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The unique ion-transport properties in nanoconfined pores enable nanofluidic devices with great potential in harvesting osmotic energy. The energy conversion performance could be significantly improved by the precise regulation of the "permeability-selectivity" trade-off and the ion concentration polarization effect. Here, we take the advantage of electrodeposition technique to fabricate a Janus metal-organic framework (J-MOF) membrane that possesses rapid ion-transport capability and impeccable ion selectivity. The asymmetric structure and asymmetric surface charge distribution of the J-MOF device can suppress the ion concentration polarization effect and enhance the ion charge separation, exhibiting an improved energy harvesting performance. An output power density of 3.44 W/m 2 has been achieved with the J-MOF membrane at a 1000-fold concentration gradient. This work provides a new strategy for fabricating high-performance energy-harvesting devices.

The simultaneous and accurate detection of intracellular pH (pH i ) and extracellular pH (pH e ) is essential for studying the complex physiological activities of cancer cells and exploring pH-related therapeutic mechanisms. Here, we developed a super-long silver nanowire-based surface-enhanced Raman scattering (SERS) detection strategy for simultaneous sensing of pH i and pH e . A surface-roughened silver nanowire (AgNW) with a high aspect ratio is prepared at a nanoelectrode tip using a Cu-mediated oxidation process, which is then modified by pH-sensitive 4-mercaptobenzoic acid (4-MBA) to form 4-MBA@AgNW as a pH sensing probe. With the assistance of a 4D microcontroller, 4-MBA@AgNW is efficient in simultaneously detecting pH i and pH e in both 2D and 3D culture cancer cells by SERS, with minimal invasiveness, high sensitivity, and spatial resolution. Further investigation proves that the surface-roughened single AgNW can also be used in monitoring the dynamic variation of pH i and pH e of cancer cells upon stimulation with anticancer drugs or under a hypoxic environment.

Biological ion pumps with two separate gates can actively transport ions against the concentration gradient. Developing an artificial nanofluidic device with multiple responsive sites is of great importance to improve its controllability over ion transport to further explore its logic function and mimic the biological process. Here, we propose an electrochemical polymerization method to fabricate electrochemically switchable double-gate nanofluidic devices. The ion transport of the double-gate nanofluidic device can be in situ and reversibly switched among four different states. The logic function of this nanofluidic device is systematically investigated by assuming the gate state as the input and the transmembrane ionic conductance as the output. A biomimetic electrochemical ion pump is then established by alternately applying two different specific logic combinations, realizing an active ion transport under a concentration gradient. This work would inspire further studies to construct complex logical networks and explore bioinspired ion pump systems.

Miniaturized and manipulable optical probes are the foundation for developing in situ characterization devices in confined space. We developed two methods for fabricating free-standing single Ag nanowires (AgNWs) directly at the tip of a glass capillary either by chemical or electrochemical reduction. The electrochemical nature of both methods resulted in a rapid growth rate of AgNWs up to 1.38 μm/s and a controllable length from 5 to 450 μm. The AgNWs with a unique anisotropic structure allow localized surface plasmon resonance and surface plasmon waveguides in the radial direction and axial direction, respectively. We verified the possibility of using single AgNWs as an optical dispersion device and waveguide probe. By controlling the experimental conditions, rough-surface AgNWs with high surface-enhanced Raman scattering (SERS) activity were also fabricated. These SERS-active probes also exhibited advantages in acquiring molecular information from a single living cell.

Metal-organic frameworks (MOFs), especially those made by biological molecules (bio-MOFs), have been proved to be prospective candidates for biomedical applications. However, a simple and universal bio-MOF to load different substances for precise targeting is still lacking. In this work, we propose a facile one-pot method to prepare a peptide-doped bio-MOF for general encapsulation and targeted delivery. This bio-MOF is constructed by 9-fluorenylmethyloxycarbonyl-modified histidine (Fmoc-His) as a bridging linker that coordinates with Zn 2+ ions, denoted as ZFH. The Fmoc-His-Asp-Gly-Arg peptide (Fmoc-HDGR) can be easily doped into the ZFH structure with different ratios to modulate the targeting ability of ZFH-DGR. Containing both hydrophobic Fmoc and hydrophilic His moieties, this framework is compatible with encapsulating various types of payloads, including hydrophobic chemotherapeutic, hydrophilic protein, and positively/negatively charged inorganic nanoparticles. It has also been proved to be highly biocompatible and stable in circulation, exhibit the capabilities to target α ν β 3 integrin overexpressed on tumor cells, and trigger drug release in a low pH microenvironment at the tumor site. As a proof of concept, Doxorubicin (Dox)-loaded ZFH-DGR (ZFH-DGR/Dox) demonstrated high cell selectivity between liver hepatocellular carcinoma (HepG2) cells and normal liver (L02) cells, which express high and low α ν β 3 integrin, respectively. This selectivity endows ZFH-DGR/Dox precise treatment and low toxicity in Heps-bearing liver cancer mice. This work develops a de novo approach to construct a peptide-doped bio-MOF system for universal load, precise delivery, and peptide drug combination therapy in the future.

