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The development of bimodal systems with signals for two diagnostic techniques has been increasing. Magnetic resonance imaging (MRI) is a non-invasive technique that distinguishes pathological tissues from healthy ones. To improve the images' contrast, nanoparticulate contrast agents (CAs) have been developed, allowing for the attachment of several CA molecules in one nanoparticle. In this work, we associated AgInSe2 quantum dots (QDs) with gadolinium complexes, obtaining nanoprobes for MRI and optical imaging. The nanosystems showed good optical properties and values of relaxivity superior to the CAs used clinically. Thus, these nanoprobes have the potential to be used as CAs for MRI and optical imaging. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an efficient method for mercury(II) and glutathione detection using a fluorescent nanoprobe as a sensor. Carbon dots were synthesized from polyethyleneimine and ammonium citrate via a one-step hydrothermal method. The fluorescence of carbon dots was quenched since electron transfer occurred due to the interaction between mercury(II) and functional groups on the surface of carbon dots. Adding glutathione to the carbon dots-mercury(II) system, the fluorescence was recovered due to the stronger binding ability of glutathione to mercury(II). Based on the above-mentioned principle, this "off-on" fluorescent sensor can easily achieve the detection of mercury(II) and glutathione, which provided limits of detection of 22.45 nM and 61.89 nM, respectively. In this paper, the proposed method has been applied to detect mercury(II) and glutathione in real lake water and serum, respectively, and a logic gate for sensing glutathione was presented. The developed "off-on" fluorescent sensor with high sensitivity and selectivity has shown great potential for mercury(II) and glutathione detection in environmental and biosensing fields. [ABSTRACT FROM AUTHOR]

Ratiometric fluorescence (FL) probes can eliminate the background interference and provide more accurate detection results than single emission intensity-based nanoprobes. Recently, carbon dots (CDs)-based ratiometric FL probes have received extensive research attention due to their excellent biocompatibility, water solubility, and multi-emission capabilities. In this review, we firstly summarize the construction strategies of CDs-based ratiometric FL probes, including physical mixing, nanohybrid, and dual-emitting CDs strategies. Additionally, we classify the sensing types of CDs-based ratiometric FL probes into five categories according to the difference in spectral variation caused by analytes: "single-response-ON", "single-response-OFF", "double-responses-ON", "double-responses-OFF", and "double-responses-Reverse" types. Finally, a thorough overview of CDs-based ratiometric FL probe applications in ions, molecules, pH, and temperature sensing is provided. We believe this review can show the latest research progress of CDs-based ratiometric FL sensing fields and provide perspectives on future developments for the construction of CDs-based ratiometric FL probes and their potential applications. [ABSTRACT FROM AUTHOR]

Excitation-emission orthogonalized luminescent upconversion nanoparticles (OUCNPs), which can respond to changes in external stimuli accordingly, show great promise in many intelligent applications. However, the construction of such materials mostly relies on the selective absorption of Nd3+ and Yb3+ at different wavelengths and the long-range energy migration between the layers, resulting in complex structures and limited orthogonal luminescence intensity. Herein, we developed a relatively simple structure of OUCNPs (β-NaErF4@NaLuF4@NaYF4:20%Yb, 2%Er@NaLuF4), where the fluorescence emission switches from red to green when the excitation wavelength is shifted from 808 to 980 nm. This structure exhibits high-quality, independent, and non-interfering orthogonal luminescence properties without Nd3+ sensitization and long-range energy migration. As a proof of concept, we demonstrate the application of the designed OUCNPs in anti-counterfeiting. We also prepared OUCNPs@PEI (PEI = polyethylenimine) self-referencing fluorescent probes to enable quantitative analysis of trinitrotoluene (TNT) in solution with a detection limit of 3.04 µM. The probes can be made into test strips for portable on-site visual detection of TNT, and can also be used to image latent fingerprints and detect explosive residues in fingerprints simultaneously. The concept proposed in this work can be extended to the visual detection of a larger range of organic and biological molecules, and is highly promising for practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescent nanoprobe sensor depending on using luminescent metal organic framework (LMOF). • Fluorescent probe for a non-chromophoric food additive monosodium glutamate(MSG) • The nanoprobe was applied to determine this food additive in the instant noodles. • AGREE, AGREEprep, and BAGI metrics were evaluated for the method. This work reports the development and application of a new fluorescent nanoprobe sensor depending on using luminescent metal organic framework (LMOF). The developed sensor composed of hybridized Ca 1,3,5-benzenetricarboxylic acid metal organic framework with microcrystalline cellulose (Ca-BTC/MCC MOF) as a fluorescent probe for the determination of the monosodium glutamate (MSG), a non-chromophoric food additive. The developed sensor was characterized using a high-resolution scanning electron microscope (HR-SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The Ca-BTC/MCC MOF hybrid, examined under the HR-SEM, showed morphological features different from the MCC and the Ca-BTC MOF. The diffraction patterns of Ca-BTC/MCC composites clearly displayed the characteristic Ca-BTC MOF diffraction bands, indicating that MCC was successfully incorporated in the formation of crystalline MOF hybrids. The FTIR spectra show the bands of MCC, as well as the bands of Ca-BTC MOFs. The prepared nanoprobe was successfully applied as a sensitive sensor for the determination of MSG in food sample. The method was validated following the International ICH (Q2)R2 guidelines in terms of precision, trueness and other main analytical figures of merit, comprised the green profile and practicability metrics. A wide linearity range was achieved (5–50 µg/mL) with good correlation coefficient (R2 ≥ 0.9993). The recoveries (%) were found in the range of 100.0 to 101.5 and the RSDs (%) were in the range of 0.1 to 0.9 %. These results show that the developed nanoprobe was selective, and highly accurate to determine this important food additive in the seasonings of instant noodles, also showing a reduced environmental impact based on the metrics currently accepted for the evaluation of the green profile and practicability. [ABSTRACT FROM AUTHOR]

To investigate the possible sources of the switching field distribution in bit-patterned media, we applied a scanning hard-X-ray nanoprobe technique based on X-ray magnetic circular dichroism spectroscopy to an array of Co-Pt dots with the typical diameters of 200 nm. Element-specific magnetization curves at the Pt L3 edge were measured for individual dots isolated from each other, and the magnetization switching field (coercivity) values were determined for more than 100 individual dots. To assess the effect of dot diameters as a possible source of switching field distribution, a statistical analysis of the coercivity values and dot diameters measured for many dots was performed. The resulting switching field distribution had a mean of = 1:80 kOe and a standard deviation of σHSW=0.64 kOe. The relative deviation of σHSW/ = 36% was not in good agreement with the relative dispersion in a dot diameter of σD/ = 2:7%, and no clear correlation between the coercivity and dot diameter was observed. These results may suggest other possible sources of switching field distribution than dot diameter, such as dispersion in the c-axis orientation and in magnetocrystalline anisotropy. [ABSTRACT FROM AUTHOR]

