Ultrasound Imaging Signal Research Articles

Ultrastable fluorinated copolypeptide nanodroplets of loaded mixed liquids with low vaporization threshold

The expansion of ultrasound molecular imaging applications warrants a reduction in ultrasound contrast agent size and significant advancement in the in vivo stability of shell-stabilized bubbles. The shift from first to second-generation ultrasound contrast agents was marked by an improvement in stability as air was replaced by hydrophobic gases like perfluoropropane and sulfur hexafluoride. Further enhancements may be facilitated by focusing on strategies to retain the encapsulated gas within the ultrasound contrast agent shell despite extreme mechanical deformations. In this study, we developed a novel ultrasound contrast agent with a unique shell structure and a specially-formulated, low-boiling fluorinated liquid interior, resulting in superior stability during repeated and prolonged ultrasound-induced oscillations. Our ultra-stable nanodroplets can withstand sustained in vitro ultrasound exposure with minimal signal attenuation and can induce significant signal enhancement and delay in signal attenuation in the kidney, liver, and tumor tissues during in vivo experiments. Furthermore, encapsulating photosensitizers within these nanodroplets and leveraging photothermal effects could further augment the ultrasound imaging signal and verify its efficacy in tumor therapy. The creation of highly stable nanodroplets opens immense potential to augment the role of ultrasound in molecular imaging, therapy, and drug delivery.

A mesoporous theranostic platform for ultrasound and photoacoustic dual imaging-guided photothermal and enhanced starvation therapy for cancer

Tumor starvation therapy utilizing glucose oxidase (GOx), has gained traction due to its non-invasive and bio-safe attributes. However, its effectiveness is often hampered by severe hypoxia in the tumor microenvironment (TME), limiting GOx's catalytic activity. To address this issue, a multifunctional nanosystem based on mesoporous polydopamine nanoparticles (MPDA NPs) was developled to alleviate TME hypoxia. This nanosystem integrated GOx modification and oxygenated perfluoropentane (PFP) encapsulation to address hypoxia-related challenges in the TME. Under NIR laser irradiation, the MPDA NPs exhibit significant photothermal conversion efficacy, activating targeted tumor photothermal therapy (PTT), while also serving as proficient photoacoustic (PA) imaging agents. The ensuing temperature rise facilitates oxygen (O2) release and induces liquid-gas conversion of PFP, generating microbubbles for enhanced ultrasound (US) imaging signals. The supplied oxygen alleviates local hypoxia, thereby enhancing GOx-mediated endogenous glucose consumption for tumor starvation. Overall, the integration of ultrasound/photoacoustic dual imaging-guided PTT and starvation therapy within MPDA-GOx@PFP@O2 nanoparticles (MGPO NPs) presents a promising platform for enhancing the efficacay of tumor treatment by overcoming the complexities of the TME. Statement of significanceA multifunctional MPDA-based theranostic nanoagent was developed for US/PAI imaging-guided PTT and starvation therapy against tumor hypoxia by direct O2 delivery. The incorporation of oxygenated perfluoropentane (PFP) within the mesoporous structure of MGPO not only enables efficient US imaging but also helps in alleviating tumor hypoxia. Moreover, the strong near-infrared (NIR) absorption of MGPO NPs promote the generation of PFP microbubbles and release of oxygen, thereby enhancing US imaging and GOx-mediated starvation therapy. Such a multifunctional nanosystem leverages synergistic effects to enhance therapeutic efficacy while incorporating US/PA imaging for precise visualization of the tumor.

Investigation of a method to estimate the average speed of sound using phase variances of element signals for ultrasound compound imaging

PurposeIn the receive beamforming of an ultrasonography system, a B-mode image is reconstructed by assuming an average speed of sound (SoS) as a constant value. In our previous studies, we proposed a method for estimating the average SoS based on the coherence factor (CF) and the reciprocal of phase variances of element signals in delay-and-sum (DAS) beamforming. In this paper, we investigate the accuracy of estimation of the average SoS for compound imaging.MethodsFor this purpose, two numerical simulations were performed with k-Wave software. Also, the estimation methods based on the CF and the reciprocal were applied to in vivo data from the common carotid artery, and B-mode images were reconstructed using the estimated average SoS.ResultsIn the first numerical simulation using an inhomogeneous phantom, the relationship between the accuracy and the transmission angles for the estimation was investigated, and the root mean squared errors (RMSEs) of estimates obtained based on the CF and the reciprocal of the phase variance were 1.25 ± 0.09, and 0.765 ± 0.17% at the transmission sequence of steering angles of (− 10°, − 5°, 0°, 5°, 10°), respectively. In the second numerical simulation using a cyst phantom, lateral resolutions were improved by reconstructing the image using the estimates obtained using the proposed strategy (reciprocal). By the proposed strategy, improvement of the continuity of the lumen–intima interface in the lateral direction was observed in the in vivo experiment.ConclusionConsequently, the results indicated that the proposed strategy was beneficial for estimation of the average SoS and image reconstruction.

