Development of a DNAzyme-Driven Fluorescent Light-Up Aptasensor for Label-Free Detection of Multiple lncRNAs.

Long noncoding RNAs (lncRNAs) act as the dynamic regulatory molecules that control the expression of genes and affect numerous biological processes, and their dysregulation is associated with tumor progression. Herein, we develop a fluorescent light-up aptasensor to simultaneously measure multiple lncRNAs in living cells and breast tissue samples based on the DNAzyme-mediated cleavage reaction and transcription-driven synthesis of light-up aptamers. When target lncRNAs are present, they can be recognized by template probes to form the active DNAzyme structures, initiating the T4 PNK-catalyzed dephosphorylation-triggered extension reaction to generate double-strand DNAs with the T7 promoter sequences. The corresponding T7 promoters can initiate the transcription amplification catalyzed by the T7 RNA polymerase to generate abundant Broccoli aptamers and malachite green aptamers, which can bind DFHBI-1T and MG to generate strong fluorescence signals. Taking advantage of the good selectivity of DNAzyme-mediated cleavage of lncRNAs, high amplification efficiency of T7 transcription-driven amplification reaction, and bright fluorescence of the RNA aptamer-fluorophore complex, this method exhibits high sensitivity with a detection limit of 21.4 aM for lncRNA HOTAIR and 18.47 aM for lncRNA MALAT1, and it can accurately measure multiple lncRNAs in both tumor cell lines and breast tissue samples, providing a powerful paradigm for biomedical research and early clinic diagnostics.

An intelligent Cu/ZIF-8-based nanodrug delivery system for tumor-specific and synergistic therapy via tumor microenvironment-responsive cascade reaction.

An intelligent nanodrug delivery system (Cu/ZIF-8@GOx-DOX@HA, hereafter CZGDH) consisting of Cu-doped zeolite imidazolate framework-8 (Cu/ZIF-8, hereafter CZ), glucose oxidase (GOx), doxorubicin (DOX), and hyaluronic acid (HA) was established for targeted drug delivery and synergistic therapy of tumors. The CZGDH specifically entered tumor cells through the targeting effect of HA and exhibited acidity-triggered biodegradation for subsequent release of GOx, DOX, and Cu2+ in the tumor microenvironment (TME). The GOx oxidized the glucose (Glu) in tumor cells to produce H2O2 and gluconic acid for starvation therapy (ST). The DOX entered the intratumoral cell nucleus for chemotherapy (CT). The released Cu2+ consumed the overexpressed glutathione (GSH) in tumor cells to produce Cu+. The generated Cu+ and H2O2 triggered the Fenton-like reaction to generate toxic hydroxyl radicals (·OH), which disrupted the redox balance of tumor cells and effectively killed tumor cells for chemodynamic therapy (CDT). Therefore, synergistic multimodal tumor treatment via TME-activated cascade reaction was achieved. The nanodrug delivery system has a high drug loading rate (48.3 wt%), and the three-mode synergistic therapy has a strong killing effect on tumor cells (67.45%).

Structurally Modulated Formation of Cyanine J-aggregates with Sharp and Tunable Spectra for Multiplexed Optoacoustic and Fluorescence Bioimaging.

J-aggregation brings intriguing optical and electronic properties to molecular dyes and significantly expands their applicability across diverse domains, yet the challenge for rationally designing J-aggregating dyes persists. Herein, we developed a large number of J-aggregating dyes from scratch by progressively refining structure of a common heptamethine cyanine. J-aggregates with sharp spectral bands (full-width at half-maximum ≤ 38 nm) are attained by introducing a branched structure featuring a benzyl and a trifluoroacetyl group at meso-position of dyes. Fine-tuning the benzyl group enables spectral regulation of J-aggregates. Analysis of single crystal data of nine dyes reveals a correlation between J-aggregation propensity and molecular arrangement within crystals. Some J-aggregates are successfully implemented in multiplexed optoacoustic and fluorescence imaging in animals. Notably, three-color multispectral optoacoustic tomography imaging with high spatiotemporal resolution is achieved, owing to the sharp and distinct absorption bands of the J-aggregates.

CRISPR/Cas12a-mediated DNA-AgNC label-free logical gate for multiple microRNAs' assay.