Electrochemical conversion of N 2 to NH 3 under ambient conditions is a promising and environmentally friendly route compared with the CO 2 -emitting and energy-intensive Haber-Bosch process. Nevertheless, due to ultrahigh stability of N 2 , it is urgent to explore efficient catalysts to weaken and activate the N≡N bond. Here, we report the Mo-doped iron phosphide (Mo-FeP) nanosphere as a valid transition-metal-based catalyst for electrochemical N 2 -to-NH 3 fixation under ambient conditions. This catalyst exhibits excellent catalytic performance with a NH 4 + yield rate (13.1 μg h -1 mg -1 ) and Faradaic efficiency (7.49%) at -0.3 and -0.2 V vs reversible hydrogen electrode (RHE), respectively. However, the FeP catalyst without doped Mo species displays weak catalytic performance. We found that the better catalytic performance of Mo-FeP might be due to the doping of Mo species, which is favorable for the polarization of adsorbed N 2 molecules, making the N≡N bond more viable to dissociate.

Protein-supported nanoparticles have a great significance in scientific and nanotechnology research because of their "green" process, low cost-in-use, good biocompatibility, and some interesting properties. Ruthenium oxide nanoparticles (RuO 2 NPs) have been considered to be an important member in nanotechnology research. However, the biosynthetic approach of RuO 2 NPs is relatively few compared to those of other nanoparticles. To address this challenge, this work presented a new way for RuO 2 NP synthesis (BSA-RuO 2 NPs) supported by bovine serum albumin (BSA). BSA-RuO 2 NPs are confirmed to exert peroxidase-like activity, electrocatalytic activity, in vitro salt resistance (2 M NaCl), and biocompatibility. Results indicate that BSA-RuO 2 NPs have higher affinity binding for 3,3',5,5'-tetramethylbenzidine or H 2 O 2 than bare RuO 2 NPs. Moreover, BSA turns out to be a crucial factor in promoting the stability of RuO 2 NPs. Taking the advantages of these improved properties, we established colorimetric (linear range from 2 to 800 μM, a limit of detection of 1.8 μM) and electrochemical (linear range from 0.4 to 3850 μM, a limit of detection of 0.18 μM) biosensors for monitoring in situ H 2 O 2 secretion from living MCF-7 cells. Herein, this work offers a new biosynthesis strategy to obtain BSA-RuO 2 NPs and sheds light on the sensitive biosensors to monitor the H 2 O 2 secreted from living cells for promising applications in the fields of nanotechnology, biology, biosensors, and medicine.

Few-atom gold nanoclusters (AuNCs) have been fabricated and used for various fields owing to their remarkable optical and photophysical features. However, the rational design for the antibody-mediated synthesis of fluorescent AuNCs for direct antigen-antibody reactions remains unexplored. In this work, immunoglobulin G (IgG)-functionalized AuNCs (IgG-AuNCs) were successfully prepared via a facile and fast biomineralization process. The generated IgG-AuNCs can emit intense red fluorescence with a high photoluminescence quantum yield. Besides strong emission, the bioactivity of IgG on the IgG-AuNCs can be retained. Surface plasmon resonance measurements suggested that IgG-AuNCs can bind to goat anti-human IgG with an affinity constant of 6.21 × 10 -8 M. A simple detection method was then developed using a dot-blot immunoassay with IgG-AuNCs as fluorescent tags. Experimental results confirmed that the IgG-AuNC-based fluorescent reporters had many advantages such as low nonspecific adsorption and good photostability, offering immense potential for the development of efficient biosensors. This work can be extended to other specific antibodies to produce multifunctional AuNCs and utilized to detect and monitor targeted analytes and biological events of interest.