Nanoprobe tips are key components in many applications such as scanning probe microscopes, nanoscale imaging, nanofabrication and sensing. This paper describes a dynamic chemical etching method for the fabrication of optical nanoprobes. The tips are produced by mechanically rotating and dipping a silica optical fibre in a chemical etching solution (aqueous hydrofluoric acid) covered with a protection layer. Using different dynamic regimes of the mechanical movements during the chemical etching process, it is possible to vary the cone angle, the shape, and the roughness of the nanoprobes. It is found that the tip profiles are determined by the nonlinear dynamic evolution of the meniscus of the etchant near the fibre. Computational fluid dynamic simulations have been performed, showing that different flow regimes correspond to different shear forces acting on the forming nanotip, in agreement with experimental results. With this method, a high yield of reproducible nanotips can be obtained, thus overcoming the drawbacks of conventional etching techniques. Typical tip features are short taper length (~200 lm), large cone angle (up to 40°), and small probe tip dimension (less than 30 nm). [ABSTRACT FROM AUTHOR]

• Copper peroxide nanodot was utilized as signal nanoprobe for photoelectrochemical sensor. • The nanodots were encapsulated in metal-organic frameworks. • The nanoprobe can self-supply H 2 O 2 by encapsulated CPNs under acidic condition. • The produced H 2 O 2 can help generate insoluble precipitation onto sensor surface. • The formed precipitation resulted in decrease of photoelectrochemical current intensity. Signal nanoprobe based on copper peroxide nanodots (CPNs) embedded within metal–organic frameworks (ZIF-8) was applied for developing photoelectrochemical (PEC) sensor for detection of circulation tumor cells (CTC). The nanoprobe can self-supply H 2 O 2 by encapsulated CPNs under acidic condition. The produced H 2 O 2 can help generate insoluble precipitation onto sensor surface in the presence of horseradish peroxidase (HRP), leading to suppressed PEC current intensity. MCF-7 was selected as model CTC, which was enriched and separated from samples by antibody modified magnetic beads (MB). Organic semiconductor BTA-C4Ph and PM6 were chosen to form n-p heterojunction on sensor surface with enhanced PEC current intensity. The PEC sensor was constructed based on "sandwich" protocol, which has a linear range from 5 cell/mL to 100 cell/mL and a limit of detection (LOD) of 3 cell/mL (S/N = 3) for MCF-7. What more, the sensor was successfully applied for detection of MCF-7 in whole blood samples. [ABSTRACT FROM AUTHOR]

Highlights • A spherical DNAzyme-based two-photon nanoprobe has been developed for high sensitive and selective monitoring of miRNA in live cells. • DNAzyme has the significant signal amplification ability. • The SNA probe has the properties of resistance to enzymatic degradation, enhanced nucleic acid binding and excellent cellular uptake. • This two-photon SNA probe may serve as a new tool for getting insight into the functionality of miRNAs in a wide range of biological processes. Abstract Two-photon excitation (TPE) has excellent properties, such as lower tissue self-absorption and autofluorescence, reduced photodamage and photobleaching, and higher spatial resolution. Meanwhile, DNAzyme has significant signal amplification ability, and the gold nanoparticle (AuNP)-based spherical nucleic acid (SNA) has the properties of resistance to enzymatic degradation, enhanced nucleic acid binding and excellent cellular uptake. Taking advantage of their properties, in this work, we constructed a novel SNA-based TPE fluorescent DNAzyme probe for the selective and sensitive detection of target miRNA in living cells. Briefly, AuNPs were first functionalized with the substrate sequences hybridized to two split fragments of the 8–17 DNAzyme-contained sequence. Then, numerous two-photon absorption (TPA)-dye molecules of Ethyl-4-[3,6-Bis (1-methyl-4-vinylpyridium iodine)-9 H -carbazol-9-yl)] (EBMVC) were inserted into the substrate/split-DNAzyme duplexes on the surface of the AuNP to form the TPE SNA nanoprobe in the "off" fluorescence emission state. When the target miRNA is bound, the conformation of the split DNAzymes will change resulting in the activation of their catalytic ability, thus leading to cleavage of the substrate sequences and the release of the TPA-dye molecules-inserted DNAzyme motif from the surface of the AuNP. Concurrently, the released target miRNA would autonomously hybridize with another split DNAzyme motif and activate further cleavage reactions. This would induce the gradual dissociation of the TPA-dye molecules-inserted DNAzyme motifs from the surface of the AuNP through the repeated target miRNA hybridization-activated cleavage reaction and thereby trigger the cascade TPE fluorescence emission, ultimately achieving the detection of the miRNA through amplification of the fluorescence signals. The assay was successfully validated with clean buffer conditions as well as with cells. [ABSTRACT FROM AUTHOR]

Abstract Surface-enhanced Raman scattering (SERS) has a great potential as a sensitive probe for analytical detection, but the low level of reproducibility remains a challenge for quantitative detection. To enhance the reproducibility, an internal standard that is incorporated between the core and shell structure of metal nanoparticles (NPs) can be employed. However, the unstable sol form of "core-shell" substrates has been unsatisfactory, causing rapid agglomeration. Herein, we prepared a SERS-active core-Raman labeling chemical (RLC)-shell material based on Au-Ag NPs assembled on silica NPs (SiO 2 @Au@RLC@Ag NPs) as internal-standard-containing NPs. When 4-mercaptobenzoic acid (4-MBA) was used as a model RLC with a silica template, the Raman intensity of SiO 2 @Au@4-MBA@Ag was ∼8-fold higher than that without a silica template (Au@4-MBA@Ag NPs). Concentrations of 4-MBA in the range of 1 × 10−6 to 1 × 10−2 M incorporated between the SiO 2 @Au core and the Ag shell did not significantly affect the Ag shell coating. Nevertheless, the Raman intensity increased linearly and was proportional to the logarithm of the 4-MBA concentration. When SiO 2 @Au@4-MBA@Ag was utilized as internal-standard-containing NPs, the dynamic linear range of thiram detection was 5–50 μM with a limit of detection of 1.2 μM. These results show that our material can be used for the broad dynamic detection of (bio)-chemical traces with high sensitivity. Highlights • An Au@-4-MBA@Ag assembled silica nanoparticles have been prepared. • Raman intensity of SiO 2 @Au@4-MBA@Ag was ∼8-folds higher than that of Au@4-MBA@Ag. • The linear range of thiram detection was 5–50 μM. • The limit of detection of thiram lower to 1.2 μM. [ABSTRACT FROM AUTHOR]

Deoxynivalenol (DON) is a toxic secondary metabolite produced by several species of Fusarium fungi, which can be predominantly found in agricultural crops such as wheat. In livestock, deoxynivalenol-contaminated grain can produce vomiting, feed refusal, weight loss, and diarrhea. This paper reports an electrochemical immunosensor for the detection of residual DON mycotoxin in food samples. The device uses electrochemical nanoprobes (CdSNP-AbDON) and antigen biofunctionalized magnetic μ-particles (DON-BSAMP) to detect the mycotoxin. CdSNP-AbDON are prepared by labelling the DON-specific antibodies with CdS nanoparticles (CdSNPs). Nanoparticle size and CdSNP-AbDON conjugation ratio are characterized using TEM images. The metal ions released by the CdSNP are reduced at the working electrode and read by anodic stripping voltammetry. DON can be detected in PBST buffer with an IC50 of 6.74 ± 0.19 μg L−1. The high detectability of the immunosensor developed allows detection of DON residues in 50-fold diluted wheat extracts. The limit of detection (LOD, IC90) accomplished in wheat is of 342.4 μg kg−1, which is below the maximum residue limit (MRL, 1750 μg kg−1 for unprocessed durum wheat, 750 μg kg−1 for cereals intended for direct human consumption) established by the EU for this mycotoxin. The working range is in the interval between 610 and 6210 μg kg−1. The performance of the immunosensor was compared with the ELISA assay. DON naturally contaminated wheat samples were analyzed with the immunosensor, showing acceptable recoveries. Graphical abstract [ABSTRACT FROM AUTHOR]