CRISPR/Cas system has been widely applied in the assay of disease-related nucleic acids. However, it is still challenging to use CRISPR/Cas system to detect multiple nucleic acids at the same time. Herein, we combined the preponderance of DNA logic circuit, label-free, and CRISPR/Cas technology to construct a label-free "AND" logical gate for multiple microRNAs detection with high specificity and sensitivity. With the simultaneous input of miRNA-155 and miRNA-141, the logic gate starts, and the activation chain of Cas12a is destroyed; thus, the activity is inhibited and the fluorescence of the signal probe ssDNA-AgNCs is turned on. The detection limit of this method for simultaneous quantitative detection of double target is 84 fmol/L (S/N = 3). In this "AND" logic gate, it is only necessary for the design of a simple DNA hairpin probe, which is inexpensive and easy, and since this method involves only one signal output, the data processing is very simple. What is more important, in this strategy two types of microRNAs can be monitored simultaneously by only using CRISPR/Cas12a and a type of crRNA, which offers a new design concept for the exploitation of single CRISPR/Cas system for multiple nucleic acid assays.

Large stokes shift and near-infrared fluorescent probe for bioimaging and evaluating the HClO in an rheumatoid arthritis mouse model.

It is crucial to identify aberrant HClO levels in living things since they pose a major health risk and are a frequent reactive oxygen species (ROS) in living organisms. In order to detect HClO in various biological systems, we created and synthesized a near-infrared fluorescent probe with an oxime group (-C = N-OH) as a recognition unit. The probe DCMP1 has the advantages of fast response (10 min), near-infrared emission (660 nm), large Stokes shift (170 nm) and high selectivity. This probe DCMP1 not only detects endogenous HClO in living cells, but also enables further fluorescence detection of HClO in living zebrafish. More importantly, it can also be used for fluorescence imaging of HClO in an rheumatoid arthritis mouse model. This fluorescent probe DCMP1 is anticipated to be an effective tool for researching HClO.

Proximity-Induced Bipedal DNA Walker for Accurately Visualizing microRNA in Living Cancer Cell.

DNA walker, a type of dynamic DNA device that is capable of moving progressively along prescribed walking tracks, has emerged as an ideal and powerful tool for biosensing and bioimaging. However, most of the reported three-dimensional (3D) DNA walker were merely designed for the detection of a single target, and they were not capable of achieving universal applicability. Herein, we reported for the first time the development of a proximity-induced 3D bipedal DNA walker for imaging of low abundance biomolecules. As a proof of concept, miRNA-34a, a biomarker of breast cancer, is chosen as the model system to demonstrate this approach. In our design, the 3D bipedal DNA walker can be generated only by the specific recognition of two proximity probes for miRNA-34a. Meanwhile, it stochastically and autonomously traveled on 3D tracks (gold nanoparticles) via catalytic hairpin assembly (CHA), resulting in the amplified fluorescence signal. In comparison with some conventional DNA walkers that were utilized for living cell imaging, the 3D DNA walkers induced by proximity ligation assay can greatly improve and ensure the high selectivity of bioanalysis. By taking advantage of these unique features, the proximity-induced 3D bipedal DNA walker successfully realizes accurate and effective monitoring of target miRNA-34a expression levels in living cells, affording a universal, valuable, and promising platform for low-abundance cancer biomarker detection and accurate identification of cancer.

MOF derivatization of multifunctional nanozyme: Peroxidase-like catalytic activity combined with magnetic solid phase extraction for colorimetric detection of Hg2.

Nanozyme-based colorimetric sensing has drawn immense attention due to the rapid development of nanozyme in recent years. However, the selectivity of nanozyme-based colorimetric sensing greatly limits its subsequent practical application. It is well known that sample pretreatment can not only improve selectivity by eliminating the sample matrix interference, but also improve sensitivity by enriching trace targets. Based on the easy facile surface modification properties of nanozyme, we rationally designed nanozyme combined with sample pretreatment for colorimetric biosensing, through separation and enrichment, thereby improving the selectivity and sensitivity of the nanozyme colorimetric biosensing. As a proof of concept, the detection of Hg2+ by nanozyme-based colorimetric sensing was used as an example. Magnetic peroxidase-like nanozyme Fe3S4 was designed and synthesized. The selectivity is improved by the specific adsorption of S-Hg bond and the interference elimination after magnetic separation. In addition, the sensitivity is improved by magnetic solid-phase extraction enrichment. Our established colorimetric sensing based on Fe3S4 nanozyme integrated sample pretreatment with an enrichment factor of 100 and the limit of detection (LOD) is 26 nM. In addition, this strategy was successfully applied to detect Hg2+ in environmental water samples. Overall, the strategy showed good selectivity and sensitivity, providing a new practical method for the application of nanozyme-based biosensing in sample pretreatment.

