Microbubbles for human diagnosis and therapy

Dual-responsive nanoscale ultrasound contrast agent as an oxidative stress amplifier for enhanced DNA damage in BRCA-proficient ovarian cancer

PARP inhibitor (PARPi)-based synthetic lethal therapies have displayed limited benefits in BRCA-proficient ovarian cancer. To potentiate the application of PARPi, an ultrasound contrast agent OLA-NDs for delivery of the PARPi olaparib (OLA) was established for enhancing DNA damage by blocking DNA repair. OLA-NDs were endowed with endogenous pH- and exogenous ultrasound (US)-responsiveness to target tumors, as well as contrast-enhanced US imaging for diagnostic and therapeutic integration. OLA-NDs could upregulate NOX4 to induce oxidative stress and sensitize BRCA wild-type A2780 cells to DNA oxidative damage through the utilization of ultrasound-targeted microbubble destruction (UTMD). In addition, the strategy further increased ROS production by interfering with mitochondrial function, thereby exacerbating DNA double-strand breaks (DSBs) and inducing mitochondria-mediated apoptosis. As a consequence, the combined application of UTMD and OLA-NDs demonstrated significant antitumor effects in vitro and in vivo. This combined strategy of amplifying oxidative damage improved lethality by promoting DNA DSBs and apoptosis with reduced adverse side effects, which would provide new insight for the clinical application of PARPi in BRCA-proficient ovarian cancer.

Interaction effects on acoustic emissions of submicron ultrasound contrast agents at subharmonic resonances

Submicron ultrasound contrast agents hold great potential to extend the bubble-mediated theranostics beyond the vasculature, but their acoustic response and the interaction effects between them remain poorly understood. This study set out to numerically examine the interaction effects on the subharmonic oscillations of nanobubbles and the resultant acoustic emissions under subharmonic resonance conditions. Results showed that a negative correlation between bubble size and subharmonic resonance frequency is readily obtained from the radius response curves. Moreover, it was also found that the larger nanobubble in a two-nanobubble system generally acts as the primary determinant for the subharmonic oscillations of the smaller one. Specifically, a larger nanobubble excited at its subharmonic resonance conditions can force a smaller nanobubble to undergo subharmonic oscillations, resulting in the generation of subharmonic acoustic emissions. Conversely, under specific resonance conditions, a smaller nanobubble undergoing subharmonic oscillations can also be restrained by a larger nanobubble that is off-resonance and consequently its subharmonic component disappears. Furthermore, it also clearly demonstrated that the generation of subharmonic resonance is pressure threshold dependent and the subharmonic resonant radius is distinctly reduced as the acoustic pressure increases. By contrast, a larger nanobubble has a lower pressure threshold than that of a smaller one, when subjected to their subharmonic resonance conditions respectively. More importantly, the higher pressure threshold of a smaller nanobubble can be prominently decreased by the interaction effects from a nearby larger nanobubble. For two interacting nanobubbles, the interaction effects strongly depend on the inter-bubble distance, and the farther the two nanobubbles is, the weaker the interaction effects become and even can be ignored. Additionally, the impacts of the lipid shell properties indicated that increasing shell viscoelasticity can increase the subharmonic resonant radius but dampen the subharmonic oscillations and the resultant acoustic emissions, which is more sensitive to the shell viscosity. This study can contribute to a better understanding of the complex interaction effects between submicron ultrasound contrast agents on the resultant acoustic emissions, potentially advancing nanobubble-specific ultrasound applications.

Free gas micro-/nano-bubble water: a novel dispersion system to prepare ultrasound imaging vehicles

OBJECTIVES

Free gas micro-/nano-bubbles (MNBs) in water have demonstrated significant potential in various industrial applications, including water treatment, enhanced transport processes, and disinfection. However, the feasibility of utilizing MNBs water as a dispersed system for preparing ultrasound imaging vehicles is seldom explored. This study aims to investigate the potential of MNBs water for this purpose.

METHODS

Initially, MNBs water containing sulfur hexafluoride (SF6) was prepared and characterized. Subsequently, the potential of SF6 MNBs water to form lipid-shelled bubbles for ultrasound imaging was evaluated. This involved the incubation of lyophilized phospholipids with SF6 MNBs water.

RESULTS

The study confirmed the presence of SF6 MNBs in water. Through the incubation process, it was possible to obtain lipid-shelled bubbles with a nano-sized and narrow size distribution. These bubbles exhibited comparable echogenicity to those produced by conventional mechanical agitation methods during the initial 5 min of in vitro observation.

CONCLUSIONS

SF6 MNBs water represents a novel dispersion medium for generating nano-sized lipid-shelled bubbles. This approach offers a promising new method for extravascular ultrasound imaging and drug delivery, potentially expanding the applications of MNBs in medical imaging and therapeutic delivery systems.

