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An ATP stimulus-responsive COF-based drug-delivery system was developed using tDNA as nanogates for controllable estradiol release and the treatment of myocardial ischemia and reperfusion injury.

Accurately delivering antisense oligonucleotides (ASOs) to tumor cells for gene therapy poses a significant challenge. To address this issue, we develop a NIR light-activable DNA nanodevice to target survivin mRNA and simultaneously release ASOs in tumor cells, which allows high-precision spatiotemporal imaging with high sensitivity and efficient gene therapy. The concept is based on upconversion nanoparticles, which can convert NIR light into UV emissions to activate an entropy-driven DNA walking system that further determines mRNA in tumor cells. The intramolecular toehold-mediated entropy-driven catalytic reaction generates a large amount of Bcl-2 ASOs, which allows accurate delivery of ASOs for gene therapy due to the specific targeting of mRNA in tumor cells. Both in vitro and in vivo results show that the NIR light induced-DNA nanodevice can detect mRNA with high sensitivity by DNA walking amplification system and high precision in gene delivery. Moreover, the released ASOs from DNA walking system deregulate the expression of Bcl-2 anti-apoptosis protein and induce tumor cell apoptosis, thereby suppressing tumor growth without a transfection reagent. The NIR-light-controlled DNA nanodevice holds great potential for precise gene therapy in clinical applications.

Small extracellular vesicles (sEVs) have attracted wide attention as a promising tumor biomarker. However, sensitive and selective detection of sEVs is challenging due to the low levels of sEVs in the early stage of cancers. Herein, a novel fluorescent sensor was developed for the detection of sEVs with high sensitivity and selectivity based on nonlinear hybridization chain reaction (nHCR) signal amplification and immunomagnetic separation. Firstly, sEVs were captured and enriched by CD63 antibody conjugated magnetic beads

A novel sp2c-COF was synthesized via the Knoevenagel condensation reaction, which exhibited excellent stability and strong fluorescence. And the sp2c-COF was further used for selective Fe3+ sensing.

As two main types of liquid biopsy markers, both circulating tumor cells (CTCs) and small extracellular vesicles (sEVs) play important roles in the diagnosis and prognosis of cancers. CTCs are malignant cells that detach from the original tumor tissue and enter the circulation of body fluids. sEVs are nanoscale vesicles secreted by normal cells or pathological cells. However, CTCs and sEVs in body fluids are scarce, leading to great difficulties in the accurate analysis of related diseases. For the sensitive detection of CTCs and sEVs in body fluids, various types of nucleic acid and nanomaterial-assisted signal amplification strategies have been developed. In this review, we summarize the recent advances in fluorescent detection of CTCs and sEVs in liquid biopsy based on nucleic acid and nanomaterial-assisted signal amplification strategies. We also discuss their advantages, challenges, and future prospects.

Distinguishing between normal, inflammatory, and progressing tumor cells plays a vital role in early diagnoses and clinical studies. The simultaneous quantification of multiple biomarkers in cells can reveal cellular heterogeneity, which contributes to the discrimination of different types of cells. Herein, a dual-channel fluorescent probe has been developed for monitoring peroxynitrite (ONOO

Precise modulation of pH in living cells plays a vital role in the study of many diseases, such as cancer and rheumatoid arthritis. Here, a series of imine-linked covalent organic frameworks (COFs) were rationally designed and developed for pH sensing in tumor cells and zebrafish. Four monomers were chosen to synthesize COFs (COF1-COF4) with different pKa by a simple orthogonal combination through condensation reaction. The as-obtained COFs exhibited a sensitive pH-dependent fluorescence response compared to their building blocks. Among them, COF2 possessed a high crystallinity, excellent fluorescence, and suitable pKa for biosensing. For bioimaging applications, COF2 was modified with poly-d-lysine (PDL) to improve its biocompatibility and endocytosis efficiency. After that, PDL-modified COF2 (PDL@COF2) was used as a novel fluorescence probe with a superior linear pH response over the range from 5.0 to 8.0 due to its fully reversible protonation and deprotonation. The fluorescent PDL@COF2 was further employed as a good candidate for pH imaging in tumor cells and zebrafish. The as-constructed environment-sensitive fluorescent COFs have greatly expanded the applications of COFs in the biological area.

