Novel dual-mode nanobubbles as potential targeted contrast agents for female tumors exploration

Ultrasound Molecular Imaging and Its Applications in Cancer Diagnosis and Therapy

Ultrasound imaging is regarded as a highly sensitive imaging modality used in routine clinical examinations. Over the last several decades, ultrasound contrast agents have been widely applied in ultrasound molecular cancer imaging to improve the detection, characterization, and quantification of tumors. To date, a few new potential preclinical and clinical applications regarding ultrasound molecular cancer imaging are being investigated. This review presents an overview of the various kinds of ultrasound contrast agents employed in ultrasound molecular imaging and advanced imaging techniques using these contrast agents. Additionally, we discuss the recent enormous development of ultrasound contrast agents in the relevant preclinical and clinical applications, highlight the recent challenges which need to be overcome to accelerate the clinical translation, and discuss the future perspective of ultrasound molecular cancer imaging using various contrast agents. As a highly promising and valuable tumor-specific imaging technique, it is believed that ultrasound molecular imaging will pave an accurate and efficient way for cancer diagnosis.

Nanosized Contrast Agents in Ultrasound Molecular Imaging

Applying nanosized ultrasound contrast agents (nUCAs) in molecular imaging has received considerable attention. nUCAs have been instrumental in ultrasound molecular imaging to enhance sensitivity, identification, and quantification. nUCAs can achieve high performance in molecular imaging, which was influenced by synthetic formulations and size. This review presents an overview of nUCAs from different synthetic formulations with a discussion on imaging and detection technology. Then we also review the progress of nUCAs in preclinical application and highlight the recent challenges of nUCAs.

Development and application of ultrasound contrast agents in biomedicine

With the rapid development of molecular imaging, ultrasound (US) medicine has evolved from traditional imaging diagnosis to integrated diagnosis and treatment at the molecular level. Ultrasound contrast agents (UCAs) play a crucial role in the integration of US diagnosis and treatment. As the micro-bubbles (MBs) in UCAs can enhance the cavitation effect and promote the biological effect of US, UCAs have also been studied in the fields of US thrombolysis, mediated gene transfer, drug delivery, and high intensity focused US. The application range of UCAs is expanding, and the value of their applications is improving. This paper reviews the development and application of UCAs in biomedicine in recent years, and the existing problems and prospects are pointed out.

Preparation of multifunctional nanobubbles and their application in bimodal imaging and targeted combination therapy of early pancreatic cancer

Pancreatic cancer will gradually become the second leading cause of cancer death due to its poor suitability for surgical treatment, frequent recurrence and metastasis, and insensitivity to radiotherapy and chemotherapy. Strategies for precise early detection and effective targeted treatment of pancreatic cancer are urgently needed. Because of its unique advantages, molecular targeted contrast-enhanced ultrasound imaging (CEUI) has generated new opportunities to overcome this challenge. The aim of this study was to explore multifunctional nanobubbles named IR780-NBs-DTX as novel ultrasound contrast agents (UCAs) for dual-mode targeted imaging and photothermal ablation combined with chemotherapy for pancreatic cancer. An optimized “film hydration method” was used to prepare IR780-NBs-DTX in this research. The characteristics and ability of the new UCAs were detected via in vitro, in vivo and ex vivo experiments. The initial dose of 0.15 mg IR-780 iodide/1.0 mg DTX was considered to be the best formula for IR780-NBs-DTX, and the concentration of 6 ×10⁶ bubbles/mL was best for CEUI. The excellent characteristics of IR780-NBs-DTX, including a uniform nanoscale particle size (349.8± 159.1 nm, n= 3), good performance in dual-mode imaging, high stability and reliable biocompatibility, were also proven. In the in vitro cell experiments, IR780-NBs-DTX targeted more pancreatic cancer cells than the control treatments, and the targeting rate was approximately 95.6± 1.7%. Under irradiation with an 808 nm laser, most cells died. Furthermore, the in vivo study demonstrated that IR780-NBs-DTX could precisely detect pancreatic cancer through near infrared fluorescence (NIRF) imaging and CEUI, and the tumor almost disappeared at 18 days after combined treatment. In ex vivo experiments, immunohistochemistry (IHC) and immunofluorescence (IF) showed that the expression of HSP70 increased and that of PCNA decreased, and many apoptotic tumor cells were observed by TUNEL staining in the IR780-NBs-DTX group. The newly prepared IR780-NBs-DTX are novel nanosized UCAs with high efficiency for dual-mode molecular targeted imaging and combined therapy, and they may have future potential applications in the precise detection and effective targeted therapy of small and metastatic lesions in the early stage of pancreatic cancer.

A new strategy for accurate targeted diagnosis and treatment of cutaneous malignant melanoma: dual-mode phase-change lipid nanodroplets as ultrasound contrast agents

Background

Currently, effective detection and treatment of cutaneous malignant melanoma (CMM) still face severe challenges. Ultrasound molecular imaging as a noninvasive and easy-to-operate method is expected to bring improvements for tumor detection.

Purpose

The aim of this research is to prepare novel phase-change ultrasound contrast agents, Nds-IR780, which can perform not only dual-mode molecule-targeted imaging but also targeted photothermal therapy for CMM.

