超声造影微泡新进展

随着超声造影微泡技术的不断发展和可携带药物超声微泡造影剂的研制,超声微泡在肿瘤的治疗方面取得了进展.我们近年来一直研究关于超声造影剂作为超声导向药物运载系统的用途[1,2]. 1 原理     

超声微泡造影剂介导基因靶向治疗肝细胞癌的研究进展

随着超声造影及微泡制备技术的不断发展,超声微泡造影剂携带基因和药物的靶向治疗成为当前医学领域中的研究热点.利用超声波与微泡造影剂的相互作用及所产生的生物学效应,可实现微泡携带基因向目标组织转移释放,使肿瘤细胞局部目的基因的浓度大大增高,达到靶向治疗目的.     

微泡超声造影剂在临床治疗诊断中的应用

超声造影剂通过改变聚合条件为某种成像条件量身定做的造影剂,从而应用于不同生理和病理状态下及靶向药物的输送。微泡超声造影剂作为靶目标显像、药物载体和基因载体,提高了超声造影的临床诊断水平,同时还可以携带基因及药物进入体内,然后在超声空化作用下释放基因及药物进入细胞内,从而达到一定的治疗作用,并在未来临床治疗中显示出巨大潜力。     

超声微泡介导的基因递送系统应用进展

超声波可聚焦于体内的特定部位。含气体微泡既可以作为医学超声显像的造影剂，又可以作为药物或基因载体。超声微泡有望实现基因的靶向递送，因此成为药物递送系统研究的热门领域。本文阐述了超声微泡介导的基因递送系统在心肌、血管、骨骼肌和肿瘤组织等方面的研究进展，讨论其在未来应用中面临的问题。     

超声诊断或治疗用微/纳泡的研究进展

过去几十年中,微泡作为超声造影剂广泛应用于肿瘤成像领域,随着研究的逐渐深入,超声靶向微泡破坏技术结合载药微泡能够实现药物的精准释放,发挥治疗作用。微泡作为微米级载体难以透过肿瘤内皮细胞间隙,纳米级递药系统——纳泡应运而生,两者结构特征相似,但尺寸上的差异突显出纳泡在药物递送方面独特的优势。本综述以外壳材料为分类原则,对用作超声诊断或治疗的微/纳泡进行归纳总结,并探讨其未来可能的发展方向,为微/纳泡的后续开发提供参考。     

载尿激酶脂质微泡制剂的制备及其理化性质检测

<正>随着超声造影剂的不断发展,超声造影剂在疾病的诊断方面发挥了巨大作用并且在疾病治疗方面也已成为国内外的研究热点。以脂质微泡为载体,将特定的药物、基因与脂质微泡相连接,与超声联用可达到药物在目标组织的富集,从而更好的发挥药物的治疗作用,并减少药物在全身的不良反应。国内外研究已有报道超声可增强溶栓药物的作用[1-3],若能将溶栓药物与微泡相结合将更有助于局部溶栓     

超声介导微泡靶向药物释放的应用研究进展

随着基因治疗学及分子生物学的迅速发展,无创性治疗基因靶向传输技术在不断进步,超声微泡除可广泛应用于疾病的诊断以外,还被证实是一种有效的靶向释放药物和基因载体[1～4].药物与微泡的结合方式有2种:一是直接粘附于微泡外壳;二是与特异性配体结合.     

一种新的药物传递系统——超声微泡剂

目的：探讨超声微泡剂作为药物载体传输药物的机制及临床应用前景。方法：查阅国内外文献，进行归纳总结，分析其作用机制及应用前景。结果：超声微泡剂可作为药物载体，可传输基因和药物，能提高基因的转染率和表达，配合超声处理产生的空化效应可提高细胞膜的通透性，利于药物穿透；并且具有靶向性。因此在基因治疗和抗肿瘤治疗方面有很好的应用前景。结论：随着超声技术和微泡剂制备技术的发展，超声微泡剂必将为临床治疗提供一种安全、高效、无创的超声介导靶向传输及治疗系统。     

超声微泡造影剂与基因转染及临床治疗的研究进展

超声微泡造影剂已应用于基因转染的实验研究中,可促进基因在靶细胞及靶组织转染.在疾病治疗中的作用也日益受到重视,已应用于肿瘤、炎症及血栓等多种疾病.本文主要对各类造影剂成膜材料的研究状况进行介绍,并在基因转染中的应用及临床治疗作一综述.     

