Colorimetric detection of alkaline phosphatase based on the off-on effect of light-responsive oxidase mimicking activity of covalent organic framework (Cu-TpBpy-COF) under near-neutral condition.

A colorimetric strategy has been developed for the detection of alkaline phosphatase (ALP) activity based on the off-on effect of the catalytic activity of light-responsive oxidase mimics covalent organic framework (Cu-TpBpy-COF) in near-neutral condition. Cu-TpBpy-COF can effectively catalyze the oxidation of the colorless substrate 3,3',5,5'-tetramethylbenzidine (TMB) by oxygen to form a blue oxidized product (oxTMB) with an absorption peak at 652 nm. Cu2+ is the active center of Cu-TpBpy-COF and pyrophosphate (PPi) can form a complex with Cu2+ to weaken the catalytic activity of Cu-TpBpy-COF. In the presence of ALP, PPi is hydrolyzed into orthophosphates (Pi) with low affinity to Cu2+, thus resulting in absorbance restoration. The absorbance at 652 nm is related to ALP activity in the linear range 10-150 U·L-1 with a detection limit of 7.17 U·L-1. The recoveries of ALP in serum samples are in the range 94.7~107.0% with relative standard deviations (RSD) lower than 5%. The decisive role of Cu2+ on the enhancing catalytic activities of Cu-TpBpy-COF in neutral condition was verified by TpBpy-COF and TpBD-COF as controls, in which the main difference between them is that TpBpy-COF contains pyridine nitrogen. Upon Cu2+ modification, Cu-TpBpy-COF has better catalytic activity than TpBpy-COF in a broader pH range because of the in situ generation of Cu+ under irradiation.

Red Emission Carbon Nanoparticles Which Can Simultaneously Responding to Hypochlorite and pH.

Multi-targets detection has obtained much attention because this sensing mode can realize the detection of multi-targets simultaneously, which is helpful for biomedical analysis. Carbon nanoparticles have attracted extensive attention due to their superior optical and chemical properties, but there are few reports about red emission carbon nanoparticles for simultaneous detection of multi-targets. In this paper, a red emission fluorescent carbon nanoparticles were prepared by 1, 2, 4-triaminobenzene dihydrochloride at room temperature. The as-prepared red emission fluorescent carbon nanoparticles exhibited strong emission peak located at 635 nm with an absolute quantum yield up to 24%. They showed excellent solubility, high photostability and good biocompatibility. Furthermore, it could sensitively and selectively response to hypochlorite and pH, thus simultaneous detection of hypochlorite and pH was achieved by combining the red emission fluorescent carbon nanoparticles with computational chemistry. The formation mechanisms of red emission fluorescent carbon nanoparticles and their response to hypochlorite and pH were investigated, respectively.

Fluorescent/Colorimetric Dual-Mode Discriminating Gln and Val Enantiomers Based on Carbon Dots.

Discrimination and quantification of amino acid (AA) enantiomers are particularly important for diagnosing and treating diseases. Recently, dual-mode probes have gained a lot of research interest because they can catch more detecting information compared with the single-mode probes. Thus, it is of great significance to develop a dual-mode sensor realizing AA enantiomer discrimination conveniently and efficiently. In this work, carbon dot L-TCDs were prepared by N-methyl-1,2-benzenediamine dihydrochloride (OTD) and l-tryptophan. With the assistance of H2O2, L-TCDs show an excellent discrimination performance for enantiomers of glutamine (Gln) and valine (Val) in both fluorescent and colorimetric modes. The fluorescence enantioselectivity of Gln (FD/FL) and Val (FL/FD) is 5.29 and 4.13, respectively, and the colorimetric enantioselectivity of Gln (ID/IL) and Val (IL/ID) is 13.26 and 3.42, individually. The chiral recognition mechanism of L-TCDs was systematically studied. L-TCDs can be etched by H2O2, and the participation of AA enantiomers results in different amounts of the released OTD, which provides fluorescent and colorimetric signals for identifying and quantifying the enantiomers of Gln and Val. This work provides a more convenient and flexible dual-mode sensing strategy for discriminating AA enantiomers, which is expected to be of great value in facile and high-throughput chiral recognition.

Construction of dual exponential amplification accompanied by multi-terminal signal output method for convenient detection of tumor biomarker FEN1 activity.