As a powerful signal amplification tool, the DNA walker has been widely applied to detect rare microRNA (miRNA) in vivo. Despite the significant advances, a near-infrared (NIR) light controllable DNA walker for signal amplification powered by an endogenous initiator has not been realized, which is crucial for spatiotemporal imaging of miRNA in living cells with high sensitivity. Herein, we constructed a NIR-photoactivatable DNA walker system, which was powered by endogenous adenosine triphosphate (ATP) for in situ miRNA imaging with spatial and temporal resolution. The system was very stable with an extremely low fluorescent background for the bioimaging in living cells. We employed upconversion nanoparticles (UCNPs) as the carriers of the DNA probe and transducers of converting NIR to UV light. Coupled with the DNA walker fueled by intracellular ATP, a smart system based on the NIR light initiated DNA walker was successfully developed for precise spatiotemporal control in living cells. Triggered by NIR light, the DNA walker could autonomously and progressively travel along the track with the assistance of intracellular ATP. The system has been successfully applied for in situ miRNA imaging in different cell lines with highly spatial and temporal resolution. This strategy can expand NIR photocontrol the DNA walker for precise imaging in a biological system.

Manipulating cell-cell interactions is of great significance in cell communication and cell-based therapies. Although efforts have been made to construct cell-cell assembly by stimuli-responsive host-guest interactions, controllable cell-cell interactions by near-infrared (NIR) light triggered reversible assembly remain a challenge. Herein, we develop a NIR-controlled system based on β-cyclodextrin (β-CD) modified upconversion nanoparticles (UCNPs) for reversible and noninvasive manipulation of cell assembly and disassembly, which is realized by host-guest interactions between

Calcium and chloride levels are closely related to lysosome dysfunction. However, the simultaneous measurement of calcium (Ca

A new coordination polymer (Ce-Fe-GMP) with excellent catalytic activity was prepared by a facile route, which was further applied to the detection of F

The efficient capture and sensitive detection of circulating tumor cells (CTCs) play a vital role in cancer diagnosis and prognosis. However, CTCs in the peripheral blood are very rare and heterogeneous, which make them difficult to isolate and detect. Herein, a novel colorimetric nanobioplatform was successfully developed for the highly efficient capture and highly sensitive detection of heterogeneous CTCs, which consisted of two parts: the multivalent aptamer-modified gold nanoparticles as the capture unit and two kinds of aptamer-functionalized pH-sensitive allochroic dyes (thymolphthalein and curcumin) @ molybdenum disulfide nanoflakes (MoS2 NFs) acting as the visual simultaneous detection of heterogeneous CTCs. Using MCF-7 and HeLa cells as the CTC models, the capture unit can effectively isolate the CTCs due to the multivalent probe with improved affinity. The two allochroic dyes can display obvious color changes under alkaline conditions (pH 12.5) in the presence of MCF-7 and HeLa cells, which provided a rapid and sensitive strategy for visualizing simultaneous detection of heterogeneous CTCs as low as 5 cells mL-1. This nanoplatform possessed a high sensitivity toward CTC detection owing to high dye loading capacity of MoS2 NFs and allochroic dyes with excellent pH sensitivity. It can successfully distinguish and quantitatively detect the targeted heterogeneous CTCs from numerous interfering cells in diluted whole blood. It can also be used to detect CTCs from lysed blood samples from cancer patients, indicating promising application for cancer diagnosis.

