Synthesis of ultrasound contrast agents: characteristics and size distribution analysis (secondary publication)

PURPOSE: The purpose of this study was to establish a method for ultrasound (US) contrast agent synthesis and to evaluate the characteristics of the synthesized US contrast agent. METHODS: A US contrast agent, composed of liposome and sulfur hexafluoride (SF₆), was synthesized by dissolving 21 μmol 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC, C₄₀H₈₀NO₈P), 9 μmol cholesterol, and 1.9 μmol of dihexadecylphosphate (DCP, [CH₃(CH₂)15O]₂P(O)OH) in chloroform. After evaporation in a warm water bath and drying for 12-24 hours, the contrast agent was synthesized using the sonication process by the addition of a buffer and SF₆ gas. The size distribution of the bubbles was analyzed using dynamic light scattering measurement methods. The degradation curve was evaluated by assessing the change in the number of contrast agent bubbles using light microscopy immediately, 12, 24, 36, 48, 60, 72, and 84 hours after synthesis. The echogenicity of the synthesized microbubbles was compared with commercially available microbubbles (SonoVue, Bracco). RESULTS: contrast agent was synthesized successfully using an evaporation-drying-sonication method. Most bubbles had a mean diameter of 154.2 nm and showed marked degradation 24 hours after synthesis. Although no statistically significant differences were observed between SonoVue and the synthesized contrast agent, a difference in echogenicity was observed between the synthesized contrast agent and saline (P<0.01). CONCLUSION: We successfully synthesized a US contrast agent using an evaporation-dryingsonication method. These results may help future research in the fields of anticancer drug delivery, gene delivery, targeted molecular imaging, and targeted therapy.

Ultrasound-Guided Delivery of siRNA and a Chemotherapeutic Drug by Using Microbubble Complexes: In Vitro and In Vivo Evaluations in a Prostate Cancer Model

OBJECTIVE: To evaluate the effectiveness of ultrasound and microbubble-liposome complex (MLC)-mediated delivery of siRNA and doxorubicin into prostate cancer cells and its therapeutic capabilities both in vitro and in vivo. MATERIALS AND METHODS: Microbubble-liposome complexes conjugated with anti-human epidermal growth factor receptor type 2 (Her2) antibodies were developed to target human prostate cancer cell lines PC-3 and LNCaP. Intracellular delivery of MLC was observed by confocal microscopy. We loaded MLC with survivin-targeted small interfering RNA (siRNA) and doxorubicin, and delivered it into prostate cancer cells. The release of these agents was facilitated by ultrasound application. Cell viability was analyzed by MTT assay after the delivery of siRNA and doxorubicin. Survivin-targeted siRNA loaded MLC was delivered into the xenograft mouse tumor model. Western blotting was performed to quantify the expression of survivin in vivo. RESULTS: Confocal microscopy demonstrated substantial intracellular uptake of MLCs in LNCaP, which expresses higher levels of Her2 than PC-3. The viability of LNCaP cells was significantly reduced after the delivery of MLCs loaded with siRNA and doxorubicin (85.0 ± 2.9%), which was further potentiated by application of ultrasound (55.0 ± 3.5%, p = 0.009). Survivin expression was suppressed in vivo in LNCaP tumor xenograft model following the ultrasound and MLC-guided delivery of siRNA (77.4 ± 4.90% to 36.7 ± 1.34%, p = 0.027). CONCLUSION: Microbubble-liposome complex can effectively target prostate cancer cells, enabling intracellular delivery of the treatment agents with the use of ultrasound. Ultrasound and MLC-mediated delivery of survivin-targeted siRNA and doxorubicin can induce prostate cell apoptosis and block survivin expression in vitro and in vivo.

Optimization of ultrasound parameters for microbubble-nanoliposome complex-mediated delivery

