Bimetallic Nanozyme: A Credible Tag for In Situ-Catalyzed Reporter Deposition in the Lateral Flow Immunoassay for Ultrasensitive Cancer Diagnosis.

The lateral flow immunoassay (LFIA) is a sought-after point-of-care testing platform, yet the insufficient sensitivity of the LFIA limits its application in the detection of tumor biomarkers. Here, a colorimetric signal amplification method, bimetallic nanozyme-mediated in situ-catalyzed reporter deposition (BN-ISCRD), was designed for ultrasensitive cancer diagnosis. The bimetallic nanozyme used, palladium@iridium core-shell nanoparticles (Pd@Ir NPs), had ultrahigh enzyme-like activity, which was further explained by the electron transfer of Pd@Ir NPs and the change in the Gibbs free energy during catalysis through density functional theory calculations. With gastric cancer biomarkers pepsinogen I and pepsinogen II as model targets, this assay could achieve a cutoff value of 10 pg/mL, which was 200-fold lower than that without signal enhancement. The assay was applied to correctly identify 8 positive and 28 negative clinical samples. Overall, this BN-ISCRD-based LFIA showed great merits and potential in the application of ultrasensitive disease diagnosis.

Electrochemiluminescent bioassay based on Ru@Zr-BTC-MOFs nanoparticles for determination of let-7a miRNA using the hybridization chain reaction.

Carboxyl-rich tris(4,4'-dicarboxylic acid-2,2'-bipyridyl) ruthenium(II) ([Ru(dcbpy)3]2+) and 1,3,5-phenyl tricarboxylic acid (H3BTC) were used as the organic ligand to synthesize the metal-organic frameworks by a simple one-pot hydrothermal method with ZrCl4 as metal ion source. Subsequently, the excellent electrochemiluminescence (ECL) luminophore (denoted as Ru@Zr-BTC-MOFs) was obtained. The Ru@Zr-BTC-MOFs displayed outstanding ECL properties, and a sensitive ECL bioassay based on Ru@Zr-BTC-MOFs was designed for the detection of let-7a microRNA (miRNA) using hybrid chain reaction (HCR). Under the optimal experimental conditions, the proposed bioassay exhibited a good linear relationship in the range from 50.0 fM to 5.00 × 102 pM with a detection limit of 3.71 fM. Besides, the proposed sensor exhibited satisfactory performance in real samples. The recovery was 91 ~ 108%, and the relative standard deviation was less than 5.6%. It might have potential clinical applications for detecting miRNA in biomedical research and clinical diagnosis. The schematic diagram of the preparation of Ru@Zr-BTC-MOFs (a) and ECL sensor for detecting let -7a (b).

Microneedle-enabled therapeutics delivery and biosensing in clinical trials.

Microneedles (MNs) are micron-sized protrusions attached to a range of devices that are used in therapeutic delivery and diagnosis. Because MNs can be self-applied, are painless, and can carry multiple therapeutic agents, they have received extensive attention, and have been widely investigated, for local and systemic therapy. Many researchers are currently working to extend the use of MNs to clinical applications. In this review, we provide an update and analysis on MN-based clinical trials since their inception in 2007. The MNs in clinical trials are classified into five types based on their appearance and properties, including: hollow MNs, MN patches, radiofrequency MNs, MN rollers, and other MNs. The various aspects of MN trials are summarized, such as MN types, clinical trial time, and trial regions. This review aims to present an overview of MN development and provide insights for future research in this field. To our knowledge, this is the first review focused on MN clinical trials which showcases the latest applications of this advanced technology in medicine.

Visual and Electrochemical Detection of let-7a: A Tumor Suppressor and Biomarker.

Let-7a, a type of low-expressed microRNAs in cancer cells, has been investigated as a promising biomarker and therapeutic target for tumor suppression. Developing simple and sensitive detection methods for let-7a is important for cancer diagnosis and treatment. In this work, the hybridization chain reaction (HCR) was initiated by let-7a via two hairpin primers (H1 and H2). After the HCR, the remaining hairpin H1 was further detected by lateral flow assay (LFA) and electrochemical impedance spectroscopy. For LFA, biotin-modified H1(bio-H1) and free H2 were used for HCR. With the decrease of let-7a concentration, the color of T line gradually increased. As for electrochemical methods, the H1'-AuNP-modified electrode was used for detection of bio-H1 based on the difference of impedance (ΔRct) detected without and with different concentrations of let-7a participating in the HCR. This method could detect let-7a in the range of 10.0 fM and 1.0 nM with detection limits of 4.2 fM.