Myeloperoxidase (MPO) is a heme peroxidases protein associated with many inflammation-related diseases. Although many fluorescent probes have been constructed for the assessment of MPO activity, it still remains a challege to develop a nanoprobe for highly sensitive biosensing and high-resolution bioimaging in biological system. In this work, we developed a novel luminescent nanoprobe based on upconversion nanoparticles (UCNPs) conjugated with phycocyanin (PC), which could detect the fluctuation of MPO. By grafting PC onto the surface of UCNPs through amidation reaction, the luminescence of UCNPs is quenched by PC via energy transfer. Due to the specific recognition by PC, the nanoprobe can be used for sensitive evaluation the bioactivity of MPO. The nanoprobe based on PC-UCNPs has been successfully applied for the bioimaging of MPO in living cells and an inflammatory process by taking an acute liver injury mouse as a model.

The integrative bioplatform for capture, detection and release of circulating tumor cells (CTCs) is of great significance in clinical diagnosis and biomedical research. To fulfill this demand, we i...

Small extracellular vesicles (sEVs), often known as exosomes, are expected to be a promising biomarker for the early diagnosis of cancer because they carry enriched proteins that originated from parent cells. Profiling surface proteins of sEVs offers non-invasive access for the early diagnosis of cancer. However, it remains challenging to simultaneously detect surface proteins of sEVs with desired sensitivity. Herein, a dual color DNA nanodevice based on toehold-mediated DNA strand displacement signal amplification and the synchronous fluorescence technique has been developed for simultaneous analysis of surface proteins of sEVs with high sensitivity. As for the DNA nanodevice-based system, the nanoconjugates of aptamer-magnetic beads can recognize surface proteins of sEVs and lead to the release of single-stranded DNA. Then, the released DNA can trigger toehold-mediated DNA strand displacement for signal amplification. In this system, a CD63 aptamer and MUC1 aptamer were used as recognition elements for the detection of surface proteins of sEVs isolated from cancer cells. Under the optimal conditions, the corresponding proteins of sEVs were simultaneously determined with ultrasensitivity by the synchronous fluorescence method. Also, the detection limits of sEVs by two surface proteins were 67 particles/μL by CD63 and 37 particles/μL by MUC1. Of note, the as-constructed method can be applied to recognize sEVs from different tumor cell lines (SGC7901, HepG2, and MCF-7 cells). Furthermore, the system has been successfully applied to precisely identify cancer patients from healthy people by serum analysis. The strategy demonstrates great potential applications in the early diagnosis of cancer.

Herein, a ratiometric fluorescent method was developed for alkaline phosphatase (ALP) detection based on near-infrared (NIR) Ag2S quantum dots (QDs) and calcein through the competitive approach. The system based on Ag2S QDs and calcein shows green (maximum emission at 512 nm from calcein) and near infrared (NIR) fluorescence (maximum 798 nm from Ag2S QDs) under the same excitation wavelength (468 nm). In the presence of Ce3+, the fluorescence intensity of calcein is decreased due to static quenching, while the fluorescence intensity of Ag2S QDs is enhanced through aggregation induced emission (AIE). The p-nitrophenyl phosphate is hydrolyzed by ALP, and the yield phosphate ions bind with Ce3+ with higher affinity than these of Ag2S QDs and calcein. Therefore, the green fluorescence from calcein is recovered while NIR fluorescence from Ag2S QDs is decreased. On the basis of these findings, a ratiometric fluorescence assay was developed for the measurement of ALP activity. The ratio of fluorescence intensity at 512 and 798 nm (F512/F798) was well associated with the ALP concentration ranging from 2 to 100 mU/mL with the detection limit of 1.28 mU/mL. The method was successfully applied for detecting ALP in human serum with an acceptable recovery and bioimaging intracellular ALP with good performance. In addition, the approach was also employed for the screening ALP inhibitor.

