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Optical biosensors have become powerful tools for bioanalysis, but most of them are limited by optic damage, autofluorescence, as well as poor penetration ability of ultraviolet (UV) and visible (Vis) light. Herein, a near-infrared light (NIR)-driven photoelectrochemical (PEC)-fluorescence (FL) dual-mode biosensor has been proposed for ultrasensitive detection of microRNA (miRNA) based on bipedal DNA walker with cascade amplification. Fueled by toehold-mediated strand displacement (TMSD), the bipedal DNA walker triggered by target miRNA-21 is formed through catalytic hairpin assembly (CHA), which can efficiently move along DNA tracks on CdS nanoparticles (CdS NPs)-modified fluorine doped tin oxide (FTO) electrode, resulting in the introduction of upconversion nanoparticles (UCNPs) on electrode surface. Under 980 nm laser irradiation, the UCNPs serve as the energy donor to emit UV/Vis light and excite CdS NPs to generate photocurrent for PEC detection, while the upconversion luminescence (UCL) at 803 nm is monitored for FL detection. This PEC-FL dual-mode biosensor has achieved the ultrasensitive and accurate analysis of miRNA-21 in human serum and different gynecological cancer cells. Overall, the proposed dual-mode biosensor can not only couple the inherent features of each single-mode biosensor but also provide mutual authentication of testing results, which opens up a new avenue for early diagnosis of miRNA-related diseases in clinic. [ABSTRACT FROM AUTHOR]

• The mechanism of action of water on the efficiency of laser rock breaking was studied. • The spatial distribution characteristics of cracks in the rock were quantitatively analyzed. • The mechanical properties of rocks with different water content states after laser irradiation were studied. Laser technology has a wide range of application prospects as a novel means of assisting rock breaking. The realization of efficient laser-assisted breaking of deep hard rocks is based on revealing the mechanism of the saturated fluid increase or inhibition of laser-weakened rock. The laser irradiation of basalt with different water contents was used to analyze the mechanical response characteristics and investigate the destruction law of basalt under different laser power irradiations to explore the mechanism of the influence of water on the effect of laser rock breaking. The results show that the presence of water can significantly increase the drilling depth, and a laser irradiation of 1250 W can penetrate 56.5 mm deep into the rock in 30 s. The uniaxial compressive strength of basalt was reduced by a maximum of 38.23 % and the modulus of elasticity by a maximum of 74.99 % after the laser irradiation. Under low- power conditions, water has a positive effect on the laser rock-breaking efficiency. After 30 s of a laser irradiation in the range of 250–750 W, the uniaxial compressive strength of the water-saturated rock (WSR) samples was 12.64–13.43 % less than that of the original rock (OR) samples, and that of the natural state rock (NSR) samples was 1.09–3.93 % less than that of the OR samples. Both acoustic emission events and basalt energy significantly increased after a laser irradiation, and water promoted the expansion of rock microcracks. The degree of rock fragmentation increased with an increasing laser power. Laser irradiation can significantly reduce the strength of the rock, and water can effectively promote a low-power laser to break the rock, which is effective in reducing the difficulty and improving the efficiency of rock breaking. The obtained results provide theoretical and technical support for the application of the laser technology in the effective crushing of deep hard rock, and efficient and safe exploitation of deep resources. [ABSTRACT FROM AUTHOR]

Spermidine, a natural polyamine, has been proven antioxidant function, but its pathway and mechanism of action remain unclear. Based on the oxidative stress model by 3-nitropropionic acid (3-NPA), the study explored the pathways by spermidine to rescue oxidative stress via autophagic process in goose granulosa cells by RNA-seq and RNA interference. In transcriptional regulation, in addition to KEGG pathways related to cell proliferation and differentiation, lots of KEGG pathways associated with inflammation, metabolism, and signaling were also significantly enriched in 3-NPA vs. 3-NPA + spermidine treatments. Six key genes (JUN , CD44 , KITLG , RND2 , BMP4 and KALRN) involved in spermidine-mediated anti-oxidative stress were screened. Furthermore, the experimental results showed that spermidine (80 μmol/L) significantly increased autophagic gene expression in goose granulosa cells, while EP300 -siRNA or MAP1S -siRNA also significantly increased autophagic process. The autophagic gene expressions were no difference between EP300 -siRNA and EP300 -siRNA + spermidine treatments, although spermidine significantly increased autophagic process of granulosa cells compared to MAP1S -siRNA alone. In addition, inhibition of mTOR pathway significantly increased autophagic gene expression, which was further enhanced by spermidine in combined with mTOR inhibitor. These results suggest that spermidine can alleviate oxidative stress by inducing autophagy regulated by EP300, MAP1S and mTOR as well as regulating other independent gene expressions in goose granulosa cells. • Spermidine improves oxidative stress in goose GCs by regulating autophagy and other independent gene expressions. • Transcriptomic techniques confirmed the target genes related to spermidine anti-oxidative stress by spermidine. • The autophagy pathway involved in anti-oxidative stress by spermidine was validated by gene interference analyses. [ABSTRACT FROM AUTHOR]

Pathogens cause infections and millions of deaths globally, while antipathogens are drugs or treatments designed to combat them. To date, multifunctional nanomaterials (NMs), such as organic, inorganic, and nanocomposites, have attracted significant attention by transforming antipathogen livelihoods. They are very small in size so can quickly pass through the walls of bacterial, fungal, or parasitic cells and viral particles to perform their antipathogenic activity. They are more reactive and have a high band gap, making them more effective than traditional medications. Moreover, due to some pathogen's resistance to currently available medications, the antipathogen performance of NMs is becoming crucial. Additionally, due to their prospective properties and administration methods, NMs are eventually chosen for cutting-edge applications and therapies, including drug administration and diagnostic tools for antipathogens. Herein, NMs have significant characteristics that can facilitate identifying and eliminating pathogens in real-time. This mini-review analyzes multifunctional NMs as antimicrobial tools and investigates their mode of action. We also discussed the challenges that need to be solved for the utilization of NMs as antipathogens. [ABSTRACT FROM AUTHOR]

Spermidine have been reported a role in antioxidative, antiaging, and antiinflammatory. Oxidative stress causes granulosa cell (GC) apoptosis, follicular atresia, and impairs poultry reproductive functions. Studies have found that autophagy is the protective mechanism against antioxidant stress and apoptosis in cells. However, the relationship between spermidine-induced autophagy, oxidative stress, and apoptosis in goose GCs remains unclear. In this study, we investigated the autophagy mechanism to mediate spermidine effects on the alleviation of oxidative stress and apoptosis in goose GCs. Follicular GCs were treated with spermidine combination with 3-Nitropropanoic acid (3-NPA), rapamycin (RAPA), and chloroquine (CQ) or with hydrogen peroxide, RAPA, and CQ. Spermidine upregulated the ratio of LC3-II/I, inhibited the accumulation of p62 protein, and induced autophagy. 3-NPA treatment significantly increased ROS production, MDA content, SOD activity, cleaved CASPASE-3 protein expression, and decreased BCL-2 protein expression in follicular GCs. Spermidine inhibited oxidative stress and apoptosis induced by 3-NPA. In addition, hydrogen peroxide-induced oxidative stress was inhibited by spermidine. However, the inhibitory effect of spermidine was eliminated under chloroquine. Our results demonstrated that spermidine relieved oxidative stress and apoptosis of GCs by inducing autophagy, indicating that spermidine has a great potential to maintain proteostasis and sustain granulosa cell viability in geese. [ABSTRACT FROM AUTHOR]

