The phagocytosis of gas-filled microbubbles by human and murine antigen-presenting cells

Self-Immolated Nanoadjuvant for In Situ Vaccination Immunotherapy of Colorectal Cancer

Vaccination immunotherapy has revolutionized cancer treatment modalities. Although the immunomodulatory adjuvant generally employs for potentiating vaccine response, systemic administration may drive immune-related side effects, even immune tolerance. Therefore, tunable immunoadjuvants are highly desirable to simultaneously stimulate the immune response and mitigate systemic toxicity. Self-immolated nanoadjuvants are herein reported to potentiate vaccination immunotherapy of cancer. The nanoadjuvants are engineered by co-assembling an intracellular acidity-ionizable polymeric agonist of toll-like receptor 7/8 resiquimod (R848) and polymeric photosensitizer pyropheophorbide a (PPa). The resultant nanoadjuvants specifically accumulate at the tumor site via passive targeting and are dissociated in the acidic endosome versicles to activate PPa via protonation of the polymer backbone. Upon 671 nm laser irradiation, PPa performed photodynamic therapy to induce immunogenic cell death of tumor cells and subsequently releases R848 in a customized manner, which synergistically activates dendritic cells (DCs), promotes antigen cross-presentation, and eventually recruits cytotoxic T lymphocytes for tumor regression. Furthermore, the synergistic in situ vaccination immunotherapy with immune checkpoint blockade induce sustained immunological memory to suppress tumor recurrence in the rechallenged colorectal tumor model.

Bubble-Based Drug Delivery Systems: Next-Generation Diagnosis to Therapy

Current radiologic and medication administration is systematic and has widespread side effects; however, the administration of microbubbles and nanobubbles (MNBs) has the possibility to provide therapeutic and diagnostic information without the same ramifications. Microbubbles (MBs), for instance, have been used for ultrasound (US) imaging due to their ability to remain in vessels when exposed to ultrasonic waves. On the other hand, nanobubbles (NBs) can be used for further therapeutic benefits, including chronic treatments for osteoporosis and cancer, gene delivery, and treatment for acute conditions, such as brain infections and urinary tract infections (UTIs). Clinical trials are also being conducted for different administrations and utilizations of MNBs. Overall, there are large horizons for the benefits of MNBs in radiology, general medicine, surgery, and many more medical applications. As such, this review aims to evaluate the most recent publications from 2016 to 2022 to report the current uses and innovations for MNBs.

Evaluation of Liposome-Loaded Microbubbles as a Theranostic Tool in a Murine Collagen-Induced Arthritis Model

Rheumatoid arthritis (RA) is an autoimmune disease characterized by severe inflammation of the synovial tissue. Here, we assess the feasibility of liposome-loaded microbubbles as theranostic agents in a murine arthritis model. First, contrast-enhanced ultrasound (CEUS) was used to quantify neovascularization in this model since CEUS is well-established for RA diagnosis in humans. Next, the potential of liposome-loaded microbubbles and ultrasound (US) to selectively enhance liposome delivery to the synovium was evaluated with in vivo fluorescence imaging. This procedure is made very challenging by the presence of hard joints and by the limited lifetime of the microbubbles. The inflamed knee joints were exposed to therapeutic US after intravenous injection of liposome-loaded microbubbles. Loaded microbubbles were found to be quickly captured by the liver. This resulted in fast clearance of attached liposomes while free and long-circulating liposomes were able to accumulate over time in the inflamed joints. Our observations show that murine arthritis models are not well-suited for evaluating the potential of microbubble-mediated drug delivery in joints given: (i) restricted microbubble passage in murine synovial vasculature and (ii) limited control over the exact ultrasound conditions in situ given the much shorter length scale of the murine joints as compared to the therapeutic wavelength.

In vitro and in vivo osteogenesis up-regulated by two-dimensional nanosheets through a macrophage-mediated pathway

Two-dimensional (2D) nanomaterials are attracting more and more interest in regenerative medicine due to their unique properties; however 2D biomimetic calcium mineral has not yet been developed and demonstrated application for bone tissue engineering. Here we described a novel calcium phosphate material with a 2D nanostructure that was synthesized using collagen and sodium alginate as the template. In vitro performance of the nanocrystalline material was evaluated, and we found that 2D CaP nanoparticles (NPs) enhanced the in vitro osteogenic differentiation of rat mesenchymal stem cells (rMSCs) through a macrophage-mediated signal pathway, when co-cultured with RAW 264.7 cells, rather than direct NP/stem cell interaction. A 2D topology structured surface was constructed by encapsulating the CaP nanomaterials in a gelatin hydrogel, which was demonstrated to be able to mediate in vivo ossification through a macrophage polarization related pathway in a femur defect rat model, and allowed the optimal therapeutic outcome compared to normal CaP counterparts. Our current work may have enlightened a new mechanism regarding NP-induced stem cell differentiation through immunoregulation, and the 2D CaP encapsulated hydrogel scaffold may serve as a potential alternative to autograft bone for orthopedic applications.

