Research
Innovation in Nanomedicine & Drug Delivery
Our mission
The need for targeted drug delivery in
acute critical illness
We focus all our technology development efforts on one very large and impactful class of diseases: acute critical illnesses (ACIs). As we explain below, these diseases provide an excellent fit with the capabilities of nanomedicine.
ACIs are those that can immediately lead to severe organ damage and loss of life. These diseases, which are taken care of in the intensive care unit (ICU), include some of the biggest killers in the US: sepsis, acute respiratory distress syndrome (ARDS; the disorder which is the main cause of death from COVID-19), heart attack, stroke, severe trauma, and many more. Unfortunately, for most of these diseases, there are few if any disease-specific drugs and the outcomes remain very poor. Thus, there is a great need to develop a new approach to drug therapy for acute critical illness.
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In developing that new approach, it is notable that these ICU diseases share 3 key pharmacological challenges that have previously impeded drug development:
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ACI patients are fragile: Once one organ is severely injured, other organs tend to fall like dominoes. The result is that ACI patients are less tolerant of drugs' off-target side effects, as several organs are already perturbed from their normal operating range.
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ACIs are complex and rapidly progressive: The underlying signaling networks for most common diseases are complex, with dozens of signaling proteins and other macromolecules interacting in a dense network. But for ACIs, the activities of each these numerous nodes change on a timescale of minutes to hours. This makes it very challenging to design a drug that will hit one of these targets at exactly the right time.
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ACIs are vascular-oriented: The microvasculature (capillaries and post-capillary venules) is at the center of the pathology of nearly all ACIs. The microvasculature serves as the gateway for toxic components of blood (e.g., complement proteins and activated leukocytes) to enter into the tissue and damage it, as seen in stroke, ARDS, sepsis, and many more ACIs. Unfortunately, drugs do not naturally concentrate in the microvasculature.
Nanomedicine as the platform for drug delivery in acute critical illness
To solve the above 3 pharmacological challenges and thereby create a platform technology for treating ACIs, the Brenner Bioengineering Lab has been developing VMLs (vascular-targeted, multi-drug-loaded lipid nanocarriers). VMLs are ~100-nanometer drug carriers, either liposomes (for loading small molecule drugs) or lipid nanoparticles (for loading in RNA cargo). When VMLs are injected intravascularly, they concentrate strongly in the target organ, using a variety of targeting mechanisms explained below. By concentrating drugs in the diseased organ, VMLs eliminate the off-target side effects of cargo drugs, solving the fragility problem above. By shuttling multiple drugs, they intervene on multiple points of pathology, addressing the problems of complexity and rapid progression. Finally, VMLs are targeted to the microvasculature of a target organ, solving the third pharmacological problem above.
Along with our collaborators, we have created a number of targeting mechanisms for VMLs so that they can target any organ affected by ACIs. The first such technology, developed in the 1990s by Dr. Brenner’s former postdoc advisor and continued close collaborator, Dr. Vlad Muzykantov, involves conjugating to VMNs’ surface affinity moieties (e.g., antibodies and derivatives thereof) that bind to endothelial cells (see our publications with PMIDs 28065731, 28304180). The second such technology we co-developed is RBC-hitchhiking (RH), in which VMLs are adsorbed onto red blood cells, which facilitates transfer to the capillary endothelium, without needing antibodies (PMID 29992966). Combined with IA (intra-arterial) catheters, RH achieved the highest published levels of delivery to organs such as the brain (for treating stroke, where RH achieved >10x the brain delivery of the best reported prior technology). Finally, more recently, we have developed nanoparticles that target the microvasculature using another distinct technique, based on their supramolecular organization of proteins (manuscript on biorXiv). Using this new technique, we can now target VMLs to marginated leukocytes (white blood cells temporarily residing inside the capillary lumen), which along with the endothelial cells are the major cell types of the microvasculature. Thus, we are getting progressively closer to our goal of being able to target any of the major cells types in any microvascular bed affected by ACIs.