Precision diagnosis and effective treatment are the cores of early cancer therapy. Here, for the first time, we report a hybridization chain reaction-based nanoprobe for selective and sensitive cancer cell recognition and amplified photodynamic therapy. [ABSTRACT FROM AUTHOR]

Abstract Based on multifunctionalized zeolitic imidazolate frameworks (ZIFs)-initiated cascade reaction triggered signal amplification strategy, a novel sandwich-type amperometric immunosensor was constructed for ultrasensitive detection of carbohydrate antigen 24-2 (CA 242). The methylene blue-glucose oxidase-ZIF-8/reduced graphene oxide-Au (MB-GOx-ZIF-8/Au-rGO) was synthesized by a facile coprecipitation method for enzyme immobilization and redox species loading. The multifunctionalized ZIFs conjugated with labeling antibodies were employed as immunoprobe. In the presence of glucose, tandem reaction was driven by the immunoprobe to catalyze the glucose oxidation to yield H 2 O 2. Simultaneously, the generated H 2 O 2 induced the decomposition of poly(anilineboronicacid) (PABA)/poly(vinyl alcohol) (PVA) films on substrate, which made the PVA chains breaking away from PABA polymer. Due to the poor conductivity of PVA chains, this decomposition reaction can amplify the current signal. The current difference (ΔI) caused by per unit concentration target with tandem reaction amplification was elevated prominently, resulting in ultrasensitive analytical performance of the immunosensor. Under optimal conditions, the proposed immunosensor displayed wide linear range from 0.001 to 1000 U mL−1 with an ultralow limit of detection 69.34 μU mL−1 (S/N = 3). This method successfully implemented functionalized ZIFs in immunoprobe construction for sensitivity amplification, providing a promising strategy to construct ultrasensitive immunosensing platform for analysis of other tumor marker. Highlights • Multifunctional ZIFs were synthesized for enzyme and redox species loading. • Glucose-triggered cascade reaction was used for signal amplification. • The immunosensor displayed ultralow limit of detection 69.34 μU mL−1. [ABSTRACT FROM AUTHOR]

Abstract Immunochromatographic strip (ICTS) nanosensors are one of the most popular point-of-care (POC) diagnostic devices currently available for rapid target screening. However, the widely used ICTS sensors based on 20–40 nm gold nanoparticles (AuNPs) as labels are limited by their low detection sensitivity due to their relatively weak color intensity. Moreover, the ever-increasing demand for high sensitivity is restricting the application of conventional AuNP-based ICTS methods. Improving the color signal intensity of AuNP nanoprobes can theoretically overcome the limitations encountered by traditional ICTS assays. In recent years, the design of various improved strategies for the enhanced detection sensitivity of ICTSs has received increasing interest. In this review, we systematically summarize the emerging amplification strategies used to enhance the detection sensitivity of conventional AuNP-based ICTS nanosensors. These strategies include 1) signal enhancement mediated by nanoparticle accumulation, 2) signal amplification induced by noble metal nanoparticle growth, 3) signal enhancement based on enzyme-mediated colored product deposition, and 4) signal amplification assisted by nanoparticle flow rate regulation on strips. Representative examples are selected to demonstrate the proof-of-concept and their potential applications in biosensing. The study focuses on elaborating the underlying mechanisms of each strategy for the enhanced colorimetric signal intensity of AuNPs on the test regions of a strip. Finally, we briefly discuss the current limitations and future perspectives in this field. Graphical abstract Image 1 Highlights • Various emerging signal amplification strategies are widely introduced to enable sensitive AuNP-based ICTS nanosensors. • This review provides a systematic overview of emerging amplification strategies for enhanced AuNP-based ICTS nanosensors. • The emphasis is placed on the underlying amplification mechanisms for each strategy. • This work can serve as a reference to promote an extensive and deep research in this field. [ABSTRACT FROM AUTHOR]

Abstract Aluminum ions, as a kind of non-essential element, show a negative impact on plants growth and contribute to diseases caused by nervous breakdown like Alzheimer's disease and Parkinson's disease. Hence, the detection of Al3+ in environment and human body is of great significance and valuableness. Herein, a N-H-type excited-state intramolecular proton transfer (ESIPT) based self-assemble nanoprobe has been designed and synthesized for the detection of Al3+. Owing to phthalandione and tosyl group, probe ABTTA could self-assemble into nanoparticles with nearly no fluorescence. However, ABTTA would be further aggregated by Al3+ ions in aqueous solution which results in enhanced fluorescence (peaking at 555 nm). Based on this principle, a novel analytical method for detection of Al3+ was established with a limit of detection of 50 nM, which was much better than most of reported probes. Moreover, the nanoprobe with excellent water solubility was successfully applied for the detection of Al3+ in real water sample with satisfactory measurement accuracy. Benefited from the favorable water solubility, the nanoprobe was further utilized to the detection of Al3+ in human cancer samples, demonstrating its potential application for biological imaging. Graphical abstract fx1 Highlights • A novel nanoprobe ABTTA based on ESIPT effect is designed and synthesized. • ABTTA can self-assemble and show strong fluorescence under the addition of Al3+. • The detection limit is low to 50 nM. • Nanoprobe could detect Al3+ in real water samples with high precision. • Nanoprobe ABTTA is applied to detect Al3+ in living system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A strongest multiple fluorescent N-CQDs were synthesized from the P. acidus fruits. • Synthesized N-CQDs showed low-toxic and were employed for in vivo live-cell imaging. • The N-CQDs were uniformly stained within the body of the nematodes (C. elegans). • The live-cell imaging result reveals the usage of N-CQDs in drug delivery. Abstract In this work, nitrogen-doped carbon quantum dots (N-CQDs) have been synthesized successfully by a simple hydrothermal method and demonstrated its application for multicolor imaging in Caenorhabditis elegans (C. elegans) as an in vivo model. The synthesized N-CQDs were characterized by various physicochemical techniques such as XRD, Raman spectroscopy, ATR-FTIR spectroscopy, XPS, HRTEM, UV–vis spectroscopy, and fluorescence spectroscopy. The synthesized N-CQDs exhibited a strong fluorescence due to the uniform size distribution with nitrogen-containing and oxygen-containing functional groups onto the surface of N-CQDs which induce the excellent dispersibility in aqueous media. The N-CQDs has an excitation-dependent fluorescence behavior and the strongest fluorescence appeared at 411 nm (emission peak position) under the excitation of 340 nm. Also, the N-CQDs displayed a high quantum yield (QY) of 12.5. The fluorescence behaviour of the aqueous N-CQDs suspension retains for a long time up to 1 year. The prolonging fluorescent N-CQDs was utilized as a staining agent for bioimaging and toxicity of N-CQDs on C. elegans that was conducted by killing assay. In-vivo studies suggested that the N-CQDs displayed excellent biocompatibility and successfully used for high-contrast imaging of N-CQDs in living and dead C. elegans. Based on the strongest fluorescence along with excellent aqueous dispersibility and biocompatibility, the green synthesized N-CQDs would be an ideal candidate for many biological applications. [ABSTRACT FROM AUTHOR]

