Development and application of ultrasound contrast agents in biomedicine

Integrated organosilica nanomedicine enables sonoimaging, sonochemistry and antitumor sonodynamic therapy

Sonography with its non-invasive and deep tissue-penetrating characteristics, not only contributes to promising developments in clinical disease diagnosis but also obtains acknowledgments as a prospective therapeutic approach in the field of tumor treatment. However, it remains a challenge for sonography simultaneously to achieve efficient imaging and therapeutic functionality. Here, we present an innovative integrated diagnosis and treatment paradigm by developing the nanomedicine of percarbamide-bromide-mesoporous organosilica spheres (MOS) with RGD peptide modification (PBMR) by loading percarbamide and bromide in MOS which were prepared by a one-step O/W microemulsion method. The PBMR nanomedicine effectively modifies the tumor acoustic environment to improve sonoimaging efficacy and induces sonochemical reactions to enhance the production of reactive oxygen species (ROS) for tumor treatment efficiency under sonography. The combination of PBMR nanomedicine and SDT achieved multiple ROS generation through the controlled sonochemical reactions and significantly boosted the potency of sonodynamic therapy and induced significant tumor regression with non-invasive tissue penetrability and minimizing damage to healthy tissues. Simultaneously, the generation of oxygen gas in the sonochemical process augments ultrasound reflection, resulting in a 4.9-fold increase in imaging grayscale. Our research establishes an effective platform for the synergistic integration of sonoimaging and sonodynamic antitumor therapy, offering a novel approach for precise antitumor treatment in the potential clinical applications.

Ultrasound contrast agent assisted ultrasonography guidance percutaneous nephrostomy for non-hydronephrotic kidney

BACKGROUND

Given the limited success rate and considerable challenges associated with conventional ultrasonography (US) guidance for percutaneous nephrostomy (PCN) in non-hydronephrotic kidneys, this study proposed a solution with ultrasound contrast agent to enhance the success rate and mitigate the difficulties.

MATERIALS AND METHODS

From January 2017 to August 2023, a total of thirteen patients diagnosed with non-hydronephrotic kidney were included in the study. Following routine ultrasonography examination, no significant dilatation of the renal collecting system was observed. US-guided percutaneous nephrostomy PCN was performed with the assistance of ultrasound contrast agent (UCA). The patients were subsequently monitored to assess the improvement of symptoms and postoperative recovery.

RESULTS

The success rate was found to be 100% for all patients (13/13) and kidneys (20/20). The average volume of UCA solution used was 19 ± 6.7 mL (range, 11-35 mL), while the mean duration of the operation was 18.92 ± 8.96 min (range, 7-36 min). A majority of the patients (12/13) underwent a single puncture procedure. Throughout the follow-up period, no serious complications were observed, and surgery resulted in significant alleviation of symptoms in all patients.

CONCLUSION

The use of UCA-assisted US guidance PCN has been shown to be effective in achieving urinary diversion and alleviating associated clinical symptoms in non-hydronephrotic kidneys. In comparison to traditional methods, this approach demonstrates a high success rate and safety profile, while also offering a simplified operative procedure. Consequently, it presents a novel method and concept for managing non-hydronephrotic kidneys afflicted by urine leakage.

Diagnostic Value of Contrast-Enhanced Ultrasonography for Catheter-Related Right Brachiocephalic Vein and Superior Vena Cava Lesions in Patients Undergoing Hemodialysis-A Pilot Study

OBJECTIVES

To evaluate the diagnostic efficacy of contrast-enhanced ultrasonography (CEUS) for detecting catheter-related right brachiocephalic vein (RBV) and superior vena cava (SVC) obstructions in patients undergoing hemodialysis (HD).

METHODS

From June 1, 2021 to December 31, 2022, we enrolled 80 patients undergoing HD who had used or were using a central venous catheter as vascular access. We evaluated the diagnostic efficacy of conventional ultrasonography and CEUS for identifying RBV and SVC obstructions and compared them with that of digital subtraction angiography (DSA). In the stratified analysis, the SVC was divided into the upper and lower segments. In total, we analyzed 240 central venous segments, including the RBV.

RESULTS

Among the RBV and SVC visualized by DSA, conventional ultrasonography and CEUS could visualize 67.92 and 100% of the vein segments, respectively; however, the lengths and diameters of the RBV and SVC were smaller than those recorded with DSA (P < .001). The diagnostic efficacy of CEUS for detecting catheter-related central venous obstruction was better than that of conventional ultrasonography, with a higher sensitivity (83.95 vs 41.98%), specificity (89.94 vs 53.46%), accuracy (87.92 vs 49.58%), and F1 score (82.42 vs 49.64%). CEUS showed good agreement (κ = 0.732) with DSA. In the stratified analyses, CEUS also showed higher sensitivity (83.93, 83.33, and 84.62%, respectively) and better agreement with DSA (κ = 0.635, 0.655, and 0.673, respectively) than conventional ultrasonography for detecting the RBV and the upper and lower segments of the SVC.