A novel sandwich impedimetric immunosensor for detection of apolipoprotein-A1 based on the gold nanoparticle-hybridized mercapto-ß-cyclodextrin-Pb(II) metal-organic framework.

A novel sandwich electrochemical impedimetric immunosensor was proposed to detect apolipoprotein-A1 (Apo-A1), a common biomarker for bladder cancer. The molybdenum disulfide/graphene quantum dot (MoS2/GQD) nanocomposites were modified on the surface of a glassy carbon electrode (GCE) and used to immobilize the biotinylated antibody (Ab1) with the help of chitosan and glutaraldehyde (denoted as BSA/Ab1/CHIT/MoS2/GQD/GCE). Pb(II)-thiol-ß-cyclodextrin metal-organic framework (denoted as Pb-MOF) was synthesized with lead metal ions and thiol-ß-cyclodextrin ligands by a one-pot solvothermal method, and then, gold nanoparticles were modified on the surface of Pb-MOF (Pb-MOF-AuNPs) by Au-S bond, which was used as signal label for the recombinant antibody (Ab2). When the immunosensor of BSA/Ab1/CHIT/MoS2/GQD/GCE reacted with Apo-A1, Pb-MOF-AuNPs-Ab2/BSA was connected to the electrode when immunoreaction occurred, and an immune sandwich structure was formed, which led to significantly increased charge transfer resistance of electrochemical probe for ferrocyanide (II)/(III) within the frequency range 10-1 ~ 105 Hz at 5 mV amplitude and the potential of 0.180 V (vs. SCE). Based on this principle, the quantitative detection of Apo-A1 was established. The relative change of electrochemical resistance and the logarithmic value of Apo-A1 concentration showed a linear relationship with a linear coefficient of 0.9989 in the range 1.00 pg mL-1 and 1.00 µg mL-1 with the limit of detection of 0.30 pg mL-1. The selectivity, repeatability, and other performance of the proposed immunosensor were also investigated. The immunosensor was successfully applied to the detection of real serum and urine samples with recovery in the range 96.4 ~ 109.1% (RSD < 3.8%), indicating that it could be helpful for the clinical diagnosis of bladder cancer.

[Rapid screening of 14 antibacterial drugs in anti-acne cosmetics using ion mobility spectrometry coupled with solid-phase extraction].

The main methods currently used to detect illegally added chemicals in cosmetics include thin-layer chromatography, high performance liquid chromatography (HPLC), gas chromatography (GC), and liquid chromatography-mass spectrometry (LC-MS). Compared with other analytical techniques, these methods have the advantages of high sensitivity, specificity, and accuracy, all of which are required in practical detection work. However, they also present a number of limitations, such as long analysis times and requirements for skilled operators and strictly controlled laboratory environments. Supervision, a growing trend in market surveillance, requires rapid and effective methods to screen illegally added chemicals. The suspected samples are sealed for some time and then sent to the laboratory for further testing. Ion mobility spectrometry (IMS) is a new type of trace gas separation technology that was developed in recent years. The principle behind IMS is the separation and characterization of chemical species based on differences in the migration speed of their gas-phase ions under an electric field. As this technology has the advantages of miniaturization, easy operation, and quick responses, it is widely used in food and drug quality testing, as well as other related fields. However, it is rarely used in cosmetic detection, likely because the cosmetics matrix is highly complex, which can interfere with ion determination. Thus, optimizing the pretreatment process of cosmetics for IMS is important. In this work, solid-phase extraction (SPE) is combined with IMS to establish a method for the rapid screening of 14 antibacterial drugs in anti-acne cosmetics. The IMS detection parameters, sample extraction conditions, and SPE clean-up conditions (SPE column, type of leachate, type and volume of eluent) were studied and optimized in detail. The sample was extracted with 80%(v/v) acetonitrile aqueous solution (containing 0.2% (mass fraction) trichloroacetic acid), loaded onto an activated Oasis® MCX SPE column, leached with 3.0 mL of methanol, and eluted with 1.0 mL of 2% ammonia methanol solution. The eluate was then directly injected into the IMS instrument. The IMS parameters were as follows: positive ion source voltage=2200 V, transfer tube voltage=8000 V, inlet temperature=180 ℃, transfer tube temperature=180 ℃, ion gate voltage=50 V, gate voltage pulse width=85 µs, and migration gas flow rate=1.2 L/min. The migration times for the 14 antibacterial drugs ranged from 11 to 17 ms, and the detection limits for the target compounds ranged from 0.2 to 1.2 µg/g. Owing to the narrow linear range of IMS, a quantitative method employing HPLC was also established to optimize the SPE pretreatment step and verify the positive samples. Chromatographic separation was conducted on a Phenomenex Luna C18 column (250 mm×4.6 mm, 5 µm), with a column flow rate of 1.0 mL/min and gradient elution with mobile phases A (0.01 mol/L potassium dihydrogen phosphate adjusted to pH 4.0 with phosphoric acid) and B (acetonitrile). The column temperature was set to 35 ℃, and the injection volume was fixed at 5 µL. A total of 25 cosmetics samples were screened, and one positive sample was found to be consistent with the results of HPLC. The proposed method is fast, simple, and efficient, and it can be used for the rapid screening of the 14 antibacterial drugs in anti-acne cosmetics. Pretreatment can significantly reduce the influence of the cosmetic matrices on the determination results, improve instrument sensitivity, and effectively decrease the occurrence rate of false positives and negatives. The technique developed in this work can improve the efficiency of screening for illegally added chemicals and expand the applications of IMS for detecting various chemicals in complex matrices, such as cosmetics.

