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Nanochannel-based plasmon-enhanced Raman scattering (PERS) substrates can simulate biological environments, revealing the recognition and conformation information on biomolecules in confined spaces. In this work, a metamaterial nanochannel-based PERS platform was constructed for highly sensitive analysis of DNA recognition to Hg 2+ with the lowest Hg 2+ concentration down to 1.0 pM. The established platform enables in situ monitoring of the thermodynamics and kinetics of DNA-Hg 2+ recognition reaction in a confined nanospace. The recognition reaction in a nanospace shows good reversibility and specificity, and the isotherm follows well the Freundlich adsorption model. Compared to its folding on a rough Au nanofilm, the folding time of ssDNA-Rox decorated in nanochannels is remarkably increased, and the folding process can be tuned through varying the pore size and ionic strength. The presented PERS platform is promising for studying biomolecule-ion binding events and biomolecule conformation change under nanochannel-confined conditions.

Inorganic nanomaterials with intrinsic singlet oxygen ( 1 O 2 ) generation capacity, are emerged yet dynamically developing materials as nano-photosensitizers (NPSs) for photodynamic therapy (PDT). Compared to previously reported nanomaterials that have been used as either carriers to load organic PSs or energy donors to excite the attached organic PSs through a Foster resonance energy transfer process, these NPSs possess intrinsic 1 O 2 generation capacity with extremely high 1 O 2 quantum yield (e.g., 1.56, 1.3, 1.26, and 1.09) than any classical organic PS reported to date, and thus are facilitating to make a revolution in PDT. In this review, the recent advances in the development of various inorganic nanomaterials as NPSs, including metal-based (gold, silver, and tungsten), metal oxide-based (titanium dioxide, tungsten oxide, and bismuth oxyhalide), metal sulfide-based (copper and molybdenum sulfide), carbon-based (graphene, fullerene, and graphitic carbon nitride), phosphorus-based, and others (hybrids and MXenes-based NPSs) are summarized, with an emphasis on the design principle and 1 O 2 generation mechanism, and the photodynamic therapeutic performance against different types of cancers. Finally, the current challenges and an outlook of future research are also discussed. This review may provide a comprehensive account capable of explaining recent progress as well as future research of this emerging paradigm., (© 2021 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Cell-surface receptors (e.g., EGFR and integrin) and their interactions play determining roles in signal transduction and cytoskeletal activation, which affect cell attachment/detachment, invasion, motility, metastasis (intracellular), and cell-cell signaling. For instance, the interactions between the EGFR and integrin (α6β4) may cause increased mechanical force and shear stress via enhanced cytoskeleton activation. Here, we design a DNA nanodevice (DNA-ND) that can simultaneously target the EGFR and integrin receptors on the caveolae. The piconewton (pN) forces in response to the EGFR-integrin coactivation can be sensed upon the unfolding of the DNA hairpin structure on the side arm of the device via changes of the fluorescence and plasmonic signals. We find that simultaneous activation of EGFR-integrin receptors causes enhanced signal transduction, contractions of the cells, and initiation of the biochemical pathways, thus resulting in a change of the cell division and endocytosis/exocytosis processes that affect the cell proliferation/apoptosis. The DNA-ND further enables us to visualize the cointernalization and degradation of the receptors by lysosomes, providing a novel approach toward bioimaging and mechano-pharmacology.

Background: Delivery of foreign cargoes into cells is of great value for bioengineering research and therapeutic applications., Objective: In this study, we proposed and established a carrier-free gene delivery platform utilizing staggered herringbone channel and silicon nanoneedle array, to achieve high-throughput in vitro gene transfection., Methods: With this microchip, fluidic micro vortices could be induced by the staggered-herringboneshaped grooves within the channel, which increased the contact frequency of the cells with the channel substrate. Transient disruptions on the cell membrane were well established by the nanoneedle array on the substrate., Result: Compared to the conventional nanoneedle-based delivery system, proposed microfluidic chip achieved flow-through treatment with high gene transfection efficiency (higher than 20%) and ideal cell viability (higher than 95%)., Conclusion: It provides a continuous processing environment that can satisfy the transfection requirement of large amounts of biological molecules, showing high potential and promising prospect for both basic research and clinical application., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

