DNA-mediated construction of hollow upconversion nanoparticles for protein harvesting and near-infrared light triggered release

A simple DNA-mediated solvothermal method has been developed for the construction of well-defined hollow UNPs that can be used for a new paradigm to realize NIR light-controlled non-invasive protein release. In vitro studies show that the UNPs are capable of the transportation of enzyme into living cells. Intracellular NIR triggers the release of enzymes with high spatial and temporal precision and the released enzyme also retains its biological activity.

Catalytically active nanomaterials: a promising candidate for artificial enzymes

Natural enzymes, exquisite biocatalysts mediating every biological process in living organisms, are able to accelerate the rate of chemical reactions up to 10(19) times for specific substrates and reactions. However, the practical application of enzymes is often hampered by their intrinsic drawbacks, such as low operational stability, sensitivity of catalytic activity to environmental conditions, and high costs in preparation and purification. Therefore, the discovery and development of artificial enzymes is highly desired. Recently, the merging of nanotechnology with biology has ignited extensive research efforts for designing functional nanomaterials that exhibit various properties intrinsic to enzymes. As a promising candidate for artificial enzymes, catalytically active nanomaterials (nanozymes) show several advantages over natural enzymes, such as controlled synthesis in low cost, tunability in catalytic activities, as well as high stability against stringent conditions. In this Account, we focus on our recent progress in exploring and constructing such nanoparticulate artificial enzymes, including graphene oxide, graphene-hemin nanocomposites, carbon nanotubes, carbon nanodots, mesoporous silica-encapsulated gold nanoparticles, gold nanoclusters, and nanoceria. According to their structural characteristics, these enzyme mimics are categorized into three classes: carbon-, metal-, and metal-oxide-based nanomaterials. We aim to highlight the important role of catalytic nanomaterials in the fields of biomimetics. First, we provide a practical introduction to the identification of these nanozymes, the source of the enzyme-like activities, and the enhancement of activities via rational design and engineering. Then we briefly describe new or enhanced applications of certain nanozymes in biomedical diagnosis, environmental monitoring, and therapeutics. For instance, we have successfully used these biomimetic catalysts as colorimetric probes for the detection of cancer cells, nucleic acids, proteins, metal ions, and other small molecules. In addition, we also introduce three exciting advances in the use of efficient modulators on artificial enzyme systems to improve the catalytic performance of existing nanozymes. For example, we report that graphene oxide could serve as a modulator to greatly improve the catalytic activity of lysozyme-stabilized gold nanoclusters at neutral pH, which will have great potential for applications in biological systems. We show that, through the incorporation of modulator into artificial enzymes, we can offer a facile but highly effective way to improve their overall catalytic performance or realize the catalytic reactions that were not possible in the past. We expect that nanozymes with unique properties and functions will attract increasing research interest and lead to new opportunities in various fields of research.

Graphene-mesoporous silica-dispersed palladium nanoparticles-based probe carrier platform for electrocatalytic sensing of telomerase activity at less than single-cell level

Human telomerase is a specialized ribonucleoprotein polymerase and is used as a clinical cancer marker and special target for chemotherapy. Traditional telomerase detection uses "telomerase repeat amplification protocol" (TRAP) assay. However, TRAP is questioned because it requires use of DNA polymerases, which is susceptible to polymerase chain reaction (PCR)-derived artifacts and time-consuming. Here, a novel PCR-free, electrocatalytic assay for signal-amplified detection of telomerase activity using graphene-mesoporous silica-dispersed palladium nanoparticles-based probe carrier platform to improve probe-target recognition is reported. The low background noise is achieved by using DNA site-specific cleavage endonuclease and the detection signal is amplified by using hemoglobin. As a highly efficient electron sink, hemoglobin does not carry out direct reduction at the surface, minimizing false positives. These merits make this assay highly sensitive, achieving the sensitivity comparable to TRAP. The developed electrocatalysis assay is PCR-free, simple in design, and fast in operation, therefore avoiding PCR amplification-related errors, which make it more reliable to evaluate telomerase activity for clinical use.

Near-infrared light-triggered drug-delivery vehicle for mitochondria-targeted chemo-photothermal therapy

A novel drug-delivery vehicle for mitochondria-targeted chemo-photothermal therapy was demonstrated. A cytochrome c-specific binding aptamer was employed to make the mesoporous silica-encapsulated gold nanorods efficiently accumulate in the mitochondria of cancer cells. This nanocarrier can load various hydrophobic therapeutic agents acting on mitochondria to enhance the therapeutic efficiency and simultaneously depress the toxic side effects. In addition, near-IR treatment could induce cytochrome c release and initiation of the mitochondrial pathway of apoptosis. Importantly, this multifunctional platform could integrate targeting, light-triggered release, and chemo-photothermal therapy into one system. We hope that such a system could open the door to the fabrication of a multifunctional mitochondria-targeted drug-delivery vehicle for cancer therapy.

