Super-Resolution Ultrasound Reveals Cerebrovascular Impairment in a Mouse Model of Alzheimer's Disease.

Increasing evidence has suggested a link between cerebrovascular disease and the cognitive impairment associated with Alzheimer's disease. However, detailed descriptions of microvascular changes across brain regions and how they relate to other more traditional pathology have been lacking. Additionally, the efforts to elucidate the interplay between cerebral microvascular function and Alzheimer's disease progression are complicated by the necessity of probing deep-brain structures since early-stage Alzheimer's disease typically involves hippocampal pathology. The purpose of this study was to examine changes in microvascular dynamics in a mouse model of Alzheimer's disease using cohorts that were age-matched to wild-type controls. Data from both sexes were included in this study. Super-resolution ultrasound localization microscopy revealed microvascular functional and structural features throughout the whole brain depth to visualize and quantify. We found that functional decreases in hippocampal and entorhinal flow velocity preceded structural derangements in regional vascular density. Co-registered histological sectioning confirmed the regionalized perfusion deficits seen on ultrasound imaging, which were co-localized with amyloid beta plaque deposition. In addition to providing global vascular quantifications of deep brain structures with a high local resolution, this technology also permitted velocity-profile analysis of individual vessels and, in some cases, allowed for decoupling of arterial and venous flow contributions. These data suggest that microvascular pathology is an early and pervasive feature of Alzheimer's disease and may represent a novel therapeutic target for this disease.

Ultrasound-targeted microbubble destruction facilitates cartilage repair through increased the migration of mesenchymal stem cells via HIF-1α-mediated glycolysis pathway in rats.

OBJECTIVE: Mesenchymal stem cells (MSCs) can treat osteoarthritis (OA), but their therapeutic efficacy is poor to date due to low migration efficiency. This study aimed to determine whether ultrasound-targeted microbubble destruction (UTMD) could ameliorate cartilage repair efficiency through facilitating the migration of MSCs via hypoxia-inducible factor-1α (HIF-1α)-mediated glycolysis regulatory pathway in OA model rats. METHODS: OA rats were treated with MSCs alone or in combination with UTMD, respectively, for 4 weeks. Cartilage histopathology, MSCs migration efficiency, von Frey fiber thresholds, and the expression levels of collagen II and MMP-13 were measured. Further, MSCs were extracted from the bone marrow of rats, cocultured with osteoarthritic chondrocytes, transfected to siRNA-HIF-1α, and subjected to UTMD for 4 days. Glucose consumption, lactate production, and cell migration efficiency were assessed. The protein expression levels of HIF-1α, HK2, PKM2, and GLUT1 were measured, respectively. RESULTS: In OA rat model, NC-MSCs + UTMD improved migration efficiency, increased collagen II expression, decreased MMP-13 expression, and delayed osteoarthritis progression. Silencing HIF-1α attenuated the effects induced by UTMD. In vitro, UTMD led to increases in MSC activity and migration, glucose consumption, lactate production, and the protein expression of HIF-1α, HK2, PKM2, and GLUT1 expression, all of which were reversed upon HIF-1α silencing. CONCLUSION: UTMD enhances MSCs migration and improves cartilage repair efficiency through the HIF-1α-mediated glycolytic regulatory pathway, providing a novel therapy strategy for knee osteoarthritis.

Biologically Active Micropatterns of Biomolecules and Living Matter Using Microbubble Lithography.

In situ patterning of biomolecules and living organisms while retaining their biological activity is extremely challenging, primarily because such patterning typically involves thermal stresses that could be substantially higher than the physiological thermal or stress tolerance level. Top-down patterning approaches are especially prone to these issues, while bottom-up approaches suffer from a lack of control in developing defined structures and the time required for patterning. A microbubble generated and manipulated by optical tweezers (microbubble lithography) is used to self-assemble and pattern living organisms in continuous microscopic structures in real-time, where the material thus patterned remains biologically active due to their ability to withstand elevated temperatures for short exposures. Successful patterns of microorganisms (Escherichia coli, Lactococcus. lactis and the Type A influenza virus) are demonstrated, as well as reporter proteins such as green fluorescent protein (GFP) on functionalized substrates with high signal-to-noise ratio and selectivity. Together, the data presented herein may open up fascinating possibilities in rapid in situ parallelized diagnostics of multiple pathogens and bioelectronics.