We demonstrate a core-satellite plasmonic nanoprobe assembled via metal-ion-dependent DNA-cleaving DNAzyme linker for imaging intercellular metal ion based on plasmon coupling effect at a single-particle level. As metal ions are present in the system, the DNAzyme linker will be cleaved, and thus, disassembly of the core-satellite nanoprobes occurs, which results in distinct blue shift of the scattering spectra of Au core-satellite probes and naked color change of the scattering light. This change in scattering spectra has been supported by theoretical simulations. As a proof of concept, sensitive detection of Cu 2+ with a limit of detection down to 67.2 pM has been demonstrated. The nanoprobes have been further utilized for intracellular Cu 2+ imaging in living cells. The results demonstrate that the present strategy provides a promising platform for detection and imaging of metal ions in living cells and could be potentially applied to imaging other interesting target molecules simply by substituting the oligonucleotide sequence.

Water-soluble and non-aggregating gold nanoclusters (AuNCs) were obtained by modification of the AuNCs with dithiothreitol (DTT) and then coating them with carboxylated chitosan. This process remarkably enhances the dispersibility of DTT-coated AuNCs in water. The resulting AuNCs, on photoexcitation at 285 nm, display strong red emission with a maximum at 650 nm and a 23% quantum yield. Fluorescence is strongly and selectively suppressed in the presence of 6-mercaptopurine (6-MP). Photoluminescence drops linearly in the 0.1-100 μM 6-MP concentration range, and the detection limit of this assay is 0.1 μM. Other features of the modified AuNCs include a decay time of 8.56 μs, a 365 nm Stokes shift, good colloidal stability, ease of chemical modification, and low toxicity. Conceivably, these NCs may find a range of applications in biological imaging and optical sensing. Graphical abstract Highly fluorescent and water-soluble gold nanoclusters (AuNCs) were obtained by modification of the AuNCs with dithiothreitol (DTT) and then coating them with carboxylated chitosan (CC). The resulting CC/DTT-AuNCs were used for sensitive and selective detection of 6-mercaptopurine.

A versatile and sensitive platform for label-free bioanalysis has been proposed on the basis of attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) using Au/ZnSe as the enhancement substrate that allows a wide spectral range down to 700 cm -1 . Au nanoparticles are stably deposited on the surface of a ZnSe prism due to the formation of Au-Se bonds via electroless deposition, and the enhancement factor of the resultant Au/ZnSe substrate is about 2 times larger than that of the commonly used Au/Si substrate. As a demonstration, the Au/ZnSe-based SEIRAS has been applied to obtain abundant structural information in the fingerprint region and quantitative analysis of various biomolecular interactions such as DNA hybridization and immunoreaction without any labeling process.

With the growing demands of the early, accurate, and sensitive diagnosis for cancers, the development of new diagnostic technologies becomes increasingly important. In this study, we proposed a strategy for efficient capture and sensitive detection of circulating tumor cells (CTCs) using an array nanochannel-ion channel hybrid coupled with an electrochemical detection technique. The aptamer probe was immobilized on the ion channel surface to couple with the protein overexpressed on the CTCs membrane. Through this special molecular recognition, CTCs can be selectively captured. The trapped CTCs cover the ion channel entrance efficiently, which will dramatically block the ionic flow through channels, resulting in a varied mass-transfer property of the nanochannel-ion channel hybrid. On the basis of the changed mass-transfer properties, the captured CTCs can be sensitively detected using the electrochemical linear sweep voltammetry technique. Furthermore, due to the amplified response of array channels compared to that of a single channel, the detection sensitivity can be enhanced greatly. The results showed that acute leukemia CCRF-CEM (a type of CTC) concentration as low as 100 cells mL -1 can be successfully captured and detected. The present method provides a simple, sensitive, and label-free technique for CTCs capture, detection, and release, which would hold great potential in the early clinical diagnosis and treatment of cancers.