Frequency-Selective Microbubble Targeting In Vitro: A Step Toward Multicolor Ultrasound Molecular Imaging

Ultrasound molecular imaging (USMI) utilizing targeted microbubbles (tMBs) and primary acoustic radiation force (Frad) pulses has demonstrated enhanced sensitivity in recent studies. However, current USMI techniques are limited to a single ligand-receptor pair per imaging scan. With the advent of the buried-ligand architecture (BLA), "cloaked" ligand-receptor binding and tMB adhesion can be activated by Frad pulses, enabling multicolor USMI. This approach permits the selective activation of two or more tMB species, each binding to its cognate receptors based on distinct resonance frequencies (f0) tuned by Frad pulses. The goal of this study was to demonstrate frequency-selective tMB adhesion to receptor-bearing microvessel tubes in vitro. Size-isolated BLA tMBs of 1 and 5 μm diameter were synthesized with f0 equal to 7 and 4 MHz, respectively (within the frequency limits of our ultrasound probe). The 1 μm tMBs were conjugated with IELLQAR peptide for P-selectin targeting, while the 5 μm tMBs were conjugated with cyclo-RGD peptide for αvβ3 integrin targeting. The MB gas volume fraction (φMB) was used to unify size and concentration into a single parameter. Frequency-selective tMB binding was quantified using fluorescence microscopy. Specific targeting was evaluated by comparing RGD- or IELLQAR-MB attachment to control RAD- or nonligand-bearing MBs, respectively. The results confirmed specific frequency-selective targeting of the two tMB species to their cognate receptors when activated by Frad pulses at their respective f0, both individually and in a cocktail. In the cocktail population, φMB of RGD-MB targeting increased 18-fold at 4 MHz compared to 7 MHz, while IELLQAR-MB targeting φMB increased 5-fold at 7 MHz compared to 4 MHz. In conclusion, this study presents the first demonstration of frequency-selective targeting of two different receptor species by two different tMB species, representing a significant step toward multicolor USMI and the potential for simultaneous imaging of multiple biomarkers in vivo within a single scan.

Using ultrasound and microbubble to enhance the effects of conventional cancer therapies in clinical settings

It has been demonstrated in preclinical research that the administration of microbubbles with ultrasound can augment the proapoptotic sphingolipid pathway and enhance chemotherapy or radiation therapy-induced vascular endothelial disruption resulting in enhanced tumor cell death. Specifically, ultrasound-stimulated microbubbles (USMB) can increase blood vessel permeability facilitating the release of therapeutic substances in the target area. USMB can also serve as a potential radiation enhancing therapy as USMB exposure increases tumor cell death significantly as observed in preclinical models. Clinical studies have found the combination of USMB and these existing cancer therapies to be safe and also to be associated with greater tumor responses. USMB-based treatment can be applicable in a clinical setting using either ultrasound imaging or magnetic resonance imaging (MRI) guidance for precise treatment. In the latter, the ultrasound device is integrated into the MRI system platform for sonication to facilitate microbubble stimulation. In this review, we concisely present findings related to USMB and existing cancer therapies (chemotherapy and radiation therapy) in clinical trial settings. The possible underlying mechanism involved in USMB-enhanced chemotherapy or radiotherapy enhancement is also discussed. Lastly, the study concludes with some limitations and an examination of the future direction of these combined therapies.

Ultrasound-Triggered Oxygen Release System for Accelerating Wound Healing of Diabetic Foot Ulcers

Diabetic foot ulcer (DFU) is a common complication of chronic diabetes mellitus. Oxygen plays a critical role in the healing process of DFU wounds by promoting cell migration and neovascularization. However, clinical hyperbaric oxygen (HBO) therapy predominantly uses systemic oxygen administration, posing challenges in inadequate DFU local oxygen penetration and potential ectopic organs oxygen toxicity. To address these challenges, a strategy to encapsulate oxygen with lipid microbubbles (OMBs) and incorporate them into a body temperature-sensitive heparin-pluronic copolymer hydrogel (HP/OMBs) have been developed. HP/OMBs showed high biocompatibility both in vitro and in vivo. After in situ administration, oxygen can be released from HP/OMBs to the local deep site of the DFU wounds under ultrasound (US) triggering. Thus, given its biocompatibility and practicality, the combined action of HP/OMBs and the US has important translational value in accelerating diabetic chronic wound healing.

Microbubble enhanced ultrasound with low mechanical index promotes therapeutic angiogenesis in hind limb ischemia mouse model

BACKGROUND

Microbubble enhanced ultrasound (MEUS) can augment tissue perfusion by angiogenesis yet the best treatment ultrasound power in the initial ischemia period is uncertain.

