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Long-term and excessive use of tetracycline hydrochloride (TC) can lead to its accumulation in the environment, which can cause water contamination, bacterial resistance, and food safety problems. 2,6-Pyridine dicarboxylic acid (DPA) is a major biomarker of Bacillus anthracis spores, and its rapid and sensitive detection is of great significance for disease prevention and counter-terrorism. A bifunctional ratiometric fluorescent nanoprobe has been fabricated to detect DPA and TC. 3,5-dicarboxyphenylboronic acid (BOP) was intercalated into layered europium hydroxide (LEuH) by the ion-exchange method and exfoliated into nanosheets as a fluorescent nanoprobe (PNP). DPA and TC could significantly enhance the red fluorescence of Eu3+ through the antenna effect under different excitation wavelengths, while the fluorescence of BOP can be used as a reference based on the constant emission intensity, realizing ratiometric detection. A low limit of detection (LOD) for the target (DPA: 9.7 nM, TC: 21.9 nM) can be achieved. In addition, visual detection of DPA and TC was realized using color recognition software based on the obvious color changes. This is the first ratiometric fluorescent nanoprobe based on layered rare-earth hydroxide (LRH) for the detection of DPA and TC simultaneously, which opens new ideas in the design of multifunctional probes.

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Chromium is widely recognized as a significant pollutant discharged into the environment by various industrial activities. The toxicity of this element is dependent on its oxidation state, making speciation analysis crucial for monitoring the quality of environmental water and assessing the potential risks associated with industrial waste. This study introduces a single-well fluorometric sensor that utilizes orange emissive thioglycolic acid stabilized CdTe quantum dots (TGA-QDs) and blue emissive carbon dots (CDs) to detect and differentiate between various chromium species, such as Cr (III) and Cr (VI) (i.e., CrO42- and Cr2O72-). The variations of fluorescence spectra of the proposed probe upon chromium species addition were analyzed using machine learning techniques such as linear discriminant analysis and partial least squares regression as a classification and multivariate calibration technique, respectively. Linear discriminant analysis (LDA) demonstrated exceptional accuracy in differentiating single-component and bicomponent samples. Additionally, the findings from the partial least squares regression (PLSR) showed that the sensor created has strong linearity within the 1.0-100.0, 1.0-100.0, and 0.1-15 µM range for Cr2O72-, CrO42-, and Cr3+, respectively. Furthermore, appropriate detection limits were successfully achieved, which were 2.6, 2.9, and 0.7 µM for Cr2O72-, CrO42-, and Cr3+, respectively. Ultimately, the successful capability of the sensing platform in the identification and quantification of chromium species in environmental water samples provides innovative insights into general speciation analytics.

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BACKGROUNDS: Cancer is a highly fatal disease which is close relative of miRNA aberrant expression and apoptosis disorders. Elucidation of the therapeutic efficacy through investigating the changes in miRNA and apoptosis holds immense importance in advancing the development of miRNA-based precision therapy. However, it remains a challenge as how to visually evaluate the efficacy during protocol optimization of miRNA-based anticancer drugs at the cellular level. Therefore, exploring effective and noninvasive methods for real-time monitoring of therapeutic efficacy in living cells is of great significance. RESULTS: Herein, we reported a novel fluorescent nanoprobe COF-H1/H2-Peptide for visually evaluating drug efficacy in living cells through amplified imaging of low-abundant miRNA-221 with catalytic hairpin assembly (CHA) circle amplification, as well as simultaneous caspase-3 imaging. With strong stability and good biocompatibility, this newly fabricated amplified nanoprobe showed high sensitivity and specificity for the detection of miRNA-221 and caspase-3, and the limit of detection (LOD) of miRNA-221 was as low as 2.79 pM. The fluorescent imaging results showed that this amplified nanoprobe could not only detect caspase-3 in living cells, but also effectively detect low levels of miRNA-221 with increasing anticancer drug concentration and treatment time. The smart nanoprobe had effective performance for optimizing miRNA-based drug treatment schedules by dual-color fluorescence imaging. SIGNIFICANCE: This nanoprobe combined CHA amplified detection of intracellular miRNA-221 and synchronous apoptosis imaging, with excellent sensitivity for the detection of cellular low-level miRNA, enabling the realization of real-time assessment of the efficacy of miRNA-based therapy in living cells. This work presents a promising approach for revealing the regulatory mechanisms between miRNAs and apoptosis in cancer occurrence, development, and treatment.

