Naked-Eye LAMP Assay of in Sputum by In Situ Au Nanoprobe Identification: For the In Vitro Diagnostics of Tuberculosis.

In spite of the development of diagnostic tests for (), the etiological agent of tuberculosis, there has remained a gap between the established methods and an easily accessible diagnostic test, particularly in developing and resource-poor areas. By combining isothermal amplification of IS6110 as the target gene and recognition by DNA-functionalized Au nanoparticles (DNA-AuNPs), we develop a colorimetric LAMP assay for convenient in vitro diagnostics of tuberculosis with a quick (≤50 min) "yes" or "no" readout. The DNA-AuNPs not only tolerate the interference in the complex LAMP system but also afford in situ identification of the amplicon, allowing for colloidal dispersion via steric effect depending on DNA grafting density.

Correction: Effect of DNA density immobilized on gold nanoparticles on nucleic acid detection.

[This corrects the article DOI: 10.1039/D3RA06528F.].

Effect of DNA density immobilized on gold nanoparticles on nucleic acid detection.

Gold nanoparticles (AuNPs) have been utilized as colorimetric biosensors, where target molecule-induced AuNP aggregation can be recognized by a colour change from red to blue. Particularly, single-stranded DNA (ssDNA)-immobilized AuNPs (ssDNA-AuNPs) have been applied to genetic diagnosis due to their rapid and sequence-specific aggregation properties. However, the effect of the density of immobilized ssDNA have not been investigated yet.

Suppressed DNA base pair stacking assembly of gold nanoparticles in an alcoholic solvent for enhanced ochratoxin A detection in Baijiu.

The currently established DNA nanoprobes for the detection of mycotoxin from beverages have been limited by complicated sample pretreatment and uncontrollable nanoparticle flocculation in complex systems. We develop a rapid colorimetric approach for ochratoxin A (OTA) detection in Baijiu in a sample-in/"yes" or "no" answer-out fashion through target-modulated base pair stacking assembly of DNA-functionalized gold nanoparticles (DNA-AuNPs). The colorimetric signification of OTA relies on the competition of OTA with the AuNP surface-grafted DNA in binding with an OTA-targeted aptamer.

A Simple Colorimetric Assay of Bleomycin-Mediated DNA Cleavage Utilizing Double-Stranded DNA-Modified Gold Nanoparticles.

A colorimetric assay of DNA cleavage by bleomycin (BLM) derivatives was developed utilizing high colloidal stability on double-stranded (ds) DNA-modified gold nanoparticles (dsDNA-AuNPs) possessing a cleavage site. The assay was performed using dsDNA-AuNPs treated with inactive BLM or activated BLM (Fe(II)⋅BLM). A 10-min exposure in dsDNA-AuNPs with inactive BLM treatment resulted in a rapid color change from red to purple because of salt-induced non-crosslinking aggregation of dsDNA-AuNPs.

Design of a Sensitive Extracellular Vesicle Detection Method Utilizing a Surface-Functionalized Power-Free Microchip.

Extracellular vesicles (EVs), which are small membrane vesicles secreted from cells into bodily fluids, are promising candidates as biomarkers for various diseases. We propose a simple, highly sensitive method for detecting EVs using a microchip. The limit of detection (LOD) for EVs was improved 29-fold by changing the microchannel structure of the microchip and by optimizing the EV detection protocols.

Generation of transmitochondrial cybrids using a microfluidic device.

Mitochondrial cloning is a promising approach to achieve homoplasmic mitochondrial DNA (mtDNA) mutations. We previously developed a microfluidic device that performs single mitochondrion transfer from a mtDNA-intact cell to a mtDNA-less (ρ) cell by promoting cytoplasmic connection through a microtunnel between them. In the present study, we described a method for generating transmitochondrial cybrids using the microfluidic device.

Molecular detection using aptamer-modified gold nanoparticles with an immobilized DNA brush for the prevention of non-specific aggregation.

Gold nanoparticles (AuNPs) are often used for biosensing. In particular, aptamer-modified AuNPs are often used for colorimetric molecular detection, where target molecule-induced AuNP aggregates can be recognized by a color change from red to blue. However, non-specific aggregation could be induced by various compounds, leading to false-positive results.