A novel magnetic nanozyme Fe3O4@MXene-Au nanocomposite, which possessed higher peroxidase-like activity than that of Fe3O4 nanoparticles and Fe3O4@MXene nanocomposites, was developed. The outstanding magnetic properties of the nanozyme endowed it with the ability of simple and rapid separation, achieving great recyclability. Based on Fe3O4@MXene-Au nanocomposites and glucose oxidase (Glu Ox), a highly selective colorimetric biosensor for glucose detection was developed. Fe3O4@MXene-Au nanocomposites can catalyze H2O2 produced from glucose catalyzed by glucose oxidase to ·OH and oxidize colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) with a significant absorbance at 652 nm. The linear range of glucose was 0–1.4 mM under optimal conditions, with a limit of detection (LOD) of 0.11 mM. Glucose in human whole blood was successfully detected with satisfactory recoveries. Furthermore, a facile agarose hydrogel detection platform was designed. With smartphone software, glucose detection can be realized by the agarose hydrogel platform, demonstrating the potential in on-site and visual detection of glucose. [ABSTRACT FROM AUTHOR]

Graphene and graphene oxides have outstanding electrical and optical properties, making it particularly interesting in the field of gas sensing. In this study, colorimetric humidity sensor based on graphene oxide (GO) thin film on different substrates was fabricated by using dip coating technique. The fabrication conditions that influence the humidity response were systematically investigated and optimized. Our results indicated that GO thin film on metallized polyethylene terephthalate (mPET) film displayed poor resolution and sensitivity if it was fabricated from aqueous dispersion. However, both spectra resolution and reflectance color of GO film on mPET are enhanced, if it was fabricated from acetone dispersion. It was attributed to the wetting property of solvent that help to form uniform d -spacing of GO sheet assemblies as revealed from XRD analysis. Bending test of the formed GO film on mPET showed an extreme spectra stability upon 10,000 cycles of bending, suggesting that the devices are quite suitable for flexible device applications in both personal physiological condition monitoring and environment condition change detection. Image 1 • Fabrication of graphene oxide films on flexible substrates by using dip-coating technique. • Optical properties of the films were remarkably affected by substrate, pulling rate and solvent. • Factors that influence humidity detection were optimized. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective electrochemical biosensor for Pb2+ with a dual-amplification strategy is proposed. The first amplification step was realized by the cycle of Pb2+ and 8–17 DNAzyme (S2), and the hybridization chain reaction (HCR) triggered by S1 further amplified the electrochemical signal. Fe3O4@Au NPs, as a multifunctional magnetic carrier, is not only manifested in the construction of a magnetically controlled electrochemical response interface, but also has significant contribution in the purifying system, reducing interference, increasing the specific surface area, and the DNA loading. The magnetic nanocomposites were characterized by TEM as spheres with particle size of around 39 nm. When there was no Pb2+, long double-strand DNA (dsDNA) is formed on the surface of Fe3O4@Au NPs by the S1-triggered HCR; in the presence of Pb2+, S2 is activated and S1 on the surface of magnetic biocomposites (Fe3O4@Au NPs-S1) is continuously cleaved with the cycle of Pb2+ and S2, leading to a significant decrease of methylene blue (MB) absorbed on dsDNA. Such reverse dual-signal amplification strategy effectively increased the current difference and improved the sensitivity of the proposed sensor. The electrochemical signal of MB was obtained by differential pulse voltammetry (DPV) with preconcentration, showing a linear response toward Pb2+ ranging from 50 pM to 1 μM with a detection limit of 15 pM. The proposed method has feasible applications in detecting other heavy metal ions based on other metal-dependent DNAzyme. [ABSTRACT FROM AUTHOR]

A novel electrochemical and fluorescence dual-signal assay was developed for the determination of hydrogen peroxide (H2O2) based on Fe3O4@MnO2 and N-doped carbon dots (NCDs). Fe3O4@MnO2 was not only applied as the recognizer for H2O2 but also served as the fluorescence quencher and electrochemical enhancer. This permits the dual-signal readout of the analytical system. In the absence of H2O2, the NCDs were quenched by Fe3O4@MnO2, and the oxidation of the electrochemical probe ferrocene (Fc) was catalyzed by Fe3O4@MnO2. In the presence of H2O2, MnO2 was reduced to Mn2+, leading to the fluorescence recovery of NCDs and the reduction in the oxidation signal of Fc. By combining the electrochemical method and the fluorescence assay, more comprehensive and valuable information for H2O2 determination was provided to meet different analytical demands. The method exhibits good repeatability and selectivity with a detection limit of 1.0 μM for the fluorescence assay and 0.6 μM for the electrochemical method. The proposed approach holds great potential for probing released targets from living cells. [ABSTRACT FROM AUTHOR]

Amperometry with nanotip electrodes has been applied to show cocaine and methylphenidate not only trigger declines in vesicle content and exocytotic catecholamine release in a model cell line but also differentially change the fraction of transmitter released from each individual vesicle. In addition, cocaine accelerates exocytotic release dynamics while they remain unchanged after methylphenidate treatment. The parameters from pre‐spike feet for the two drugs are also in opposition, suggesting this aspect of release is affected differentially. As cocaine and methylphenidate are psychostimulants with similar pharmacologic action but have opposite effects on cognition, these results might provide a missing link between the regulation of exocytosis and vesicles and the effect of this regulation on cognition, learning, and memory. A speculative chemical mechanism of the effect of these drugs on vesicle content and exocytosis is presented. All around my brain: Single‐cell amperometry and intracellular vesicle impact electrochemical cytometry with nanotip electrodes were employed to investigate the effects of cocaine and methylphenidate on exocytosis and the fraction of chemical release in PC12 cells. These drugs have differential effects on exocytosis dynamics as well as the release fraction. [ABSTRACT FROM AUTHOR]

Amperometry with nanotip electrodes has been applied to show cocaine and methylphenidate not only trigger declines in vesicle content and exocytotic catecholamine release in a model cell line but also differentially change the fraction of transmitter released from each individual vesicle. In addition, cocaine accelerates exocytotic release dynamics while they remain unchanged after methylphenidate treatment. The parameters from pre‐spike feet for the two drugs are also in opposition, suggesting this aspect of release is affected differentially. As cocaine and methylphenidate are psychostimulants with similar pharmacologic action but have opposite effects on cognition, these results might provide a missing link between the regulation of exocytosis and vesicles and the effect of this regulation on cognition, learning, and memory. A speculative chemical mechanism of the effect of these drugs on vesicle content and exocytosis is presented. [ABSTRACT FROM AUTHOR]

Abstract Sensitive and efficient detection of protein markers, such as transcription factors (TFs), is an important issue in postgenomic era. In this paper, we report a DNA nanodevice, allosteric DNA-silver nanocluster switches (AgSwitches), for TFs detection. The mechanism of this nanodevice is based on the binding-induced allostery whereby the binding between AgSwitches and TFs alters the conformation of AgSwitches. This alteration brings DNA-silver nanocluster (DNA-AgNCs) and guanine-rich enhancer sequences (GRS) into close proximity, generating fluorescent enhancement for quantifications. Our results revealed that the sequence design of AgSwitches can be rationally optimized according to stimulated free energy, and we demonstrated that this method can not only be used for detecting TFs in nuclear extracts of cells, but also be developed as a tool for screening inhibitors of TFs. Overall, this work expanded the category allosteric DNA nanodevices by first introducing DNA-AgNCs into this area, and the obtained method was efficient for TFs-related investigations. Graphical abstract Image 1 Highlights • DNA-AgNCs are first introduced into designing allosteric probes. • The first label-free allosteric nanodevice for fluorescent TFs detection. • Design of the probe can be optimized with the help of free online servers. • Easy monitoring of TFs in cell nuclear extracts is implementable. • The IC 50 of compounds towards target TFs can be facilely calculated by this method. [ABSTRACT FROM AUTHOR]