Dihydroxanthene-based monoamine oxidase A-activated photosensitizers for photodynamic/photothermal therapy of tumors.

Small molecule photosensitizers for combined in vivo tailored cancer diagnostics and photodynamic/photothermal therapy are desperately needed. Monoamine oxidase A (MAO-A)-activated therapeutic and diagnostic compounds provide great selectivity because MAO-A can be employed as a biomarker for associated Tumors. In order to screen photosensitizers with photodynamic therapeutic potential, we have created a range of near-infrared fluorescent molecules in this work by combining dihydroxanthene parent with various heterocyclic fluorescent dyes. The NIR fluorescent diagnostic probe, DHMQ, was created by combining the screened fluorescent dye matrices with the propylamino group, which is the recognition moiety of MAO-A, based on the oxidative deamination mechanism of the enzyme. This probe has a low toxicity level and can identify MAO-A precisely. It has the ability to use fluorescence imaging on mice and cells to track MAO-A activity in real-time. It has strong phototoxicity and can produce singlet oxygen when exposed to laser light. The temperature used in photothermal imaging can get up to 50 °C, which can harm tumor cells permanently and have a positive phototherapeutic impact on tumors grown from SH-SY5Y xenograft mice. The concept of using MAO-A effectively in diseases is expanded by the MAO-A-activated diagnostic-integrated photosensitizers, which offer a new platform for in vivo cancer diagnostics and targeted anticancer treatment.

Acid-Triggered Degradation of Three-In-One Ag2S Quantum Dots for In Situ Ratiometric NIR-II Fluorescence Imaging-Guided Ion/Gas Combination Therapy.

Smart theranostic nanoprobes with the integration of multiple therapeutic modalities are preferred for precise diagnosis and efficient therapy of tumors. However, it remains a big challenge to arrange the imaging and two or more kinds of therapeutic agents without weakening the intended performances. In addition, most existing fluorescence (FL) imaging agents suffer from low spatiotemporal resolution due to the short emission wavelength (<900 nm). Here, novel three-in-one Ag2S quantum dot (QD)-based smart theranostic nanoprobes were proposed for in situ ratiometric NIR-II FL imaging-guided ion/gas combination therapy of tumors. Under the acidic tumor microenvironment, three-in-one Ag2S QDs underwent destructive degradation, generating toxic Ag+ and H2S. Meanwhile, their FL emission at 1270 nm was weakened. Upon introduction of a downconversion nanoparticle (DCNP) as the delivery carrier and NIR-II FL reference signal unit, the formed Ag2S QD-based theranostic nanoprobes could achieve precise diagnosis of tumors through ratiometric NIR-II FL signals. Also, the generated Ag+ and H2S enabled specific ion/gas combination therapy toward tumors. By combining the imaging and therapeutic functions, three-in-one Ag2S QDs may open a simple yet reliable avenue to design theranostic nanoprobes.

Doping Engineering To Modulate Surface Plasmon Resonance and Enzyme-like Activities for Enhancing Photoacoustic Imaging-Guided Targeted Cancer Therapy in the Second Near-Infrared Window.

Biological imaging-guided targeted tumor therapy has been a soughtafter goal in the field of cancer diagnosis and treatment. To this end, we proposed a strategy to modulate surface plasmon resonance and endow WO3-x nanoparticles (NPs) with enzyme-like catalytic properties by doping Fe2+ in the structure of the NPs. Doping of the Fe2+ introduced oxygen vacancies into the structure of the NPs, inducing a red shift of the maximum absorption wavelength into the near-infrared II (NIR-II) region and enhancing the photoacoustic (PA) and photothermal properties of the NPs for more effective imaging-guided cancer therapy. Under NIR-II laser irradiation, the Fe-WO3-x NPs produced very strong NIR-II PA and photothermal effects, which significantly enhanced the PA imaging and photothermal treatment effects. On the other hand, Fe2+ in Fe-WO3-x could undergo Fenton reactions with H2O2 in the tumor tissue to generate ·OH for chemodynamic therapy. In addition, Fe-WO3-x can also catalyze the above reactions to produce more reactive oxygen species (ROS) and induce the oxidation of NADH to interfere with intracellular adenosine triphosphate (ATP) synthesis, thereby further improving the efficiency of cancer therapy. Specific imaging of tumor tissue and targeted synergistic therapy was achieved after ligation of a MUC1 aptamer to the surface of the Fe-WO3-x NPs by the complexing of -COOH in MUC1 with tungsten ions on the surface of the NPs. These results demonstrated that Fe-WO3-x NPs could be a promising diagnosis and therapeutic agent for cancer. Such a study opens up new avenues into the rational design of nanodiagnosis and treatment agents for NIR-II PA imaging and cancer therapy.

