Penetration of different molecule sizes upon ultrasound combined with microbubbles in a superficial tumour model

Regulation of IFP in solid tumours through acoustic pressure to enhance infiltration of nanoparticles of various sizes

Numerous nanomedicines have been developed recently that can accumulate selectively in tumours due to the enhanced permeability and retention (EPR) effect. However, the high interstitial fluid pressure (IFP) in solid tumours limits the targeted delivery of nanomedicines. We were previously able to relieve intra-tumoural IFP by low-frequency non-focused ultrasound (LFNFU) through ultrasonic targeted microbubble destruction (UTMD), improving the targeted delivery of FITC-dextran. However, the accumulation of nanoparticles of different sizes and the optimal acoustic pressure were not evaluated. In this study, we synthesised Cy5.5-conjugated mesoporous silica nanoparticles (Cy5.5-MSNs) of different sizes using a one-pot method. The Cy5.5-MSNs exhibited excellent stability and biosafety regardless of size. MCF7 tumour-bearing mice were subjected to UTMD over a range of acoustic pressures (0.5, 0.8, 1.5 and 2.0 MPa), and injected intravenously with Cy5.5-MSNs. Blood perfusion, tumour IFP and intra-tumoural accumulation of Cy5.5-MSNs were analysed. Blood perfusion and IFP initially rose, and then declined, as acoustic pressure intensified. Furthermore, UTMD significantly enhanced the accumulation of differentially sized Cy5.5-MSNs in tumour tissues compared to that of the control group, and the increase was sevenfold higher at an acoustic pressure of 1.5 MPa. Taken together, UTMD enhanced the infiltration and accumulation of Cy5.5-MSNs of different sizes in solid tumours by reducing intra-tumour IFP.

Role of microRNA-505 during tumor progression and metastasis

Late diagnosis of cancer in advanced stages due to the lack of screening methods is considered as the main cause of poor prognosis and high mortality rate among these patients. Therefore, it is necessary to investigate the molecular tumor biology in order to introduce biomarkers that can be used in cancer screening programs and early diagnosis. MicroRNAs (miRNAs) have key roles in regulation of the cellular pathophysiological processes. Due to the high stability of miRNAs in body fluids, they are widely used as the non-invasive tumor markers. According to the numerous reports about miR-505 deregulation in a wide range of cancers, we investigated the role of miR-505 during tumor progression. It was shown that miR-505 mainly has the tumor suppressor functions through the regulation of signaling pathways, chromatin remodeling, and cellular metabolism. This review has an effective role in introducing miR-505 as a suitable marker for the early cancer diagnosis.

Mechanistic study of ultrasound and microbubble enhanced cancer therapy in a 3D vascularized microfluidic cancer model

Accumulating evidence has shown that ultrasound exposure combined with microbubbles can enhance cancer therapy. However, the underlying mechanisms at the tissue level have not been fully understood yet. The conventional cell culture in vitro lacks complex structure and interaction, while animal studies cannot provide micron-scale dynamic information. To bridge the gap, we designed and assembled a 3D vascularized microfluidic cancer model, particularly suitable for ultrasound and microbubble involved mechanistic studies. Using this model, we first studied SonoVue microbubble traveling dynamics in 3D tissue structure, then resolved SonoVue microbubble cavitation dynamics in tissue mimicking agarose gels at a frame rate of 0.675 M fps, and finally explored the impacts of ultrasound and microbubbles on cancer cell spheroids. Our results demonstrate that microbubble penetration in agarose gel was enhanced by increasing microbubble concentration, flow rate and decreasing viscosity of the gel, and little affected by mild acoustic radiation force. SonoVue microbubble exhibited larger expansion amplitudes in 2 %(w/v) agarose gels than in water, which can be explained theoretically by the relaxation of the cavitation medium. The immediate impacts of ultrasound and SonoVue microbubbles to cancer cell spheroids in the 3D tissue model included improved cancer cell spheroid penetration in micron-scale and sparse direct permanent cancer cell damage. Our study provides new insights of the mechanisms for ultrasound and microbubble enhanced cancer therapy at the tissue level.

Microbubbles for human diagnosis and therapy

Microbubbles (MBs) were observed for the first time in vivo as a curious consequence of quick saline injection during ultrasound (US) imaging of the aortic root, more than 50 years ago. From this serendipitous event, MBs are now widely used as contrast enhancers for US imaging. Their intrinsic properties described in this review, allow a multitude of designs, from shell to gas composition but also from grafting targeting agents to drug payload encapsulation. Indeed, the versatile MBs are deeply studied for their dual potential in imaging and therapy. As presented in this paper, new generations of MBs now opens perspectives for targeted molecular imaging along with the development of new US imaging systems. This review also presents an overview of the different therapeutic strategies with US and MBs for cancer, cardiovascular diseases, and inflammation. The overall aim is to overlap those fields in order to find similarities in the MBs application for treatment enhancement associated with US. To conclude, this review explores the new scales of MBs technologies with nanobubbles development, and along concurrent advances in the US imaging field. This review ends by discussing perspectives for the booming future uses of MBs.