超声微泡介导基因转移在骨折创伤愈合中的应用

随着分子生物学的深入研究,基因治疗在医学领域具有广阔的应用前景。超声微泡介导基因转移是将携带有目的基因的微泡造影剂经静脉注射传递到靶组织后,利用超声波在靶区破坏微泡,实现体内局部组织目的基因转移及促进表达的技术。     

高分子聚合物PLGE超声微泡的制备与体外显影研究

目的：应用新型高分子聚合材料聚乳酸/羟基乙酸/聚乙二醇嵌段共聚物（PLGE）制备超声微泡并观察其体外显影效果。方法：采用复乳法（W/O/W）制备超声微泡,使用光镜和扫描电镜观察形态、测定微泡的粒径分布,通过体外溶液超声显影实验观察显影效果。结果：采用该法制备的超声微泡呈球形,粒径分布均匀,平均粒径1.75μm,体外显影效果好。结论：以PLGE为外壳材料,采用复乳法制备的微泡可以作为超声造影剂,为下一步载药研究提供基础。     

含蔗糖白蛋白包膜微泡超声造影剂制备研究

目的　研制一种新型的直径在数微米范围内的含蔗糖白蛋白微泡超声造影剂。方法　以全氟化碳及少量氧气为微泡中的气体介质,用超声空化方法进行微泡制备。研究了蔗糖对白蛋白包膜微泡半衰期、微泡尺寸保持及热稳定性的影响,测定了含40%蔗糖白蛋白包膜微泡的谐波特性等。结果　常温下( 20℃) ,在一定范围内,随着糖的加入及浓度的增加,白蛋白微泡的稳定性不断加强;当糖质量浓度达到40% ,微泡半衰期可延长至50d以上,96%微泡尺寸分布在2 - 5 μm ,常温下保存一月后微泡之间无明显合并现象,同时比未含蔗糖微泡耐热性明显加强,4℃下将制得的微泡保存半年,未观测到微泡数量及尺寸有明显变化,制备出的微泡有较强的非线性特征,在2次谐波上的反射幅度远高于背景散射源及对比金属板。结论　含40%蔗糖的以全氟化碳及少量氧气为气体介质的白蛋白包膜微泡可以成为一种性能优良的超声造影剂。     

Response of contrast agents to ultrasound

Microbubbles are used as ultrasonic contrast agents that enhance the ultrasound signals of the vascular bed. The recent development of site-targeted microbubbles opened up the possibility for molecular imaging as well as localised drug and gene delivery. Initially the microbubbles' physical properties and their response to the ultrasound beam were not fully understood. However, the introduction of fast acquisition microscopy has allowed the observation of the microbubble behaviour in the presence of ultrasound. In addition, acoustical techniques can determine the scatter of single microbubbles. Sonoporation experiments promise high-specificity drug and gene delivery, but the responsible physical mechanisms, particularly for in vivo applications, are not fully understood. An improvement of microbubble technology may address variability related problems in both imaging and drug/gene delivery.     

Vascular gene transfer and drug delivery in vitro using low-frequency ultrasound and microbubbles

Aim:

To determine the effects of ultrasound exposure in combination with a microbubble contrast agent (SonoVue) on the cellular uptake and delivery of drugs/genes into human umbilical vein endothelial cells (HUVECs) as well as their biological effects on migration.

Methods:

HUVECs in suspension were exposed to pulsed ultrasound with a 10% duty cycle in combination with various concentrations of a microbubble contrast agent (SonoVue) using a digital sonifier at a frequency of 20 kHz and an intensity of 3.77 W/cm² on the surface of a horn tip. Cell culture inserts were used to determine the cell migration ability.