Assessment of polybrominated diphenyl ethers and emerging brominated flame retardants in Pheretima (a Traditional Chinese Medicine): Occurrence, residue profiles, and potential health risks.

China produces and consumes large quantities of brominated flame retardants (BFRs) as well as several other unregulated electronic waste recycling activities, causing high BFR concentrations in the natural environment. Thus, Traditional Chinese Medicines (TCMs) may be contaminated by legacy BFRs (e.g. polybrominated diphenyl ethers (PBDEs)) and emerging BFRs (eBFRs, such as decabromodiphenyl ethane (DBDPE)) during growth, processing, packaging, and transportation. Pheretima, which is a typical animal drug recorded in Chinese Pharmacopoeia, was used as an example to evaluate human exposure to BFRs through TCM intake. This study is the first to determine 25 PBDEs and 5 eBFRs in Pheretima and estimate the daily BFR intake via Pheretima-containing TCMs. Twenty-seven Shanghai Pheretima and fifty-one Guang Pheretima samples were collected between March and June 2019 in southeast China. High BFR detection frequencies were found in Pheretima, of which BDE-209 and DBDPE were the most predominant analytes. The total PBDE contents ranged from 73 pg/g to 8,725 pg/g, while that of the eBFRs varied between 115 pg/g and 2,824 pg/g. The profiles and abundances were found to be species- and origin-dependent. However, the traditional processing of Pheretima may reduce BFR residues. Based on the usual clinical doses of Pheretima and the available chronic oral reference doses of BDE-47, 99, 153, and 209, the mean (95th percentile) of the total hazard quotient was estimated to be 9.1 × 10-5 (2.7 × 10-4). Therefore, there is little risk related to BFR exposure for patients taking formulated Pheretima-containing TCMs. However, it is necessary to establish routine monitoring programs for the co-existence of pollutants in TCMs to perform a systematic and comprehensive risk assessment.

Combinatory antitumor therapy by cascade targeting of a single drug.

Combination therapy has shown its promise in the clinic for enhancing the efficacy of tumor treatment. However, the dose control of multiple drugs and their non-overlapping toxicity from different drugs are still great challenge. In this work, a single model drug, paclitaxel (PTX), is used to realize combination therapy and solve the problems mentioned above. Either PTX or its triphenylphosphine derivative (TPTX) is encapsulated in galactose-modified liposomes (GLips) to obtain GLips-P or GLips-TP, which are simply mixed in different ratios to finely control the proportion of PTX and TPTX. These mixed liposomes, GLips-P/TP, feature a cascade target delivery of PTX, from tissue to cell, and then to organelle. PTX plays a primary role to cause the cytotoxicity by microtubule bindings in cytoplasm, while TPTX is proved to increase the intracellular levels of caspase-3 and caspase-9 that cause apoptosis via a mitochondria-mediated pathway. Notably, GLips-P/TP 3:1 exhibited the significant drug synergy in both cytotoxicity assay of HepG2 cells and the treatment efficacy in Heps xenograft ICR mouse models. This work not only demonstrates the great promise of a cascade targeting delivery for precise tumor treatment, but also offers a novel platform to design combinatory therapy systems using a single drug.

