[Determination of ochratoxin A in human urine by HPLC-FLD after cleaned-up by molecularly imprinted polymer solid phase extraction column].

A method was developed for the determination of ochratoxin A (OTA) in human urine by HPLC-FLD after molecularly imprinted polymer solid phase extraction (MIP-SPE) column. After the pH being adjusted to 2.5 with 0.1 mol x L(-1) HC1, sample was cleaned up with MIP-SPE column for ochratoxin A, the analyte was analyzed by high performance liquid chromatography coupled with fluorescence detection (HPLC-FLD), and finally all the positive results were confirmed by LC-MS/MS. Recoveries from urine samples spiked with OTA at levels ranging from 2 to 20 ng x mL(-1) were 90.6%-101.9%, and RSDs were 0.1%-1.6%. Sixty-five volunteers living in Beijing took part in the study, of which 5 were found containing OTA in their urine and the highest value was 0.091 ng x mL(-1). The MIP-SPE column was firstly applied to purify and concentrate OTA in human urine, this method is simple, rapid and reliable and can be used to determine the contents of OTA in human urine.

A novel enzyme-immobilized flow cell used as end-column chemiluminescent detection interface in open-tubular capillary electrochromatography.

A novel enzyme-immobilized flow-through interface was designed for sensitive end-column chemiluminescent (CL) detection in open-tubular capillary electrochromatography (OTCEC). Enzyme was covalently bound on an aldehyde-activated polymer membrane immobilized in a flow cell to catalyze the CL reaction that occurred in it. Using glycine as the model analyte, N-(4-aminobutyl)-N-ethylisoluminol-derivatized glycine effused from the OTCEC column and triggered a horseradish peroxidase (HRP)-catalyzed CL reaction, to produce an enhanced detection signal. To obtain a satisfying result for complex biological sample analysis, a thiolated ß-cyclodextrin-modified gold nanoparticles-coated OTCEC column was adopted to improve the separation efficiency. Glycine can be assayed in the range of 0.50-200 µM (R(2) = 0.9921) with a detection limit of 0.12 µM (S/N of 3). The whole analysis process can be completed within 13 min with a theoretical plate number of 22,500. Compared to the previously reported solution-phase enzyme catalysis, pre-column and on-column immobilized enzyme catalysis for capillary electrophoresis detection, a significantly reduced enzyme consumption and greatly improved enzyme stability can be achieved with the use of this end-column enzyme-immobilized detection interface. The novel flow cell can be further applied in other capillary electrophoresis modes including capillary zone electrophoresis, capillary gel electrophoresis, and micellar electrokinetic chromatography. It is also suitable for some other detectors such as fluorimetric, ultraviolet-visible absorption spectrometric and electrochemical detectors.

Molecularly imprinted polymer-based solid phase clean-up for analysis of ochratoxin A in beer, red wine, and grape juice.

A simple, reliable, and low-cost method based on molecularly imprinted polymer as a selective sorbent of SPE was proposed for the determination of ochratoxin A (OTA) in beer, red wine, and grape juice by HPLC coupled with fluorescence detection (HPLC-FLD). Samples were diluted with water and cleaned up with an AFFINIMIP® SPE OTA column. After washing and eluting, the analyte was analyzed by HPLC-FLD. Under the optimized conditions, LOD and LOQ for OTA were 0.025 and 0.08 ng/mL, respectively. The recoveries of OTA from beer, red wine, and grape spiked at 0.1, 2, and 5 ng/mL ranged from 91.6 to 101.7%. Furthermore, after a simple regenerated procedure, the molecularly imprinted polymer based SPE column could be reused at least 14 times to achieve more than 80% recoveries of OTA in real samples. The developed method was applied to the detection of 30 beer, red wine, and grape juice samples and only four samples were contaminated by OTA with levels below the legal limits.

Colorimetric immunosensing using liposome encapsulated MnO2 nanozymes for SARS-CoV-2 antigen detection.

Development of specific signal reporters with signal amplification effect are highly needed for sensitive and accurate detection of pathogen. Herein, we design a colorimetric immunosensing nanosystem based on liposome encapsulated quantum dots-sized MnO2 nanozyme (MnO2QDs@Lip) as a signal reporter for ultrasensitive and fast detection of SARS-CoV-2 antigen. The pathogenic antigens captured and separated by antibody-conjugated magnetic beads (MBs) are further connected with antibody-modified MnO2QDs@Lip to form a sandwich-like immunocomplex structure. After triggered release, MnO2 QDs efficiently catalyze colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB, which can be qualitatively observed by naked eyes and quantitatively analyzed by UV-Vis spectra or smartphone platforms. By taking advantages of immuno-magnetic separation, excellent peroxidase-like catalytic activity of MnO2 QDs, and high encapsulation efficiency of MnO2QDs@Lip, ultrasensitive detection of SARS-CoV-2 antigen ranging from 0.1 pg/mL to 100 ng/mL is achieved within 20 min. The limit of detection (LOD) is calculated to be 65 fg/mL in PBS buffer. Furthermore, real clinical samples of SARS-CoV-2 antigens can be effectively identified by this immunosensing nanosystem with excellent accuracy. This proposed detection nanosystem provides a strategy for simple, rapid and ultrasensitive detection of pathogens and may shed light on the development of new POCT detection platforms for early diagnosis of pathogens and surveillance in public health.