Graphene platform used for electrochemically discriminating DNA triplex

Triplex DNA has received great attention as new molecular biology tools and therapeutic agents due to their possible novel functions in biology systems. Therefore, it is important to distinguish triplex from among different forms of DNA, such as single-stranded and double-stranded DNA. In this report, several electrochemical techniques, cyclic voltammetry, electrochemical impedance spectroscopy, different pulse voltammetry, and electrochemiluminescence were used for distinguishing this unique structure among different DNA formations by using functionalized graphene/Nafion-Ru(bpy)3(2+) (bpy = 2, 2'-bipyridine) modified glass carbon electrode. The different interactions between nucleotides and graphene surface and Ru(bpy)3(2+) mediated guanine oxidation produced quite different electrochemical responses. Guanine bases are hidden inside the folded triplex DNAs, which are much less susceptible to be oxidized by Ru(bpy)3(3+) produced on electrodes. Furthermore, the effect of guanine bases stacking in triplex also influences the electrochemical behaviors. By changing the different position and distance of guanine bases in DNA sequences, we found that the conjoint way of several guanines strongly influenced the catalytic electrochemical responses on graphene surface. Our results provide new insight into determination of less stable protonated triplex formation by using graphene-based rapid, low-cost and sensitive electrochemical techniques.

Transition-metal-substituted polyoxometalate derivatives as functional anti-amyloid agents for Alzheimer's disease

Inhibitions of amyloid β (Aβ) aggregation and Aβ-haem peroxidase-like activity have received much attention because these two symptoms can be the primary targets of therapeutic strategies for Alzheimer's disease (AD). Recently, our group found that polyoxometalate (POM) with a Wells-Dawson structure can efficiently inhibit Aβ aggregation. However, the interaction between POMs and Aβ is robust, but still needs to improve Aβ binding affinity. More importantly, it is unclear whether POMs can cross the blood-brain barrier and decrease Aβ-haem peroxidase-like activity. Here we show that our designed series of transition metal-functionalized POM derivatives with a defined histidine-chelated binding site have much better Aβ inhibition and peroxidase-like activity inhibition effects than the parent POM. More intriguingly, we show that these compounds can cross the blood-brain barrier and are metabolized after 48 h. Our work provides insights into the design, synthesis and screening of inorganic metal compounds as multifunctional therapeutic agents against AD.

Biocompatible and high-performance amino acids-capped MnWO4 nanocasting as a novel non-lanthanide contrast agent for X-ray computed tomography and T(1)-weighted magnetic resonance imaging

In the present work, a novel non-lanthanide dual-modality contrast agent, manganese tungstate (MnWO4), has been successfully constructed by a facile and versatile hydrothermal route. With the merits of a high atomic number and a well-positioned K-edge energy of tungsten, our well-prepared non-lanthanide nanoprobes provide a higher contrast efficacy than routine iodine-based agents in clinics. Additionally, the presence of Mn in these nanoparticles endow them with excellent T1-weighted MR imaging capabilities. As an alternative to T2-weighted MRI and CT dual-modality contrast agents, the nanoprobes can provide a positive contrast signal, which prevents confusion with the dark signals from hemorrhage and blood clots. To the best of our knowledge, this is the first report that a non-lanthanide imaging nanoprobe is applied for CT and T1-weighted MRI simultaneously. Moreover, comparing with gadolinium-based T1-weighted MRI and CT dual-modality contrast agents that were associated with nephrogenic systemic fibrosis (NSF), our contrast agents have superior biocompatibility, which is proved by a detailed study of the pharmacokinetics, biodistribution, and in vivo toxicology. Together with excellent dispersibility, high biocompatibility and superior contrast efficacy, these nanoprobes provide detailed and complementary information from dual-modality imaging over traditional single-mode imaging and bring more opportunities to the new generation of non-lanthanide nanoparticulate-based contrast agents.

Spectral measurement of electron antineutrino oscillation amplitude and frequency at Daya Bay

A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9  GW(th) reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) and the first direct measurement of the ν¯(e) mass-squared difference |Δm(ee)2|=(2.59(-0.20)(+0.19))×10(-3)  eV2 is obtained using the observed ν¯(e) rates and energy spectra in a three-neutrino framework. This value of |Δm(ee)2| is consistent with |Δm(μμ)2| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.