An impedimetric immunosensor for determination of porcine epidemic diarrhea virus based on the nanocomposite consisting of molybdenum disulfide/reduced graphene oxide decorated with gold nanoparticles.

An electrochemical immunosensor for the determination of porcine epidemic diarrhea virus (PEDV) is described. It was manufactured by using gold nanoparticles/molybdenum disulfide/reduced graphene oxide nanocomposites modified on the surface of a glassy carbon electrode (GCE). The independently developed monoclonal antibody of PEDV-2C11 was immobilized on the modified electrode at site of gold nanoparticles provided in the nanocomposites. The concentration of PEDV was quantified by measuring the changes in the charge transfer resistance of the electrode before and after the immunoreaction between antigen-antibody by using hexacyanoferrate(II)/(III) as the redox probe. The frequency range was 10-1 to 105 Hz at the amplitude of 10 mV and an applied potential of + 0.180 V. Based on the immunoreaction between PEDV antigen and PEDV-2C11 antibody in 0.1 M phosphate buffer containing 0.1 M KCl at 37.5 °C for 140 min, the relative change in impedance was proportional to the logarithmic value of PEDV concentrations in the range of 82.5 to 1.65 × 104 TCID50 mL-1. Good reproducibility, stability, and specificity of the proposed immunosensor were obtained. It was successfully applied to the determination of PEDV in the spiked sample. Graphical abstractSchematic representation. a The preparation of AuNP/MoS2/rGO composites. b Representation of modification and functioning of the label-free electrochemical immunosensor and the electrochemical impedimetric response obtained before (a) and after (b) incubation of PEDV.

[Rapid untargeted screening and determination of unknown contaminants in aquatic products by high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry].

A method has been developed for rapid untargeted screening and determination of unknown contaminants in aquatic products by high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry. The samples were extracted by acetonitrile, dried under nitrogen, dissolved in methanol-water (3:7, v/v), and analyzed via the full MS scan/data dependent MS2 mode during the screening process. The Trace Finder software was used to match the precise mass, the isotope abundance ratio, the fragment ion to search for unknown contaminants in aquatic samples. The optimized QuEChERS method is used to purify the samples when quantifying. The quantitative analyses of triazole, caffeine, and ethoxyquinoline were performed via the target-MS2 mode. The correlation coefficients of the three compounds in fish and shrimp samples were higher than 0.99 in the linear range of 5-1000 µg/L. The limit of detection was 1 µg/kg, and the limit of quantitation was 5 µg/kg. The average recoveries were between 70.5% and 90.9% with the relative standard deviations ranging from 5.4% to 12.8%. The screening method has the advantages of fast, accurate, and high throughput; when combined with the quantitative method, it can be used to screen and determine unknown contaminants in the actual aquatic products.

[Determination of 10 perfluorinated carboxylic acid compounds in water by gas chromatography-mass spectrometry coupled with negative chemical ionization].

A method was developed for the simultaneous determination of 10 perfluorinated carboxylic acid compounds in water by gas chromatography-mass spectrometry coupled with negative chemical ionization (GC-NCI-MS). Perfluorinated carboxylic acid compounds were derivatized by trifluoro-N-methyl-N-(trimethylsilyl) acetamide (MSTFA) as the trimethylsilyl derivatization reagent. The water sample was purified and enriched through a weak anion exchange solid phase extraction column and analyzed via GC-NCI-MS. The sample pretreatment, derivation and instrument conditions were optimized. The results showed that the linearity of the 10 perfluorinated carboxylic acid compounds was good in the range of 0.1-10 mg/L with correlation coefficients of 0.9956-0.9993. The limits of detection (LODs) and limits of quantification (LOQs) were 0.5-1.5 µg/L and 1.5-4.5 µg/L, respectively. The spiked recoveries of the blank samples ranged from 70.2% to 112.6% with the relative standard deviations (RSDs) between 2.1% and 14.5% (n=6). The method is simple, sensitive, accurate and precise, and can be used to detect the 10 perfluorinated carboxylic acid compounds in water.

Metabolic profile elucidation of Zhi-Zi-Da-Huang decoction in rat intestinal bacteria using high-resolution mass spectrometry combined with multiple analytical perspectives.