To improve the bioimaging signal‐to‐noise ratio (SNR), long‐term imaging capability, and decrease the potential biotoxicity, an in vivo cross‐linking strategy was developed by using sub‐10 nm, glutathione‐modified, lanthanide nanoprobes. After administration, the nanoprobes cross‐link in response to reactive oxygen species (ROS) at the inflamed area and enable the quick imaging of ROS in the second near‐infrared (NIR‐II) window. These nanoprobes could be rapidly excreted due to their ultra‐small size. This strategy may also be applied to other ultra‐small contrast agents for the precise bioimaging by in situ lesion cross‐linking. [ABSTRACT FROM AUTHOR]

We develop a novel peptide-based four-color fluorescent polydopamine nanoprobe for multiplexed sensing and imaging of tumor-related proteases in living cells. This nanoprobe responds rapidly and selectively, enabling simultaneous and high-contrast imaging of multiple proteases in living cells. Furthermore, it could detect the changes of protease expression in living cells. [ABSTRACT FROM AUTHOR]

An activatable organic semiconducting nanoprobe that specifically turns on its second near-infrared window fluorescence upon being exposed to nitric oxide stimuli was developed for in vivo, in situ, real-time and high-spatial-resolution mapping of drug-induced hepatotoxicity. [ABSTRACT FROM AUTHOR]

Abstract Surface-enhanced Raman scattering (SERS) still faces a big challenge in bioanalysis due to the biological background interference and the poor reproducibility of the Raman signal. Accordingly, herein a novel surface-enhanced Raman scattering (SERS) nanoprobe is prepared via the co-assembly of 3-(4-(phenylethynyl)benzylthio) propanoic acid (PEB) tagged-peptides and 4-thiol phenylacetylene (TPA) on gold nanorods, and used for the measurement of caspase 3, as a biomarker. A key advantage of this system is the lack of background alkyne signals throughout the cell. The two alkyne-bearing molecules produce distinct SERS signal but the PEB signal decreases in response to the peptide-cleavage activity of caspase 3, thereby allowing the ratiometric detection of analytes. Under the optimized conditions, the ratiometric peak intensity of I 2027 /I 2218 dynamically increased with increasing caspase 3 concentration in the range from 12.5 to 500 ng/mL, with a detection limit of 1.99 ng/mL based on a signal-to-noise ratio of S/N = 3. The nanoprobe has been successfully applied in a live cell imaging assay of caspase 3 and in an ischemia–reperfusion surgery-treated rat living tissue model. Graphical abstract Image 1 Highlights • A novel SERS strategy for caspase 3 detection has been established. • Alkyne introduced into as the Raman reporter can efficiently reduce the background interference of the cellular components. • The ratiometric signal output strategy could greatly improve the Raman signal reproducibility of the SERS nanosensor. • The prepared SERS nanoprobe was successfully applied for caspase 3 assay in a rat living tissue model. [ABSTRACT FROM AUTHOR]

Abstract Owing to its dual role as a hormone and neurotransmitter, norepinephrine (NE) detection is of great significance to biomedical diagnosis. In the present work, we have explored intense green fluorescence of poly (norepinephrine) (PNE) nanoparticles synthesized by oxidizing NE in alkaline condition, in combination with red fluorescent bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) for naked-eye detection of NE. The effect of sodium hydroxide on the emission behavior of NE was studied. The surface morphology and optical properties of PNE nanoparticles were characterized by UV–Vis, fluorescence, FTIR, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. For ratiometric sensing of NE, red fluorescent BSA-AuNCs were served as an internal reference while NE delivered a new emission peak at 527 nm, resulting in a wide distinguishable color change from strong red into red, pink, orange, and green under a UV lamp. The ratiometric approach was demonstrated to be highly sensitive and selective for NE detection against even structurally similar biomolecules with a detection limit of 49 nmol L−1. Furthermore, the proposed method was successfully applied to determine NE in urine samples. Graphical abstract Image 1 Highlights • The oxidation product of norepinephrine has intense green fluorescence. • A naked-eye ratiometric fluorescence method has been developed for norepinephrine detection. • Different concentrations of norepinephrine were identified by color changes from red to green. • High selectivity was achieved without the interference of structurally similar molecules. • A simple and low-cost sensor has been presented for norepinephrine detection in urine samples. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • SERS nanoprobe for HOCl and ONOO- is developed on basis of their respective reaction with p -methoxyphenol and phenylboronate. • The SERS nanoprobe performs well on the simultaneous response to HOCl and ONOO- because of narrow SERS peaks for spectral multiplexing. • The SERS nanoprobe has high selectivity for HOCl and ONOO- respectively due to SERS fingerprinting and reactions specificity. • With the SERS nanoprobe, in-situ simultaneous imaging of the HOCl and ONOO- generated in living cells can be accomplished readily. Abstract Hypochlorous acid (HOCl) and peroxynitrite (ONOO−) are two important intracellular reactive oxygen species (ROS) as crucial mediators in diverse pathological and physiological processes. Nonetheless, many of their functions are still inexplicit due to the shortage of methods for simultaneously detecting intracellular HOCl and ONOO−. Here we present a novel kind of reaction-based surface-enhanced Raman scattering (SERS) nanoprobes, gold nanoparticles (AuNPs) modified with synthesized 2-mercapto-4-methoxy-phenol (MMP) and 4-mercaptophenyl boronic acid pinacol ester (MBAPE), to synchronously detect HOCl and ONOO− in single living cells. Taking advantage of narrow SERS peaks for spectral multiplexing, the simultaneous detection is accomplished with the SERS variation of AuNPs/MMP/MBAPE nanoprobes caused by the respective reaction of MMP and MBAPE bonded on AuNPs with HOCl and ONOO−. The AuNPs/MMP/MBAPE nanoprobes demonstrate a less than 1 min response to HOCl and ONOO− with a sensitivity at 10−7 M level. The presented nanoprobes also have high selectivity for HOCl and ONOO− respectively, resulting from SERS fingerprinting coupling with reaction specificity. Moreover, the proposed SERS strategy can be used for the simultaneous imaging of endogenous HOCl and ONOO− in a single living macrophage, showing great application potential in studies of HOCl- and ONOO−- involved physiological events. [ABSTRACT FROM AUTHOR]

