Herein, a highly sensitive label-free multi-mode exonuclease III (Exo-III) assisted target recycling amplification detection method for Epstein-Barr virus (EBV) gene was developed based on super-stable CsPbBr3@SiO2 fluorescence composite, in which metal halide perovskite nanocrystals CsPbBr3 NCs were embedded in mesoporous silica nanospheres. The excellent stability and high fluorescence intensity of CsPbBr3@SiO2 fluorescence composite is helpful to improve the accuracy and sensitivity of detection. A duplex strand DNA complex (DSC) with a recognition DNA and a signal DNA was designed. The DSC can bind with EBV gene and activate Exo-III to digest recognition DNA from the 3 '-terminus, the released target DNA can participate in the next cycle to generate more signal DNA for signal amplification. The signal DNA containing G-rich sequences would fold into G-quadruplex when K+ was present, and form G-quadruplex/hemin DNAzymes with peroxidase-mimicking activity, which could accelerate the production of quinone imine by oxidizing 2,4-dichlorophenol (2,4-DP), 4-aminoantipyrine (4-AP) could react with the oxidation product of 2,4-DP, and the absorption at 510 nm would increase. The fluorescence of CsPbBr3@SiO2 would be quenched by quinone imine as a result of inner filter effect. Thus, the colorimetric and fluorometric sensing modes of EBV gene were realized with the limits of detection of 4.79 pM and 2.43 pM, respectively. Furthermore, a visualization detection of EBV gene was realized by combination of Image J software and smartphone. The sensing system was successfully employed to detect EBV gene in human saliva and serum samples with satisfied results.

In this work, a novel iron-nitrogen-carbon single-atom nanozyme (Fe-N800 SAzyme) with peroxidase-like activity was synthesized by doping Fe in zeolitic imidazolate frameworks (ZiF-8) and utilizing graphitic C3N4 (g-C3N4) as a nitrogen source in the pyrolysis process. Acetylcholine (ACh) was continuously oxidized by acetylcholinesterase (AChE) and choline oxidase (CHO) to generate H2O2 through an enzymatic cascade reaction. The interaction between Fe-N800 SAzyme and H2O2 led to the generation of reactive oxygen species (ROS) that could then oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to oxidized TMB (oxTMB), which exhibited an absorption peak at 650 nm. Lysozyme (LZ)-functionalized 5-methyl-2-thiouracil (MTU) gold/silver nanoclusters (Au/Ag/LZ-MTU), which exhibited a fluorescence peak at 610 nm, could be quenched by oxTMB through the inner filter effect (IFE). Dopamine (DA) was able to consume ROS and hinder the oxidation of TMB. Therefore, by monitoring the change of fluorescence at 610 nm and absorption at 650 nm, a dual signal fluorometric and colorimetric sensing platform for AChE and DA was established. The AChE activity was monitored through the variation of fluorescence (I610) or colorimetric (A650) intensity, which had a low limit of detection (LOD) of 0.057 U/L and 0.11 U/L, respectively. The fluorescence and colorimetric methods were also able to sensitively monitor the DA activity with a LOD of 0.83 mu M and 2.7 mu M, respectively. Finally, the developed method could satisfactorily quantify AChE and DA in human serum, whole blood, and DA hydrochloride injection samples.

As a natural polyphenolic compound, tannic acid (TA) exists in many foods and beverages. Excessive intake of TA can be harmful to human health. Herein, a dual-signal fluorometric and colorimetric sensing platform was established based on ssDNA modified copper manganese oxide nanosheets (CuMnO2 NSs@ssDNA) and copper doped silicon quantum dots (Cu-SiQDs) for the detection of TA. The CuMnO2 NSs@ssDNA nanocomplex could catalyze the oxidation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) by H2O2. The oxidation product exhibited a characteristic absorption peak at 652 nm and greatly quenched the fluorescence of Cu-SiQDs at 468 nm. The introduction of TA inhibited the catalytic oxidation of TMB, leading to recovered fluorescence and decreased absorbance. Therefore, TA could be determined on the basis of the variation of fluorescence and absorption signals. The limits of detection were 0.018 mu M and 0.077 mu M, respectively. Moreover, this proposed system was utilized for TA determination in real beverage samples with satisfactory results.