PURPOSE

Considering the mechanical index (MI) is the most commonly used parameter for regulating diagnostic ultrasound power, here, we explored the effects of MEUS mediated by different MI on perfusion and sought to characterize the angiogenesis in the early stage of ischemia.

METHODS

Experiments were conducted on hind limb ischemia mouse model (HLI) and MEUS was administrated in the first week every other day following induction of HLI for four times. MEUS was conducted with a modified diagnostic ultrasound in combination with a lipid microbubble at 3 MHz and 21 cycles employing MI 0.3 (0.8 MPa), 0.7 (1.32 MPa) and 1.3 (2.78 MPa), respectively. Semi-quantitative visual score and blood perfusion quantitation by contrast-enhanced ultrasound were performed before each treatment. Hematoxylin-eosin staining and immunohistochemistry with CD31 were performed after four times treatment.

RESULTS

The results showed HLI mice in MI 0.3 mediated MEUS group longitudinally exhibited more blood perfusion in calf muscle and less visible necrosis compared to other experimental groups in the early stage. Additionally, diffused inflammatory cells with greater number of vessels in calf muscle were observed in MI 0.3 group.

CONCLUSIONS

Low MI mediated MEUS had significantly greater effects on augmenting muscle blood perfusion and reducing necrosis in the initial period after HLI surgery. These effects are most likely mediated by angiogenesis stimulated by low MI mediated MEUS.

Modifications of biological membranes, fat globules and liposomes promoted by cavitation processes. Consequences and applications

Cavitation-based technologies, such as ultrasound (or acoustic cavitation, AC) and hydrodynamic cavitation (HC), are gaining interest among green processing technologies due to their cost effectiveness in operation, toxic solvent use reduction, and ability to obtain superior processed products, compared to conventional methods. Both AC and HC generate bubbles, but their effects may differ and it is difficult to make comparisons as both are based on different phenomena and are subject to different operational variables. AC is one of the most used techniques in extraction and homogenization processes at the laboratory level. However, upscaling to an industrial level is hard. On the other hand, HC is based on the passage of the liquid through a constriction (orifice plate, Venturi, throttling valve), which causes an increase in liquid velocity at the expense of local pressure, forcing the pressure around the contraction below the threshold pressure that induces the formation of cavities. Some applications of cavitation technologies, such as the production of liposomes or lipid nanoparticles (LNPs) allow the generation of delivery systems for biomedical applications.Many others (inactivation of pathogenic viruses, bacteria and algae for water purification, extraction procedures, third generation of biofuel production, green extractions) are based on the disruption of lipid membranes. There are also applications aimed at the modification of membranes (like the milk fat globule) for the development of innovative products. Process parameters, such as cavitation intensity, duration and temperature define the impact of the process on the physical, chemical, and biological characteristics of the membranes. Thus, the adequate implementation of cavitation processes requires understanding of interactions and synergistic mechanisms in complex systems and of their effects on membranes at the microscopic or molecular level. In the present work, the use of cavitation technologies for the generation of LNPs or nanostructured lipid carriers, and the effects of AC and HC treatments on several types of membrane systems (liposomes, solid lipid nanoparticles, milk fat globules, algae and bacterial membranes) are discussed, focusing on the structural and chemical modifications of lipidic structures under cavitation.

Flexible deformation and special interface structure in nanoparticle-stabilized Pickering bubbles strengthen the immunological response as adjuvant

Adjuvants can enhance an immunological response, which is an important part of vaccine research. Pickering bubbles have been a mega-hit for biomedical applications, including in vivo visualization and targeted drug delivery. However, there have been no studies on Pickering bubbles as an immunological adjuvant, and the special properties and structures of Pickering bubbles may play an important role in immunization. In this study, poly(lactic-co-glycolic acid) (PLGA) particles were used to construct nanoparticle-stabilized Pickering bubbles (PPBs). PPBs were evaluated as immunological adjuvants based on immune response effects and mechanisms and aiming at future applications. PPBs have a flexible gas core and a special surface structure that can increase the cell contact area to promote phagocytosis and enhance the immune response. Quartz crystal microbalance with dissipation (QCM-D) data showed the flexibility of PPBs, and confocal images captured the deformability of PPBs during cell uptake. Flow cytometry and antibody titer detection showed that PPBs significantly promoted antigen uptake and activation of bone-marrow-derived dendritic cells (BMDCs) and induced an immune response with upregulated SIINFEKL MHC I and CD127 molecules on the surface of CD8+ T cells, indicating excellent antigen cross-presentation and cellular immune triggering effects. The upregulation of CD44 and CD62L on CD4+ T cells and the IgG2a/IgG1 ratio bias further demonstrated the excellent adjuvant role of PPBs in immunity. Finally, the biosafety of PPBs as an immunological adjuvant was also demonstrated. Our study demonstrates the potential of particle-stabilized bubbles as immune adjuvants, which provides innovative ideas for vaccine development and design.

