Clinical observation and influence on nutritional status of intensive nutritional nursing combined with 3-day dietary diary intervention in peritoneal dialysis patients.

BACKGROUND: Peritoneal dialysis is a commonly used treatment for chronic kidney failure patients. Studies have shown that long-term peritoneal dialysis can lead to various degrees of malnutrition. Therefore, it is of great significance to improve the nutritional conditions of patients with peritoneal dialysis. This retrospective cohort study aimed to evaluate the clinical effects of intensive nutritional nursing combined with a 3-day diet diary intervention on the nutritional condition of peritoneal dialysis patients. METHODS: In total, 163 patients were included in this study and, after 6 months of intervention, their nutritional and biochemical indicators, body weight, body mass index (BMI) and intake of dietary ingredients were analysed. RESULTS: After the intervention, patients' serum albumin, haemoglobin, prealbumin, body weight, BMI and cholesterol levels were significantly increased (p < 0.05). Also, the daily energy and protein intake were significantly increased, whereas phosphorus intake was decreased (p < 0.05). Of note, the effective rate of intervention was 63.8%, respectively. We also found that factors such as the patient's age, education degree, income level and peritoneal dialysis age were the risk factors associated with malnutrition. Moreover, patients younger than 55 years old, with dialysis age younger than 5 years, unmarried/divorced and high school graduates, had higher chances of effective intervention, whereas the possibility of effective intervention was lower when the per capita monthly household income was less than 4000 Yuan. CONCLUSIONS: In conclusion, intensive nutritional nursing combined with a 3-day dietary diary intervention can significantly improve the nutritional condition and optimise the diet structure of peritoneal dialysis patients with malnutrition. These findings provide evidence for healthcare providers to develop personalised interventions to address malnutrition in this population.

Regulating the N Coordination Environment of Co Single-Atom Nanozymes for Highly Efficient Oxidase Mimics.

Single-atom catalysts with well-defined atomic structures and precisely regulated coordination environments have been recognized as potential substitutes for natural metalloenzymes. Inspired by the metal coordination structure of natural enzymes, we show here that the oxidase-like activity of single-atom Co catalysts greatly depends on their local N coordination around the Co catalytic sites. We synthesized a series of Co single-atom catalysts with different nitrogen coordination numbers (Co-Nx(C), x = 2, 3, and 4) and demonstrated that the oxidase-like activity of single-atom Co catalysts could be effectively tailored by fine-tuning the N coordination. Among the studied single-atom Co catalysts, the Co-N3(C) with three-coordinate N atoms shows the optimum oxygen adsorption structure and robust reactive oxygen species (ROS) generation, thus presenting the preferable oxidase-like catalytic activity. This work facilitates the future development of rational nanozyme designs for targeting reactions at the atomic level.

Light-Triggered Signal Enhancement Strategy Integrated with a CRISPR/Cas13a-Based Assay for Ultrasensitive and Specific miRNA Detection.

The development of facile, accurate, and affordable assays for microRNAs (miRNAs) in early cancer is greatly desirable but encounters an obstacle due to low cellular abundance in biofuids. In this study, we present a novel approach called a light-triggered exponential amplification strategy coupled with a CRISPR/Cas13a-based diagnostic system (LEXPA-CRISPR), which directly transduces rare miRNA targets into photocontrolled signal enhancement response. This innovative platform leverages trans-cleavage of CRISPR/Cas13a, activated by the miRNA target, to cleave specific RNA fragments within the MB@PC-NAC assembly, thus releasing free PC-single-stranded DNA (PC-ssDNA) that is modified by a photocleavable linker (PC linker). UV irradiation is further employed toward the photoresponsive PC-ssDNA, resulting in instantaneous generation of oligo with a new 5' phosphate group (Pho-ssDNA). The Pho-ssDNA serves as a trigger for rolling circle amplification (RCA) reaction, which generates thousands of long ssDNA repeats of diverse lengths with a strong fluorescence signal. Through optimization, we achieved a detection limit of 1 fM for miR21 without the need for target amplification. Moreover, the programmable versatility of LEXPA-CRISPR is also demonstrated for miR17 determination only with simple modification of CRISPR RNA (crRNA) sequences. This proposed biosensor successfully monitored the levels of miR21 and miR17 in tumor cells, showing a satisfactory consistency with the standard qRT-PCR method. Conclusively, LEXPA-CRISPR represents a promising strategy for ultrasensitive miRNA detection. It combines the advantages of light-triggered signal amplification and robust collateral cleavage activity of Cas13a, making it an attractive tool for practical CRISPR-based diagnostics.