PURPOSE: The aim of this study was to identify the optimal ultrasound (US) parameters for gene and drug delivery. METHODS: In order to target SkBr3, which is a breast cancer cell overexpressing the Her2 receptor, trastuzumab (Herceptin) was used. Micobubble-nanoliposome complex (MLC) was mixed with trastuzumab and stored overnight. Finally, MLC was combined with Her2Ab. A US device equipped with a 1-MHz probe was used for delivery to the cell. Several parameters, including intensity (w/cm2), time (minutes), and duty cycle (%), were varied within a range from 1 w/cm2, 1 minute, and 20% to 2 w/cm2, 2 minutes, and 60%, respectively. A confocal laser scanning microscope (CLSM) was used to confirm the delivery of MLC to the cells after US treatment. RESULTS: MLC with fluorescent dyes and trastuzumab was synthesized successfully. By delivering MLC with Her2Ab to cells, the targeting effect of trastuzumab with MLC was confirmed by CLSM. The cell membranes showed green (fluorescein isothiocyanate) and red (Texas red) fluorescence but treatments with MLC without Her2Ab did not show any fluorescence. Optimal conditions for US-mediated delivery were 1 or 2 w/cm2, 2 minutes, and 60% (uptake ratio, 95.9% for 1 w/cm2 and 95.7% for 2 w/cm2) for hydrophobic materials and 2 w/cm2, 2 minutes, and 60% (uptake ratio, 95.0%) for hydrophilic materials. CONCLUSION: The greater the strength, duty cycle, and period of US application within the tested range, the more efficiently the fluorescent contents were conveyed.

Trastuzumab-Conjugated Liposome-Coated Fluorescent Magnetic Nanoparticles to Target Breast Cancer

OBJECTIVE: To synthesize mesoporous silica-core-shell magnetic nanoparticles (MNPs) encapsulated by liposomes (Lipo [MNP@m-SiO2]) in order to enhance their stability, allow them to be used in any buffer solution, and to produce trastuzumab-conjugated (Lipo[MNP@m-SiO2]-Her2Ab) nanoparticles to be utilized in vitro for the targeting of breast cancer. MATERIALS AND METHODS: The physiochemical characteristics of Lipo[MNP@m-SiO2] were assessed in terms of size, morphological features, and in vitro safety. The multimodal imaging properties of the organic dye incorporated into Lipo[MNP@m-SiO2] were assessed with both in vitro fluorescence and MR imaging. The specific targeting ability of trastuzumab (Her2/neu antibody, Herceptin(R))-conjugated Lipo[MNP@m-SiO2] for Her2/neu-positive breast cancer cells was also evaluated with fluorescence and MR imaging. RESULTS: We obtained uniformly-sized and evenly distributed Lipo[MNP@m-SiO2] that demonstrated biological stability, while not disrupting cell viability. Her2/neu-positive breast cancer cell targeting by trastuzumab-conjugated Lipo[MNP@m-SiO2] was observed by in vitro fluorescence and MR imaging. CONCLUSION: Trastuzumab-conjugated Lipo[MNP@m-SiO2] is a potential treatment tool for targeted drug delivery in Her2/neu-positive breast cancer.

Synthesis of Ultrasound Contrast Agent: Characteristics and Size Distribution Analysis

PURPOSE: The purpose of this study is to establish the methodology regarding synthesis of ultrasound contrast agent imaging, and to evaluate the characteristics of the synthesized ultrasound contrast agents, including size or degradation interval and image quality. MATERIALS AND METHODS: The ultrasound contrast agent, composed of liposome and SF6, was synthesized from the mixture solution of 21 micromol DPPC (1, 2-Dihexadecanoyl-sn-glycero-3-phosphocholine, C40H80NO8P), 9 micromol cholesterol, 1.9 micromol of DCP(Dihexadecylphosphate, [CH3(CH2)15O]2P(O)OH), and chloroform. After evaporation in a warm water bath and drying during a period of 12-24 hours, the contrast agent was synthesized by the sonication process by addition of buffer and SF6 gas. The size of the contrast agent was controlled by use of either extruder or sonication methods. After synthesis of contrast agents, analysis of the size distribution of the bubbles was performed using dynamic light scattering measurement methods. The degradation curve was also evaluated by changes in the number of contrast agents via light microscopy immediate, 12 hours, 24 hours, 36 hours, 48 hours, 60 hours, 72 hours, and 84 hours after synthesis. For evaluation of the role as an US contrast agent, the echogenicity of the synthesized microbubble was compared with commercially available microbubbles (SonoVue, Bracco, Milan, Italy) using a clinical ultrasound machine and phantom. RESULTS: The contrast agents were synthesized successfully using an evaporation-drying-sonication method. The majority of bubbles showed a mean size of 154.2 nanometers, and they showed marked degradation 24 hours after synthesis. ANOVA test revealed a significant difference among SonoVue, synthesized contrast agent, and saline (p < 0.001). Although no significant difference was observed between SonoVue and the synthesized contrast agent, difference in echogenicity was observed between synthesized contrast agent and saline (p < 0.01). CONCLUSION: We could synthesize ultrasound contrast agents using an evaporation-drying-sonication method. On the basis of these results, many prospective types of research, such as anticancer drug delivery, gene delivery, including siRNA or microRNA, targeted molecular imaging, and targeted therapy can be performed.