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Trimesic acid and o-phenylenediamine (OPD) were employed as precursors to synthesize yellow-green fluorescent carbon dots (Y-G-CDs) by solvothermal synthesis for the sensitive detection of Thiophanate-methyl (TM) in real agricultural products. The Y-G-CDs probe could specifically recognize the TM primarily through π-π stacking. Moreover, the fluorescence quenching of the probe was ultimately dominated by the PET effect, based on the interaction between the abundant carboxyl groups on the surface of the Y-G-CDs and the amino group of TM. A strong linear relationship between the fluorescence quenching of the probe and TM concentration in the range of 0-10 µmol/L was observed and the limit of detection (LOD) was calculated to be 50.7 nmol/L. Compared to the interference pesticides, the Y-G-CDs probe demonstrated exceptional selectivity toward TM, with satisfactory recoveries of 96.3 % - 104.2 % in spiked food samples. The Y-G-CDs probe enables simple pretreatment, cost-effective, and on-site detection of TM in fruits and vegetables with visual detection of the TM employing a smartphone-assisted sensing platform.

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A novel dual-emission fluorescent nanoprobe based on rare-earth nanosheets was fabricated to detect 2,6-pyridine dicarboxylic acid (DPA), which is the biomarker of Bacillus anthracis. 2-amino terephthalic acid (BDC-NH2) and surfactant sodium dodecyl sulfate (SDS) were co-intercalated into layered europium hydroxide (LEuH) to prepare the organic/inorganic composite, which was delaminated to obtain the rare-earth nanosheets. The ratio detection of DPA is possible due to the antenna effect between DPA and Eu3+. The nanoprobe shows high accuracy and sensitivity due to the large specific surface area of the rare-earth nanosheets. The limit of detection (LOD) is 4.4 nM for DPA in the range of 0-20 µM. In addition, a more convenient and faster smartphone-based visual detection platform was established based on the obvious color change. This work offers an effective way for developing visual sensing platforms, which opens a new path for designing fluorescent probes with superior sensing capabilities.

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Given that intricate toxicological profiles exist among different antibiotics and pose serious threats to the environment and human health, synchronous analysis of multiple residues becomes crucial. Sensor arrays show potential to achieve the above purpose, but it is challenging to develop easy-to-use and high-sensitivity tools because the state-of-the-art arrays often require more than one recognition unit and are monosignal dependent. Here we exquisitely designed a fluorescent nanoprobe (2-aminoterephthalic acid-anchored CdTe quantum dots with Eu3+ coordination, CdTe-ATPA-Eu3+) featuring triple emissions at the same excitation as the only element to fabricate a luminescent sensor array with ratiometric calculations for identifying multiple antibiotics. By taking tetracycline, chlortetracycline, doxycycline, oxytetracycline, penicillin G, and sulfamethoxazole as models, the six species exhibited distinguishable motivation or/and quenching impacts on the three emissions of CdTe-ATPA-Eu3+, which were employed as indicators to perform the ratiometric logical operation and further combined with pattern recognition analysis for multitarget determination. Evidently, such a design exhibits two advances: (1) with the triple-emission probe as the sole receptor requiring neither internal nor external adjustments, the fabricated array acts as an extremely facile tool for multianalyte detection; (2) the ratiometric calculations offer excellent sensitivity and reliability for high-performance determination. Consequently, accurate identification and quantification of individual antibiotics and their combinations at various levels were verified in both laboratory and practical matrices. Our work provides a new tool for simultaneously detecting multiple antibiotics, and it will inspire the development of advanced sensor arrays for multitarget analysis.

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In recent years, the application of nanoimaging technology on standardize tumor diagnosis has become a new research hotspot, especially nanoprobes. Our research group has synthesized a kind of nanocarrier, mPEG2000-GPLGIAGQ-DSPE, which has the characteristic of matrix metalloproteinase-2 (MMP2) sensitive ability in tumor microenvironment. Meanwhile, the encapsulation method is adopted to prepare MMP2-sensitive tumor-targeted prussian blue fluorescent nanoprobe with mPEG2000-GPLGIAGQ-DSPE as the carrier. On the one hand, this novel nanoprobe not only can effectively improve the solubility of prussian blue, but is non-toxic and safe for cells. On the other hand, octapeptide (GPLGIAGQ) in mPEG2000-GPLGIAGQ-DSPE nanocarrier can specifically respond to MMP2 in tumor cells to release prussian blue, and achieve targeted intelligent imaging of tumor cells.

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An "off-on" fluorescent nanoprobe for near-infrared multiphoton imaging of singlet oxygen has been developed. The nanoprobe comprises a naphthoxazole fluorescent unit and a singlet-oxygen-sensitive furan derivative attached to the surface of mesoporous silica nanoparticles. In solution, the fluorescence of the nanoprobe increases upon reaction with singlet oxygen both under one- and multiphoton excitation, with fluorescence enhancements up to 180-fold. The nanoprobe can be readily internalized by macrophage cells and is capable of imaging intracellular singlet oxygen under multiphoton excitation.