A one-tube dual-readout biosensor for detection of nucleic acids and non-nucleic acids using CRISPR-ALP tandem assay.

Clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostics have been considered a next-generation molecular diagnosis tool. Single-readout mode has been extensively employed in massive CRISPR/Cas12a-based biosensors. In this work, we propose a one-tube dual-readout biosensor (CRISAT) for the first time for the detection of ultrasensitive nucleic acids and non-nucleic acids developed by harnessing CRISPR-ALP tandem assay. In the presence of a target, Cas12a is activated to randomly cut the single-stranded hyDNA sequence of MB@hyDNA-cALP, thus releasing abundant alkaline phosphatase (ALP) in the supernatant solution. By using 4-aminophenol phosphate as the substrate of ALP, p-aminophenol is produced, which then reacts with N-[3-(trimethoxysilyl)propyl]ethylenediamine or diethylenetriamine to generate silicon-containing polymer carbon dots (Si PCDs) or polymer carbon dots (PCDs) in situ, which can be observed by the naked eye or detected using a fluorescent device in the same solution. Using this strategy, a fluorescence and colorimetry dual-readout nanoplatform for CRISPR-based biosensors can be rationally developed. We ascertain the applicability of CRISAT by detecting the SARS-CoV-2 pseudovirus, achieving superior sensitivity and specificity. With simple modification of crRNAs, the CRISAT platform can also be employed to detect monkeypox virus (MPXV) and non-nucleic acids of adenosine triphosphate (ATP). This work shows great potential for the detection of nucleic acids and non-nucleic acids.

Fluorescence detection of 4-nitrophenol and α-glucosidase activity based on 4-nitrophenol-regulated fluorescence of silicon nanoparticles.

A fluorescence assay for the detection of 4-nitrophenol (4-NP), α-glucosidase (α-Glu) activity and α-Glu inhibitors (AGIs) is developed based on the inner filter effect (IFE), a flexible and simple signal transfer strategy. In this assay, silicon nanoparticles (Si NPs) synthesized under mild and easily accessible conditions are employed as fluorescent indicators. 4-NP efficaciously quenches the fluorescence of Si NPs through the IFE at a very rapid rate, thus achieving 4-NP detection in a mix-to-read manner, which is suitable for on-site detection. The quenching mechanism has been comprehensively studied and confirmed. More significantly, based on the fact that 4-NP can be generated through α-Glu-catalyzed hydrolysis of 4-nitrophenyl-α-D-glucopyranoside (NPG), the fluorescence detection of α-Glu activity is legitimately achieved by employing NPG as the substrate. The linear ranges for 4-NP and α-Glu activity detection are 0.5-60 µM and 0.5-60 mU mL-1 with low detection limits of 0.074 µM and 0.094 mU mL-1, respectively. This method not only can preciously assay targets in real samples, but is also capable of screening AGIs as drugs as well as assessing their inhibition efficiency.

Platinum nanoparticles confined in metal-organic frameworks as excellent peroxidase-like nanozymes for detection of uric acid.

High levels of uric acid (UA) in humans can cause a range of diseases, and traditional assays that rely on uric acid enzymes to break down uric acid are limited by the inherent deficiencies of natural enzymes. Fortunately, the rapid development of nanozymes in recent years is expected to solve the above-mentioned problems. Hence, we used a host-guest strategy to synthesize a platinum nanoparticle confined in a metal-organic framework (Pt NPs@ZIF) that can sensitively detect UA levels in human serum. Unlike previously reported free radical-catalyzed oxidation systems, its unique electron transfer mechanism confers excellent peroxidase-like activity to Pt NPs@ZIF. In addition, UA can selectively inhibit the chromogenic reaction of TMB, thus reducing the absorbance of the system. Therefore, using the peroxidase-like activity of Pt NPs@ZIF and using TMB as a chromogenic substrate, UA can be detected directly without relying on natural enzymes. The results showed a relatively wide detection range (10-1000 µM) and a low detection limit (0.2 µM). Satisfactory results were also obtained for UA in human serum. This study with simple operation and rapid detection offers a promising method for efficiently detecting UA in serum.