As an important 5'-nuclease in DNA replication and damage repair, Flap endonuclease 1 (FEN1) has been considered as a potential tumor biomarker due to its overexpression in different human cancer cells. Here, we developed a convenient fluorescent method based on dual enzymatic repairing exponential amplification accompanied by multi-terminal signal output to realize the rapid and sensitive detection of FEN1. In the presence of FEN1, the double-branched substrate could be cleaved to produce 5' flap single strand DNA (ssDNA) which subsequently was used as a primer to initiate the dual exponential amplification (EXPAR) to generate abundant ssDNAs (X' and Y'), then the ssDNAs can respectively hybridize with the 3' and 5' ends of the signal probe to form partially complementary double strands (dsDNAs). Subsequently, the signal probe on the dsDNAs could be digested under the assistance of Bst. polymerase and T7 exonuclease, as well as releasing the fluorescence signals. The method displayed high sensitivity with the detection limit of 9.7 × 10-3 U mL-1 (1.94 × 10-4 U) and also exhibited good selectivity towards FEN1 under the challenge from complicated samples including extracts of normal and cancer cells. Furthermore, it was successfully applied to screen FEN1 inhibitors, holding great promise in the screening of potential drugs targeting FEN1. This sensitive, selective and convenient method could be used for FEN1 assay without the complicated nanomaterial synthesis/modification, showing great potential in FEN1- related prediction and diagnosis.

Exploring the effect of silicene monolayer on the structure and function of villin headpiece and amyloid fibrils by molecular dynamics simulations.

With the development of various nanomaterial expected to be used in biomedical fields, it is more important to evaluate and understand their potential effects on biological system. In this work, two proteins with different structure, Villin Headpiece (HP35) with α-helix structure and protofibrils Aß1-42 with five ß-strand chains, were selected and their interactions with silicene were studied by means of molecular dynamics (MD) simulation to reveal the potential effect of silicene on the structure and function of biomolecules. The obtained results indicated that silicene could rapidly attract HP35 and Aß1-42 fibrils onto the surface to form a stable binding. The adsorption strength was moderate and no significant structural distortion of HP35 and Aß1-42 fibrils was observed. Moreover, the strength of calculated the H-bonds in neighbor chain of Aß1-42 fibrils indicated that the mild interactions between silicene and fibrils could regularize the structure of Aß1-42 fibrils and stabilize the interactions between five chains of fibrils protein, which might enhance the aggregation of Aß1-42 fibrils. This study provides a new insight for understanding the interaction between nanomaterials and biomolecules and moves forward the development of silicene into biomedical fields.

Potential toxicity mechanism of MoS2 nanotube in the interaction between YAP65 WW domain and PRM.

With the widespread application of Molybdenum disulfide (MoS2) in biomedicine, its mechanism of action with biomolecules has attracted increasing attention. Herein, molecular dynamics simulations were performed to investigate the effect of MoS2 nanotube on the binding of the signal protein YAP65, an important Yes kinase-associated protein domain (WW domain), to the proline rich motif ligand (PRM). We designed four systems based on the different initial binding modes among WW domain, PRM and MoS2 nanotube, and observed two ways to affect the binding of WW domain to PRM. The first pathway, the active site in WW domain was occupied by MoS2 nanotube, which prevents WW domain from binding to PRM. In the second pathway, WW domain was bound to PRM with residues W17 and F29 instead of the two highly conserved residues (Y28 and W39), forming an unstable combination. These two results might cause WW domain to lose its original function or to pass the mistaken signal. However, MoS2 nanotube did not destroy the structure and binding of WW domain and PRM in the composite. These findings shed light on the interaction between MoS2 nanotube and signal protein system, while providing another valuable insight into the potential nanotoxicity of MoS2 nanotube.

Target triggered fluorescence "turn-off" of silicon nanoparticles for cobalt detection and cell imaging with high sensitivity and selectivity.

Cobalt ions (Co2+) are among heavy metals ions which cause pollution in environment because of their toxicity and improper degradation. In this work, a new fluorescent approach based on silicon nanoparticles (Si NPs) was designed for Co2+ detection. The fluorescent Si NPs were prepared by mixing 3-aminopropyl trimethoxysilane (APTES) and basic fuchsin, and under the excitation of 400 nm, they emitted green fluorescence at 515 nm. The prepared Si NPs were highly soluble in water, stable to salt and pH, and their fluorescence emission was extremely constant, with the quantum yield of 2.28%. The detailed mechanism studies showed that Co2+ effectively quenched the fluorescence of Si NPs by forming static complex. After optimizing the reaction parameters, a good linear relationship for Co2+ was observed from 0.2 to 60 µM, and the limit of detection was 0.14 µM that is lower than the guideline announced by Department of Environmental Protection for drinking water (1.7 µM). The preparation method of Si NPs was cheap, rapid and simple, and the fluorescent approach was applied to determine Co2+ in Yellow river water, drinking water, and industrial wastewater. Moreover, the Si NPs has good response to exogenous Co2+ in HepG2 cell imaging.