Fabrication of porous poly(L-lactide-co-ε-caprolactone) micropowder for microbubble effect and ultrasound-mediated drug delivery.

Biodegradable elastic poly(L-lactide-co-ε-caprolactone) (PLCL) copolymer (50:50, lactide:caprolactone molar ratio) was synthesized and porous PLCL micropowders was fabricated by a simple method involving rapid cooling of 0.1, 0.5, and 1% (wt/vol) PLCL/dioxane spray into liquid nitrogen. The physicochemical properties of the porous PLCL micropowders were examined by measuring their pore size, pore morphology, and microbead size using a scanning electron microscopy (SEM) and dye and temozolomide (TMZ)-release testing under ultrasound. Human U-87MG, glioblastoma (GBM) cell culture tests were performed to evaluate cell cytotoxicity by released drug from PLCL micropowders. In this study, the porous PLCL micropowders prepared from 1 wt%/vol% PLCL solutions showed a highly porous structure, satisfactory mechanical properties, and optimal drug release efficiency compared with those produced from 0.1 or 0.5 wt%/vol% solutions. The results of the accumulated release test with the results of the absorbance of the dye initially applied, it was confirmed that more than 80% of the added dye was trapped inside the micropowder, and clearly GBM cytotoxicity effect could be observed by the released TMZ. The drug release system using micropowders and ultrasound can be applied as a drug supply system for various diseases such as brain tumors with low drug permeability.

Novel treatment system using endoscopic ultrasound-guided high-intensity focused ultrasound: A proof-of-concept study.

AIM: High-intensity focused ultrasound (HIFU) is a novel minimally invasive local treatment of solid tumors. Endoscopic ultrasound-guided HIFU (EUS-HIFU) using mechanical effects would have potential benefits, including precise detection of target lesions and enhance drug delivery. The aim of this study is to develop EUS-HIFU device and to prove our concept in porcine model using a locally injected phase change nano droplet (PCND) as the sensitizer. METHOD: A phospholipid PCND contained volatile perfluoro-carbon liquids. The prototype HIFU apparatus comprised a small (20 × 20 mm) transducer with center frequency of 2.1 MHz, attachable to a linear EUS transducer. Under general anesthetic, a single porcine received EUS-guided injection of PCND. The HIFU transducer was placed laparotomically in the stomach, and the liver was ablated through the gastric wall. RESULTS: PCND was injected successfully and a distinct lesion was generated at the HIFU transducer focus only in injected areas that received HIFU exposure at 4.7 kW/cm2 at a duty cycle of 5 % (mean temporal intensity, 0.245 kW/cm2) for 30 s. The generated lesions were mechanically fractionated in macroscopic view. CONCLUSION: The concept of transluminal HIFU ablation using novel EUS-HIFU system was proved in a porcine animal model. This novel treatment system has great potential for future cancer treatment although further investigation in more animals and different organs are warranted.

Strain in Hybrid Organic-Inorganic Metal Halide Perovskites Microstructures by Numerical Simulations.

Hybrid organic-inorganic metal halide perovskites (HOIPs) are promising materials for optoelectronics applications. Their optical and electrical properties can be controlled by strain engineering, that results from application of local elastic deformation or deposition on pre-patterned substrates acquiring a conformal 3D shape. Most interesting, their mechanical properties depend on their crystal structure, composition and dimensionality. We explore by numerical simulations the deformation of a selection of HOIPs comprising a broad range of elastic properties. We consider an axial symmetry with the formation of microdomes on flakes. Radial and vertical forces are considered, finding that the radial force is more effective to obtain large deformation. Large vertical displacement and strain is obtained for HOIPs with low stiffness. The layered nature of HOIPs, that are formed by inorganic layers of different thickness and organic spacers, is also investigated, revealing a non-monotonous trend with the proportion of inorganic to organic part.