Results:

Exposure to pulsed ultrasound resulted in enhanced green fluorescent protein (EGFP) gene transfection efficiencies ranging from 0.2% to 2%. The transfection efficiency of HUVECs was approximately 3-fold higher in the presence of SonoVue than in its absence at the effective exposure time of 6 s. For drug delivery to HUVECs using ultrasound, the delivery efficiencies of a low-molecular-weight model drug (TO-PRO^®−1, M_W 645.38) were significantly higher when compared to drug delivery without ultrasound, with a maximum efficiency of approximately 34%. However, the delivery efficiencies of a high-molecular-weight model drug (Dextran-Rhodamine B, M_W 70 000) were low, with a maximum delivery efficiency of nearly 0.5%, and gene transfection results were similarly poor. The migration ability of HUVECs exposed to ultrasound was also lower than that of the control (no exposure).

Conclusion:

The use of low-frequency and low-energy ultrasound in combination with microbubbles could be a potent physical method of increasing drug/gene delivery efficiency. This technique is a promising nonviral approach that can be used in cardiovascular disease therapy.     

Ultrasound-directed drug delivery

It has been proven, that the cellular uptake of drugs and genes is increased, when the region of interest is under ultrasound insonification, and even more when a contrast agent is present. This increased uptake has been attributed to the formation of transient porosities in the cell membrane, which are big enough for the transport of drugs into the cell (sonoporation). Owing to this technique, new ultrasound contrast agents that incorporate a therapeutic compound have become of interest. Combining ultrasound contrast agents with therapeutic substances, such a chemotherapeutics and virus vectors, may lead to a simple and economic method to instantly cure upon diagnosis, using conventional ultrasound scanners. There are two hypotheses for explaining the sonoporation phenomenon, the first being microbubble oscillations near a cell membrane, the second being microbubble jetting through the cell membrane. Based on modeling, high-speed photography, and recent cellular uptake measurements, it is concluded that microbubble jetting behavior is less likely to be the dominant sonoporation mechanism. Ultrasound-directed drug delivery using microbubbles is a promising method that has great potential in the treatment of malignant disorders.     

Microbubbles as a vehicle for gene and drug delivery: current clinical implications and future perspectives

Ultrasound targeted microbubble destruction (UTMD) has evolved as a novel system for non-invasive, organ- and tissue-specific drug and gene delivery. Initially developed as ultrasound contrast agents, microbubbles (MBs) have increasingly gained attention for their ability to directly deliver different classes of bioactive substances (e.g. genes, drugs, proteins, gene silencing constructs) to various organ systems and tumors. Bioactive substances can be attached to or incorporated in the microbubble shells. Applying ultrasound at their resonance frequency, microbubbles oscillate. When using higher ultrasound energies, oscillation amplitudes increase, finally resulting in microbubble destruction. This leads to increased capillary and cell membrane permeability in the immediate vicinity of the ruptured MBs, thus facilitating tissue and cell penetration of co-administered or loaded bioactive substances. Numerous proof of principle studies have been performed, demonstrating the broad potential of UTMD as a site-specific, non-invasive therapeutic tool, delivering microbubble payload to various target tissues and organ systems or facilitating uptake of bioactive substances into tissues or cells. This review focuses on current in vivo studies and therapeutic approaches of UTMD. Promising results give hope for future clinical applications of this novel non-viral vector system. Nevertheless, several limitations remain, which will also be discussed in this review article.     

Anti-angiogenic gene therapy for hepatocellular carcinoma mediated by microbubble-enhanced ultrasound exposure: An in vivo experimental study

Objective: The aim of this study was to assess the effect of anti-angiogenic gene therapy for hepatocelluar carcinoma (HCC) treated by microbubble-enhanced ultrasound exposure.