Technical note: Evaluation of the acoustic radiation force imaging for predicting HIFU focus with in vitro and ex vivo experiments.

High-intensity focused ultrasound (HIFU) is currently used for the treatment of various diseases, but it still lacks a reliable technique in the preoperative stage to accurately place its "energy blade" onto diseased targets. Acoustic radiation force imaging (ARFI) was recently introduced to tackle this issue, but its applicability and limitations were not clear. The aim of this study was to evaluate the performance of ARFI method in prediction of HIFU focal location at the preoperative stage. A point spread function (PSF) localization method, which was borrowed from the ultrasound super resolution field, was used to validate the core autocorrelation-based motion estimation algorithm in the ARFI procedure. Accuracy of the ARFI method for estimating the HIFU focus were tested with in vitro and ex vivo experiments with a clinically equivalent HIFU system. Comparisons were made between the estimated focal locations and those of the damaged area after the testing objects were cut open. Results showed that the PSF localization was able to serve as a validating method for motion detection only when the tissue displacement was large. With the ARFI method, location of the HIFU focus could be accurately predicted by a 2D motion map preoperatively, and the axial spatial errors were less than 0.5mm. However, the derived 2D motion maps can only be valuable when the acoustic stimulation in ARFI were strong enough, which was probably due to the fact that the HIFU focal locations were at large depths and the ultrasound imaging signal had low signal to noise ratio. The ARFI method was indeed an accurate technique for preoperatively predicting HIFU focus in vitro and ex vivo. If clinical applications were to be considered, particularly in deep tissues, efforts might need to be made to improve ability of the ultrasound motion estimation technique.

Aptamer-Functionalized Microbubbles Targeted to P-selectin for Ultrasound Molecular Imaging of Murine Bowel Inflammation.

Our objectives were to develop a targeted microbubble with an anti-P-selectin aptamer and assess its ability to detect bowel inflammation in two murine models of acute colitis. Lipid-shelled microbubbles were prepared using mechanical agitation. A rapid copper-free click chemistry approach (azide-DBCO) was used to conjugate the fluorescent anti-P-selectin aptamer (Fluor-P-Ap) to the microbubble surface. Bowel inflammation was chemically induced using 2,4,6-trinitrobenzenesulfonic acid (TNBS) in both Balb/C and interleukin-10-deficient (IL-10 KO) mice. Mouse bowels were imaged using non-linear contrast mode following an i.v. bolus of 1 × 108 microbubbles. Each mouse received a bolus of aptamer-functionalized and non-targeted microbubbles. Mouse phenotypes and the presence of P-selectin were validated using histology and immunostaining, respectively. Microbubble labelling of Fluor-P-Ap was complete after 20min at 37 ̊C. We estimate approximately 300,000 Fluor-P-Ap per microbubble and confirmed fluorescence using confocal microscopy. There was a significant increase in ultrasound molecular imaging signal from both Balb/C (p = 0.003) and IL-10 KO (p = 0.02) mice with inflamed bowels using aptamer-functionalized microbubbles in comparison to non-targeted microbubbles. There was no signal in healthy mice (p = 0.4051) using either microbubble. We constructed an aptamer-functionalized microbubble specific for P-selectin using a clinically relevant azide-DBCO click reaction, which could detect bowel inflammation in vivo. Aptamers have potential as a next generation targeting agent for developing cost-efficient and clinically translatable targeted microbubbles.

Rapid Copper-free Click Conjugation to Lipid-Shelled Microbubbles for Ultrasound Molecular Imaging of Murine Bowel Inflammation.