Current lysosomal H 2 S-responsive fluorescent probes usually possess notorious aggregation caused quenching (ACQ) phenomenon and suffer from the inevitable background fluorescence signals. To circumvent this problem, we here combined H 2 S recognizing aggregation-induced emission (AIE) group with photochromic spiropyran moiety to rational design novel photoswitchable AIE nanoprobe (DNBS-DCM-SP) for lysosomal H 2 S detection with high spatiotemporal resolution. In the presence of H 2 S, the electron-withdrawing DNBS moiety will deviate from DNBS-DCM-SP via a H 2 S-induced O S bond cleavage, induced a sensitive turn-on fluorescence response at about 592 nm. The prepared nanoprobe displays good sensitivity (∼5.0 nM), and high specificity (especial against other thiols). In additon, the fluorescence of the H 2 S-activated AIE nanoprobe (DCM-SP) can be reversibly switched by selective fluorescence resonance energy transfer (FRET) from the AIE fluorophore (DCM) to ring-opened state of spiropyran via alternating UV/visible light irradiation. Moreover, the feasibility of the prepared photoswitchable AIE nanoprobe is also demonstrated by mapping the production of endogenous H 2 S in living cells as well as reversible dual-color fluorescence imaging. [ABSTRACT FROM AUTHOR]

Abstract In this study the effect of nature of nanostructural materials used as colorimetric optical probes on the analytical performance of the resulting sensors is compared. Different effects related to the nanoprobe materials - probe structure and properties: surface charge and stability, but also effects related to the analyte – receptor interactions – complex formation kinetics and transport of ions from the sample to the probe were taken into account. Presence of charge on the nanostructural colorimetric sensor effectively hinders ions exchange between the probe and the sample, leading to a linear dependence of absorbance on logarithm of analyte concentration changes. Interestingly, both anionic and cationic micelles are offering linear dependence on logarithm of concentration, covering 2 logarithmic units. Nanostructures, e.g. prepared from amphiphilic polymer Pluronic F127, lead to absorbance dependence on concentration observed in rather narrow concentration range. In this respect crosslinked poly(maleic anhydride- alt -1-octadecene) nanostructures of pH tunable surface charge, due to the presence of carboxyl and amine group on the surface, seem an attractive alternative, offering also the lowest detection limits among tested systems. This system is stable even in the presence of high concentration of background electrolyte in the sample and offers the lowest detection limit, what makes it useful as e.g. indicator for titration. Generally from the results obtained it follows that inert complexes, hindering ion transport to the probe, can be used to expose a linear dependence of the optical signal on logarithm of concentration, whereas for labile complexes formed sigmoidal type dependences of higher sensitivity over limited concentration range are obtained. Highlights • Effect of nanostructures properties on analytical properties is shown. • Higher lipophilicity of the nanostructure results in lower detection limit. • The absorbance vs. concentration relation is dependent on complex formation rate and surface charge of the nanostructure. [ABSTRACT FROM AUTHOR]

Abstract Synchrotron-based techniques are increasingly used in the field of cultural heritage, and this review focuses notably on the application of nano-beams to access high-spatial-resolution information on fragments sampled in historical or model artworks. Depending on the targeted information, various nano-analytical techniques can be applied, providing both identification and localization of the various components. More precisely, nano-X-ray fluorescence probes elements, nano-X-ray diffraction identify crystalline phases, and nano X-ray absorption spectroscopy is sensitive to speciation. Furthermore, computed tomography-based techniques can provide useful information about the morphology and in particular the porosity of materials. [ABSTRACT FROM AUTHOR]

Graphical Abstract Fluorescent activatable gadofullerene nanoprobes as new NIR-MR dual-modal imaging contrast for in vivo imaging. Highlights • Nanoprobe was prepared by linking Gd@C 82 derivative with NIR783 via disulfide bond. • Nanoprobe was used to dual-modal MR/NIR imaging with the fluorescence activatable. • Fluorescence activatable was due to the breakage of -S-S- in the presence of thiol. • In vivo cytotoxicity studies proved the low toxic of the nanoprobes. Abstract Dual mode imaging technology is widely developed to achieve the early-stage precision cancer diagnosis. Here we designed a dual-modal magnetic resonance/near infrared fluorescence optical imaging contrast agent (GdF-SS-NIR783) with the fluorescence activatable and safer gadofullerene. The nanoprobes were fabricated by conjugating the gadofullerene derivatives with a NIR fluorescence imaging agent (NIR783) via the disulfide bond. The obtained nanoprobes showed no fluorescence (OFF), but the fluorescence turned on when incubated within reduction environment such as GSH solution. The clear fluorescence signal in tumor site was observed obviously after their intratumor injection. The nanoprobes also revealed efficient MRI contrast enhancement both in vitro and in vivo. And they showed good biocompatibility and did not demonstrate any tissue toxicity in vivo. This work gave the new possibility in designing more efficient and safer nanoprobes for future medical diagnoses. [ABSTRACT FROM AUTHOR]

Activatable 19F MRI nanoprobes for sensing caspase-1 activity were developed. Tandem repetition of substrate peptide sequences improved the turn-on response of nanoprobes, allowing detection of caspase-1 activity by 19F MRI. In vivo immune response was successfully imaged using the new nanoprobe. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel small molecule-conjugated photoaffinity nanoprobes have been synthesized. • A hydrophilic spacer promoted the water dispersibility of the nanoprobes. • Arylazide on nanoprobes enabled a most selective crosslinking of a model binding protein. Abstract We designed and synthesized a set of photoaffinity nanoprobes, which multivalently display a small molecule ligand and a photoreactive group on gold nanoparticles. Due to the typically hydrophobic nature of these two functional groups, a hydrophilic spacer was additionally introduced to co-functionalize the nanoprobes to maintain their dispersibility in aqueous buffer solutions. Photoaffinity labeling studies using the nanoprobes composed of different ratios of three functional groups showed that including high density of the spacer group attenuates crosslinking efficiency. Comparative analysis of the reactivity among three major photoreactive groups suggested that unlike in the context of conventional photoaffinity probes, arylazide group enables the most selective crosslinking of a model small molecule binding protein. [ABSTRACT FROM AUTHOR]

Single-domain antibody (sdAb) or nanobody possesses specific features non-accessible for conventional antibodies that make them suitable for research and biotechnological applications. Porcine epidemic diarrhea virus (PEDV) causes lethal diarrhea in piglets, resulting in great economic losses all over the world. To detect and isolate PEDV rapidly and accurately is important for the control and further research of the clinical PEDV strains. In this study, four sdAb fragments (sdAb-Mc19/29/30/37) targeting the membrane (M) protein of PEDV were selected from sdAb library that was constructed through M protein-immunized Camelus bactrianus. The selected sdAb-Mcs were solubly expressed in Escherichia coli. The functional characteristics analysis revealed that the recombinant sdAb-Mcs have excellent binding activity and specificity to M protein but have no neutralizing activity to PEDV. For further application, sdAb-Mc37 was conjugated with quantum dots to synthesize a nanoprobe for imaging PEDV in vero cells. The observed fluorescence in vero cells clearly reflects that PEDV virions can be reliably recognized and labeled by the nanoprobe. Furthermore, the sdAb-Mc29 was conjugated with superparamagnetic nanobeads to construct immunomagnetic nanobeads (IMNBs) used to isolate PEDV. One PEDV strain was successfully isolated from clinical fecal sample, suggesting IMNBs as a novel and efficient tool suitable for PEDV isolation from clinical samples. This study provided a novel application and substantiated the suitability of sdAb as a specific binder for the isolation of viruses. [ABSTRACT FROM AUTHOR]