Methods

A double emulsion process was used to prepare the Nds-IR780. Then, the entrapment rate and drug loading of IR-780 iodide in Nds-IR780 were detected by high-performance liquid chromatography. The biocompatibility of Nds-IR780 was evaluated by a CCK-8 assay and the characteristics and stability of that were verified through the particle size analyzer, laser scanning confocal microscopy (LSCM) and transmission electron microscopy (TEM). The abilities of dual-mode molecule-targeted imaging and targeted photothermal therapy for Nds-IR780 were confirmed via the in vitro and in vivo experiments.

Results

Nds-IR780 had good size distribution, polydispersity index, stability and biosafety. The in vitro and in vivo experiments confirmed that Nds-IR780 were capable of targeting CMM cells with high affinity (22.4±3.2%) and facilitating dual-mode imaging to detect the primary lesion and sentinel lymph nodes (SLNs) of CMM. Furthermore, the photothermal ablation of CMM mediated by Nds-IR780 was very effective in vivo.

Conclusion

The newly prepared Nds-IR780 were observed to be effective targeted theranostic probe for the precise detection and targeted treatment of CMM.

Time-intensity-curve Analysis and Tumor Extravasation of Nanobubble Ultrasound Contrast Agents

Our group recently presented a simple strategy using the non-ionic surfactant, Pluronic, as a size control excipient to produce nanobubbles in the 100-nm range, which exhibited stability and echogenicity on par with clinically available microbubbles. The objective of the present study was to evaluate biodistribution and extravasation of the Pluronic-stabilized lipid nanobubbles compared with microbubbles in 2 experimental tumor models in mice. Standard lipid-stabilized perfluoropropane bubbles (Pluronic L10) and lipid-stabilized perfluoropropane nanobubbles were intravenously injected into mice bearing either an orthotopic mouse breast cancer (BC4 T1) or subcutaneous mouse ovarian cancer (OVCAR-3) through the tail vein to perform perfusion dynamic studies. No significant differences between the nanobubble and microbubble groups were observed in the peak enhancement of the 3 tested regions (tumor, liver and kidney). However, the decay rates of nanobubble in the tumor and kidney of BC4 T1-bearing mice, as well as in mice with OVRCAR-3 tumors were significantly slower than those of the microbubble. To quantify extravasation, fluorescently labeled bubbles were intravenously injected into mice bearing the same tumors. Histologic analysis showed that nanobubbles were retained in tumor tissue to a greater extent compared with microbubbles in both tumor models at the 3-h time point. Our results demonstrate unique nanobubble behavior compared with microbubbles and support augmented application of these agents in ultrasound molecular imaging and drug delivery beyond the tumor vasculature.

A Novel Bimodal Imaging Agent Targeting HER2 Molecule of Breast Cancer

Nanobubble (NB), a newly developed nanoscaled ultrasound contrast agent (UCA) for molecular imaging, has been widely researched for these years. Targeting it with functional molecule, nanobubble can adhere selectively to cellular epitopes and receptors outside the vasculature via enhanced permeability and retention (EPR) effect of tumor blood vessel. To enhance the targeting rate of our previous prepared NBs-Affibody for HER2 (+) breast cancer imaging, we introduced a near-infrared fluorescent (NIRF) dye, IR783, in this study to enhance tumor-specific targeting rate and provide a promising modality for dual-mode imaging. The prepared IR783-NBs-Affibody presented a uniform nanoscale size around 482.7 ± 54.3 nm, good biosecurity, and stability over time. The encapsulation efficiency (EE) of IR-783 was 15.09% in the conjugates leading to a successful NIR fluorescence and ultrasound enhancement imaging ex vivo. IR783-NBs-Affibody was able to automatically accumulate on BT474 cells with a highly increased targeting rate of 85.4% compared with previous NBs-Affibody of 26.6%, while Affibody-guided HER2 binding was only found in HER2-positive cell lines (BT474 and T-47D). The newly developed IR783-NBs-Affibody is characterized with favorable HER2 targeting ability and bimodal imaging capability for breast cancer. Thus, IR783-NBs-Affibody holds great potential in molecular diagnosis for patients with breast cancer.

Targeted Soft Biodegradable Glycine/PEG/RGD-Modified Poly(methacrylic acid) Nanobubbles as Intelligent Theranostic Vehicles for Drug Delivery

The development of multifunctional ultrasound contrast agents has inspired considerable interest in the application of biomedical imaging and anticancer therapeutics. However, combining multiple components that can preferentially accumulate in tumors in a nanometer scale poses one of the major challenges in targeting drug delivery for theranostic application. Herein, reflux-precipitation polymerization, and N-(3-(dimethylamino)propyl)-N'-ethylcarbodiimide-meditated amidation reaction were introduced to effectively generate a new type of soft glycine/poly(ethylene glycol) (PEG)/RGD-modified poly(methacrylic acid) nanobubbles with a uniform morphology and desired particle size (less than 100 nm). Because of the enhanced biocompatibility resulting from the glycine modification, over 80% of the cells survived, even though the dosage of glycine-modified polymeric nanobubbles was up to 5 mg/mL. By loading doxorubicin as an anticancer drug and perfluorohexane as an ultrasound probe, the resulting glycine/PEG/RGD-modified nanobubbles showed remarkable cancer therapeutic efficacy and a high quality of ultrasonic imaging; thus, the ultrasonic signal exhibited a 1.47-fold enhancement at the tumor site after intravenous injection. By integrating diagnostic and therapeutic functions into a single nanobubble, the new type of theranostic nanobubbles offers a promising strategy to monitor the therapeutic effects, giving important insights into the ultrasound-traced and enhanced targeting drug delivery in biomedical applications.