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As a major apurinic/apyrimidinic endonuclease and a redox signaling protein in human cells, APE1 plays a crucial role in cellular function and survival. The relationship between alterations of APE1 expression and subcellular localization and the initiation, development and treatment of various cancers has received extensive attention. However, comparing the in-vivo activity of APE1 in normal and cancerous breast live cells remains challenging due to the low efficiency of commonly used liposome transfection methods in delivering DNA substrate probes into human normal breast epithelial cells (MCF-10A). In this work, we develop a DNA/RNA hybrid-based small magnetic fluorescent nanoprobe (25 ± 3 nm) that can be taken up by various live cells under magnetic transfection. The D0/R-nanoprobe demonstrates an outstanding specificity toward APE1 and strong resistance to the cellular background interference. Using this nanoprobe, we are not only able to visualize the intracellular activity of APE1 in breast ductal carcinoma (MCF-7) live cells, but also demonstrate the APE1 activity in MCF-10A live cells for the first time. The method is then extended to observe the changes in APE1 levels in highly metabolically active neuroendocrine cells under normal conditions and severe attacks by reactive oxygen species in real-time. The fluorescent nanoprobe provides a useful tool for studying the dynamic changes of intracellular APE1 in normal or cancerous live cells. It also displays the potential for visible and controllable release of miRNA drugs within live cells for therapeutic purposes.

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Sensing Hg2+ is significant to protecting human health and environmental ecosystems, for its toxicity and genotoxicity. Here, highly stable fluorescent folic acid (FA)-protected Au nanoclusters (FA-AuNCs) were synthesized by optimizing the reactive parameters with high quantum yield of 34.7%. Main components of Au4L were confirmed by MALDI-TOF, and the electron-rich residues of FA shell enabled FA-AuNCs excellent photostability. FA-AuNCs exhibited sensitive response behavior to Hg2+ with a minimum detectability of 1.3 nM, and presented extreme effect to the detection of Hg2+ in real water. Notably, the cellular imaging and in-situ detection of Hg2+ in cells can be achieved visually. The high selectivity was attributed to the chemical bond formed between Au+ (4f145d10) and Hg2+ (4f145d10). And the internal filter effect and static quenching effect were proved triggering the quenching of FA-AuNCs. The ultra-stable FA-AuNCs provide a potential promising opportunity for the in-situ tracing Hg2+ from environmental and biological samples.

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Herein, a multi-mode visualization platform was initiated for in-situ detection of food dyes (FDs) by combining colorimetry, fluorometry and smartphone­based digital image analysis, in which water-dispersible quantum dots (QDs) were served as nanoprobes. Colorimetry was achieved by color comparison, while both fluorometry and fluorescence quantification were performed through inner filter effect (IFE)-induced fluorescence quenching, then color information (RGB & gray-scale values) of colorimetry and fluorometry was picked by a smartphone to reconstruct digitized alignments. Since IFE mechanism was concentration-dependent but did not rely on the interaction between fluorophore and quencher, the whole process of fluorescence response could be finished within 10 s, and both color gradients and fluorescence changes showed fine mappings to FDs concentrations in the range of 1.0 × 10-3∼0.035 mg/mL for brilliant blue, and 1.0 × 10-4∼0.1 mg/mL for Allura red and sunset yellow. As a proof-of-concept, the in-situ multi-mode visualization of these FDs in real beverages was experimentally proved to be highly feasible and reliable as compared with instrumental techniques like UV-vis/fluorescence spectrometry, along with HPLC. Finally, this strategy was extended to the multi-mode visualization of non-food dyes in three simulated wastewater samples with high credibility by contrast with the true additive amounts of model dyes.

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The continuously increasing flow of toxic heavy metals to the environment due to intensive industrial activity and tightening requirements with regard to the content of metal ions in drinking and discharged waters urges the development of affordable and sensitive devices to the field control of pollutants. Here, we report a new thiated Rhodamine-lactam probe for Hg2+ detection and demonstrate how its sensitivity can be increased via the incorporation of the probe molecules into the optically transparent siloxane-acrylate coatings on polymethyl methacrylate and, alternatively, into the water-dispersible light-harvesting FRET nanoparticles (NPs), in which dye cations are separated by fluorinated tetraphenylborate anions. We have shown that the optimization of the FRET NPs composition had allowed it to reach the antenna effect of ~300 and fabricate "off/on" sensor for Hg2+ ion determination in aqueous solutions with the detection limit of ~100 pM, which is far below the maximum permissible concentration (MPC) of mercury in drinking water recommended by the World Health Organization. Although this work is more proof-of-concept than a ready-to-use analytical procedure, the suggested approaches to fabrication of the FRET NPs based on the popular rhodamine-lactam platform can be used as a background for the development of low-cost portable sensing devices for the extra-laboratory determination of hazardous metal ions.

