Sensing the delivery and endocytosis of nanoparticles using magneto-photo-acoustic imaging

Evaluation of cellular stress responses in magnetomotive ultrasound

Early and accurate diagnoses are important for successful cancer treatment. Lymph node involvement is often critical, and magnetomotive ultrasound (MMUS) has been proposed for its detection and characterization. MMUS relies on a magnetic contrast agent, for example, iron oxide nanoparticles, delivered to the tissue of interest, magnetically set in motion and detected using ultrasound. The magneto-mechanical interaction has not previously been evaluated on a cellular level. Here we demonstrate uptake and dose-dependent retention of magnetic nanoparticles in two human adenocarcinoma cell lines, with <10% cytotoxicity which did not increase following magnetic excitation. Further, the oxidative stress levels were not affected by magnetic particles or force. Thus, we found no evidence of adverse effects from the magneto-mechanical interactions under these conditions.

Modelling of magnetic microbubbles to evaluate contrast enhanced magnetomotive ultrasound in lymph nodes - a pre-clinical study

OBJECTIVES

Despite advances in MRI the detection and characterisation of lymph nodes in rectal cancer remains complex, especially when assessing the response to neoadjuvant treatment. An alternative approach is functional imaging, previously shown to aid characterisation of cancer tissues. We report proof of concept of the novel technique Contrast-Enhanced Magneto-Motive Ultrasound (CE-MMUS) to recover information relating to local perfusion and lymphatic drainage, and interrogate tissue mechanical properties through magnetically induced deformations.

METHODS

The feasibility of the proposed application was explored using a combination of experimental animal and phantom ultrasound imaging, along with finite element analysis. First, contrast-enhanced ultrasound imaging on one wild type mouse recorded lymphatic drainage of magnetic microbubbles after bolus injection. Second, tissue phantoms were imaged using MMUS to illustrate the force- and elasticity dependence of the magnetomotion. Third, the magnetomechanical interactions of a magnetic microbubble with an elastic solid were simulated using finite element software.

RESULTS

Accumulation of magnetic microbubbles in the inguinal lymph node was verified using contrast enhanced ultrasound, with peak enhancement occurring 3.7 s post-injection. The magnetic microbubble gave rise to displacements depending on force, elasticity, and bubble radius, indicating an inverse relation between displacement and the latter two.

CONCLUSION

Combining magnetic microbubbles with MMUS could harness the advantages of both techniques, to provide perfusion information, robust lymph node delineation and characterisation based on mechanical properties.

ADVANCES IN KNOWLEDGE

(a) Lymphatic drainage of magnetic microbubbles visualised using contrast-enhanced ultrasound imaging and (b) magnetomechanical interactions between such bubbles and surrounding tissue could both contribute to (c) robust detection and characterisation of lymph nodes.

Magnetomotive Ultrasound Imaging Systems: Basic Principles and First Applications

This review discusses magnetomotive ultrasound, which is an emerging technique that uses superparamagnetic iron oxide nanoparticles as a contrast agent. The key advantage of using nanoparticle-based contrast agents is their ability to reach extravascular targets, whereas commercial contrast agents for ultrasound comprise microbubbles confined to the blood stream. This also extends possibilities for molecular imaging, where the contrast agent is labeled with specific targeting molecules (e.g., antibodies) so that pathologic tissue may be visualized directly. The principle of action is that an external time-varying magnetic field acts to displace the nanoparticles lodged in tissue and thereby their immediate surrounding. This movement is then detected with ultrasound using frequency- or time-domain analysis of echo data. As a contrast agent already approved for magnetic resonance imaging (MRI) by the US Food and Drug Administration, there is a shorter path to clinical translation, although safety studies of magnetomotion are necessary, especially if particle design is altered to affect biodistribution or signal strength. The external modulated magnetic field may be generated by electromagnets, permanent magnets, or a combination of the two. The induced nanoparticle motion may also reveal mechanical material properties of tissue, healthy or diseased, one of several interesting potential future aspects of the technique.

Remarkable In Vivo Nonlinear Photoacoustic Imaging Based on Near-Infrared Organic Dyes

Two near-infrared dyes featuring good dispersion and light-harvesting property present a remarkable nonlinear photoacoustic response in vitro and in vivo comparing with conventional gold nanorods. This study benefits the fabrication of drug delivery platforms with accurate targeting and control effect under photoacoustic image guidance.

Nanotechnology in diagnosis and treatment of coronary artery disease

Nanotechnology could provide a new complementary approach to treat coronary artery disease (CAD) which is now one of the biggest killers in the Western world. The course of events, which leads to atherosclerosis and CAD, involves many biological factors and cellular disease processes which may be mitigated by therapeutic methods enhanced by nanotechnology. Nanoparticles can provide a variety of delivery systems for cargoes such as drugs and genes that can address many problems within the arteries. In order to improve the performance of current stents, nanotechnology provides different nanomaterial coatings, in addition to controlled-release nanocarriers, to prevent in-stent restenosis. Nanotechnology can increase the efficiency of drugs, improve local and systematic delivery to atherosclerotic plaques and reduce the inflammatory or angiogenic response after intravascular intervention. Nanocarriers have potential for delivery of imaging and diagnostic agents to precisely targeted destinations. This review paper will cover the current applications and future outlook of nanotechnology, as well as the main diagnostic methods, in the treatment of CAD.