Highlights • Novel type of piezoresistive SThM cantilevers that allow for quantitative spatial and thermal observations. • Integrated thermal probe (due to compact size) ideal for application in small AFM heads without optical beam deflection measurement. • LoFM scanning mode for thermal observation of the nanosize structures. • Characterization of the mechanical probe parameters and piezoresistive deflection sensor combined with calibration of the thermal tip response allowed for quantitative measurements of the thermal behavior of silicon nanoresistors. The technology described in this article made it possible to map temperature distribution on 200 nm wide nanowire biased with current 500 µA. Abstract In this paper we present design and application of novel piezoresistive scanning thermal microscopy (SThM) probes. The proposed probe integrates a piezoresistive deflection sensor and thermally active, resistive nanosize tip. Manufacturing technology includes standard silicon MEMS/CMOS processing and sophisticated postprocessing using Focus Ion Beam milling. Authors also describe dedicated measurement technique in order to perform quantitative nanoscale thermal probing. Performance of the developed thermal probes is validated by test scans (topography and temperature distribution) of silicon nanoresistors supplied with current. [ABSTRACT FROM AUTHOR]

We designed and synthesized a highly water-soluble biological nanoprobe (Au-GS@ β -CD) through the covalent bonding of β –cyclodextrin ( β -CD) onto the surface of gold nanoclusters (NCs) (Au-GS). The morphology, composition and photophysical properties of as-prepared Au-GS and Au-GS@ β -CD NCs were fully characterized. The maximum emission intensity at about 600 nm of Au-GS@ β -CD NCs increased significantly as compared to Au-GS NCs, which is consistent with its effective absorption enhancement. The water solubility and biocompatibility of resultant Au-GS@ β -CD NCs were also notably enhanced, which allow it to be selectively uptaken by gastric cancer cells (MGC-803) and exhibit red luminescence in the cells. Thus, the as-prepared Au-GS@β-CD NCs could be used as promising biological nanoprobes for diagnosis of gastric cancer cells. The successful loading of doxorubicin (DOX) also allows it to hold attractive ability of drug delivery. Moreover, both Au-GS and Au-GS@ β -CD NCs are thermally responsive. Furthermore, the metal ions detection experiments indicate that both Au-GS NCs and Au-GS@ β -CD NCs can selectively recognize Pb 2+ , Al 3+ , Cu 2+ , Fe 3+ and Ag + ions through luminescence change. The detection limits of Pb 2+ and Fe 3+ are improved for Au-GS@ β -CD NCs due to the synergistic effect of β -CD and Au NCs. [ABSTRACT FROM AUTHOR]

Aggregation-induced emission (AIE) is an abnormal phenomenon, which has been extensively explored for various applications. Taken advantage of the unique AIE feature, a number of luminescent nanoprobes with strong fluorescence intensity could thus be fabricated through different strategies; however, the fabrication of AIE-active carbohydrate polymers is still challenge owing to the poor solubility of carbohydrate polymers in most of organic solvents. In this work, a rather facile strategy has been developed for fabricating AIE-active sodium hyaluronate (Sh) through the formation of dynamic phenyl borate between the phenylboronic acid groups of AIE dye (An-B(OH) 2 )) and Sh in a “one-pot” route. This reaction could occur under low temperature, air atmosphere and in the present water. The physicochemical properties, biocompatibility, biological imaging and drug delivery performance of the final An-Sh fluorescent organic nanoparticles (FNPs) were confirmed by different characterization techniques. Results suggested that An-Sh FNPs possess high water dispersibility, strong fluorescence, and good biocompatibility. These excellent properties make An-Sh FNPs great potential for biological imaging and controlled drug delivery applications. In conclusion, we have developed a facile one-pot strategy for the preparation of AIE-active FNPs through the formation of dynamic bonds in rather mild experimental conditions. The outstanding properties and performance of An-Sh FNPs make them promising candidates for biological imaging and controlled drug delivery applications. [ABSTRACT FROM AUTHOR]

Highlights • Introduction to the field of Nanobeam diffraction imaging in materials science with an overview of the main achievements to date. • Historical overview of the evolution from first X-ray nanoprobes to diffraction imaging. • Technical state of the art and limits in terms of spatial resolution vs. lattice parameter resolution. • Scientific state of the art of nanobeam imaging in material science (examples). Abstract Unprecedented tools to image crystalline structure distributions in materials have been made possible by recent advances in X-ray sources, X-ray optics and X-ray methods. Nanobeams combined with diffraction have made it possible to image parameters that were traditionally only addressed as ensemble averages. This enables the study of highly heterogeneous materials such as microelectronic devices and opens a new field of material science on the mesoscale. Coherent nanobeams offer the opportunity to image nanomaterials in three dimensions with a resolution far smaller than the focused beam size. This has opened up new fields in X-ray diffraction in general and has become one of the main drivers for the enhancement of existing, and the construction of new, large scale scientific infrastructure projects around the world. [ABSTRACT FROM AUTHOR]

This review surveys recent advances in optical spectral detection of reactive oxygen species (ROS), particularly singlet oxygen, superoxide, hydroxyl radical, and hydrogen peroxide. Advances using nanoparticles and self-organizing nanostructures as well as optical detection schemes are included. Measurements using plasmonic, luminescent, photocatalytic, or self-organizing nanoparticles are highlighted. The large number of spectrophotometric and luminescent probe methods are categorized by ROS sensing mechanism, signaling mode, (de)activation mechanism, if any, and spectral chromaticity. Reports describing multicomponent ROS detection or novel nanoscale probes are discussed. Measurements using ratiometric, multichannel, or time-resolved detection and nonlinear spectral transitions are reviewed. The focus on developing probe molecules for spectral detection documented over the last 20 years has continued, with sustained emphasis on luminescence detection, but with less focus on spectrophotometric measurements. Use of nanoparticles as probes, probe carriers, and compartmentalization agents in ROS detection is increasing. On the other hand, incorporation of advanced spectral methods, such as nonlinear transition and multichannel detection, is increasing slowly in ROS analysis. This indicates there is a substantial opportunity to develop ROS measurements with use of a synergistic combination of (multi)functional nanoscale systems and advanced optical detection methods to optimize the detection limit, selectivity, and response time.ᅟ [ABSTRACT FROM AUTHOR]

We successfully fabricated 19F magnetic resonance imaging (MRI) nanoprobes by partly replacing the 2-methylimidazolate of the metal organic framework (MOF) matrix ZIF-8, of which the strong 19F MRI signal displays an interesting pH dependence property, indicating its great potential as a 19F MRI contrast agent for stimuli-responsive imaging with high penetration depth and low background. [ABSTRACT FROM AUTHOR]