This work developed a sensitive fluorescence and colorimetric dual-channel sensing system for melatonin determination based on iron-cobalt oxide nanosheets (FeCo-ONSs) and gold nanoclusters (AuNCs). FeCo-ONSs exhibited excellent peroxidase (POD)-like activities, that could catalyze H2O2 to produce reactive oxygen species and further catalyze N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium (TOPS) to couple with 4-amino-antipyrine (4-AAP) to generate purple compounds (PCs), which had absorption at 549 nm. The generated PCs can quench the fluorescence of AuNCs at 577 nm via fluorescence resonance energy transfer (FRET). The process of the generation of purple compounds would be restrained in existence of melatonin due to its scavenging capacity for free radicals. As a consequence, the absorption at 549 nm decreased, while the fluorescence quenching of AuNCs was weakened, and emission intensity at 577 nm progressively recovered. The recovery of fluorescence and the decrease in absorption depended on the concentration of melatonin. Therefore, by employing fluorescence and colorimetric dual signal monitoring, the linear ranges of melatonin were 5-300 mu M and 5-800 mu M, and the LODs were 1.17 mu M and 2.13 mu M, respectively.

A novel dual-mode fluorometric and colorimetric sensing platform is reported for determining glutathione S-transferase (GST) by utilizing polyethyleneimine-capped silver nanoclusters (PEI-AgNCs) and cobalt-manganese oxide nanosheets (CoMn-ONSs) with oxidase-like activity. Abundant active oxygen species (O2•−) can be produced through the CoMn-ONSs interacting with dissolved oxygen. Afterward, the pink oxDPD was generated through the oxidation of colorless N,N-diethyl-p-phenylenediamine (DPD) by O2•−, and two absorption peaks at 510 and 551 nm could be observed. Simultaneously, oxDPD could quench the fluorescence of PEI-AgNCs at 504 nm via the inner filter effect (IFE). However, in the presence of glutathione (GSH), GSH prevents the oxidation of DPD due to the reducibility of GSH, leading to the absorbance decrease at 510 and 551 nm. Furthermore, the fluorescence at 504 nm was restored due to the quenching effect of oxDPD on decreased PEI-AgNCs. Under the catalysis of GST, GSH and1-chloro-2,4-dinitrobenzo (CDNB) conjugate to generate an adduct, initiating the occurrence of the oxidation of the chromogenic substrate DPD, thereby inducing a distinct colorimetric response again and the significant quenching of PEI-AgNCs. The detection limits for GST determination were 0.04 and 0.21 U/L for fluorometric and colorimetric modes, respectively. The sensing platform illustrated reliable applicability in detecting GST in real samples.

Multiple heteroatom doping is one of the effective strategies to tune the structure of carbon supports and enhance the catalytic performance of nanozymes. Herein, the carbon-based copper nanozyme with sulfur/nitrogen codoping (S/Cu-NC) was synthesized by one-step pyrolysis of Cu-doped ZIF-8 with thiourea encapsulated (Th/ Cu@ZIF-8). Benefiting from the synergy of binary heteroatoms and 3D porous structure, the obtained S/Cu-NC had more active sites and exhibited outstanding peroxidase-like activity. Subsequently, a dual-channel (colorimetric/fluorescent) detection method for melatonin was developed by selecting 3,3,5,5-tetramethylbenzidine (TMB) and thiamine as the substrates of S/Cu-NC, which was based on the free radical scavenging effect of melatonin. Furthermore, a simple and portable paper-based device was designed to realize the rapid detection of melatonin through color changes under ultraviolet light and daylight, and the limit of detection were 0.87 mu M and 1.42 mu M, respectively. This paper-based device was successfully applied to detect melatonin in two kinds of drug samples with satisfactory results.