Harnessing Ultrasonic Technologies to Treat Staphylococcus Aureus Skin Infections

The rise of antibiotic-resistant Staphylococcus aureus strains, particularly MRSA, complicates the management of skin and soft tissue infections. This review highlights ultrasonic methodologies as adjunctive therapies to combat S. aureus-driven skin infections and prevent progression to biofilm formation and chronic wounds. Low- and high-frequency ultrasound (LFU and HFU) demonstrate potential in disrupting biofilms, enhancing drug delivery, and promoting tissue repair through cavitation and microbubble activity. These approaches integrate ultrasonic frequencies with microbubbles and therapeutics, such as antibiotics and affimers, to minimize resistance and improve healing. Tailoring the bioeffects of ultrasound on skin structures through localized delivery technologies, including microneedle patches and piezoelectric systems, presents promising solutions for early intervention in skin and soft structure infections (SSSIs).

Nanobubble Contrast Enhanced Ultrasound Imaging: A Review

Contrast-enhanced ultrasound is currently used worldwide with clinical indications in cardiology and radiology, and it continues to evolve and develop through innovative technological advancements. Clinically utilized contrast agents for ultrasound consist of hydrophobic gas microbubbles stabilized with a biocompatible shell. These agents are used commonly in echocardiography, with emerging applications in cancer diagnosis and therapy. Microbubbles are a blood pool agent with diameters between 1 and 10 μm, which precludes their use in other extravascular applications. To expand the potential use of contrast-enhanced ultrasound beyond intravascular applications, sub-micron agents, often called nanobubbles or ultra-fine bubbles, have recently emerged as a promising tool. Combining the principles of ultrasound imaging with the unique properties of nanobubbles (high concentration and small size), recent work has established their imaging potential. Contrast-enhanced ultrasound imaging using these agents continues to gain traction, with new studies establishing novel imaging applications. We highlight the recent achievements in nonlinear nanobubble contrast imaging, including a discussion on nanobubble formulations and their acoustic characteristics. Ultrasound imaging with nanobubbles is still in its early stages, but it has shown great potential in preclinical research and animal studies. We highlight unexplored areas of research where the capabilities of nanobubbles may offer new advantages. As technology advances, this technique may find applications in various areas of medicine, including cancer detection and treatment, cardiovascular imaging, and drug delivery.

Ultrasound-mediated nanobubbles loaded with STAT6 siRNA inhibit TGF-β1-EMT axis in LUSC cells via overcoming the polarization of M2-TAMs

M2-like tumor-associated macrophages (M2-TAMs) are closely correlated with metastasis and poor clinical outcomes in lung squamous cell carcinoma (LUSC). Previous studies have demonstrated that STAT6 is an important signaling molecule involved in the polarization of M2-TAMs, EMT is the main way for TAMs to promote tumor progression. However, little attention has been paid to the effect of STAT6 inhibition on LUSC, and it is difficult to achieve an ideal gene silencing effect in immune cells using traditional gene transfection methods. Here, we investigated the optimal concentration of 12-myristic 13-acetate (PMA), lipopolysaccharide (LPS) for the induction of THP-1 into M1-TAMs and M2-TAMs. The expression of pSTAT6 and STAT6 was confirmed in three types of macrophages, and it was demonstrated that pSTAT6 can be used as a specific target of M2-TAMs derived from THP-1. Ultrasound-mediated nanobubble destruction (UMND) is a non-invasive and safe gene delivery technology. We also synthesized PLGA-PEI nanobubbles (NBs) to load and deliver STAT6 small interfering RNA (siRNA) into M2-TAMs via UMND. The results show that the NBs could effectively load with siRNA and had good biocompatibility. We found that UMND enhanced the transfection efficiency of siRNA, as well as the silencing effect of pSTAT6 and the inhibition of M2-TAMs. Simultaneously, when STAT6 siRNA entered M2-TAMs by UMND, proliferation, migration, invasion and EMT in LUSC cells could be inhibited via the transforming growth factor-β1 (TGF-β1) pathway. Therefore, our results confirm that UMND is an ideal siRNA delivery strategy, revealing its potential to inhibit M2-TAMs polarization and ultimately treat LUSC.

Nanobubbles and Fibroblast Growth: An In Vitro Study on Cell Migration and Proliferation

Nanobubbles are studied for their unique properties and possible applications in wound healing processes. This study investigates the effects of hydrogen (H₂), oxygen (O₂), and ozone (O₃) nanobubbles on fibroblast migration and proliferation using in vitro scratch wound healing assays. Fibroblast cells were treated with Dulbecco's Modified Eagle Medium (DMEM) combined with nanobubble solutions, and cell density was measured at 24 and 48 hours. While no significant difference was observed at 24 hours (p=0.52), ozone nanobubbles significantly reduced cell density at 48 hours (p=0.005), indicating cytotoxic effects. Hydrogen and oxygen nanobubble treatments did not show statistically significant differences from the control. These results highlight the cytotoxic effects of ozone nanobubbles on fibroblasts, which may impact their potential application in wound healing. While the study shows the cytotoxic effects of ozone nanobubbles, in vivo wound healing and antimicrobial impacts remain unexplored and warrant further study.