Opening doors with ultrasound and microbubbles: Beating biological barriers to promote drug delivery

Apart from its clinical use in imaging, ultrasound has been thoroughly investigated as a tool to enhance drug delivery in a wide variety of applications. Therapeutic ultrasound, as such or combined with cavitating nuclei or microbubbles, has been explored to cross or permeabilize different biological barriers. This ability to access otherwise impermeable tissues in the body makes the combination of ultrasound and therapeutics very appealing to enhance drug delivery in situ. This review gives an overview of the most important biological barriers that can be tackled using ultrasound and aims to provide insight on how ultrasound has shown to improve accessibility as well as the biggest hurdles. In addition, we discuss the clinical applicability of therapeutic ultrasound with respect to the main challenges that must be addressed to enable the further progression of therapeutic ultrasound towards an effective, safe and easy-to-use treatment tailored for drug delivery in patients.

Nanoparticles for mucosal vaccine delivery

Mucosal surfaces represent important routes of entry into the human body for the majority of pathogens, and they constitute unique sites for targeted vaccine delivery. Nanoparticle-based drug delivery systems are emerging technologies for delivering and improving the efficacy of mucosal vaccines. Recent studies have provided new insights into formulation and delivery aspects of importance for the design of safe and efficacious mucosal subunit vaccines based on nanoparticles. These include novel nanomaterials, their physicochemical properties and formulation approaches, nanoparticle interaction with immune cells in the mucosa, and mucosal immunization and delivery strategies. Here, we present recent progress in the application of nanoparticle-based approaches for mucosal vaccine delivery and discuss future research challenges and opportunities in the field.

Persistent Enhancement on Contrast-Enhanced Ultrasound Studies of Severe Crohn's Disease: Stuck Bubbles?

A small population of patients with severe Crohn's disease (CD) exhibit atypical lack of intensity decline on intestinal contrast-enhanced ultrasound. From a retrospective CD cohort examined with contrast-enhanced ultrasound, 104 patients were identified. Twenty study patients with severe active disease exhibited high peak enhancement (>23 dB) and minimal decline. From the same cohort, 84 control patients also exhibited high peak enhancement >23dB, but with typical intensity decline. Patient outcomes were assessed. Time-intensity curve analysis revealed a significantly higher (p < 0.0001) area under the curve (44.7 ± 1.5 dB·s), washout time and intensities at 60s and 120s in the study population compared with controls (40.0 ± 1.1 dB·s). Study patients had a worse overall outcome with surgery in 30% versus 10% (p = 0.027) during follow-up. Heightened enhancement with lack of decline on contrast-enhanced ultrasound suggests microbubbles are stuck within the inflamed bowel wall for an extended period. This observation occurs in patients with severe disease and a bad outcome.

Gas‑filled ultrasound microbubbles enhance the immunoactivity of the HSP70‑MAGEA1 fusion protein against MAGEA1‑expressing tumours

Advanced malignant melanoma is characterized by rapid development, poor prognosis and insensitivity to chemoradiotherapy. Immunotherapy has become one of the primary clinical treatments for malignant melanomas. In recent decades, identifying specific tumour antigens and the enhanced immunoactivity of tumour vaccines has become critical for engineering successful tumour vaccines. As a widely used vaccine carrier, heat shock protein 70 (HSP70) clearly increases the immunogenicity of tumour antigens, such as melanoma-associated antigen A1 (MAGEA1). Based on previous studies, gas-filled ultrasound microbubbles (MBs) were engineered to carry an HSP70-MAGEA1 fusion protein (FP). Following subcutaneous injection around the lymphatic nodes the FP was directly released into the lymph nodes under ultrasonic imaging. The results indicated that the microbubbles enhanced the immunoactivity of FPs more effectively than HSP70-MAGEA1 fusion alone. Additionally, HSP70-MAGEA1 delivered via microbubbles clearly inhibited and delayed the growth of MAGEA1-expressing B16 melanomas in mice and improved the survival times of these animals compared with the fusion protein alone. The results of the present study demonstrated that controlled MBs enhance the immunoactivity of FPs and also highlights novel, potential vaccine carriers and a new strategy for engineering controllable tumour vaccine designs.