Background: Due to that the higher activity of nanozymes would bring outstanding performance for the nanozyme-based biosensing strategies, great efforts have been made by researchers to improve the catalytic activity of nanozymes, and novel nanozymes with high catalytic activity are desired. Considering the crucial role in controlling blood glucose level, strategies like colorimetric and chemiluminescence to monitor alpha-glucosidase are developed. However, multi -mode detection with higher sensitivity was insufficient. Therefore, developing triple -mode detection method for alpha-glucosidase based on great performance nanozyme is of great importance. Results: In this work, a novel nanozyme Cu-BCN was synthesized by loading Cu on boron doped carbon substrate g-C 3 N 4 and applied to the colorimetric-fluorescent-smartphone triple -mode detection of alpha-glucosidase. In the presence of H 2 O 2 , Cu-BCN catalyzed the generation of 1 O 2 from H 2 O 2 , 1 O 2 subsequently oxidized TMB to blue colored oxTMB. In the presence of hydroquinone (HQ), the ROS produced from H 2 O 2 was consumed, inhibiting the oxidation of TMB, which endows the possibility of colorimetric and visual on -site detection of HQ. Further, due to that the fluorescence of Mg-CQDs at 444 nm could be quenched by oxTMB, HQ could also be quantified through fluorescent mode. Since alpha-glucosidase could efficiently hydrolyze alpha-arbutin into HQ, the sensitive detection of alpha-glucosidase was realized. Further, colorimetric paper -based device ( c -PAD) was fabricated for on site alpha-glucosidase detection. The LODs for alpha-glucosidase via three modes were 2.20, 1.62 and 2.83 U/L respectively, high sensitivities were realized. Significance: The nanozyme Cu-BCN possesses higher peroxidase-like activity by doping boron to the substrate than non -doped Cu-CN. The proposed triple -mode detection of alpha-glucosidase is more sensitive than most pre- vious reports, and is reliable when applied to practical sample. Further, the smartphone-based colorimetric paper -based analytical device ( c -PAD) made of simple materials could also detect alpha-glucosidase sensitively. The smartphone-based on -site detection provided a convenient, instrument -free and sensitive sensing method for alpha-glucosidase.

In this work, a novel and sensitive fluorescence sensing system for alkaline phosphatase (ALP) was constructed using a bifunctional copper metal-organic framework (Cu@MOF) nanozyme, which had excellent oxidasemimetic activity and fluorescence properties. Owing to the presence of 2-amino-1,4-benzenedicarboxylic acid (1,4-BDC-NH 2 ) ligand, Cu@MOF displays excellent fluorescence performance at 444 nm. Additionally, Cu 2 + endows the oxidase-like activity of Cu@MOF, which could trigger p-phenylenediamine (PPD) to be oxidized to a brown product (PPDox) and quench the photoluminescence of Cu@MOF through the inner filtration effect (IFE). As the preferential affinity of ATP for Cu 2 + , the catalytic activity of Cu@MOF was significantly reduced once ATP was added, thus PPD could not be oxidized and fluorescence was recovered. In the presence of ALP, ATP was hydrolyzed to adenosine and Pi, which allowed Cu@MOF to regain its catalytic activity and continued to catalyze the generation of PPDox. The fluorescence of Cu@MOF was therefore weakened once again. The ALP activity was directly proportional to the degree of decrease in fluorescence intensity. Thus, this novel fluorescence sensing strategy had a linear range of 0.5 -60 U/L and the limit of detection was 0.14 U/L. The established sensing method could also be used to for ALP inhibitors screening, and achieved satisfactory results in determining the level of ALP activity in human serum.

Herein, we successfully synthesized two-dimensional iron-doped carbon-based nanosheets (Fe-N800 CS) with catalase-like activity through doping Fe into Zn MOF and introducing graphitic C3N4 (g-C3N4). The interaction of the Fe-N800 CS with hydrogen peroxide could generated abundant reactive oxygen species (ROS) and further oxidize o-Phenylenediamine (OPD) to 2,3-diaminophenazine (DAP) which has constant fluorescence at 560nm. Ascorbic acid (AA) could be generated via the hydrolysis reaction between alkaline phosphatase (ALP) and ascorbic acid 2-phosphate (AAP). AA can be oxidized to dehy-droascorbic acid (DHA) by ROS, and then combined with OPD to generate 3-(1,2-dihydroxyethyl)furo[3,4b]-quinoxaline (QXD) with fluorescence at 440nm, which could increase as the concentration of AA enhanced. DHA could also be generated through oxidation of AA by ascorbate oxidase (AAO). Thus, by monitoring the fluorescence ratio (I560/I440), a ratiometric fluorescence biosensing platform for ALP and AAO was established with the linear ranges in 0.2-10 U/L and 1-60 U/L, respectively. The limit of detection for ALP and AAO were 0.12 U/L and 0.59 U/L. Furthermore, the biosensing platform was successfully applied for the detection of ALP and AAO activity in human serum samples. This work provides a potential tool for future biomedical diagnostics.