Carbon Dots as Fluorescent/Colorimetric Probes for Real-Time Detection of Hypochlorite and Ascorbic Acid in Cells and Body Fluid.

Hypochlorite (ClO-) and ascorbic acid (AA) are reported to have a high correlation with oxidative stress and related diseases, so it is necessary and critical to develop sensitive and fast response sensors to investigate the dynamical variation of these redox substances, especially those sensors which can detect ClO- and AA in real time in two manners. However, it is still an unmet challenge for now. Herein, novel carbon dots (RD-CDs) which can respond to ClO- and AA rapidly, reversibly, and dynamically by fluorescence and colorimetry were synthesized. In the fluorescence manner, the constructed nanosensor possessed high selectivity toward ClO- in the range of 0.1-100 µM with a detection limit of 83 nM, and can be selectively recovered by AA. It endows this sensor with good capacity as a fluorescent probe for dynamic detection of ClO- and AA in living cells, which can be monitored by a fluorescence microscope. In the colorimetric manner, ClO- and AA can be detected by UV-vis in the range of 5-200 µM and 1-30 µM, respectively. The concentrations of ClO- and AA in humor can be measured by RD-CDs in both fluorescence and colorimetric mode. The results above-mentioned demonstrate its great potential in biosensing.

Target-mediated hyperbranched amplification for sensitive detection of human alkyladenine DNA glycosylase from HeLa cells.

Human alkyladenine DNA glycosylase (hAAG) is an important protein enzyme which can specifically recognize and initiate the repair of a variety of alkylated purines and hypoxanthine, and the dysregulation of hAAG activity is associated with various human diseases. Although there are several methods focusing on hAAG detection, they share common defects such as time-consuming protocols, laborious operation or requirement of expensive analytical instruments. Herein, taking advantage of the high amplification efficiency of hyperbranched signal amplification and the low background signals by modifying NH2 at 3' terminus of hairpin substrate and signal probe to prevent the terminal deoxynucleotidyl transferase (TdT)-activated nonspecific amplification, a fluoresence method for sensitive detection of hAAG was established using TdT-activated Endonuclease IV (Endo IV)-assisted hyperbranched signal amplification. This method exhibits high sensitivity with a limit of detection of 0.090 U/mL for pure hAAG and shows a large dynamic range of 3 orders of magnitude from 0.1 to 50 U/mL, and it can be applied for accurate detection of hAAG in complicated HeLa nuclear extract. Moreover, the method can be used for discrimination of hAAG from other DNA glycosylases, holding great potential in hAAG-related biomedical research and clinical diagnosis.

In situ preparation of multilayer coated capillary column with HKUST-1 for separation of neutral small organic molecules by open tubular capillary electrochromatography.

The popularity of novel nanoparticles coated capillary column has aroused widespread attention of researchers. Metal organic frameworks (MOFs) with special structure and chemical properties have received great interest in separation sciences. This work presents the investigation of HKUST-1 (Hong Kong University of Science and Technology-1, called Cu3(BTC)2 or MOF-199) nanoparticles as a new type of coating material for capillary electrochromatography. For the first time, three layers coating (3-LC), five layers coating (5-LC), ten layers coating (10-LC), fifteen layers coating (15-LC), twenty layers coating(20-LC) and twenty-five layers coating (25-LC) capillary columns coated with HKUST-1 nanoparticles were synthesized by covalent bond with in situ, layer-by-layer self-assembly approach. The results of scanning electron microscopy (SEM), X-ray diffraction (XRD) and plasma atomic emission spectrometry (ICP-AES) indicated that HKUST-1 was successfully grafted on the inner wall of the capillary. The separating performances of 3-LC, 5-LC, 10-LC, 15-LC, 20-LC and 25-LC open tubular (OT) capillary columns were studied with some neutral small organic molecules. The results indicated that the neutral small organic molecules were separated successfully with 10-LC, 15-LC and 20-LC OT capillary columns because of the size selectivity of lattice aperture and hydrophobicity of organic ligands. In addition, 10-LC and 15-LC OT capillary columns showed better performance for the separation of certain phenolic compounds. Furthermore, 10-LC, 15-LC and 20-LC OT capillary columns exhibited good intra-day repeatability with the relative standard deviations (RSDs; %) of migration time and peak areas lying in the range of 0.3-1.2% and 0.5-4.2%, respectively. For inter-day reproducibility, the RSDs of the three OT capillary columns were found to be lying in the range of 0.3-5.5% and 0.3-4.5% for migration time and peak area, respectively. The RSDs of retention times for column-to-column for three batches of 10-LC, 15-LC and 20-LC OT capillary columns were in the range from 2.3% to 7.2%. Moreover, the fabricated 10-LC, 15-LC and 20-LC OT capillary columns exhibited good repeatability and stability for separation, which could be used successively for more than 120 runs with no observable changes on the separation efficiency.