Rational design of nanozyme with integrated sample pretreatment for colorimetric biosensing.

Nanozymes have been widely used in the field of biosensing owing to their high stability, low cost, adjustable catalytic activity, and convenient modification. However, achieving high selectivity and sensitivity simultaneously in nanozyme-based colorimetric sensing remains a major challenge. Nanozymes are nanomaterials with enzyme-simulating activity that are often used as solid-phase adsorbents for sample pretreatment. Our design strategy integrated sample pretreatment function into the nanozyme through separation and enrichment, thereby improving the selectivity and sensitivity of nanozyme-based colorimetric biosensing. As a proof-of-concept, glucose was used as the model analyte in this study. A phenylboric acid-modified magnetic nanozyme (Cu/Fe3O4@BA) was rationally designed and synthesized. Selectivity was enhanced by boronate-affinity specific adsorption and the elimination of interference after magnetic separation. In addition, magnetic solid-phase extraction enrichment was used to improve the sensitivity. A recovery rate of more than 80% was reached when the enrichment factor was 50. The synthesized magnetic Cu/Fe3O4@BA was recyclable at least five times. The proposed method exhibited excellent selectivity and sensitivity, simple operation, and recyclability, providing a novel and practical strategy for designing multifunctional nanozymes for biosensing.

Lysosome passivation triggered by silver nanoparticles enhances subcellular-targeted drug therapy.

Frequently, subcellular-targeted drugs tend to accumulate in lysosomes after cellular absorption, a process termed the lysosomal trap. This accumulation often interferes with the drug's ability to bind to its target, resulting in decreased efficiency. Existing methods for addressing lysosome-induced drug resistance mainly involve improving the structures of small molecules or enveloping drugs in nanomaterials. Nonetheless, these approaches can lead to changes in the drug structure or potentially trigger unexpected reactions within organisms. To address these issues, we introduced a strategy that involves inactivating the lysosome with the use of Ag nanoparticles (Cy3.5@Ag NPs). In this method, the Cy3.5@Ag NPs gradually accumulate inside lysosomes, leading to permeation of the lysosomal membrane and subsequent lysosomal inactivation. In addition, Cy3.5@Ag NPs also significantly affected the motility of lysosomes and induced the occurrence of lysosome passivation. Importantly, coincubating Cy3.5@Ag NPs with various subcellular-targeted drugs was found to significantly increase the efficiency of these treatments. Our strategy illustrates the potential of using lysosomal inactivation to enhance drug efficacy, providing a promising therapeutic strategy for cancer.

A Macrophage Membrane-Coated Cu-WO3-x-Hydro820 Nanoreactor for Treatment and Photoacoustic/Fluorescence Dual-Mode Imaging of Inflamed Liver Tissue.

A disease-targeting nanoplatform that integrates imaging with therapeutic activity would facilitate early diagnosis, treatment, and therapeutic monitoring. To this end, a macrophage membrane-coated Cu-WO3-x-Hydro820 (CWHM) nanoreactor was prepared. This reactor was shown to target inflammatory tissues. The reactive oxygen species (ROS) such as H2O2 and ·OH in inflammatory tissues can react with Hydro820 in the reactor to form the NIR fluorophore IR820. This process allowed photoacoustic/fluorescence dual-mode imaging of H2O2 and ·OH, and it is expected to permit visual diagnosis of inflammatory diseases. The Cu-WO3-x nanoparticles within the nanoreactor shown catalase and superoxide enzyme mimetic activity, allowing the nanoreactor to catalyze the decomposition of H2O2 and ·O2- in inflammatory cells of hepatic tissues in a mouse model of liver injury, thus alleviating the oxidative stress of damaged liver tissue. This nanoreactor illustrates a new strategy for the diagnosis and treatment of hepatitis and inflammatory liver injury.

Improving the sensing sensitivity of silver nanoparticle-based colorimetric biosensors from the point of salt.