Microbubbles are ultrasound contrast agents that can adhere to disease-related vascular biomarkers when functionalized with binding ligands such as antibodies or peptides. The biotin-streptavidin approach has predominantly been used as the microbubble labeling approach in preclinical imaging. However, due to the immunogenicity of avidin in humans, it is not suitable for clinical translation. What would aid clinical translation is a simple and effective microbubble functionalization approach that could be directly translated from animals to humans. We developed a targeted microbubble to P-selectin, a vascular inflammatory marker, labeled using a strain-promoted [3 + 2] azide-alkyne (azide-DBCO) reaction, comparing its ability to detect bowel inflammation to that of P-selectin targeted microbubbles labeled with a traditional biotin-streptavidin approach. Bowel inflammation was chemically induced using 2,4,6-trinitrobenzenesulfonic acid (TNBS) in Balb/C mice. Each mouse received both non-targeted and P-selectin targeted microbubbles (either biotin-streptavidin or azide-DBCO). Using the biotin-streptavidin reaction, there was a significant increase in the ultrasound molecular imaging signal in inflamed mice using P-selectin targeted (2.30 ± 0.91 a.u.) compared to isotype control microbubbles (1.14 ± 0.7 a.u.) (p = 0.009). Using the azide-DBCO reaction, there was a similar increase in the ultrasound molecular imaging signal in inflamed mice (2.54 ± 0.56 a.u) compared to the isotype control (0.44 ± 0.25 a.u) (p = 0.009). There were no significant differences between the two labeling approaches between non-targeted and P-selectin targeted microbubbles. Mouse inflammatory phenotypes and expression of P-selectin were validated using histology and immunostaining. We constructed P-selectin targeted microbubbles using an azide-DBCO click reaction, which could detect bowel inflammation in vivo. This reaction generated a similar ultrasound molecular imaging signal to biotin-strepavidin-labeled microbubbles. These data show the potential of click chemistry conjugation (azide-DBCO) as a quick, cost-efficient, and clinically translatable approach for developing targeted microbubbles.

Nanogel loading 808 nm laser-activated organic dyes with a special D− π − a structure and the regulation of their photothermal property by non-conjugated modification

Here, we firstly designed an advanced PTA, probe-1, based on a special D− π − A structure with strong NIR absorption near 800 nm. It is successfully dispersed into water and endowed with targetability for tumors by loading into hydrogel to form nanoparticles, probe-1-cRGD. However, the absorption peak (λmax) of probe-1-cRGD blue-shifted to 690 nm because the strong antiparallel aggregation, which deviated from the ideal 808 nm excitation. To optimize the photothermal performances at 808 nm after loading to hydrogel, we further constructed another PTA, probe 2, by changing the non-conjugated substituents to regulate its aggregation behavior. The experimental data shows that both probes possess high PTCEs (60.5% and 57.3%) and that probe-2-cRGD exhibits a better photothermal performance under 808 nm laser excitation because it has a greater absorbance than probe-1-cRGD at 808 nm, and the results proved that site-isolation principle could play an important role in the optimizing the photothermal performance for the D− π − A type PTAs. Probe-2-cRGD maintained its better photothermal properties in vivo and was found to completely ablate tumors during photothermal therapy. It also demonstrated a distinct photoacoustic imaging signal and enhanced ultrasound imaging signals of tumors in vivo.

Phase-Change Nanotherapeutic Agents Based on Mesoporous Carbon for Multimodal Imaging and Tumor Therapy.

A multifunctional nanotherapeutic agent based on mesoporous carbon is reported for multimodal imaging and cancer therapy. The nanoplatform consists of oxidized mesoporous carbon nanoparticles (OMCNs) as a near-infrared (NIR) photoresponse carrier and perfluoropentane (PFP) as a phase-change agent. OMCNs can absorb the NIR excitation light and convert it into heat, which not only triggers the thermal ablation of cancer cells but also promotes liquid-gas phase change for gasification of PFP to enhance the in site tumor ultrasound (US) and photoacoustic (PA) imaging signals. This nanoplatform demonstrates good biocompatibility, attractive ability to US/PA imaging, and excellent photothermal therapy efficiency.

MAGE-Targeted Gold Nanoparticles for Ultrasound Imaging-Guided Phototherapy in Melanoma.