A luminescence resonance energy transfer (LRET) system was successfully developed using near-infrared (NIR) Ag2S nanodots (NDs) as the energy acceptors and upconversion nanoparticles (UCNPs) as the energy donors. The system possessing the properties of NIR excitation (980 nm) and NIR emission (795 nm) was used for the ratiometric detection and bioimaging of pH in tumor cells and zebrafish. Glutathione and mercaptopropionic acid (MPA) co-modified Ag2S NDs (GM-Ag2S NDs) were prepared by ligand exchange with an excellent pH-responsive property over a pH range of 4.0 to 9.0. The NIR GM-Ag2S NDs were covalently grafted with silica coated UCNPs, and an efficient LRET platform was developed via modulation of the thickness of the silica coating. Due to the LRET process between UCNPs and GM-Ag2S NDs, a ratiometric luminescence nanoprobe with the properties of NIR excitation-NIR emission was constructed for pH biosensing and bioimaging. On the basis of high contrast bioimaging, the nanoplatform can distinguish between tumor and normal tissue in the zebrafish model.

Elevated hydrogen sulfide (H2S) level is closely associated with various diseases. So the sensing of H2S is noteworthy for divulging its role in diagnosing these diseases. Herein, we proposed poly(acrylic acid)-modified upconversion nanoparticles assembled with cationic near-infrared cyanine chromophores (Cy7-Cl) as the nanoprobe (Cy7-UCNPs) for monitoring H2S based on thiolation reactions. The presence of H2S resulted into about five-fold enhancement in the luminescence intensity of Cy7-UCNPs and the nanoprobe showed a good linearity (R2 =0.9952) over the range of 1.0 − 90 μM. Furthermore, Cy7-UCNPs were successfully employed in sensing and imaging of exogenous and endogenous H2S in live cells and zebrafish. The system shows great potential in the field of nanobiomedicine because of the many excellent properties including high sensitivity, good selectivity, and low cytotoxicity.

A luminescent terbium metal–organic framework (Tb-MOF) was prepared using Tb3+ as metal ions and a boronic acid ligand (3,5-dicarboxybenzeneboronic acid) as linkers, which was successfully employed for the detection and scavenging of reactive oxygen species (ROS) in living cells. After the formation of the Tb-MOF, the luminescence of Tb3+ is sensitized by the organic linkers. In addition, the functionalization of boronic acid groups in the channels of MOFs also enhances the luminescence of Tb3+ ions through the antenna effect by adjusting the energy level of the ligand. In addition, the free boronic acid groups act as active sites and react with ROS due to a rapid nucleophilic addition reaction, which leads to the luminescence quenching of Tb-MOF. On the basis of these findings, the boronic acid-functionalized Tb-MOF can be used as an excellent ROS scavenger and a nanoprobe for highly selective and sensitive detection of ROS in living cells.

Nanoassemblies for bioimaging in living cells have attracted much attention. In this work, an efficient and sensitive turn-on fluorescent detection platform for reactive oxygen species (ROS) in living cells has been constructed using the nanoassemblies of upconversion nanoparticles (UCNPs)-MoS2 nanoflakes. In this nanostructure, the positively charged UCNPs could assemble with negatively charged poly(acrylic acid) modified MoS2 nanoflakes by electrostatic force, which led to the remarkable fluorescence quenching of UCNPs owing to the excellent quenching ability of MoS2 nanoflakes. In contrast, in the presence of ROS, the fluorescence recovery of UCNPs is successfully realized owing to the decomposition of MoS2 nanoflakes through the chemical reaction with ROS. The ROS-mediated disassembly of the nanoarchitecture display excellent fluorescent response toward ROS. Furthermore, the disassembly of UCNPs-MoS2 nanoflakes has been successfully used for ROS bioimaging in cells and zebrafish.

Two-photon fluorescent (TPF) molybdenum disulfide quantum dots (MoS

The unique electronic, physical and chemical properties of nanostructured transition metal dichalcogenide (TMD) materials have received great attention, specifically, with the decrease of size to several nanometers, particles named TMD quantum dots (QDs). The inherent properties of TMD QDs make them promising for a variety of applications, including catalytic, luminescence and biomedical. In this review, we first briefly introduce the controlled synthesis of TMD QDs using mechanical exfoliation, ion intercalation-assisted liquid exfoliation, free radical and electrochemical shear and hydrothermal/solvothermal reaction. We then summarize recent progress on chemical and biological applications of TMD QDs in detail.