Lipid-Based Particles: Versatile Delivery Systems for Mucosal Vaccination against Infection

Vaccination is the process of administering immunogenic formulations in order to induce or harness antigen (Ag)-specific antibody and T cell responses in order to protect against infections. Important successes have been obtained in protecting individuals against many deleterious pathological situations after parenteral vaccination. However, one of the major limitations of the current vaccination strategies is the administration route that may not be optimal for the induction of immunity at the site of pathogen entry, i.e., mucosal surfaces. It is now well documented that immune responses along the genital, respiratory, or gastrointestinal tracts have to be elicited locally to ensure efficient trafficking of effector and memory B and T cells to mucosal tissues. Moreover, needle-free mucosal delivery of vaccines is advantageous in terms of safety, compliance, and ease of administration. However, the quest for mucosal vaccines is challenging due to (1) the fact that Ag sampling has to be performed across the epithelium through a relatively limited number of portals of entry; (2) the deleterious acidic and proteolytic environment of the mucosae that affect the stability, integrity, and retention time of the applied Ags; and (3) the tolerogenic environment of mucosae, which requires the addition of adjuvants to elicit efficient effector immune responses. Until now, only few mucosally applicable vaccine formulations have been developed and successfully tested. In animal models and clinical trials, the use of lipidic structures such as liposomes, virosomes, immune stimulating complexes, gas-filled microbubbles and emulsions has proven efficient for the mucosal delivery of associated Ags and the induction of local and systemic immune reponses. Such particles are suitable for mucosal delivery because they protect the associated payload from degradation and deliver concentrated amounts of Ags via specialized sampling cells (microfold cells) within the mucosal epithelium to underlying antigen-presenting cells. The review aims at summarizing recent development in the field of mucosal vaccination using lipid-based particles. The modularity ensured by tailoring the lipidic design and content of particles, and their known safety as already established in humans, make the continuing appraisal of these vaccine candidates a promising development in the field of targeted mucosal vaccination.

Ultrasonic Characteristics and Cellular Properties of Anabaena Gas Vesicles

Ultrasound imaging is a common modality in clinical examination and biomedical research, but has not played a significant role in molecular imaging for lack of an appropriate contrast agent. Recently, biogenic gas vesicles (GVs), naturally formed by cyanobacteria and haloarchaea, have exhibited great potential as an ultrasound molecular imaging probe with a much smaller size (∼100 nm) and improved imaging contrast. However, the basic acoustic and biological properties of GVs remain unclear, which hinders future application. Here, we studied the fundamental acoustic properties of a rod-shaped gas vesicle from Anabaena, a kind of cyanobacterium, including attenuation, oscillation resonance, and scattering, as well as biological behaviors (cellular internalization and cytotoxicity). We found that GVs have two resonance peaks (85 and 120 MHz). We also observed a significant non-linear effect and its pressure dependence as well. Ultrasound B-mode imaging reveals sufficient echogenicity of GVs for ultrasound imaging enhancement at high frequencies. Biological characterization also reveals endocytosis and non-toxicity.

Molecular Ultrasound Imaging of Junctional Adhesion Molecule A Depicts Acute Alterations in Blood Flow and Early Endothelial Dysregulation

OBJECTIVE

The junctional adhesion molecule A (JAM-A) is physiologically located in interendothelial tight junctions and focally redistributes to the luminal surface of blood vessels under abnormal shear and flow conditions accompanying atherosclerotic lesion development. Therefore, JAM-A was evaluated as a target for molecularly targeted ultrasound imaging of transient endothelial dysfunction under acute blood flow variations.

APPROACH AND RESULTS

Flow-dependent endothelial dysfunction was induced in apolipoprotein E-deficient mice (n=43) by carotid partial ligation. JAM-A expression was investigated by molecular ultrasound using antibody-targeted poly(n-butyl cyanoacrylate) microbubbles and validated with immunofluorescence. Flow disturbance and arterial remodeling were assessed using functional ultrasound. Partial ligation led to an immediate drop in perfusion at the ligated side and a direct compensatory increase at the contralateral side. This was accompanied by a strongly increased JAM-A expression and JAM-A-targeted microbubbles binding at the partially ligated side and by a moderate and temporary increase in the contralateral artery (≈14× [P<0.001] and ≈5× [P<0.001] higher than control, respectively), both peaking after 2 weeks. Subsequently, although JAM-A expression and JAM-A-targeted microbubbles binding persisted at a higher level at the partially ligated side, it completely normalized within 4 weeks at the contralateral side.

CONCLUSIONS

Temporary blood flow variations induce endothelial rearrangement of JAM-A, which can be visualized using JAM-A-targeted microbubbles. Thus, JAM-A may be considered as a marker of acute endothelial activation and dysfunction. Its imaging may facilitate the early detection of cardiovascular risk areas, and it enables the therapeutic prevention of their progression toward an irreversible pathological state.

