By adjusting the chemical structure of lipid nanoparticles (LNPs), Penn Engineers have discovered how to target specific organs, a major breakthrough in precision medicine. (Love Employee via Getty Images)
Penn Engineers have discovered a novel means of directing lipid nanoparticles (LNPs), the revolutionary molecules that delivered the COVID-19 vaccines, to target specific tissues, presaging a new era in personalized medicine and gene therapy.
While past research — including at Penn Engineering — has screened “libraries” of LNPs to find specific variants that target organs like the lungs, this approach is akin to trial and error. “We’ve never understood how the structure of one key component of the LNP, the ionizable lipid, determines the ultimate destination of LNPs to organs beyond the liver,” says Michael J. Mitchell, Associate Professor in Bioengineering.
In a new paper published in Nature Nanotechnology, Mitchell’s group describes how subtle adjustments to the chemical structure of the ionizable lipid, a key component of the LNP, allows for tissue-specific delivery, in particular to the liver, lungs and spleen.
In a collaborative interdisciplinary study, Michael Mitchell of the School of Engineering and Applied Science, Wei Guo of the School of Arts & Sciences, and Drew Weissman of the Perelman School of Medicine show that solid tumors can block drug-delivery mechanisms with a “forcefield-like” effect but certain genetic elements that can effectively “shut down” the forcefield. Their findings hint at new targets for delivering cancer treatments that use the body’s immune system to fight tumors. (Image: iStock / CIPhotos)
The tumor microenvironment—an ad hoc, messy amalgamation of signaling molecules, immune cells, fibroblasts, blood vessels, and the extracellular matrix—acts like a “powerful security system that protects solid tumors from invaders seeking to destroy them,” says Michael Mitchell, a bioengineer at the University of Pennsylvania working on nanoscale therapeutics aimed at targeting cancers.
“A lot like the Death Star with its surrounding fleet of fighter ships and protective shields, solid tumors can use features like immune cells and vasculature to exert force, acting as a physical barrier to rebel forces (nanoparticles) coming in to deliver the payload that destroys it,” Mitchell says.
Now, researchers in the Mitchell lab have teamed up with Wei Guo’s group in the School of Arts & Sciences at Penn and Drew Weissman of the Perelman School of Medicine to figure out the molecular mechanisms that make tumor microenvironments seemingly impenetrable and found that small extracellular vesicles (sEVs) are secreted by tumor cells and act as a “forcefield,” blocking therapeutics. Their findings are published in Nature Materials.
“This discovery reveals how tumors create a robust defense system, making it challenging for nanoparticle-based therapies to reach and effectively target cancer cells,” Guo says. “By understanding the cellular mechanisms driving these responses, we can potentially develop strategies to disable this defense, allowing therapeutics to penetrate and attack the tumor more efficiently.”
The research builds on a prior collaboration between Guo and Mitchell’s labs, wherein the teams focused on how tumor-associated immune cells, known as macrophages, contribute to the suppression of anti-tumor immunity by secreting extracellular vesicles.
Wei Guo is the Hirsch Family President’s Distinguished Professor in the Department of Biology in Penn’s School of Arts & Sciences.
Ningqiang Gong, a former postdoctoral researcher in the Mitchell lab at Penn Engineering, is an assistant professor at the University of Science and Technology of China.
Wenqun Zhong is a reseearch associate in the Guo Laboratory in Penn Arts & Sciences.
Other authors include: Alex G Hamilton, Dongyoon Kim, Junchao Xu, and Lulu Xue of Penn Engineering; Junhyong Kim, Zhiyuan Qin, and Fengyuan Xu of Penn Arts & Sciences; Mohamad-Gabriel Alameh and Drew Weissman of the Perelman School of Medicine; Andrew E. Vaughn and Gan Zhao of the Penn School of Veterinary Medicine; Jinghong Li and Xucong Teng of the University of Beijing; and Xing-Jie Liang of the Chinese Academy of Sciences.
This research received support from the U.S. National Institutes of Health (DP2 TR002776, R35 GM141832, and NCI P50 CA261608), Burroughs Wellcome Fund, U.S. National Science Foundation CAREER Award (CBET-2145491), and an American Cancer Society Research Scholar Grant (RGS-22-1122-01-ET.)
Lipid nanoparticles present one of the most advanced drug delivery platforms to shuttle promising therapeutics such as mRNA but are limited by the time it takes to synthesize cationic lipids, a key component. Now, Michael Mitchell and his team at the School of Engineering and Applied Science have developed a faster way to make cationic lipids that are also more versatile, able to carry different kinds of treatments to target specific organs. (Image: iStock / Dr_Microbe)
Imagine a scenario where a skilled hacker must upload critical software to update a central server and thwart a potentially lethal virus from wreaking havoc across a vast computer network. The programmer, armed with the lifesaving code, must navigate through treacherous territory teeming with adversaries, and success hinges on promptly getting a safe, stealthy delivery vehicle that can place the hacker exactly where they need to be.