The level of circulating tumor cells (CTCs) plays a critical role in tumor metastasis and personalized therapy, but it is challenging for highly efficient capture and detection of CTCs because of the extremely low concentration in peripheral blood. Herein, we report near-infrared fluorescent Ag2S nanodot-based signal amplification combing with immune-magnetic spheres (IMNs) for highly efficient magnetic capture and ultrasensitive fluorescence labeling of CTCs. The near-infrared fluorescent Ag2S nanoprobe has been successfully constructed through hybridization chain reactions using aptamer-modified Ag2S nanodots, which can extremely improve the imaging sensitivity and reduce background signal of blood samples. Moreover, the antiepithelial-cell-adhesion-molecule (EpCAM) antibody-labeled magnetic nanospheres have been used for highly capture rare tumor cells in whole blood. The near-infrared nanoprobe with signal amplification and IMNs platform exhibits excellent performance in efficient capture and detectio...

Pt nanoparticle (Pt NP)@UiO-66-NH2 composites were synthesized and encompassed the benefits of permanent porosity, high thermal and chemical stability of metal–organic frameworks (MOFs), together with the functional behavior of isolated Pt NPs. The PVP-stabilized Pt NPs with the average diameter of 2.48 nm were well dispersed and confined within the framework of UiO-66-NH2. Pt NPs possess highly peroxidase-like activities and make the composites oxidize 3,3′,5,5′-tetramethylbenzidine in the presence of H2O2. Moreover, the specific interaction between Hg2+ and Pt NPs leads to the effective suppression of the peroxidase-like activity of Pt NP@UiO-66-NH2, which endows excellent selectivity for Hg2+ measurement over the interfering metal ions. Based on the colorimetric sensing system, Hg2+ is linearly measured over the range from 0 to 10 nM with a detection limit of 0.35 nM. Moreover, the as-obtained Pt NP@UiO-66-NH2 nanocomposites exhibit high capacity and good selectivity for Hg2+ adsorption, which is succe...

In this work, a fast, sensitive and label-free fluorescence sensing platform for evaluating the acetylcholinesterase (AChE) activity was developed based on the inner filter effect (IFE) between black phosphorus quantum dots (BP QDs) and 2-nitro-5-thiobenzoate anion (TNB). BP QDs were successfully synthesized from bulk BP through a facile top-down route by sonication-assisted solvothermal method. The as-prepared QDs exhibit green fluorescence with a relative high quantum yield, good photostability and relative pH resistance. 5,5′-Dithiobis-(2-nitrobenzoic acid) (DTNB), as a well-known Ellman’s reagent, can react with thiol groups to form TNB. Based on the IFE between BP QDs and TNB, a sensitive and label-free sensing platform was developed for fluorescent measurement of thiols. As a proof-of-concept application, the platform was further applied in the evaluation of AChE activity by using acetylthiocholine as the substrate.

An efficient near-infrared fluorescence probe has been developed for the sequential detection of Cu2+, pyrophosphate (P2O74-, PPi), and alkaline phosphatase (ALP), which is based on the "off-on-off" fluorescence switch of branched polyethyleneimine (PEI)-capped NaGdF4:Yb/Tm upconversion nanoparticles (UCNPs). The fluorescence is quenched via energy transfer from UCNPs to Cu2+ for the coordination of PEI with Cu2+. The strong affinity between Cu2+ and PPi leads to the formation of Cu2+-PPi complex and results in the detachment of Cu2+ from the surface of UCNPs, thus the fluorescence is triggered on. ALP-directed hydrolysis of PPi causes the disassembly of Cu2+-PPi complex and re-conjugation between Cu2+ with PEI, which leads to the switch-off fluorescence of UCNPs. The system allows sequential analysis of Cu2+, PPi, and ALP by modulating the switch of the fluorescence of UCNPs with detection limits of 57.8nM, 184nM, and 0.019U/mL for Cu2+, PPi, and ALP, respectively. By virtue of the NIR feature and excellent biocompatibility, the UCNPs-based probes are suitable for bioimaging. Taking Cu2+ visualization as a model, the nanoprobes have been successfully applied for intracellular imaging of Cu2+ in living cells.