Multienzyme Cascades Based on Highly Efficient Metal-Nitrogen-Carbon Nanozymes for Construction of Versatile Bioassays.

Distinguished by the coupled catalysis-facilitated high turnover and admirable specificity, enzyme cascades have sparked tremendous attention in bioanalysis. However, three-enzyme cascade-based versatile platforms have rarely been explored without resorting to tedious immobilization procedures. Herein, we have demonstrated that formamide-converted transition metal-nitrogen-carbon (f-MNC, M = Fe, Cu, Mn, Co, Zn) with a high loading of atomically dispersed active sites possesses intrinsic peroxidase-mimetic activity following the activity order of f-FeNC > f-CuNC > f-MnNC > f-CoNC > f-ZnNC. Ulteriorly, benefitting from the greatest catalytic performance and explicit catalytic mechanism of f-FeNC, versatile enzyme cascade-based colorimetric bioassays for ultrasensitive detection of diabetes-related glucose and α-glucosidase (α-Glu) have been unprecedentedly devised using f-FeNC-triggered chromogenic reaction of 3,3',5,5'-tetramethylbenzidine as an amplifier. Notably, several types of α-Glu substrates can be effectively utilized in this three-enzyme cascade-based α-Glu assay, and it can be further employed for screening α-Glu inhibitors that are used as antidiabetic and antiviral drugs. These versatile assays can also be extended to detect other H2O2-generating or -consuming biomolecules and other bioenzymes that are capable of catalyzing glucose generation procedures. These nanozyme-involved multienzyme cascades without intricate enzyme-engineering techniques may provide a concept to facilitate the deployment of nanozymes in celestial versatile bioassay fabrication, disease diagnosis, and biomedicine.

Manganese-doped iron coordination polymer nanoparticles with enhanced peroxidase-like activity for colorimetric detection of antioxidants.

A convenient and sensitive antioxidant assay with high performance is essential for assessing food quality and monitoring the oxidative stress level of biological matrices. Although coordination polymer nanoparticles (CPNs)-based nanozymes have emerged as candidates in the analytical field, strategies to improve the catalytic activity of CPNs have been scarcely revealed and studied. Herein, we demonstrate a manganese (Mn) doping strategy to enhance the peroxidase-mimetic activity of Fe-based CPNs. By tuning the Mn doping amounts and selecting 2,5-dihydroxyterephthalic acid (H4DHTP) as ligands, the produced nanozymes in amorphous state followed the catalytic activity order of Fe5Mn-DHTP > Fe8Mn-DHTP > Fe2Mn-DHTP > Fe-DHTP > Mn-DHTP. Ulteriorly, benefitting from the best catalytic performance and definite catalytic mechanism of Fe5Mn-DHTP, versatile colorimetric assays for ultrasensitive detection of one exogenous antioxidant (ascorbic acid, AA) and two endogenous antioxidants (glutathione, GSH; cysteine, Cys) have been deftly devised based on the inhibition of the 3,3',5,5'-tetramethylbenzidine chromogenic reaction in presence of H2O2. It was found that mercaptan (GSH and Cys) and AA exhibited different inhibition mechanisms. Practically, such a colorimetric assay was viable to determine the total antioxidant capacity of drugs and foods with desirable results. This work proposes a feasible strategy for embellishing CPN nanozymes used for designing sensitive and convenient assays for various antioxidants based on an explicit detection mechanism.

Inhibited oxidase mimetic activity of palladium nanoplates by poisoning the active sites for thiocyanate detection.