Lactoferrin administration into the nostril alleviates murine allergic rhinitis and its mechanisms

Lactoferrin (LF) can downregulate allergic airway inflammation in asthma. However, the in vivo effect of exogenous LF on allergic rhinitis (AR), a disease attributed to airway inflammation, has yet to be determined. We investigated the effect of intranasal administration recombinant human (rh) LF and its underlying mechanisms on AR in BALB/c mice. Multiple parameters of allergic responses were evaluated to determine the effect of rhLF. We found that the number of eosinophils and goblet cells, as well as mRNA and protein expression of type 2 helper T (Th2), Th17 and regulatory T (Treg) cells in the nasal cavity, was significantly upregulated in AR mice compared with the controls, Conversely, administration of rhLF prior to or after intranasal ovalbumin challenge markedly downregulated these same parameters. Th1-specific mRNA and protein expression in the nasal cavity of the controls was not different from that in AR mice, but expression significantly increased with rhLF treatment. The mRNA and protein expression of endogenous LF in the nasal cavity was significantly downregulated in AR mice compared with the controls. However, after rhLF treatment, endogenous LF mRNA and protein expression was significantly upregulated. Exogenous rhLF inhibited allergic inflammation in AR mice, most likely by promoting the endogenous LF expression and skewing T cells to a Th1, but not a Th2 and Th17 phenotype in the nasal mucosa. Our findings suggest that rhLF treatment may be a novel therapeutic approach for prevention and treatment AR.

Methods and preliminary measurement results of liquid Li wettability

A test of lithium wettability was performed in high vacuum (< 3 × 10(-4) Pa). High magnification images of Li droplets on stainless steel substrates were produced and processed using the MATLAB(®) program to obtain clear image edge points. In contrast to the more standard "θ/2" or polynomial fitting methods, ellipse fitting of the complete Li droplet shape resulted in reliable contact angle measurements over a wide range of contact angles. Using the ellipse fitting method, it was observed that the contact angle of a liquid Li droplet on a stainless steel substrate gradually decreased with increasing substrate temperature. The critical wetting temperature of liquid Li on stainless steel was observed to be about 290 °C.

Multiconfigurable logic gates based on fluorescence switching in adaptive coordination polymer nanoparticles

Fluorescence switching of guest molecules confined in coordination polymer nanoparticles (CPNs) generated from nucleotides and lanthanide ions are used to construct multiconfigurable logic gates. Moreover, the potential of the material as fluorescent probe with large Stokes shift is demonstrated for cellular imaging. In this work the logic gate is integrated into the therapeutic agent and this will be highly beneficial in future molecular computing.

Reduced graphene oxide upconversion nanoparticle hybrid for electrochemiluminescent sensing of a prognostic indicator in early-stage cancer

Upconversion nanoparticles (UCNPs) have been proposed as a promising new class of biological luminescent labels because of their weak auto-fluorescence background, strong penetration ability under near-infrared (NIR) radiation, resistance to photobleaching, and low toxicity. Although UCNPs hold great promise in nanotechnology and nanomedicine, their applications in ECL fields still remain unexplored. Herein, a label-free, ultra-sensitive and selective electrochemiluminescence (ECL) assay is developed for detection of cyclin A2 by using highly efficient ECL graphene-upconversion hybrid. Being an important member of the cyclin family, cyclin A2 is involved in the initiation of DNA replication, transcription and cell cycle reg-ulation through the association of cyclin-dependent kinases (CDK). Cyclin A2 is a prognostic indicator in early-stage cancers and a target for treatment of different types of cancers. However, the expression level of cyclin A2 is quite low, direct detection of cyclin A2 in crude cancer cell extracts is challenging and important for both clinical diagnosis of cancer in the early stage and the treatment. By chemically grafting cyclin A2 detection specific probe, a PEGlyted hexapeptide, to graphene-upconversion hybrid, the constructed ECL biosensor displays a superior performance for cyclin A2 , which can not only detect cyclin A2 directly in cancer cell extracts, but also discriminate between normal cells and cancer cells. More importantly, the ECL biosensor has different responses between clinical used anticancer drug-treated and non-treated cancer cells, which demonstrates that the sensor can be potentially used for drug screening, and for evaluation of therapeutic treatments in early-stage cancers.