In this research, a sensitive fluorometric and colorimetric dual-mode sensing platform based on nitrogen-doped carbon quantum dots (NCDs) and magnetic Fe nanoparticles with peroxidase-like activity (Fe nanozymes, Fe NZs) was established, and was further applied for the detection of alpha-glucosidase (alpha-glu) and its inhibitors. The center dot OH that produced by H2O2 catalyzed by Fe NZs can oxidize the colorless diammonium 2,2 '-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) to green oxABTS, and a noticeable absorption peak at 417 nm appeared. Simultaneously, oxABTS can quench the fluorescence of NCDs at 402 nm via fluorescence resonance energy transfer (FRET). 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AAG) can be decomposed by alpha-glu to glucose and ascorbic acid (AA), AA can prevent the oxidation of ABTS, resulting in the absorption at 417 nm decreased. Moreover, the quenching effect of oxABTS on NCDs is weakened, and the fluorescence at 402 nm is restored. Therefore, based on the change of absorption at 417 nm and fluorescence at 402 nm, the fluorometric and colorimetric dual-mode sensing method can be used for the determination of acarbose and voglibose that are the inhibitors of alpha-glu.

Herein, we synthesized a novel N-doped carbon layer encapsulated Fe/Co bimetallic nanoparticles (Fe/Co-NC), which exhibited superior oxidase-like activity due to the facilitation of electron penetration and the formation of metal-nitrogen active sites. Fe/Co-NC could catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) to blue oxTMB. Acetylcholinesterase (AChE) could catalyze the hydrolysis of thioacetylcholine to produce reducing thiocholine, which prevented TMB from oxidation. Thus, a portable hydrogel colorimetric sensor was developed for on-site and visual monitoring of AChE with the detection limit of 0.36 U L-1, and successfully applied to detect AChE in human erythrocyte samples. Furthermore, this platform was used to investigate the inhibition of triazophos on AChE activity.

As one of the existing forms of xanthine oxidoreductase, xanthine oxidase (XOD) exists in many human tissues, and the overactivity of XOD will result in some serious illnesses such as gout and diabetes. Herein, a novel dual-signal sensing system for XOD activity determination was proposed based on fluorescent nitrogen-doped carbon dots (N-CDs) and iron-cobalt oxide nanosheets (FeCo-ONSs). XOD has the ability to oxidise xanthine to uric acid while also producing H2O2. As a sort of peroxidase-like enzyme, FeCo-ONSs can catalyze H2O2 to produce reactive oxygen species (ROS). And N, N-Diethyl-p-phenylenediamine sulfate salt (DPD) was oxidized to DPDox that serves as a chromogenic substrate in the presence of ROS, causing the colorless solution to turn pink. DPDox exhibits two characteristic absorption peaks at 551nm and 512nm and it can also efficiently quench the fluorescence emission of N-CDs at 500nm. Therefore, the fluorometric and colorimetric dual-channel sensing platform was established to assay XOD with the lower LOD of 0.00522 mU/mL and 0.0177 mU/mL, respectively. Additionally, the dual-output strategy was found to be applicable to the quantitative analysis of XOD in serum samples with good reliability and selectivity.

In this paper, a novel sensing strategy with both ratiometric fluorescence and colorimetric responses towards 1,4-dithiothreitol (DTT) was developed based on tannic acid-templated copper nanoclusters (TA-CuNCs). The one-step reduction approach was utilized to obtain TA-CuNCs with the fluorescence emission peak located at 436 nm. Through the catalytic oxidation of Cu2+, o-phenylenediamine (OPD) could be converted to 2,3-diaminophe-nazine (DAP) with an obvious fluorescence signal at 557 nm. Additionally, the obtained yellow DAP showed a clear absorption peak at 420 nm, DAP could cause a significant fluorescence quenching of TA-CuNCs on account of inner-filter effect (IFE). The oxidation process between Cu2+ and OPD could be largely prevented by 1,4-dithiothreitol (DTT), whose sulfhydryl groups bound to Cu2+, and the fluorescence intensity of DAP was diminished, whereas the fluorescence of the TA-CuNCs was restored. The ratiometric fluorescence signal and absorbance intensity changed with the concentration of DTT in the linear ranges of 5-45 mu M and 5-40 mu M, respectively. And the limits of detection (LOD) for two modes were found to be 2.98 and 2.03 mu M, respectively. Furthermore, the dual-mode assay method was used for the determination of DTT accurately and reliably in human serum samples.