In this work, a novel phenomenon was discovered that the fluorescence intensity of silver sulfide quantum dots (Ag2S QDs) could be enhanced in the presence of rare earth ions through aggregation-induced emission (AIE). Based on the strong coordination between rare earth ions and F−, a facile and label-free strategy was developed for the detection of F− in living cells. Ag2S QDs were synthesized using 3-mercaptopropionic acid as sulfur source and stabilizer in aqueous solution. The near infrared (NIR) emitting QDs exhibited excellent photostalilty, high quantum yield and low toxic. Interestingly, the fluorescence intensity of QDs was obviously enhanced upon the addition of various rare earth ions, especially in the presence of Gd3+. The AIE mechanism was proved via the TEM, zeta potential and dynamic light scattering analysis. Moreover, the coordination between rare earth ions and F− could lead to the quenching of fluorescence QDs due to the weakening the AIE. Based on these findings, we developed a highly sensitive and selective method for detection of F−. The label-free NIR fluorescence probe was successfully used for F− bioimaging in live cells.

A luminescence resonance energy transfer (LRET) system was successfully developed using near-infrared (NIR) Ag

Nanoscale metal-organic frameworks (NMOFs) have been widely employed in biological diagnosis and treatment system. In this work, glutathione stabilized gold nanoclusters (GSH-AuNCs) were successfully encapsulated in NMOFs and the as-obtained nanocomposites (named as AuNCs@NMOFs) showed nearly 10 times enhancement in fluorescence intensity and longer fluorescence lifetime relative to GSH-AuNCs. In addition, the fluorescence intensity of AuNCs@NMOFs was quenched by highly reactive oxygen species (hROS) due to their strong oxidation ability. Based on the fact, the nanocomposites were used for the detection of hROS with a linear range from 80 nM to 1.0 μM toward hypochlorite (as the representative of hROS). The limit of detection (LOD) was about 30 nM, which was about 30 times lower than that of GSH-AuNCs (LOD = 0.96 μM). With the features of good biocompatibility, excellent luminescence and efficient cellular uptake, AuNCs@NMOFs were successfully applied in fluorescence imaging of hROS in living cells.

Herein, a ratiometric fluorescent method was developed for alkaline phosphatase (ALP) detection based on near-infrared (NIR) Ag

Fluoride ion (F−) is an essential micronutrient in the human body, however, an abnormal large intake of F− can result in adverse effects, such as skeletal fluorosis or DNA damage. Therefore, it is of great significance to develop convenient assays for the visual detection of F− with high sensitivity. We rationally developed the nanosized iron-based metal organic frameworks (Fe-MOFs) by using 3,5-dicarboxybenzeneboronic acid as organic linkers and Fe3+ as metal ions through the solvothermal method, which can be applied for detecting F− with high sensitivity and selectivity owing to the specific recognition of boronic acid groups towards F− and the strong binding affinity between F− and Fe3+. The Fe-MOFs possess excellent peroxidase-like activity, which can be effectively inhibited by F−. Moreover, a portable test kit for the determination of F− was developed by embedding Fe-MOFs into hydrogel, and the visual measurement of F− was realized based on smartphone by identifying the color signal of the oxidation of 3,3',5,5'-tetramethylbenzidine dihydrochloride. The output signal (R/G) was linear with F− concentration in the range of 10.0–200.0 μM. The Fe-MOFs-based colorimetric strategy is easy-operation, low-cost and equipment-free, which has been further applied to detect F− in the real water samples.

