Controlling Liquid Crystal Configuration and Phase Using Multiple Molecular Triggers.

Liquid crystals are able to transform a local molecular interaction into a macroscopic change of state, making them a valuable "smart" material. Here, we investigate a novel polymeric amphiphile as a candidate for molecular triggering of liquid crystal droplets in aqueous background. Using microscopy equipped with crossed polarizers and optical tweezers, we find that the monomeric amphiphile is able to trigger both a fast phase change and then a subsequent transition from nematic to isotropic. We next include sodium dodecyl sulfate (SDS), a standard surfactant, with the novel amphiphilic molecules to test phase transitioning when both were present. As seen previously, we find that the activity of SDS at the surface can result in configuration changes with hysteresis. We find that the presence of the polymeric amphiphile reverses the hysteresis previously observed during such transitions. This work demonstrates a variety of phase and configuration changes of liquid crystals that can be controlled by multiple exogenous chemical triggers.

Core Hydrophobicity of Supramolecular Nanoparticles Induces NLRP3 Inflammasome Activation.

Designer nanomaterials capable of delivering immunomodulators to specific immune cells have been extensively studied. However, emerging evidence suggests that several of these nanomaterials can nonspecifically activate NLRP3 inflammasomes, an intracellular multiprotein complex controlling various immune cell functions, leading to undesirable effects. To understand what nanoparticle attributes activate inflammasomes, we designed a multiparametric polymer supramolecular nanoparticle system to modulate various surface and core nanoparticle-associated molecular patterns (NAMPs), one at a time. We also investigated several underlying signaling pathways, including lysosomal rupture-cathepsin B maturation and calcium flux-mitochondrial ROS production, to gain mechanistic insights into NAMPs-mediated inflammasome activation. Here, we report that out of the four NAMPs tested, core hydrophobicity strongly activates and positively correlates with the NLRP3 assembly compared to surface charge, core rigidity, and surface hydrophobicity. Moreover, we demonstrate different signaling inclinations and kinetics followed by differential core hydrophobicity patterns with the most hydrophobic ones exhibiting both lysosomal rupture and calcium influx early on. Altogether, this study will help design the next generation of polymeric nanomaterials for specific regulation of inflammasome activation, aiding efficient immunotherapy and vaccine delivery.

Toward Chemotactic Supramolecular Nanoparticles: From Autonomous Surface Motion Following Specific Chemical Gradients to Multivalency-Controlled Disassembly.

Nature designs chemotactic supramolecular structures that can selectively bind specific groups present on surfaces, autonomously scan them moving along density gradients, and react once a critical concentration is encountered. Since such properties are key in many biological functions, these also offer inspirations for designing artificial systems capable of similar bioinspired autonomous behaviors. One approach is to use soft molecular units that self-assemble in an aqueous solution generating nanoparticles (NPs) that display specific chemical groups on their surface, enabling multivalent interactions with complementarily functionalized surfaces. However, a first challenge is to explore the behavior of these assemblies at sufficiently high-resolution to gain insights on the molecular factors controlling their behaviors. Here, by coupling coarse-grained molecular models and advanced simulation approaches, we show that it is possible to study the (autonomous or driven) motion of self-assembled NPs on a receptor-grafted surface at submolecular resolution. As an example, we focus on self-assembled NPs composed of facially amphiphilic oligomers. We observe how tuning the multivalent interactions between the NP and the surface allows to control of the NP binding, its diffusion along chemical surface gradients, and ultimately, the NP reactivity at determined surface group densities. In silico experiments provide physical-chemical insights on key molecular features in the self-assembling units which determine the dynamic behavior and fate of the NPs on the surface: from adhesion, to diffusion, and disassembly. This offers a privileged point of view into the chemotactic properties of supramolecular assemblies, improving our knowledge on how to design new types of materials with bioinspired autonomous behaviors.

Optical "Blinking" Triggered by Collisions of Single Supramolecular Assemblies of Amphiphilic Molecules with Interfaces of Liquid Crystals.

We report that incubation of aqueous dispersions of supramolecular assemblies formed by synthetic alkyl triazole-based amphiphiles against interfaces of thermotropic liquid crystals (LCs; 4-cyano-4'-pentylbiphenyl) triggers spatially localized (micrometer-scale) and transient (subsecond) flashes of light to be transmitted through the LC. Analysis of the spatiotemporal response of the LC supports our proposal that each optical "blinking" event results from collision of a single supramolecular assembly with the LC interface. Particle tracking at the LC interface confirmed that collision and subsequent spreading of amphiphiles at the interface generates a surface pressure-driven interfacial flow (Marangoni flow) that causes transient reorientation of LC and generation of a bright optical flash between crossed polarizers. We also found that dispersions of phospholipid vesicles cause "blinks". When using vesicles formed from 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), we measured the frequency of blinking to decrease proportionally with the number density of vesicles in the aqueous phase, consistent with single vesicle events, with the lifetime of each blink dependent on vesicle size (800 ± 80 nm to 150 ± 30 nm). For 100 µM of DLPC, we measured vesicles with a diameter of 940 ± 290 nm to generate 47 ± 9 blinks min-1 mm-2, revealing that the fraction of vesicle collisions resulting in fusion with the LC interface is ∼10-3. Overall, the results in this paper unmask new nonequilibrium behaviors of amphiphiles at LC interfaces, and provide fresh approaches for exploring the dynamic interactions of supramolecular assemblies of amphiphiles with fluid interfaces at the single-event level.

Polymer with Competing Depolymerization Pathways: Chain Unzipping versus Chain Scission.

Interest in triggered depolymerization is growing, driven by needs in sustainable plastics, self-healing materials, controlled release, and sensory amplification. For many triggered depolymerization reactions, the rate-limiting step does not directly involve the stimulus, and therefore, depolymerization kinetics exhibit only weak or no correlation to the concentration and reactivity of the stimulus. However, for many applications, a direct relationship between the stimulus and the depolymerization kinetics is desired. Here we designed, synthesized, and studied a polymer in which a nucleophile-induced chain scission (NICS) mechanism competes with the chain unzipping pathway. We find that the choice of the chain end functionality and the character of the nucleophile determines which of these is the predominant pathway. The NICS pathway was found to be dependent on the stimulus concentration, in contrast to the chain unzipping mechanism. We demonstrate transferability of these molecular-scale, structure-property relationships to nanoscale materials by formulating the polymers into host nanoparticles.