CONCLUSIONS

CEUS had high sensitivity and specificity in diagnosing catheter-related RBV and SVC obstructions.

Ultrasound Sonosensitizers for Tumor Sonodynamic Therapy and Imaging: A New Direction with Clinical Translation

With the rapid development of sonodynamic therapy (SDT), sonosensitizers have evolved from traditional treatments to comprehensive diagnostics and therapies. Sonosensitizers play a crucial role in the integration of ultrasound imaging (USI), X-ray computed tomography (CT), and magnetic resonance imaging (MRI) diagnostics while also playing a therapeutic role. This review was based on recent articles on multifunctional sonosensitizers that were used in SDT for the treatment of cancer and have the potential for clinical USI, CT, and MRI applications. Next, some of the shortcomings of the clinical examination and the results of sonosensitizers in animal imaging were described. Finally, this paper attempted to inform the future development of sonosensitizers in the field of integrative diagnostics and therapeutics and to point out current problems and prospects for their application.

The Evolution and Recent Trends in Acoustic Targeting of Encapsulated Drugs to Solid Tumors: Strategies beyond Sonoporation

Despite recent advancements in ultrasound-mediated drug delivery and the remarkable success observed in pre-clinical studies, no delivery platform utilizing ultrasound contrast agents has yet received FDA approval. The sonoporation effect was a game-changing discovery with a promising future in clinical settings. Various clinical trials are underway to assess sonoporation's efficacy in treating solid tumors; however, there are disagreements on its applicability to the broader population due to long-term safety issues. In this review, we first discuss how acoustic targeting of drugs gained importance in cancer pharmaceutics. Then, we discuss ultrasound-targeting strategies that have been less explored yet hold a promising future. We aim to shed light on recent innovations in ultrasound-based drug delivery including newer designs of ultrasound-sensitive particles specifically tailored for pharmaceutical usage.

Recent applications of phase-change materials in tumor therapy and theranostics

Phase-change materials (PCMs) are a type of special material which can store and release a large amount of thermal energy without any significant temperature change. They are emerging in recent years as a promising functional material in tumor therapy and theranostics due to their accurate responses to the temperature variations, biocompatibility and low toxicity. In this review, we will introduce the main types of PCMs and their desirable physiochemical properties for biomedical applications, and highlight the recent progress of PCM's applications in the modulated release of antitumor drugs, with special attentions paid to various ways to initiate temperature-dependent phase change, the concomitant thermal therapy and its combination with or activation of other therapies, particularly unconventional therapies. We will also summarize PCM's recent applications in tumor theranostics, where both drugs and imaging probes are delivered by PCMs for controlled drug release and imaging-guided therapy. Finally, the future perspectives and potential limitations of harnessing PCMs in tumor therapy will be discussed.

Ultrasound-targeted microbubble destruction remodels tumour microenvironment to improve immunotherapeutic effect

Cancer immunotherapy (CIT) has gained increasing attention and made promising progress in recent years, especially immune checkpoint inhibitors such as antibodies blocking programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4). However, its therapeutic efficacy is only 10-30% in solid tumours and treatment sensitivity needs to be improved. The complex tissue environment in which cancers originate is known as the tumour microenvironment (TME) and the complicated and dynamic TME is correlated with the efficacy of immunotherapy. Ultrasound-targeted microbubble destruction (UTMD) is an emerging technology that integrates diagnosis and therapy, which has garnered much traction due to non-invasive, targeted drug delivery and gene transfection characteristics. UTMD has also been studied to remodel TME and improve the efficacy of CIT. In this review, we analyse the effects of UTMD on various components of TME, including CD8⁺ T cells, tumour-infiltrating myeloid cells, regulatory T cells, natural killer cells and tumour vasculature. Moreover, UTMD enhances the permeability of the blood-brain barrier to facilitate drug delivery, thus improving CIT efficacy in vivo animal experiments. Based on this, we highlight the potential of immunotherapy against various cancer species and the clinical application prospects of UTMD.