A facile and eco-friendly approach for the synthesis of water-soluble WS2 quantum dots (QDs) was developed via ultrasonication and a hydrothermal process from bulk WS2. In this strategy, the dispersity of bulk WS2 in aqueous phase was improved with the aid of a surfactant (hexadecyltrimethylammonium bromide, CTAB), which could shorten the exfoliation time and improve the exfoliation efficiency to form layered WS2 nanosheets. Through hydrothermal treatment, the nanosheets were further scissored into QDs with high quality. The QDs show excellent features with narrow size distribution, good water solubility, and stable fluorescence. We find that the fluorescence of WS2 QDs can be quenched by Fe3+ through photoinduced electron transfer, and a wide detection linear range for Fe3+ is acquired. It indicates that WS2 QD can be used as a “turn-off” probe for Fe3+. In the presence of lipoic acid (LA), the fluorescence was recovered due to the stronger interaction between LA and Fe3+ than WS2 QDs. A “turn-on” sensor...

The development of highly sensitive and selective methods for the detection of lead ion (Pb(2+)) is of great scientific importance. In this work, we develop a new surface-enhanced Raman scattering (SERS)-based sensor for the selective trace measurement of Pb(2+). The SERS-based sensor is assembled from gold nanoparticles (AuNPs) and graphene using cucurbit[7]uril (CB[7]) as a precise molecular glue and a local SERS reporter. Upon the addition of Pb(2+), CB[7] forms stronger complexes with Pb(2+) and desorbs from AuNPs, resulting in a sensitive "turn-off" of SERS signals. This SERS-based assay shows a limit of detection (LOD) of 0.3 nm and a linear detection range from 1 nm to 0.3 μm for Pb(2+). The feasibility of the assay is further demonstrated by probing Pb(2+) in real water samples. This SERS-based analytical method is highly sensitive and selective, and therefore holds promising applications in environmental analysis.

As a newly developed fluorescent probe, DNA functionalized quantum dots (QDs) with unique optical properties play a critical role in the bioanalytical applications. The present review provides an overview on the conjugation technologies of DNA to QDs, including electrostatic attraction, covalent attachment, specific effect and direct synthesis. In addition, we summarize recent advances on DNA functionalized QDs in the bioapplications, such as targeting nucleic acids, ions, small molecules and the protein detection, cell imaging and disease diagnosis. Finally, we envision aspects concerning current challenges on the DNA functionalized fluorescent QDs.

In this paper, a facile and simple strategy was developed for in-situ growth cerium oxide nanoparticles on reduced graphene oxide (rGO) through thermal treatment of the Ce 3+ -doped graphene oxide(GO) under nitrogen atmosphere. Through regulation the thermal treatment temperature, the growth of cerium oxide nanocrystals can be easily controlled in accompany with the reduction of GO. The morphology and chemical composition of the as-synthesized CeO 2 /rGO at different temperature are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The nanocomposites show electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline solution. Especially, the cerium oxide nanoparticles/rGO nanocomposites treated at 750 °C possess excellent electrocatalytic ability with a dominating four-electron pathway, high tolerance of methanol and long-term operation stability due to the well exfoliation of graphene and perfect crystalline structure of cerium oxide. Compared to the commercial Pt/C catalyst, the synergistic effect of the fast electron transport of rGO and the high electrocatalytic activity of cerium oxide nanocrystals makes the nanocomposites as advanced, non-precious electrocatalysts for ORR.

Two-photon fluorescent (TPF) molybdenum disulfide quantum dots (MoS2 QDs) were synthesized through a facile and one-step solvothermal approach. The MoS2 QDs exhibit small size and high stability. Because of their low toxicity and TPF ability, the MoS2 QDs are successfully applied in two-photon fluorescence bio-imaging.