Polymeric Microbubble Shell Engineering: Microporosity as a Key Factor to Enhance Ultrasound Imaging and Drug Delivery Performance

Microbubbles (MB) are widely used as contrast agents for ultrasound (US) imaging and US-enhanced drug delivery. Polymeric MB are highly suitable for these applications because of their acoustic responsiveness, high drug loading capability, and ease of surface functionalization. While many studies have focused on using polymeric MB for diagnostic and therapeutic purposes, relatively little attention has thus far been paid to improving their inherent imaging and drug delivery features. This study here shows that manipulating the polymer chemistry of poly(butyl cyanoacrylate) (PBCA) MB via temporarily mixing the monomer with the monomer-mimetic butyl cyanoacetate (BCC) during the polymerization process improves the drug loading capacity of PBCA MB by more than twofold, and the in vitro and in vivo acoustic responses of PBCA MB by more than tenfold. Computer simulations and physisorption experiments show that BCC manipulates the growth of PBCA polymer chains and creates nanocavities in the MB shell, endowing PBCA MB with greater drug entrapment capability and stronger acoustic properties. Notably, because BCC can be readily and completely removed during MB purification, the resulting formulation does not include any residual reagent beyond the ones already present in current PBCA-based MB products, facilitating the potential translation of next-generation PBCA MB.

A Promising Therapeutic Strategy of Combining Acoustically Stimulated Nanobubbles and Existing Cancer Treatments

In recent years, ultrasound-stimulated microbubbles (USMBs) have gained great attention because of their wide theranostic applications. However, due to their micro-size, reaching the targeted site remains a challenge. At present, ultrasound-stimulated nanobubbles (USNBs) have attracted particular interest, and their small size allows them to extravasate easily in the blood vessels penetrating deeper into the tumor vasculature. Incorporating USNBs with existing cancer therapies such as chemotherapy, immunotherapy, and/or radiation therapy in several preclinical models has been demonstrated to have a profound effect on solid tumors. In this review, we provide an understanding of the composition and formation of nanobubbles (NBs), followed by the recent progress of the therapeutic combinatory effect of USNBs and other cancer therapies in cancer treatment.

Vascularized tumor models for the evaluation of drug delivery systems: a paradigm shift

As the conversion rate of preclinical studies for cancer treatment is low, user-friendly models that mimic the pathological microenvironment and drug intake with high throughput are scarce. Animal models are key, but an alternative to reduce their use would be valuable. Vascularized tumor-on-chip models combine great versatility with scalable throughput and are easy to use. Several strategies to integrate both tumor and vascular compartments have been developed, but few have been used to assess drug delivery. Permeability, intra/extravasation, and free drug circulation are often evaluated, but imperfectly recapitulate the processes at stake. Indeed, tumor targeting and chemoresistance bypass must be investigated to design promising cancer therapeutics. In vitro models that would help the development of drug delivery systems (DDS) are thus needed. They would allow selecting good candidates before animal studies based on rational criteria such as drug accumulation, diffusion in the tumor, and potency, as well as absence of side damage. In this review, we focus on vascularized tumor models. First, we detail their fabrication, and especially the materials, cell types, and coculture used. Then, the different strategies of vascularization are described along with their classical applications in intra/extravasation or free drug assessment. Finally, current trends in DDS for cancer are discussed with an overview of the current efforts in the domain.

Advances in the application of gas vesicles in medical imaging and disease treatment

The gas vesicle (GV) is like a hollow nanoparticle consisting of an internal gas and a protein shell, which mainly consists of hydrophobic gas vesicle protein A (GvpA) and GvpC attached to the surface. GVs, first discovered in cyanobacteria, are mainly produced by photosynthetic bacteria (PSB) and halophilic archaea. After being modified and engineered, GVs can be utilized as contrast agents, delivery carriers, and immunological boosters for disease prevention, diagnosis, and treatment with good results due to their tiny size, strong stability and non-toxicity advantages. Many diagnostic and therapeutic approaches based on GV are currently under development. In this review, we discuss the source, function, physical and chemical properties of GV, focus on the current application progress of GV, and put forward the possible application prospect and development direction of GV in the future.