Delivery of Anticancer Drugs Using Microbubble-Assisted Ultrasound in a 3D Spheroid Model.

Tumor spheroids are promising three-dimensional (3D) in vitro tumor models for the evaluation of drug delivery methods. The design of noninvasive and targeted drug methods is required to improve the intratumoral bioavailability of chemotherapeutic drugs and reduce their adverse off-target effects. Among such methods, microbubble-assisted ultrasound (MB-assisted US) is an innovative modality for noninvasive targeted drug delivery. The aim of the present study is to evaluate the efficacy of this US modality for the delivery of bleomycin, doxorubicin, and irinotecan in colorectal cancer (CRC) spheroids. MB-assisted US permeabilized the CRC spheroids to propidium iodide, which was used as a drug model without affecting their growth and viability. Histological analysis and electron microscopy revealed that MB-assisted US affected only the peripheral layer of the CRC spheroids. The acoustically mediated bleomycin delivery induced a significant decrease in CRC spheroid growth in comparison to spheroids treated with bleomycin alone. However, this US modality did not improve the therapeutic efficacy of doxorubicin and irinotecan on CRC spheroids. In conclusion, this study demonstrates that tumor spheroids are a relevant approach to evaluate the efficacy of MB-assisted US for the delivery of chemotherapeutics.

Evaluation of tumor microvasculature with 3D ultrasound localization microscopy based on 2D matrix array.

OBJECTIVE: Evaluation of tumor microvascular morphology is of great significance in tumor diagnosis, therapeutic effect prediction, and surgical planning. Recently, two-dimensional ultrasound localization microscopy (2DULM) has demonstrated its superiority in the field of microvascular imaging. However, it suffers from planar dependence and is unintuitive. We propose a novel three-dimensional ultrasound localization microscopy (3DULM) to avoid these limitations. METHODS: We investigated 3DULM based on a 2D array for tumor microvascular imaging. After intravenous injection of contrast agents, all elements of the 2D array transmit and receive signals to ensure a high and stable frame rate. Microbubble signal extraction, filtering, positioning, tracking, and other processing were used to obtain a 3D vascular map, flow velocity, and flow direction. To verify the effectiveness of 3DULM, it was validated on double helix tubes and rabbit VX2 tumors. Cisplatin was used to verify the ability of 3DULM to detect microvascular changes during tumor treatment. RESULTS: In vitro, the sizes measured by 3DULM at 3 mm and 13 mm were 178 µ m and 182 µ m , respectively. In the rabbit tumors, we acquired 9000 volumes to reveal vessels about 30 µ m in diameter, which surpasses the diffraction limit of ultrasound in traditional ultrasound imaging, and the results matched with micro-angiography. In addition, there were significant changes in vascular density and curvature between the treatment and control groups. CONCLUSIONS: The effectiveness of 3DULM was verified in vitro and in vivo. Hence, 3DULM may have potential applications in tumor diagnosis, tumor treatment evaluation, surgical protocol guidance, and cardiovascular disease. CLINICAL RELEVANCE STATEMENT: 3D ultrasound localization microscopy is highly sensitive to microvascular changes; thus, it has clinical potential for tumor diagnosis and treatment evaluation. KEY POINTS: • 3D ultrasound localization microscopy is demonstrated on double helix tubes and rabbit VX2 tumors. • 3D ultrasound localization microscopy can reveal vessels about 30 µ m in diameter-far smaller than traditional ultrasound. • This form of imaging has potential applications in tumor diagnosis, tumor treatment evaluation, surgical protocol guidance, and cardiovascular disease.

Hydralazine loaded nanodroplets combined with ultrasound-targeted microbubble destruction to induce pyroptosis for tumor treatment.