This paper reports a new and facile method for the synthesis of water-soluble thiolate-protected AuNCs via protein-ligand interaction. Using 3-mercaptopropionic acid (MPA) as a model ligand and bovine serum albumin (BSA) as a model protein, water-soluble AuNCs (BSA/MPA-AuNCs) with intense orange-yellow fluorescent emission (quantum yield=16%) are obtained. Results show that AuNCs produced with this method have hydrophobic interactions with BSA. The synthetic strategy is then successfully extended to produce water-soluble AuNCs protected by other thiolates. Moreover, a sensitive and eco-friendly sensing system is established for detection of the activity of inorganic pyrophosphatase (PPase), which relies on the selective coordination of Fe(3+)with BSA/MPA-AuNCs, the higher affinity between pyrophosphate (PPi) and Fe(3+), and the hydrolysis of PPi by PPase. A good linearity between the fluorescence intensity and PPase activity within the range from 0.1 to 3U/L is found, with a detection limit down to 0.07U/L. Additionally, the fluorescent assay developed here is utilized to assay the PPase activity in real biological samples and as well as to evaluate PPase inhibitor, illustrating the great potential for biological analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Supramolecular steric hindrance designs make pyrene-functionalized spiro[fluorene-9,7'-dibenzo[c,h]acridine]-5'-one (Py-SFDBAO) assemble into 2D nanostructures that facilitate aqueous phase large-area synthesis of high-quality and uniform crystalline thin films. Thin-film diodes using aqueous nanosheets as active layers exhibit a non-volatile bistable electrical switching feature with ON/OFF ratios of 6.0 × 10(4) and photoswitching with conductive gains of 10(2) -10(3). Organic nanosheets are potentially key components for eco-friendly aqueous dispersed organic nano-inks in the application of printed and flexible electronics., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report a controllable method to fabricate silica colloidal crystals at defined position in microchannel of microuidic devices using simple surface modification. The formed PCs (photonic crystals) in microfluidic channels were stabilized by chemical cross-linking of Si-O-Si bond between neighboring silica beads. The voids among colloids in PCs integrated on microfluidic devices form interconnected nanoporous networks, which show special electroosmotic properties. Due to the "surface-charge induced ion depletion effect" mechanism, FITC-labeled proteins can be efficiently and selectively concentrated in the anodic boundary of the ion depletion zone. Using this device, about 10(3) - to 10(5)-fold protein concentration was achieved within 10 min. The present simple on chip protein concentration device could be a potential sample preparation component in microfluidic systems for practical biochemical assays., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Graphene can be viewed as an individual atomic plane extracted from graphite, as unrolled single-walled carbon nanotube or as an extended flat fullerene molecule. In this paper, a facile approach to the synthesis of high quality graphene nanosheets in large scale through electrochemical reduction of exfoliated graphite oxide precursor at cathodic potentials (completely reduced potential: -1.5 V) is reported. This method is green and fast, and will not result in contamination of the reduced material. The electrochemically reduced graphene nanosheets have been carefully characterized by spectroscopic and electrochemical techniques in comparison to the chemically reduced graphene-based product. Particularly, FTIR spectra indicate that a variety of the oxygen-containing functional groups have been thoroughly removed from the graphite oxide plane via electrochemical reduction. The chemically converted materials are not expected to exhibit graphene's electronic properties because of residual defects. Indeed, the high quality graphene accelerates the electron transfer rate in dopamine electrochemistry (DeltaE(p) is as small as 44 mV which is much smaller than that on a glassy carbon electrode). This approach opens up the possibility for assembling graphene biocomposites for electrocatalysis and the construction of biosensors.

We used polyethyleneglycol (PEG) as a modulator to manipulate pore and cell sizes in the porous anodic alumina (PAA) fabrication. It is shown for the first time that continuous manipulation of the pore size of PAA can be realized. Combined with the coexistent cell-size controlling effect, the morphology and properties of this important nanoscale template and separation membrane can be precisely regulated. The pore size modulation mechanism is proposed on the basis of the morphological and electrochemical results. The presence of PEG in the electrolyte results in a more compacted structure of the barrier layer alumina (BLA), although the barrier layer thickness does not change considerably. In addition, the additive can obviously restrain the chemical dissolution of alumina and shape smaller pores. These two effects combined with the increased viscosity of the electrolyte slow down the ion transportation and diminish the anodization current. Thus, the burning-down phenomena of the aluminum substrates can be avoided at relatively high voltage anodization, and an interpore distance up to 610 nm can be achieved.