In this work, a novel convenient colorimetric method for sensitive detection of thiocyanate (SCN-) has been developed based on its suppression of the oxidase-like activity of palladium square nanoplates on reduced graphene oxide (Pd SP@rGO). SCN- can be adsorbed onto the surface of Pd SP@rGO via binding with Pd atoms and blocks the active sites that mimic oxidase, thus inhibiting the corresponding chromogenic reaction of 3,3',5,5'-tetramethylbenzidine, which has been comprehensively revealed by the UV-vis spectra and X-ray photoelectron spectra. The color fading exhibits SCN- concentration-dependent behavior and can be easily recorded by either UV-vis spectroscopy or naked-eye observation. Therefore, both quantitative detection via measurement of the decrease in absorbance and visual detection of SCN- can be achieved. Owing to the intrinsic amplification of signals by the oxidase-like activity of Pd SP@rGO without resorting to unstable and destructive H2O2, this assay is straightforward, robust and sensitive enough for the detection of SCN- in real samples. Furthermore, an "INH" logic gate is rationally constructed based on the proposed colorimetric SCN- sensor.

Ultrathin PdCu alloy nanosheet-assembled 3D nanoflowers with high peroxidase-like activity toward colorimetric glucose detection.

Enzyme-mimetic properties of nanomaterials can be efficiently tuned by controlling their size, composition, and structure. Here, ultrathin PdCu alloy nanosheet-assembled three-dimensional (3D) nanoflowers (Pd1Cux NAFs) with tunable surface composition are obtained via a generalized strategy. In presence of H2O2, the as-synthesized Pd1Cux NAFs can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to the oxidized form of TMB (oxTMB) with a characteristic absorption peak at 652 nm. Interestingly, Pd1Cux NAFs show obviously composition-dependent peroxidase-like catalytic activities because of the synergistic interaction of nanoalloy. Additionally, different from 2D Pd nanosheets, the distinctive 3D superstructures are featured with rich approachable sites and proper layer spacing, which are in favor of fast mass transport and electron transfers during the catalytic process. Among the studied Pd1Cux NAFs, the Pd1Cu1.7 NAFs show the highest enzyme-like activities and can be successfully applied for the colorimetric detection of glucose with a low detection limit of 2.93 ± 0.53 µM. This work provides an efficient avenue to fabricate PdCu NAF nanozymes in biosensing toward glucose detection. Two-dimensional (2D) PdCu ultrathin nanosheet-assembled 3D nanoflowers (Pd1Cux NAFs) with tunable surface composition exhibit substantially enhanced intrinsic peroxidase-like catalytic activities. The Pd1Cu1.7 NAFs are successfully used as peroxidase mimic catalyst for the colorimetric detection of glucose with low detection limit of 2.93 µM.

Colorimetric detection of acetylcholinesterase and its inhibitor based on thiol-regulated oxidase-like activity of 2D palladium square nanoplates on reduced graphene oxide.

A convenient and sensitive colorimetric assay for acetylcholinesterase (AChE) and its inhibitor has been designed based on the oxidase-like activity of {100}-faceted Pd square nanoplates which are grown in situ on reduced graphene oxide (PdSP@rGO). PdSP@rGO can effectively catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) without the assistance of H2O2 to generate blue oxidized TMB (oxTMB) with a characteristic absorption peak at 652 nm. In the presence of AChE, acetylthiocholine (ATCh), a typical AChE substrate, is hydrolyzed to thiocholine (TCh). The generated TCh can effectively inhibit the PdSP@rGO-triggered chromogenic reaction of TMB via cheating with Pd, resulting in color fading and decrease in absorbance. Thus, a sensitive probe for AChE activity is constructed with a working range of 0.25-5 mU mL-1 and  a limit of detection (LOD) of 0.0625 mU mL-1. Furthermore, because of the inhibition effect of tacrine on AChE, tacrine is also detected through the colorimetric AChE assay system within the concentrations range 0.025-0.4 µM with a LOD of 0.00229 µM. Hence, a rapid and facile colorimetric procedure to sensitively detect AChE and its inhibitor can be anticipated through modulating the oxidase-like activity of PdSP@rGO. Colorimetric method for detection of AChE and its inhibitor is established by modulating the oxidase mimetic activity of {100}-faceted Pd square nanoplates on reduced graphene oxide (PdSP@rGO).