Gold nanorods exhibit a wide variety of applications such as tumor molecular imaging and photothermal therapy (PTT) due to their tunable optical properties. Several studies have demonstrated that the combination of other therapeutic strategies may improve PTT efficiency. A method called optical droplet vaporization (ODV) was considered as another noninvasive imaging and therapy strategy. Via the ODV method, superheated perfluorocarbon droplets can be vaporized to a gas phase for enhancing ultrasound imaging; meanwhile, this violent process can cause damage to cells and tissue. In addition, active targeting through the functionalization with targeting ligands can effectively increase nanoprobe accumulation in the tumor area, improving the sensitivity and specificity of imaging and therapy. Our study prepared a nanoparticle loaded with gold nanorods and perfluorinated hexane and conjugated to a monoclonal antibody (MAGE-1 antibody) to melanoma-associated antigens (MAGE) targeting melanoma, investigated the synergistic effect of PTT/ODV therapy, and monitored the therapeutic effect using ultrasound. The prepared MAGE-Au-PFH-NPs achieved complete eradication of tumors. Meanwhile, the MAGE-Au-PFH-NPs also possess significant ultrasound imaging signal enhancement, which shows the potential for imaging-guided tumor therapy in the future.

Dendritic organosilica nanospheres with large mesopores as multi-guests vehicle for photoacoustic/ultrasound imaging-guided photodynamic therapy

Photodynamic therapy (PDT) is a minimally invasive treatment strategy that uses photosensitizers and light in combination with oxygen to generate cytotoxic singlet oxygen (1O2) to kill cancer cells by necrosis or apoptosis. However, the treatment effects are still not satisfactory because of the tumor hypoxia and the PDT-induced oxygen consumption. Here, we have successfully synthesized dendritic mesoporous organosilica nanoparticles (MONs) with large center-radial pore structure that can be used to simultaneously encapsulate indocyanine green (ICG, <1 nm) and macromolecule catalase (CAT, 2.0 nm × 6.0 nm × 9.0 nm) to overcome the tumor hypoxia. Upon 808 nm laser irradiation, ICG as the organic NIR dye can generate highly cytotoxic singlet oxygen (1O2) and other reactive oxygen species (ROS) to kill cancer cells and realize photoacoustic (PA) imaging. The catalase can decompose the endogenous H2O2 in malignant cancerous cells into O2 bubble to simultaneously intensify the ultrasound (US) imaging signal and enhance PDT efficacy. These results indicate that the ICG-CAT@MONs holds great promise in multimodal photoacoustic / ultrasound image-guided tumor PDT therapy.

On-demand drug release nanoplatform based on fluorinated aza-BODIPY for imaging-guided chemo-phototherapy

Intelligent drug delivery systems (DDS), integrating with multi-modal imaging guidance and controlled drug release, have practical significance in enhancing the therapeutic efficiency of tumors. Herein, fluorinated aza-boron-dipyrromethene (NBF) with high near-infrared absorption is synthesized by introducing nonadecafluorodecanoic acid into aza-BODIPY via the amide bond. Through the co-precipitation methods, nanoparticles (NPs) based on NBF are fabricated and the obtained NBF NPs can not only load with DOX with a high loading efficiency (25%, DNBF NPs), but also absorb PFC droplets (1H-perfluoropentane) with bp of 42 °C because of the fluorinated chains inside NBF NPs (PDNBF NPs). Under 808-nm laser irradiation, the hyperthermia effect of NBF could induce the liquid-gas phase transition of PFC droplets, triggering the burst release of DOX and enhancing echo signals for ultrasound imaging as well. With efficient enrichment of PDNBF NPs at tumor site as revealed by in vivo ultrasound imaging and photoacoustic imaging, significant improvement in inhibiting tumor growth is achieved with PDNBF NPs under laser irradiation without noticeable side effects. The work presents a multifunctional organic DDS with great biocompatibility, high drug loading efficiency and light-stimuli-responsive drug release, which provides a new strategy for the manufacture of intelligent composite theranostic nanoplatform.

Ultrasound Molecular Imaging of Renal Cell Carcinoma: VEGFR targeted therapy monitored with VEGFR1 and FSHR targeted microbubbles