Abstract Herein, a novel magnetic biocomposite (Fe 3 O 4 @Au-S1/S2) was applied to analyze thrombin. The Fe 3 O 4 @Au-S1/S2 consisted of Fe 3 O 4 @Au nanoparticles (Fe 3 O 4 @Au NPs) as carriers for magnetic separation and magnetic field-induced self-assembly, thiolated complementary strand (S1) anchored based on Au-S bond and thrombin binding aptamer (S2) as a recognition element. As a redox indicator, methylene blue (MB) can be adsorbed to DNA anchored on the surface of Fe 3 O 4 @Au NPs by electro-static interaction. In the absence of thrombin, MB were adsorbed on double-stranded DNA (S1/S2) which anchored on Fe 3 O 4 @Au NPs and a high electrochemical signal of MB was recorded by Differential pulse voltammetry. Conversely, the complementary strand (S1) exposed after thrombin competitively bonded with aptamer. The introduction of Pb2+-dependent DNAzyme (S3) split S1 at specific rA site, resulting in the significantly decreased adsorption capacity of MB. Thus, the thrombin detection could be recorded by monitoring the electrochemical signal reduction of MB through incubation of thrombin with S3. This method exhibited a high sensitivity toward thrombin with a broad linear range from 5 pmol L−1 to 5 nmol L−1 and a limit of detection of 1.8 pmol L−1. Graphical abstract Image 1 Highlights • Novel magnetic biocomposites consist of Fe 3 O 4 @Au for magnetic field directed self-assembly and aptamer for high selectivity. • Electrochemical signal enhanced 3 times by the catalyzing cleavage of Pb2+-dependent DNAzyme. • A label-free electrochemical aptasensor opens a promising avenue for the detection of thrombin and other clinical biomarkers. [ABSTRACT FROM AUTHOR]

Highlights • A synthetic biomimetic SERS sensor for highly specific and sensitive detection of ACP is realized. • Boronate affinity-based surface imprinting approach is applied for specific extraction of trace targets. • The approach shows great versatility by imprinting different glycoproteins. Abstract In this paper, we introduce a synthetic biomimetic receptors-based surface enhanced Raman scattering (SERS) sensor for highly specific recognition and detection of acid phosphatase in complex biological samples. It depends on the establishment of molecular imprinted polymers (MIPs) which capture the target glycoprotein via biomimetic recognition, and SERS probes which bind to glycoproteins by boronate affinity. The MIPs layer was synthesized through self-polymerization of dopamine on the surface of glycoprotein-immobilized polymeric skeletons, which was prepared by choosing 4-vinylphenylboronic acid (VPBA) as functional monomers, pentaerythritol triacrylate (PETA) as crosslinker, ethyleneglycol (EG) and cyclohexanol as porogens. The accessible and stable recognition sites allowed the rebinding of the template and offered good reproducibility. The proposed biomimetic recognition-based SERS sensor showed superb performances for acid phosphatase detection with high sensitivity (LOD of 0.1 ng mL−1) and excellent selectivity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Label-free and enzyme-free multiplexed detection of TFs is first realized. • PPyNPs is first applied in detection of transcription factors. • Absorption and desorption process between DNA-AgNCs and PPyNPs is first described. • Multiplexed detection of NF-κB p50 and p53 in cell nuclear extracts is implementable. • Facile evaluation of TFs inhibitors is realized. Abstract Transcription factors (TFs) regulate information flow from gene to protein, and they are recognized as key indicators to reflect cellular processes. Facile monitoring of TFs may aid diagnostics and treatment, but we still lack of techniques for highly efficient detection of them. In this research, a hybrid material consisting of DNA-silver nanoclusters (DNA-AgNCs) and polypyrrole nanoparticles (PPyNPs) was built for TFs detection. The designed DNA-AgNCs have a hairpin-shaped nucleic acid architecture with a double-stranded stem for recognizing TFs and a single-stranded loop for interacting with PPyNPs. In the absence of TFs, DNA-AgNCs are absorbed to PPyNPs, resulting in fluorescent quenching. While in the presence of TFs, the binding between TFs and the DNA-AgNCs caused desorption of DNA-AgNCs via steric hindrance mechanism. Accordingly, the increase of fluorescence derived from desorption is used for quantifications. Derived from low non-specific protein absorption features of PPyNPs, detection limit of 70 pM for NF-κB p50 and 110 pM for p53 were obtained. Then, by absorbing two kinds of DNA-AgNCs to PPyNPs, label-free multiplexed detection of TFs was first realized. Additionally, we suggested that this platform can be developed for drug screening by evaluating inhibitory effect of a pair of optical isomers towards TFs. [ABSTRACT FROM AUTHOR]

It has been demonstrated that acetylcholinesterase (AChE) contributed significantly to the maintenance of normal cholinergic neurophysiology, and its abnormal expression has been linked to several diseases. Due to intrinsic self-confirmation and self-adjustment, multi-mode detection was able to provide more dependable and accurate results when compared to commonly used single-signal detection. Despite this, the problem of achieving multi-mode analysis of AChE has not been solved. In this study, we developed a dual-mode approach to determine AChE by multifunctional BSA-MnO 2 QDs with oxidase-mimetic activity. A visible color signal was induced by BSA-MnO 2 QDs which exhibit good oxidase-mimetic activity to oxidize 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to blue oxide; by employing AChE to hydrolyze acetylthiocholine (ATCh), the generated thiocholine (TCh) can inhibit BSA-MnO 2 QDs activity, that displayed an outstanding fluorescence signal but the oxidase-mimetic activity decreased. Following this principle, dual-mode determination of AChE with high sensitivity was achieved. By analyzing real samples, it was verified that the method demonstrated excellent interference tolerance and reliability. In addition to having excellent properties and practicability, the proffered dual-mode method was likely to be an effective method for detecting AChE with high efficiency and reliability. ● A new type of bifunctional nanozyme BSA-MnO 2 QDs with oxidase-mimetic activity. ● The fluorescence and colorimetric dual-mode sensor based on BSA-MnO 2 QDs. ● A new accurate multi-channel analysis strategy for acetylcholinesterase detection. ● A new way for the mixed determination of organophosphorus pesticides. [ABSTRACT FROM AUTHOR]

In this work, based on purifying the analysis system by magnetic separation, we constructed a turn-on fluorescent assay for highly sensitive detection of possible biomarkers, employing adenosine as the model target analyte. Aptamer labeled-carbon dots (Apt-CDs) was applied as fluorescence probes as well as selective recognition elements, while Fe 3 O 4 @polypyrrole (Fe 3 O 4 @PPY) was used as fluorescence quenching and magnetic separating materials for system purification. In absence of adenosine, the Apt-CDs were attached to the surface of PPY through π-π stacking and hydrophobic interaction and its fluorescence was quenched by Fe 3 O 4 @PPY. In presence of adenosine, the aptamer could specifically bind with adenosine to form a three dimensional Apt-CDs-adenosine complex and detach from PPY, leading to the fluorescence recovery of Apt-CDs. More importantly, with analysis system purification via twice convenient magnetic separations of free CDs and Apt-CDs-adenosine complex respectively, the detection limit could be reduced from 8 nmol L −1 to 0.15 nmol L −1 . This concept offers potential application for simple, rapid, cost-effective, and highly sensitive assay of biological samples. [ABSTRACT FROM AUTHOR]