Microbubbles Ultrasonic Cavitation Regulates Tumor Interstitial Fluid Pressure and Enhances Sonodynamic Therapy

Sonodynamic therapy (SDT) is a promising treatment method for solid tumors. However, the high interstitial fluid pressure (IFP) in tumor tissues limits the accumulation of sonosensitizers. In the present study, microbubbles ultrasonic cavitation was used to regulate the tumor’s IFP and evaluate SDT effects. Rabbit VX2 tumor tissues were treated with microbubbles ultrasonic cavitation. The IFP of different tumor parts before and after cavitation was measured by the WIN method. The accumulation of the sonosensitizers hematoporphyrin monomethyl ether (HMME) in tumor tissues was observed using an ultramicro spectrophotometer and laser confocal microscope. Then, tumor-bearing rabbits were treated with SDT once a week for eight weeks and the therapeutic effect was evaluated. After microbubbles ultrasonic cavitation treatment, the tumor’s IFP decreased and the HMME concentration increased. We concluded that microbubbles ultrasonic cavitation can increase HMME accumulation in rabbit VX2 tumors and increase SDT therapeutic effects.

Appropriate Size of Fe3O4 Nanoparticles for Cancer Therapy by Ferroptosis

Iron oxide nanoparticles can induce cell death due to the ferroptosis mechanism, showing a great potential for cancer therapy. Here, we synthesized different-sized iron oxide nanoparticles (2-100 nm) to investigate their antitumor effect and toxicity mechanism. It was found that ultrasmall nanoparticles (< ∼5 nm) could accumulate in nucleus and were more efficient in triggering the generation of ^•OH than larger nanoparticles due to the quicker release of Fe²⁺, thus exhibiting more remarkable cytotoxicity. Nevertheless, 10 nm iron oxide nanoparticles group displayed the best antitumor effect in vivo. We studied the in vivo and intratumoral biodistribution of the nanoparticles and found that the therapeutic effects were related to both the tumoral accumulation and intratumoral distribution of nanoparticles. This work indicates the appropriate size of Fe₃O₄ NPs for cancer treatment and illustrates the possible factors that influence the therapeutic effect, suggesting the great potential of iron oxide in clinical application.

The influence of hyperglycemia on the safety of ultrasound in retinal pigment epithelial cells

Ultrasound (US) assisted drug delivery is receiving interest in treating posterior eye diseases, such as diabetic retinopathy due to its ability to maximize drug penetration into difficult to reach tissues. Despite its promise, the technique has only been investigated using healthy cell and tissue models, with no evidence to date about its safety in active disease. As a result, the aim of this study was to evaluate the safety of US administration in vitro in retinal pigment epithelial cells under normal and high glucose conditions. US protocols within the presently accepted safety threshold were applied and their influence on cell membrane and tight junction integrity as well as intracellular inflammation was evaluated using lactate dehydrogenase (LDH), zona occludens-1 (ZO-1), fluorescein isothiocyanate (FITC)-dextran dye leak and nuclear factor-kappaB (NF-κB) assays, respectively. Under high glucose conditions, US application increased LDH release and resulted in loss of ZO-1 labeling at 2 h; however, normal levels were restored within 24 h. US within its safety parameters did not induce any FITC-dextran dye leak or NF-κB nuclear translocation in normal or high glucose conditions. In conclusion, our results suggest that while high glucose conditions increase cell susceptibility to US-mediated stress, basal conditions can be restored within 24 h without long-lasting cell damage.

Ultrasound Microbubble-Mediated microRNA-505 Regulates Cervical Cancer Cell Growth via AKT2

The application of ultrasound and microbubbles (USMB-) mediated microRNA (miR) is a promising approach of gene delivery for cancer treatment. We aimed to discuss the effects of USMB-miR-505 on cervical cancer (CC) development. miR-505 mediated by USMB was prepared. The effect of miR-505 on its transfection efficiency and the effect of miR-505 on HeLa cell proliferation, cell cycle, apoptosis, migration, and invasion were studied. The target gene of miR-505 was predicted, and its expression in CC was detected. The effect of the target gene on HeLa cells was further verified. USMB-miR-505 showed a higher transfection efficiency than miR-505 alone. The inhibitory effect of miR-505 mediated by USMB on HeLa cells was better than miR-505. miR-505 targeted AKT2, which was upregulated in CC. Overexpression of AKT2 reversed the inhibitory effect of USMB-miR-505 on HeLa cell malignant behaviors. Overall, we highlighted that USMB-miR-505 inhibited HeLa cell malignant behaviors by targeting AKT2.

