High-fidelity imaging of drug-induced acute gastritis by using a fluorescent and photoacoustic dual-modal probe with good stability in stomach acid.

In consideration of deep tissue imaging and signal fidelity, fluorescent-photoacoustic (PA) dual-modal probes are much more desirable. However, dual-modal imaging of gastritis using molecular probes remains a challenge due to the harsh gastric acid environment in the stomach. Based on the positive correlation between gastritis and cell viscosity, stomach acid-stable and viscosity-activated probes could potentially diagnose gastritis. As a proof of concept, herein, a fluorescent and photoacoustic dual-modal probe (named WSP-1) is revealed for the imaging of drug-induced acute gastritis in vivo. WSP-1 exhibits viscosity-dependent fluorescence emission and photoacoustic signals. A rotatable C-C single bond is incorporated into the D-π-A structure of WSP-1, which could facilitate the formation of the twisted intramolecular charge transfer (TICT) state in a low-viscosity environment (weak fluorescence/PA signal) and the intramolecular charge transfer (ICT) state in a high-viscosity environment (strong fluorescence/PA signal). WSP-1 has demonstrated the capability to target mitochondria and can be utilized to monitor the viscosity enhancement of cells during inflammation. Most importantly, WSP-1 exhibits good optical and structural stability in gastric acid. By leveraging these desirable features of WSP-1, we have achieved fluorescent and 3D photoacoustic in situ imaging of drug-induced acute gastritis following oral administration of WSP-1.

Twisted Intramolecular Charge Transfer-Based Viscosity-Responsive Probe Reveals Lysosomal Degradation Process of Endocytosed Foreign Bodies.

The optimization of nanomedicines requires a thorough understanding of nanocarrier attrition during lysosome-mediated biological processes. Real-time monitoring of endocytosis provides valuable insights into the lysosomal effects on nanocarriers and the release of nanodrugs. We report the development of a coresponsive probe that detects changes in the spatial viscosity of the intracellular domain caused by lysosomal degradation of foreign bodies. The probe, based on a benzofuro[2,3-d]pyrimidine structure, exhibits torsional intramolecular charge transfer (TICT) and responds to ambient viscosity changes with a sensitive fluorescence intensity. The antidiffused fluorescence transition of the probe in the spatially restricted domain serves as a key indicator for real-time monitoring. When encapsulated with diverse foreign bodies and emitted into macrophages by endocytosis, the probe forms nanoparticles. Lysosomes uptake these materials for intracellular digestion, causing alterations in the aggregation or depolymerization state of the nanoparticles, leading to viscosity changes manifested by the probe's fluorescence. By studying the spatial viscosity changes caused by lysosomal degradation of foreign bodies, our monitoring strategy contributes to understanding the digestion or escape capabilities of potential pharmaceutical-carrying nanocarriers, providing guidelines to design more effective nanocarriers that navigate lysosomal degradation to achieve precise drug payloads and release.

Spatially confined dual-emission nanoprobes assembled from silicon nanoparticles and gold nanoclusters for ratiometric biosensing.

Gold nanoclusters (AuNCs) possess weak intrinsic fluorescence, limiting their sensitivity in biosensing applications. This study addresses these limitations by developing a spatially confined dual-emission nanoprobe composed of silicon nanoparticles (SiNPs) and AuNCs. This amplified and stabilized fluorescence mechanism overcomes the limitations associated with using AuNCs alone, achieving superior sensitivity in the sensing platform. The nanoprobe was successfully employed for ratiometric detection of bleomycin (BLM) in serum samples, operating at an excitation wavelength of 365 nm, with emission wavelengths at 480 nm and 580 nm. The analytical performance of the system is distinguished by a linear detection range of 0-3.5 µM, an impressive limit of detection (LOD) of 35.27 nM, and exceptional recoveries ranging from 96.80 to 105.9%. This innovative approach significantly enhances the applicability and reliability of AuNC-based biosensing in complex biological media, highlighting its superior analytical capabilities.

Integrating a Copper-Histidine Brace in a Mimetic Nanozyme Streamlines the Tyrosinase Recognition Moiety to Achieve Chiral Differentiation.