Hollow carbon nanospheres (HCNS) with large surface area were synthesized from hollow chitosan nanospheres by one-step pyrolysis with a relatively low temperature (550 degrees C). The resulted HCNS is fully carbonized and partially graphitized under the experiment conditions. It is an important and facile method to prepare the uniform, shape- and size-controlled carbon nanomaterials by carbonization of the natural polysaccharide compounds and their derivatives. The as-prepared HCNS has a narrow size distribution in hollow carbon nanospheres (about 53 nm). The structure and size of HCNS are reproducible and could be tunable by changing the preparation conditions. The characterizations to estimate the composition, decompose properties, crystalline form, structure and surface property of the HCNS were investigated using FT-IR spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction measurement (XRD), transmission electron microscopy (TEM) analysis, and the N2 adsorption-desorption isothermal process. The present preparation method makes it feasible to synthesize carbon nanospheres in abundance in the lab, and the synthesized HCNS could be a promising support for metal catalysts, an ideal matrix connecting with DNA or other bioactive substances.

A three-dimensionally ordered, macroporous, inverse-opal platinum film was synthesized electrochemically by the inverted colloidal-crystal template technique. The inverse-opal film that contains platinum nanoparticles showed improved electrocatalytic activity toward glucose oxidation with respect to the directly deposited platinum; this improvement is due to the interconnected porous structure and the greatly enhanced effective surface area. In addition, the inverse-opal Pt-film electrode responds more sensitively to glucose than to common interfering species of ascorbic acid, uric acid, and p-acetamidophenol due to their different electrochemical reaction mechanisms. Results showed that the ordered macroporous materials with enhanced selectivity and sensitivity are promising for fabrication of nonenzymatic glucose biosensors.

A multilayered glucose biosensor via sequential deposition of Prussian blue (PB) nanoclusters and enzyme-immobilized poly(toluidine blue) films was constructed on a bare Au electrode using electrochemical methods. The whole configuration of the present biosensor can be considered as an integration of several independent hydrogen peroxide sensing elements. In each sensing element, the poly(toluidine blue) film functioned as both the supporting matrix for the glucose oxidase immobilization and the inhibitor for the diffusion of interferences, such as ascorbic acid and uric acid. Meanwhile, the deposited Prussian blue nanocluster layers acts as a catalyst for the electrochemical reduction of hydrogen peroxide formed from enzymatic reaction. Performance of the whole multilayer configuration can be tailored by artificially arranging the sensing elements assembled on the electrode. Under optimal conditions, the biosensors exhibit a linear relationship in the range of 1 x 10(-4) to 1 x 10(-2) mol/L with the detection limit down to 10(-5) mol/L. A rapid response for glucose could be achieved in less than 3 s. For 1 mM glucose, 0.5 mM acetaminophen, 0.2 mM uric acid, and 0.1 mM ascorbic acid have no obvious interferences (<5%) for glucose detection at an optimized detection potential. The present multilayered glucose biosensor with a high selectivity and sensitivity is promising for practical applications.

A biocompatible and uniform interface based on silica nanoparticles derivatized with amino groups has been constructed for the effective immobilization and sensitive sequence-specific detection of calf thymus DNA. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results showed that a monolayer of silica nanoparticles can be formed on a gold electrode under our experimental conditions using cysteine self-assembly monolayer as binder medium. Electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy (XPS) verified the successful immobilization of DNA on silica-nanoparticle-modified gold electrodes. Quantitative results demonstrated that enhanced immobilization of single-strand DNA (ss-DNA) up to 1.6 x 10(-8) mol cm(-2) could be achieved owing to the larger surface area and the special properties of silica nanoparticles. In addition, hybridization experiments demonstrated that the immobilized ss-DNA on silica nanoparticles could specifically interact with complementary DNA in solutions.