The authors describe a new kind of adenosine triphosphate (ATP) assay. It is based on the use of gold nanoparticles (AuNPs) coated with 4-mercaptophenylboronic acid (MPBA) as the recognition element for ATP. MPBA has a specific affinity for AuNPs through Au-S interaction, and three boronic acid groups undergo condensation to form a boroxine ring. This induces the aggregation of AuNPs and a visible color change from red to blue. However, in the presence of ATP, the boronic acid group of MPBA preferentially binds to the 2', 3'-hydroxy group of ATP to form a stable boronate ester. Hence, the aggregation of AuNPs is progressively decreased as the concentration of ATP increases, and the color change is increasingly reversed. The ratio of absorbance at 520 and 683 nm increases linearly in the 8 to 100 μM ATP concentration range, with a 0.12 μM limit of detection (at an S/N ratio of 3 σ). The colorimetric assay was successfully applied to the determination of ATP in T47D breast cancer cells and in cultured cells with added anticarcinogen. [ABSTRACT FROM AUTHOR]

In this paper, a novel turn-on fluorescence aptasensor has been designed for adenosine detection based on fluorescence resonance energy transfer (FRET) from single-stranded DNA labeled carbon dots (ssDNA-CDs) to aptamer modified gold nanoparticles (aptamer-AuNPs). In the absence of adenosine, the fluorescence of ssDNA-CDs was quenched by aptamer-AuNPs via the formation of an aptamer–ssDNA duplex. The introduced adenosine competed to displace ssDNA-CDs by specifically binding to the aptamer, resulting in the recovery of the quenched fluorescence of ssDNA-CDs. Under optimized conditions, the increase in fluorescence intensity was proportional to the concentration of adenosine with a linear range of 10–500 nM and allowed a limit of detection as low as 4.2 nM. In addition, this method was successfully applied to adenosine determination in human serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Adenosine is an endogenous nucleotide pivotally involved in nucleic acid and energy metabolism. Its excessive existence may indicate tumorigenesis, typically lung cancer. Encouraged by its significance as the clinical biomarker, sensitive assay methods towards adenosine have been popularized, with high cost and tedious procedures as the inevitable defects. Herein, we report a label-free aptamer-based exonuclease III (Exo III) amplification colorimetric aptasensor for the highly sensitive and cost-effective detection of adenosine. The strategy employed two unlabeled hairpin DNA oligonucleotides (HP1 and HP2), where HP1 contained the aptamer towards adenosine and HP2 embedded the guanine-rich sequence (GRS). In the presence of adenosine, hairpin HP1 could form specific binding with adenosine and trigger the unfolding of HP1's hairpin structure. The resulting adenosine-HP1 complex could hybridize with HP2, generating the Exo III recognition site. After Exo III-assisted degradation, the GRS was released from HP2, and the adenosine-HP1 was released back to the solution to combine another HP2, inducing the cycling amplification. After multiple circulations, the released ample GRSs were induced to form G-quadruplex, further catalyzing the oxidation of TMB, yielding a color change which was finally mirrored in the absorbance change. On the contrary, the absence of adenosine failed to unfold HP1, remaining color unchanged eventually. Thanks to the amplification strategy, the limit of detection was lowered to 17 nM with a broad linear range from 50 nM to 6 μM. The proposed method was successfully applied to the detection of adenosine in biological samples and satisfying recoveries were acquired. [ABSTRACT FROM AUTHOR]

Chiral selector-functionalized magnetic nanoparticles were achieved by self-assembly anchoring L-cysteine (L-Cys) on the surface of the Au/Fe 3 O 4 nanocomposites, which was synthesized via a facile in-situ reduction process. The as-prepared L-Cys-Au/Fe 3 O 4 magnetic nanoparticles (MNPs) were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy and electrochemical methods The typical MNPs with uniform globular morphology not only can provide the enhanced pore accessibility and excellent electrocatalytic active site for the guest species, but also effectively improve the load capacity of chiral selector of L-Cys. Based on magnetic field-induced assembly, a novel magnetic electrochemical chiral sensor (MECS) was first constructed by MNPs for the discrimination and determination of tyrosine (Tyr) enantiomers. Under the optimized experimental condition, the oxidation peak current ratio of L-Tyr to D-Tyr ( I L / I D ) and the difference between the peak potential of the two enantiomers (Δ E p = E D – E L ) was observed to be 1.85 and 84 mV according to square wave voltammetry (SWV). With the synergic effect of the magnetic Fe 3 O 4 NPs and the chiral electrocatalytic activity of L-Cys functionalized AuNPs, a linear relationship between the peak current and the concentration of the two enantiomers was obtained over the range of 1–125 μM, with the limit of detection of 0.021 μM and 0.084 μM for L- and D-Tyr, respectively. The preferential chiral recognition for L-Tyr was further verified by circular dichroism spectroscopy. Furthermore, the sensitive MECS has been successfully used for the practical determination of L- or D-enantiomer in the Tyr mixture solutions by continuously increasing the concentration of one isomer, showing the consistent and reproducible results. [ABSTRACT FROM AUTHOR]

A magnetically controlled electrochemical sensing membrane for detection of insulin was fabricated by magnetic field directed self-assembly of electromagnetic molecularly imprinted polymers (EMMIPs). EMMIPs with excellent electrochemical performance and multiple recognition sites to insulin were synthesized by surface polymerization on the ternary Fe 3 O 4 @rGO/PANI nanoparticles (MGP NPs). The insulin-EMMIPs obtained by recognizing insulin from sample were assembled onto a magnetic glassy carbon electrode (MGCE) surface in order to form the magnetically controlled membrane under the magnetic field induction, and the membrane was peeled off from the electrode by removal of the magnet after electrochemical measurement. In this work, the biomimetic sensing membrane could be controlled more effectively and the electrode could be regenerated more conveniently. The novel magnetically controlled sensing membrane showed good selectivity and reproducibility for the determination of insulin with the detection limit reaching 17 pM (S/N = 3), and this limit of detection was further reduced to 3 pM by using the Fe(CN) 6 3−/4− redox probe. It has potential applications in the fields of clinical diagnosis with real-time detection capability, high efficiency, and easy operation properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new nanozyme Fe 3 O 4 @MoS 2 -Au NPs was designed and synthesized. • The dual-mode sensor based on Fe 3 O 4 @MoS 2 -Au NPs has multiple advantages. • Using the magnetic characteristics of nanozyme, real-time regulation of the catalytic reaction can be achieved. • 4. This research provides a new sensitive and accurate multi-channel analysis strategy for H 2 O 2 detection. Hydrogen peroxide (H 2 O 2) is closely related to many diseases and is often used as a target for disease diagnosis and treatment, so the research of H 2 O 2 detection method has attracted much attention. Compared with the current single-signal detection methods commonly used, dual-mode detection has inherent self-verification and self-correction functions and is expected to provide more reliable and anti-interference detection results. In this work, a novel nanocomposite Fe 3 O 4 @MoS 2 -Au NPs with strong peroxidase activity was constructed for the first time, and on this basis, a colorimetric/electrochemical dual-mode sensor was successfully prepared. Concretely, the Fe 3 O 4 @MoS 2 -Au NPs could catalyze reduction of H 2 O 2 to generate ·OH, leading to a significant electrochemical signal. At the same time, the color reaction of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) by ·OH can be used to build a colorimetric sensor. In colorimetric and electrochemical sensing systems, the linear range was 1–120 μM. The detection limit (LOD) can reach as low as 109 nM and 80 nM, respectively. In addition, the sensor has been favorably used for the detection of H 2 O 2 in normal human serum, and the recovery range was 87.55–113.13 %. In conclusion, this work provides an economical, sensitive and visualized H 2 O 2 detection platform, which has a wide application prospects. [ABSTRACT FROM AUTHOR]