Designing artificial mimetic enzymes with high activity/selectivity to replace chiral bioenzymes is of great interest in the development of chiral materials consisting of molecules, enantiomers, that exist in two forms as mirror images of one another but cannot be superimposed. In this study, the chiral catalytic structural unit was streamlined from tyrosinase to integrate a mimetic nanozyme. The chiral amino acid l-histidine, as the chiral binding/recognition site, and the active metal site Cu were coupled (Cu@l-His) to create a copper-histidine brace with enantioselective catalytic ability to tyrosinol enantiomers. Results of kinetic parameters and activation energies confirmed the excellent peroxidase-like activity with a preference of Cu@l-His to l-tyrosinol. Such a preference could be attributed to the structurally oriented copper-histidine brace with a stronger affinity and catalytic activity to l-tyrosinol. By accurately evaluating chiral recognition units derived from bioenzymes, stable and superior chiral mimetic nanoenzymes could be constructed in a more straightforward and simplified manner, and they could also be extended to the reconstruction of diverse chiral enzymes.

Dual-Aptamer Recognition of DNA Logic Gate Sensor-Based Specific Exosomal Proteins for Ovarian Cancer Diagnosis.

Clinical diagnosis of ovarian cancer lacks high accuracy due to the weak selection of specific biomarkers along with the circumstance biomarkers localization. Clustering analysis of proteins transported on exosomes enables a more precise screening of effective biomarkers. Herein, through bioinformatics analysis of ovarian cancer and exosome proteomes, two coexpressed proteins, EpCAM and CD24, specifically enriched, were identified, together with the development of an as-derived dual-aptamer targeted exosome-based strategy for ovarian cancer screening. In brief, a DNA ternary polymer with aptamers targeting EpCAM and CD24 was designed to present a logic gate reaction upon recognizing ovarian cancer exosomes, triggering a rolling circle amplification chemiluminescent signal. A dynamic detection range of 6 orders of magnitude was achieved by quantifying exosomes. Moreover, for clinical samples, this strategy could accurately differentiate exosomes from healthy persons, other cancer patients, and ovarian cancer patients, enabling promising in situ detection. By accurately selecting biomarkers and constructing a dual-targeted exosomal protein detection strategy, the limitation of insufficient specificity of traditional protein markers was circumvented. This work contributed to the development of exosome-based prognosis monitoring in ovarian cancer through the identification of disease-specific exosome protein markers.

Metal-organic framework-based ratiometric point-of-care testing for quantitative visual detection of nitrite.

Nitrite (NO2-) is categorized as a carcinogenic substance and is subjected to severe limitations in water and food. To safeguard the public's health, developing fast and convenient methods for determination of NO2- is of significance. Point-of-care testing (POCT) affords demotic measurement of NO2- and shows huge potential in future technology beyond those possible with traditional methods. Here, a novel ratiometric fluorescent nanoprobe (Ru@MOF-NH2) is developed by integrating UiO-66-NH2 with tris(2,2'-bipyridyl)ruthenium(II) ([Ru(bpy)3]2+) through a one-pot approach. The special diazo-reaction between the amino group of UiO-66-NH2 and NO2- is responsible for the report signal (blue emission) with high selectivity and the red emission from [Ru(bpy)3]2+ offers the reference signal. The proposed probe shows obviously distinguishable color change from blue to red towards NO2- via naked-eye. Moreover, using a smartphone as the detection device to read color hue, ultra-sensitive quantitative detection of NO2- is achieved with a low limit of detection at 0.6 µΜ. The accuracy and repeatability determined in spiked samples through quantitative visualization is in the range of 105 to 117% with a coefficient of variation below 4.3%. This POCT sensing platform presents a promising strategy for detecting NO2- and expands the potential applications for on-site monitoring in food and environment safety assessment.

An ATMND/SGI based three-way junction ratiometric fluorescent probe for rapid and sensitive detection of bleomycin.

In this work, we developed a rapid and sensitive label-free ratiometric fluorescent (FL) probe for the detection of bleomycin (BLM). The probe consists of a DNA sequence (D6) and two fluorophore groups, 2-amino-5,6,7-trimethyl-1,8-naphthalene (ATMND) and SYBR Green I (SGI). The D6 sequence could be folded into a three-way junction structure containing a C-C mismatch position in the junction pocket. The unique "Y" structure not only could entrap ATMND in the mismatch pocket with high affinity, leading to FL quenching at 408 nm, but also embed SGI in the grooves of the double-stranded portion, resulting in FL enhancement at 530 nm. In the presence of BLM-Fe(II), the "Y" structure of D6 was destroyed due to the specific cleavage of the BLM recognition site, the 5'-GT-3' site in D6. This caused the release of ATMND and SGI and thus the ratiometric signal change of FL enhancement by ATMND and FL quenching by SGI. Under optimal conditions, the ratiometric probe exhibited a linear correlation between the intensity ratio of F408/F530 and the concentration of BLM in the range of 0.5-1000 nM, with a detection limit of 0.2 nM. In addition, the probe was applied to detect BLM in human serum samples with satisfactory results, indicating its good clinical application potential.