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Changed levels of intracellular peroxynitrite anion (ONOO-) are closely related to the occurrence and development of inflammation. Specific imaging of ONOO- at sites of inflammation can be of great significance not only for inflammation diagnosis but also for obtaining a deeper understanding of the role of ONOO- in inflammation. Therefore, there is an urgent need for constructing some reliable tools to study the relationship between ONOO- and inflammation in biosystems. In this work, we developed a robust high selectivity fluorescence turn-on nanoprobe (Rhb-ONOO) for inflammation-targeted imaging of ONOO-. The Rhb-ONOO was obtained by self-assembly of amphiphilic Rhb-ONOO, which was constructed by the condensation reaction of the hydrophobic, ONOO--response and deep red-emitting fluorophore (Rhb) with hydrophilic biopolymer glycol chitosan (GC). Rhb-ONOO showed rapid response towards ONOO- during 60 s, high sensitivity with 19-fold enhancement of fluorescence intensity ratio (I628/I0), and excellent selectivity towards ONOO- over other analytes as well as a good linear relationship was observed between the I628/I0 and the ONOO- concentration range 0-1 µM, with an excellent limit of detection (LOD) of 33 nM. Impressively, it was successfully employed Rhb-ONOO for ONOO- imaging in living inflammatory cells and drug-induced inflammatory mice, illustrating nanoprobe Rhb-ONOO has excellent potential for further study ONOO--related inflammatory diseases.

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Accurate and real-time reporting the freshness and quality of meat has far-reaching implications for safeguarding food safety and public health. Owing to the significant indicator role of H2S in meat spoilage, we here designed a ''dual-key-and-lock'' kind of H+-powered H2S-responsive ratiometric fluorescent nanoprobe BODIPY/Cy7Cl@HyNPs for precise and real-time evaluating the meat freshness. After incubation with spoilt meat, BODIPY/Cy7Cl@HyNPs was simultaneously initiated by the abnormal H+ and H2S acted as "dual-keys". As a result, the fluorescence emission of BODIPY/Cy7Cl@HyNPs at âˆ¼ 688 nm was enhanced, and the other emission at âˆ¼ 818 nm was quenched, thereby yielding a typical H+-powered ratiometric fluorescence response toward H2S in meat. In addition, we also successfully exploited BODIPY/Cy7Cl@HyNPs to achieve the real-time monitoring of the meat freshness during storage by measuring the changes of fluorescence signals and solution color.

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Quantitative detection of different types of reactive oxygen species (ROS) is vital for understanding the crucial roles of them in biological processes. However, few researches achieved the detection of multiple types of ROS with one probe until now. Given this, we designed and prepared fluorescent gold nanoclusters capped by dual ligand bovine serum albumin and lysozyme (BSA-LYS-AuNCs), which could detect 3 specific types of ROS based on its different fluorescent responses to H2O2, •OH and ClO-, respectively. The limit of detection (LOD) of H2O2, •OH, and ClO- was as low as 0.82 µM, 0.45 µM, and 0.62 µM. Moreover, as an important ROS type, ClO- was detected with high sensitivity and low LOD by BSA-LYS-AuNCs. It was also proved that the crosslinking of protein mainly contributed to the unique fluorescent characteristics of the probe exposing to ClO-. Furthermore, the fluorescent probe achieved the smart detection of hROS (including •OH and ClO-) and wROS (the form of H2O2) in the real sample, which could also been applied specifically to the detection of antioxidants, e.g. ascorbic acid. The gold nanoclusters developed have high potential for the smart detection of multiple ROS in the body fluid of organisms.