In the present work, an advanced pretreatment method magnetic molecular imprinted polymers-dispersive solid phase extraction (MMIPs-DSPE) combined with the high sensitivity LTQ-Orbitrap mass spectrometry was applied to the complicated metabolites analysis of Traditional Chinese Medicines (TCMs) in complex matrices. The ginsenoside Rb 1 magnetic molecular imprinted polymers (Rb 1 -MMIPs) were successfully synthesized for specific recognition and selective enrichment of Panax notoginseng saponin metabolites in rat faeces. The polymers were prepared by using Fe 3 O 4 @SiO 2 as the supporting material, APTES as the functional monomer and TEOS as the cross-linker. The Rb 1 -MMIPs showed quick separation (10.8 emu/g), large adsorption capacity (636 μmol/g), high selectivity and fast binding kinetics (25 min). Dispersion solid-phase extraction using Rb 1 -MMIPs (Rb 1 -MMIPs-DSPE) integrated with LTQ-Orbitrap MS was applied to fish out and identify saponin metabolites from rat faeces, and totally 58 related compounds were detected within 20 min, including 26 PPD-group and 32 PPT-group notoginsenoside metabolites. Parallel tests showed that Rb 1 -MMIPs-DSPE obtained the lowest matrix effects of 0.98–14.84% and captured the largest number of structural analogues compared with traditional pretreatment methods organic solvent extraction (OSE) and solid phase extraction (SPE). [ABSTRACT FROM AUTHOR]

A novel magnetic molecularly imprinted sensing film (MMISF) was fabricated for the determination of estradiol (E2) based on magnetic glassy carbon electrode (MGCE) and magnetic molecularly imprinted polymers (MMIPs). The MMIPs were synthesized by in situ polymerization of glutathione (GSH)-functionalized gold (Au)-coated Fe 3 O 4 (Fe 3 O 4 @Au-GSH) nanocomposites and aniline. The MMISF was constructed with MMIPs via a kind of “soft modification” where MMIPs were assembled and immobilized on the surface of MGCE or removed from it by freely installing a magnet into MGCE or not. The E2-MMIPs were obtained by MMIPs recognizing E2 from sample, and the electrochemical detection was carried out after forming the “soft modification” sensing film by putting MGCE into the E2-MMIPs suspension liquid. Afterwards, the “soft modification” MMISF was peeled off from the electrode by removing the magnet from MGCE. The interface of the electrode could be quickly refreshed through simple treatment for the next detection. The structures and morphologies of Fe 3 O 4 @Au-GSH, MMIPs and MMISF were investigated by Fourier transform infrared spectrometer, ultraviolet and visible spectrophotometer, scanning electron microscope and atomic force microscope. In addition, the MMISF was successfully used for detecting E2 in milk powder with good sensitivity, selectivity, reproducibility and efficiency. The linear range of the MMISF for E2 was 0.025–10.0 μmol L −1 with the limit of detection of 2.76 nmol L −1 ( S / N = 3). [ABSTRACT FROM AUTHOR]

The molecularly imprinted magnetic stir bar coatings were created based on graft-functional Fe 3 O 4 nanoparticles with magnetic field-induced self-assembly. The magnetic complex including clonazepam as template, the graft-functional Fe 3 O 4 nanoparticles and methacrylic acid as monomers was pre-assembled through π–π interaction and hydrogen bonding, then was directionally adsorbed on the surface of magnetic stir bar under the magnetic induction. The molecularly imprinted coating with well-ordered structure was generated by one-step copolymerization based on the cross linking of ethylene glycol dimethacrylate. The molecularly imprinted coating with multiple recognition sites could be manufactured and applied in polar solvents, and showed superior selectivity and fast binding kinetics for benzodiazepines. The analytes in herbal health foods, treated by stir bar sorptive extraction, were determined by HPLC-UV. Good linearity was observed in the range of 0.01–2 μg mL −1 . The content of clonazepam in the herbal health foods was found to be 44 ng g −1 , and the average recoveries were 89.8–103.3% with a relative standard deviation (RSD) <6.5%, demonstrating the successful application in real sample analysis. [ABSTRACT FROM AUTHOR]

Several research have reported that silver ions (Ag + ) could enhance the photoluminescence of some kinds of gold nanoclusters (AuNCs), and redox reaction involved mechanisms were recognized as the main reason to cause such phenomenon. However, in this work, we found that Ag + could enhance the luminescence of aggregation-induced emission gold nanoclusters (AIE-AuNCs) without valence state change. Upon addition of Ag + , the luminescence of AIE-AuNCs enhanced instantly by 7.2 times with a red-shift of emission peak and a complete restoration of luminescence features was observed when Ag + was removed. A cost-effective, rapid-response, highly sensitive and selective method to detect trace amount of Ag + has thereby been established using AIE-AuNCs as a nanosensor. This analytical method exhibited a linear range of 0.5 nM–20 μM with a limit of detection of 0.2 nM and it showed great promise for Ag + monitoring in environmental water. [ABSTRACT FROM AUTHOR]

Based on magnetic field directed self-assembly (MDSA) of the ternary Fe 3 O 4 @PANI/rGO nanocomposites, a facile and controllable molecularly imprinted electrochemical sensor (MIES) was fabricated through a one-step approach for detection of glutathione (GSH). The ternary Fe 3 O 4 @PANI/rGO nanocomposites were obtained by chemical oxidative polymerization and intercalation of Fe 3 O 4 @PANI into the graphene oxide layers via π–π stacking interaction, followed by reduction of graphene oxide in the presence of hydrazine hydrate. In molecular imprinting process, the pre-polymers, including GSH as template molecule, Fe 3 O 4 @PANI/rGO nanocomposites as functional monomers and pyrrole as both cross-linker and co-monomer, was assembled through N–H hydrogen bonds and the electrostatic interaction, and then was rapidly oriented onto the surface of MGCE under the magnetic field induction. Subsequently, the electrochemical GSH sensor was formed by electropolymerization. In this work, the ternary Fe 3 O 4 @PANI/rGO nanocomposites could not only provide available functionalized sites in the matrix to form hydrogen bond and electrostatic interaction with GSH, but also afford a promoting network for electron transfer. Moreover, the biomimetic sensing membrane could be controlled more conveniently and effectively by adjusting the magnetic field strength. The as-prepared controllable sensor showed good stability and reproducibility for the determination of GSH with the detection limit reaching 3 nmol L −1 (S/N = 3). In addition, the highly sensitive and selective biomimetic sensor has been successfully used for the clinical determination of GSH in biological samples. [ABSTRACT FROM AUTHOR]

A facile adsorbent, a nanocomposite of Fe3O4 and reduced graphene oxide, was fabricated for the selective separation and enrichment of synthetic aromatic azo colorants by magnetic solid-phase dispersion extraction. The nanocomposite was synthesized in a one-step reduction reaction and characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller analysis. The colorants in beverages were quickly adsorbed onto the surface of the nanocomposite with strong π-π interactions between colorants and reduced graphene oxide, and separated with the assistance of an external magnetic field. Moreover, the four colorants in beverages were detected at different wavelengths by high performance liquid chromatography with diode array detection. A linear dependence of peak area was obtained over 0.05-10 μg/mL with the limits of detection of 10.02, 11.90, 10.41, 15.91 ng/mL for tartrazine, allure red, amaranth, and new coccine, respectively (signal to noise = 3). The recoveries for the spiked colorants were in the range of 88.95-95.89% with the relative standard deviation less than 2.66%. The results indicated that the nanocomposite of Fe3O4 and reduced graphene oxide could be used as an excellent selective adsorbent for aromatic compounds and has potential applications in sample pretreatment. [ABSTRACT FROM AUTHOR]