In this work, a novel dual-mode ratiometric fluorometric and colorimetric system was proposed based on molybdenum disulfide quantum dots (MoS2 QDs) and rhodamine B (RhB) by combining the Exo III-assisted target recycling approach with the magnetic separation method. KRAS (Kirsten rat sarcoma viral oncogene homolog) gene as the target DNA could hybridize with the hairpin DNA to generate the output DNA through exonuclease III-assisted recycling amplification. The output DNA served as a bridge to link magnetic beads labeled with ssDNA1 (MBs-ssDNA1) to gold nanoparticles modified with ssDNA2 (AuNPs-ssDNA2). After magnetic separation, the remaining AuNPs could catalyze the reduction of RhB with the aid of sodium borohydride (NaBH4). When the KRAS gene concentration increased, the AuNPs in the solution decreased and thus less RhB was reduced. In this process, the fluorescence of RhB at 582 nm enhanced while the fluorescence of MoS2 QDs at 420 nm as a reference signal kept unchanged. Meanwhile, the absorbance of the MoS2 QDs/RhB sensing platform at 554 nm gradually increased. The dual-mode fluorometric and colorimetric sensing methods displayed excellent selectivity for KRAS gene determination with limits of detection (LOD) of 0.22 and 0.41 pM, respectively. By combining signal amplification and magnetic separation technology, this method effectively eliminated background interference and improved the sensitivity of the results. The two detection modes were successfully applied to detect the KRAS gene in real samples.

The development of point-of-care testing (POCT) for glutathione S-transferase (GST) is an effective way to establish the mechanism of targeted monitoring of cancer chemotherapy drug metabolism. Assays for GST with high sensitivity as well as on-site screening have been urgently required to monitor this process. Herein, we synthesized oxidized Pi@Ce-doped Zr-based metal-organic frameworks (MOFs) by electrostatic self-assembly between phosphate and oxidized Ce-doped Zr-based MOFs. It was found that the oxidase-like activity of oxidized Pi@Ce-doped Zr-based MOFs was substantially increased after phosphate ion (Pi) assembly. And a stimulus-responsive hydrogel-based kit was constructed by embedding oxidized Pi@Ce-doped Zr-based MOFs into a PVA (polyvinyl alcohol) hydrogel system, we integrated a portable hydrogel kit with a smartphone for real-time monitoring of GST for quantitative and accurate analysis. The color reaction was triggered based on oxidized Pi@Ce-doped Zr-based MOFs with 3,3',5,5'-tetramethylbenzidine (TMB). However, in the presence of glutathione (GSH), the above color reaction was hindered due to the reducibility of GSH. Catalyzed by GST, GSH can react with 1-chloro-2,4-dinitrobenzo (CDNB) to form an adduct, which caused the color reaction to occur again, resulting in the color response of the kit. In combination with ImageJ software, the kit image information acquired by smartphone could be converted into hue intensity, providing a direct quantitative tool for the detection of GST with a detection limit of 0.19mU·L-1. Based on the advantages of simple operation and cost-effectiveness, the introduction of the POCT miniaturized biosensor platform will meet the requirements of on-site quantitative analysis of GST.

Here, we successfully designed a dual-signal sensing system based on 3-D DNA walker signal amplification and target recycling amplification strategies for ultrasensitive determination of the human immunodeficiency virus (HIV)DNA. The DNA walker is constructed by locked swing arm and track strand onto the surface of the magnetic beads (MBs). After adding HIV DNA, the swing arm was activated to hybridize with the track strand to form ds-DNA, which could be cleaved by Exonuclease III (Exo III) to release G-quadruplex. Subsequently, hemin combined with G-quadruplex to construct DNAzymes, which catalyzed the oxidation of o-phenylenediamine (OPD) into the yellow product 2,3 diaminophenazine (DAP), resulting in the fluorescence quenching of MoS2 QDs at 420 nm, and the fluorescence enhancement of DAP at 560 nm. Therefore, the amounts of HIV DNA can be detected by Uv-vis absorbance and fluorescence dual-signal changes. Besides, each swing arm cleaved multiple track strands to amplify the signal, while the target recycling amplification was also in progress. Such doubleamplified signal strategy not only provided excellent sensitivity and selectivity, but also realized magnetic separation, eliminating interferences in complex samples. In addition, our designed sensing platform can detect different DNAs by adjusting the recognition sequence, providing a general strategy for various virus analysis.

