Non-mechanical nano- and microscale pumps that function without the aid of an external power source and provide precise control over the flow rate in response to specific signals are needed for the development of new autonomous nano- and microscale systems. Here we show that surface-immobilized enzymes that are independent of adenosine triphosphate function as self-powered micropumps in the presence of their respective substrates. In the four cases studied (catalase, lipase, urease and glucose oxidase), the flow is driven by a gradient in fluid density generated by the enzymatic reaction. The pumping velocity increases with increasing substrate concentration and reaction rate. These rechargeable pumps can be triggered by the presence of specific analytes, which enables the design of enzyme-based devices that act both as sensor and pump. Finally, we show proof-of-concept enzyme-powered devices that autonomously deliver small molecules and proteins in response to specific chemical stimuli, including the release of insulin in response to glucose.

Self-propelled nano/micromotors and pumps are considered to be next generation drug delivery systems since the carriers can either propel themselves ("motor"-based drug delivery) or be delivered ("pump"-based drug delivery) to the target in response to specific biomarkers. Recently, there has been significant advancement towards developing nano/microtransporters into proof-of-concept tools for biomedical applications. This review encompasses the progress made to date on the design of synthetic nano/micromotors and pumps with respect to transportation and delivery of cargo at specific locations. Looking ahead, it is possible to imagine a day when intelligent machines navigate through the human body and perform challenging tasks.

DNA polymerase is responsible for synthesizing DNA, a key component in the running of biological machinery. Using fluorescence correlation spectroscopy, we demonstrate that the diffusive movement of a molecular complex of DNA template and DNA polymerase enhances during nucleotide incorporation into the growing DNA template. The diffusion coefficient of the complex also shows a strong dependence on its inorganic cofactor, Mg2+ ions. When exposed to gradients of either nucleotide or cofactor concentrations, an ensemble of DNA polymerase complex molecules shows collective movement toward regions of higher concentrations. By immobilizing the molecular complex on a patterned gold surface, we demonstrate the fabrication of DNA polymerase-powered fluid pumps. These miniature pumps are capable of transporting fluid and tracer particles in a directional manner with the pumping speed increasing in the presence of the cofactor. The role of DNA polymerase as a micropump opens up avenues for designing miniature fluid pumps using enzymes as engines.

In order to test the proposal that most nucleotide polymerases share a common active site structure and folding topology, we have generated 22 mutations of residues within motifs A, B and C of T7 RNA polymerase (RNAP). Characterization of these T7 RNAP mutants showed the following: (i) most of the mutations resulted in moderate to drastic reductions in T7 RNAP transcriptional activity supporting the idea that motifs A, B and C identify part of the polymerase active site; (ii) the degree of conservation of an amino acid within these motifs correlated with the degree to which mutation of that amino acid reduced transcriptional activity, supporting the predictive ability of this alignment in identifying the most functionally critical residues; (iii) a comparison of DNAP I and T7 RNAP mutants revealed similarities (as well as differences) between corresponding mutant phenotypes; (iv) the Klenow fragment structure is shown to provide a reasonable basis for interpretation of the differential effects of mutating different amino acids within motifs A, B and C in T7 RNAP. These observations support the proposal that these polymerase active sites have similar three‐dimensional structures.

Chemical composition and shape determine the basic properties of any object. Commonly, chemical synthesis and shaping follow each other in a sequence, although their combination into a single process would be an elegant simplification. Here, a pathway of simultaneous synthesis and shaping as applied to polysiloxanes on the micro- and nanoscale is presented. Complex structures such as stars, chalices, helices, volcanoes, rods, or combinations thereof are obtained. Varying the shape-controlling reaction parameters including temperature, water saturation, and the type of substrate allows to direct the reaction toward specific structures. A general mechanism of growth is suggested and analytical evidence and thermodynamic calculations to support it are provided. An aqueous droplet in either gaseous atmosphere or in a liquid organic solvent serves as a spatially confined polymerization volume. By substituting the starting materials, germanium-based nanostructures are also obtained. This transferability marks this approach as a major step toward a generally applicable method of chemical synthesis including in situ shaping.

In an effort to reduce the flammability of polyurethane foam, a thin film of renewable inorganic nanoparticles (i.e., anionic vermiculite [VMT] and cationic boehmite [BMT]) was deposited on polyurethane foam via layer-by-layer (LbL) assembly. One, two, and three bilayers (BL) of BMT-VMT resulted in foam with retained shape after being exposed to a butane flame for 10 s, while uncoated foam was completely consumed. Cone calorimetry confirmed that the coated foam exhibited a 55% reduction in peak heat release rate with only a single bilayer deposited. Moreover, this protective nanocoating reduced total smoke release by 50% relative to untreated foam. This study revealed that 1 BL, adding just 4.5 wt % to PU foam, is an effective and conformal flame retardant coating. These results demonstrate one of the most efficient and renewable nanocoatings prepared using LbL assembly, taking this technology another step closer to commercial viability.

Microporous capsules (MCs) such as polymerosomes [1,2] feature attractive properties for potential applications in materials development, optics, electronics, and delivery. [3,4] Colloidosomes are a related class of MCs whose shells consists of densely packed colloidal particles. These systems feature useful attributes including enhanced mechanical stability and controlled pore-size distribution, [5] as well as the optical, fluorescent, and magnetic properties of their precursor particles.Colloidosomes feature an identical solvent inside and out (typically water), and have been generally synthesized using micrometer-or submicrometer-sized particles. [4a,6] However, the formation of stable colloidosomes using nanoparticles (NPs) <20 nm in diameter remains a challenge. [7] The competition between the interfacial energy and the spatial fluctuation of the NPs resulting from thermal energy causes instability of the emulsions. Recent approaches to fabricate colloidosomes have included different types of NPs, as well as the use of assembly strategies. [8,9] For example, Duan et al. have used agarose to gelate water at the water-oil interface and transferred the resultant MCs into water to create stable colloidosomes. [9] In recent studies, we and others have developed various crosslinking reactions between NPs at water-oil droplet interfaces. [10] However, to the best of our knowledge there are no reports of successful transfer of these crosslinked droplets into water to synthesize colloidosomes.Herein, we report the fabrication of stable magnetic colloidosomes by crosslinking NPs at a water-oil interface using click chemistry under ambient conditions. In this strategy, alkyne-and azide-functionalized Fe 3 O 4 NPs were coassembled at the interface and covalently linked using a Cu(I)-catalyzed Huisgen click reaction. [11,12] There are two major advantages for this interfacial crosslinking method. First, click chemistry involving alkyne and azide functional groups is highly selective and essentially inert to the many functional groups and environmental conditions (e.g., pH and solvent). [13][14][15][16][17] Second, this methodology provides dense packing of NPs on the colloidosome shell, resulting in high stability of the colloidosomes.The alkyne (IO-1) and azide (IO-2) NPs used in this study were formed by place-exchange of oleic acid from Fe 3 O 4 NPs that were 11.3 AE 2 nm in diameter (see Supporting Information, Figure S1). These NPs were dissolved in an equimolar ratio in oil (a mixture of toluene and methylene chloride with a 7:1 ratio), and an aqueous solution of the Cu(I) catalyst (a mixture of CuSO 4 and sodium L-ascorbate) was added with vigorous shaking for %30 s (Scheme 1). The colloidosomes formed by this technique were 49 AE 15 mm (Figure 1a) in diameter, and required a crosslinking time of 30 min with a catalyst concentration of 0.8 mM to form stable assemblies. The catalyst concentration had little effect on the shape and size of the colloidosomes (see Supporting Information, Figure S2), however onl...

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