We demonstrate a method to create highdensity DNA coatings on colloidal particles that can be used for DNA-mediated self-assembly of single-and multiplecomponent colloidal crystals. First, we modify an amphiphilic diblock copolymer consisting of a hydrophobic polystyrene (PS) block and a hydrophilic poly(ethylene oxide) (PEO) block with azide functional groups at the end (poly(ethylene oxide)-N 3 ). Then, we introduce the diblock copolymers into an aqueous suspension of colloidal polymer particles swollen with a solvent. The hydrophobic PS anchoring block is incorporated into the swollen polymer spheres and physically trapped when the solvent is removed, resulting in a dense PEO polymer brush with azide functional end groups. Finally, singlestranded DNA strands with sticky ends are attached to the azide groups using strain-promoted azide−alkyne cycloaddition (SPAAC, a copper-free click chemistry). This procedure results in a high areal coverage of up to 225 000 DNA strands on 1-μmdiameter particles. The ssDNA-coated particles with sticky ends can readily form either face-centered-cubic (fcc) or cesium chloride (CsCl) crystal structures when annealed just below the melting temperature of the DNA-coated particles.

Lactic acid bacteria (LAB) are the common probiotics. Here, we investigated the antiviral protective effects of heat-killed LAB strain Lactobacillus casei DK128 (DK128) on influenza viruses. Intranasal treatment of mice with DK128 conferred protection against different subtypes of influenza viruses by lessening weight loss and lowering viral loads. Protection via heat-killed DK128 was correlated with an increase in alveolar macrophage cells in the lungs and airways, early induction of virus specific antibodies, reduced levels of pro-inflammatory cytokines and innate immune cells. Importantly, the mice that were protected against primary viral infection as a result of heat-killed DK128 pretreatment developed subsequent heterosubtypic immunity against secondary virus infection. For protection against influenza virus via heat-killed DK128 pretreatment, B cells and partially CD4 T cells but not CD8 T cells were required as inferred from studies using knockout mouse models. Our study provides insight into how hosts can be equipped with innate and adaptive immunity via heat-killed DK128 treatment to protect against influenza virus, supporting that heat-killed LAB may be developed as anti-virus probiotics.

Janus colloids with one attractive patch on an otherwise repulsive particle surface serve as model systems to explore structure formation of particles with chemically heterogeneous surfaces such as proteins. While there are numerous computer studies, there are few experimental realizations due to a lack of means to produce such colloids with a well-controlled variable Janus balance. Here, we report a simple scalable method to precisely vary the Janus balance over a wide range and selectively functionalize one patch with DNA. We observe, via experiment and simulation, the dynamic formation of diverse superstructures: colloidal micelles, chains, or bilayers, depending on the Janus balance. Flexible dimer chains form through cooperative polymerization while trimer chains form by a two-stage process, first by cooperative polymerization into disordered aggregates followed by condensation into more ordered stiff trimer chains. Introducing substrate binding through depletion catalyzes dimer chains to form nonequilibrium rings that otherwise do not form.

A simple yet versatile solution-based process to produce colloidal silica hexapods is developed in which various shapes of silica rods are grown on the faces of cubes in a controlled manner. In the presence of hematite cubic particles, water droplets nucleate on the surface of hematite by phase separation in pentanol. By adjusting the water concentration, six droplets can form on each face of the hematite cube. A silica precursor is then administered into the system, which gradually diffuses into the water droplets through the oil phase. Within the droplets, hydrolysis and condensation of the precursors take place, leading to formation of silica rods. As a result, silica hexapods on a magnetic hematite cubic seed are produced. Furthermore, when the emulsions are aged at 60 °C prior to the silica growth, the water content in the solution decreases gradually due to evaporation and spiky sharp hexapods are produced. On the other hand, when organosilane precursor is added, pancake-like hexapods are formed due to the reduction of interfacial tension. These colloidal hexapods can further be utilized as new building blocks for self-assembly to construct functional materials or as a model system to understand collective behaviors.

Patchy particles with shape complementarity can serve as building blocks for assembling colloidal superstructures. Alternatively, encoding information on patches using DNA can direct assembly into a variety of crystalline or other preprogrammed structures. Here, we present a tool where DNA is used both to engineer shape and to encode information on colloidal particles. Two reactive oil emulsions with different but complementary DNA (cDNA) brushes are assembled into CsCl-like crystalline lattices. The DNA brushes are recruited to and ultimately localized at the junctions between neighboring droplets, which gives rise to DNA-encoded faceted patches. The emulsions are then solidified by ultraviolet (UV) polymerization, producing faceted patchy particles. The facet size and DNA distribution are determined by the balance between the DNA binding energy and the elastic deformation energy of droplets. This method leads to a variety of new patchy particles with directional interactions in scalable quantities.