A molecularly imprinted stir bar was constructed based on Fe 3 O 4 @Polyaniline nanoparticles with magnetic field-induced self-assembly process. The monomer, methacrylic acid, was pre-assembled into the pre-polymers with vanillin as template by the formation of hydrogen bonds. After that, the magnetic complexes were generated by the hydrogen bonding, the hydrophobic and π–π interaction between the pre-polymers and Fe 3 O 4 @Polyaniline. The complexes were adsorbed on the surface of magnetic stir bar under the magnetic induction, and the coating of vanillin-molecularly imprinted polymers was generated by the one-step copolymerization basing on the cross linking of ethylene glycol dimethacrylate. The molecular imprinting stir bar showed superior selectivity and fast binding kinetics for vanillin, and was used for the enrichment of vanilla-flavor enhancers (vanillin, ethyl maltol and methyl vanillin) in infant milk powders. The results measured by HPLC-UV exhibited good linear ranges of 0.01–100, 0.02–100 and 0.03–100 μg mL −1 with the limit of detection of 2.5–10.0 ng mL −1 , and the recoveries were 94.7–98.9%, 82.1–96.7% and 84.5–93.2% with RSD < 7.2% for the three enhancers, respectively. [ABSTRACT FROM AUTHOR]

High plasma urate is closely related to gout, cardiovascular and other diseases. Therefore, monitoring the content of uric acid (UA) in plasma is of great significance for the treatment of gout and the prevention of other related diseases. Herein, a biosensor based on the biomimetic oxidase Fe 3 O 4 nanoparticles (NPs) @MnO 2 nanosheets (Fe 3 O 4 @MnO 2 NS) was constructed for colorimetric determination of UA. MnO 2 NS is an efficient biomimetic oxidase, and we found that the intrinsic oxidase activity of MnO 2 NS doped with Fe 3 O 4 NPs can be significantly enhanced. The chromogenic substrate TMB can be catalyzed by Fe 3 O 4 @MnO 2 NS to generate blue oxidized TMB, and UA can decompose the MnO 2 NS to inhibit the color reaction of TMB selectively, thereby realizing the quantitative detection of UA. In addition, the UA biosensor can perform colorimetric analysis of UA level through three methods: naked eye, smartphone and ultraviolet-visible (UV–vis) spectrophotometer. The linear ranges of UV–vis spectrophotometry and colorimetry with smartphone were 1–70 μM and 200–650 μM, respectively, and the limits of detection (LOD) were 0.27 μM and 21 μM. The analysis results of human plasma samples showed that the method had good selectivity and practicability. [Display omitted] • Fe 3 O 4 @MnO 2 NS showing significantly enhanced intrinsic oxidase activity. • Colorimetric analysis of UA level by naked eye, smartphone and microplate reader. • Fe 3 O 4 @MnO 2 NS combining the advantages of oxidase and magnetic properties. • The method completing the detection within 1 min at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: A novel electrochemical sensing platform based on magnetic field-induced self-assembly of Fe3O4@Polyaniline nanoparticles (Fe3O4@PANI NPs) has been for the first time fabricated for the sensitive detection of creatinine in biological fluids. The template molecule, creatinine, was self-assembled on the surface of Fe3O4@PANI NPs together with the functional monomer aniline by the formation of N–H hydrogen bonds. After pre-assembled, through the magnetic-induction of the magnetic glassy carbon electrode (MGCE), the ordered structure of molecularly imprinted polymers (MIPs) were established by the electropolymerization and assembled on the surface of MGCE with the help of magnetic fields by a simple one-step approach. The structural controllability of the MIPs film established by magnetic field-induced self-assembly was further studied. The stable and hydrophilic Fe3O4@PANI can not only provide available functionalized sites with which the template molecule creatinine can form hydrogen bond by the abundant amino groups in PANI matrix, but also afford a promoting pathway for electron transfer. The as-prepared molecularly imprinted electrochemical sensor (MIES) shows good stability and reproducibility for the determination of creatinine with the detection limit reached 0.35nmolL−1 (S/N=3). In addition, the highly sensitive and selective MIES has been successfully used for the clinical determination of creatinine in human plasma and urine samples. The average recoveries were 90.8–104.9% with RSD lower than 2.7%. [Copyright &y& Elsevier]

Abstract: Based on magnetic field directed self-assembly (MDSA) of Fe3O4@rGO composites, a novel magnetic molecularly imprinted electrochemical sensor (MIES) was fabricated and developed for the determination of the azo dye amaranth. Fe3O4@rGO composites were obtained by a one-step approach involving the initial intercalating of iron ions between the graphene oxide layers via the electrostatic interaction, followed by the reduction with hydrazine hydrate to deposit Fe3O4 nanoparticles onto the reduced oxide graphene nanosheets. In molecular imprinting, the complex including the function monomer of aniline, the template of amaranth and Fe3O4@rGO was pre-assembled through π–π stacking and hydrogen bonding interactions, and then was self-assembled on the surface of magnetic glassy carbon electrode (MGCE) with the help of magnetic field induction before electropolymerization. The structures and morphologies of Fe3O4@rGO and the doped molecularly imprinted polymers (MIPs) were investigated by Fourier transform infrared spectrometer (FT-IR), Raman spectra and scanning electron microscope (SEM). Besides, the characterization by differential pulse voltammetry (DPV) showed that Fe3O4@rGO composites promoted the electrical conductivity of the imprinted sensors when doped into the MIPs. The adsorption isotherms and adsorption kinetics were employed to evaluate the performances of MIES. The detection of amaranth was achieved via the redox probe K3[Fe(CN)6] by blocking the imprinted cavities, which avoided the interferences of oxidation products and analogs of amaranth. Furthermore, the prepared MIES exhibited good sensitivity, selectivity, reproducibility and efficiency for detecting amaranth in fruit drinks. The average recoveries were 93.15–100.81% with the RSD <3.0%. [Copyright &y& Elsevier]

Highlights: [•] The membrane of rGO/PANI was prepared for enhancing the sensitivity of sensor. [•] Functionalized AuNPs were proposed to fabricate the conductive AuNPs@MIPs. [•] The sensor could avoid the interferences caused by AA, DA, UA, and EP. [•] The sensor was used for sensitive and selective detection of 5-HT in real samples. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a highly sensitive and selective biomimetic electrochemical sensor for the amperometric detection of trace dopamine (DA) in human serums was achieved by gold nanoparticles (AuNPs) doped molecularly imprinted polymers (MIPs). Functionalized AuNPs (F-AuNPs), a novel functional monomer bearing aniline moieties on the surface of the AuNPs, were prepared via a direct synthesis method and then used to fabricate the conductive MIPs film on the modified electrode by electropolymerization method in the presence of DA and p-aminobenzenethiol (p-ATP). The obtained electrochemical sensor based on the conductive film of AuNPs doped MIPs (AuNPs@MIPs) could effectively minimize the interferences caused by ascorbic acid (AA) and uric acid (UA). The linear range for amperometric detection of DA was from 0.02μmolL−1 to 0.54μmolL−1 with the detection limit of 7.8nmolL−1 (S/N=3). Furthermore, the AuNPs@MIPs modified electrode (AuNPs@MIES) was successfully employed to detect trace DA in different human serums. [Copyright &y& Elsevier]

Highlights: [•] Pd3Pt1/PDDA-RGO nanomaterials were synthesized through a one-step in situ reduction process. [•] The nanomaterials showed excellent electrochemical behavior on oxidation of AA, DA and UA. [•] Simultaneous determination of the three analytes was performed by DPV with LOD of 0.61, 0.04 and 0.1μM for AA, DA and UA, respectively. [•] The sensor can be used for simultaneous detection of the three analytes in real samples. [ABSTRACT FROM AUTHOR]