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Monitoring the content and structural transition of human serum albumin (HSA) is valuable for diagnosing hypoalbuminemia and albuminuria and elucidating its transport function, respectively. Herein, we developed a multifunctional and efficient nanoprobe based on the self-assembly of an amphiphilic aggregation-induced emission luminogen, TPNN, for HSA detection and structure monitoring. TPNN molecules formed loose self-assembly in aqueous media and emitted faint fluorescence due to vigorous intramolecular motion. In the presence of HSA, a remarkable fluorescence enhancement accompanied by dissociation of TPNN assembly was observed due to the site-specific binding of TPNN to the middle long-narrow pocket of HSA. This binding blocked the intramolecular motion while producing a sensitive, selective, fast and stable fluorescence turn-on response to HSA, making TPNN assembly suitable for the HSA assay. TPNN assemblies also showed superior selectivity to HSA than bovine serum albumin (BSA) due to the distinct binding modes, and enabled us to distinguish the two homologous proteins. Furthermore, the generated TPNN-HSA complex underwent stepwise fluorescence quenching in the presence of protein denaturants and proteases, which revealed the process and kinetics of HSA unfolding and cleavage. TPNN assembly provides a powerful tool for accurate quantification of HSA in serum and urine and real-time monitoring of HSA structural transition.

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Nitrogen and sulfur element co-decorated carbon nanodots (N,S-CDs) were synthesized by solid state hydrothermal method utilizing mercaptoacetic acid and melamine as the precursors. The obtained N,S-CDs had wonderful optical and chemical stability. The experimental results demonstrated that silver nanoparticles (AgNPs) could noticeably quench the fluorescence of N,S-CDs. The quenching of fluorescence signal from the presence of AgNPs may be attributed to inner filter effect. The crafted nanoprobe for sensing AgNPs was endowed with some specialties such as simplicity, excellent selectivity and sensitivity, environmental friendliness and low cost. The probe exhibited specific linearity from 0.024 to 1.77 nM, and was endowed a good limit of detection down to 0.022 nM. The experimental results demonstrated that the built probe could be an efficient tool for AgNPs detection and had a prospective application, and also provided a new direction for establishing innovative method for determining and monitoring pollutants from nanoparticles.

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In this work we presented novel strategy for increasing the performance of popular fluorescent probes on the basis of rhodamine-lactam platform. This strategy is based on the incorporation of probe molecules into the light-harvesting nanoparticles to pump modulated optical signal by Förster resonant energy transfer. Using the commercially available Cu2+ probe as a reference chemical, we have developed an efficient approach to significantly improve its sensing performance. Within obtained nanoparticles coumarin-30 nanoantenna absorbs excitation light and pumps incorporated sensing molecules providing bright fluorescence to a small number of emitters, while changing the probe-analyte equilibrium from liquid-liquid to solid-liquid significantly increased the apparent association constant, which together provided a ∼100-fold decrease in the detection limit. The developed nanoprobe allows highly sensitive detection of Cu2+ ions in aqueous media without organic co-solvents usually required for dissolution of the probe, and demonstrate compatibility with inexpensive fluorometers and the ability to detect low concentrations with the naked eye.

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MiRNA-targeted therapy is an active research field in precision cancer therapy. Studying the effect of miRNA expression changes on apoptosis is important for evaluating miRNA-targeted therapy and realizing personalized precision therapy for cancer patients. Here, a new fluorescent nanoprobe was designed for the simultaneous imaging of miRNA-21 and apoptotic protein caspase-3 in cancer cells by using gold nanoparticles as the core and polydopamine as the shell. Confocal imaging indicated that the nanoprobe could be successfully applied for in situ monitoring of miRNA regulation of apoptosis. This design strategy is critical for investigating the feasibility of miRNA-targeted therapy, screening new anti-cancer drugs targeting miRNA, and developing personalized treatment plans.

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Hydrogen sulfide (H2S) is an important signal molecule involved in intracellular activities. To understand the role of H2S in cellular physiological and pathological process, the development of sensitive and selective methods, especially biocompatible assays, for efficient monitoring the level of H2S is necessary. Herein, we modified novel rare earth element europium (EU) based fluorescent nanospheres with azide (-N3) based sensor to construct an ingenious ratiometric fluorescent nanoprobe EU-N3. This nanoprobe showed excellent water solubility and high biocompatibility for intracellular H2S accurate detection. Nanoprobe EU-N3 had two obvious emission peaks, the green fluorescence peak at 540 nm increased according to the increasing of H2S concentration and the red fluorescence peak at 616 nm was stable as ratiometric reference. The fluorescence intensity ratio (I540/I616) displayed good linear response (R = 0.99136) in H2S range of 0.5 âˆ¼ 30 µM. The analytes response assay demonstrated that the nanoprobe EU-N3 possessed a better specificity for H2S, compared with other 9 anions and 3 cations. The cell viability assay indicated the nanoprobe EU-N3 had an excellent biocompatibility. The cell imaging showed that the proposed nanoprobe could be applied for detecting the intracellular H2S changes accurately in live cells. Such nanoprobe provided a safe and accurate strategy for intracellular H2S detection, which is helpful for the real-time H2S visualization in the live cell activities.

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