Development of antibody-carrying microbubbles based on clinically available ultrasound contrast agent for targeted molecular imaging: a preliminary chemical study

Toward Ultrasound Molecular Imaging of Endothelial Dysfunction in Diabetes: Targets, Strategies, and Challenges

Diabetes vasculopathy is a significant complication of diabetes mellitus (DM), and early identification and timely intervention can effectively slow the progression. Accumulating studies have shown that diabetes causes vascular complications directly or indirectly through a variety of mechanisms. Direct imaging of the endothelial molecular changes not only identifies the early stage of diabetes vasculopathy but also sheds light on the precise treatment. Targeted ultrasound contrast agent (UCA)-based ultrasound molecular imaging (UMI) can noninvasively detect the expression status of molecular biomarkers overexpressed in the vasculature, thereby being a potential strategy for the diagnosis and treatment response evaluation of DM. Amounts of efforts have been focused on identification of the molecular targets expressed in the vasculature, manufacturing strategies of the targeted UCA, and the clinical translation for the diagnosis and evaluation of therapeutic efficacy in both micro- and macrovasculopathy in DM. This review summarizes the latest research progress on endothelium-targeted UCA and discusses their promising future and challenges in diabetes vasculopathy theranostics.

Sonazoid-Conjugated Natural Killer Cells for Tumor Therapy and Real-Time Visualization by Ultrasound Imaging

Various cell therapy strategies, including chimeric antigen receptor-expressing T or natural killer (NK) cells and cell-mediated drug delivery, have been developed for tumor eradication. However, the efficiency of these strategies against solid tumors remains unclear. We hypothesized that real-time control and visualization of therapeutic cells, such as NK cells, would improve their therapeutic efficacy against solid tumors. In this study, we engineered Sonazoid microbubble-conjugated NK (NK_Sona) cells and demonstrated that they were detectable by ultrasound imaging in real-time and maintained their functions. The Sonazoid microbubbles on the cell membrane did not affect the cytotoxicity and viability of the NK cells in vitro. Additionally, the NK_Sona cells could be visualized by ultrasound imaging and inhibited tumor growth in vivo. Taken together, our findings demonstrate the feasibility of this new approach in the use of therapeutic cells, such as NK cells, against solid tumors.

Near-Infrared Light-Driven Multifunctional Tubular Micromotors for Treatment of Atherosclerosis

One of the difficulties in atherosclerosis treatment is that the ablation of inflammatory macrophages, repair of vascular endothelial injury, and anti-tissue proliferation should be considered. However, there are few studies that can solve the abovementioned problems simultaneously. Herein, we present a kind of near-infrared (NIR) light-driven multifunctional mesoporous/macroporous tubular micromotor which can rapidly target the damaged blood vessels and release different drugs. Their motion effect can promote themselves to penetrate into the plaque site, and the generated heat effect caused by NIR irradiation can realize the photothermal ablation of inflammatory macrophages. Furthermore, these micromotors can rapidly release the vascular endothelial growth factor for endothelialization and slowly release paclitaxel for antiproliferation to achieve synergistic treatment of atherosclerosis. In vivo results demonstrated that the micromotors can achieve a good therapeutic effect for atherosclerosis. This kind of micro/nanomotor technology with a complex porous structure for drug loading will bring a more potential treatment platform for the disease.

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.

Platelet-derived nanomotor coated balloon for atherosclerosis combination therapy

A nanorobot is used to realize deep penetration of drugs in atherosclerotic plaque, photothermal ablation of inflammatory macrophages and long-term anti-proliferation effects.

Multimodal Molecular Imaging: Current Status and Future Directions

Molecular imaging has emerged at the end of the last century as an interdisciplinary method involving in vivo imaging and molecular biology aiming at identifying living biological processes at a cellular and molecular level in a noninvasive manner. It has a profound role in determining disease changes and facilitating drug research and development, thus creating new medical modalities to monitor human health. At present, a variety of different molecular imaging techniques have their advantages, disadvantages, and limitations. In order to overcome these shortcomings, researchers combine two or more detection techniques to create a new imaging mode, such as multimodal molecular imaging, to obtain a better result and more information regarding monitoring, diagnosis, and treatment. In this review, we first describe the classic molecular imaging technology and its key advantages, and then, we offer some of the latest multimodal molecular imaging modes. Finally, we summarize the great challenges, the future development, and the great potential in this field.