G-Quadruplex-Functionalized Gold Nanoparticles for a Real-Time Biomolecule Sensor with On-Demand Tunable Properties.

G-quadruplex (G4) DNA-functionalized gold nanoparticles (AuNPs) were fabricated for a new sensing platform for a biomolecule, thrombin. Thrombin-binding aptamer (TBA), which forms a highly ordered G4 structure, was immobilized on AuNPs. The particles were induced to aggregate by binding of thrombin to G4 DNA.

Regeneration of the Eyespot and Flagellum in during Cell Division.

Cell division of unicellular microalgae is a fascinating process of proliferation, at which whole organelles are regenerated and distributed to two new lives. We performed dynamic live cell imaging of using optical microscopy to elucidate the mechanisms involved in the regulation of the eyespot and flagellum during cell division and distribution of the organelles into the two daughter cells. Single cells of the wild type (WT) and colorless SM-ZK cells were confined in a microfluidic device, and the appearance of the eyespot (stigma) and emergent flagellum was tracked in sequential video-recorded images obtained by automatic cell tracking and focusing.

Temporal Evolution of the Gravitaxis of from a Single Cell.

Gravitaxis is one of the most important issues in the growth of microalgae in the water column; it determines how easily cells receive sunlight with a comfortable intensity that is below the damaging threshold. We quantitatively investigated and analyzed the gravitaxis and cell multiplication of using vertically placed microchambers containing a single cell. A temporal change in gravitaxis and cell multiplication was observed after transferring the cells to fresh culture medium for 9 days.

Quantitatively Controlled Intercellular Mitochondrial Transfer by Cell Fusion-Based Method Using a Microfluidic Device.

Quantitative control of mitochondrial transfer is a promising approach for genetic manipulation of mitochondrial DNA (mtDNA) because it enables precise modulation of heteroplasmy. Furthermore, single mitochondrion transfer from a mtDNA mutation-accumulated cell to a mtDNA-less (ρ) cell potentially achieves homoplasmy of mutated mtDNA. Here we describe the method for quantitative control of mitochondrial transfer including achieving single mitochondrion transfer between live single cells using a microfluidic device.

Plasmon switching of gold nanoparticles through thermo-responsive terminal breathing of surface-grafted DNA in hydrated ionic liquids.

Self-assembly performed in ionic liquids (ILs) as a unique solvent promises distinct functions and applications in sensors, therapeutics, and optoelectronic devices due to the rich interactions between nanoparticle building blocks and ILs. However, the general consideration that common nanoparticles are readily destabilized by counterions in an IL has largely prevented researchers from investigating controlled nanoparticle assembly in IL-based systems. This study explores the assembling behaviour of double-stranded (ds) DNA-functionalized gold nanoparticles (dsDNA-AuNPs) in hydrated ionic liquids.

Terminal Sequence-Specific Interparticle Attraction between DNA Duplex-Carrying Polystyrene Microparticles in Aqueous Salt Solution Assessed by Optical Tweezers.

The dispersion behavior of DNA duplex-carrying colloidal particles in aqueous high-salt solutions shows extraordinary selectivity against the duplex terminal sequence. We investigated the interparticle force between DNA duplex-carrying polystyrene (dsDNA-PS) microparticles in aqueous salt solutions and examined their behavior in relation to the duplex terminal sequences. Force-distance () curves for a pair of dsDNA-PS particles were recorded with a dual-beam optical tweezers system with the two optically trapped particles closely approaching each other.

Electrochemical Impedimetric Study of Non-Watson-Crick Base Pairs of DNA.

Electrochemical impedance spectroscopy (EIS) was used to detect non-Watson-Crick base pairs of DNA. Thiol-modified DNA as a probe and mercaptohexanol (MCH) were co-immobilized to form a DNA/MCH mixed self-assembled monolayer on a gold electrode surface and then hybridized with complementary DNAs. The DNA layers were measured by the EIS method and interpreted by equivalent circuits.

Multiplex MicroRNA Detection on a Surface-Functionalized Power-Free Microfluidic Chip.