Improving the Therapeutic Effect of Ultrasound Combined With Microbubbles on Muscular Tumor Xenografts With Appropriate Acoustic Pressure

Ultrasound combined with microbubbles (USMB) is a promising antitumor therapy because of its capability to selectively disrupt tumor perfusion. However, the antitumor effects of repeated USMB treatments have yet to be clarified. In this study, we established a VX2 muscular tumor xenograft model in rabbits, and performed USMB treatments at five different peak negative acoustic pressure levels (1.0, 2.0, 3.0, 4.0, or 5.0 MPa) to determine the appropriate acoustic pressure. To investigate whether repeated USMB treatments could improve the antitumor effects, a group of tumor-bearing rabbits was subjected to one USMB treatment per day for three consecutive days for comparison with the single-treatment group. Contrast-enhanced ultrasonic imaging and histological analyses showed that at an acoustic pressure of 4.0 MPa, USMB treatment contributed to substantial cessation of tumor perfusion, resulting in severe damage to the tumor cells and microvessels without causing significant effects on the normal tissue. Further, the percentages of damaged area and apoptotic cells in the tumor were significantly higher, and the tumor growth inhibition effect was more obvious in the multiple-treatment group than in the single USMB treatment group. These findings indicate that with an appropriate acoustic pressure, the USMB treatment can selectively destroy tumor vessels in muscular tumor xenograft models. Moreover, the repeated treatments strategy can significantly improve the antitumor effect. Therefore, our results provide a foundation for the clinical application of USMB to treat solid tumors using a novel therapeutic strategy.

Ultrasound-Responsive Cavitation Nuclei for Therapy and Drug Delivery

Therapeutic ultrasound strategies that harness the mechanical activity of cavitation nuclei for beneficial tissue bio-effects are actively under development. The mechanical oscillations of circulating microbubbles, the most widely investigated cavitation nuclei, which may also encapsulate or shield a therapeutic agent in the bloodstream, trigger and promote localized uptake. Oscillating microbubbles can create stresses either on nearby tissue or in surrounding fluid to enhance drug penetration and efficacy in the brain, spinal cord, vasculature, immune system, biofilm or tumors. This review summarizes recent investigations that have elucidated interactions of ultrasound and cavitation nuclei with cells, the treatment of tumors, immunotherapy, the blood-brain and blood-spinal cord barriers, sonothrombolysis, cardiovascular drug delivery and sonobactericide. In particular, an overview of salient ultrasound features, drug delivery vehicles, therapeutic transport routes and pre-clinical and clinical studies is provided. Successful implementation of ultrasound and cavitation nuclei-mediated drug delivery has the potential to change the way drugs are administered systemically, resulting in more effective therapeutics and less-invasive treatments.

Recent Progress of Potentiating Immune Checkpoint Blockade with External Stimuli-an Industry Perspective

The past decade has seen the materialization of immune checkpoint blockade as an emerging approach to cancer treatment. However, the overall response and patient survival are still modest. Various efforts to study the "cancer immunogram" have highlighted complex biology that necessitates a multipronged approach. This includes increasing the antigenicity of the tumor, strengthening the immune infiltration in the tumor microenvironment, removing the immunosuppressive mechanisms, and reducing immune cell exhaustion. The coordination of these approaches, as well as the ability to enhance them through delivery, is evaluated. Due to their success in multiple preclinical models, external-stimuli-responsive nanoparticles have received tremendous attention. Several studies report success in distantly located tumor regression, metastases, and reoccurrence in preclinical mouse models. However, clinical translation in this space remains low. Herein, the recent advancement in external-stimuli-responsive nanoconstruct-synergized immune checkpoint blockade is summarized, offering an industry perspective on the limitations of current academic innovations and discussing challenges in translation from a technical, manufacturing, and regulatory perspective. These limitations and challenges will need to be addressed to establish external-stimuli-based therapeutic strategies for patients.

Nano-Enhanced Drug Delivery and Therapeutic Ultrasound for Cancer Treatment and Beyond

While ultrasound is most widely known for its use in diagnostic imaging, the energy carried by ultrasound waves can be utilized to influence cell function and drug delivery. Consequently, our ability to use ultrasound energy at a given intensity unlocks the opportunity to use the ultrasound for therapeutic applications. Indeed, in the last decade ultrasound-based therapies have emerged with promising treatment modalities for several medical conditions. More recently, ultrasound in combination with nanomedicines, i.e., nanoparticles, has been shown to have substantial potential to enhance the efficacy of many treatments including cancer, Alzheimer disease or osteoarthritis. The concept of ultrasound combined with drug delivery is still in its infancy and more research is needed to unfold the mechanisms and interactions of ultrasound with different nanoparticles types and with various cell types. Here we present the state-of-art in ultrasound and ultrasound-assisted drug delivery with a particular focus on cancer treatments. Notably, this review discusses the application of high intensity focus ultrasound for non-invasive tumor ablation and immunomodulatory effects of ultrasound, as well as the efficacy of nanoparticle-enhanced ultrasound therapies for different medical conditions. Furthermore, this review presents safety considerations related to ultrasound technology and gives recommendations in the context of system design and operation.