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

In vivo Fate of Targeted Drug Delivery Carriers

This review aimed to systematically investigate the intracellular and subcellular fate of various types of targeting carriers. Upon entering the body via intravenous injection or other routes, a targeting carrier that can deliver therapeutic agents initiates their journey. If administered intravenously, the carrier initially faces challenges presented by the blood circulation before reaching specific tissues and interacting with cells within the tissue. At the subcellular level, the car2rier undergoes processes, such as drug release, degradation, and metabolism, through specific pathways. While studies on the fate of 13 types of carriers have been relatively conclusive, these studies are incomplete and lack a comprehensive analysis. Furthermore, there are still carriers whose fate remains unclear, underscoring the need for continuous research. This study highlights the importance of comprehending the in vivo and intracellular fate of targeting carriers and provides valuable insights into the operational mechanisms of different carriers within the body. By doing so, researchers can effectively select appropriate carriers and enhance the successful clinical translation of new formulations.

Progression in low-intensity ultrasound-induced tumor radiosensitization

BACKGROUND

Radiotherapy (RT) is a widely utilized tumor treatment approach, while a significant obstacle in this treatment modality is the radioresistance exhibited by tumor cells. To enhance the effectiveness of RT, scientists have explored radiosensitization approaches, including the use of radiosensitizers and physical stimuli. Nevertheless, several approaches have exhibited disappointing results including adverse effects and limited efficacy. A safer and more effective method of radiosensitization involves low-intensity ultrasound (LIUS), which selectively targets tumor tissue and enhances the efficacy of radiation therapy.

METHODS

This review summarized the tumor radioresistance reasons and explored LIUS potential radiosensitization mechanisms. Moreover, it covered diverse LIUS application strategies in radiosensitization, including the use of LIUS alone, ultrasound-targeted intravascular microbubble destruction, ultrasound-mediated targeted radiosensitizers delivery, and sonodynamic therapy. Lastly, the review presented the limitations and prospects of employing LIUS-RT combined therapy in clinical settings, emphasizing the need to connect research findings with practical applications.

RESULTS AND CONCLUSION

LIUS employs cost-effective equipment to foster tumor radiosensitization, curtail radiation exposure, and elevate the quality of life for patients. This efficacy is attributed to LIUS's ability to utilize thermal, cavitation, and mechanical effects to overcome tumor cell resistance to RT. Multiple experimental analyses have underscored the effectiveness of LIUS in inducing tumor radiosensitization using diverse strategies. While initial studies have shown promising results, conducting more comprehensive clinical trials is crucial to confirm its safety and effectiveness in real-world situations.

Effect of Poly(ethylene glycol) Configuration on Microbubble Pharmacokinetics

Microbubbles (MBs) hold substantial promise for medical imaging and therapy; nonetheless, knowledge gaps persist between composition, structure, and in vivo performance, especially with respect to pharmacokinetics. Of particular interest is the role of the poly(ethylene glycol) (PEG) layer, which is thought to shield the MB against opsonization and rapid clearance but is also known to cause an antibody response upon multiple injections. The goal of this study was, therefore, to elucidate the role of the PEG layer in circulation persistence of MBs in the naïve animal (prior to an adaptive immune response). Here, we directly observe the number and size of individual MBs obtained from blood samples, unifying size and concentration into the microbubble volume dose (MVD) parameter. This approach enables direct evaluation of the pharmacokinetics of intact MBs, comprising both the lipid shell and gaseous core, rather than separately assessing the lipid or gas components. We examined the in vivo circulation persistence of 3 μm diameter phospholipid-coated MBs with three different mPEG2000 content: 2 mol % (mushroom), 5 mol % (intermediate), and 10 mol % (brush). MB size and concentration in the blood were evaluated by a hemocytometer analysis over 30 min following intravenous injections of 20 and 40 μL/kg MVD in Sprague-Dawley rats. Interestingly, pharmacokinetic analysis demonstrated that increasing PEG concentration on the MB surface resulted in faster clearance. This was evidenced by a 1.6-fold reduction in half-life and area under the curve (AUC) (p < 0.05) in the central compartment. Conversely, the AUC in the peripheral compartment increased with PEG density, suggesting enhanced MB trapping by the mononuclear phagocyte system. This was supported by an in vitro assay, which showed a significant rise in complement C3a activation with a higher PEG content. In conclusion, a minimal PEG concentration on the MB shell (mushroom configuration) was found to prolong circulation and mitigate immunogenicity.

Revolutionizing lymph node metastasis imaging: the role of drug delivery systems and future perspectives

The deployment of imaging examinations has evolved into a robust approach for the diagnosis of lymph node metastasis (LNM). The advancement of technology, coupled with the introduction of innovative imaging drugs, has led to the incorporation of an increasingly diverse array of imaging techniques into clinical practice. Nonetheless, conventional methods of administering imaging agents persist in presenting certain drawbacks and side effects. The employment of controlled drug delivery systems (DDSs) as a conduit for transporting imaging agents offers a promising solution to ameliorate these limitations intrinsic to metastatic lymph node (LN) imaging, thereby augmenting diagnostic precision. Within the scope of this review, we elucidate the historical context of LN imaging and encapsulate the frequently employed DDSs in conjunction with a variety of imaging techniques, specifically for metastatic LN imaging. Moreover, we engage in a discourse on the conceptualization and practical application of fusing diagnosis and treatment by employing DDSs. Finally, we venture into prospective applications of DDSs in the realm of LNM imaging and share our perspective on the potential trajectory of DDS development.