The sensing sensitivity was improved for silver nanoparticles (AgNPs)-based colorimetric biosensors by using the most suitable salt to induce AgNPs aggregation. As for the salt composed of low-affinity anion and monovalent cation, the cation-dependent charge screening effect was the driving force for AgNPs aggregation. Apart from the charge screening effect, both the bridging of multivalent cation to the surface ligand of AgNP and the interaction between anion and Ag contributed to inducing AgNPs aggregation. Considering the higher aggregation efficiency of AgNPs resulted in a narrower sensing range, salt composed of low-affinity anion and monovalent cation was recommended for AgNPs-based colorimetric analysis, which was confirmed by fourfold higher sensitivity of DNA-21 detection using NaF than NaCl. This work inspires further thinking on improving the sensing performance of metal nanomaterials-based sensors from the point of colloidal surface science.

Self-Feedback DNAzyme Motor for Cascade-Amplified Imaging of mRNA in Live Cells and In Vivo.

DNA motors have attracted extensive interest in biosensing and bioimaging. However, the amplification capacity of the existing DNA motor systems is limited since the products from the walking process are unable to feedback into the original DNA motor systems. As a result, the sensitivities of such systems are limited in the contexts of biosensing and bioimaging. In this study, we report a novel self-feedback DNAzyme motor for the sensitive imaging of tumor-related mRNA in live cells and in vivo with cascade signal amplification capacity. Gold nanoparticles (AuNPs) are modified with hairpin-locked DNAzyme walker and track strands formed by hybridizing Cy5-labeled DNA trigger-incorporated substrate strands with assistant strands. Hybridization of the target mRNA with the hairpin strands activates DNAzyme and promotes the autonomous walking of DNAzyme on AuNPs through DNAzyme-catalyzed substrate cleavage, resulting in the release of many Cy5-labeled substrate segments containing DNA triggers and the generation of an amplified fluorescence signal. Moreover, each released DNA trigger can also bind with the hairpin strand to activate and operate the original motor system, which induces further signal amplification via a feedback mechanism. This motor exhibits a 102-fold improvement in detection sensitivity over conventional DNAzyme motors and high selectivity for target mRNA. It has been successfully applied to distinguish cancer cells from normal cells and diagnose tumors in vivo based on mRNA imaging. The proposed DNAzyme motor provides a promising paradigm for the amplified detection and sensitive imaging of low-abundance biomolecules in vivo.

Rational design of cuprofullerene bipyridine nanozyme with high peroxidase-like activity for colorimetric sensing of bleomycin.

The high catalytic activity of Cu-based nanozymes mainly depends on the efficient Fenton-like reaction of Cu+/ H2O2, but Cu+ cannot exist stably. Trying to find a material that can stably support Cu+ while promoting the electron cycle of Cu2+/Cu+ still faces serious challenges. C60 is expected to be an ideal candidate to solve this problem due to its unique structure and rich physicochemical properties. Here, we designed and synthesized a C60-doped Cu+-based nanozyme (termed as C60-Cu-Bpy) by loading high catalytic active site Cu+ onto C60 and coordinating with 2,2'-bipyridine (Bpy). The single crystal diffraction analysis and a series of auxiliary characterization technologies were used to demonstrate the successful preparation of C60-Cu-Bpy. Significantly, the C60-Cu-Bpy exhibited superior peroxidase-like activity during the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Then, the catalytic mechanism of C60-Cu-Bpy as peroxidase was elucidated in detail, mainly benefiting from the dual function of C60. On the one hand, C60 acted as a carrier to directly support Cu+, which has the ability to efficiently decompose H2O2 to produce reactive oxygen species. The other was that C60 acted as an electron buffer, contributing to promoting the Cu2+/Cu+ cycle to facilitate the reaction. Furthermore, a colorimetric sensor for the quantitative analysis of bleomycin was established based on the principle of bleomycin specific inhibition of C60-Cu-Bpy peroxidase-like activity, with satisfactory results in practical samples. This study provides a new strategy for the direct synthesis of Cu+-based nanozymes with high catalytic performance.

Elongation and Ligation-Mediated Differential Coding for Label-Free and Locus-Specific Analysis of 8-Oxo-7,8-dihydroguanine in DNA.