We report a high-performance Ru@C 4 N electrocatalyst for the hydrogen evolution reaction (HER) in both acidic and alkaline solutions. This catalyst is synthesized by annealing a complex of a covalent organic framework compound coordinated with ruthenium synthesized by a "one-pot" solvothermal method. This Ru@C 4 N catalyst shows excellent electrocatalytic activity toward the hydrogen evolution reaction (HER) in both acidic and alkaline solutions with very low overpotentials at 10 mA/cm 2 (6 mV in 0.5 M H 2 SO 4 solution; 7 mV in 1.0 M KOH solution), which outperforms the commercial catalyst Pt/C. The Ru@C 4 N electrocatalyst also exhibits high HER turnover frequencies of 0.93 H 2 per s in 0.5 M H 2 SO 4 and 0.65 H 2 per s in 1.0 M KOH solutions at 25 mV as well as superior performance stability.

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.

The development of simple yet powerful methods for monitoring enzyme activity is of great significance. Herein, a facile, convenient, cost-effective, and continuous fluorescent method for the detection of arginase and its inhibitor has been reported based on a host-guest interaction-controlled and enzymatic hydrolysis-controlled luminescent nanoswitch. The fluorescence intensity of 6-aza-2-thiothymine-stabilized gold nanoparticle (ATT-AuNP) is enhanced by l-arginine, owing to the formation of a supramolecular host-guest assembly between the guanidine group of l-arginine and ATT molecules capped on the AuNP surface. However, hydrolysis of l-arginine, catalyzed by arginase, leads to a decrease in the fluorescence intensity of l-arginine/ATT-AuNPs hybrids. Upon incorporation of the arginase inhibitor l-norvaline, the fluorescence of the ATT-AuNP-based detecting system is restored. The linear range of arginase activity determination is from 0.0625 to 1.15 U/mL and the limit of detection is 0.056 U/mL. The half-maximal inhibition value IC 50 of l-norvaline is determined to be 5.6 mM. The practicability of this luminescent nanoswitch is validated by assaying the arginase activity in rat liver and monitoring the response of rat liver arginase to pharmacological agent. Compared to the existing fluorescent method of arginase activity assay, the approach demonstrated here does not involve any complicated technical manipulation, thereby greatly simplifying the detection steps. We propose that this AuNP-based luminescent nanoswitch would find wide applications in the field of life sciences and medicine.

The effective capture and release of circulating tumor cells (CTCs) is of significant importance in cancer prognose and treatment. Here we report a highly efficient method to capture and release human leukemic lymphoblasts (CCRF-CEM) using aptamers modified gold nanowire arrays (AuNWs). The gold nanowires, showing tunable morphologies from relatively random pillar deposit to relatively uniform arrays, were fabricated by electrochemical deposition using anodic aluminum oxide (AAO) as template. Upon simply being modified with aptamers by Au-S chemistry, the AuNWs exhibit higher specificity to target cells. Also compared to flat gold substrate, the AuNWs with nanostructure can capture target cells with much higher capture yield. Moreover, the captured CCRF-CEM cells can be released from AuNWs efficiently with little damage through an electrochemical desorption process. We predict that our strategy has great potential in providing a simple and economical platform for CTCs isolation, cancer diagnosis, and therapy.

Intraorgan targeting of chemical drugs at tumor tissues is essential in the treatment of solid tumors that express the same target receptor as normal tissues. Here, asialoglycoprotein receptor (ASGP-R)-targeting paclitaxel-conjugated gold nanoparticles (Gal/PTX-GNPs) are fabricated as a demonstration to realize the precise treatment of liver cancer. The enhanced biological specificity and therapeutic performance of drugs loaded on nanoparticles not only rely on the ligands on carriers for receptor recognition but are also determined by the performance of gold conjugates with designed structure. The tumor cell selectivity of the designed conjugates in liver tumor (HepG2) cells is close to six times of that incubated with control conjugates without galactose modification in liver normal (L02) cells. The drug level in tumor versus liver of Gal/PTX-GNPs is 121.0% at 8 h post injection, a 15.7-fold increase in the tumor specificity compared to that of GNPs conjugated with PTX only. This intraorgan-targeting strategy results in a considerable improvement of performance in treating both Heps heterotopic and orthotopic xenograft tumor models, which is expected to be used for the enhanced antitumor efficacy and reduced hepatotoxicity in liver cancer treatment.

Metal-encapsulated nitrogen-doping porous carbonaceous materials (NDPCs) prepared from metalloporphyrin-based covalent organic frameworks (MP-COFs) have become very promising candidates for highly effective oxygen reduction electrocatalysts. To enhance the ORR performance and durability of these NDPCs in novel energy conversion and storage devices, we develop a new type of metal-encapsulated NDPCs (HBY-COF-900) composed of FeN 4 active sites by introduction of metalloporphyrin into porous COFs. Comparable to the benchmark 20% Pt/C, HBY-COF-900 in acidic solutions exhibits higher oxygen reduction electrocatalytic activity, long-term durability, and good CO tolerance. These properties can be attributed to a synergistic effect of FeN 4 active sites, high graphitization, and porous structure. This work opens an avenue for the development of metal-encapsulated NDPCs from three-dimensional polyporphyrin prepared by one-step polymerization.

