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Specific NanoImmunotherapy for Treating Atherosclerotic Plaque

Key Points

• Atherosclerosis is the build up of fatty plaque in the blood vessels that can result in blockage leading to heart attacks and strokes. It is also the primary contributor to heart disease, which is the #1 cause of death globally with 17.9 million lives lost each year. 
• An unnerving fact – more than half of all first heart attacks occur in people who are healthy with no known obvious risks. 
• The T-NIE lab is currently conducting world-changing research and developing innovative solutions to eliminate this problem.
• The cells within the plaque have a “do not destroy” signal (CD47 receptor) attached to them which prevents the removal of dead/dying cells. The team developed a highly-selective single-walled carbon nanotube (SWNT) to block the CD47 signal and stimulate removal of the dead cells.

Overview

Atherosclerosis (fatty plaque in the blood vessels) is the leading cause of mortality in the world. 

Dr. Smith and his team determined that the plaque via SHP1 being phosphorylated to pSHP1 was sending out a “do not destroy” signal (CD47 receptor) that prevented immune cells called macrophages from doing their job of cleaning up the apoptotic (dead) cells – a process called efferocytosis. However, because CD47 is up-regulated in atherosclerotic plaque cores, strategies to block the “do not destroy” signal can stimulate the removal of dead cells and help prevent the progression of plaque buildup. Past therapies have been costly and have resulted in undesirable side effects.

The team developed an intracellular phagocytosis-stimulating treatment in the CD47-SIRPα pathway using single-walled carbon nanotubes (SWNTs) coated with a TPI (tyrosine phosphatase inhibitor 1) molecule (see Figures A and B below). This inhibitor is released in a pH-dependent manner to inhibit/reduce the phosphorylation of SHP1. This reduction effectively blocks the CD47 signal which allows the body’s immune system to stimulate macrophage removal of the dead plaque cells.  The results have been very promising in animal trials, showing a significant reduction in plaque and blood vessel inflammation with no harmful side effects.

Learn More

• PDF article (Free) – Pro-efferocytic Nanoparticles are Specifically Taken up by Lesional Macrophages and Prevent Atherosclerosis
• Full Article (Charge) – Pro-efferocytic Nanoparticles are Specifically Taken up by Lesional Macrophages and Prevent Atherosclerosis

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Imaging of Inflamed Atherosclerotic Plaque

Key Points

• Abundant immune cells in the arterial wall, especially inflammatory monocytes and foamy macrophages, help initiate and drive plaque development and inflammation, and are likely associated with plaque vulnerability.
• Simple anatomic imaging of atherosclerotic plaque is insufficient, as the vast majority of adults have lesions, but only a subset of these go on to cause a heart attack/stroke or other cardiovascular diseases.
• We developed an ultra-selective nanoparticle targeting inflammatory monocytes and foamy macrophages and combined that with a unique modality, photoacoustic imaging (PAI), to precisely and specifically image inflamed plaque.
• Ultra-selective uptake into almost solely the inflammatory monocytes/macrophages results in the accumulation of large amounts of nanoparticles (single-walled nanotubes (SWNTs)) within the atherosclerotic plaque, but not within healthy arteries.
• This new imaging method may provide a targeted, noninvasive imaging strategy to accurately identify and diagnose cardiovascular disease.

Overview

Vascular inflammation, in which circulating inflammatory monocytes (Ly-6C^hi inflammatory monocytes in mice) infiltrate the arterial wall and differentiate into foamy macrophages plays a key role in the forming of fatty plaque in arteries. The number of monocyte/macrophage cells approximately scale with plaque severity and contribute to plaque destabilization. Therefore, their presence in a given vascular region is a major indicator for the presence of an inflamed plaque that may be vulnerable to disruption leading to heart attack or stroke.

Other imaging methods such as MRI and PET scans are not highly selective in imaging foamy macrophages and their precursor inflammatory monocytes. If contrast is used, it is relatively indiscriminately taken up by a broad spectrum of phagocytic cells. This can decrease diagnostic accuracy and specificity. These imaging methods are also associated with relatively poor resolution that cannot easily resolve early atherosclerotic plaques.

We developed an ultra-selective nanoparticle targeting inflammatory monocytes and foamy macrophages and combined it with photoacoustic imaging (PAI) to precisely and specifically image inflamed plaque.