We have two truly co-equal missions:
Build nanotechnologies to treat diseases
Provide a great training environment
Therefore, we focus heavily on educating our trainees in the fundamentals of bioengineering and on the hardest technical skills of our particular fields of nanomedicine and targeted drug delivery. We believe in providing our trainees with support from career lab scientists and technicians, especially helping with our multiple models of disease, so trainees can focus on learning the fundamentals of nanomedicine.
Our hope is that our trainees will therefore learn how to develop nanotechnologies for any disease, with our lab's particular diseases of interest (acute critical illnesses) serving as a convenient but impactful training ground.
If a trainee cures a disease while they're at it, then it's bonus points!
Techniques we use in our lab
Nanomedicine requires an interdisciplinary team, focused on three areas:
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Nanoengineering:
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Nanocarriers: We have utilized a large number of different nanocarriers, such as our recent manuscript employing >20 nanoparticle (NP) formats, including nanogels, protein NPs, polymer NPs, liposomes, viruses, and more. However, our major focus is on lipid nanocarriers (liposomes and lipid NPs), since these have by far the best track record of FDA-approvals. When we need NPs which we do not normally synthesize ourselves, we get help from our multiple collaborators whom we've published with.
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Nanoparticle characterization: We use the standard: DLS (Malvern Zetasizer), nanoparticle tracking analysis (NanoSight), electronmicroscopy (via Penn's EM core), etc.
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Drug-loading: We stably load drugs into liposomes, using a variety of techniques (passive loading and multiple active loading methods based on the functional groups on each molecule). For RNA loading, we've partnered with Drew Weissman and Mike Mitchell's labs at Penn.
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Protein engineering: We work with the Muzykantov lab at Penn to use protein engineering to make improved targeting moeities for nanocarriers, the simplest of which is to use scFv's instead of mAbs.
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Models of disease:
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Rodent models: ​For each disease we work on, we aim to have multiple mouse models, given that each has its own caveats and models different aspects of the disease. For example, for ARDS, we have established several mouse models: nebulized LPS, unilateral aspiration of acid or LPS, oleic acid IV, ventilator-induced lung injury, hyperoxia, and cecal slurry.
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Rodent ICU: Through our own equipment and those of collaborators, we have all the tools to measure the physiology and disease phenotypes that are used clinically in the ICU, such as pulse oximetry, blood pressure, CBC, ABG, and more.
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Nanoparticle tracing: We trace nanoparticles using radiolabeling (the most accurate quantitation available, with far better sensitivity and lower artifacts than fluorescence tracing), flow cytometry, histology, and even intravital microscopy (fluorescent confocal microscopy of nanoparticles and cells in living animals).
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Large animal models: For any new targeting technology, we believe in the importance of testing it in large animals. For example, for RBC-hitchhiking (RH), we used pigs to show that RH is not simply a.phenomenon of mice but found more widely. We do this in collaboration with labs at Penn that focus on large animal models.
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Ex vivo human organs: As a final de-risking of nanotechnology, we test it in ex vivo human organs. We started this with fresh ex vivo human lungs that were rejected from transplant due to having ARDS (our disease of interest!). We've published on this multiple times, and can get such lungs weekly.
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Patient samples: Through our collaborators in Pulmonology and Neurology, we have access to serum samples from large numbers of patients with acute critical illnesses, such as ARDS, sepsis, DIC, trauma, and ischemic stroke.
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Computational Modeling:
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PBPK modeling: We employ physiology-based pharmacokinetic modeling (PBPK) modeling to determine how nanocarriers, drugs, and even microbes distribute ​within the body. In PBPK modeling, we create a set of ordinary differential equations (ODEs) to describe the flow of blood and particle fluxes between the blood and multiple organs, using a large number of experimentally measured values to parameterize the model. We then use the model to predict how various nanocarrier properties would influence drug distribution. We have used PBPK modeling to greatly influence our design of nanocarriers for acute critical illnesses.
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Other computational techniques for nanomedicine: Collaborating with computational modeling labs at Penn, we are also investigating the tools of network pharmacology to predict optimal pairs of drugs to deliver, and molecular dynamics to understand how nanocarriers interact with serum proteins.
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