Pyroptosis, a novel type of programmed cell death (PCD), which provides a feasible therapeutic option for the treatment of tumors. However, due to the hypermethylation of the promoter, the critical protein Gasdermin E (GSDME) is lacking in the majority of cancer cells, which cannot start the pyroptosis process and leads to dissatisfactory therapeutic effects. Additionally, the quick clearance, systemic side effects, and low concentration at the tumor site of conventional pyroptosis reagents restrict their use in clinical cancer therapy. Here, we described a combination therapy that induces tumor cell pyroptosis via the use of ultrasound-targeted microbubble destruction (UTMD) in combination with DNA demethylation. The combined application of UTMD and hydralazine-loaded nanodroplets (HYD-NDs) can lead to the rapid release of HYD (a demethylation drug), which can cause the up-regulation of GSDME expression, and produce reactive oxygen species (ROS) by UTMD to cleave up-regulated GSDME, thereby inducing pyroptosis. HYD-NDs combined with ultrasound (US) group had the strongest tumor inhibition effect, and the tumor inhibition rate was 87.15% (HYD-NDs group: 51.41 ± 3.61%, NDs + US group: 32.73%±7.72%), indicating that the strategy had a more significant synergistic anti-tumor effect. In addition, as a new drug delivery carrier, HYD-NDs have great biosafety, tumor targeting, and ultrasound imaging performance. According to the results, the combined therapy reasonably regulated the process of tumor cell pyroptosis, which offered a new strategy for optimizing the therapy of GSDME-silenced solid tumors.

Ultrasound Combined With Continuous Microbubble Injection to Enhance Catheter-Directed Thrombolysis in Vitro and in Vivo.

OBJECTIVES: To investigate the influence of microbubble perfusion mode on catheter-directed thrombolysis (CDT), we evaluated the effect of two different types of microbubble perfusion modes (continuous injection versus bolus injection) on the thrombolytic efficacy of CDT in vitro and further assessed the effect of continuous microbubble injection on CDT in vivo. METHODS: In an in vitro experimental setup, 50 fresh bovine whole blood clots were randomized into five groups: ultrasound and continuous microbubble injection-enhanced CDT (US + cMB + CDT), ultrasound and bolus microbubble injection-enhanced CDT (US + bMB + CDT), US + CDT, US + cMB, and CDT. In a porcine femoral vein thrombosis model, 16 completely obstructive thrombi were randomly assigned to the CDT group and the US + cMB + CDT group, respectively. Thrombolysis rate, vascular recanalization rate, hematoxylin-eosin, and immunofluorescence staining were used to evaluate the thrombolytic effect in vitro and in vivo. RESULTS: In vitro, US + cMB + CDT group resulted in a significantly higher thrombolysis rate compared with the other four groups (P < .05). Meanwhile, this group also demonstrated a looser clot structure and more disrupted fibrin structures. In vivo, US + cMB + CDT contributed to a significantly higher vascular recanalization rate compared with CDT (87.50% versus 25.00%, P < .05). CONCLUSIONS: US + cMB + CDT was more effective than US + bMB + CDT in thrombolysis, and ultrasound combined with continuous microbubble injection could enhance the thrombolytic efficacy of CDT.

Ultrasound-Induced Tumor Perfusion Changes and Doxorubicin Delivery: A Study on Pulse Length and Pulse Repetition Frequency.