Oxidative DNA damage is closely associated with the occurrence of numerous human diseases and cancers. 8-Oxo-7,8-dihydroguanine (8-oxoG) is the most prevalent form of DNA damage, and it has become not only an oxidative stress biomarker but also a new epigenetic-like biomarker. However, few approaches are available for the locus-specific detection of 8-oxoG because of the low abundance of 8-oxoG damage in DNA and the limited sensitivity of existing assays. Herein, we demonstrate the elongation and ligation-mediated differential coding for label-free and locus-specific analysis of 8-oxoG in DNA. This assay is very simple without the involvement of any specific labeled probes, complicated steps, and large sample consumption. The utilization of Bsu DNA polymerase can specifically initiate a single-base extension reaction to incorporate dATP into the opposite position of 8-oxoG, endowing this assay with excellent selectivity. The introduction of cascade amplification reaction significantly enhances the sensitivity. The proposed method can monitor 8-oxoG with a limit of detection of 8.21 × 10-19 M (0.82 aM), and it can identify as low as 0.001% 8-oxoG damage from a complex mixture with excessive undamaged DNAs. This method can be further applied to measure 8-oxoG levels in the genomic DNA of human cells under diverse oxidative stress, holding prospect potential in the dynamic monitoring of critical 8-oxoG sites, early clinical diagnosis, and gene damage-related biomedical research.

A dual-core 3D DNA nanomachine based on DNAzyme positive feedback loop for highly sensitive MicroRNA imaging in living cells.

A double 3D DNA walker nanomachine by DNAzyme self-driven positive feedback loop amplification for the detection of miRNA was constructed. This method uses two gold nanoparticles as the reaction core, and because of the spatial confinement effect the local concentration of the reactants increase the collision efficiency was greatly improved. Meanwhile, the introduction of positive feedback loop promotes the conversion efficiency. In presence of miRNA-21, a large amount of DNAzyme was released and hydrolyze the reporter probe, resulting the recovery of fluorescence signal. The linear range for miRNA-21 is 0.5-60 pmol/L, and the detection limit is 0.41 pmol/L (S/N = 3). This nanomachine has been successfully used for accurate detection of miRNA-21 expression levels in cell lysates. At the same time, it can enter cells for intracellular miRNA-21 fluorescence imaging, distinguishing tumor cells from normal cells. This combination of in vitro detection and imaging analysis of living cells can achieve the goal of jointly detecting cancer markers through multiple pathways, providing new ideas for early diagnosis and screening of diseases.

Bimetallic FeOx-TiO2@Carbon hybrid structure materials with notable peroxidase enzyme mimics applied to one-step colorimetric detection of glucose.

FeOx-TiO2@Carbon hybrid structure materials (FeOx-TiO2@CHs) with high peroxidase (POD)-like activity have been prepared by one-pot hydrothermal method. Based on the excellent POD activity of FeOx-TiO2@CHs, one pot colorimetric detection for glucose was constructed by using TMB as substrate with the synergistic reaction of glucose oxidase; the linear range and the limit of detection (LOD) are 25 ~ 1000 and 1.77 µM, respectively. Using this method, the glucose in serum real samples was detected with satisfactory results, and the results are consistent with that of the glucometer method in the hospital. The recovery in diabetic and artificial urine samples was 95.71 ~ 104.67% and 99.01 ~ 103.16%, respectively. The mechanism of the catalytic colorimetric reaction was also investigated by multiple measurements, and the results indicated that superoxide anions (O2•-) between FeOx-TiO2@CHs and substrate play a main role, but a small quantity of hydroxyl radical •OH and singlet oxygen 1O2 is also generated simultaneously. The one-pot reaction method is simple and fast; the detection process only requires a simple mixing, which is suitable for application in special environment.

Monoamine oxidase B activatable red fluorescence probe for bioimaging in cells and zebrafish.

A real-time and specific for the detection of Monoamine Oxidase B (MAO-B) to investigate the MAO-B-relevant disease development and treatment process is urgently desirable. Here, we utilized MAO-B to catalyze the conversion of propylamino groups to aldehyde groups, which was then quickly followed by a ß-elimination process to produce fluorescent probes (FNJP) that may be used to detect MAO-B in vitro and in vivo. The FNJP probe possesses unique properties, including favorable reactivity (Km = 10.8 µM), high cell permeability, and NIR characteristics (λem = 610 nm). Moreover, the FNJP probe showed high selectivity for MAO-B and was able to detect endogenous MAO-B levels from a mixed population of NIH-3 T3 and HepG2 cells. MAO-B expression was found to be increased in cells under lipopolysaccharide-stimulated cellular oxidative stress in neuronal-like SH-SY5Y cells. In addition, the visualization of FNJP for MAO-B activity in zebrafish can be an effective tool for exploring the biofunctions of MAO-B. Considering these excellent properties, the FNJP probe may be a powerful tool for detecting MAO-B levels in living organisms and can be used for accurate clinical diagnoses of related diseases.