Ratiometric Detection of Intracellular Lysine and pH with One-Pot Synthesized Dual Emissive Carbon Dots.

Recently, the development of new fluorescent probes for the ratiometric detection of target objects inside living cells has received great attention. Normally, the preparation, modification as well as conjugation procedures of these probes are complicated. On this basis, great efforts have been paid to establish convenient method for the preparation of dual emissive nanosensor. In this work, a functional dual emissive carbon dots (dCDs) was prepared by a one-pot hydrothermal carbonization method. The dCDs exhibits two distinctive fluorescence emission peaks at 440 and 624 nm with the excitation at 380 nm. Different from the commonly reported dCDs, this probe exhibited an interesting wavelength dependent dual responsive functionality toward lysine (440 nm) and pH (624 nm), enabling the ratiometric detection of these two targets. The quantitative analysis displayed that a linear range of 0.5-260 µM with a detection limit of 94 nM toward lysine and the differentiation of pH variation from 1.5 to 5.0 could be readily realized in a ratiometric strategy, which was not reported before with other carbon dots (CDs) as the probe. Furthermore, because of the low cytotoxicity, good optical and colloidal stability, and excellent wavelength dependent sensitivity and selectivity toward lysine and pH, this probe was successfully applied to monitor the dynamic variation of lysine and pH in cellular systems, demonstrating the promising applicability for biosensing in the future.

Ultrathin polydopamine film coated gold nanoparticles: a sensitive, uniform, and stable SHINERS substrate for detection of benzotriazole.

In shell-isolated nanoparticle (NP)-enhanced Raman spectroscopy (SHINERS), traditional metal oxide-based shells have inferior chemical inertness, they require strict preparation conditions, and lack specific groups, which lead to their poor selectivity toward target molecules. In this study, ultrathin and compact gold (Au)@polydopamine (PDA) SHINERS NPs were successfully fabricated by a simple self-polymerization technique. High wrapping tendency of PDA, a multifunctional biopolymer, favored the fabrication process. Au@PDA NPs exhibited a typical shell-isolated effect, i.e., Au@PDA NPs with a thick shell (more than 2.3 nm) showed a lower SERS activity, while those with an ultrathin (1.3 nm) shell exhibited higher SERS activity compared to uncoated Au NPs. The Au@PDA SHINERS substrate shows high performance in terms of sensitivity, uniformity, and stability. The relative standard deviations (RSDs) of SERS intensities from ten positions on the same substrate were less than 4%. Their Raman intensities dropped by only 15% over two months. More importantly, the Au@PDA (1.3 nm) SHINERS substrate exhibited high SERS activity for label-free and quantitative detection of benzotriazole (BTA), an important corrosion inhibitor, through utilizing a presumed π-π stacking interaction. A broad linear range from 10-4 to 10-8 M was achieved with a low detection limit (LOD) of 1 nM (0.119 µg L-1). The LOD was not only significantly lower than the maximum allowable level (20 µg L-1) of the Australian government water guide, but also lower than that of some modern methods such as fluorescence, liquid chromatography, and gas chromatography coupled with mass spectrometry. Furthermore, the substrate showed excellent discrimination against other compounds with a single aromatic ring. It is expected that the Au@PDA SHINERS substrate will offer great potential for analysis application in a complicated environmental system.

Red Emission B, N, S-co-Doped Carbon Dots for Colorimetric and Fluorescent Dual Mode Detection of Fe3+ Ions in Complex Biological Fluids and Living Cells.

