Weighing nanoparticles in solution at the attogram scale.

Physical characterization of nanoparticles is required for a wide range of applications. Nanomechanical resonators can quantify the mass of individual particles with detection limits down to a single atom in vacuum. However, applications are limited because performance is severely degraded in solution. Suspended micro- and nanochannel resonators have opened up the possibility of achieving vacuum-level precision for samples in the aqueous environment and a noise equivalent mass resolution of 27 attograms in 1-kHz bandwidth was previously achieved by Lee et al. [(2010) Nano Lett 10(7):2537-2542]. Here, we report on a series of advancements that have improved the resolution by more than 30-fold, to 0.85 attograms in the same bandwidth, approaching the thermomechanical noise limit and enabling precise quantification of particles down to 10 nm with a throughput of more than 18,000 particles per hour. We demonstrate the potential of this capability by comparing the mass distributions of exosomes produced by different cell types and by characterizing the yield of self-assembled DNA nanoparticle structures.

Tandem arrays of TEMPO and nitronyl nitroxide radicals with designed arrangements on DNA.

Herein we describe one-dimensional electron-spin arrays consisting of two different organic radicals with the designed arrangement based on the DNA sequence. Two mismatch-binding ligands carrying 2,2,6,6-tetramethylpiperidine N-oxide (TEMPO) and nitronyl nitroxide selectively bind to the predetermined sites on double stranded DNA. By using the two mismatch-binding ligands carrying the organic radicals as the glue for DNA, electron-spin assembly could be successfully synchronized with the hybridization. Periodically and tandemly arranged, two kinds of organic radical molecules at designed positions might be useful for an approach to build up scalable qubits of electron-spin-based quantum computing. The approach using DNA nanostructures as a scaffold to assembly functional small molecules can afford one of the promising ways for the future application of DNA nanostructures and nanotechnology.

DNA Origami and G-Quadruplex Hybrid Complexes Induce Size Control of Single-Walled Carbon Nanotubes via Biological Activation.

DNA self-assembly has enabled the programmable fabrication of nanoarchitectures, and these nanoarchitectures combined with nanomaterials have provided several applications. Here, we develop an approach for cutting single-walled carbon nanotubes (SWNTs) of predetermined lengths, using DNA origami and G-quadruplex hybrid complexes. This approach is based on features of DNA: (1) wrapping SWNTs with DNA to improve the dispersibility of SWNTs in water; (2) using G-quadruplex DNA to confine hemin in close proximity to SWNTs and enhance the biological activation of hydrogen peroxide by hemin; and (3) forming DNA origami platforms to allow for the precise placement of G-quadruplexes, enabling size control. These integrated features of DNA allow for temporally efficient cutting of SWNTs into desired lengths, thus expanding the availability of SWNTs for applications in the fields of nanoelectronics, nanomedicine, nanomaterials, and quantum physics, as well as in fundamental studies.

Harnessing the hygroscopic and biofluorescent behaviors of genetically tractable microbial cells to design biohybrid wearables.

Cells' biomechanical responses to external stimuli have been intensively studied but rarely implemented into devices that interact with the human body. We demonstrate that the hygroscopic and biofluorescent behaviors of living cells can be engineered to design biohybrid wearables, which give multifunctional responsiveness to human sweat. By depositing genetically tractable microbes on a humidity-inert material to form a heterogeneous multilayered structure, we obtained biohybrid films that can reversibly change shape and biofluorescence intensity within a few seconds in response to environmental humidity gradients. Experimental characterization and mechanical modeling of the film were performed to guide the design of a wearable running suit and a fluorescent shoe prototype with bio-flaps that dynamically modulates ventilation in synergy with the body's need for cooling.

Ligand-induced electron spin-assembly on a DNA tile.

By binding of a ligand molecule carrying an electron spin to a guanine-guanine mismatch in a DNA duplex on a DNA tile, a three-dimensional assembly of electron spins was successfully constructed.

Ligand inducible assembly of a DNA tetrahedron.

Here we show that a small synthetic ligand can be used as a key building component for DNA nanofabrication. Using naphthyridinecarbamate dimer (NCD) as a molecular glue for DNA hybridization, we demonstrate NCD-triggered formation of a DNA tetrahedron.

Programmed assembly of organic radicals on DNA.

Nitronyl nitroxide radical introduced to naphthyridine carbamate dimer is noncovalently bound to a CGG/CGG triad as an addressable position in DNA duplexes, leading to the programmed assembly of the radical molecules into an 11-mer duplex and a tandem repetitive array of double stranded DNA.

Fluorescence-based affinity labeling of nucleobase by hydrogen-bond forming metal complex.

A new class of nucleobase-binding fluorescent ligand, ND-DOTA in which 2-amino-5,7-dimethyl-1.8-naphthyridine (ND) is conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DOTA) by an amide linker, was synthesized. On the basis of the experimental results obtained from the DNA melting analysis and fluorescent measurement, ND-DOTA-Tb (III) complex was found to strongly recognize cytosine (C) base opposite an abasic site in DNA duplexes. The binding of ND-DOTA-Tb (III) with C was accompanied by significant quenching of the fluorescence from the naphthyridine moiety (lambdamax, 435 nm), while the emission from the Tb based on lanthanoids energy-transfer luminescence (lambdamax, 550 nm) was relatively unaffected. Such a fluorescence response of ND-DOTA-Tb (III) is to be expected to develop the fluorescence-based affinity labelling of a nucleobase at the single-nucleotide segments in DNA duplexes.