The method proposed in this paper works even when data is non-stationary.     

G protein-coupled receptors in energy homeostasis

G-protein coupled receptors (GPCRs) compromise the largest membrane protein superfamily which play vital roles in physiological and pathophysiological processes including energy homeostasis. Moreover, they also represent the up-to-date most successful drug target. The gut hormone GPCRs, such as glucagon receptor and GLP-1 receptor, have been intensively studied for their roles in metabolism and respective drugs have developed for the treatment of metabolic diseases such as type 2 diabetes (T2D). Along with the advances of biomedical research, more GPCRs have been found to play important roles in the regulation of energy homeostasis from nutrient sensing, appetite control to glucose and fatty acid metabolism with various mechanisms. The investigation of their biological functions will not only improve our understanding of how our body keeps the balance of energy intake and expenditure, but also highlight the possible drug targets for the treatment of metabolic diseases. The present review summarizes GPCRs involved in the energy control with special emphasis on their pathophysiological roles in metabolic diseases and hopefully triggers more intensive and systematic investigations in the field so that a comprehensive network control of energy homeostasis will be revealed, and better drugs will be developed in the foreseeable future.     

生物热应变成像技术的研究进展

热应变成像(thermal strain imaging,TSI)是一种利用超声回波时移的温度相关性进行成像的超声应用.它既具有超声安全、无创和实时成像的优点,又能够显示与其他超声成像方式不同的组织特征,具有良好的应用前景.热应变成像目前在生物医学领域主要应用于组织表征和温度监测两个方面.本综述介绍了热应变成像的基本原理,讨论了适用于临床的主要能量源,并通过回顾近几年热应变成像的研究成果和分析目前面临的局限与挑战,对热应变成像技术的发展进行了探讨和展望.     

Ultrasound and microbubble-targeted delivery of therapeutic compounds

The molecular understanding of diseases has been accelerated in recent years, producing many new potential therapeutic targets. A noninvasive delivery system that can target specific anatomical sites would be a great boost for many therapies, particularly those based on manipulation of gene expression. The use of microbubbles controlled by ultrasound as a method for delivery of drugs or genes to specific tissues is promising. It has been shown by our group and others that ultrasound increases cell membrane permeability and enhances uptake of drugs and genes. One of the important mechanisms is that microbubbles act to focus ultrasound energy by lowering the threshold for ultrasound bioeffects. Therefore, clear understanding of the bioeffects and mechanisms underlying the membrane permeability in the presence of microbubbles and ultrasound is of paramount importance. (Neth Heart J 2009;17:82-6.)     

Développement d’un dispositif expérimental ultrasonore pour le largage ciblé et contrôlé d’une chimiothérapie encapsulée

Applying ultrasound on drug-loaded sonosensitive liposomes offers new possibilities for treating cancer. In vitro experiments were performed in the present study to define an index of inertial cavitation which could be used to monitor the delivery of drugs. This index could also be used to assess the sonosensitivity of new formulations of liposomes. Experiments were then carried out in rats bearing subcutaneous abdominal tumors. Based on pharmacokinetic and biodistribution studies, a period of 48 hours was chosen between the injection of the liposomes and the exposure to ultrasound. At the injected doses, liposomes slowed down significantly the tumor development. Ultrasound combined with liposomes seemed to contribute to the tumor control. However, the important efficacy of liposomes alone and the eventual weak interactions with ultrasound prevent to guarantee that the effect of ultrasound is significant.     

Gold nanostructures absorption capacities of various energy forms for thermal therapy applications

This mini-review has investigated the recent progress regarding gold nanostructures capacities of energy absorption for thermal therapy applications. Unselective thermal therapy of malignant and normal tissues could lead to irreversible damage to healthy tissues without effective treatment on target malignant tissues. In recent years, there has been a considerable progress in the field of cancer thermal therapy for treating target malignant tissues using nanostructures. Due to the remarkable physical properties of the gold nanoparticle, it has been considered as an exceptional element for thermal therapy techniques. Different types of gold nanoparticles have been used as energy absorbent for thermal therapy applications under several types of energy exposures. Electromagnetic, ultrasound, electric and magnetic field are examples for these energy sources. Well-known plasmonic photothermal therapy which applies electromagnetic radiation is under clinical investigation for the treatment of various medical conditions. However, there are many other techniques in this regard which should be explored.     

