Kacper Lachowski

Bio: Kacper Lachowski is an academic researcher from University of Washington. The author has contributed to research in topics: Medicine & Chemistry. The author has co-authored 1 publications.

Predictive Theoretical Framework for Dynamic Control of Bioinspired Hybrid Nanoparticle Self-Assembly.

Abstract: At-will tailoring of the formation and reconfiguration of hierarchical structures is a key goal of modern nanomaterial design. Bioinspired systems comprising biomacromolecules and inorganic nanoparticles have potential for new functional material structures. Yet, consequential challenges remain because we lack a detailed understanding of the temporal and spatial interplay between participants when it is mediated by fundamental physicochemical interactions over a wide range of scales. Motivated by a system in which silica nanoparticles are reversibly and repeatedly assembled using a homobifunctional solid-binding protein and single-unit pH changes under near-neutral solution conditions, we develop a theoretical framework where interactions at the molecular and macroscopic scales are rigorously coupled based on colloidal theory and atomistic molecular dynamics simulations. We integrate these interactions into a predictive coarse-grained model that captures the pH-dependent reversibility and accurately matches small-angle X-ray scattering experiments at collective scales. The framework lays a foundation to connect microscopic details with the macroscopic behavior of complex bioinspired material systems and to control their behavior through an understanding of both equilibrium and nonequilibrium characteristics.

Dual-Stimuli Responsive Single-Chain Polymer Folding via Intrachain Complexation of Tetramethoxyazobenzene and β-Cyclodextrin.

Abstract: We synthesize and characterize a triblock polymer with asymmetric tetramethoxyazobenzene (TMAB) and β-cyclodextrin functionalization, taking advantage of the well-characterized azobenzene derivative-cyclodextrin inclusion complex to promote photoresponsive, self-contained folding of the polymer in an aqueous system. We use 1H NMR to show the reversibility of (E)-to-(Z) and (Z)-to-(E) TMAB photoisomerization, and evaluate the thermal stability of (Z)-TMAB and the comparatively rapid acid-catalyzed thermal (Z)-to-(E) isomerization. Important for its potential use as a functional material, we show the photoisomerization cyclability of the polymeric TMAB chromophore and calculate isomerization quantum yields by extinction spectroscopy. To verify self-inclusion of the polymeric TMAB and cyclodextrin, we use two-dimensional 1H NOESY NMR data to show proximity of TMAB and cyclodextrin in the (E)-state only; however, (Z)-TMAB is not locally correlated with cyclodextrin. Finally, the observed decrease in photoisomerization quantum yield for the dual-functionalized polymer compared to the isolated chromophore in an aqueous solution confirms TMAB and β-cyclodextrin not only are in proximity to one another, but also form the inclusion complex.

Multivariate Analysis of Peptide-Driven Nucleation and Growth of Au Nanoparticles

Abstract: In this work we synthesize gold nanostructures using a liquid-handling robot and present new data analysis methods to quantitatively compare the effect of peptides and peptide modifications on gold nanoparticle synthesis outcomes. The peptides used were gold binding peptides Z2 and AG3, as well as five Z2 variants obtained by sequence modification or conjugation of a lipid tail. Four different concentrations of peptide, reducing agent (HEPES), and precursor (\ce{HAuCl4}) were used to synthesize 64 different reagent combinations for each of the seven peptides. Each sample was characterized using UV-Vis spectroscopy, which serves as a proxy for changes in nanoparticle structure, and enabled comparisons of how peptide modifications and reagent conditions affect synthesis outcomes. We then used functional data analysis to extract a pairwise signal correlation distance between each of the peptides. The signal correlation distance quantified how different the set of 64 spectra, and therefore the synthesis outcomes, was from one peptide to the other. We show that substitution of methionine for isoleucine in Z2 has a profound impact on synthesis outcomes when compared with conjugation of a lipid tail. Electron microscopy and ultra-small angle X-ray scattering were used to corroborate our conclusions from spectroscopy experiments by directly characterizing the structure of a smaller set of samples. Scanning electron microscopy revealed interconnected plate-like structures in samples prepared with a Z2 variant with all methionines substituted by isoleucine. Z2 peptides modified with a lipid tail on the other hand, formed nanoparticles which were more colloidally stable than those prepared with non-lipidated peptides, contained no plate-like particles, and whose size depended on the ratio of peptide to precursor.

Multi-Step Nucleation of A Crystalline Silicate Framework via A Structurally Precise Prenucleation Cluster.

Abstract: Hierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of open framework lattices such as zeolites and metal-organic frameworks, pre-organized multi-ion "secondary building units" (SBUs) have long been proposed as fundamental building blocks of the forming crystals. However, detailing the progress of multi-step reaction mechanisms in going from monomeric species to stable crystals and defining the structures of the intermediate SBUs remains an unmet challenge. Combining in situ nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy, we show that crystallization of the framework silicate, cyclosilicate hydrate, occurs through an assembly of cubic octameric Q38 polyanions formed through cross-linking and polymerization of smaller silicate monomers and other oligomers. These Q38 are stabilized by hydrogen bonds with surrounding H2O and tetramethylammonium ions (TMA+). When Q38 levels reach a threshold of ~32% of the total silicate species nucleation within these clathrates occurs. Further growth proceeds through the incorporation of [(TMA)x(Q38)·nH2O](x-8) clathrate complexes into step edges on the crystals. These findings provide a clear picture of the multi-step nucleation process by which SBUs build a framework silicate lattice with implications for the synthesis of both functional materials and natural minerals.