Simplified Preparation of αvβ3 Integrin-Targeted Microbubbles Based on a Clinically Available Ultrasound Contrast Agent: Validation in a Tumor-Bearing Mouse Model

The usefulness of ultrasound molecular imaging with α_vβ₃ integrin-targeted microbubbles for detecting tumor angiogenesis has been demonstrated. Recently, we developed α_vβ₃ integrin-targeted microbubbles by modifying clinically available microbubbles (Sonazoid, Daiichi-Sankyo Pharmaceuticals, Tokyo, Japan) with a secreted glycoprotein (lactadherin). The aims of our present study were to simplify the preparation of lactadherin-bearing Sonazoid and to examine the diagnostic utility of lactadherin-bearing Sonazoid for α_vβ₃ integrin-expressing tumor vessels by using SK-OV-3-tumor-bearing mice. By incubating 1.2 × 10⁷ Sonazoid microbubbles with 1.0 µg lactadherin, the complicated washing and centrifugation steps during the microbubble preparation could be omitted with no significant reduction in labeling ratio of lactadherin-bearing Sonazoid. In addition, the number of Sonazoid microbubbles accumulated in the SK-OV-3 tumor was significantly increased by modifying Sonazoid with lactadherin. Our data suggest that the lactadherin-bearing Sonazoid is an easily prepared and potentially clinically translatable targeted microbubble for α_vβ₃ integrin-expressing vessels.

Recent development of biotin conjugation in biological imaging, sensing, and target delivery

Despite encouraging results from preliminary studies of anticancer therapies, the lack of tumor specificity remains an important issue in the modern pharmaceutical industry. New findings indicate that biotin or biotin-conjugates could be favorably assimilated by tumor cells that over-express biotin-selective transporters. Furthermore, biotin can form stable complexes with avidin and its bacterial counterpart streptavidin. The strong bridging between avidin and biotin moieties on other molecules is a proven adaptable tool with broad biological applications. Under these circumstances, a biotin moiety is certainly an attractive choice for live-cell imaging, biosensing, and target delivery.

Feasibility of lactadherin-bearing clinically available microbubbles as ultrasound contrast agent for angiogenesis

OBJECTIVES

Phagocytosis of apoptotic cells is carried out through bridging of phosphatidylserine (PS)-expressing apoptotic cells and integrin αvβ3-expressing phagocytes with lactadherin. The objective of this study was to examine whether microbubbles targeted to integrin αvβ3 could be produced by conjugating a PS-containing clinically available ultrasound contrast agent with lactadherin.

MATERIALS AND METHODS

PS-containing perfluorobutane-filled microbubbles were incubated with R-phycoerythrin (PE)-labeled lactadherin, and the presence of PE-positive bubbles was examined by FACS analysis. Secondly, the attachment of lactadherin to integrin αvβ3-expressing cells (human umbilical vein endothelial cells (HUVEC)) was also examined by FACS analysis. Finally, the adhesion of PS-containing bubbles to HUVEC was examined using a parallel plate flow chamber. The number of adherent bubbles with or without the intermediation of lactadherin was compared.

RESULTS

The more lactadherin was added to the bubble suspension, the more PE-positive bubbles were detected. The size of bubbles was not increased even after conjugation with lactadherin (2.90 ± 0.04 vs. 2.81 ± 0.02 μm). Binding between lactadherin and HUVEC was also confirmed by FACS analysis. The parallel plate flow chamber study revealed that the number of PS-containing bubbles adherent to HUVEC was increased about five times by the intermediation of lactadherin (12.1 ± 6.0 to 58.7 ± 33.1 bubbles).

CONCLUSION

Because integrin αvβ3 is well-known to play a key role in angiogenesis, the complex of PS-containing bubbles and lactadherin has feasibility as a clinically translatable targeted ultrasound contrast agent for angiogenesis.