In the new method, single-walled carbon nanotubes (SWNTs) are injected intravenously into mice. We quantitatively showed that the circulating inflammatory monocytes in mice took up these SWNTs ultra-selectively, with nearly 100% uptake into inflammatory monocytes, and nearly no uptake by any other peripheral blood cells, including patrolling monocytes, granulocytes, and lymphocytes. 

Learn More

• PDF Article (Free) – Ultraselective Carbon Nanotubes for Photoacoustic Imaging of Inflammed Atherosclerotic Plaques
• Full Article (Charge) – Ultraselective Carbon Nanotubes for Photoacoustic Imaging of Inflamed Atherosclerotic Plaques

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Nanoparticles for Drug Delivery to Relieve Tumor Immunosuppression

Key Points

• Myeloid-derived suppressor cells (MDSCs) in tumors prevent the appropriate immune system response and allow the tumor to thrive.
• Current treatments to change MDSC behavior have harmful side effects, including altering other immune cell sub-populations and non-immune cell types that reduce therapeutic efficacy.
• We developed a novel, targeted nanoparticle system that achieves high myeloid uptake in mixed primary immune cells. The nanoparticles successfully infiltrate the 4T1 triple-negative breast tumor microenvironment in mice.
• The system could provide insight into the prognostic outlook of cancer patients, provide a platform to deliver drugs to selectively modify MDSC behavior, and reduce cancer progression and patient mortality.

Overview

Metabolic-reprogramming drugs are loaded into nanoparticles to target the breast cancer tumor environment in mice that contain myeloid-derived suppressor cells (MDSCs). MDSCs strongly suppress the function of CD8+ T-cells and natural killer (NK) T-cells involved in tumor progression.

Current treatments to modify myeloid cell behavior also alter other immune cell sub-populations and non-immune cell types with harmful side effects, often resulting in tumor rebound. Therefore, improved selectivity of myeloid treatment is an urgent need.

To meet this need, the team developed a system comprising the following elements: (1) granulocyte-colony stimulation factor (G-CSF) as a targeting ligand to promote accumulation in myeloid cells including MDSCs, (2) albumin nanoparticles  (100-120 nm in diameter) that maintain their form and allow a drug payload in simulated physiological conditions, and (3) a fluorophore that enables nanoparticle tracking and models a therapeutic molecule.

The team demonstrated that this system achieves high myeloid uptake in mixed primary immune cells, that the nanoparticles successfully infiltrated the 4T1 tripe-negative breast tumor microenvironment in mice, and these cells can be imaged and tracked by imaging.

Measuring the localization, population size, and/or movement of the myeloid cells in the tumor microenvironment via this approach could provide insight into the prognostic outlook of cancer patients. Ongoing work will provide a platform to deliver myeloid-reprogramming drugs to modify MDSC behavior and reduce cancer progression and patient mortality, particularly in combination with immuno- and chemotherapeutic drugs.

Learn More

• PDF Article (Free) – Nanoparticles Decorated with Granulocyte-Colony Stimulating Factor for Targeting Myeloid Cells
• Full Article (Charge) – Nanoparticles Decorated with Granulocyte-Colony Stimulating Factor for Targeting Myeloid Cells

Nanoparticles (arrows) in Myeloid Cells (Purple = Nucleus, Red = Cell Membrane, Green = Dyed Nanoparticles)

Fluorescence Imaging of 4T1 Breast Cancer-Bearing Mice (see explanation of three mouse images below)

• Images shown 15 minutes after 10 microgram injection
  • Left mouse image – ICG (dye) alone
  • Middle mouse image – blank nanoparticles
  • Right mouse image – G-CSF nanoparticles (containing ICG dye) – observed localization in breast tumor

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Quantitative Drug Release Monitoring by Magnetic Particle Imaging (MPI)

Key Points

• Invented a new process using MPI to monitor chemotherapy concentrations.
• Created a nanocomposite consisting of super-paramagnetic nanoparticle with Doxorubicin (DOX).
• The composite serves as both a drug delivery system as well as an MPI tracer for effective imaging of tissue.
• Process is noninvasive and could help doctors adjust dosage amounts on the fly.