Alkaline Phosphatase-Triggered in Situ Formation of Silicon-Containing Nanoparticles for a Fluorometric and Colorimetric Dual-Channel Immunoassay.

Enzyme-triggered in situ chromogenic and/or fluorogenic reactions under accessible conditions are significant for developing enzyme activity and related spectroscopic assays. Here, we describe a facile one-pot synthetic strategy to prepare silicon-containing nanoparticles with yellow-green fluorescence and orange-red color by mixing N-[3-(trimethoxysilyl)propyl]ethylenediamine and p-aminophenol (AP) in aqueous solution at a mild temperature. Encouraged by the AP-regulated simple synthetic procedure and the generation of AP from alkaline phosphatase (ALP)-catalyzed hydrolysis of 4-aminophenol phosphate (APP), a fluorometric and colorimetric dual-readout ALP activity assay can be rationally envisioned and developed by employing APP as the substrate. In the wake of the good analytical performance of such ALP activity assay and its successful combination with enzyme-linked immunosorbent assay (ELISA), corresponding fluorometric and colorimetric dual-readout ALP-based ELISA has been constructed for highly sensitive and quantitative determination of human prostate-specific antigen (PSA), the key biomarker of prostate cancer in human serum. The convincing performance in evaluating the PSA level in serologic tests unambiguously reveals the great potential of our proposed fluorometric and colorimetric dual-channel immunoassay in early clinical diagnosis by monitoring disease biomarkers.

Colorimetric determination of the activity of alkaline phosphatase by exploiting the oxidase-like activity of palladium cube@CeO2 core-shell nanoparticles.

Core-shell palladium cube@CeO2 (Pd cube@CeO2) nanoparticles are shown to display oxidase-like activity. This is exploited in a method for determination of the activity of alkaline phosphatase (ALP). The Pd cube@CeO2 nanoparticles were thermally synthesized from Ce(NO3)3, L-arginine and preformed Pd cube seeds in water. The Pd cube@CeO2 nanoparticles catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by oxygen. This results in the formation of oxidized TMB (oxTMB) with an absorption peak at 652 nm. Ascorbic acid (AA) is generated from the hydrolysis of L-ascorbic acid 2-phosphate (AAP) catalyzed by ALP. It can reduce oxTMB to TMB, and this results in a decrease of the absorbance. The method allows for quantitative determination of the activity of ALP in the range from 0.1 to 4.0 U·L-1 and with a detection limit down to 0.07 U·L-1. Endowed with high sensitivity and selectivity, the assay can quantify ALP activity in biological system with satisfactory results. Graphical abstractSchematic illustration of Pd cube@CeO2 core-shell nanoparticles for colorimetric determination of alkaline phosphatase.

Logically Regulating Peroxidase-Like Activity of Gold Nanoclusters for Sensing Phosphate-Containing Metabolites and Alkaline Phosphatase Activity.

Phosphate-containing metabolites and alkaline phosphatase (ALP) activity are useful biomarkers for many types of diseases. However, there are few straightforward, sensitive, and efficient colorimetric methods for the quantification of them only when resorting to unstable transition metal ions or specially designed organic substrates. Herein, we have demonstrated that histidine-protected gold nanoclusters (His-AuNCs) possess intrinsic peroxidase-like activity with Au atom facilitated formation of superoxide anions (O2•-) and their electron transfer ability. More interestingly, phosphate-containing metabolites can severely inhibit the peroxidase-like activity of His-AuNCs by blocking the generation of O2•- and electron transfer, and then ALP is able to restore the inhibition process through hydrolyzing the phosphate-containing metabolites. Therefore, using peroxidase-triggered chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) as an amplifier, a colorimetric on-off-on switch has been developed for sensing phosphate-containing metabolites and ALP based on the logical regulation of such deactivation and reactivation processes for the first time. According to the intrinsic mimic enzyme-catalyzed amplification and clear response mechanism, our colorimetric assay exhibits excellent sensitivity, selectivity, and sensing performance. Furthermore, on the basis of the proposed colorimetric sensors, a combinatorial "NOR+IMPLICATION" logic gate is further rationally constructed.