Local drug and gene delivery through microbubbles and ultrasound

Although gene therapy has great potential as a treatment for diseases, clinical trials are slowed down by the development of a safe and efficient gene delivery system. In this review, we will give an overview of the viral and nonviral vehicles used for drug and gene delivery, and the different nonviral delivery techniques, thereby focusing on delivery through ultrasound contrast agents.The development of ultrasound contrast agents containing encapsulated microbubbles has increased the possibilities not only for diagnostic imaging, but for therapy as well. Microbubbles have been shown to be able to carry drugs and genes, and destruction of the bubbles by ultrasound will result in local release of their contents. Furthermore, ligands can be attached so that they can be targeted to a specific target tissue. The recent advances of microbubbles as vehicles for delivery of drugs and genes will be highlighted.     

Transdermal drug delivery

Transdermal drug delivery has made an important contribution to medical practice, but has yet to fully achieve its potential as an alternative to oral delivery and hypodermic injections. First-generation transdermal delivery systems have continued their steady increase in clinical use for delivery of small, lipophilic, low-dose drugs. Second-generation delivery systems using chemical enhancers, noncavitational ultrasound and iontophoresis have also resulted in clinical products; the ability of iontophoresis to control delivery rates in real time provides added functionality. Third-generation delivery systems target their effects to skin's barrier layer of stratum corneum using microneedles, thermal ablation, microdermabrasion, electroporation and cavitational ultrasound. Microneedles and thermal ablation are currently progressing through clinical trials for delivery of macromolecules and vaccines, such as insulin, parathyroid hormone and influenza vaccine. Using these novel second- and third-generation enhancement strategies, transdermal delivery is poised to significantly increase its impact on medicine.     

Perspectives on transdermal ultrasound mediated drug delivery

The use of needles for multiple injection of drugs, such as insulin for diabetes, can be painful. As a result, prescribed drug noncompliance can result in severe medical complications. Several noninvasive methods exist for transdermal drug delivery. These include chemical mediation using liposomes and chemical enhancers or physical mechanisms such as microneedles, iontophoresis, electroporation, and ultrasound. Ultrasound enhanced transdermal drug delivery offers advantages over traditional drug delivery methods which are often invasive and painful. A broad review of the transdermal ultrasound drug delivery literature has shown that this technology offers promising potential for noninvasive drug administration. From a clinical perspective, few drugs, proteins or peptides have been successfully administered transdermally because of the low skin permeability to these relatively large molecules, although much work is underway to resolve this problem. The proposed mechanism of ultrasound has been suggested to be the result of cavitation, which is discussed along with the bioeffects from therapeutic ultrasound. For low frequencies, potential transducers which can be used for drug delivery are discussed, along with cautions regarding ultrasound safety versus efficacy.     

Preliminary Investigation of a 64-element Capacitive Micromachined Ultrasound Transducer (CMUT) Annular Array Designed for High Intensity Focused Ultrasound (HIFU)

Background

Treatment of prostate cancer using endocavitary High Intensity Focused Ultrasound (HIFU) has become more commonplace since the first treatments in the 1990s. The gold standard HIFU strategy to treat prostate cancer is the complete thermal ablation of the entire prostate gland under real-time ultrasound (US) image guidance. A more desirable treatment and the current trend, however, is towards a focal treatment but more accurate and finely tunable thermal lesions are needed along with improved US imaging guidance. In this study, Capacitive Micromachined Ultrasound Transducer (CMUT) technology is being investigated, as they have shown recent promise for US imaging and potential to be used for HIFU therapy. They offer potential advantages over current piezoelectric designs in the context of ultrasound-guided HIFU (USgHIFU) focal therapies.