Use of oxygen-loaded nanobubbles to improve tissue oxygenation: Bone-relevant mechanisms of action and effects on osteoclast differentiation

Gas-loaded nanobubbles have potential as a method of oxygen delivery to increase tumour oxygenation and therapeutically alleviate tumour hypoxia. However, the mechanism(s) whereby oxygen-loaded nanobubbles increase tumour oxygenation are unknown; with their calculated oxygen-carrying capacity being insufficient to explain this effect. Intra-tumoural hypoxia is a prime therapeutic target, at least partly due to hypoxia-dependent stimulation of the formation and function of bone-resorbing osteoclasts which establish metastatic cells in bone. This study aims to investigate potential mechanism(s) of oxygen delivery and in particular the possible use of oxygen-loaded nanobubbles in preventing bone metastasis via effects on osteoclasts. Lecithin-based nanobubbles preferentially interacted with phagocytic cells (monocytes, osteoclasts) via a combination of lipid transfer, clathrin-dependent endocytosis and phagocytosis. This interaction caused general suppression of osteoclast differentiation via inhibition of cell fusion. Additionally, repeat exposure to oxygen-loaded nanobubbles inhibited osteoclast formation to a greater extent than nitrogen-loaded nanobubbles. This gas-dependent effect was driven by differential effects on the fusion of mononuclear precursor cells to form pre-osteoclasts, partly due to elevated potentiation of RANKL-induced ROS by nitrogen-loaded nanobubbles. Our findings suggest that oxygen-loaded nanobubbles could represent a promising therapeutic strategy for cancer therapy; reducing osteoclast formation and therefore bone metastasis via preferential interaction with monocytes/macrophages within the tumour and bone microenvironment, in addition to known effects of directly improving tumour oxygenation.

A combination of PD-L1-targeted IL-15 mRNA nanotherapy and ultrasound-targeted microbubble destruction for tumor immunotherapy

PD-1/PD-L1-based immune checkpoint blockade therapy has shown limited benefits in tumor patients, partially attributed to the inadequate infiltration of immune effector cells within tumors. Here, we established a nanoplatform named DPPA/IL-15 NPs to target PD-L1 for the tumor delivery of IL-15 messenger RNA (mRNA). DPPA/IL-15 NPs were endowed with ultrasound responsiveness and contrast-enhanced ultrasound (CEUS) imaging performance. They effectively protected IL-15 mRNA from degradation and specifically transfected it into tumor cells through the utilization of ultrasound-targeted microbubble destruction (UTMD). This resulted in the activation of IL-15-related immune effector cells while blocking the PD-1/PD-L1 pathway. In addition, UTMD could generate reactive oxygen species (ROS) that induce endoplasmic reticulum (ER) stress-driven immunogenic cell death (ICD), initiating anti-tumor immunity. In vitro and in vivo studies revealed that this combination therapy could induce a robust systemic immune response and enhance anti-tumor efficacy. Thus, this combination therapy has the potential for clinical translation through enhanced immunotherapy and provides real-time ultrasound imaging guidance.

Quantitative Parameters of Contrast-Enhanced Ultrasound Predicting the Response to Combined Immune Checkpoint Inhibitor and Anti-angiogenesis Therapies for Unresectable Hepatocellular Carcinoma

OBJECTIVE

The aim of the work described here was to explore the value of contrast-enhanced ultrasound (CEUS) quantitative parameters in predicting the response of combined immune checkpoint inhibitor (ICI) and anti-angiogenesis therapies for unresectable hepatocellular carcinoma (HCC).

METHODS

Sixty-six HCC patients who underwent combined ICI and anti-angiogenesis therapies were prospectively enrolled. A CEUS examination was performed at baseline, and tumor perfusion parameters were obtained with perfusion quantification software. The differences in CEUS quantitative parameters between the responder and non-responder groups were compared, and the correlations between CEUS parameters and progression-free survival (PFS) was evaluated.