Fluorometric and colorimetric dual-readout alkaline phosphatase activity assay based on enzymatically induced formation of colored Au@Ag nanoparticles and an inner filter effect.

An ultrasensitive fluorometric and colorimetric dual-mode assay is described for the determination of the activity of alkaline phosphatase (ALP). ALP catalyzes the decomposition of 2-phospho-L-ascorbic acid, and the ascorbic acid thus generated reduces silver ions. In the presence of gold nanoparticles, gold-silver nanoparticles (Au@Ag NPs) are formed. This is accompanied by a color change form pink to deep yellow. The Au@Ag NPs reduce the fluorescence of blue fluorescent graphene quantum dots due to spectral overlap. The changes of absorbance (measured at 410 and 520 nm) and fluorescence (measured at excitation/emission wavelengths of 346/415 nm) correlate well with the ALP activity in the 0.01-6 mU·mL-1 (absorption) and 0.01-2 mU·mL-1 (fluorescence) ranges, and the detection limits are 9 and 5 µU·mL-1 individually. Graphical abstract Schematic presentation of colorimetric and fluorometric dual-readout assay for alkaline phosphatase (ALP) activity. It is based on enzymatically induced formation of gold-silver nanoparticles (Au@Ag NPs), and the fluorescence quenching of graphene quantum dots due to inner filter effect.

Fluorometric determination of the activity of alkaline phosphatase and its inhibitors based on ascorbic acid-induced aggregation of carbon dots.

The authors describe a fluorometric method for determination of the activity of alkaline phosphatase (ALP) and its inhibitors. Nitrogen and boron co-doped carbon dots (C-dots) with excitation/emission peaks at 490/540 nm act as the fluorescent probe. The C-dots were prepared by hydrothermal carbonization starting from 3-aminophenylboronic acid as the sole precursor. On the basis of the boronic acid-triggered specific reaction with cis-diols, the boronic acid modified C-dots can bind to ascorbic acid that is generated by ALP-catalyzed hydrolysis of ascorbic acid 2-phosphate. This results in particle aggregation and quenching of fluorescence. If the ALP inhibitor Na3VO4 is introduced into the system, the activity of ALP is reduced and the fluorescence of C-dots recovers. This fluorometric method allows for the determination of ALP activity in the range from 0.2 to 6.0 mU mL-1 with a detection limit of 0.16 mU mL-1. The IC50 value for the inhibitor Na3VO4 is 3.6 µM. The method is convenient and cost-effective. It does not require complicated operations and in our perception widens the scope of applications of C-dots in bioanalytical sciences. Graphical abstract Schematic presentation of the nitrogen and boron co-doped carbon dot-based fluorometric method for determination of alkaline phosphatase (ALP) activity.

Spectrophotometric determination of the activity of alkaline phosphatase and detection of its inhibitors by exploiting the pyrophosphate-accelerated oxidase-like activity of nanoceria.

The oxidase-like activity of nanoceria is low. This limits its practical applications. It is demonstrated here that pyrophosphate ion (PPi) can improve the oxidase-like activity of nanoceria. Specifically, nanoceria catalyzes the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to give a blue product (oxTMB) with an absorption peak at 645 nm in the presence of PPi. If, however, alkaline phosphatase (ALP) is present, it will hydrolyze PPi, and this results in a decreased oxidase-like activity of nanoceria. Hence, less blue oxTMB willl be formed. On the other hand, if the ALP inhibitor Na3VO4 is added to the system, the oxidase-like activity of nanoceria is gradually restored. On the basis of the above results, a spectrophotometric method was developed for determination of the activity of ALP. It works in the 0.5 to 10 mU.mL-1 activity range and has a 0.32 mU.mL-1 detection limit. Na3VO4 causes a 50% ALP inhibition if present in 71 µM concentration. The assay was successfully applied to the determination of ALP in spiked human serum and gave good recoveries. Graphical abstract Schematic presentation of pyrophosphate (PPi)-induced acceleration of the oxidase-like activity of nanoceria (CeO2) for determination of alkaline phosphatase enzyme (ALP) activity and its inhibitor NaVO3.