Sentinel Lymph Node Mapping of the Stomach Using Fluorescent Magnetic Nanoparticles in Rabbits / 대한소화기학회지

BACKGROUND: Sentinel lymph node (SLN) mapping of the stomach cancer using available techniques is limited by unpredictable lymphatic drainage patterns and skip metastasis. The aim of this study was to test the feasibility of gastric SLN mapping using fluorescent magnetic nanoparticles (FMNP) of uniform nano-size. METHODS: Biocompatible silica-overcoated magnetic nanoparticles containing rhodamine B isothiocyanate (RITC) within a silica shell of controllable thickness with 60 nm thickness were used as model nanomaterials. Gastric lymphatic mapping was performed by injecting 100 microliter of either FMNP or isosulafan blue subserosally. Gastric injections (n=7) were made into the body, approximately 5 cm from the lesser curvature of rabbits. Sentinel lymph nodes were visualized using fluorescent nanoparticle detection system. RESULTS: In 7 rabbits, it was demonstrated that FMNP quickly and accurately detected sentinel lymph nodes. Injection into the stomach resulted in identification of a retrogastric lymph node. Histological analysis in all cases confirmed the presence of nodal tissue. CONCLUSIONS: FMNP can be a potential alternative to existing tracers in the detection of SLN in this animal experiment.

Targeting Colon Cancer Cells with Fluorescent Magnetic Nanoparticles Conjugated to Anti-epidermal Growth Factor Receptor Antibodies / 대한소화기내시경학회지

BACKGROUND/AIMS: The aim of this study was to evaluate targeting the epidermal growth factor receptors (EGFRs) of colon cancer cells with fluorescent magnetic nanoparticles (FMNP) conjugated to anti-EGFR antibodies. METHODS: The expression of EGFRs was evaluated in the HT-29 colon cancer cell lines and the control H-520 lung cancer cells by performing Western blot analysis. We synthesized silica-overcoated iron oxide nanoparticles that contained rhodamine B isothiocyanate (RITC) within a silica shell of a controllable thickness. This FMNP was conjugated to anti-EGFR mouse monoclonal antibody. The cells were treated with this probe conjugate for 4 hours and then the targeting was assessed via confocal microscopy. The fluorescence properties were evaluated for their binding to the expressed EGFRs with using a FACScan flow cytometer. RESULTS: EGFR was expressed in the HT-29 cells, as assessed by Western blot analysis. Red fluorescence was only detected in the membrane regions of the HT-29 cells on the confocal microscope imaging. On the FACS analysis, there was a significant shift of fluorescence intensity for the HT-29 cells. CONCLUSIONS: Our data show the feasibility of targeting colon cancer cells with FMNP conjugated with anti-EGFR antibodies in vitro.

Cellular uptake of magnetic nanoparticle is mediated through energydependent endocytosis in A549 cells

Biocompatible silica-overcoated magnetic nanoparticles containing an organic fluorescence dye, rhodamine B isothiocyanate (RITC), within a silica shell [50 nm size, MNP@SiO2(RITC)s] were synthesized. For future application of the MNP@SiO2(RITC)s into diverse areas of research such as drug or gene delivery, bioimaging, and biosensors, detailed information of the cellular uptake process of the nanoparticles is essential. Thus, this study was performed to elucidate the precise mechanism by which the lung cancer cells uptake the magnetic nanoparticles. Lung cells were chosen for this study because inhalation is the most likely route of exposure and lung cancer cells were also found to uptake magnetic nanoparticles rapidly in preliminary experiments. The lung cells were pretreated with different metabolic inhibitors. Our results revealed that low temperature disturbed the uptake of magnetic nanoparticles into the cells. Metabolic inhibitors also prevented the delivery of the materials into cells. Use of TEM clearly demonstrated that uptake of the nanoparticles was mediated through endosomes. Taken together, our results demonstrate that magnetic nanoparticles can be internalized into the cells through an energy-dependent endosomal-lysosomal mechanism.