There is always a substantial effort to develop a point of care detection for a severe and acute disease like dengue. In this work, we have described the detection of serotype-specific dengue virus using multicolor triangular silver nanoparticles (TAg) which could be a potential diagnosis method to distinguish between serotype. Functionalized TAg was prepared with polyA 10 DNA through pH-mediated process. Further, it was characterized with Transmission Electron Microscopy (TEM), Ultra Visible-visible spectroscopy (UV–vis) and gel electrophoresis and its stability towards NaCl concentration. The colorimetric detection was carried out based on the interaction of TAg-DNA probe with specific complimentary strand which was designed to form a network assembly between DNA probes and sample RNA. The hybridization process was enhanced in presence of NaCl (0.4 M) which makes the hybridization process more stable over probe compared to un-hybridization. Therefore a simple and effective colorimetric method was developed to detect the different dengue serotype RNA with high sensitivity and specificity. [ABSTRACT FROM AUTHOR]

Abstract: To achieve the accurate diagnosis of tumor with the magnetic resonance imaging (MRI), nanomaterials‐based contrast agents are developed rapidly. Here, a tumor targeting nanoprobe of c(RGDyK) modified ultrasmall sized iron oxide is reported with high saturation magnetization and high T1‐weighted imaging capability, attributed to a large number of paramagnetic centers on the surface of nanoprobes and rapid water proton exchange rate (inner sphere model), as well as strong superparamagnetism (outer sphere model). These nanoprobes could actively target and gradually accumulate at the tumor site with a time‐dependent T1–T2 contrast enhancement imaging effect. In in vivo MRI experiments, the nanoprobes exhibit the best T1 contrast enhancement at 30 min after intravenous administration, followed by gradually vanishing and generating T2 contrast enhancement with increasing time at tumor site. This is likely due to time‐dependent nanoprobes aggregation in tumor, in good agreement with in vitro experiment where aggregated nanoprobes display larger r2/r1 value (19.1) than that of the dispersed nanoprobes (2.8). This dynamic property is completely different from other T1‐T2 dual‐modal nanoprobes which commonly exhibit the T1‐ and T2‐weighted enhancement effect at the same time. To sum up, these c(RGDyK) modified ultrasmall Fe3O4 nanoprobes have significant potential to improve the diagnostic accuracy and sensitivity in MRI. [ABSTRACT FROM AUTHOR]

The article offers information on a study according to which three-level spaser for next-generation luminescent nanoprobe. It mentions that development of modern biological and medical science highly depends on advanced luminescent probes. It states that delayed spasing dots (dsDs) have the potential to become new generation luminescent probes for super-multiplex biological analysis without disturbance from short lifetime background emission.

Development of various cost-effective multifunctional nanoprobes for efficient targeted molecular imaging of tumors remains a great challenge in medicine. Herein, we report a simple method of forming folic acid-targeted multifunctional gold nanoparticles via cost-effective cysteamine as a template for tumor molecular computed tomography (CT) imaging technique. The formed multifunctional cysteamine-folic acid conjugated gold nanoparticles (FA-Cys-AuNPs) were characterized via different techniques. Colony assay, hematoxylin and eosin (H&E), MTT, and flow cytometry analysis were used to evaluate the cytocompatibility of the particles. We showed that the formed FA-Cys-AuNPs with an Au core size of ~15 nm are non-cytotoxic in a given concentration range and revealed greater X-ray attenuation intensity than iodine-based contrast agent under the same concentration of the active element. At 80 kVp, FA-Cys-AuNPs enable 1.77–times greater contrast per unit mass compared with iodine at a concentration of 2000 μg/ml, and importantly, the developed FA-Cys-AuNPs can be used as a contrast media for targeted CT imaging of folic acid receptor-expressing cancer cells in vitro. CT values of the targeted cells were 2-times higher than that of non-targeted cells at 80 kVp. These findings propose that the designed FA-Cys-AuNPs can be used as a promising contrast agent for molecular CT imaging. This data can be also considered for the application of gold nanostructures in radiation dose enhancement where nanoparticles with high X-ray attenuation are applied. [ABSTRACT FROM AUTHOR]

The article describes the process of locating failures in current semiconductor device nodes using electron beam induced current (EBIC), electron beam absorbed current (EBAC) or resistive contrast imaging, current imaging and nanoprobing techniques. It presents cases of failure analysis including the locating of resistor chain defects, characterization of the electrical impact caused by increased substrate leakage, and back end of line open issue on copper plating recipe development wafer.

In this report, a novel T 1 /T 2 dual modal nanoprobe based on highly efficient and bioinspired melanin dots (M-dots) with directly loading gadolinium (Gd-M-dots) for magnetic resonance imaging (MRI) is described. In vitro and in vivo investigations have revealed that Gd-M-dots showed nontoxicity and good biocompatibilitity. Gd-M-dots relaxivity values on 3 T were determined to be r 1  = 23.4 and r 2  = 123.3 mM −1 s −1 , which were much higher than both Gd-DTPA ( r 1  = 5.1, r 2  = 6.2 mM −1 s −1 ) and Fe-M-dots ( r 1  = 1.2, r 2  = 2.1 mM −1 s −1 ). For in vivo MRI, after injection of Gd-M-dots, simultaneous T 1 and T 2 contrast enhancement have been observed in the MRI of mice abdomen and mice bearing U87MG tumors. Furthermore, all the veins showed high signal intensity on T 1 - weighted MRI and remained for 2 h. Overall, in vitro and in vivo studies indicate that Gd-M-dot with high r 1 relaxivity and r 2 relaxivity has high potential to be a promising nanoprobe for MR venography and molecular imaging. [ABSTRACT FROM AUTHOR]

A real-time quartz crystal microbalance (QCM) cytosensor based on a signal recovery strategy was first developed for in-situ and continuous monitoring of multiple cell membrane glycoproteins. In this work, gold nanoparticles (AuNPs) were linked with ligands to fabricate ligand-functionalized mass nanoprobes with signal amplification for increasing monitoring sensitivity. The mass nanoprobes bound to cell surface could be eluted with glycine-hydrochloric acid buffer, which led to a quick recovery of resonance frequency. Using the strategy, folate receptors (FR), CD44 molecule and epidermal growth factor receptor (EGFR) on cell membrane as the models were monitored continuously. The quantification result of MDA-MB-231 cells showed a range of linearity of 3.0 × 10 4 to 1.0 × 10 6 cells and a detection limit of 5.0 × 10 3 cells. Furthermore, the multianalyte cytosensor exhibited three sensitive and recoverable frequency shifts during continuous monitoring for in-situ and continuous evaluation of the expression levels of FR, CD44 and EGFR on cell membrane, which exhibited that the average numbers of molecules of FR, CD44 and EGFR per MDA-MB-231 cell were 0.5 × 10 6 , 0.2 × 10 6 and 1.4 × 10 5 with the relative standard deviation of 4.8%, 4.5% and 5.1%, respectively. Compared with monolithic multichannel QCM, the multianalyte cytosensor based on a single microbalance could not only exclude acoustic interference but also reduce instrumental cost. This work provided a simple and efficient QCM cytosensor for in-situ and continuous monitoring of multiple cell membrane glycoproteins that offered a new avenue for early diagnosis of cancer. [ABSTRACT FROM AUTHOR]