Fluorescence Immunoassay Based on the Phosphate-Triggered Fluorescence Turn-on Detection of Alkaline Phosphatase.

A simple and cost-effective fluorescence immunoassay for the sensitive quantitation of disease biomarker α-fetoprotein (AFP) has been developed based on the phosphate-triggered fluorescence turn-on detection of alkaline phosphatase (ALP), with the reversible binding between calcein and Ce3+ as a signaling element. In this immunoassay, fluorescent calcein is readily quenched by Ce3+ via a coordination process. The ALP-catalyzed hydrolysis of p-nitrophenyl phosphate leads to the formation of p-nitrophenol and inorganic orthophosphate, and the newly formed orthophosphate could potently combine with Ce3+ due to the higher affinity, thus, recovering the fluorescence of calcein. The corresponding fluorescence signal triggered by phosphate is related to ALP activities labeled on antibody, and thus could be applied to detect target antigen in an enzyme-linked immunosorbent assay (ELISA) platform. The fluorescence intensity correlated well to the AFP concentration ranges of 0.2-1.0 and 1.0-4.0 ng/mL, with a detection limit of 0.041 ng/mL. The proposed fluorescence ELISA possesses convincing recognition mechanism and exhibits excellent assay performance in the evaluation of the AFP level in serologic test, which unambiguously reveals great application potential in the clinic diagnosis of disease biomarkers.

Fluorescence assay for alkaline phosphatase based on ATP hydrolysis-triggered dissociation of cerium coordination polymer nanoparticles.

Alkaline phosphatase (ALP) is a significant biomarker for diagnostics. Simple, selective and sensitive detection of ALP activity is thus of critical importance. In this study, an artful fluorescence assay for ALP is proposed based on adenosine triphosphate (ATP) hydrolysis-triggered disassociation and fluorescence quenching of cerium coordination polymer nanoparticles (CPNs). ATP, a recognized natural substrate of phosphatase, can serve as a superb "antenna" to sensitize the luminescence of Ce3+ with the aid of tris(hydroxymethyl) aminomethane (Tris), forming Ce3+-ATP-Tris CPNs. In the presence of ALP, ATP will be catalytically converted into adenosine and inorganic orthophosphate, however neither of them can sensitize Ce3+ in alkaline media. As a result, the obtained CPNs are disassociated, inducing the quenching of the fluorescence. On this basis, a straightforward fluorescence assay for ALP activity is rationally developed. The fluorescence quenching efficiency shows a linear relationship for ALP within the activity range from 0.1 to 10 mU mL-1 with a detection limit of 0.09 mU mL-1 under the optimal experimental conditions. Moreover, this facile yet effective fluorescence method featured simplicity, cost-effectiveness, high sensitivity and high selectivity and can be successfully utilized for the quantitative detection of ALP in human serum samples.

Highly sensitive fluorescent detection of glutathione and histidine based on the Cu(ii)-thiamine system.

In this work, we propose a fluorescence method for the simultaneous detection of glutathione (GSH) and histidine (His) based on the Cu(ii)-thiamine (Cu(ii)-TH) system. It is well established that non-fluorescent thiamine (TH) can be oxidized by Cu(ii) to generate fluorescent thiochrome (TC) under alkaline conditions. The introduction of GSH and His can inhibit the oxidation of TH by Cu(ii) due to the strong affinity between Cu(ii) and GSH or His. With this strategy, the detection limit for GSH and His is 10.5 nM and 26.4 nM, respectively. The developed method shows several obvious advantages: (1) simplicity in design and operation without the utilization of fluorescent nanomaterials or probes; (2) time-saving detection process since all the detection process is completed within 15 min; (3) cost-effectiveness by using TH as the fluorescent substrate; and (4) higher sensitivity and good selectivity. Therefore, it shows great potential in biosensing fields.