OBJECTIVES: To investigate the appropriate combination of pulse length (PL) and pulse repetition frequency (PRF) when performing ultrasound stimulated microbubble (USMB) to enhance doxorubicin (DOX) delivery to tumors. METHODS: A total of 48 tumor-bearing mice were divided into four groups, namely groups A-D. The mice in groups B-D were treated with chemotherapy and USMB treatment with different combinations of PL and PRF, and group A was control. Contrast-enhanced ultrasound imaging was conducted to analyze tumor blood perfusion. Fluorescence microscopy and high-performance liquid chromatography were used to qualitatively and quantitatively analyse DOX release. The structural changes of tumors were observed under light microscope and transmission electron microscope. Furthermore, another 24 tumor-bearing mice were treated with sonochemotherapy and some related inflammatory factors were measured to explore the underlying mechanism. RESULTS: With PL of three cycles and PRF of 2 kHz, the tumor perfusion area ratio increased by 26.67%, and the DOX concentration was 4.69 times higher than the control (P < .001). With PL of 34.5 cycles and PRF of 200 Hz, the tumor perfusion area ratio decreased by 12.7% and DOX did not exhibit increased extravasation compared with the control. Microvascular rupture and hemorrhage were observed after long PL and low PRF treatment. While vasodilation and higher levels of some vasodilator inflammatory factors were found after treatment with short PL and high PRF. CONCLUSIONS: USMB treatment using short PL and high PRF could enhance tumor blood perfusion and increase DOX delivery, whereas long PL and low PRF could not serve the same purpose.

Microbubble Biointerfacing by Regulation of the Platelet Membrane Surfactant Activity at the Gas-Liquid Interface for Acute Thrombosis Targeting.

Biointerfacing nanomaterials with cell membranes has been successful in the functionalization of nanoparticles or nanovesicles, but microbubble functionalization remains challenging due to the unique conformation of the lipid monolayer structure at the gas-liquid interface that provides insufficient surfactant activity. Here, we describe a strategy to rationally regulate the surfactant activity of platelet membrane vesicles by adjusting the ratio of proteins to lipids through fusion with synthetic phospholipids (i.e., liposomes). A "platesome" with the optimized protein-to-lipid ratio can be assembled at the gas-liquid interface in the same manner as pulmonary surfactants to stabilize a microsized gas bubble. Platesome microbubbles (PMBs) inherited 61.4 % of the platelet membrane vesicle proteins and maintained the active conformation of integrin αIIbß3 without the talin 1 for fibrin binding. We demonstrated that the PMBs had good stability, long circulation, and superior functionality both in vitro and in vivo. Moreover, by molecular ultrasound imaging, the PMBs provide up to 11.8 dB of ultrasound signal-to-noise ratio enhancement for discriminating between acute and chronic thrombi. This surface tension regulating strategy may provide a paradigm for biointerfacing microbubbles with cell membranes, offering a potential new approach for the construction of molecular ultrasound contrast agents for the diagnosis of different diseases.

The involvement of transient receptor potential channels in mast cell activation by microbubbles.

This study was to explore the activation of mast cells by microbubbles, with the focus on transient receptor potential (TRP) channels mediated degranulation and calcium influx. Bone marrow-derived mast cells (BMMCs) were primarily obtained from femurs in mice and induced differentiation for 4 weeks. After the purity identification, BMMCs were contacted by homogeneous microbubbles with the diameter of 1 mm for 1 h. ß-hexosaminidase and histamine levels in supernatants were assessed by enzyme-linked immunosorbent assay (ELISA) and the CD63 expression was tested by flow cytometry. The intracellular calcium binding with Fluo-4 AM dyes in BMMCs was observed under the fluorescence microscope and the mean fluorescence intensity was quantitatively measured by flow cytometry. ß-hexosaminidase release, histamine concentration, CD63 expression and calcium influx were significantly increased in BMMCs group upon microbubble stimulation compared to the control groups. After preconditioning with the available inhibitors and microbubble contact, only transient receptor potential vanilloid 1 (TRPV1) and TRPV4 inhibitors robustly suppressed the microbubble-induced degranulation. Likewise, the elevated fluorescence intensity of cytosolic calcium level was also significantly weaken. The results demonstrated microbubble stimulus effectively promoted BMMCs degranulation, which could be substantially restrained by inhibitors targeted for blocking TRPV1 or TRPV4 channel. The alternation of intracellular calcium level in BMMCs was consistent with the changes of degranulation capacity. It's suggested that the activation of BMMCs by microbubbles may involve specific TRP calcium dependent channels.

Enhanced bone regeneration by low-intensity pulsed ultrasound and lipid microbubbles on PLGA/TCP 3D-printed scaffolds.