RESULTS

The objective response rate (ORR) was 21.2%. The values of rising time (RT) ratio, time to peak ratio, fall time ratio, peak enhancement ratio, wash-in rate ratio, wash-in perfusion index ratio and wash-out rate ratio differed significantly differed between the responder and non-responder groups (all p values < 0.05). Multivariable logistic regression analysis revealed that the RT ratio was the only independent factor associated with the ORR (odds ratio = 0.007, 95% confidence interval: 0.000-0.307, p = 0.010). The median RT ratios of the responder and non-responder groups were 36.9 and 58.9, respectively (p = 0.006). The appropriate cutoff point of the RT ratio was 80.1, determined with the X-tile program. Survival analysis indicated high PFS for the patients with a lower RT ratio (high RT ratio vs. low RT ratio = 4.4 mo vs. not reached, p = 0.001).

CONCLUSION

CEUS quantitative parameters may predict the efficacy of ICI and anti-angiogenesis combined therapies for HCC.

Nanotheranostics in cancer lymph node metastasis: The long road ahead

Lymph node metastasis (LNM) significantly impacts the prognosis of cancer patients. Despite significant advancements in diagnostic techniques and treatment modalities, clinical challenges continue to persist in the realm of LNM. These include difficulties in early diagnosis, limited treatment efficacy, and potential side effects and injuries associated with treatment. Nanotheranostics, a field within nanotechnology, seamlessly integrates diagnostic and therapeutic functionalities. Its primary goal is to provide precise and effective disease diagnosis and treatment simultaneously. The development of nanotheranostics for LNM offers a promising solution for the stratified management of patients with LNM and promotes the advancement of personalized medicine. This review introduces the mechanisms of LNM and challenges in its diagnosis and treatment. Furthermore, it demonstrates the advantages and development potential of nanotheranostics, focuses on the challenges nanotheranostics face in its application, and provides an outlook on future trends. We consider nanotheranostics a promising strategy to improve clinical effectiveness and efficiency as well as the prognosis of cancer patients with LNM.

rtPA-loaded fucoidan polymer microbubbles for the targeted treatment of stroke

Systemic injection of thrombolytic drugs is the gold standard treatment for non-invasive blood clot resolution. The most serious risks associated with the intravenous injection of tissue plasminogen activator-like proteins are the bleeding complication and the dose related neurotoxicity. Indeed, the drug has to be injected in high concentrations due to its short half-life, the presence of its natural blood inhibitor (PAI-1) and the fast hepatic clearance (0.9 mg/kg in humans, 10 mg/kg in mouse models). Overall, there is a serious need for a dose-reduced targeted treatment to overcome these issues. We present in this article a new acoustic cavitation-based method for polymer MBs synthesis, three times faster than current hydrodynamic-cavitation method. The generated MBs are ultrasound responsive, stable and biocompatible. Their functionalization enabled the efficient and targeted treatment of stroke, without side effects. The stabilizing shell of the MBs is composed of Poly-Isobutyl Cyanoacrylate (PIBCA), copolymerized with fucoidan. Widely studied for its targeting properties, fucoidan exhibit a nanomolar affinity for activated endothelium and activated platelets (P-selectins). Secondly, the thrombolytic agent (rtPA) was loaded onto microbubbles (MBs) with a simple adsorption protocol. Hence, the present study validated the in vivo efficiency of rtPA-loaded Fuco MBs to be over 50 % more efficient than regular free rtPA injection for stroke resolution. In addition, the relative injected rtPA grafted onto targeting MBs was 1/10th of the standard effective dose (1 mg/kg in mouse). As a result, no hemorrhagic event, BBB leakage nor unexpected tissue distribution were observed.

The Green Synthesis of Reduced Graphene Oxide Using Ellagic Acid: Improving the Contrast-Enhancing Effect of Microbubbles in Ultrasound

There is an urgent need to realize precise clinical ultrasound with ultrasound contrast agents that provide high echo intensity and mechanical index tolerance. Graphene derivatives possess exceptional characteristics, exhibiting great potential in fabricating ideal ultrasound contrast agents. Herein, we reported a facile and green approach to synthesizing reduced graphene oxide with ellagic acid (rGO-EA). To investigate the application of a graphene derivative in ultrasound contrast agents, rGO-EA was dispersed in saline solution and mixed with SonoVue (SV) to fabricate SV@rGO-EA microbubbles. To determine the properties of the product, analyses were performed, including ultraviolet-visible spectroscopy (UV-vis), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectrum (XPS), X-ray diffraction analysis (XRD) and zeta potential analysis. Additionally, cell viability measurements and a hemolysis assay were conducted for a biosafety evaluation. SV@rGO-EA microbubbles were scanned at various mechanical index values to obtain the B-mode and contrast-enhanced ultrasound (CEUS) mode images in vitro. SV@rGO-EA microbubbles were administered to SD rats, and their livers and kidneys were imaged in CEUS and B-mode. The absorption of rGO-EA resulted in an enhanced echo intensity and mechanical index tolerance of SV@rGO-EA, surpassing the performance of SV microbubbles both in vitro and in vivo. This work exhibited the application potential of graphene derivatives in the field of ultrasound precision medicine.