Colorimetric and fluorescent dual mode detection methods have gained much attention in recent years; however, it is still desirable to develop new colorimetric and fluorescent dual mode nanosensors with more simple preparation procedures, low cost, and excellent biocompatibility. Herein, a colorimetric and fluorescent nanosensor based on B, N, S-co-doped carbon dots (BNS-CDs) was synthesized by one-step hydrothermal treatment of 2,5-diaminobenzenesulfonic acid and 4-aminophenylboronic acid hydrochloride. Using this nanosensor, a highly sensitive assay of Fe3+ in the range of 0.3-546 µM with a detection limit of 90 nM was provided by quenching the red emission fluorescence. It is more attractive that Fe3+ can also be visualized by this nanosensor via evident color changes of the solution (from red to blue) under sunlight without the aid of an ultraviolet (UV) lamp. Furthermore, the designed nanosensor can be applied for efficient detection of intracellular Fe3+ with excellent biocompatibility and cellular imaging capability, and it holds great promise in biomedical applications.

Fluorescent carbon nanoparticles: A low-temperature trypsin-assisted preparation and Fe(3+) sensing.

In recent years, extensive researches are focused on the fluorescent carbon nanoparticles (CNPs) due to their excellent photochemical, biocompatible and water-soluble properties. However, these synthesis methods are generally suffered from tedious processes. In this paper, fluorescent carbon nanoparticles are synthesized by a facile, one-pot, low-temperature method with trypsin and dopamine as precursors. The synthesis process avoids any heating operation and organic solvent, which provides a "green" and effective preparation route. The obtained CNPs exhibit excellent water-solubility, salt-tolerance and photostability. Based on the synergistic action of the inner filter effect and static quenching mechanism, the CNPs are exploited as a "turn-off" fluorescence sensor for sensitive and selective detection of Fe(3+) ions. The probe shows a wide linear range from 0.1 to 500 µM, with a limit of detection of 30 nM. Furthermore, the as-fabricated fluorescent sensing system is successfully applied to the analysis of Fe(3+) in biological samples such as human urine and serum samples with satisfactory recoveries (92.8-113.3%).

Fluorescence resonance energy transfer-based ratiometric fluorescent assay for highly sensitive and selective determination of sulfide anions.

A novel and effective ratiometric fluorescence strategy was developed for rapidly, sensitively and selectively probing sulfide anions (S(2-)). A dual-emission nanosensor was prepared by covalently attaching fluorescent carbon nanoparticles (CNPs) to gold nanoclusters (Au NCs), triggering the sensing mechanism of fluorescence resonance energy transfer (FRET) from CNPs (donor) to Au NCs (acceptor). Once S(2-) was added, considerable fluorescence recovery of CNPs and quenching of Au NCs were observed due to the inhibition of FRET progress via the formation of Au2S. The ratiometric probe showed good, specific S(2-) sensing behavior and high sensitivity with a detection limit of 18 nM. Significantly, the assay was successfully employed to determine the S(2-) content in biological and water samples, presenting immense promise in the biological and environmental fields.

RfiA, a novel PAP2 domain-containing polytopic membrane protein that confers resistance to the FtsZ inhibitor PC190723.

BACKGROUND: As an essential protein for bacterial cell division, the tubulin-like FtsZ protein has been selected as a target for development of next generation antimicrobials. PC190723 is a fluoride-containing benzamide compound developed as a FtsZ inhibitor that selectively inhibits growth of multidrug resistant Gram-positive bacteria. AIM: Our aim was to investigate the mechanism of resistance to PC109723 conferred by over-expression of a gene, rfiA, in an environmental bacterium Arthrobacter A3. MATERIALS & METHODS: The investigations included analysis of the effect of PC109723 on wild-type Arthrobacter A3 and a recombinant strain over-expressing rfiA, in vivo localization of RfiA, in vitro measurements of fluorine release from PC109723 by membrane extracts from the over-expression strain combined with mass spectrophotometric analysis of reaction products, and modelling of RfiA structure. RESULTS: We describe a novel protein, RfiA, from Arthrobacter A3 that confers PC190723 resistance. RfiA is a PAP2 domain-containing polytopic transmembrane protein that can modify the fluoridated benzamide ring that is critical for high affinity binding of PC190723 with FtsZ. CONCLUSION: RfiA-mediated modification of PC190723 is the first reported instance of resistance to this antibiotic involving a change to its structure. We predict that adoption of PC190723 or related benzamides as antimicrobials in clinical practice will lead to the acquisition by resistant pathogens of a gene encoding this subfamily of proteins.