Resonance behaviors of encapsulated microbubbles oscillating nonlinearly with ultrasonic excitation

The resonance behaviors of a few lipid-coated microbubbles acoustically activated in viscoelastic media were comprehensively examined via radius response analysis. The size polydispersity and random spatial distribution of the interacting microbubbles, the rheological properties of the lipid shell and the viscoelasticity of the surrounding medium were considered simultaneously. The obtained radius response curves present a successive occurrence of linear resonances, nonlinear harmonic and sub-harmonic resonances with the acoustic pressure increasing. The microbubble resonance is radius-, pressure- and frequency-dependent. Specifically, the maximum bubble expansion ratio at the main resonance peak increases but the resonant radius decreases as the ultrasound pressure increases, while both of them decrease with the ultrasound frequency increasing. Moreover, compared to an isolated microbubble case, it is found that large microbubbles in close proximity prominently suppress the resonant oscillations while slightly increase the resonant radii for both harmonic and subharmonic resonances, even leading to the disappearance of the subharmonic resonance with the influences increasing to a certain degree. In addition, the results also suggest that both the encapsulating shell and surrounding medium can substantially dampen the harmonic and subharmonic resonances while increase the resonant radii, which seem to be affected by the medium viscoelasticity to a greater degree rather than the shell properties. This work offers valuable insights into the resonance behaviors of microbubbles oscillating in viscoelastic biological media, greatly contributing to further optimizing their biomedical applications.

Exosomes and ultrasound: The future of theranostic applications

Biomaterials and pertaining formulations have been very successful in various diagnostic and therapeutic applications because of its ability to overcome pharmacological limitations. Some of them have gained significant focus in the recent decade for their theranostic properties. Exosomes can be grouped as biomaterials, since they consist of various biological micro/macromolecules and possess all the properties of a stable biomaterial with size in nano range. Significant research has gone into isolation and exploitation of exosomes as potential theranostic agent. However, the limitations in terms of yield, efficacy, and target specificity are continuously being addressed. On the other hand, several nano/microformulations are responsive to physical or chemical alterations and were successfully stimulated by tweaking the physical characteristics of the surrounding environment they are in. Some of them are termed as photodynamic, sonodynamic or thermodynamic therapeutic systems. In this regard, ultrasound and acoustic systems were extensively studied for its ability towards altering the properties of the systems to which they were applied on. In this review, we have detailed about the diagnostic and therapeutic applications of exosomes and ultrasound separately, consisting of their conventional applications, drawbacks, and developments for addressing the challenges. The information were categorized into various sections that provide complete overview of the isolation strategies and theranostic applications of exosomes in various diseases. Then the ultrasound-based disease diagnosis and therapy were elaborated, with special interest towards the use of ultrasound in enhancing the efficacy of nanomedicines and nanodrug delivery systems, Finally, we discussed about the ability of ultrasound in enhancing the diagnostic and therapeutic properties of exosomes, which could be the future of theranostics.

Preparation of ultrasound contrast agents: The exploration of the structure-echogenicity relationship of contrast agents based on neural network model

There is a need to standardize the process of micro/nanobubble preparation to bring it closer to clinical translation. We explored a neural network-based model to predict the structure-echogenicity relationship for the preparation and fabrication of ultrasound-enhanced contrast agents. Seven formulations were screened, and 109 measurements were obtained. An artificial neural network-multilayer perceptron (ANN-MLP) model was used. The original data were divided into the training and testing groups, which included 73 and 36 groups of data, respectively. The hidden layer was selected from three hidden layers and included bias. The classification graph showed that the predicted values of the training and testing groups were 76.7% and 66.7%, respectively. According to the receiver operating characteristic curve, the accuracy of different imaging effects could achieve a prediction rate of 88.1–96.5%. The percentage graph showed that the data were gradually converging. The predictive analysis curves of different ultrasound effects gradually approached stable value of Gain. Normalized importance predicted contributions for the Pk1, poly-dispersity index (PDI), and intensity account were 100%, 98.5%, and 89.7%, respectively. The application of the ANN-MLP model is feasible and effective for the exploration of the synthesis process of ultrasound contrast agents. 1,2-Distearoyl-sn-glycero-3 phosphoethanolamine-N (methoxy[polyethylene glycol]-2000) (DSPE PEG-2000) correlated highly with the success rate of contrast agent synthesis.

Emerging photodynamic/sonodynamic therapies for urological cancers: progress and challenges

Photodynamic therapy (PDT), and sonodynamic therapy (SDT) that developed from PDT, have been studied for decades to treat solid tumors. Compared with other deep tumors, the accessibility of urological tumors (e.g., bladder tumor and prostate tumor) makes them more suitable for PDT/SDT that requires exogenous stimulation. Due to the introduction of nanobiotechnology, emerging photo/sonosensitizers modified with different functional components and improved physicochemical properties have many outstanding advantages in cancer treatment compared with traditional photo/sonosensitizers, such as alleviating hypoxia to improve quantum yield, passive/active tumor targeting to increase drug accumulation, and combination with other therapeutic modalities (e.g., chemotherapy, immunotherapy and targeted therapy) to achieve synergistic therapy. As WST11 (TOOKAD® soluble) is currently clinically approved for the treatment of prostate cancer, emerging photo/sonosensitizers have great potential for clinical translation, which requires multidisciplinary participation and extensive clinical trials. Herein, the latest research advances of newly developed photo/sonosensitizers for the treatment of urological cancers, and the efficacy, as well as potential biological effects, are highlighted. In addition, the clinical status of PDT/SDT for urological cancers is presented, and the optimization of the photo/sonosensitizer development procedure for clinical translation is discussed.

