Programming of Supercrystals Using Replicable DNA-Functionalized Colloids.

The development of self-replicating systems is of great importance in research on the origin of life. As the most iconic molecules, nucleic acids have provided prominent examples of the fabrication of self-replicating artificial nanostructures. However, it is still challenging to construct sophisticated synthetic systems that can create large-scale or three-dimensionally ordered nanomaterials using self-replicating nanostructures. By integrating a template system containing DNA-functionalized colloidal seeds with a simplified DNA strand-displacement circuit programmed subsystem to produce DNA-functionalized colloidal copies, we developed a facile enthalpy-mediated strategy to control the replication and catalytic assembly of DNA-functionalized colloids in a time-dependent manner. The replication efficiency and crystal quality of the resulting superlattice structures can be effectively increased by regulating the molar ratio of the template to the copy colloids. By constructing binary systems from two types of gold nanoparticles (or proteins), superlattice structures with different crystal symmetries can be obtained through the replication and catalytic assembly processes. This programmable enthalpy-mediated approach was easily leveraged to achieve the phase transformation and catalytic amplification of colloidal crystals starting from different initial template crystals. This work offers a potential way to construct self-replicating artificial systems that exhibit complicated phase behaviors and can produce large-scale superlattice nanomaterials.

A Biomimetic Cardiac Fibrosis-on-a-Chip as a Visible Disease Model for Evaluating Mesenchymal Stem Cell-Derived Exosome Therapy.

Cardiac fibrosis acts as a serious worldwide health issue due to its prevalence in numerous forms of cardiac disease and its essential link to cardiac failure. Considering the efficiency of stem cell therapy for cardiac fibrosis, great efforts have been dedicated to developing accurate models for investigating their underlying therapeutic mechanisms. Herein we present an elaborate biomimetic cardiac fibrosis-on-a-chip based on Janus structural color film (SCF) to provide microphysiological visuals for stem cell therapeutic studies. By coculturing cardiomyocytes (CMs) and cardiac fibroblasts (FBs) on Janus SCF with fibrosis induction, the chip can recreate physiological intercellular crosstalk within the fibrotic microenvironment, elucidating the physiological alterations of fibrotic hearts. In particular, the Janus structural color film possesses superior perceptual capabilities for capturing and responding to a weak cardiac force, demonstrating synchronized structural color shifts. Based on these features, we have not only explored the dynamic relationship between color mapping and the evaluated disease phenotype but also demonstrated the self-reporting capacity of the cardiac fibrosis-on-a-chip for the assessment of mesenchymal stem cell-derived exosome therapy. These features suggest that such a chip can potentially facilitate the evolution of precision medicine strategies and create a protocol for preclinical cardiac drug screening.

Modeling order-disorder boundaries of colloidal dispersions in organic solvents using interaction force measurements.

HYPOTHESIS: The formation of soft colloidal crystals, which are nonclose-packed ordered arrays of colloidal particles suspended in a solvent, is dictated by a single physical factor that yields a fixed threshold at order-disorder boundaries for different experimental conditions such as ion concentration, solvent type, and particle size. Identifying the determinant factor and its threshold value should enable the prediction of the critical concentrations of colloidal particles to form soft colloidal crystals. EXPERIMENTS: Soft colloidal crystals were fabricated using a series of monohydric alcohols as dispersion media and reflectance spectra were measured to locate order-disorder boundaries. The interaction forces acting between particles were also measured by employing atomic force microscopy. FINDINGS: The interparticle forces at the order-disorder boundaries exhibited a universal threshold that was independent of the solvent types including alcohols and water. Therefore, the determinant factor for the formation of soft colloidal crystals was determined to be the force acting between the particles. Furthermore, a priori calculation of this critical force and consequently the critical particle concentration in colloidal systems was demonstrated by referring to the pressure at the liquid-to-solid transition in a hard sphere system (Alder transition).

Real-time tracking of the adsorption of bovine serum albumin on lipid layer and its effect on lipolysis by optical interferometry.

The model proteins bovine serum albumin (BSA) and lipid layer were used to study the effect of proteins on lipolysis. A lipid layer with an interference effect was constructed by loading the triolein into the silica colloidal crystal (SCC) film. The ordered porous layer interferometry (OPLI) system was used to track the changes in lipid layer mass caused by lipase hydrolysis to achieve real-time lipolysis detection. The real-time tracking of the adsorption of BSA on the lipid layer by converting the migration of interference fringes caused by the change of the lipid layer into the optical thickness change (ΔOT). The effect of BSA on the early and late stages of lipolysis was studied, and lipases containing 5 mg/mL BSA degraded the lipid layer 3.4 times faster than lipases containing 0.1 mg/mL BSA in the later stages. This study deepens the understanding of protein-lipid interactions in complex digestive environments.

Nanocrystal Assemblies: Current Advances and Open Problems.

We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.