1. Zhi-Zi-Da-Huang decoction (ZZDHD) has been widely used for the treatment of alcoholic jaundice, alcoholic liver disease, and acute hepatitis in China for thousands of years. Conventionally decoctions are administered orally, after which the metabolism caused by the enzymes in intestinal bacteria may influence significantly on the curative effects or toxicity. 2. In this work, the comprehensive metabolic process of ZZDHD in intestinal bacteria was investigated reliably using high-resolution HPLC-DAD-ESI-TOF/MS. Besides, a novel strategy for major-to-trace metabolites identification which integrated information derived from diagnostic fragment ions, mass spectral similarity filter strategy, dynamic metabolic change of target compounds and relevant behavior in LC-MS was adopted. 3. As a result, 45 compounds, including 26 bio-converted prototypes and 19 newly generated metabolites were detected and tentatively identified. The metabolic profile of ZZDHD in gastro-intestinal was subsequently elucidated. Deglycosylation, oxidation, reduction, acetylation, and ring cleavage were all observed in the biotransformation of the decoction. Among the rest, deglycosylation was found to be the predominant metabolic pathway. 4. The results obtained herein provided a practical strategy for metabolic profile elucidation of traditional herbal medicines. Moreover, it would be helpful to unravel how the oral decoctions play the therapeutic role in vivo.

Deciphering the absorption profile and interaction of multi-components of Zhi-Zi-Da-Huang decoction based on in vitro-in silico-in vivo integrated strategy.

Zhi-Zi-Da-Huang decoction (ZZDHD) has been acknowledged with striking therapeutic effects for hepatobiliary disorders in the history of China. As decoctions are usually administrated orally, intestinal absorption, the prerequisite task of exerting therapeutic effects, is of utmost significance for screening potential active compounds and understanding the mechanism of drug action. In this work, an in vitro-in silico-in vivo strategy based on HPLC-DAD-ESI-TOF/MS was adopted for precisely profiling the intestinal absorption of ZZDHD, which integrated information obtained from rat everted gut sac model, octanol-water partition model, in silico prediction and in vivo experimental data. Besides, 34 main absorbed ingredients were selected as chemical markers to investigate the compatible interaction of the decoction on absorption level using rat everted gut sac experiment. In total, 106 compounds of ZZDHD were speculated as potential absorptive. Among them, 90 constituents predicted absorbable in at least two experimental models were finally recognized as intestinal absorbable ingredients. In addition, the absorption level of iridoids, terpenoids and flavonoid glycosides were found improved and the absorption of catechins and anthraquinones were inhibited after prescription compatibility. Taken together, this study presents a reliable strategy for evaluating intestinal absorption of herbal medicines and offers a reference for the rationality of herbal compatibility and the modernization of traditional Chinese medicine (TCM).

Mitochondria: promising organelle targets for cancer diagnosis and treatment.

Mitochondria, the energy supply factories for cell-life activities, play important roles in controlling epigenetics, differentiation and initiation, and the execution of apoptosis. These functions of the mitochondria contribute to cell adaptation to challenging microenvironment conditions. In past decades, mitochondrial malfunction has been revealed to be closely related to the occurrence and development of a variety of human disorders, including cancer and multiple neurodegenerative diseases. The disturbance of the mitochondrial genome (mtDNA) or mitochondrial vital functions, e.g., the production of adenosine triphosphate (ATP) and the generation of reactive oxygen species (ROS), can potentially be involved in disease pathogenesis. Recent research has shown that the precise monitoring of mitochondrial environments can provide potential directions for cancer diagnosis. Furthermore, mitochondrial-targeted cancer treatment exhibits unparalleled superiority for enhanced tumor therapy. Therefore, in this review, we focus on mitochondrial-based cancer diagnosis via monitoring mitochondrial respiration or mitophagy. Current approaches using mitochondrial-based cancer treatments, including targeting mitochondrial ATP, mitochondrial membrane permeability, and mitochondrial ROS levels and mtDNA, are also summarized. This review will provide insights into mitochondrial-mediated tumor monitoring and mitochondrial-based therapy.

[Determination of characteristic compound in manuka honey by automatic on-line solid phase extraction-liquid chromatography-high resolution mass spectrometry].