Ratiometric fluorescence determination of alkaline phosphatase activity based on carbon dots and Ce3+-crosslinked copper nanoclusters.

A new ratiometric fluorescent probe for efficient determination of ALP was developed. The probe was constructed by combining Ce3+-crosslinked copper nanoclusters (Ce3+-CuNCs) which exhibit the aggregation-induced emission (AIE) feature with carbon dots (CDs). The introduction of phosphate (Pi) induced the generation of CePO4 precipitation, resulting in significant decrease of fluorescence emission of CuNCs at 634 nm. At the same time, the fluorescence of CDs at 455 nm was obviously enhanced, thus generating ratiometric fluorescence response. Based on the fact that the hydrolysis of pyrophosphate (PPi) by ALP can produce Pi, the CD/Ce3+-CuNCs ratiometric probe was successfully used to determine ALP. A good linear relationship between the ratiometric value of F455/F634 and ALP concentrations ranging from 0.2 to 80 U·L- 1 was obtained, with a low detection limit of 0.1 U·L- 1. The ratiometric responses of the probe resulted in the visible fluorescence color change from orange red to blue with the increase of ALP concentration. The smartphone-based RGB recognition of the fluorescent sample images was used for ALP quantitative determination. A novel ratiometric fluorescent system based on Ce3+-CuNCs with AIE feature and CDs were constructed for efficient detection of ALP.

Responsive calcium-derived nanoassemblies induce mitochondrial disorder to promote tumor calcification.

Physiological calcification of the treated tumor area is considered to be a predictor of good prognosis. Promoting tumor calcification by inducing mitochondrial metabolic disorder and destroying calcium equilibrium has a potential inhibitory effect on tumor proliferation. Here, by promoting calcification by inducing mitochondrial dysfunction combined with triggering a surge of reactive oxygen species, we construct a bioresponsive calcification initiator, termed CaP-AA, using CaHPO4 covalently doped l-ascorbic acid. CaHPO4 releases Ca2+ within the cytoplasm of tumor cells to trigger calcium overload. Meanwhile, exogenous l-ascorbic acid indirectly enhances metabolic balance disruption via pro-oxidant effects. Such Ca2+ overload increases the likelihood of tumor calcification in vivo for tumor inhibition by perturbing mitochondrial homeostasis. The introduction of responsive calcium sources that would, in turn, trigger intratumoral calcification mediated by perturbing mitochondrial homeostasis would be an effective regulatory strategy for tumor therapy.

Synergistic Incorporation of Two ssDNA Activators Enhances the Trans-Cleavage of CRISPR/Cas12a.

CRISPR/Cas12a has been believed to be powerful in molecular detection and diagnostics due to its amplified trans-cleavage feature. However, the activating specificity and multiple activation mechanisms of the Cas12a system are yet to be elucidated fully. Herein, a "synergistic activator effect" is discovered, which supports an activation mechanism that a synergistic incorporation of two short ssDNA activators can promote the trans-cleavage of CRISPR/Cas12a, while either of them is too short to work independently. As a proof-of-concept example, the synergistic activator-triggered CRISPR/Cas12a system has been successfully harnessed in the AND logic operation and the discrimination of single-nucleotide variants, requiring no signal conversion elements or other amplified enzymes. Moreover, a single-nucleotide specificity has been achieved for the detection of single-nucleotide variants by pre-introducing a synthetic mismatch between crRNA and the "helper" activator. The finding of "synergistic activator effect" not only provides deeper insight into CRISPR/Cas12a but also may facilitate its expanded application and power the exploration of the undiscovered properties of other CRISPR/Cas systems.

Activatable Near-Infrared Fluorescent and Photoacoustic Dual-Modal Probe for Highly Sensitive Imaging of Sulfatase In Vivo.

