Research

The broad aim of this laboratory is to characterize key structural properties and interactions among biomolecular soft matter (lipids, polymers, peptides, proteins and their complexes) to elucidate their function in nature as well as to develop therapeutic and biotechnological materials. A current focus of our work is to understand how the structural complexity of lipids and bio-membranes in living systems is implicated in certain diseases and how that knowledge can inform the design of better gene and drug delivery systems. Below we highlight a few specific ongoing research projects:

I. Smart supramolecular structures for the transport of biomolecules (proteins, siRNA, mRNA, and DNA) in cells: Lipids are the building blocks of the bilayer structure present in cellular membranes. Even though lipids are held together by

Figure I. A microfluidics platform produces cuboplex LNPs that deliver siRNA to cells.

non-covalent interactions, the plasma membrane construct is a highly specific and efficient barrier and transferring biomolecules from outside to inside cells is a fascinating materials science challenge. We focus on lipid materials that are highly biocompatible and favorably interact with the plasma membrane. The most recent demonstration of the power of lipid materials is the development of the COVID-19 mRNA vaccines. In the Leal lab we focus our research on developing and characterizing lipid nanoparticles (LNPs) with exotic structures that have preferential interactions with cell membranes and deliver biomolecules and drugs effectively. We are particularly interested in the basic science behind this process and understanding the physical effects of LNP nanostructure on nucleic acid delivery. (NIH-funded, publication example: L. Zheng, S. Bandara, Z. Tan, and C. Leal*, "Lipid nanoparticle topology regulates endosomal escape and delivery of RNA to the cytoplasm." Proc. Natl. Acad. Sci. USA. 120, 27, e2301067120 (2023))

II. Polymer-lipid hybrid membranes: Polymers have rich chemical diversity while lipids are biocompatible, have preferential interactions with cells, and have highly dynamic phase transformations. We are investigating a new class of

Figure II. Confocal microscopy image of a multilamellar giant vesicle comprising polymer and lipid domains. Scale bar is 10 mm.

hybrid systems, one can say soft matter alloys, where lipids and polymers co-assemble into a hybrid nanostructure. We are interested in the synergistic phase behavior that emerges during the process of polymer-lipid hybridization. The properties of these hybrid materials can be harnessed to design: i) new drug delivery systems for the oral delivery of highly hydrophobic drugs, ii) thermally actuated membranes, and iii) ion/water synthetic porin systems, among others. (NSF-funded, publication example: Y. K. Go, J. Shin, G. Chen, and C. Leal*, "Reorientation of Crystalline Block Copolymer Membranes by Phospholipid Hybridization." Chem. Mater. 34, 19, 8577–8592 (2022))

III. Characterization of the structural evolution of lipid droplet organelles as a function of diet: We are developing scattering, optical, and electron

Figure III. Confocal microscopy of LDs isolated from adipose tissue.

microscopy-based methods to understand how lipid droplet organelles (LDs) store fats in adipocytes during the the onset of obesity and how the process is regulated by diet. A related project evalulates the morphological alterations of LDs isolated from hepatocytes during the progression of hepatocellular carcinoma. We do this work in collaboration with Sayee Anakk (Cancer Center at Illinois and NIH-funded, publication example: K. Ko, S. R. Bandara, W. Zhou, L. Svenningsson, M. Porras-Gómez, N. Kambar, J. Dreher-Threlkeld, D. Topgaard, D. Hernàndez-Saavedra, S. Anakk*, C. Leal*, "Diet-Induced Obesity Modulates Close-Packing of Triacylglycerols in Lipid Droplets of Adipose Tissue," J. Am. Chem. Soc. 146, 34796-34810 (2024)).

IV: Characterization of biomolecular materials structures by Cryo-EM: We are developing electron microscopy-based methods to analyze and quantitatively characterize the structural properties of biomolecular and living systems such as LNPs for gene and drug delivery, extracellular vesicals, organelles, and membranouse microorganisms such as bacteria and viruses. (NIH- and MURI/ARO-funded).

V. Phase behavior of lung soft materials:

Figure V. Illustration of a gas sensor developed to detect oxygen permeation through lung membranes.

We are underpinning the role of phase behavior, morphology, and gas transport properties of pulmonary membranes in lungs afflicted with respiratory diseases. We investigate materials extracted from lungs as well as rationally designed model systems to determine the specific role of structure and lipid composition using a battery of techniques such as AFM, Fluorescence Microscopy, Small Angle X-ray Scattering (ONR-funded, publication example: M. Kim, M. Porras-Gómez, and C. Leal*, "Graphene-based sensing of oxygen transport through pulmonary membranes" Nat. Commun. 11, 1-10 (2020))

VI. Fundamental processes of polymers and lipid self-assembly:

Figure VIa. A giant unilamellar vesicle displays enhanced fluctuations when including "non-lamellar lipids". Video by Edin Li (Schroeder's group).

We investigate the intermolecular interactions enabling the rich phase behavior of certain lipid and polymer classes. We are particularly interested in lipid membrane biophysical properties such as packing and elasticity as affected by the addition of active proteins and/or lipids that do not traditionally assemble in flat bilayers.

Figure VIb. 2D X-ray diffraction of a super-swelled lipid 3D bicontinuous cubic phase.

We are also exploring the basic principles leading to the formation of soft material phases that assemble into highly ordered non-lamellar crystal-like structures. Specifically, we are underpinning the physical properties that lead to super-swelling of highly ordered bicontinuous cubic phases as well as multilamellar systems. (ONR-, NSF-, and NIH-funded, publication example: H. Kim, Z. Song, and C. Leal*, "Super-swelled Lyotropic Single Crystals" Proc Natl Acad Sci USA 114, 10834-10839 (2017)).

Funding

Many thanks to our main sources of funding: National Institutes of Health (NIH), National Science Foundation (NSF), Office of Naval Research (ONR), the American Chemical Society, Petroleum Research Fund (ACS-PRF), Army Research Office (ARO-MURI).

Collaborators

Our most active collaborators presently are: Sayee Anakk, Chris Evans, Charles Schroeder, Rosa Espinosa Marzal, Daniel Topgaard, Hua Wang, Paul Braun, David Cahill, Nancy Sottos among others!