In the context of modern medicine, messenger RNA (mRNA) serves as the hacker, carrying genetic instructions to produce specific proteins within cells that can induce desired immune responses or sequester maladaptive cellular elements. Lipid nanoparticles (LNPs) are the stealthy delivery vehicles that transport these fragile mRNA molecules through the bloodstream to their target cells, overcoming the body’s defenses to deliver their payload safely and efficiently.
However, much like building an advanced stealth vehicle, the synthesis of cationic lipids—a type of lipid molecule that’s positively charged and a key component of LNPs—is often a time-consuming process, involving multiple steps of chemical synthesis and purification.
Now, Michael Mitchell and a team at the University of Pennsylvania have addressed this challenge with a novel approach that leverages a compound library fabrication technique known as “click-like chemistry” to create LNPs in a single, simple step. Their findings, published in the journal Nature Chemistry, show that this method not only speeds up the synthesis process but also presents a way to equip these delivery vehicles with a “GPS” to better target specific organs such as the liver, lungs, and spleen, potentially opening new avenues for treating a range of diseases that arise in these organs.
“We’ve developed what we call an amidine-incorporated degradable (AID) lipid, a uniquely structured biodegradable molecule,” Mitchell says. “Think of it as an easy-to-build custom mRNA vehicle with a body kit that informs its navigation system. By adjusting its shape and degradability, we can enhance mRNA delivery into cells in a safe manner. By adjusting the amount of the AID lipid that we incorporate into the LNP, we can also guide it to different organs in the body, much like programming different destinations into a GPS.”
First author Xuexiang Han, a former postdoctoral researcher in the Mitchell Lab, explains that their new approach allows the rapid creation of diverse lipid structures in just an hour, compared to the weekslong process traditionally required.
Visualization of a CAR T cell (in red) attacking a cancer cell (in blue) (Meletios Varras via Getty Images)
For patients with certain types of cancer, CAR T cell therapy has been nothing short of life changing. Developed in part by Carl June, Richard W. Vague Professor at Penn Medicine, and approved by the Food and Drug Administration (FDA) in 2017, CAR T cell therapy mobilizes patients’ own immune systems to fight lymphoma and leukemia, among other cancers.
However, the process for manufacturing CAR T cells themselves is time-consuming and costly, requiring multiple steps across days. The state of the art involves extracting patients’ T cells, then activating them with tiny magnetic beads, before giving the T cells genetic instructions to make chimeric antigen receptors (CARs), the specialized receptors that help T cells eliminate cancer cells.
Now, Penn Engineers have developed a novel method for manufacturing CAR T cells, one that takes just 24 hours and requires only one step, thanks to the use of lipid nanoparticles (LNPs), the potent delivery vehicles that played a critical role in the Moderna and Pfizer-BioNTech COVID-19 vaccines.
In a new paper in Advanced Materials, Michael J. Mitchell, Associate Professor in Bioengineering, describes the creation of “activating lipid nanoparticles” (aLNPs), which can activate T cells and deliver the genetic instructions for CARs in a single step, greatly simplifying the CAR T cell manufacturing process. “We wanted to combine these two extremely promising areas of research,” says Ann Metzloff, a doctoral student in Bioengineering and NSF Graduate Research Fellow in the Mitchell lab and the paper’s lead author. “How could we apply lipid nanoparticles to CAR T cell therapy?”
Penn Engineers have developed a way to target lung diseases, including lung cancer, with lipid nanoparticles (LNPs). (wildpixel via Getty Images)
Penn Engineers have developed a new means of targeting the lungs with lipid nanoparticles (LNPs), the miniscule capsules used by the Moderna and Pfizer-BioNTech COVID-19 vaccines to deliver mRNA, opening the door to novel treatments for pulmonary diseases like cystic fibrosis.
In a paper in Nature Communications, Michael J. Mitchell, Associate Professor in the Department of Bioengineering, demonstrates a new method for efficiently determining which LNPs are likely to bind to the lungs, rather than the liver. “The way the liver is designed,” says Mitchell, “LNPs tend to filter into hepatic cells, and struggle to arrive anywhere else. Being able to target the lungs is potentially life-changing for someone with lung cancer or cystic fibrosis.”
Previous studies have shown that cationic lipids — lipids that are positively charged — are more likely to successfully deliver their contents to lung tissue. “However, the commercial cationic lipids are usually highly positively charged and toxic,” says Lulu Xue, a postdoctoral fellow in the Mitchell Lab and the paper’s first author. Since cell membranes are negatively charged, lipids with too strong a positive charge can literally rip apart target cells.