Sulfatase is an important biomarker closely associated with various diseases. However, the state-of-the-art sulfatase probes are plagued with a short absorption/emission wavelength and limited sensitivity. Developing highly sensitive fluorescent probes for in vivo imaging of sulfatase remains a grand challenge. Herein, for the first time, an activatable near-infrared fluorescence/photoacoustic (NIRF/PA) dual-modal probe (Hcy-SA) for visualizing sulfatase activity in living cells and animals is developed. Hcy-SA is composed of a sulfate ester moiety as the recognition unit and a NIR fluorophore hemicyanine (Hcy-OH) as the NIRF/PA reporter. The designed probe exhibits a rapid response, excellent sensitivity, and high specificity for sulfatase detection in vitro. More importantly, cells and in vivo experiments confirm that Hcy-SA can be successfully applied for PA/NIRF dual-modal imaging of sulfatase activity in living sulfatase-overexpressed tumor cells and tumor-bearing animals. This probe can serve as a promising tool for sulfatase-related pathological research and cancer diagnosis.

Compute-and-Release Logic-Gated DNA Cascade Circuit for Accurate Cancer Cell Imaging.

Accurate identification of cancer cells is an essential prerequisite for cancer diagnosis and subsequent effective curative interventions. The logic-gate-assisted cancer imaging system that allows a comparison of expression levels between biomarkers, rather than just reading biomarkers as inputs, returns a more comprehensive logical output, improving its accuracy for cell identification. To fulfill this key criterion, we develop a compute-and-release logic-gated double-amplified DNA cascade circuit. This novel system, CAR-CHA-HCR, consists of a compute-and-release (CAR) logic gate, a double-amplified DNA cascade circuit (termed CHA-HCR), and a MnO2 nanocarrier. CAR-CHA-HCR, a novel adaptive logic system, is designed to logically output the fluorescence signals after computing the expression levels of intracellular miR-21 and miR-892b. Only when miR-21 is present and its expression level is above the threshold CmiR-21 > CmiR-892b, the CAR-CHA-HCR circuit performs a compute-and-release operation on free miR-21, thereby outputting enhanced fluorescence signals to accurately image positive cells. It is capable of comparing the relative concentrations of two biomarkers while sensing them, thus allowing accurate identification of positive cancer cells, even in mixed cell populations. Such an intelligent system provides an avenue for highly accurate cancer imaging and is potentially envisioned to perform more complex tasks in biomedical studies.

Promoting sensitive colorimetric detection of hydroquinone and Hg2+ via ZIF-8 dispersion enhanced oxidase-mimicking activity of MnO2 nanozyme.

Reducing the agglomeration and improving the dispersibility in water of two-dimensional (2D) nanozymes is one of the effective ways to improve their enzyme-like activity. In this work, we propose a method by constructing zeolitic imidazolate framework-8 (ZIF-8)-dispersed 2D manganese-based nanozymes to achieve the specific regulated improvement of oxidase-mimicking activity. By in-situ growth of manganese oxides nanosheets of MnO2(1), MnO2(2) and Mn3O4 on the surface of ZIF-8, the corresponding nanocomposites of ZIF-8 @MnO2(1), ZIF-8 @MnO2(2), and ZIF-8 @Mn3O4 were prepared at room temperature. The Michaelis-Menton constant measurements indicated that ZIF-8 @MnO2(1) exhibits best substrate affinity and fastest reaction rate for 3,3',5,5'-tetramethylbenzidine (TMB). The ZIF-8 @MnO2(1)-TMB system was exploited to detection of trace hydroquinone (HQ) based on the reducibility of phenolic hydroxyl groups. In addition, by employing the fact that the cysteine (Cys) with the excellent antioxidant capacity can bind the Hg2+ based on the formation of "S-Hg2+" bonds, the ZIF-8 @MnO2(1)-TMB-Cys system was applied to detection of Hg2+ with high sensitivity and selectivity. Our findings not only provide a better understanding of the relationship between dispersion of nanozyme and enzyme-like activity, but also provide a general method for the detection of environmental pollutants using nanozymes.

A protein enzyme-free strategy for fluorescence detection of single nucleotide polymorphisms using asymmetric MNAzymes.

