Circulating Magnetic Microbubbles for Localized Real-Time Control of Drug Delivery by Ultrasonography-Guided Magnetic Targeting and Ultrasound

Image-guided and target-selective modulation of drug delivery by external physical triggers at the site of pathology has the potential to enable tailored control of drug targeting. Magnetic microbubbles that are responsive to magnetic and acoustic modulation and visible to ultrasonography have been proposed as a means to realize this drug targeting strategy. To comply with this strategy in vivo, magnetic microbubbles must circulate systemically and evade deposition in pulmonary capillaries, while also preserving magnetic and acoustic activities in circulation over time. Unfortunately, challenges in fabricating magnetic microbubbles with such characteristics have limited progress in this field. In this report, we develop magnetic microbubbles (MagMB) that display strong magnetic and acoustic activities, while also preserving the ability to circulate systemically and evade pulmonary entrapment. Methods: We systematically evaluated the characteristics of MagMB including their pharmacokinetics, biodistribution, visibility to ultrasonography and amenability to magneto-acoustic modulation in tumor-bearing mice. We further assessed the applicability of MagMB for ultrasonography-guided control of drug targeting. Results: Following intravenous injection, MagMB exhibited a 17- to 90-fold lower pulmonary entrapment compared to previously reported magnetic microbubbles and mimicked circulation persistence of the clinically utilized Definity microbubbles (>10 min). In addition, MagMB could be accumulated in tumor vasculature by magnetic targeting, monitored by ultrasonography and collapsed by focused ultrasound on demand to activate drug deposition at the target. Furthermore, drug delivery to target tumors could be enhanced by adjusting the magneto-acoustic modulation based on ultrasonographic monitoring of MagMB in real-time. Conclusions: Circulating MagMB in conjunction with ultrasonography-guided magneto-acoustic modulation may provide a strategy for tailored minimally-invasive control over drug delivery to target tissues

Indirect Low-Intensity Ultrasonic Stimulation for Tissue Engineering

Low-intensity ultrasound (LIUS) treatment has been shown to increase mass transport, which could benefit tissue grafts during the immediate postimplant period, when blood supply to the implanted tissue is suboptimal. In this in vitro study, we investigated effects of LIUS stimulation on dye diffusion, proliferation, metabolism, and tropomyosin expression of muscle cells (C2C12) and on tissue viability and gene expression of human adipose tissue organoids. We found that LIUS increased dye diffusion within adjacent tissue culture wells and caused anisotropic diffusion patterns. This effect was confirmed by a hydrophone measurement resulting in acoustic pressure 150–341 Pa in wells. Cellular studies showed that LIUS significantly increased proliferation, metabolic activity, and expression of tropomyosin. Adipose tissue treated with LIUS showed significantly increased metabolic activity and the cells had similar morphology to normal unilocular adipocytes. Gene analysis showed that tumor necrosis factor-alpha expression (a marker for tissue damage) was significantly lower for stimulated organoids than for control groups. Our data suggests that LIUS could be a useful modality for improving graft survival in vivo

Development of a magnetically-targeted, MRI-monitored nano-platform for brain tumor drug delivery.

Brain tumors inflict a heavy burden of morbidity and high risk of death. Currently employed treatment modalities fail to substantially improve these dismal outcomes. Proteins have recently emerged as a new class of agent with potent anti-glioma activity. However, their therapeutic potential has been limited by formidable challenges in their delivery to brain tumor sites. This dissertation research investigated the feasibility of utilizing magnetic nanoparticles as a carrier for delivery of proteins to brain tumor lesions. Magnetic nanoparticles composed of a superparamagnetic core and a biocompatible polymeric shell presented a promising platform for this application. The core provided high saturation magnetization of 108 emu/g Fe, suggesting that the particles would be amenable to capture within a tumor lesion by an external magnetic field, a strategy termed magnetic targeting. Moreover, high T2 relaxivity of 43 s-1mM -1 indicated a possibility for non-invasive monitoring of nanocarrier delivery to the target site by in vivo T2 MRI. Furthermore, the polysaccharide shell of the nanoparticles allowed successful loading of a model protein, beta-Galactosidase (betaGal), with a high loading capacity of 7.5% w/w. To deliver the nanocarriers to brain tumor lesions in vivo, an improved magnetic targeting methodology has been developed. This methodology involved administration of nanoparticles via carotid artery, optimization of the magnet configuration, and MRI-guided animal alignment with respect to mapped magnetic field topography. Animal studies in rats harboring 9L-gliosarcomas revealed that utilization of the developed methodology provided a 4.7-fold increase in tumor betaGal activity (636 +/- 42 muU/g tissue) compared to non-targeted control animals (134 +/- 46 muU/g tissue). In addition, high tumor selectivity of protein localization was observed, as tumor tissues displayed 7.5-fold higher betaGal activity (636 +/- 42 muU/g tissue) than the contra-lateral brain (85 +/- 30 muU/g tissue). Moreover, the delivery of the betaGal-loaded nanocarrier to the target site was successfully validated and quantified with non-invasive T2 MRI. In conclusion, this work established the plausibility of protein delivery to brain tumor lesions using MRI-monitored magnetically-responsive nanoplatform in conjunction with developed magnetic targeting methodology. This accomplishment may pave the way to realization of efficacious protein-based therapies for brain cancer treatment.Ph.D.Applied SciencesBiomedical engineeringHealth and Environmental SciencesMaterials scienceOncologyPharmacologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/127130/2/3392772.pd