Recent treatment developments for metastatic renal cell carcinoma offer combinations of immunotherapies or immunotherapy associated with tyrosine kinase inhibitors (TKI). There is currently no argument to choose one solution or another. Easy-to-use markers to assess longitudinal responses to TKI are necessary to determine when to switch to immunotherapies. These new markers will enable an earlier adaptation of therapeutic strategy in order to prevent tumor development, unnecessary toxicity and financial costs. This study evaluates the potential of ultrasound molecular imaging to track the response to sunitinib in a clear cell renal carcinoma model (ccRCC). We used a patient-derived xenograft model for this imaging study. Mice harboring human ccRCC were randomized for sunitinib treatment vs. control. The tumors were imaged at days 0, 7, 14 and 28 with ultrasound molecular imaging. Signal enhancement was quantified and compared between the two groups after injections of non-targeted microbubbles and microbubbles targeting VEGFR1 and FSHR. The tumor growth of the sunitinib group was significantly slower. There was a significantly lower expression of both VEGFR-1 and FSHR molecular ultrasound imaging signals in the sunitinib group at all times of treatment (Days 7, 14 and 28). These results confirm the study hypothesis. There was no significant difference between the 2 groups for the non-targeted microbubble ultrasound signal. This study demonstrated for the first time the potential of VEGFR1 and FSHR, by ultrasound-based molecular imaging, to follow-up the longitudinal response to sunitinib in ccRCC. These results should trigger developments for clinical applications.

Prediction of Ankle Dorsiflexion Moment by Combined Ultrasound Sonography and Electromyography.

To provide an effective and safe therapy to persons with neurological impairments, accurate determination of their residual volitional ability is required. However, accurate measurement of the volitional ability, through non-invasive means (e.g., electromyography), is challenging due to signal interference from neighboring muscles or stimulation artifacts caused by functional electrical stimulation (FES). In this work, a new model-based intention detection method that combines signals from both surface electromyography (sEMG) and ultrasound (US) sonography to predict isometric volitional ankle dorsiflexion moment is proposed. The work is motivated by the fact that the US-derived signals, unlike sEMG, provide direct visualization of the muscle activity, and hence may enhance the prediction accuracy of the volitional ability, when combined with sEMG. The weighted summation of sEMG and US imaging signals, measured on the tibialis anterior muscle, is utilized as an input to a modified Hill-type neuromusculoskeletal model that predicts the ankle dorsiflexion moment. The effectiveness of the proposed model-based moment prediction method is validated by comparing the predicted and the measured ankle joint moments. The new modeling method has a better prediction accuracy compared to a prediction model that uses sole sEMG or sole US sonography. This finding provides a more accurate approach to detect movement intent in the lower limbs. The approach can be potentially beneficial for the development of US sonography-based robotic or FES-assisted rehabilitation devices.

Biodegradable nanotheranostics with hyperthermia-induced bubble ability for ultrasound imaging-guided chemo-photothermal therapy.

BackgroundTheranostics, elaborately integrating both therapeutic and diagnostic functions into a nanoplatform holds great potential for precision cancer medicine.MethodsHerein, a biodegradable theranostic nanoplatform with hyperthermia-induced bubble ability for highly efficient ultrasound (US) imaging–guided chemo-photothermal therapy of breast tumors was developed. The prepared nanoparticles consisted of polydopamine (PDA)-modified hollow mesoporous organosilica nanoparticles (HMONs) with approximately 75 nm in diameter for doxorubicin (DOX) loading and perfluoropentane (PFP) filling. In addition, the pH-sensitive PDA coating served as both gatekeeper controlling DOX release and photothermal agent for inducing hyperthermia.ResultsSuch nanoplatform (PDA@HMONs-DOX/PFP, PHDP) provides efficient loading (328 mg/g) and controllable stimuli-responsive release of DOX for chemotherapy. The incorporated disulfide bonds in the framework of HMONs endowed nanoparticles with intrinsic glutathione-responsive biodegradability and improved biocompatibility. Benefiting from the hyperthermia upon an 808-nm laser irradiation of PDA, the liquid–gas phase transition of the loaded PFP was induced, resulting in the generation of the nanobubbles, followed by the coalescence into microbubbles. This conversation could enhance the tumor cell uptake of nanoparticles, as well as intensify the US imaging signals. In addition, a synergistic therapeutic effect of our fabricated nanoplatform on cells/tumor growth effect has been systematically evaluated both in vitro and in vivo.ConclusionTherefore, such “all-in-one” PHDP nanoparticles with satisfactory biocompatibility and biodegradability, hyperthermia-induced bubble ability and simultaneous US imaging performance hold great potential for cancer nanotheranostics.