Determination of free cisplatin in medium by differential pulse polarography after ultrasound and cisplatin treatment of a cancer cell culture

The in vitro study was carried out for detection of the cisplatin in free form and in culture medium, depending on various conditions of sonodynamic human ovarian cancer cells A2780 treatment by differential pulse polarography (DPP). For sonodynamic treatment, we used cisplatin alone and combined cisplatin/ultrasound treatments. The ultrasound exposure intensity of 1.0 and 2.0 W x cm(-2) in far field for incubation periods 1, 24 and 48 h was used. The parameters of DPP measurements were--1 s drop time, 5 mV x s(-1) voltage scan rate, 50 mV modulation amplitude and negative scanning direction; platinum wire served as counter electrode and Ag/AgCl/3 M KCl as reference electrode. The results showed the dependence of free platinum quantities in culture medium on incubation time and treatment protocol. We found difference in concentration of free cisplatin between conventional application of cisplatin and sonodynamic treatment. The sonodynamic combined treatment of cisplatin and ultrasound field showed a higher cisplatin content in the culture medium than cisplatin treatment alone; a difference of 20% was observed for incubation time 48 h. The results also showed the influence of a time sequence of ultrasound and cytostatics in the sonodynamic treatment. The highest amount of free cisplatin in the solution was found for primary application of cisplatin and the subsequent ultrasound exposure. The quantity of free cisplatin increased with time, namely for time intervals 1-24 h. There was no difference between the DPP signal of cisplatin in reaction mixture containing cells in small quantities and micro-filtered mixture without cells. Thus, the DPP method is suitable for the detection and quantification of free cisplatin in the culture medium of cell suspension. Ultrasound field can be important factor during cytostatic therapy.     

Polymalic Acid-based Nano Biopolymers for Targeting of Multiple Tumor Markers: An Opportunity for Personalized Medicine?

Tumors with similar grade and morphology often respond differently to the same treatment because of variations in molecular profiling. To account for this diversity, personalized medicine is developed for silencing malignancy associated genes. Nano drugs fit these needs by targeting tumor and delivering antisense oligonucleotides for silencing of genes. As drugs for the treatment are often administered repeatedly, absence of toxicity and negligible immune response are desirable. In the example presented here, a nano medicine is synthesized from the biodegradable, non-toxic and non-immunogenic platform polymalic acid by controlled chemical ligation of antisense oligonucleotides and tumor targeting molecules. The synthesis and treatment is exemplified for human Her2-positive breast cancer using an experimental mouse model. The case can be translated towards synthesis and treatment of other tumors.     

Degradation of azo dyes by laccase and ultrasound treatment

The goal of this work was to investigate the decomposition of azo dyes by oxidative methods, such as laccase and ultrasound treatments. Each of these methods has strong and feeble sides. The laccase treatment showed high decolorization rates but cannot degrade all investigated dyes (reactive dyes), and high anionic strength led to enzyme deactivation. Ultrasound treatment can decolorize all tested dyes after 3 h at a high energy input, and prolonged sonication leads to nontoxic ionic species, which was demonstrated by ion chromatography and toxicity assays. For the first time, it was shown that a combination of laccase and ultrasound treatments can have synergistic effects, which was shown by higher degradation rates. Bulk light absorption and ion-pairing high-performance liquid chromatography (IP-HPLC) were used for process monitoring, while with reversed-phase HPLC, a lower number of intermediates than expected by IP-HPLC was found. Liquid chromatography-mass spectrometry indicated that both acid orange dyes lead to a common end product due to laccase treatment. Acid Orange 52 is demethylated by laccase and ultrasound treatment. Further results confirmed that the main effect of ultrasound is based on *OH attack on the dye molecules.