Spatial Control of Gene Expression by Nanocarriers Using Heparin Masking and Ultrasound-Targeted Microbubble Destruction

We developed a method to spatially control gene expression following nonviral delivery of DNA. This method includes surface-modifying DNA nanocarriers with heparin to inhibit passive gene transfer in both the target and the off-target tissues and using ultrasound-targeted microbubble destruction (UTMD) to selectively activate heparin-inhibited gene transfer at the target site. We observed that the engraftment of heparin onto the surface of cationic liposomes reduced off-target gene expression in the liver, a major site of nanoplex accumulation, by more than 700-fold compared to the nonheparinized PEGylated liposomes. We further observed that tumor-directed UTMD increased gene transfer with heparin-modified nanoplexes by more than 10-fold. This method augmented tumor-to-liver selectivity of gene expression by 4000-fold compared to controls. We conclude that heparinization of DNA nanocarriers in conjunction with localized activation of gene transfer by UTMD may enable greater spatial control over genetic therapy. Keywords: gene delivery, spatial control, tumor targeting, gene nano carriers, heparin surface masking, microbubbles, ultrasoundNational Institutes of Health (U.S.) (Grant U54 CA151884

Drug Delivery Interfaces in the 21st Century: From Science Fiction Ideas to Viable Technologies

Early science fiction envisioned the future of drug delivery as targeted micrometer-scale submarines and "cyborg" body parts. Here we describe the progression of the field toward technologies that are now beginning to capture aspects of this early vision. Specifically, we focus on the two most prominent types of systems in drug delivery: the intravascular micro/nano drug carriers for delivery to the site of pathology and drug-loaded implantable devices that facilitate release with the predefined kinetics or in response to a specific cue. We discuss the unmet clinical needs that inspire these designs, the physiological factors that pose difficult challenges for their realization, and viable technologies that promise robust solutions. We also offer a perspective on where drug delivery may be in the next 50 years based on expected advances in material engineering and in the context of future diagnostics. Keywords: drug delivery; drug carriers; nanotechnology; controlled release implants; physiological barriers; pharmacokinetics; translational medicineNational Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant 1F32EB015835-01

Size-Controlled Iron Oxide Nanoplatforms with Lipidoid-Stabilized Shells for Efficient Magnetic Resonance Imaging-Trackable Lymph Node Targeting and High-Capacity Biomolecule Display

Nanoplatforms for biomolecule delivery to the lymph nodes have attracted considerable interest as vectors for immunotherapy. Core–shell iron oxide nanoparticles are particularly appealing because of their potential as theranostic magnetic resonance imaging (MRI)-trackable vehicles for biomolecule delivery. The key challenge for utilizing iron oxide nanoparticles in this capacity is control of their coating shells to produce particles with predictable size. Size determines both the carrier capacity for biomolecule display and the carrier ability to target the lymph nodes. In this study, we develop a novel coating method to produce core–shell iron oxide nanoparticles with controlled size. We utilize lipidlike molecules to stabilize self-assembled lipid shells on the surface of iron oxide nanocrystals, allowing the formation of consistent coatings on nanocrystals of varying size (10–40 nm). We further demonstrate the feasibility of leveraging the ensuing control of nanocarrier size for optimizing the carrier functionalities. Coated nanoparticles with 10 and 30 nm cores supported biomolecule display at 10-fold and 200-fold higher capacities than previously reported iron oxide nanoparticles, while preserving monodisperse sub-100 nm size populations. In addition, accumulation of the coated nanoparticles in the lymph nodes could be tracked by MRI and at 1 h post injection demonstrated significantly enhanced lymph node targeting. Notably, lymph node targeting was 9–40 folds higher than that for previously reported nanocarriers, likely due to the ability of these nanoparticles to robustly maintain their sub-100 nm size in vivo. This approach can be broadly applicable for rational design of theranostic nanoplatforms for image-monitored immunotherapy