Herein, a multi-mode assay platform was constructed for the detection of D-penicillamine based on perovskite nanocrystals (CsPbBr3 NCs) and MnO2 nanosheets. The water-dispersible CsPbBr3 NCs synthesized via aqueous emulsion process has a strong fluorescence emission at 520 nm. The electrostatic interaction between positively charged CsPbBr3 NCs and negatively charged MnO2 nanosheets would lead to the fluorescence quenching of CsPbBr3 NCs on account of the inner filter effect (IFE). The addition of D-penicillamine could convert MnO2 nanosheets to Mn2+ and weaken inner filter effect, resulting in distinct recovery of fluorescence at 520 nm and the decrease of the absorption of CsPbBr3 NCs/MnO2 at 375 nm. Therefore, the fluorescence and colorimetric assay system for D-penicillamine was developed. The fluorescence and colorimetric sensing system could detect D-penicillamine ranging from 0.1 to 40 & mu;M and 0.5 to 40 & mu;M with the limits of detection (LOD) were 0.061 & mu;M and 0.24 & mu;M, respectively. The developed assay system could be applied to analyze D-penicillamine in real samples and acquired satisfactory results. Furthermore, a portable intelligent detection device was developed based on the mobile phone and RGB analysis software, demonstrating the practicability and potential of the sensing system.

Herein, we constructed a label-free ratiometric fluorescence biosensing strategy for the determination of butyrylcholinesterase (BChE) activity and organophosphorus (OPs) concentration. BChE promoted the hydrolysis of iodized s-butyrylthiocholine (BTCh) into a reducing substance thiocholine, which can decompose CoOOH nanosheets (CoOOH NSs) to Co2+. Subsequently, the single-stranded DNA (ssDNA) on the surface of CoOOH NSs was released. Then, ssDNA hybridized with hairpin DNA (h-DNA) and triggered the target recycling amplification process, producing large amounts of G-quadruplex. After adding thioflavin T (ThT), the target BChE was converted into activatable G-quadruplex/ThT with an amplified yellow fluorescence signal. The addition of OPs could significantly inhibit the hydrolysis of BTCh by BChE and thus unable to produce the yellow fluorescence G-quadruplex/ThT complex. Throughout the entire process, the fluorescence intensity of Hg-ZnSe QDs as a reference signal remained unchanged at 630 nm. Furthermore, this work provided an effective approach for detecting the BChE activity in serum samples and OPs in fruits and vegetables.

Herein, a novel dual-signal sensing system for the determination of beta-galactosidase (beta-Gal) activity was estab-lished, which was based on a dual-emission probe assembled from gold-platinum bimetallic nanoclusters (Au-Pt NCs) and rhodamine B. Under the catalysis of beta-Gal, 4-nitrophenyl beta-D-galactopyranoside (PNPG) was rapidly hydrolyzed to generate p-nitrophenol (PNP), which has an obvious UV absorption peak at 400 nm. The hy-drolyzed product PNP can quench the fluorescence of Au-Pt NCs effectively by inner filter effect (IFE), and PNP had no impact on the fluorescence of rhodamine B, which will change the emission intensity ratio of Au-Pt NCs and rhodamine B. Therefore, the ratiometric fluorescent and colorimetric dual-signal sensor based on Au-Pt NCs and rhodamine B was successfully constructed for sensitive detection of beta-Gal activity. The linear detection range for the ratiometric fluorescence and colorimetric methods were 2.5-25 U/L and 15-55 U/L with detection limits of 1.2 U/L and 5.2 U/L, respectively. The developed assay method has been used for quantitative detection of beta-Gal in spiked serum samples and showed good performance. And the detection platform has high reliability and excellent selectivity, which opens a new avenue for the further application of Au-Pt NCs in chemical sensing and biological analysis.

Herein, we have synthesized a novel kind of gold nanoclusters decorated iron-cobalt oxide nanosheets (His-AuNCs@FeCo-ONSs) assembled by electrostatic interaction, which possessed both outstanding peroxidase-like activity and fluorescence property. Taking advantage of our bifunctional hybrid nanozyme and enzyme cascade reactions, a sensitive dual-mode (colorimetric/fluorescent) detection method for α-glucosidase was constructed. The detection limits for α-glucosidase were 2.2 U/L and 3.3 U/L in fluorometric and colorimetric mode, respectively. This method not only provides high sensitivity, but also can correct itself to improve the accuracy of analysis due to the dual-response signals. Furthermore, it was employed for α-glucosidase determination in real samples and screening of α-glucosidase inhibitors.