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A unifying fundamental element of our research will be the harnessing of anisometric interactions in soft matter to achieve new functions. We seek to use orientation-dependent interactions to modulate self-assembly, photonic properties and active transport processes. We also employ these interactions in detection mechanisms to create a range of biologically and technologically relevant soft materials. These materials include biomimetic photonic structures, biosensors and materials for guided active transport.
Liquid Liquid Crystal Phase Separation:
Liquid-liquid phase separation (LLPS) is a fundamental phenomenon observed in various branches of materials science. Recently, it has gained prominence in the field of biology, offering profound insights into genomic organization, RNA processing, mitosis, and cell adhesion. LLPS occurs when macromolecular components within a homogeneous solution demix into two distinct phases. In nature, LLPS and liquid crystalline (LC) ordering occur together. However, there is still much to uncover about synthetic counterparts that mimic these phenomena. Notably, biopolymers such as actin, nucleic acid, amyloid fibrils, microtubules, collagen, and nanocellulose has been reported to form structured liquid crystals in vitro because of a combination of molecular processes, such as crowded environment, excluded volume interactions, hydrophobic interactions, crosslinking, hydrogen bonding and increasing concentrations. We explore liquid-liquid crystalline phase separation (LLCPS), an intricate phenomenon observed in the presence of LC-forming molecule governed by intricate molecular interactions and thermodynamic forces. LLCPS manifests as the demixing of a solution into two distinct phases: a dense phase enriched with LC-forming components coexisting with a supernatant phase depleted in LC content. This phase separation can be segregative, associative, or simple associative.
The primary mechanism that drives segregative LLPS is the entropic depletion force, which arises when large particles are placed in a solution of smaller ones and sterically constrained to avoid them. These two molecules segregate into aqueous distinct two-phase systems: one phase enriched with the large molecules and the other predominantly with the smaller particles (depletants). Here, we propose that segregative LLCPS, driven by depletants, can enrich the assembly of LC-forming components into orientationally ordered structures. We can engineer the LC phase with desired morphologies and functionality by tuning depletant shapes, concentration, and size. For example, we observe a phase transition from isotropic to nematic of chromonic at nanomolar concentrations of DNA; the fundamental knowledge uncovered because of this study enables the development of real-time optical reporting of DNA amplification.
Associative phase separation, more commonly known as complex coacervation, arises due to an attractive interaction such as charge-based interactions, hydrogen bonding, hydrophobic interactions, and π-π interactions between two molecules. The basic form of LC coacervation consists of an LC-forming molecule and an oppositely charged polyelectrolyte. Here, the dense (coacervate phase) consists of the LC-forming molecule and the polyelectrolyte, while the supernatant is mostly water. The associative LLCPS offers a strategy to construct LC droplets with sensitive and unique optical properties that can be influenced by external stimuli. Understanding the associative LLCPS is essential for controlling LC droplets for various applications. For example, we observe a texture change from radial to bipolar when proteins are introduced to the LC droplets. Notably, only poly-lysine has been reported to undergo an LLCPS when associated with chromonic or DNA (LC-forming molecules), as such influential factors such like stoichiometry, molecular weights of polymers, ionic strength, and temperature must be explored.
Source of support: Arkansas Biosciences Institute
Interfacing Cells with Liquid Crystals:
It is known that changes in mechanical properties of biological cells, for instance, red blood cells (RBCs), play a profound role in physiological processes. For instance, increased stiffness of sickle cells reduce the lifespan and the ability of blood cells to flow through narrow capillaries where they commonly encounter anisometric strain. Furthermore, the stiffness of mammalian cells has been shown to be a marker of the metastatic potential of cancers. We study the deformability and relaxation of cell membranes when subjected to anisometric strain using an ordered fluid, specifically, lyotropic chromonic liquid crystals (LCLCs), as a host. LCLCs are a class of polyaromatic dyes that are soluble in water and form supramolecular semi-flexible rod-like assemblies upon solvation. The water solubility and bio-compatibility of LCLCs make them suitable for biological applications. In addition we are also interested in the phase behavior of LCLCs as a function of different counter-ions will also be explored using a combination of microscopy, rheology and scattering techniques. This will enable studies of biological membranes in the presence of specific cations that are known to influence cell membrane properties. Current efforts also involve identifying heat stress in poultry and on research pertaining to sickle cell disease.
Source of support: USDA NIFA
Instabilities at Interfaces:
This research theme is motivated by a simple table-top experiment wherein a large drop of oil is placed atop a petri-dish filled with water. We explore several means of creating surface tension-driven instabilities to break down the large oil drop into tiny droplets. This system will be used to model the cleaning up of oil spills. In particular, the role of orientational elasticity in influencing jet-breakup will be explored. In addition, the more general topic of droplet breakup in ordered fluids will be examined. Specific efforts are directed towards droplet breakup studies of lyotropic chromonic liquid crystals wherein open questions regarding the rheological behavior of these fluids (wormlike micellar solutions or rigid rods) remain to be answered.