Scale-up production, characterization and toxicity of a freeze-dried lipid-stabilized microbubble formulation for ultrasound imaging and therapy

Microbubble formulations have a long history for enhancement of ultrasound (US) imaging and recently also for therapeutic applications. Previously, a series of freeze-dried bubble formulations based on the lipids DSPC and DSPG were developed. Here, we have attempted to scale-up the production process for future more extensive studies. Bubbles were prepared by homogenization of a lipid dispersion in a perfluoropropane atmosphere in a medium size (300–500 mL) homogenizer and then freeze-dried for better storage stability. In total, 300 freeze-dried vials were prepared. The properties of the bubbles were similar to those previously prepared on a lab scale with the difference that they were slightly larger and also had a better stability. The re-entrapped gas concentration after re-constituted freeze-dried bubbles was 9.4 µL/µmol lipid. The re-entrapped rate was 72.3% of fresh bubble before freeze-drying (13.0 µL/µmol lipid). The half-life of US imaging signal of the re-constituted freeze-dried bubbles in water in vitro was shorter than that of the fresh bubbles (2.7 min vs. 3.3 min). A leak of Evans Blue, that binds to albumin, from mouse ear blood vessel was observed after combination of bubble and US irradiation of 1 MHz for 1 min. As a result of bubble vibration by US irradiation, vascular endothelial cell bond opened and Evans Blue leaked. Toxicity of bubble was tested in rats. No toxicity was found after a single injection in the dose range tested. No serious toxicity was seen after repeated injections (one daily injection during 15 days).

Ultrasound Molecular Imaging of Lymphocyte-endothelium Adhesion Cascade in Acute Cellular Rejection of Cardiac Allografts.

Acute cellular rejection is one of the main reasons for graft failure after heart transplantation. A precise diagnosis at the early stage of acute cellular rejection is a big challenge for clinicians. Given the importance of the interaction between T cells and graft endothelia in initiating rejection, we developed T cell-microbubble complexes (cell-MBs) as ultrasound molecular imaging probes to monitor the lymphocyte-endothelium adhesion cascade in cardiac acute cellular rejection. Cell-MBs were fabricated by incubating lymphocytes with anti-CD4 antibody-conjugated MBs (MBCD4). The potential of cell-MBs as probes for detecting acute cardiac rejection was examined. Donor hearts from Brown Norway or Lewis rats were transplanted into Lewis recipients. Ultrasound molecular imaging was performed on allografts of untreated or cyclosporin A (CsA)-treated recipients, and isografts on posttransplantation day 3. Histology was used to assess rejection grades. We detected a significantly stronger ultrasound molecular imaging signal of cell-MBs than that of MBCD4 or plain MBs in allografts of untreated and CsA-treated recipients. No signal enhancement was observed in isografts with cell-MBs. The signal of cell-MBs in allografts of the untreated group was significantly higher than that in the CsA-treated group, and the signal in the CsA-treated group was higher than that in isografts. Histology confirmed grade 3R rejection in the untreated group, grade 2R rejection in CsA-treated group, and no rejection in isografts. Our study suggests that cell-MBs can function as a promising probe to image the dynamic lymphocyte-endothelium adhesion cascade for noninvasive diagnosis of cardiac acute cellular rejection.

Molecular Ultrasound Monitoring of Early Artery Injury After Carotid Balloon Angioplasty.

Cardiovascular intervention is a common treatment procedure for many cardiovascular diseases. But restenosis often occurs after these procedures, greatly discounting their long-term therapeutic effects. Early detection of endothelial denudation is helpful for the diagnosis and prevention of restenosis. Here, we fabricated targeted microbubbles by conjugating anti-collagen IV antibodies to the surface of biotinylated microbubbles (MBColIV) and applied them for ultrasound molecular imaging of endothelial injury at early stage. Our results showed that the MBColIV, with a typical multi-peak particle distribution, was successfully constructed, which was confirmed by Alexa Fluor® 555-labeled secondary antibody. Ex vivo adhesion of microbubbles revealed that MBColIV can effectively and specially bind to the surface of balloon-injured carotid artery. The in vivo animal experiments showed ultrasound molecular imaging signals from carotid artery-injured rats administrated with MBColIV were significantly higher than those administrated with isotype control microbubbles. Histological staining of the left carotid common artery revealed that collagen IV was obviously exposed after endothelium denudation in balloon-injured artery. In conclusion, our current study provides an effective approach to detect vascular injury at the early stage and a potential platform for image-guided therapy to vascular injury.

Hyaluronic acid and polydopamine functionalized phase change nanoparticles for ultrasound imaging-guided photothermal-chemotherapy.

