DNA-Directed Assembly of Hierarchical MOF-Cellulose Nanofiber Microbioreactors with "Branch-Fruit" Structures

Assembling metal-organic frameworks (MOFs) into ordered multidimensional porous superstructures promises the encapsulation of enzymes for heterogeneous biocatalysts. However, the full potential of this approach has been limited by the poor stability of enzymes and the uncontrolled assembly of MOF nanoparticles onto suitable supports. In this study, a novel and exceptionally robust Ni-imidazole-based MOF was synthesized in water at room temperature, enabling in situ enzyme encapsulation. Based on this MOF platform, we developed a DNA-directed assembly strategy to achieve the uniform placement of MOF nanoparticles onto bacterial cellulose nanofibers, resulting in a distinctive "branch-fruit" structure. The resulting hybrid materials demonstrated remarkable versatility across various catalytic systems, accommodating natural enzymes, nanoenzymes, and multienzyme cascades, thus showcasing enormous potential as universal microbioreactors. Furthermore, the hierarchical composites facilitated rapid diffusion of the bulky substrate while maintaining the enzyme stability, with ∼3.5-fold higher relative activity compared to the traditional enzyme@MOF immobilized in bacterial cellulose nanofibers.

DNA-Directed Assembly of a Cell-Responsive Biohybrid Interface for Cargo Release

The development of a DNA-based cell-responsive biohybrid interface that can be used for spatially confined release of molecular cargo is reported. To this end, tailored DNA-protein conjugates are designed as gatekeepers that can be specifically cleaved by matrix metalloproteases (MMPs), which are secreted by many cancer cells. These gatekeepers can be installed by DNA hybridization on the surface of mesoporous silica nanoparticles (MSNs). The MSNs display another orthogonal DNA oligonucleotide that can be exploited for site-selective immobilization on solid glass surfaces to yield micropatterned substrates for cell adhesion. Using the human fibrosarcoma cell line HT1080 that secretes MMPs, it is demonstrated that the biohybrid surface is specifically modified by the cells to release both MSN-bound gatekeeper proteins and the encapsulated cargo peptide KLA. In view of the enormously high modularity of the system presented here, this approach promising for applications in drug delivery, tissue engineering, or other areas of nanobiotechnology is considered.

Super-Resolution Optical Lithography with DNA

We developed an efficient, versatile, and accessible super-resolution microscopy method to construct a nanoparticle assembly at a spatial resolution below the optical diffraction limit. The method utilizes DNA and a photoactivated DNA cross-linker. Super-resolution optical techniques have been used only as a means to make measurements below the light diffraction limit. Furthermore, no optical technique is currently available to construct nanoparticle assemblies with a precisely designed shape and internal structure at a resolution of a few tens of nanometers (nm). Here we demonstrate that we can fulfill this deficiency by utilizing spontaneous structural dynamics of DNA hairpins combined with single-molecule fluorescence resonance energy transfer (smFRET) microscopy and a photoactivated DNA cross-linker. The stochastic fluorescence blinking due to the spontaneous folding and unfolding motions of DNA hairpins enables us to precisely localize a folded hairpin and solidify it only when it is within a predesigned target area whose size is below the diffraction limit. As the method is based on an optical microscope and an easily clickable DNA cross-linking reagent, it will provide an efficient means to create large nanoparticle assemblies with a shape and internal structure at an optical super-resolution, opening a wide window of opportunities toward investigating their photophysical and optoelectronic properties and developing novel devices.