BACKGROUND: To investigate the effect of low-intensity pulsed ultrasound (LIPUS) combined with lipid microbubbles on the proliferation and bone regeneration of bone marrow mesenchymal stem cells (BMSCs) in poly (lactic-glycolic acid copolymer) (PLGA)/α-tricalcium phosphate (TCP) 3D-printed scaffolds. METHODS: BMSCs were irradiated with different LIPUS parameters and microbubble concentrations, and the best acoustic excitation parameters were selected. The expression of type I collagen and the activity of alkaline phosphatase were detected. Alizarin red staining was used to evaluate the calcium salt production during osteogenic differentiation. RESULTS: BMSCs proliferation was the most significant under the condition of 0.5% (v/v) lipid microbubble concentration, 2.0 MHz frequency, 0.3 W/cm2 sound intensity and 20% duty cycle. After 14 days, the type I collagen expression and alkaline phosphatase activity in the scaffold increased significantly compared to those in the control group, and alizarin red staining showed more calcium salt production during osteogenic differentiation. After 21 days, scanning electron microscopy experiments showed that osteogenesis was obvious in the PLGA/TCP scaffolds. CONCLUSION: LIPUS combined with lipid microbubbles on PLGA/TCP scaffolds can promote BMSCs growth and bone differentiation, which is expected to provide a new and effective method for the treatment of bone regeneration in tissue engineering.

Ultrasound and microbubble-mediated delivery of miR-424-5p has a therapeutic effect in preeclampsia.

OBJECTIVE: To determine the influence of ultrasound/microbubble-mediated miR-424-5p delivery on trophoblast cells and the underlying mechanism. METHODS: Blood pressure and 24-h proteinuria of patients with preeclampsia (PE) were measured as well as the levels of miR-424-5p and amine oxidase copper containing 1 (AOC1) in placental tissues. HTR-8/Svneo and TEV-1 cells were subjected to cell transfection or ultrasonic microbubble transfection for determination of the expression of miR-424-5p, AOC1, ß-catenin and c-Myc as well as cell proliferation, apoptosis, migration and invasiveness. The concentrations of placental growth factor (PLGF), human chorionic gonadotropin (ß-hCG) and tumor necrosis factor-α (TNF-α) were measured in HTR-8/Svneo and TEV-1 cells. RNA immunoprecipitation (RIP) and dual luciferase reporter assay detected the binding of miR-424-5p to AOC1. A PE mouse model was induced by subcutaneous injection of L-NAME, where the influence of ultrasound/microbubble-mediated miR-424-5p delivery was evaluated. RESULTS: miR-424-5p was downregulated while AOC1 was upregulated in the placental tissues from PE patients. Overexpression of miR-424-5p activated Wnt/ß-catenin signaling pathway and promoted the proliferation of HTR-8/Svneo and TEV-1 cells as well as enhanced the migratory and invasive behaviors. AOC1 overexpression partly eliminated the effects of miR-424-5p on HTR-8/Svneo and TEV-1 cells. Ultrasound and microbubble mediated gene delivery enhanced the transfection efficiency of miR-424-5p and further promoted the effects of miR-424-5p in trophoblast cells. Ultrasound/microbubble-mediated miR-424-5p delivery alleviated experimental PE in mice. CONCLUSION: Ultrasound and microbubble-mediated miR-424-5p delivery targets AOC1 and activates Wnt/ß-catenin signaling pathway, thus promoting the aggressive phenotype of trophoblast cells, which indicating that miR-424-5p/AOC1 axis might be involved with PE pathogenesis.

Enhanced Local Delivery of microRNA-145a-5P into Mouse Aorta via Ultrasound-Targeted Microbubble Destruction Inhibits Atherosclerotic Plaque Formation.

Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) play a key role in the formation and rupture of atherosclerotic plaques. Previous studies have confirmed that microRNA-145 (miR-145) is involved in the phenotypic regulation of VSMCs and reduction of atherosclerosis. At present, seeking safe and effective gene delivery remains a key problem restricting the development of gene therapy. In recent years, ultrasound-targeted microbubble destruction (UTMD) has become a safe and effective transfection method that is widely used in the basic research of gene therapy for heart and tumor diseases. Here, we synthesized cationic microbubbles to encapsulate miR-145 and targeted their release into VSMCs in vitro and in vivo using ultrasound. The feasibility of this gene therapy was verified by fluorescence microscopy and an in vivo imaging system. The results showed that treatment with miR-145 delivered via UTMD considerably improved the gene transfection efficiency and promoted the contraction phenotype of VSMCs in vitro. In vivo, this treatment reduced the atherosclerotic plaque area by 48.04% compared with treatment with free miR-145. Therefore, UTMD-mediated miRNA therapy may provide a new targeted therapeutic approach for atherosclerotic plaques.

Modeling Gasotransmitter Availability to Brain Capillary Endothelial Cells with Ultrasound-sensitive Microbubbles.

BACKGROUND: Vascular cognitive impairment and dementia results from blood components passing through disrupted blood brain barriers (BBBs). Current treatments can reduce further progress of neuronal damage but do not treat the primary cause. Instead, these treatments typically aim to temporarily disrupt the BBB. Alternatively, this study computationally assessed the feasibility of delivering carbon monoxide (CO) from ultrasound-sensitive microbubbles (MBs) as a strategy to promote BBB repair and integrity. CO can interact with heme-containing compounds within cells and promote cell growth. However, careful dose control is critical for safety and efficacy because CO also binds at high affinity to hemoglobin (Hb). METHODS: Ultrasound activation was simulated at the internal carotid artery, and CO released from the resulting MB rupture was tracked along the shortest path to the BBB for several activation times and doses. The CO dose available to brain capillary endothelial cells (BCECs) was predicted by considering hemodynamics, mass transport, and binding kinetics. RESULTS: The half-life of CO binding to Hb indicated that CO is available to interact with BCECs for several cardiac cycles. Further, MB and COHb concentrations would not be near toxic levels and free Hb would be available. The axisymmetric model indicated that biologically-relevant CO concentrations will be available to BCECs, and these levels can be sustained with controlled ultrasound activation. A patient-specific geometry shows that while vessel tortuosity provides a heterogeneous response, a relevant CO concentration could still be achieved. CONCLUSIONS: This computational study demonstrates feasibility of the CO / MB strategy, and that controlled delivery is important for viability of this strategy.

Diagnostic ultrasound-mediated microbubble cavitation dose-dependently improves diabetic cardiomyopathy through angiogenesis.

Ultrasound-mediated microbubble cavitation (UMMC) induces therapeutic angiogenesis to treat ischemic diseases. This study aimed to investigate whether diagnostic UMMC alleviates diabetic cardiomyopathy (DCM) and, if so, through which mechanisms. DCM model was established by injecting streptozocin into rats to induce hyperglycemia, followed by a high-fat diet. The combined therapy of cation microbubble with low-intensity diagnostic ultrasound (frequency = 4 MHz), with a pulse frequency of 20 Hz and pulse length (PL) of 8, 18, 26, or 36 cycles, was given to rats twice a week for 8 consecutive weeks. Diagnostic UMMC therapy with PL at 8, 18, and 26 cycles, but not 36 cycles, dramatically prevented myocardial fibrosis, improved heart functions, and increased angiogenesis, accompanied by increased levels of PI3K, Akt, and eNOS proteins in the DCM model of rats. In cultured endothelial cells, low-intensity UMMC treatment (PL = 3 cycles, sound pressure level = 50%, mechanical index = 0.82) increased cell viability and activated PI3K-Akt-eNOS signaling. The combination of diagnostic ultrasound with microbubble destruction dose-dependently promoted angiogenesis, thus improving heart function through PI3K-Akt-eNOS signaling in diabetes. Accordingly, diagnostic UMMC therapy should be considered to protect the heart in patients with diabetes.