Typically, it would require hundreds of mice to individually test the members of a “library” of LNPs — chemical variants with different structures and properties — to find one with a low charge that has a higher likelihood of delivering a medicinal payload to the lungs.
Instead, Xue, Mitchell and their collaborators used what is known as “barcoded DNA” (b-DNA) to tag each LNP with a unique strand of genetic material, so that they could inject a pool of LNPs into just a handful of animal models. Then, once the LNPs had propagated to different organs, the b-DNA could be scanned, like an item at the supermarket, to determine which LNPs wound up in the lungs.
Four University of Pennsylvania undergraduates have received 2024 Goldwater Scholarships, awarded to second- or third-year students planning research careers in mathematics, the natural sciences, or engineering.
They are among the 438 students named 2024 Goldwater Scholars from 1,353 undergraduates students nominated by 446 academic institutions in the United States, according to the Barry Goldwater Scholarship & Excellence in Education Foundation. Each scholarship provides as much as $7,500 each year for as many as two years of undergraduate study.
Mrksich, from Hinsdale, Illinois, is majoring in bioengineering. She is interested in developing drug delivery systems that can serve as novel therapeutics for a variety of diseases. Mrksich works in the lab of Michael J. Mitchell where she investigates the ionizable lipid component of lipid nanoparticles for mRNA delivery. At Penn, Mrksich is the president of the Biomedical Engineering Society, where she plans community building and professional development events for bioengineering majors. She is a member of the Kite and Key Society, where she organizes virtual programming to introduce prospective students to Penn. She is a member of Tau Beta Pi engineering honor society, and the Sigma Kappa sorority. She also teaches chemistry to high schoolers as a volunteer in the West Philadelphia Tutoring Project through the Civic House. After graduating, Mrksich plans to pursue an M.D./Ph.D. in bioengineering.
Mrksich was awarded a Student Award for Outstanding Research (Undergraduate) by the Society for Biomaterials earlier this year. Read the story in the BE Blog.
Like space shuttles using booster rockets to breach the atmosphere, lipid nanoparticles (LNPs) equipped with the new molecule more successfully deliver medicinal payloads. (Love Employee via Getty Images)
Inspired by the design of space shuttles, Penn Engineering researchers have invented a new way to synthesize a key component of lipid nanoparticles (LNPs), the revolutionary delivery vehicle for mRNA treatments including the Pfizer-BioNTech and Moderna COVID-19 vaccines, simplifying the manufacture of LNPs while boosting their efficacy at delivering mRNA to cells for medicinal purposes.
In a paper in Nature Communications, Michael J. Mitchell, Associate Professor in the Department of Bioengineering, describes a new way to synthesize ionizable lipidoids, key chemical components of LNPs that help protect and deliver medicinal payloads. For this paper, Mitchell and his co-authors tested delivery of an mRNA drug for treating obesity and gene-editing tools for treating genetic disease.
Previous experiments have shown that lipidoids with branched tails perform better at delivering mRNA to cells, but the methods for creating these molecules are time- and cost-intensive. “We offer a novel construction strategy for rapid and cost-efficient synthesis of these lipidoids,” says Xuexiang Han, a postdoctoral student in the Mitchell Lab and the paper’s co-first author.
In the human body, the lungs and their vasculature can be likened to a building with an intricate plumbing system. The lungs’ blood vessels are the pipes essential for transporting blood and nutrients for oxygen delivery and carbon dioxide removal. Much like how pipes can get rusty or clogged, disrupting normal water flow, damage from respiratory viruses, like SARS-CoV-2 or influenza, can interfere with this “plumbing system.”
In a recent study, researchers looked at the critical role of vascular endothelial cells in lung repair. Their work, published in Science Translational Medicine, was led by Andrew Vaughan of the University of Pennsylvania’s School of Veterinary Medicine and shows that, by using techniques that deliver vascular endothelial growth factor alpha (VEGFA) via lipid nanoparticles (LNPs), that they were able to greatly enhance modes of repair for these damaged blood vessels, much like how plumbers patch sections of broken pipes and add new ones.
“While our lab and others have previously shown that endothelial cells are among the unsung heroes in repairing the lungs after viral infections like the flu, this tells us more about the story and sheds light on the molecular mechanisms at play,” says Vaughan, assistant professor of biomedical sciences at Penn Vet. “Here we’ve identified and isolated pathways involved in repairing this tissue, delivered mRNA to endothelial cells, and consequently observed enhanced recovery of the damaged tissue. These findings hint at a more efficient way to promote lung recovery after diseases like COVID-19.”