In this study, we successfully prepared polydopamine (PD) and hyaluronic acid (HA) coated liquid perfluorocarbon nanoparticles, which integrated the good photothermal conversion effect of PD, the ultrasound imaging properties of the liquid fluorocarbon and active tumor-targeting of HA. Liquid perfluorocarbon nanodroplets significantly improved in terms of their physical stability after being coated with PD and HA as the shell. Photothermal and ultrasound imaging experiments showed that PD could effectively convert near-infrared (NIR) laser energy into heat for photothermal therapy, which could induce a phase change of the liquid perfluorocarbon, thereby generating microbubbles, enhancing ultrasound imaging signals and promoting drug release. In vitro cellular experiments showed that HA on the surface of the nanoparticles could actively target 4T1 breast cancer cells by CD44 receptor-mediated endocytosis. Furthermore, the novel nanosystem has shown effective inhibition of tumor growth by synergistic photothermal-chemotherapy in tumor-bearing mice. In conclusion, the novel nanosystem we prepared in this study is expected to provide a new strategy for the diagnosis and treatment of cancer.

Preparation and Imaging Investigation of Dual-targeted C3F8-filled PLGA Nanobubbles as a Novel Ultrasound Contrast Agent for Breast Cancer

Molecularly-targeted contrast enhanced ultrasound (US) imaging is a promising imaging strategy with large potential for improving diagnostic accuracy of conventional US imaging in breast cancer detection. Therefore, we constructed a novel dual-targeted nanosized US contrast agent (UCA) directed at both vascular endothelial growth factor receptor 2 (VEGFR2) and human epidermal growth factor receptor 2 (HER2) based on perfluoropropane (C3F8)-filled poly(lactic-co-glycolic acid) (PLGA) (NBs) for breast cancer detection. In vitro, single- or dual-targeted PLGA NBs showed high target specificities and better effects of target enhancement in VEGFR2 or HER2-positive cells. In vivo, US imaging signal in the murine breast cancer model was significantly higher (P < 0.01) for dual-targeted NBs than single-targeted and non-targeted NBs. Small animal fluorescence imaging further confirmed the special affinity of the dual-targeted nanosized contrast agent to both VEGFR2 and HER2. Immunofluorescence and immunohistochemistry staining confirmed the expressions of VEGFR2 and HER2 on tumor neovasculature and tumor cells of breast cancer. In conclusions, the feasibility of using dual-targeted PLGA NBs to enhance ultrasonic images is demonstrated in vitro and in vivo. This may be a promising approach to target biomarkers of breast cancer for two site-specific US molecular imaging.

Ultrasound Molecular Imaging of Atherosclerosis for Early Diagnosis and Therapeutic Evaluation through Leucocyte-like Multiple Targeted Microbubbles.

Cardiovascular diseases resulting from atherosclerosis have become a serious threat to human health. It is well-known that an ongoing inflammatory response is involved during atherosclerosis progression that ultimately results in the accumulation of lipids and formation of plaques. Monitoring the pathological changes during the inflammatory response will be of great significance for early diagnosis and therapeutic evaluation of atherosclerosis. Targeted contrast-enhanced ultrasonography has been shown to be a promising noninvasive imaging technique for evaluating the degree of atherosclerosis and may potentially be translated to clinical imaging in the future. However, inadequate cell adhesion of targeted microbubbles (MBs) in large arterial vessels still remains a great challenge.Methods: By mimicking the leucocytes that are recruited to the vessel wall during the initiation of atherosclerosis through selectin-dependent arrest and cell adhesion molecule-mediated firm cell adhesion, we developed VCAM-1/ICAM-1/P-selectin-targeted MBVIS by integrating VCAM-1 and ICAM-1 antibodies and synthetic polymeric sialyl Lewis X (sLex) onto the MB surface.Results: The resulting MBVIS had a high affinity to inflammatory bEnd.3 cells in both static and dynamic flow conditions. Significantly enhanced ultrasound imaging signals were achieved by MBVIS in detecting the atherosclerosis progress when compared with the single- or dual-targeted MBs. Taking advantage of the artificial MBVIS, less ultrasound imaging signals were found in the atorvastatin-treated, but not placebo-treated, ApoE-deficient mice with atherosclerosis, revealing a potential therapeutic efficacy of atorvastatin for early stage atherosclerosis. This was further confirmed by histologic staining examination.Conclusions: Our study provides a promising ultrasound molecular imaging probe for early-stage diagnosis and therapeutic evaluation of atherosclerosis.