• Construct a coumarin ratio fluorescence sensor with artificial nano enzymes firstly. • Fe 3 O 4 NPs used to conveniently control the catalytic reaction and purification system. • The method for analysis of complex samples with great selectivity and sensitivity. Herein, using Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) as a magnetic artificial peroxidase, an "on–off" ratiometric photoluminescence sensor with high-sensitivity and high-selectivity for coumarin was constructed based on photoinduced electron transfer (PET) between 7-hydroxycoumarin and rhodamine B (RB). The results showed that Fe 3 O 4 NPs catalyzed H 2 O 2 to generate nucleophilic group ·OH, which attacked the active site of coumarin and produced strong fluorescent 7-hydroxycoumarin molecules. Then, the fluorescence of RB was quenched with 7-hydroxycoumarin through the PET effect. The ratio signal generated in the above process was used for the quantitative detection of coumarin. Under optimized conditions, the linear range 0.5–25 mg/L was acquired for coumarin with the detection limit of 0.016 mg/L. This method had excellent selectivity and the recovery rate was 81.8%−106.8% with the relative standard deviation less than 5.6%, so it can be used for the quantitative analysis of coumarin in complex matrix samples. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a highly sensitive and selective biomimetic electrochemical sensor for Sildenafil in herbal sexual health products was prepared. Reduced graphene oxide (RGO), a novel highly conductive material was used to modify glassy carbon electrode (GCE) through layer-by-layer (LBL) self-assembly. The conductive molecularly imprinted films were constructed on the functional electrode surface using Sildenafil as template molecules, p-phenylenediamine (p-PD) as functional monomers. The obtained molecularly imprinted electrochemical sensor (MIES) was successfully used to detect Sildenafil in herbal sexual health products. The limit of detection (LOD) was 6.2nmolL−1. The recoveries for the spiked Sildenafil contents were in the range of 92.34–97.71% with the RSD<2.31%. The selective efficiencies for Sildenafil and other structurally related analogues only slightly varied from 0.93 to1.09. [Copyright &y& Elsevier]

In this paper, the novel surface molecularly imprinted polymers based on dendritic-grafting magnetic nanoparticles were developed to enrich and separate glibenclamide in health foods. The density functional theory method was used to give theoretical directions to the synthesis of molecularly imprinted polymers. The polymers were prepared by using magnetic nanoparticles as supporting materials, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The characteristics of magnetic nanoparticles and polymers were measured by transmission electron microscope and SEM, respectively. The enriching ability of molecularly imprinted polymers was measured by Freundlich Isotherm. The molecularly imprinted polymers were used as dispersive SPE materials to enrich, separate, and detect glibenclamide in health foods by HPLC. The average recoveries of glibenclamide in spiked health foods were 81.46-93.53% with the RSD < 4.07%. [ABSTRACT FROM AUTHOR]

A novel molecularly imprinted polymers ( MIPs) coated micro-stir bar ( MSB) for Glibenclamide ( GM) was developed. The MIPs, with GM as template molecular and methacrylic acid as functional monomer, were synthesized at the surface of the silylated MSB that was filled with magnetic core as substrate. Computational simulation was used for the optimal selection of functional monomers and porogen. The thickness of MIPs coating for MSB was about 10 μm, the adsorption and desorption time were about 40 and 20 min, respectively. The MIPs coated MSB possessed mechanical stability, high adsorption capacity, and good selectivity for GM. To achieve the optimum extraction performance, several parameters including extraction and desorption time, stirring rate, extraction and desorption solvent were investigated. A method for the determination of GM in herbal dietary supplements by MIPs coated MSB coupled with HPLC- UV was established. The results exhibited good linear ranges of 10-6250 μg L−1 with the low limit of detection of GM (3.05 μg L−1) and the good recoveries (81.9-101.4%). [ABSTRACT FROM AUTHOR]

Abstract: In order to resolve the low imprinting efficiency of surface molecularly imprinted polymers (MIPs), a dendritic-grafting method introducing more functional groups was proposed to modify the SiO2-coated magnetic nanoparticles (SiO2-coated MNPs). And then magnetic MIPs (MMIPs) were obtained using 17-ethyl estradiol (EE2) as a pseudo template with dendronized SiO2-coated MNPs as the supporter, aiming to avoid residual template leakage and to increase the imprinting efficiency. The resulting MMIPs showed high adsorption capacity, quick binding kinetics and good selectivity for trace estrogens. Meanwhile, MMIPs were used as magnetic dispersive solid-phase extraction (MDSPE) materials coupled with HPLC-UV for the detection of trace estrogens. The amounts of three estrogens which were detected from the plasma samples of pregnant women were 5.28, 5.31 and 4.17ngmL−1, and the average recoveries were 87.8%, 93.1% and 90.6% for the spiked samples with RSDs in the range of 1.4–6.3%, respectively. All these results reveal that MMIPs as MDSPE materials has good applicability to selective extraction and separation of trace estrogens from complex samples. [Copyright &y& Elsevier]

Abstract: A novel sandwich-type molecular imprinting electrochemical sensor (MIES) with enhanced sensitivity was prepared by using reduced graphene oxide (rGO) combined with platinum nanoparticles (PtNPs). Functional monomers were chosen with the aid of Gaussian 09 software. With the formation of Pt–S bond, 6-mercaptonicotinic acid (MNA) was fabricated at the surface of PtNPs/rGO composites modified glassy carbon electrode (GCE). 17β-estradiol (E2) was assembled by forming hydrogen bond with MNA. The polymer films were formed by electropolymerization of MNA and the specific recognition cavities were formed after the removal of templates. By using the differential pulse voltammetry (DPV), the resulting sensor exhibited good linear ranges of 0.004–0.060μM (I p (μA)=57.872C (μM)+1.6678, R =0.9977) and 0.060–50μM (I p (μA)=0.7915C (μM)+6.6906, R =0.9957). The limit of detection (LOD) of E2 was 0.002μM (S/N =3). Moreover, the MIES was successfully used in the analysis of E2 in makeups with good recoveries (>91.9%) with lower RSDs (<3.8%). The results revealed that the combination of molecular imprinting polymers (MIPs) with rGO/PtNPs composites could be applied to sensitive and selective determination of trace E2 in complex matrix. [Copyright &y& Elsevier]

Abstract: Graphene/gold nanoparticle multilayer films composed of polysodium 4-styrenesulfonate (PSS) functionalized reduced graphene oxide (RGO) and polyamidoamine (PAMAM) dendrimer stabilized gold nanoparticles (AuNPs) were built up using the electrostatic layer-by-layer (LBL) self-assembly technique on a glassy carbon electrode (GCE) modified with a first layer of poly(diallyldimethylammonium chloride) (PDDA). The film assembly, the electrochemical property as well as the electrocatalytic activity toward the oxidation of dopamine were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Electrochemical studies exhibit that the LBL assembled RGO/AuNPs films possess an excellent sensing performance for the detection of dopamine with a linear range from 1μM to 60μM and a limit of detection (LOD) as low as 0.02μM based on S/N =3. In addition, this electrochemical sensor was applied to the simultaneous detection of dopamine and uric acid by using DPV with high sensitivity and selectivity. The good analytical performance and long-term stability of the proposed sensor can be attributed to the combination of the reduced graphene oxide and gold nanoparticles in the LBL assembly films and the synergistic effect on the electrochemical oxidation of dopamine. [Copyright &y& Elsevier]

Abstract: In this paper, the molecularly imprinted polymer layer of estriol at the silica nanoparticles surface with selective recognition had been constructed. The methacryl groups of functional monomer at the silica nanoparticles surface were acted as reactive sites to induce imprinting polymerisation. The absorption capacity results showed that the molecularly imprinted polymers had an excellent combining affinity, recognition selectivity and fast kinetics. Furthermore, the molecularly imprinted polymers were successfully used as absorbent of dispersive solid-phase extraction coupled with high-performance liquid chromatography to determinate trace estriol and estradiol in milk tablets. The high recoveries yielded of 89.1–93.5% were achieved with the relative standard deviations less than 9.4%. So, the molecularly imprinted polymers are the effective absorbents for the separation and enrichment of oestrogens in the complex matrices samples. [Copyright &y& Elsevier]