Low-Intensity Focused Ultrasound Technique in Glioblastoma Multiforme Treatment

Glioblastoma is one of the central nervous system most aggressive and lethal cancers with poor overall survival rate. Systemic treatment of glioblastoma remains the most challenging aspect due to the low permeability of the blood-brain barrier (BBB) and blood-tumor barrier (BTB), limiting therapeutics extravasation mainly in the core tumor as well as in its surrounding invading areas. It is now possible to overcome these barriers by using low-intensity focused ultrasound (LIFU) together with intravenously administered oscillating microbubbles (MBs). LIFU is a non-invasive technique using converging ultrasound waves which can alter the permeability of BBB/BTB to drug delivery in a specific brain/tumor region. This emerging technique has proven to be both safe and repeatable without causing injury to the brain parenchyma including neurons and other structures. Furthermore, LIFU is also approved by the FDA to treat essential tremors and Parkinson's disease. It is currently under clinical trial in patients suffering from glioblastoma as a drug delivery strategy and liquid biopsy for glioblastoma biomarkers. The use of LIFU+MBs is a step-up in the world of drug delivery, where onco-therapeutics of different molecular sizes and weights can be delivered directly into the brain/tumor parenchyma. Initially, several potent drugs targeting glioblastoma were limited to cross the BBB/BTB; however, using LIFU+MBs, diverse therapeutics showed significantly higher uptake, improved tumor control, and overall survival among different species. Here, we highlight the therapeutic approach of LIFU+MBs mediated drug-delivery in the treatment of glioblastoma.

Biosynthetic Gas Vesicles from Halobacteria NRC-1: A Potential Ultrasound Contrast Agent for Tumor Imaging

Ultrasound contrast agents are valuable for diagnostic imaging and drug delivery. Generally, chemically synthesized microbubbles (MBs) are micro-sized particles. Particle size is a limiting factor for the diagnosis and treatment of many extravascular diseases. Recently, gas vesicles (GVs) from some marine bacteria and archaea have been reported as novel nanoscale contrast agents, showing great potential for biomedical applications. However, most of the GVs reported in the literature show poor contrast imaging capabilities due to their small size, especially for the in vivo condition. In this study, we isolated the rugby-ball-shaped GVs from Halobacteria NRC-1 and characterized their contrast imaging properties in vitro and in vivo. Our results showed that GVs could produce stable and strong ultrasound contrast signals in murine liver tumors using clinical diagnostic ultrasound equipment at the optimized parameters. Interestingly, we found these GVs, after systemic administration, were able to perfuse the ischemic region of a tumor where conventional lipid MBs failed, producing a 6.84-fold stronger contrast signal intensity than MBs. Immunohistochemistry staining assays revealed that the nanoscale GVs, in contrast to the microscale MBs, could penetrate through blood vessels. Thus, our study proved these biosynthesized GVs from Halobacterium NRC-1 are useful for future molecular imaging and image-guided drug delivery.

FN3 linked nanobubbles as a targeted contrast agent for US imaging of cancer-associated human PD-L1

PD-L1 (programmed death-ligand 1) targeted therapies may be useful for several cancers. The use of non-invasive diagnostic and prognostic molecular imaging platforms could improve clinical assessment of PD-L1 tumor status during these therapies. Contrast enhanced ultrasound molecular imaging (CE-USMI) techniques may offer versatile and cost-effective ways to detect and quantify the expression levels of cellular targets in vivo. However, conventional use of microbubbles as a blood pool contrast agent for CE-USMI is limited to accessing intravascular biomarkers rather than reflecting the tumor molecular status. Using a microfluidic based reconstruction process we therefore developed ultra-stable nanobubbles (NBs) as a contrast agent for molecular imaging of vascular and extravascular cell surface markers. We then functionalized these NBs by covalently linking to nanobody (FN3_hPD-L1) targeting human (h)PD-L1 to measure the expression of human PD-L1 in the tumor microenvironment (TME) in vivo. We showed the specific binding of hPD-L1 targeted NBs in cell culture, and in xenografted mouse models of hPD-L1 expressing CT26 tumors. CE-USMI of hPD-L1 in the TME in vivo showed ~3-fold increase in contrast signal compared to non-targeted NBs. Overall, in vivo use of CE-USMI with hPD-L1 targeted NBs has the potential for clinical translation and imaging of human cancers during immunotherapy, and for prognostic evaluation of patient response to PD-L1 targeted immunotherapy.