Focused ultrasound-mediated blood-brain barrier opening combined with magnetic targeting cytomembrane based biomimetic microbubbles for glioblastoma therapy.

Glioblastoma is the most common type of brain tumor. Due to the presence of the blood-brain barrier, the effects of chemotherapy have been unsatisfactory. The combination of focused ultrasound and microbubbles to reversibly open the blood-brain barrier is now considered a key factor in improving treatment outcomes of glioblastoma. In this study, we developed bionic drug delivery microbubbles, which in combination with focused ultrasound had an obvious inhibitory effect on glioblastoma. We extracted the brain microvascular cell membranes, combined them with lipid components, and loaded them with superparamagnetic iron oxide and doxorubicin to prepare biomimetic drug delivery microbubbles (FeDOX@cellMBs). We demonstrated that FeDOX@cellMBs retained the intrinsic properties of loading, such as magnetic properties and drug toxicity, both in vitro and in vivo. FeDOX@cellMBs exhibited good tumor targeting and uptake under the combined action of magnetic and focused ultrasound. Importantly, the FeDOX@cellMBs demonstrated excellent internal stability and effectively inhibited tumor growth in orthotopic glioblastoma mice. Finally, organ H&E staining confirmed that FeDOX@cellMBs were safe for use. In conclusion, FeDOX@cellMBs successfully penetrated the blood-brain barrier and effectively inhibited glioblastoma growth under the combined effects of focused ultrasound and magnetic stimulation. These results provide a new approach for the treatment of glioblastoma, with implications for future clinical translation.

Ultrasound-targeted microbubble destruction promotes PDGF-primed bone mesenchymal stem cell transplantation for myocardial protection in acute Myocardial Infarction in rats.

BACKGROUND: Ultrasound-targeted microbubble destruction (UTMD) has emerged as a promising strategy for the targeted delivery of bone marrow mesenchymal stem cells (MSCs) to the ischemic myocardium. However, the limited migration capacity and poor survival of MSCs remains a major therapeutic barrier. The present study was performed to investigate the synergistic effect of UTMD with platelet-derived growth factor BB (PDGF-BB) on the homing of MSCs for acute myocardial infarction (AMI). METHODS: MSCs from male donor rats were treated with PDGF-BB, and a novel microbubble formulation was prepared using a thin-film hydration method. In vivo, MSCs with or without PDGF-BB pretreatment were transplanted by UTMD after inducing AMI in experimental rats. The therapeutic efficacy of PDGF-BB-primed MSCs on myocardial apoptosis, angiogenesis, cardiac function and scar repair was estimated. The effects and molecular mechanisms of PDGF-BB on MSC migration and survival were explored in vitro. RESULTS: The results showed that the biological effects of UTMD increased the local levels of stromal-derived factor-1 (SDF-1), which promoted the migration of transplanted MSCs to the ischemic region. Compared with UTMD alone, UTMD combined with PDGF-BB pretreatment significantly increased the cardiac homing of MSCs, which subsequently reduced myocardial apoptosis, promoted neovascularization and tissue repair, and increased cardiac function 30 days after MI. The vitro results demonstrated that PDGF-BB enhanced MSC migration and protected these cells from H2O2-induced apoptosis. Mechanistically, PDGF-BB pretreatment promoted MSC migration and inhibited H2O2-induced MSC apoptosis via activation of the phosphatidylinositol 3-kinase/serine-threonine kinase (PI3K/Akt) pathway. Furthermore, crosstalk between PDGF-BB and stromal-derived factor-1/chemokine receptor 4 (SDF-1/CXCR4) is involved in the PI3K/AKT signaling pathway. CONCLUSION: The present study demonstrated that UTMD combined with PDGF-BB treatment could enhance the homing ability of MSCs, thus alleviating AMI in rats. Therefore, UTMD combined with PDGF-BB pretreatment may offer exciting therapeutic opportunities for strengthening MSC therapy in ischemic diseases.