Pt-free electrocatalysts with high activity and low cost are highly pursued for hydrogen production by electrochemically splitting water. Ni-based alloy catalysts are potential candidates for the hydrogen evolution reaction (HER) and have been studied extensively. Here, we synthesized novel hollow core-shell structure Ni-Sn@C nanoparticles (NPs) by sol-gel, chemical vapor deposition, and etching processes. The prepared electrocatalysts with porous hollow carbon layers have a high conductivity and large active area, which exhibit good electrocatalytic activity toward HER. The Tafel slope of ∼35 millivolts per decade measured in acidic solution for Ni-Sn@C NPs is the smallest one to date for the Ni-Sn alloy catalysts, and exceeds those of the most non-noble metal catalysts, indicating a possible Volmer-Heyrovsky reaction mechanism. The synthetic method can be extended to prepare other hollow core-shell structure electrocatalysts for low-temperature fuel cells.

A micro/nanofluidic enrichment device combined with the Förster resonance energy transfer (FRET) technique has been developed for sensitive detection of trace quantities of protein. In this approach, sample protein is first adsorbed on gold nanoparticles (AuNPs) to occupy part of the AuNP surface. Then, dye-labeled protein is added, which adsorbs to the residual active sites of the AuNP surface, saturating the AuNP surface with protein molecules. The unadsorbed dye-labeled protein remains in a free state in the system. Keeping a fixed amount of dye-labeled protein, a high concentration of sample protein leads to more free dye-labeled protein molecules remaining in the system, and thus a larger photoluminescence signal. Under the action of an electric field, the free dye-labeled protein molecules can be efficiently enriched in front of the nanochannel of a micro/nanofluidic chip, which greatly amplifies the magnitude of the photoluminescence and improves the detection sensitivity. As a demonstration, bovine serum albumin (BSA) and fluorescein isothiocyanate-labeled dog serum albumin (FITC-DSA) are used as sample and fluorescent proteins, respectively. Using the proposed strategy, a detection limit of BSA as low as 2.5 pg/mL can be achieved, which is more than 10(3) times lower than the reported minimums in most sensitive commercial protein quantification methods.

We propose a novel method to obtain versatile droplets arrays on a regional hydrophilic chip that is fabricated by PDMS soft lithography and regional plasma treatment. It enables rapid liquid dispensation and droplets array formation just making the chip surface in contact with solution. By combining this chip with a special Christmas Tree structure, the droplets array with concentrations in gradient is generated. It possesses the greatly improved performance of convenience and versatility in bioscreening and biosensing. For example, high throughput condition screening of toxic tests of CdSe quantum dots on HL-60 cells are conducted and cell death rates are successfully counted quickly and efficiently. Furthermore, a rapid biosensing approach for cancer biomarkers carcinoma embryonic antigen (CEA) is developed via magnetic beads (MBs)-based sandwich immunoassay methods.

We present a facilely prepared graphene oxide (GO)/ poly(dimethylsiloxane) (PDMS) composite by dispersing nanosized GO in PDMS. On the basis of the combination of photothermal effects of GO and grafted thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), an optical-driving approach for remote control of localized wettability is realized. And this method has been successfully applied in the spatially controlled reversible protein adsorption in microfluidic devices.

In this paper, we present a simple method to fabricate gold film patterns and PDMS patterns by air plasma assisting microcontact deprinting and printing transfer approaches. Chemical gold plating is employed instead of conventional metal evaporation or sputtering to obtain perfect gold film both on flat and topographic PDMS chips, and complicated SAM precoating is replaced by simple air plasma treatment to activate both the surface of gold film and PDMS. In this way, large area patterns of conductive gold film and PDMS patterns could be easily obtained on the elastomeric PDMS substrate. Both the chemical plating gold film and transferred gold film were of good electrochemical properties and similar hydrophilicity with smooth and conductive surface, which made it potentially useful in microfluidic devices and electronics. The gold transfer mechanism is discussed in detail. For typical applications, a cell patterning chip based on the gold pattern was developed to imply the interfacial property, and dielectrophoresis control of live cells was carried out with the patterned gold as interdigital electrodes to show the conductivity.