Pharmacokinetic analysis reveals limitations and opportunities for nanomedicine targeting of endothelial and extravascular compartments of tumours.

Targeting of nanoparticles to tumours can potentially improve the specificity of imaging and treatments. We have developed a multicompartmental pharmacokinetic model in order to analyse some of the factors that control efficiency of targeting to intravascular (endothelium) and extravascular (tumour cells and stroma) compartments. We make the assumption that transport across tumour endothelium is an important step for subsequent nanoparticle accumulation in the tumour (area-under-the-curve, AUC) regardless of entry route (interendothelial and transendothelial routes) and study this through a multicompartmental simulation.

Removal of ligand-bound liposomes from cell surfaces by microbubbles exposed to ultrasound.

Gas-filled microbubbles attached to cell surfaces can interact with focused ultrasound to create microstreaming of nearby fluid. We directly observed the ultrasound/microbubble interaction and documented that under certain conditions fluorescent particles that were attached to the surface of live cells could be removed. Fluorescently labeled liposomes that were larger than 500 nm in diameter were attached to the surface of endothelial cells using cRGD targeting to αvβ3 integrin.

Isolation of Breast cancer CTCs with multitargeted buoyant immunomicrobubbles.

Circulating tumor cells (CTCs) are extremely rare cells found in blood of metastatic cancer patients. There is a need for inexpensive technologies for fast enrichment of CTCs from large blood volumes. Previous data showed that antibody-conjugated lipid shell immuno-microbubbles (MBs) bind and isolate cells from biological fluids by flotation.

Longitudinal monitoring of skin accumulation of nanocarriers and biologicals with fiber optic near infrared fluorescence spectroscopy (FONIRS).

Systemically injected drug delivery systems distribute into various organs and tissues, including liver, spleen and kidneys. Recent reports pointed out a significant accumulation of systemically injected nanoparticles in the skin. Skin constitutes the largest organ in the body with important immune functions, and accumulation of drug delivery systems could have significant implications for skin toxicity in living subjects.

Optical detection of harmonic oscillations in fluorescent dye-loaded microbubbles ensonified by ultrasound.

A new optical contrast agent has been developed by exposing dye-loaded microbubbles to a rapidly-cooled thermal treatment to homogenize the dye distribution across the surface. Ultrasound causes these microbubbles to oscillate in size which changes the self-quenching efficiency of the dye molecules creating a "blinking" signal. We demonstrate for the first time that these microbubbles can reproducibly generate second, third, and even fourth harmonic fluorescence intensity modulations, in addition to the fundamental frequency of the driving ultrasound.

The behavior of lipid debris left on cell surfaces from microbubble based ultrasound molecular imaging.

Lipid monolayer coated microbubbles are currently being developed to identify vascular regions that express certain surface proteins as part of the new technique of ultrasound molecular imaging. The microbubbles are functionalized with targeting ligands which bind to the desired cells holding the microbubbles in place as the remaining unbound microbubbles are eliminated from circulation. Subsequent scanning with ultrasound can detect the highly reflectant microbubbles that are left behind.

Manipulating nanoscale features on the surface of dye-loaded microbubbles to increase their ultrasound-modulated fluorescence output.

The nanoscale surface features of lipid-coated microbubbles can dramatically affect how the lipids interact with one another as the microbubble diameter expands and contracts under the influence of ultrasound. During microbubble manufacturing, the different lipid shell species naturally partition forming concentrated lipid islands. In this study the dynamics of how these nanoscale islands accommodate the expansion of the microbubbles are monitored by measuring the fluorescence intensity changes that occur as self-quenching lipophilic dye molecules embedded in the lipid layer change their distance from one another.

Neural progenitor cells labeling with microbubble contrast agent for ultrasound imaging in vivo.

Tracking neuroprogenitor cells (NPCs) that are used to target tumors, infarction or inflammation, is paramount for cell-based therapy. We employed ultrasound imaging that can detect a single microbubble because it can distinguish its unique signal from those of surrounding tissues. NPCs efficiently internalized positively charged microbubbles allowing a clinical ultrasound system to detect a single cell at 7 MHz.

Phospholipid/Carbocyanine Dye-Shelled Microbubbles as Ultrasound-Modulated Fluorescent Contrast Agents.

Fluorescent microbubbles have been fabricated with the capacity to have their emission modulated by ultrasound. These contrast agent particles could potentially be used in the future to extract fluorescence modulation from a strong light background to increase imaging depth and resolution in scattering media. Fluorescence intensity modulation was demonstrated at the ultrasound driving frequency.

Fluorescent microscope system to monitor real-time interactions between focused ultrasound, echogenic drug delivery vehicles, and live cell membranes.

Rapid development in the field of ultrasound triggered drug delivery has made it essential to study the real-time interaction between the membranes of live cells and the membranes of echogenic delivery vehicles under exposure to focused ultrasound. The objective of this work was to design an analysis system that combined fluorescent imagining, high speed videography, and definable pulse sequences of focused ultrasound to allow for real time observations of both cell and vehicle membranes. Documenting the behavior of the membranes themselves has not previously been possible due to limitations with existing optical systems used to understand the basic physics of microbubble/ultrasound interaction and the basic interaction between microbubbles and cells.

Acoustic droplet vaporization and propulsion of perfluorocarbon-loaded microbullets for targeted tissue penetration and deformation.

[Image: see text] Acoustic droplet vaporization of perfluorocarbon-loaded microbullets triggered by an ultrasound pulse provides the necessary force to penetrate, cleave, and deform cellular tissue for potential targeted drug delivery and precision nanosurgery.

Ultrasound mediated localized drug delivery.

Chemotherapy is one of the frontline treatments for cancer patients, but the toxic side effects limit its effectiveness and potential. The goal of drug delivery is to reduce these side effects by encapsulating the drugs in a carrier which prevents release and can circulate throughout the body causing minimal damage to the healthy tissue. Slow release carriers have been developed which reduce the exposure to healthy tissue but this slow release also limits the maximum levels of drug in the tumor and nonspecific accumulation in healthy tissue remains a major hurdle.

A novel nested liposome drug delivery vehicle capable of ultrasound triggered release of its payload.

The use of focused ultrasound can be an effective method to locally highlight tumor tissue and specifically trigger the activation of echogenic drug delivery vehicles in an effort to reduce systemic chemotherapy side effects. Here we demonstrate a unique ultrasound triggered vehicle design and fabrication method where the payload and a perfluorocarbon gas microbubble are both encapsulated within the internal aqueous space of a liposome. This nested lipid shell geometry both stabilized the microbubble and ensured it was spatially close enough to interact with the liposome membrane at all times.