They found VEGFA’s involvement in this recovery, while building on work in which they used single cell RNA sequencing to identify transforming growth factor beta receptor 2 (TGFBR2) as a major signaling pathway. The researchers saw that when TGFBR2 was missing it stopped the activation of VEGFA. This lack of signal made the blood vessel cells less able to multiply and renew themselves, which is vital for the exchange of oxygen and carbon dioxide in the tiny air sacs of the lungs.
“We’d known there was a link between these two pathways, but this motivated us to see if delivering VEGFA mRNA into endothelial cells could improve lung recovery after disease-related injury,” says first author Gan Zhao, a postdoctoral researcher in the Vaughan Lab.
“LNPs have been great for vaccine delivery and have proven incredibly effective delivery vehicles for genetic information. But the challenge here was to get the LNPs into the bloodstream without them heading to the liver, which is where they tend to congregate as its porous structure lends favor to substances passing from the blood into hepatic cells for filtration,” says Mitchell, an associate professor of bioengineering at Penn Engineering and a coauthor of the paper. “So, we had to devise a way to specifically target the endothelial cells in the lungs.”
Lulu Xue, a postdoctoral researcher in the Mitchell Lab and a co-first author of the paper, explains that they engineered the LNP to have an affinity for lung endothelial cells, this is known as extra hepatic delivery, going beyond the liver.
From left: Emily Han, Rohan Palanki, Jacqueline Li, Michael Mitchell, Dongyoon Kim, and Marshall Padilla of Penn Engineering.
Imagine the brain as an air traffic control tower, overseeing the crucial and complex operations of the body’s ‘airport.’ This tower, essential for coordinating the ceaseless flow of neurological signals, is guarded by a formidable layer that functions like the airport’s security team, diligently screening everything and everyone, ensuring no unwanted intruders disrupt the vital workings inside.
However, this security, while vital, comes with a significant drawback: sometimes, a ‘mechanic’—in the form of critical medication needed for treating neurological disorders—is needed inside the control tower to fix arising issues. But if the security is too stringent, denying even these essential agents entry, the very operations they’re meant to protect could be jeopardized.
Now, researchers led by Michael Mitchell of the University of Pennsylvania are broaching this long-standing boundary in biology, known as the blood-brain barrier, by developing a method akin to providing this mechanic with a special keycard to bypass security. Their findings, published in the journal Nano Letters, present a model that uses lipid nanoparticles (LNPs) to deliver mRNA, offering new hope for treating conditions like Alzheimer’s disease and seizures—not unlike fixing the control tower’s glitches without compromising its security.
“Our model performed better at crossing the blood-brain barrier than others and helped us identify organ-specific particles that we later validated in future models,” says Mitchell, associate professor of bioengineering at Penn’s School of Engineering and Applied Science, and senior author on the study. “It’s an exciting proof of concept that will no doubt inform novel approaches to treating conditions like traumatic brain injury, stroke, and Alzheimer’s.”
Kaitlin Mrksich, an undergraduate student in Penn Bioengineering, was honored with the Student Award for Outstanding Research (Undergraduate) by the Society for Biomaterials (SFB). This prestigious award recognizes undergraduate students who have shown outstanding achievement in biomaterials research.
Mrksich is a third-year student from Hinsdale, Illinois. She is interested in developing drug delivery systems that can serve as novel therapeutics for a variety of diseases. She works in the lab of Michael Mitchell, Associate Professor in Bioengineering. In the Mitchell Lab, Mrksich investigates the ionizable lipid component of lipid nanoparticles for mRNA delivery.
“In Kaitlin’s independent projects, she has focused on probing the role of lipophilicity and chirality for LNP-mediated mRNA delivery,” Mitchell said in the award announcement. “She has synthesized dozens of unique lipids, formulated these lipids into LNPs, and evaluated their potential for mRNA delivery in vivo and in primary T cells. She has been able to deduce structure-function relationships that help explain the role of lipid hydrophobicity in the delivery of mRNA by LNPs. Her findings have not only been instrumental in helping our lab design better LNPs but will also provide fundamental knowledge that will benefit all labs working on LNP technology.”
In addition to her academic activities, Mrksich is also the President of the Penn Biomedical Engineering Society (BMES), where she plans community-building and professional-development events for bioengineering majors, and the visit coordinator for special programs for the Kite and Key Society, where she organizes virtual programming to introduce prospective students to Penn. She also tutors a West Philadelphia high school student in chemistry as part of the West Philadelphia Tutoring Project and is a member of Tau Beta Pi engineering honor society and Sigma Kappa sorority. After graduating, she plans to pursue an M.D.-Ph.D. in Bioengineering.
Read the full list of 2024 SFB award recipients here.