A method for the determination of characteristic compound 3,5-dimethoxybenzoate-4-diglucoside (leptosperin) in manuka honey was developed by automatic on-line solid phase extraction-liquid chromatography-high resolution mass spectrometry (SPE-LC-HRMS). The samples were separated on a Dikma Diamonsil Plus C18 column (150 mm×4.6 mm, 5 µm) using the mobile phases of 0.1% (v/v) formic acid aqueous solution and acetonitrile with gradient elution. The compound was detected with negative electrospray ionization (ESI-) in Target-MS2 mode. The results showed that the linear range was 0.5-100.0 mg/L, the correlation coefficient was 0.9993. The limit of detection (LOD, S/N ≥ 3) and limit of quantification (LOQ, S/N ≥ 10) of the method was 3 mg/kg and 10 mg/kg, respectively. The recoveries at the spiked levels of 50.0, 100.0, 200.0 mg/kg (10.0, 20.0, 50.0 mg/kg in black locust samples) were in the range of 82.0%-95.2% with the relative standard deviations ranging from 2.7% to 9.7% (n=6). The proposed method was applied to 95 mature honey samples from hives in New Zealand including 12 different kinds and 50 commercial honey samples from four different countries. The method is fast, sensitive and accurate to provide technical support to solve the judgment of the manuka honey imported from New Zealand.

Comparative pharmacokinetics and brain distribution of magnolol and honokiol after oral administration of Magnolia officinalis cortex extract and its compatibility with other herbal medicines in Zhi-Zi-Hou-Po Decoction to rats.

Zhi-Zi-Hou-Po decoction (ZZHPD) is one of the famous antidepressant Chinese formulas and is composed of Magnolia officinalis cortex (HP), Gardenia jasminoides Ellis (ZZ) and Citrus aurantium L. (ZS). Magnolol (MN) and honokiol (HN) from HP are the major active ingredients responsible for the therapeutic effects of ZZHPD. The aim of this study is to compare the pharmacokinetics and rat brain distribution of MN and HN after oral administration of HP extract and its compatibility with other herbal medicines in ZZHPD by HPLC-FLD. Compared with the HP group, Tmax (time to reach peak drug concentration in plasma) and AUC(0-τ) significantly increased in the ZZHPD and HP-ZZ groups. There was little change in the HP-ZS group in comparison with the HP group, which indicated that ZZ promotes absorption extent and defers the absorption rate of MN. The different compatibility of ZZHPD had a different degree of impact on the concentration of MN and HN in brain. The concentration of MN significantly increased in the HP-ZZ group while it decreased in the HP-ZS group compared with the HP group, which explained the concentration of compounds being slightly greater in the ZZHPD group than in the HP group. HP mixed with other medicines resulted in a decrease in HN concentration in the brain, particularly HP compatible with ZS. The results could be helpful for revealing the compatibility mechanism and providing clinical medication guidance for ZZHPD.

Development of an impedimetric immunosensor for the determination of 3-amino-2-oxazolidone residue in food samples.

The use of furazolidone in food animals has been banned in European Union (EU) because of its carcinogenicity and mutagenicity on human health, but its continued misuse is widespread. Therefore, there is an urgent need for a simple, reliable, and rapid method for the detection of its marker residue, 3-amino-2-oxazolidinone (AOZ), in food products. In this regard, a sensitive and reliable electrochemical method was presented to detect AOZ based on a novel label-free electrochemical impedimetric immunosensor to address this need. The immobilization of monoclonal antibody against AOZ (denoted as AOZ-McAb) on the gold electrode was carried out through a stable acyl amino ester intermediate generated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydrosuccinimide (NHS), which could condense antibodies on the self-assembled monolayer (SAM). The detection of AOZ was performed by measuring the relative change in charge transfer resistance before and after AOZ and AOZ-McAb immunoreaction by electrochemical impedance spectroscopy (EIS). Under the optimized conditions, the relative change in charge transfer resistance was proportional to the logarithmic value of AOZ concentrations in the range of 20.0 to 1.0×10(4) ng mL(-1) (r=0.9987). Moreover, the proposed immunosensor has a high selectivity to AOZ alone with no significant response to the metabolites of other nitrofuran antibiotics, such as 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), semicarbazide (SEM), and 1-aminohydantoin hydrochloride (AHD). This protocol has been applied to detect AOZ in food samples with satisfactory results.

Novel reagents for quantitative analysis of valiolamine in biological samples by high-performance liquid chromatography with pre-column UV derivatization.