To establish protein enzyme-free and simple approach for sensitive detection of single nucleotide polymorphisms (SNPs), the nucleic acid amplification reactions were developed to reduce the dependence on protein enzymes (polymerase, endonuclease, ligase). These methods, while enabling highly amplified analysis for the short sequences, cannot be generalized to long genomic sequences. Herein, we develop a protein enzyme-free and general SNPs assay based on asymmetric MNAzyme probes. The multi-arm probe (MNAzyme-9M-13) with two asymmetric recognition arms, containing a short (9 nt) and a long (13 nt) arm, is designed to detect EGFR T790 M mutation (MT). Owing to the excellent selectivity of short recognition arm, MNAzyme-9M-13 probe can efficiently avoid interferences from wild-type target (WT) and various single-base mutations. Through a one-pot mixing, MNAzyme-9M-13 probe enables the sensitive detection of MT, without protein enzyme or multi-step operation. The calculated detection limit for MT is 0.59 nM and 0.83%. Moreover, this asymmetric MNAzyme strategy can be applied for SNPs detection in long genomic sequences as well as short microRNAs (miRNAs) only by changing the low-cost unlabeled recognition arms. Therefore, along with simple operation, low-cost, protein enzyme-free and strong versatility, our asymmetric MNAzyme strategy provides a novel solution for SNPs detection and genes analysis.

ssDNA-C3N4 conjugates-based nanozyme sensor array for discriminating mycotoxins.

A nanozyme sensor array based on the ssDNA-distensible C3N4 nanosheet sensor elements for discriminating multiple mycotoxins commonly existing in contaminated cereals has been explored. The sensor array exploited (a) three DNA nonspecific sequences (A40, T40, C40) absorbed on the C3N4 nanosheets as sensor elements catalyzing the oxidation of TMB; (b) the presence of five mycotoxins affected the catalytic activity of three nanozymes with various degrees. The parameter (A0-A) was employed as the signal output to obtain the response patterns for different mycotoxins with the same concentration where A0 and A were the absorption peak values at 650 nm of oxTMB in the absence and presence of target mycotoxins, respectively. After the raw data was subjected to principal component analysis, 3D canonical score plots were obtained. The sensor array was capable of separating five mycotoxins from each other with 100% accuracy even if the concentration of the mycotoxins was as low as 1 nM. Moreover, the array performed well in discriminating the mycotoxin mixtures with different ratios. Importantly, the practicality of this sensor array was demonstrated by discriminating the five mycotoxins spiking in corn-free samples in 3D canonical score plots, validating that the sensor array can act as a flexible detection tool for food safety. A nanozyme sensor array was developed based on the ssDNA-distensible C3N4 NSs sensor elements for discriminating muitiple mycotoxins.

Silver ion-regulated ratiometric fluorescence assay for alkaline phosphatase detection based on carbon dots and o-phenylenediamine.

In this work, a novel silver ion (Ag+)-regulated ratiometric fluorescence method for the effective and sensitive determination of alkaline phosphatase (ALP) was established based on carbon dots (CDs) and o-phenylenediamine (OPD). OPD can be oxidized by Ag+ to generate fluorescent 2, 3-diaminophenazine (DAP). Thus, based on inner-filter effect (IFE) or/and fluorescence resonance energy transfer (FRET) between CDs and DAP, the CDs-Ag+-OPD system can generate dual-emission at 454 nm and 570 nm respectively when excited at 360 nm. The introduction of ascorbic acid (AA) can react with Ag+ to produce dehydroascorbic acid (DHAA), which inhibits the generation of DAP, resulting in the fluorescence decrease at 570 nm and fluorescence recovery of CDs at 454 nm. Meanwhile, DHAA can react with OPD to generate quoxaline (QX), which emits strong blue fluorescence at 440 nm, further inhibiting the IFE or/and FRET between CDs and DAP. An obvious ratiometric fluorescence response was observed with the increase of the concentration of AA introduced. Due to the fact that AA can be generated by the enzyme catalysis reaction between ALP and 2-phospho-l-ascorbic acid (AAP), the CDs-Ag+-OPD ratiometric system was applied to the determination of ALP successfully. The ratiometric fluorescence value of F454/F570 increases with increasing ALP concentration, with a linear range of 0.2 to 40 U/L and detection limit of 0.1 U/L. In addition, the CDs-Ag+-OPD ratiometric system was successfully applied to the detection of ALP in human serum samples.

Long-wavelength emission carbon dots as self-ratiometric fluorescent nanoprobe for sensitive determination of Zn2.

