We have developed a general synthetic route to encapsulate small molecules in monodisperse zeolitic imid-azolate framework-8 (ZIF-8) nanospheres for drug delivery. Electron microscopy, powder X-ray diffraction, and elemental analysis show that the small-molecule-encapsulated ZIF-8 nanospheres are uniform 70 nm particles with single-crystalline structure. Several small molecules, including fluorescein and the anticancer drug camptothecin, were encapsulated inside of the ZIF-8 framework. Evaluation of fluorescein-encapsulated ZIF-8 nanospheres in the MCF-7 breast cancer cell line demonstrated cell internalization and minimal cytotoxicity. The 70 nm particle size facilitates cellular uptake, and the pH-responsive dissociation of the ZIF-8 framework likely results in endosomal release of the small-molecule cargo, thereby rendering the ZIF-8 scaffold an ideal drug delivery vehicle. To confirm this, we demonstrate that camptothecin encapsulated ZIF-8 particles show enhanced cell death, indicative of internalization and intracellular release of the drug. To demonstrate the versatility of this ZIF-8 system, iron oxide nanoparticles were also encapsulated into the ZIF-8 nanospheres, thereby endowing magnetic features to these nanospheres.

Transforming natural cells into functional biocompatible robots capable of active movement is expected to enhance the functions of the cells and revolutionize the development of synthetic micromotors. However, present cell-based micromotor systems commonly require the propulsion capabilities of rigid motors, external fields, or harsh conditions, which may compromise biocompatibility and require complex actuation equipment. Here, we report on an endogenous enzyme-powered Janus platelet micromotor (JPL-motor) system prepared by immobilizing urease asymmetrically onto the surface of natural platelet cells. This Janus distribution of urease on platelet cells enables uneven decomposition of urea in biofluids to generate enhanced chemophoretic motion. The cell surface engineering with urease has negligible impact on the functional surface proteins of platelets, and hence, the resulting JPL-motors preserve the intrinsic biofunctionalities of platelets, including effective targeting of cancer cells and bacteria. The efficient propulsion of JPL-motors in the presence of the urea fuel greatly enhances their binding efficiency with these biological targets and improves their therapeutic efficacy when loaded with model anticancer or antibiotic drugs. Overall, asymmetric enzyme immobilization on the platelet surface leads to a biogenic microrobotic system capable of autonomous movement using biological fuel. The ability to impart self-propulsion onto biological cells, such as platelets, and to load these cellular robots with a variety of functional components holds considerable promise for developing multifunctional cell-based micromotors for a variety of biomedical applications.

Small interfering RNA (siRNA) is a powerful tool for gene silencing that has been used for a wide range of biomedical applications, but there are many challenges facing its therapeutic use in vivo. Here, we report on a platelet cell membrane-coated metal-organic framework (MOF) nanodelivery platform for the targeted delivery of siRNA in vivo. The MOF core is capable of high loading yields, and its pH sensitivity enables endosomal disruption upon cellular uptake. The cell membrane coating provides a natural means of biointerfacing with disease substrates. It is shown that high silencing efficiency can be achieved in vitro against multiple target genes. Using a murine xenograft model, significant antitumor targeting and therapeutic efficacy are observed. Overall, the biomimetic nanodelivery system presented here provides an effective means of achieving gene silencing in vivo and could be used to expand the applicability of siRNA across a range of disease-relevant applications.

Composite nanomaterials are attractive for a diverse range of applications in catalysis, plasmonics, sensing, imaging, and biology. In such composite nanomaterials, it is desired, yet still challenging to create a controlled alignment between components with lattices in disparate scales. To address this challenge, we report a new concept of colloidal synthesis, in which self-assembled molecular layers control the alignment between materials during the synthesis. To illustrate this concept, self-assembled cetyltrimethylammonium bromide (CTAB) molecules are used to control interfaces in a core-shell nanocomposite with a well-defined metal nanocrystal core and a metal-organic-framework (MOF) shell, which differ in structural dimensions by orders of magnitude. We show that single metal nanocrystals are captured individually in single-crystalline MOFs, and an alignment between the {100} planes of the metal and {110} planes of the MOFs is observed. By utilizing the same concept, a layer of mesostructured silica is formed over MOF crystals. These multilayered core-shell structures demonstrate a controlled alignment across a wide range of materials, from the metal nanocrystals, extending to nanoporous MOFs and mesostructured silica.

The effect of lattice strain on the catalytic properties of Pd nanoparticles is systematically studied. Synthetic strategies for the preparation of a series of shape-controlled Pd nanocrystals with lattice strain generated from different sources has been developed. All of these nanocrystals were created with the same capping agent under similar reaction conditions. First, a series of Pd nanoparticles was synthesized that were enclosed in {111} surfaces: Single-crystalline Pd octahedra, single-crystalline AuPd core-shell octahedra, and twinned Pd icosahedra. Next, various {100}-terminated particles were synthesized: Single-crystalline Pd cubes and single-crystalline AuPd core-shell cubes. Different extents of lattice strain were evident by comparing the X-ray diffraction patterns of these particles. During electrocatalysis, decreased potentials for CO stripping and increased current densities for formic-acid oxidation were observed for the strained nanoparticles. In the gas-phase hydrogenation of ethylene, the activities of the strained nanoparticles were lower than those of the single-crystalline Pd nanoparticles, perhaps owing to a larger amount of cetyl trimethylammonium bromide on the surface.

Anti‐adhesion therapies interfere with the bacterial adhesion to the host and thus avoid direct disruption of bacterial cycles for killing, which may alleviate resistance development. Herein, an anti‐adhesion nanomedicine platform is made by wrapping synthetic polymeric cores with bacterial outer membranes. The resulting bacterium‐mimicking nanoparticles (denoted “OM‐NPs”) compete with source bacteria for binding to the host. The “top‐down” fabrication of OM‐NPs avoids the identification of the adhesins and bypasses the design of agonists targeting these adhesins. In this study, OM‐NPs are made with the membrane of Helicobacter pylori and shown to bind with gastric epithelial cells (AGS cells). Treatment of AGS cells with OM‐NPs reduces H. pylori adhesion and such anti‐adhesion efficacy is dependent on OM‐NP concentration and its dosing sequence.

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The efforts of detecting bioactive targets with complex, dynamic, and unknown molecular profiles have inspired the development of various biosensor platforms. Herein, we report a cell-membrane-modified field effect transistor (FET) as a function-based nanosensor for the detection and quantitative measurement of numerous toxins and biological samples. By coating carbon nanotube FETs with natural red blood cell membranes, the resulting biomimetic nanosensor can selectively interact with and absorb broad-spectrum hemolytic toxins regardless of their molecular structures. Toxin–biomembrane interactions alter the local charge distribution at the FET surface in an ultrasensitive and concentration-dependent manner, resulting in a detection limit down to the femtomolar (fM) range. Accurate and quantitative measurements are enabled via a built-in calibration mechanism of the sensor, which overcomes batch-to-batch fabrication variations, and are demonstrated using three distinct toxins and various complex bacterial supernatants. The measured signals of bacterium-secreted proteins correlate linearly with the actual bacterial numbers, making the biosensor a nontraditional approach to rapidly detecting bacterial concentrations without a need to count bacterial colonies.