Ultrasound-mediated destruction of oxygen and paclitaxel loaded dual-targeting microbubbles for intraperitoneal treatment of ovarian cancer xenografts

Folate receptor (FR) is overexpressed in many epithelial cancers and tumor-associated macrophages (TAMs), which enable it to function as an appropriate target for cancer treatment. We have successfully synthesized multifunctional folate-targeted and oxygen/paclitaxel loaded microbubbles (TOPLMBs) for ultrasound (US) mediated delivery for combination therapy in an intraperitoneal ovarian cancer xenograft model. The TOPLMBs target both ovarian cancer cells and TAMs and provide a promising drug delivery strategy for the combination treatment of ovarian cancer and tumor microenvironment. Microscopic imaging and flow cytometric analysis showed that TOPLMBs significantly penetrated into ovarian cancer cells and tumor-associated macrophages (TAMs) within tumor ascites fluid and the tumor nodules. Immunohistochemical analyses of dissected tumor tissue confirmed the increased tumor apoptosis, the reduced expression of vascular endothelial growth factor (VEGF) and microvascular density (MVD), and the reduced expression of CD68 after treatment (P < 0.05). Our experiment results suggest that intraperitoneal injection of dual-targeting TOPLMBs followed by US mediation provide a promising drug delivery strategy for combination treatment of ovarian cancer and tumor microenvironment with the therapeutic outcome superior to that of conventional therapeutic options.

Design of a Novel Composite H2 S-Releasing Hydrogel for Cardiac Tissue Repair

The design of 3D scaffolds is a crucial step in the field of regenerative medicine. Scaffolds should be degradable and bioresorbable as well as display good porosity, interconnecting pores, and topographic features; these properties favour tissue integration and vascularization. These requirements could be fulfilled by hybrid hydrogels using a combination of natural and synthetic components. Here, the mechanical and biological properties of a polyethylene glycol-fibrinogen hydrogel (PFHy) are improved in order to favour the proliferation and differentiation of human Sca-1(pos) cardiac progenitor cells (hCPCs). PFHys are modified by embedding air- or perfluorohexane-filled bovine serum albumin microbubbles (MBs) and characterized. Changes in cell morphology are observed in MBs-PFHys, suggesting that MBs could enhance the formation of bundles of cells and influence the direction of the spindle growth. The properties of MBs as carriers of active macromolecules are also exploited. For the first time, enzyme-coated MBs have been used as systems for the production of hydrogen sulfide (H2 S)-releasing scaffolds. Novel H2 S-releasing PFHys are produced, which are able to improve the growth of hCPCs. This novel 3D cell-scaffold system will allow the assessment of the effects of H2 S on the cardiac muscle regeneration with its potential applications in tissue repair.

Co-administration of Microbubbles and Drugs in Ultrasound-Assisted Drug Delivery: Comparison with Drug-Carrying Particles

There are two alternative approaches to ultrasound-assisted drug delivery. First, the drug can be entrapped into or attached onto the ultrasound-responsive particles and administered in the vasculature, to achieve ultrasound-triggered drug release from the particles and localized tissue deposition in response to ultrasound treatment of the target zone. Second, the drug can be co-administered with the microbubbles or other sonosensitive particles. In this case, the action of ultrasound on the particles (which act as cavitation nuclei) results in the transient improvement of permeability of the physiological barriers, so that the circulating drug can exit the bloodstream and get into the target tissues and cells. We discuss and compare both of these approaches, their characteristic advantages and disadvantages for the specific drug delivery scenarios. Clearly, the system based on the off-label use of the existing approved microbubbles and drugs (or drug carriers) will have a chance of getting to clinical trials faster and with lesser resources spent. However, if a superior curative potential of a sonosensitive drug carrier is proven, and formulation stability problems are addressed properly, this approach may find its way to practical use, especially for nucleic acid delivery scenarios.

Ultrasound-mediated destruction of LHRHa-targeted and paclitaxel-loaded lipid microbubbles for the treatment of intraperitoneal ovarian cancer xenografts

Ultrasound-targeted microbubble destruction (UTMD) is a promising technique to facilitate the delivery of chemotherapy in cancer treatment. However, the process typically uses nonspecific microbubbles, leading to low tumor-to-normal tissue uptake ratio and adverse side effects. In this study, we synthesized the LHRH receptor-targeted and paclitaxel (PTX)-loaded lipid microbubbles (TPLMBs) for tumor-specific binding and enhanced therapeutic effect at the tumor site. An ovarian cancer xenograft model was established by injecting A2780/DDP cells intraperitoneally in BALB/c nude mice. Microscopic imaging of tumor sections after intraperitoneal injection of TPLMBs showed effective binding of the microbubbles with cancer cells. Ultrasound mediated destruction of the intraperitoneally injected TPLMBs yielded a superior therapeutic outcome in comparison with other treatment options. Immunohistochemical analyses of the dissected tumor tissue further confirmed the increased tumor apoptosis and reduced angiogenesis. Our experiment suggests that ultrasound-mediated intraperitoneal administration of the targeted drug-loaded microbubbles may be a useful method for the treatment of ovarian cancer.