Overview

The team invented a new way to monitor chemotherapy concentrations. This method is more effective in keeping patients’ treatments within the crucial therapeutic window as described below.

• If dosage too high = can kill healthy tissue and trigger more side effects. 
• If dosage too low = may stun, rather than kill the cancer cells. This can allow them to come back even stronger and deadlier.

The process is based on a new imaging technology called magnetic particle imaging (MPI) that employs super-paramagnetic nanoparticles as the contrast agent and the sole signal source to monitor drug release in the body – at the site of the tumor. 

Smith’s team, which included scientists from Stanford University, created a nanocomposite by pairing its nanoparticles with Doxorubicin (DOX), a commonly used chemotherapy drug. The results in a mice study showed that this combination served as a drug delivery system as well as an MPI tracer. As the nanocomposite degrades, it begins to release DOX in the tumor. Simultaneously, as the iron oxide  (Fe₃O₄) nanoparticle/nanocluster begins to disassemble, it triggers the MPI signal changes.

The process is noninvasive and could give doctors an immediate quantitative visualization of how the drug is being distributed anywhere in the body.  With MPI, doctors in the future could see how much drug is going directly to the tumor and then adjust amounts given on the fly. Conversely, if toxicity is a concern, it can provide a view of the liver, spleen or kidneys to minimize side effects.

Learn More

• PDF Article (Free) – Quantitative Drug Release Monitoring in Tumors of Living Subjects by Magnetic Particle Imaging Nanocomposite
• Full Article (Charge) – Quantitative Drug Release Monitoring in Tumors of Living Subjects by Magnetic Particle Imaging Nanocomposite

 

TEM (Transmission electron microscopy) image of a SPNCD core−shell nanocomposite clustered inside the PLGA nanoparticle at 100 nanometers (nm)

Figure 1: Correlation curve between DOX release percentage and MPI signal intensity in cells.

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Cellular Nanomechanics

Key Points

• New nanoparticle-based imaging technique that, for the first time, can examine cell mechanical properties in living subjects.
• The mechanical properties of tissues play a major role in many well-known diseases such as heart disease and cancer.
• Nanoparticles inside living cells revealed important structural information, including how tumor cells physically change as they form a tumor.
• Discovered that normal cells’ pliability (softness) remained steady over time, but cancer cells stiffened.

Overview

The team developed an innovative nanoparticle-based imaging technique that, for the first time, can examine cell mechanical properties in living subjects. This technique promises to open entirely new avenues of inquiry for both disease diagnosis and treatment.

The mechanical properties of biological tissues have been known to play a major role in many disease states, including heart disease, inflammation and cancer, as well as normal physiology such as cell migration and organism development.

Once the nanoparticles are inside living cells, they can reveal important information about cell structure – including how tumor cells physically change as they form a tumor. Analyzing how the particles move within the cell can reveal a lot about its internal physical properties.

In a mouse study, the team observed the movement of the nanoparticles within the cells and were able to measure how pliable (soft) the cells were. Importantly, the team found that normal cells’ pliability remained steady over time, but as cancer cells formed a tumor they stiffened. 

Multiple technologies are now being combined to carefully study the role of cell mechanical properties in metastatic invasion – that is, the ability of cancer to spread throughout the body.

Learn More

• PDF Article (Free) – Particle Tracking Microheology of Cancer Cells in Living Subjects
• Full Article (Charge) – Particle Tracking Microheology of Cancer Cells in Living Subjects

Figure A: In a live mouse, EGFP (enhanced green fluorescent protein)-labeled breast cancer cells (left image) and four representative nanoparticles (right image) were tracked for 20 seconds at a high-frame rate. Note that the scale bar of 20 microns (um) applies to both images, which are the same field-of-view with separated color channels.

Figure B: Unadulterated trajectories of each tracked nanoparticle over 20 seconds, which are color-coded from blue to read, indicating elapsed time. Note the different scale bar of 500 nm. Trajectories include a combination of intrinsic intracellular Brownian motion plus the slight movements of the live mouse.

Figure C: MSDs were computed from the tracked trajectories of these four nanoparticles. Large oscillations are readily apparent in all MSDs, likely because of the rhythmic motion induced by the mouse. In this project, we developed a method to remove much of the noise due to mouse motion, enabling quantification of the physical properties of cells in living subjects.