Source of support: ACS PRF
Liquid Liquid Crystal Phase Separation:
Liquid-liquid phase separation (LLPS) is a fundamental phenomenon observed in various branches of materials science. Recently, it has gained prominence in the field of biology, offering profound insights into genomic organization, RNA processing, mitosis, and cell adhesion. LLPS occurs when macromolecular components within a homogeneous solution demix into two distinct phases. In nature, LLPS and liquid crystalline (LC) ordering occur together. However, there is still much to uncover about synthetic counterparts that mimic these phenomena. Notably, biopolymers such as actin, nucleic acid, amyloid fibrils, microtubules, collagen, and nanocellulose has been reported to form structured liquid crystals in vitro because of a combination of molecular processes, such as crowded environment, excluded volume interactions, hydrophobic interactions, crosslinking, hydrogen bonding and increasing concentrations. We explore liquid-liquid crystalline phase separation (LLCPS), an intricate phenomenon observed in the presence of LC-forming molecule governed by intricate molecular interactions and thermodynamic forces. LLCPS manifests as the demixing of a solution into two distinct phases: a dense phase enriched with LC-forming components coexisting with a supernatant phase depleted in LC content. This phase separation can be segregative, associative, or simple associative.
The primary mechanism that drives segregative LLPS is the entropic depletion force, which arises when large particles are placed in a solution of smaller ones and sterically constrained to avoid them. These two molecules segregate into aqueous distinct two-phase systems: one phase enriched with the large molecules and the other predominantly with the smaller particles (depletants). Here, we propose that segregative LLCPS, driven by depletants, can enrich the assembly of LC-forming components into orientationally ordered structures. We can engineer the LC phase with desired morphologies and functionality by tuning depletant shapes, concentration, and size. For example, we observe a phase transition from isotropic to nematic of chromonic at nanomolar concentrations of DNA; the fundamental knowledge uncovered because of this study enables the development of real-time optical reporting of DNA amplification.
Associative phase separation, more commonly known as complex coacervation, arises due to an attractive interaction such as charge-based interactions, hydrogen bonding, hydrophobic interactions, and π-π interactions between two molecules. The basic form of LC coacervation consists of an LC-forming molecule and an oppositely charged polyelectrolyte. Here, the dense (coacervate phase) consists of the LC-forming molecule and the polyelectrolyte, while the supernatant is mostly water. The associative LLCPS offers a strategy to construct LC droplets with sensitive and unique optical properties that can be influenced by external stimuli. Understanding the associative LLCPS is essential for controlling LC droplets for various applications. For example, we observe a texture change from radial to bipolar when proteins are introduced to the LC droplets. Notably, only poly-lysine has been reported to undergo an LLCPS when associated with chromonic or DNA (LC-forming molecules), as such influential factors such like stoichiometry, molecular weights of polymers, ionic strength, and temperature must be explored.
Source of support: Arkansas Biosciences Institute
Interfacing Cells with Liquid Crystals:
It is known that changes in mechanical properties of biological cells, for instance, red blood cells (RBCs), play a profound role in physiological processes. For instance, increased stiffness of sickle cells reduce the lifespan and the ability of blood cells to flow through narrow capillaries where they commonly encounter anisometric strain. Furthermore, the stiffness of mammalian cells has been shown to be a marker of the metastatic potential of cancers. We study the deformability and relaxation of cell membranes when subjected to anisometric strain using an ordered fluid, specifically, lyotropic chromonic liquid crystals (LCLCs), as a host. LCLCs are a class of polyaromatic dyes that are soluble in water and form supramolecular semi-flexible rod-like assemblies upon solvation. The water solubility and bio-compatibility of LCLCs make them suitable for biological applications. In addition we are also interested in the phase behavior of LCLCs as a function of different counter-ions will also be explored using a combination of microscopy, rheology and scattering techniques. This will enable studies of biological membranes in the presence of specific cations that are known to influence cell membrane properties. Current efforts also involve identifying heat stress in poultry and on research pertaining to sickle cell disease.
Source of support: USDA NIFA
Instabilities at Interfaces:
This research theme is motivated by a simple table-top experiment wherein a large drop of oil is placed atop a petri-dish filled with water. We explore several means of creating surface tension-driven instabilities to break down the large oil drop into tiny droplets. This system will be used to model the cleaning up of oil spills. In particular, the role of orientational elasticity in influencing jet-breakup will be explored. In addition, the more general topic of droplet breakup in ordered fluids will be examined. Specific efforts are directed towards droplet breakup studies of lyotropic chromonic liquid crystals wherein open questions regarding the rheological behavior of these fluids (wormlike micellar solutions or rigid rods) remain to be answered.
Source of support: ACS PRF