Hierarchical Materials from High Information Content Macromolecular Building Blocks: Construction, Dynamic Interventions, and Prediction.

Abstract: Hierarchical materials that exhibit order over multiple length scales are ubiquitous in nature. Because hierarchy gives rise to unique properties and functions, many have sought inspiration from nature when designing and fabricating hierarchical matter. More and more, however, nature's own high-information content building blocks, proteins, peptides, and peptidomimetics, are being coopted to build hierarchy because the information that determines structure, function, and interfacial interactions can be readily encoded in these versatile macromolecules. Here, we take stock of recent progress in the rational design and characterization of hierarchical materials produced from high-information content blocks with a focus on stimuli-responsive and "smart" architectures. We also review advances in the use of computational simulations and data-driven predictions to shed light on how the side chain chemistry and conformational flexibility of macromolecular blocks drive the emergence of order and the acquisition of hierarchy and also on how ionic, solvent, and surface effects influence the outcomes of assembly. Continued progress in the above areas will ultimately usher in an era where an understanding of designed interactions, surface effects, and solution conditions can be harnessed to achieve predictive materials synthesis across scale and drive emergent phenomena in the self-assembly and reconfiguration of high-information content building blocks.

Hierarchical Materials from High Information Content Macromolecular Building Blocks: Construction, Dynamic Interventions, and Prediction.

Abstract: Hierarchical materials that exhibit order over multiple length scales are ubiquitous in nature. Because hierarchy gives rise to unique properties and functions, many have sought inspiration from nature when designing and fabricating hierarchical matter. More and more, however, nature's own high-information content building blocks, proteins, peptides, and peptidomimetics, are being coopted to build hierarchy because the information that determines structure, function, and interfacial interactions can be readily encoded in these versatile macromolecules. Here, we take stock of recent progress in the rational design and characterization of hierarchical materials produced from high-information content blocks with a focus on stimuli-responsive and "smart" architectures. We also review advances in the use of computational simulations and data-driven predictions to shed light on how the side chain chemistry and conformational flexibility of macromolecular blocks drive the emergence of order and the acquisition of hierarchy and also on how ionic, solvent, and surface effects influence the outcomes of assembly. Continued progress in the above areas will ultimately usher in an era where an understanding of designed interactions, surface effects, and solution conditions can be harnessed to achieve predictive materials synthesis across scale and drive emergent phenomena in the self-assembly and reconfiguration of high-information content building blocks.

pH-Triggered Transition from Micellar Aggregation to a Host-Guest Complex Accompanied by a Color Change.

Abstract: A pH-triggered transition from micellar aggregation to a host-guest complex was achieved based on the supramolecular interactions between calixpyridinium and pyrroloquinoline quinone disodium salt (PQQ-2Na) accompanied by a color change. Our design has the following three advantages: (1) a regular spherical micellar assembly is fabricated by the supramolecular interactions between calixpyridinium and PQQ-2Na at pH 6 in an aqueous solution, (2) increasing the pH can lead to a transition from micellar aggregation to a host-guest complex due to the deprotonation of calixpyridinium, and at the same time (3) increasing the pH can lead to a color change owing to the deprotonation of calixpyridinium and the complexation of deprotonated calixpyridinium with PQQ-2Na. Benefitting from the low toxicity of calixpyridinium and PQQ-2Na, this pH-induced transition from micellar aggregation to a host-guest complex was further studied as a controllable-release model.

A hybrid approach for coarse-graining helical peptoids: Solvation, secondary structure, and assembly.

Abstract: Protein mimics such as peptoids form self-assembled nanostructures whose shape and function are governed by the side chain chemistry and secondary structure. Experiments have shown that a peptoid sequence with a helical secondary structure assembles into microspheres that are stable under various conditions. The conformation and organization of the peptoids within the assemblies remains unknown and is elucidated in this study via a hybrid, bottom-up coarse-graining approach. The resultant coarse-grained (CG) model preserves the chemical and structural details that are critical for capturing the secondary structure of the peptoid. The CG model accurately captures the overall conformation and solvation of the peptoids in an aqueous solution. Furthermore, the model resolves the assembly of multiple peptoids into a hemispherical aggregate that is in qualitative agreement with the corresponding results from experiments. The mildly hydrophilic peptoid residues are placed along the curved interface of the aggregate. The composition of the residues on the exterior of the aggregate is determined by two conformations adopted by the peptoid chains. Hence, the CG model simultaneously captures sequence-specific features and the assembly of a large number of peptoids. This multiscale, multiresolution coarse-graining approach could help in predicting the organization and packing of other tunable oligomeric sequences of relevance to biomedicine and electronics.