Nowadays, in order to improve the diagnostic accuracy of the disease, more and more contrast agents have been applied in the clinical imaging modalities. A combination of nanotechnology with optical, computed X-ray tomography (CT), and magnetic resonance imaging (MRI) has great potential to improve disease diagnosis and therapy. Herein, we developed a novel multimodal contrast agent for deep-tissue bioimaging based on PEGylated Mn 2+ doped NaLuF 4 :Yb/Er nanoparticles (PEG-UCNPs). The multimodal nanoprobes have revealed the intensely red upconversion luminescence emission for deep-tissue upconversion luminescence (UCL) imaging. Moreover, Owing to the high longitudinal relaxivity, the PEG-UCNPs can be used as T 1 -weighted MRI contrast agents. Additionally, with the high X-ray mass absorption coefficient of Lu 3+ , the novel nanoprobes are appropriate for CT imaging. With integration the high paramagnetic property, superior X-ray mass absorption coefficient and excellent upconversion luminescence in one system, the multimodal nanoprobes can provide a unique opportunity for MRI, CT and UCL imaging. More importantly, modification with PEG endows the novel nanoprobes with high biocompatibility, which would bring more opportunities for the biomedical applications in clinic. [ABSTRACT FROM AUTHOR]

We present an efficient carbon quantum dots (CQDs)-modified silver nanoparticles (AgNPs) (CQDs-AgNPs) as turn-on fluorescence nanoprobe for monitoring hydrogen sulfide (H 2 S) in brain microdialysate. The fluorescence of the CQDs-AgNPs probe can be selectively and sensitively turned on by H 2 S due to the formation of Ag S bonds between AgNPs and H 2 S and breaking of the Ag N bond between AgNPs and CQDs. Density functional theory (DFT)/time-dependent density functional theory (TD-DFT) investigation were thoroughly conducted on the electronic structures, absorption and emission spectra of CQDs-AgNPs complex as well as the sensing mechanism for hydrogen sulfide. The CQDs-AgNPs fluorescent probe illustrates a wide linear detection range towards H 2 S from 1 to 1900 nM with the detection limit of ∼0.4 nM. This improved sensitivity, lower limit, along with the high selectivity and fast response toward H 2 S, makes this CQDs-AgNPs complex successfully monitor H 2 S basal level in rats without exogenous stimulation, which was calculated to be 3.08 ± 0.10 μM (n = 3). This novel fluorescence probe provides an assay for direct detection of H 2 S in the cerebral systems and contributes to understand the physiological function and molecular mechanisms of endogenous H 2 S. [ABSTRACT FROM AUTHOR]

In the work, a novel fabrication method for homogeneous and sharp nanoprobe array on (111) silicon wafer is presented. The specific spatial structure of {111} planes and the unique anisotropic etching mechanism on (111) wafer were utilized to form a size controllable funnel-neck structure. A highly downscaled size-reduction technology is developed for precise size control. Followed with a self-limiting oxidation procedure, sharp and long needles can be made with precise size control requiring only a series of conventional processes (dry etching of silicon by DRIE, anisotropic wet etching by potassium hydroxide solution and thermal-oxidation-based tip sharpening). The fabricated probe, whose tip’s diameter is less than 30 nm, can potentially have broad application to cell research. [ABSTRACT FROM AUTHOR]

As one of the emerging inorganic graphene analogues, two-dimensional titanium carbide (Ti3C2) nanosheets have attracted extensive attention in recent years because of their remarkable structural and electronic properties. Herein, a sensitive and selective nanoprobe to fluorescently probe phospholipase D activity was developed on the basis of an ultrathin Ti3C2 nanosheets-mediated fluorescence quenching effect. Ultrathin Ti3C2 nanosheets with ~1.3 nm in thickness were synthesized from bulk Ti3AlC2 powder by a two-step exfoliation procedure and further modified by a natural phospholipid that is doped with rhodamine B-labeled phospholipid (RhB-PL-Ti3C2). The close proximity between RhB and Ti3C2 leads to efficient fluorescence quenching (>95%) of RhB by energy transfer. Phospholipase D-catalyzed lipolysis of the phosphodiester bond in RhB-PL results in RhB moving away from the surface of Ti3C2 nanosheets and subsequent fluorescence recovery of RhB, providing a fluorescent "switch-on" assay for the phospholipase D activity. The proposed nanoprobe was successfully applied to quantitatively determine phospholipase D activity with a low limit of detection (0.10 U L[sup -1]) and to measure its inhibition. Moreover, in situ monitoring and imaging the activity of phospholipase D in living cells were achieved using this biocompatible nanoprobe. These results reveal that Ti3C2 nanosheets-based probes exhibit great potential in fluorometric assay and clinical diagnostic applications. [ABSTRACT FROM AUTHOR]

Hybrid gold nanoparticles covalently coated with 5,10,15- p -(ω-methoxy polyethyleneoxyphenyl)-20- p -(hydroxyphenyl) porphyrin molecules, having about 16 repetitive units in each of its poly(oxyethylene) branches, were synthesized and characterized by UV–vis, fluorescence, dynamic light scattering (DLS), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) measurements. Their [H 3 O + ] optical sensing behavior was also studied and compared to that of the similar water-soluble star polymer 5,10,15,20-tetrakis p -[ω-methoxypoly(ethyleneoxy)]phenylporphyrin. Changing the pH of a solution, the UV–vis spectra of the PEGylate porphyrin gold nanoparticles conjugates showed the gradual disappearance of the Soret band at 424 nm and the progressive increase of a new band at 451 nm. Upon acidic titration, also the fluorescence spectra showed a gradual disappearing of the fluorescence at 654 nm. Moreover, an unusual B-Band red-shift and a decreasing of porphyrin core basicity were observed for this porphyrin bonded to the gold nanoparticle surfaces. To rationalize these phenomena an in silico TD-DFT calculation study was then conducted. For its properties, this new system: can be used in both aqueous and organic media; by a simple treatment of the solution at 80 °C under N 2 gas stream the starting Soret signals can be recovered; the nanoparticles can be eventually removed from the solution by centrifugation. [ABSTRACT FROM AUTHOR]

Herein we combine the enzyme-nanoprobe induced biomineralization of cupric subcarbonate with a sensitive copper chromogenic reaction to develop an ultrasensitive colorimetric immunosensing method. The nanoprobe was prepared through the surface assembly of signal antibody and high-content urease on the nanocarrier of gold nanoparticle (Au NP). Upon sandwich immunoreaction at a magnetic bead (MB)-based immunosensing platform, the analyte of carcinoembryonic antigen and the Au NP/urease nanoprobe were quantitatively captured onto the MB surface successively to form an immunocomplex. The enzyme reaction of the nanoprobe resulted in the catalyzed hydrolysis of the urea substrate to produce large amounts of OH − and HCO 3 − . These ions were further combined with added Cu 2+ to form the biomineralization of cupric subcarbonate rapidly on the immunocomplex. Based on the acid-release of Cu 2+ from the biomineralized products for the chromogenic reaction, a red complex was obtained and employed for the ultrasensitive colorimetric signal transduction. Under the optimum conditions, a linear range over five orders of magnitude was obtained with a low detection limit of 0.45 pg/mL. In addition, this method features low cost, rapid and convenient operation as well as satisfactory reproducibility, stability and accuracy. It thus owns great potentials for practical applications. [ABSTRACT FROM AUTHOR]