Future applications of contrast ultrasound

PLGA nanoparticles delivering CPT-11 combined with focused ultrasound inhibit platinum resistant ovarian cancer

Background

Ovarian cancer cells show resistance to platinum drugs treatment, which brings a big challenge to clinical therapeutics. This study aimed to construct effective drug delivering nanoparticles specifically targeting ovarian cancer cell.

Methods

Poly lactic-co-glycolic acid (PLGA) were used to form Nano-spheres by double emulsion method, and to deliver CPT-11. Connected with targeted LHRH-a molecules, their effects were tested by ovarian cancer cell A2780/DDP in vitro and in vivo.

Results

We successfully constructed PLGA nanoparticles carrying LHRH-a (Luteinizing hormone releasing hormone analogue) and CPT-11 (irinotecan HCl trihydrate), which can specifically target LHRH receptor high expression ovarian cancer cell A2780/DDP (cisplatin). Combined with focused ultrasound in vitro, LHRH-a/CPT-11/PLGA nanoparticles significantly inhibited the proliferation of A2780/DDP cells (a cisplatin-resistant A2780 cell line), and the cells were obviously arrested at S phase. Both the mRNA expression and protein level of Caspase3 increased, while Bcl-2 and MMP2 declined, which promoted apoptosis. In vivo, LHRH-a/CPT-11/PLGA nanoparticles bind specifically with LHRH receptor on xenograft tumors of A2780/DDP. With focused ultrasound, LHRH-a/CPT-11/PLGA nanoparticles inhibited the growth of A2780/DDP xenograft tumors significantly. The expression level of VEGF, Bcl-2 and MMP2 reduced, while Caspase3 increased in tumors.

Conclusions

CPT-11 delivering PLGA nanoparticles with LHRH-a specifically target ovarian cancer cell A2780/DDP, and work locally when combined with focused ultrasound. They increase local drug concentration and reduce side effects. This research may provide a new effective therapeutic strategy for recurrent platinum resistant ovarian cancer.

Postoperative Assessment of Myocardial Function and Microcirculation in Patients with Acute Coronary Syndrome by Myocardial Contrast Echocardiography

BACKGROUND Postoperative myocardial function and microcirculation of acute coronary syndrome (ACS) was assessed by myocardial contrast echocardiography (MCE). MATERIAL AND METHODS Eighty-nine ACS patients treated with percutaneous coronary intervention (PCI) were detected by MCE and two-dimensional ultrasonography before and a month later after PCI respectively. Their myocardial perfusion was evaluated by myocardial contrast score (MSC) and contrast score index (CSI); cross-sectional area of microvessel (A), average myocardial microvascular impairment (β), and myocardial blood flow (MBF) were analyzed by cardiac ultrasound quantitative analysis (CUSQ), and fractional flow reserve (FFR) change was observed. Left ventricular ejection fraction (LVEF), left ventricular end-diastolic dimension (LVEDD), and left ventricular end-systolic dimension (LVESD) were observed; the index of microcirculatory resistance (IMR), FFR, and coronary flow reserve (CFR) were detected to evaluate coronary microcirculation. RESULTS None of the 89 patients experienced no-reflow. Patients with normal myocardial perfusion mostly had normal or slightly decreased ventricular wall motion after PCI. A month after the operation, there was an increase in A, β, MBF, LVEF, E/A, IMR, FFR, and CFR (all P<0.05), while LVEDD, LVESD, diastolic gallop A peak, E/Ea, E/Ea×S, and Tei decreased (all P<0.05). LVEF and IMR were in positive correlations with A. LVEF, IMR, FFR and CFR were positively correlated with b and MBF (both r>0, P<0.05), while E/Ea×Sa and Tei were negatively correlated with b and MBF (r<0, P<0.05). CONCLUSIONS MCE can safely assess post-PCI myocardial function and microcirculation of ASC.

Acoustic characterization and pharmacokinetic analyses of new nanobubble ultrasound contrast agents