One-step DNA-programmed growth of CpG conjugated silver nanoclusters: a potential platform for simultaneous enhanced immune response and cell imaging

We designed a one-pot synthesis that allows CpG-functionalized AgNCs to be prepared, combining attractive features of enhanced immune response and intracellular imaging.

G-Quadruplex binding enantiomers show chiral selective interactions with human telomere

Chiral recognition of DNA molecules is important because DNA chiral transition and its different conformations are involved in a series of important life events. Among them, polymorphic human telomere DNA has attracted great interests in recent years because of its important roles in chromosome structural integrity. In this report, we examine the short-term effect of chiral metallo-supramolecular complex enantiomers treatment on tumor cells, and find that a zinc-finger-like alpha helical chiral metallo-supramolecular complex, [Ni₂L₃]⁴⁺-P enantiomer (NiP), can selectively provoke the rapid telomere uncapping, trigger DNA damage responses at telomere and degradation of G-overhang and the delocalization of telomeric protein from telomeres. Further studies indicate that NiP can induce an acute cellular apoptosis and senescence in cancer cells rather than normal cells. These results are further evidenced by the upregulation of p21 and p16 proteins. Moreover, NiP can cause translocation of hTERT from nuclear to cytoplasm through Tyr 707 phosphorylation. While its enantiomer, [Ni₂L₃]⁴⁺-M (NiM), has no such mentioned effects, these results clearly demonstrate the compound’s chiral selectivity in cancer cells. Our work will shed light on design of chiral anticancer drugs targeting G-quadruplex DNA, and developing telomere and telomerase modulation agents.

One-step nucleotide-programmed growth of porous upconversion nanoparticles: application to cell labeling and drug delivery

A simple and "green" strategy has been reported for the first time to fabricate upconversion nanoparticles (UCNPs) by utilizing nucleotides as bio-templates. The influence of the functionalities present on the nucleotide on the production of nanoparticles was investigated in detail. Through the effects of nucleotides, the obtained nanoparticles possessed a porous structure. The use of the as-prepared UCNPs for cell imaging, drug delivery and versatile therapy applications were demonstrated. In view of the bright up-conversion luminescence as well as the excellent biocompatibility, and the good colloidal stability of the as-prepared UCNPs, we envision that our synthesis protocol might advance both the fields of UCNPs and biomolecule-based nanotechnology for future studies.

Polypyrrole nanoparticles as promising enzyme mimics for sensitive hydrogen peroxide detection

Polypyrrole nanoparticles possess intrinsic peroxidase-like activity, which can be employed to quantitatively monitor the H₂O₂ generated by macrophages.

Multifunctional upconverting nanoparticles for near-infrared triggered and synergistic antibacterial resistance therapy

A novel nanomaterial with CuS nanoparticles decorated onto the surface of NaYF₄:Mn/Yb/Er@photosensitizer doped SiO₂ was synthesized for synergistic multidrug-resistant bacteria therapy.

Towards intelligent bioreactor systems: triggering the release and mixing of compounds based on DNA-functionalized hybrid hydrogel

We have designed and synthesized an intelligent DNA-functionalized hydrogel bioreactor system that can be controlled by external stimuli.

Visual detection of telomerase activity with a tunable dynamic range by using a gold nanoparticle probe-based hybridization protection strategy

We developed a novel telomere complementary (TC) oligonucleotide modified AuNP probe (TC-AuNPs) for colorimetric analysis of telomerase activity. The mechanism of this method is that the telomerase reaction products (TRP), which can hybridize with the TC-AuNPs, are able to protect the AuNPs from the aggregation induced by salt. It is demonstrated that the colorimetric method enabled the analysis of the telomerase activity in 1000 HeLa cells with the naked eye, and down to 100 HeLa cells with the aid of UV-Vis spectroscopy. This strategy is not only convenient and sensitive, but also has a tunable dynamic range. The platform is also applicable for the initial screening of a telomerase inhibitor to discover new anticancer drugs.

Aptamer-directed synthesis of multifunctional lanthanide-doped porous nanoprobes for targeted imaging and drug delivery

Multifunctional lanthanide-doped porous nanoparticles are prepared via a facile one-step solvothermal route by employing aptamers as the biotemplate. The nanoparticles feature excellent aqueous dispersibility and biospecific properties and could work as effective nanoprobes for targeted imaging and drug delivery. With aptamer being in principle available for any kind of target, this synthetic strategy may open the door to a new generation of nanoprobes for bioapplications such as time-resolved biodetection, multimode bioimaging/biolabeling, and targeted cancer therapy.