A rapid, low-cost, high sensitive and quantitative method to detect valiolamine in a medium for microbial culture, involving derivatization with a new labeling reagent, 4-methoxybenzenesulfonyl fluoride (MOBS-F), followed by reverse-phase high-performance liquid chromatography with ultraviolet (UV) detection with simple operation procedure. 4-Methoxybenzenesulfonyl chloride (MOBS-Cl) and 2-nitrobenzenesulfonyl chloride (NBS-Cl) were compared with MOBS-F as novel reagents in this paper, and the MOBS-F was chosen as the most suitable derivatization reagent. The column was thermostatic at 35 degrees C, the mobile phase flow-rate was 1.0mL/min and the detection wavelength was 240nm. For a biological sample, the separation of the derivatives was achieved using a gradient mobile system. The elution program is 88% phosphate buffer (50mM; pH=3.0) and 12% methanol for 23min, then 70% of phosphate buffer and 30% methanol for another 15min and finally 88% of phosphate buffer and 12% of methanol for 5min to re-equilibrate the column. The optimized conditions of the derivatization were as follows: derivatization reaction temperature 30 degrees C; derivatization reaction pH value 11.0, reaction time 10min and MOBS-F concentration higher than 1.5mg/mL for standard solutions and higher than 5.0mg/mL for the biological sample. Calibration curves were linear in the range of 0.050-25microg/mL for the standard solutions and 1.0-75microg/mL for the biological sample. The sensitive analytical method is helpful to control the biotechnological process of voglibose production and product quality control.

An electrochemical impedimetric immunosensor for label-free detection of Campylobacter jejuni in diarrhea patients' stool based on O-carboxymethylchitosan surface modified Fe3O4 nanoparticles.

A novel electrochemical impedimetric immunosensor based on O-carboxymethylchitosan surface modified Fe(3)O(4) nanoparticles (denoted as OCMCS-Fe(3)O(4) nanoparticles) was developed for rapid detection of Campylobacter jejuni, which is becoming the most common cause of gastroenteritis in developed countries and raising major public health concerns worldwide. In the present study, anti-FlaA monoclonal antibodies 2D12 (denoted as 2D12McAbs) were immobilized on OCMCS-Fe(3)O(4) nanoparticles. The detection was performed by measuring relative change in impedance before and after 2D12McAbs-Campylobacter jejuni reaction with the technique of electrochemical impedance spectroscopy. Under the optimized conditions, the relative change in impedance was proportional to the logarithmic value of Campylobacter jejuni concentrations in the range of 1.0x10(3) to 1.0x10(7) CFU/mL (r=0.991). The advantages of the OCMCS-Fe(3)O(4) nanoparticle-based immunosensor are simplicity of use, fast response, wide linear range, acceptable reproducibility and long stability. Moreover, the immunosensor could be regenerated by being treated with glycine-HCl buffer solution (pH 2.8). We demonstrate the convenient application of the novel immunosensor for the detection of Campylobacter jejuni in diarrhea patients' stool samples.

A reusable capacitive immunosensor for detection of Salmonella spp. based on grafted ethylene diamine and self-assembled gold nanoparticle monolayers.

Fabrication of a novel capacitive immunosensor based on grafted ethylene diamine and self-assembled gold nanoparticle monolayer on glassy carbon electrode for the detection of Salmonella spp. is described for the first time. In the present study, the Salmonella spp. monoclonal antibodies (denoted as McAbs) was immobilized on gold nanoparticles. Interaction of McAbs and Salmonella spp. was detected directly using the electrochemical impedance spectroscopy (EIS) technique. The experimental results showed that the concentration of antigen was measured through the relative change in capacitance in the corresponding specific binding of Salmonella spp. and McAbs. Under the optimized conditions, the relative changes in capacitance were proportional to the logarithmic values of Salmonella spp. concentrations in the range of 1.0 x 10(2) to 1.0 x 10(5) CFU mL(-1) (r = 0.991) with the detection limit of 1.0 x 10(2) CFU mL(-1). The stability of proposed immunosensor could be estimated by determining the relative change in capacitance, which remained almost the same in two months and decreased gradually to 85.3% of initial value after four months' storage. The used immunosensor could be regenerated repeatedly by immersing in glycine-HCl buffer solution (pH 2.8). Finally, the proposed immunosensor was successfully used for the detection of Salmonella spp. in lab-processed commercial pork samples.