Greigite magnetic nanoparticles (Fe3S4-MNPs) were prepared and reveal a peroxidase-like activity. Kinetic studies revealed a pseudo-enzymatic activity that is much higher than that of other magnetic nanomaterial-based enzyme mimetics. This finding was exploited to design a photometric enzymatic glucose assay based on the formation of H2O2 during enzymatic oxidation of glucose by glucose oxidase, and the formation of a blue product from an enzyme substrate that is catalytically oxidized by H2O2 in the presence of Fe3S4-MNPs. Glucose can be detected in the 2 to 100 μM concentration range, and the low detection limit is 0.16 μM. The method was applied to quantify glucose in human serum. In our perception, this enzyme mimetic has a large potential in that it may be used in other oxidase based assays, but also in ELISAs.

As an important biomarker, cytochrome c (Cyt c) plays a crucial role in mitochondrial electron transport chain and cell apoptosis. Herein, a label-free near-infrared (NIR) Ag

Elevated hydrogen sulfide (H

The level of circulating tumor cells (CTCs) plays a critical role in tumor metastasis and personalized therapy, but it is challenging for highly efficient capture and detection of CTCs because of the extremely low concentration in peripheral blood. Herein, we report near-infrared fluorescent Ag

The authors describe an environmentally friendly and fast (~14 min) method for the synthesis of homogeneously distributed fluorescent polydopamine nanodots (PDA-NDs) using KMnO4 as the oxidant. Alkaline phosphatase (ALP) catalyzes the hydrolysis of ascorbic acid 2-phosphate to release free ascorbic acid which undergoes an in-situ redox reaction with KMnO4. Depending on the activity of ALP, more or less KMnO4 is consumed, and this affects the formation of the PDA-NDs. Based on this finding, a sensitive method was worked out to quantify the activity of ALP via real-time formation of fluorescent PDA-NDs. The fluorometric signal (best measured at excitation/emission peaks of 390/500 nm) is linear in the 1 to 50 mU·mL−1 ALP activity range, and the limit of the detection is as low as 0.94 mU·mL−1 (based on 3 σ/m). The method was successfully applied to the determination of ALP activity in spiked human serum and in MCF-7 cell lysates. It was also applied in a method to screen for inhibitors of ALP.

A simple yet effective strategy was developed to generate a non-precious oxygen electrode electrocatalyst of MoS2/nitrogen-doped graphene (NG) by physical mixing MoS2 sheets with NG. The micrometer-sized MoS2 sheets were obtained through ultrasonication exfoliation of the bulk MoS2, only showing little oxygen reduction reaction (ORR) activity. MoS2/NG hybrid was obtained by loading MoS2 sheets onto NG through ultrasonication, and the resulting nanocomposites exhibited improved electrocatalytic activity for ORR with dominant 4 electron pathway in alkaline solutions. The exposed active edges as well as the synergistic effect and reduced resistance connection jointly make the MoS2/NG composite a highly competitive ORR catalyst.

We describe an electrochemical sensor for melamine based on a glassy carbon electrode (GCE) modified with reduced graphene oxide that was decorated with gold nanoparticles (AuNP/rGO). The AuNPs/rGO nanocomposite was synthesized by co-reduction of Au(III) and graphene oxide and characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The response of the modified GCE to melamine was investigated by using hexacyanoferrate as an electrochemical reporter. It is found that the electrochemical response to hexacyanoferrate is increasingly suppressed by increasing concentration of melamine. This is attributed to competitive adsorption of melamine at the AuNP/rGO composite through the interaction between the amino groups of melamine and the AuNPs. The presence of rGO, in turn, provides a platform for a more uniform distribution of the AuNPs and enhances the electron transfer rate of the redox reaction. The findings were used to develop a sensitive method for the determination of melamine. Under optimized conditions, the redox peak current of hexacyanoferrate at a working voltage of 171 mV (vs. SCE) is linearly related to the concentration of melamine in 5.0 to 50 nM range. The method was successfully applied to the determination of melamine in food contact materials.