In contrast to the clinically used microbubble ultrasound contrast agents, nanoscale bubbles (or nanobubbles) may potentially extravasate into tumors that exhibit more permeable vasculature, facilitating targeted molecular imaging and drug delivery. Our group recently presented a simple strategy using the non-ionic surfactant Pluronic as a size control excipient to produce nanobubbles with a mean diameter of 200 nm that exhibited stability and echogenicity on par with microbubbles. The objective of this study was to carry out an in-depth characterization of nanobubble properties as compared with Definity microbubbles, both in vitro and in vivo. Through use of a tissue-mimicking phantom, in vitro experiments measured the echogenicity of the contrast agent solutions and the contrast agent dissolution rate over time. Nanobubbles were found to be more echogenic than Definity microbubbles at three different harmonic frequencies (8, 6.2 and 3.5 MHz). Definity microbubbles also dissolved 1.67 times faster than nanobubbles. Pharmacokinetic studies were then performed in vivo in a subcutaneous human colorectal adenocarcinoma (LS174T) in mice. The peak enhancement and decay rates of contrast agents after bolus injection in the liver, kidney and tumor were analyzed. No significant differences were observed in peak enhancement between the nanobubble and Definity groups in the three tested regions (tumor, liver and kidney). However, the decay rates of nanobubbles in tumor and kidney were significantly slower than those of Definity in the first 200-s fast initial phase. There were no significant differences in the decay rates in the liver in the initial phase or in three regions of interest in the terminal phase. Our results suggest that the stability and acoustic properties of the new nanobubble contrast agents are superior to those of the clinically used Definity microbubbles. The slower washout of nanobubbles in tumors suggests potential entrapment of the bubbles within the tumor parenchyma.

Lung surfactant microbubbles increase lipophilic drug payload for ultrasound-targeted delivery

The cavitation response of circulating microbubbles to targeted ultrasound can be used for noninvasive, site-specific delivery of shell-loaded materials. One challenge for microbubble-mediated delivery of lipophilic compounds is the limitation of drug loading into the microbubble shell, which is commonly a single phospholipid monolayer. In this study, we investigated the use of natural lung surfactant extract (Survanta^®, Abbott Nutrition) as a microbubble shell material in order to improve drug payload and delivery. Pulmonary surfactant extracts such as Survanta contain hydrophobic surfactant proteins (SP-B and SP-C) that facilitate lipid folding and retention on lipid monolayers. Here, we show that Survanta-based microbubbles exhibit wrinkles in bright-field microscopy and increased lipid retention on the microbubble surface in the form of surface-associated aggregates observed with fluorescence microscopy. The payload of a model lipophilic drug (DiO), measured by flow cytometry, increased by over 2-fold compared to lipid-coated microbubbles lacking SP-B and SP-C. Lung surfactant microbubbles were highly echogenic to contrast enhanced ultrasound imaging at low acoustic intensities. At higher ultrasound intensity, excess lipid was observed to be acoustically cleaved for localized release. To demonstrate targeting, a biotinylated lipopolymer was incorporated into the shell, and the microbubbles were subjected to a sequence of radiation force and fragmentation pulses as they passed through an avidinated hollow fiber. Lung surfactant microbubbles showed a 3-fold increase in targeted deposition of the model fluorescent drug compared to lipid-only microbubbles. Our results demonstrate that lung surfactant microbubbles maintain the acoustic responsiveness of lipid-coated microbubbles with the added benefit of increased lipophilic drug payload.

Advances in ultrasound mediated gene therapy using microbubble contrast agents

Microbubble ultrasound contrast agents have the potential to dramatically improve gene therapy treatments by enhancing the delivery of therapeutic DNA to malignant tissue. The physical response of microbubbles in an ultrasound field can mechanically perturb blood vessel walls and cell membranes, enhancing drug permeability into malignant tissue. In this review, we discuss literature that provided evidence of specific mechanisms that enhance in vivo gene delivery utilizing microbubble contrast agents, namely their ability to 1) improving cell membrane permeability, 2) modulate vascular permeability, and 3) enhance endocytotic uptake in cells. Additionally, we review novel microbubble vectors that are being developed in order to exploit these mechanisms and deliver higher gene payloads with greater target specificity. Finally, we discuss some future considerations that should be addressed in the development of next-generation microbubbles in order to improve in vivo microbubble gene delivery. Overall, microbubbles are rapidly gaining popularity as efficient gene carriers, and combined with their functionality as imaging contrast agents, they represent powerful theranostic tools for image guided gene therapy applications.

Perfusion curve f (t) analysis of breast cancer by contrast-enhanced ultrasonography

BACKGROUND

Imaging the perfusion of contrast media in breast tumors may allow improved diagnosing and treating breast cancer.

PURPOSE

To compare the perfusion curve f (t) characteristics of contrast-enhanced ultrasonography in benign and malignant breast tumors.

MATERIAL AND METHODS

Patients with breast tumors (n = 87) were evaluated with contrast-enhanced ultrasonography and the perfusion curve f (t) parameters were calculated using Sonoliver(®) software to compare analysis (tumor) and reference (normal) tissue areas. Differences between breast and breast tumors were assessed.

RESULTS

Compared to benign tumors, malignant tumors had faster enhancement time and a shorter mean transit time (all P values < 0.05). The intensity of the signal was also greater for malignant compared with benign tumors.

CONCLUSION

Perfusion curve f (t) parameter measurements can distinguish differences in vascular flow between malignant and benign breast tumors and may provide a new quantitative indicator of breast tumor.