The peroxidase/catalase-like activities of MFe2O4 (M=Mg, Ni, Cu) MNPs and their application in colorimetric biosensing of glucose.

MFe2O4 (M=Mg, Ni, Cu) magnetic nanoparticles (MNPs) were found to have catalytic activities similar to those of biological enzymes such as catalase and peroxidase. These nanomaterials, as bifunctional catalase/peroxidases (KatGs), not only could catalyze H2O2 to produce hydroxyl radicals, which oxidized peroxidase substrate to produce color, but also could catalyze the decomposition reaction of H2O2 into water and oxygen directly in the same condition through the catalase-like activity. And it was also found that the amount of generated hydroxyl radicals and oxygen was related to the concentration of MFe2O4 (M=Mg, Ni, Cu) MNPs. The peroxidase-like catalytic behavior of MFe2O4 MNPs was analyzed in detail. Under the optimized conditions, NiFe2O4 MNPs were used as a colorimetric biosensor for the detection of 9.4×10(-7)-2.5×10(-5) mol L(-1) glucose with a limit of detection (LOD) of 4.5×10(-7) mol L(-1). The sensor was successfully applied to glucose detection in urine sample.

Probing the mechanism of the interaction between l-cysteine-capped-CdTe quantum dots and Hg(2+) using capillary electrophoresis with ensemble techniques.

A good understanding of the mechanism of interaction between quantum dots (QDs) and heavy metal ions is essential for the design of more effective sensor systems. In this work, CE was introduced to explore how l-cysteine-capped-CdTe QDs (l-cys-CdTe QDs) interacts with Hg(2+) . The change in electrophoretic mobility can synchronously reflect the change in the composition and property of QDs. The effects of the free and capping ligands on the system are discussed in detail. ESI-MS, dynamic light scattering (DLS), zeta potential, and fluorescence (FL) were also applied as cooperative tools to study the interaction mechanism. Furthermore, the interaction mechanism, which principally depended on the concentration of Hg(2+) , was proposed reasonably. At the low concentration of Hg(2+) , the formation of a static complex between Hg(2+) and the carboxyl and amino groups of l-cys-CdTe QDs surface was responsible for the FL quenching. With the increase of Hg(2+) concentration, the capping l-cys was stripped from the surface of l-cys-CdTe QDs due to the high affinity of Hg(2+) to the thiol group of l-cys. Our study demonstrates that CE can reveal the mechanism of the interaction between QDs and heavy metal ions, such as FL quenching.

Protein adsorption on citrate modified magnetic nanoparticles.

Magnetic iron oxide nanoparticles were prepared by chemical co-precipitation method and then modified with sodium citrate. These iron oxide nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM). BSA was adsorbed on these citrate modified nanoparticles using two types of buffers (acetate buffer, pH 4.0, 4.7 and phosphate buffer, pH 7.4). The results showed that the maximum adsorption of BSA was 83 mg/g at its isoelectric point (pH 4.7). Fourier-transform infrared spectroscopy (FTIR) was used to confirm the attachment of citrate groups and BSA on the prepared magnetic nanoparticles. BSA was desorbed from nanoparticles under alkaline conditions, which was confirmed by SDS-PAGE electrophoresis, UV-vis and fluorescence spectra. The desorbed BSA showed small changes in its structure. The adsorption results indicated that BSA adsorption on citrate modified iron oxide nanoparticles occurred mainly by electrostatic mechanism.

Colorimetric detection of urine glucose based ZnFe2O4 magnetic nanoparticles.

In this paper, we discovered that ZnFe(2)O(4) magnetic nanoparticles (MNPs) possess intrinsic peroxidase-like activity. ZnFe(2)O(4) MNPs exhibit several advantages such as high catalytic efficiency, good stability, monodispersion, and rapid separation over other peroxidase nanomimetics and horseradish peroxidase (HRP). ZnFe(2)O(4) MNPs were used as a colorimetric biosensor for the detection of urine glucose. This method is simple, inexpensive, highly sensitive, and selective for glucose detection using glucose oxidase (GOx) and ZnFe(2)O(4) MNPs with a linear range from 1.25 × 10(-6) to 1.875 × 10(-5) mol L(-1) with a detection limit of 3.0 × 10(-7) mol L(-1). The color change observable by the naked eyes based on the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) is the principle for the sensing of urine glucose level.