Methods: Forty C57BL/6J female mice were inoculated s.c. with Hepa1-6 tumor cell line. Herpes simplex virus thymidine kinase under the control of kinase domain-containing receptor (KDR, angiogenic growth factor's corresponding receptor) promoter was used. Plasmid DNA with or without microbubble contrast agent of SonoVue? was i.v. injected. Ultrasound (1 MHz, 2 W/cm², 5 min) was delivered to hepatic carcinomas in mice. The KDR-tk gene transfer was followed by ganciclovir (GCV) injection for 10 days and then the diameters of tumors were measured every 4 days till 28 days. The survivals of tumor-bearing mice were observed. PCR analysis and immunohistochemistry measurements revealed expression of the transfected gene. Transferase-mediated dUTP nick end labeling staining was used to detect apoptotic cells.

Results: Compared with the group treated by ultrasound alone, KDR-tk gene treatment treated by ultrasound combined with SonoVue restrained tumor growth and increased survival time of tumor-bearing mice; microvessel density in group mediated by ultrasound and SonoVue was significantly lower than that in group ultrasound alone (12.3 ± 1.4 vs. 27.4 ± 3.2, P < 0.05). An apoptosis index increased in the group treated by ultrasound and SonoVue compared with the group treated by ultrasound alone (25 ± 3.6 vs. 36 ± 3.8, P < 0.05), whereas there was no significant difference between group mediated by SonoVue alone and group phosphate-buffered saline alone (17 ± 1.8 vs. 14 ± 1.2, P>0.05).

Conclusions: Gene therapy mediated by ultrasound exposure enhanced by a microbubble contrast agent may become a new treatment option for persistent HCC.     

Ultrasound targeted microbubble destruction for drug and gene delivery

Background: Gas-filled microbubbles have been used as ultrasound contrast agents for some decades. More recently, such microbubbles have evolved as experimental tools for organ- and tissue-specific drug and gene delivery. When sonified with ultrasound near their resonance frequency, microbubbles oscillate. With higher ultrasound energies, oscillation amplitudes increase, leading to microbubble destruction. This phenomenon can be used to deliver a substance into a target organ, if microbubbles are co-administered loaded with drugs or gene therapy vectors before i.v. injection. Objective: This review focuses on different experimental applications of microbubbles as tools for drug and gene delivery. Different organ systems and different classes of bioactive substances that have been used in previous studies will be discussed. Methods: All the available literature was reviewed to highlight the potential of this non-invasive, organ-specific delivery system. Conclusion: Ultrasound targeted microbubble destruction has been used in various organ systems and in tumours to successfully deliver drugs, proteins, gene therapy vectors and gene silencing constructs. Many proof of principle studies have demonstrated its potential as a non-invasive delivery tool. However, too few large animal studies and studies with therapeutic aims have been performed to see a clinical application of this technique in the near future. Nevertheless, there is great hope that preclinical large animal studies will confirm the successful results already obtained in small animals.     

Ultrasound targeted microbubble destruction for drug and gene delivery

Background: Gas-filled microbubbles have been used as ultrasound contrast agents for some decades. More recently, such microbubbles have evolved as experimental tools for organ- and tissue-specific drug and gene delivery. When sonified with ultrasound near their resonance frequency, microbubbles oscillate. With higher ultrasound energies, oscillation amplitudes increase, leading to microbubble destruction. This phenomenon can be used to deliver a substance into a target organ, if microbubbles are co-administered loaded with drugs or gene therapy vectors before i.v. injection. Objective: This review focuses on different experimental applications of microbubbles as tools for drug and gene delivery. Different organ systems and different classes of bioactive substances that have been used in previous studies will be discussed. Methods: All the available literature was reviewed to highlight the potential of this non-invasive, organ-specific delivery system. Conclusion: Ultrasound targeted microbubble destruction has been used in various organ systems and in tumours to successfully deliver drugs, proteins, gene therapy vectors and gene silencing constructs. Many proof of principle studies have demonstrated its potential as a non-invasive delivery tool. However, too few large animal studies and studies with therapeutic aims have been performed to see a clinical application of this technique in the near future. Nevertheless, there is great hope that preclinical large animal studies will confirm the successful results already obtained in small animals.