A novel ratiometric fluorescence nanoprobe based on long-wavelength emission carbon dots (CDs) was designed for high sensitive and selective detection of Zn2+. The CDs were conveniently prepared by a one-step solvothermal treatment of formamide and glutathione (GSH). Under single excitation wavelength (420 nm), the obtained CDs exhibit three emission peaks at 470, 650, and 685 nm, respectively. For the long-wavelength emission region of the CDs, the fluorescence at 685 nm can be quenched with different levels upon the addition of most metal ions. However, the presence of Zn2+ not only results in the fluorescence quenching at 685 nm effectively but also enhances at 650 nm remarkably, which may be due to the formation of CD-Zn2+ chelate complex inducing the dispersion of CDs aggregates and changes in the group distribution on the surface of CDs. Taking the advantage of the unique fluorescence response induced by Zn2+, the prepared CDs were successfully employed as nanoprobe for self-ratiometric fluorescence determination of Zn2+ with F650/F685 as signal output. A good linear relationship in the concentration range 0.01 to 2 µM, and a detection limit as low as 5.1 nM has been obtained. The ratiometric nanoprobe was successfully applied to  Zn2+ determination  in human serum samples.

A DNAzyme-based normalized fluorescence strategy for direct quantification of endogenous zinc in living cells.

Taking the maximum fluorescence of an identical fluorophore as a reference, a DNAzyme-based normalized strategy is developed to unify the output signals under external interferences. This makes it possible to directly quantify endogenous zinc in living cells by in situ fluorescence imaging, implying promising potential in fundamental study and early disease diagnosis.

Combination of pipette tip solid phase extraction and high performance liquid chromatography for determination of plant growth regulators in food samples based on the electrospun covalent organic framework/polyacrylonitrile nanofiber as highly efficient sorbent.

Facile and sensitive determination of plant growth regulators (PGRs) in food samples is important but still remains great challenge. Herein, a pipette tip solid phase extraction (PT-SPE) method was developed for fast and sensitively detecting PGRs. The PT-SPE adsorbent was prepared by integrating a novel covalent organic framework (COF) of schiff base network 3 (SNW-3) and polyacrylonitrile (PAN) through electrospinning. The SNW-3 can easily adsorb PGRs with high special affinity through electrovalent bands between the ammonium ions of SNW-3 and the carboxy groups of PGRs. The polymer of PAN acts as scaffold material for SNW-3, which can lower seepage pressure hence accelerates adsorption/desorption kinetics. By combination with HPLC-DAD, a satisfactory method was successfully developed for simultaneous determination of ten PGRs in watermelon. Good analytical performances were achieved with this proposed method, including good linearity (5-500 ng/mL) with high correlation coefficients (R ≥ 0.9981), low limits of detection (S/N = 3, 0.24-3.19 ng/mL) and limits of quantification (S/N = 10, 1.65-5.72 ng/mL), satisfactory precision (intra-day RSDs ≤ 2.7%, inter-day RSDs ≤ 3.7%), and high accuracy (recovery: 82.8-113.0%). The method developed in this study shows high potential for design of high target-affinity adsorbents for food sample preparing.

A novel ratiometric fluorescence nanoprobe for sensitive determination of uric acid based on CD@ZIF-CuNC nanocomposites.

A novel ratiometric fluorescence nanoprobe based on carbon dots (CDs) and Cu nanoclusters (CuNCs) was designed for the label-free determination of uric acid (UA). The metal-organic framework (MOF) encapsulated CuNCs (ZIF-CuNC), and nitrogen-doped CDs can self-assemble into well-defined spherical nanocomposites (CD@ZIF-CuNC) due to physical adsorption. Under the excitation wavelength of 360 nm, the CD@ZIF-CuNC nanocomposites exhibit two evident intrinsic emissions peaked at 460 nm (CDs) and 620 nm (ZIF-CuNC), respectively. In the presence of H2O2, the fluorescence of CD@ZIF-CuNC at 620 nm is quenched remarkably within 1 min, while little effect on the emission at 460 nm is observed. Therefore, taking the fluorescence at 620 nm as the report signal and 460 nm as the reference signal, ratiometric quantitative determination of H2O2 was achieved with a linear range of 1-100 µM and a detection limit of 0.30 µM. The CD@ZIF-CuNC nanoprobe was successfully applied to the determination of UA that is catalyzed by uricase to produce H2O2, obtaining the linear range of 1-30 µM and the detection limit of 0.33 µM. Eventually, this strategy has been successfully applied to the determination of UA in human urine samples. A novel and convenient CDs@ZIF-CuNCs-based nanoplatform was constructed for sensitive ratiometric fluorescence determination of UA.