Abstract: In this paper, an electrochemical sensor for 17β-estradiol (E2) based on the molecular imprinting polymer (MIP) membranes had been constructed. 6-mercaptonicotinic acid (MNA) and E2 were first assembled on the surface of platinum nanoparticles-modified glassy carbon electrode (PtNPs/GCE) by the formation of Pt–S bonds and hydrogen-bonding interactions, and subsequently the polymer membranes were formed by electropolymerization. Finally, a novel molecularly imprinted sensor (MIS) was obtained after removal of E2. Experimental parameters such as deposition time, scan cycles, pH value and accumulation condition were optimized. Under optimal conditions, the MIS exhibited a large adsorption capacity and high selectivity. A good linearity was obtained in the range of 3.0×10−8–5.0×10−5 molL−1 (r =0.996) with an estimated detection limit of 1.6×10−8 molL−1. MIS had been successfully used to analyze E2 in water samples without complex pretreatment. Meanwhile, the average recoveries were higher than 93.9% with RSD<3.7%. All results above reveal that MIS is an effective electrochemical technique to determine E2 real-time in complicated matrix. [Copyright &y& Elsevier]

Abstract: This paper reports a surface molecular self-assembly strategy for molecular imprinting on magnetic nanoparticles for selective separation and detection of estrogens in feeds. First, γ-methacryloxypropyltrimethoxysilane (MEMO) was successfully assembled at the surface magnetic nanoparticles through simple free radical polymerization, and subsequently, the copolymerization was further assembled between methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of templates 17β-estradiol (E2). The synthesized magnetic molecularly imprinted polymers for E2 (E2-MMIPs) showed quick separation, large adsorption capacity, high selectivity and fast binding kinetics for E2. Meanwhile, a dispersive solid-phase extraction (DSPE) based on E2-MMIPs has been established for efficient separation and fast enrichment of estrogens from the feeds. The assay exhibited a linear range of 0.1–4μM for E2 and estriol (E3) with the correlation coefficient above 0.9996 and 0.9994, respectively. Recoveries of E2 from three kinds of feeds spiked at different concentration levels ranged from 92.7% to 97.0% with RSD<4.7%, and recoveries of E3 ranged from 71.9% to 83.1% with RSD<4.9%, respectively. The method is simple and sensitive, and can be used as an alternative tool to effectively separate and enrich the trace of estrogens in agricultural products by HPLC–UV. [Copyright &y& Elsevier]

Abstract: An analytical procedure for selective extraction of sildenafil and vardenafil in herbal dietary supplements (HDSs) has been set up by using the magnetic molecularly imprinted polymers (MMIPs) as the extraction and clean-up materials, followed by high performance liquid chromatography-ultraviolet (HPLC-UV). The MMIPs were prepared by a surface molecular imprinting technique, using Fe3O4 magnetite as a magnetically susceptible component, sildenafil as template molecule, 2-(trifluoromethyl) acrylic acid (TFMAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as polymeric matrix components. The MMIPs were characterized by transmission electron microscope (TEM), Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. The heterogeneity of the MMIPs was modeled with the Freundlich isotherm equation. The resulting MMIPs had high recognition ability and fast binding kinetics for sildenafil. The MMIPs were used as dispersive solid-phase extraction (DSPE) materials to selectively extract sildenafil and vardenafil from HDSs, the contents of sildenafil and vardenafil were found to be 8.05 and 3.86μgg−1, respectively, and the average recoveries in spiked HDSs were 70.91–91.75% with a relative standard deviation (R.S.D.) below 7%. The MMIPs were successfully used to selectively enrich and determine sildenafil and vardenafil from HDSs. [Copyright &y& Elsevier]

Abstract: To assess the potential risks associated with the environmental exposure of steroid estrogens, a novel highly efficient and selective estrogen enrichment procedure based on the use of molecularly imprinted polymer has been developed and evaluated. Herein, analogue of estrogens, namely 17-ethyl estradiol (EE2) was used as the pseudo template, to avoid the leakage of a trace amount of the target analytes. The resulting pseudo molecularly imprinted polymers (PMIPs) showed large sorption capacity, high recognition ability and fast binding kinetics for estrogens. Moreover, using these imprinted particles as dispersive solid-phase extraction (DSPE) materials, the amounts of three estrogens (E1, E2 and E3) which were detected by HPLC–UV from the chicken tissue samples were 0.28, 0.31 and 0.17μgg−1, and the recoveries were 72.5–78.7%, 90.3–95.2% and 80.5–83.6% in spiked chicken tissue samples with RSD <7%, respectively. All these results reveal that EE2-PMIPs as DSPE materials coupled with HPLC–UV could be applied to the highly selective separation and sensitive determination of trace estrogens in chicken tissue samples. [Copyright &y& Elsevier]

Abstract: In this paper, highly selective core–shell molecularly imprinted polymers of 17β-estradiol on the surface of silica nanoparticles (SiO2@E2-MIPs) were prepared. The SiO2@E2-MIPs were characterized by Fourier transform infrared spectrometer (FT-IR), transmission electron microscope (TEM), dynamic adsorption and static adsorption tests. The sorption capacity of the SiO2@E2-MIPs were nearly 5 times that of the non-imprinted polymers (NIPs), and it only took 25min to achieve the sorption equilibrium. It indicated that the SiO2@E2-MIPs exhibited a high selectivity, large adsorption capacity and fast kinetics. When the SiO2@E2-MIPs were used as dispersive solid-phase extraction (dSPE) absorbents to selectively enrich and determine estrogens in duck feed, the average recoveries of E2 and estriol (E3) were higher than 96.74% and 72.07%, respectively, and the relative standard deviations (RSD) of E2 and E3 were less than 1.61% and 3.28%, respectively. The study provides an effective method for the separation and enrichment of estrogens in the complex matrix samples by the SiO2@E2-MIPs. [ABSTRACT FROM AUTHOR]

• A novel magnetic ternary nanocomposite hemin-Fe 3 O 4 @polypyrrole with stronger peroxidase-like activity was synthesized. • The residual catalytic effect can be removed and the real-time regulation of the catalytic reaction can be realized. • Its excellent stability and reusable characteristics can increase the practicality of this colorimetric sensors. • The analysis of actual samples showed that GSH/GSSG was more significant in clinical diagnosis. At present, artificial mimic enzyme has become a powerful substitute for natural enzyme. In particular, the biosensors based on nano-enzymes have been the focus of current research. Herein, a novel magnetic ternary nanocomposite hemin-Fe 3 O 4 @polypyrrole (h-Fe 3 O 4 @ppy) was synthesized by chemical oxidation polymerization. The results showed that the h-Fe 3 O 4 @ppy had stronger peroxidase activity than Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) and h-ppy NPs, and was indicated by Michaelis-Menten constant (K m) and maximum initial velocity (V max). Therefore, we used h-Fe 3 O 4 @ppy catalyzing H 2 O 2 to oxidize the chromogenic substrate TMB, and built Hydrogen peroxide (H 2 O 2) and Glutathione (GSH) colorimetric biosensors with the help of signal intrinsic exponential amplification and easy operation. The controllable catalysis was realized by h-Fe 3 O 4 @ppy which was prone to separation. The method of removing h-Fe 3 O 4 @ppy by magnetic separation effectively eliminated the effect of residual catalysis when terminating the reaction. The sensor was then applied to the determination of GSH in biological samples from acute coronary syndrome patients. The linear ranges of H 2 O 2 and GSH were 0.2–100 μM and 0.5–80 μM, respectively. The detection limits of H 2 O 2 and GSH are 0.18 μM and 0.15 μM, respectively. This research not only proposes a new type of nanoenzyme, but also shows the multiple advantages of magnetic nano-enzymes for the construction of biosensors. [ABSTRACT FROM AUTHOR]