Nanobubbles for enhanced ultrasound imaging of tumors

The fabrication and initial applications of nanobubbles (NBs) have shown promising results in recent years. A small particle size is a basic requirement for ultrasound contrast-enhanced agents that penetrate tumor blood vessel pores to allow for targeted imaging and therapy. However, the nanoscale size of the particles used has the disadvantage of weakening the imaging ability of clinical diagnostic ultrasound. In this work, we fabricated a lipid NBs contrast-enhanced ultrasound agent and evaluated its passive targeting ability in vivo. The results showed that the NBs were small (436.8 ± 5.7 nm), and in vitro ultrasound imaging suggested that the ultrasonic imaging ability is comparable to that of microbubbles (MBs). In vivo experiments confirmed the ability of NBs to passively target tumor tissues. The NBs remained in the tumor area for a longer period because they exhibited enhanced permeability and retention. Direct evidence was obtained by direct observation of red fluorescence-dyed NBs in tumor tissue using confocal laser scanning microscopy. We have demonstrated the ability to fabricate NBs that can be used for the in vivo contrast-enhanced imaging of tumor tissue and that have potential for drug/gene delivery

The Optimized Fabrication of a Novel Nanobubble for Tumor Imaging

Nanobubbles with a size of less than 1 µm can be used as ultrasound contrast agents for diagnosis and as drug/gene carriers for therapy. However, the optimal method of preparing uniform-sized nanobubbles is considered controversial. In this study, we developed novel biocompatible nanobubbles by performing differential centrifugation to isolate the relevant subpopulation from the parent suspensions. Compared with the method of modulating the thickness of the phospholipid film without centrifugation, nanobubbles fabricated under optimal centrifugation conditions exhibited a uniform bubble size, good stability, and low toxicity. Using in vitro ultrasound imaging, nanobubbles displayed excellent enhancement ability, which was comparable to microbubbles. In an in vivo experiment, the video intensity of nanobubbles in tumors was stronger than that of microbubbles at different times (5 min, 163.5 ± 8.3 a.u. vs. 143.2 ± 7.5 a.u., P < 0.01; 15 min, 125.4 ± 5.2 a.u. vs. 97.3 ± 4.6 a.u., P < 0.01). Fluorescence imaging obtained by confocal laser scanning microscopy demonstrated that obviously more nanobubbles passed through the vessel wall into the extravascular and intercellular space of tumors, compared with microbubbles. In conclusion, this optimized preparation method will strongly promote the application of nanobubbles in imaging and therapy

Recent Advances about Local Gene Delivery by Ultrasound

Gene therapy has been widely explored as a pharmacological approach, with a great potential to treat various diseases. Generally, many diseases have definite lesion’s site, especially for tumors. This feature results in a great demand on the delivery of therapeutic gene to the local lesion’s site. Ultrasound combined with microbubbles provides a promising platform to deliver gene in a spatiotemporally controlled way. Ultrasound beam can be positioned and targeted onto the deep-seated lesion’s site of diseases by an external mobile transducer. Microbubbles can serve as vehicles for carrying genetic cargo and can be destructed by ultrasound, resulting in the local release of genetic payload. Meanwhile, sonoporation effect will occur upon which the bubbles are exposed to the appropriate ultrasonic energy, producing the transient small holes on the adjacent cell membrane and thus increasing the vascular and cellular permeability. In this chapter, we will review the recent advances about local gene delivery by ultrasound

Ultrasound Targeted Apoptosis Imaging in Monitoring Early Tumor Response of Trastuzumab in a Murine Tumor Xenograft Model of Her-2–Positive Breast Cancer1

AbstractOBJECTIVE: Our study aimed to monitor the trastuzumab therapy response of murine tumor xenograft model with human epidermal growth factor receptor 2 (Her-2)–positive breast cancer using ultrasound targeted apoptosis imaging. METHODS: We prepared targeted apoptosis ultrasound probes by nanobubble (NB) binding with Annexin V. In vitro, we investigated the binding rate of NB–Annexin V with breast cancer apoptotic cells after the trastuzumab treatment. In vivo, tumor-bearing mice underwent ultrasound targeted imaging over 7 days. After imaging was completed, the tumors were excised to determine Her-2 and caspase-3 expression by immunohistochemistry (IHC). The correlation between parameters of imaging and histologic results was then analyzed. RESULTS: For seeking the ability of targeted NB binding with apoptotic tumor cells (Her-2 positive), we found that binding rate in the treatment group was higher than that of the control group in vitro (P = .001). There were no differences of tumor sizes in all groups over the treatment process in vivo (P = .98). However, when using ultrasound imaging to visualize tumors by targeted NB in vivo, we observed that the mean and peak intensities from NBs gradually increased in the treatment group after trastuzumab therapy (P = .001). Furthermore, these two parameters were significantly associated with caspase-3 expression of tumor excised samples (P = .0001). CONCLUSION: Ultrasound targeted apoptosis imaging can be a non-invasive technique to evaluate the early breast tumor response to trastuzumab therapy

HIGH INTENSITY FOCUSED ULTRASOUND AND OXYGEN LOAD NANOBUBBLES: TWO DIFFERENT APPROCHES FOR CANCER TREATMENT

The study of applications based on the use of ultrasound in medicine and biology for therapeutic purposes is under strong development at international level and joins the notoriously well-established and widespread use of diagnostic applications [1]. In the past few years, High Intensity Focused Ultrasound (HIFU) has developed from a scientific curiosity to an accepted therapeutic modality. HIFU is a non invasive technique for the treatment of various types of cancer, as well as non-malignant pathologies, by inducing localized hyperthermia that causes necrosis of the tissue. Beside HIFU technology, other innovative therapeutic modalities to treat cancer are emerging. Among them, an extremely innovative technique is represented by oxygen loaded nanobubbles (OLNs): gas cavities confined by an appropriately functionalized coating. This is an oxygenating drugs aimed at re-oxygenation of cancerous tissue. Oxygen deficiency, in fact, is the main hallmark of cancerous solid tumors and a major factor limiting the effectiveness of radiotherapy. In this work, these two approaches to treat tumours are under study from a metrological point of view. In particular, a complete characterization of an HIFU fields regarding power, pressure and temperature is provided while oxygen load nanobubbles are synthesized, characterized and applied in in vitro and in vivo experiments