Circulating microRNAs (miRNAs) have emerged as promising cancer biomarkers because their concentration profiles in body fluids are associated with the type and clinical stage of cancer. For multiplex miRNA detection, a novel surface-functionalized power-free microfluidic chip (SF-PF microchip) has been developed. The inner surface of the SF-PF microchip microchannels was functionalized via electron beam-induced graft polymerization and immobilization of capture probe DNAs.

Protein-Functionalized Gold Nanoparticles for Antibody Detection Using the Darkfield Microscopic Observation of Nanoparticle Aggregation.

Gold nanoparticles (AuNPs) are commonly used in biosensing applications. In this study, AuNPs were synthesized by using reduced bovine serum albumin (rBSA) as the reducing agent. The rBSA conjugated with AuNPs via Au-Sulfur interactions to form rBSA-functionalized AuNPs (rBSA-AuNPs).

A Microfluidic Device for Modulation of Organellar Heterogeneity in Live Single Cells.

The quantitatively controlled organellar transfer between living single cells provides a unique experimental platform to analyze the contribution of organellar heterogeneity on cellular phenotypes. We previously developed a microfluidic device which can perform quantitatively controlled mitochondrial transfer between live single cells by promoting strictured cytoplasmic connections between live single cells, but its application to other organelles is unclear. In this study, we investigated the quantitative properties of peroxisome transfer in our microfluidic device.

DNA Terminal-Specific Dispersion Behavior of Polystyrene Latex Microparticles Densely Covered with Oligo-DNA Strands Under High-Salt Conditions.

We prepared microspheres densely covered with oligo-DNA strands by immobilizing amino-terminated oligo-DNA strands on the surface of carboxylate polystyrene latex (PS) particles via the amide bond formation. The obtained microspheres (ssDNA-PS) stably dispersed in neutral pH buffer containing high concentrations of NaCl. For the ssDNA-PS ≥1 μm diameter, only 3 - 5% of surface-immobilized oligo-DNA could form a duplex with the complementary strands.

Photo-switching of blunt-end stacking between DNA strands immobilized on gold nanoparticles.

End-to-end intermolecular interaction between double-stranded DNAs grafted onto individual nanoparticles is regulated by terminal base pairing/unpairing triggered by the photo-isomerization of an azobenzene moiety inserted in the vicinity of the DNA terminal. This is the first example of highly reversible control of blunt-end stacking under both isothermal and isoionic-strength conditions.

DNA Base Pair Stacking Assembly of Anisotropic Nanoparticles for Biosensing and Ordered Assembly.

Anisotropic gold nanoparticles have attracted great interest due to their unique physicochemical properties derived from the shape anisotropy. Manipulation of their interfacial interactions, and thereby the assembling behaviors are often requisite in their applications ranging from optical sensing and diagnosis to self-assembly. Recently, the control of interfacial force based on base pair stacking of DNA terminals have offered a new avenue to surface engineering of nanostructures.

Opposite Effects of Flexible Single-Stranded DNA Regions and Rigid Loops in DNAzyme on Colloidal Nanoparticle Stability for "Turn-On" Plasmonic Detection of Lead Ions.

Strains in biomolecules greatly restrict their structural flexibility. The effects of DNA's structural flexibility on nanoparticle stability have remained less explored in the field of plasmonic biosensors. In the present study, we discover the opposite effects of a rigid loop and a flexible single-stranded DNA (ssDNA) region in DNAzyme on the colloidal stability of gold nanoparticles (AuNPs), which afford "turn-on" plasmonic detection of Pb.

Carotenoid accumulation in the eyespot apparatus required for phototaxis is independent of chloroplast development in Euglena gracilis.

Euglena gracilis exhibits photomovements in response to various light stimuli, such as phototactic and photophobic responses. Our recent study revealed that carotenoids in the eyespot apparatus are required for triggering phototaxis in this alga. However, the role of chloroplasts in eyespot formation is not understood.

DNA-Programmed Bimodal 2D Assembly of Differently Sized Nanoparticles via Folding of Precursory Circular Chains.

Gold nanoparticle (AuNP) assemblies in two-dimensions (2D) exhibit collective physical/chemical properties that are useful for various devices. However, technical issues still impede the efficient ordering of differently sized AuNPs on solid supports while avoiding phase separation. This paper describes a method to construct binary 2D assemblies by folding precursory circular chains composed of small and large AuNPs.