Simultaneous determination of multiple mycotoxins in corn and wheat by high efficiency extraction and purification based on polydopamine and ionic liquid bifunctional nanofiber mat.

Due to the universality and harmfulness of mycotoxin co-contamination in cereals, it is of great significance to simultaneously monitor various mycotoxins co-polluted to ensure food safety and public health. In this work, a nanofiber mat modified by polydopamine and ionic liquid (PDA-IL-NFsM) was prepared and utilized as a solid-phase extraction (SPE) adsorbent for the simultaneous quantitative detection of multiple mycotoxins in corn and wheat. The PDA-IL-NFsM can form multiple retention mechanisms with the targets through hydrogen bond, π-π interaction, electrostatic or hydrophobic interaction, it shows favorable simultaneous adsorption performance (adsorption efficiency mostly higher than 88.27%) for fifteen mycotoxins in seven classes. Moreover, it can significantly reduce the matrix effect (lower than -13.69%), showing a good purification effect on the sample matrix. Based on the superior performance of PDA-IL-NFsM, a simple sample preparation method was established. The sample extract is simply diluted with water for SPE, and the eluent can be directly collected for ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) analysis. The detection limit can reach 0.04-4.21 µg kg-1, the recovery was 80.09%-113.01%, and the relative standard deviations of intra-day and inter-day precision were 2.80%-14.81% and 0.68%-13.80% respectively. The results show that the proposed method has good sensitivity, accuracy and precision, and has practical application potential.

A nanofiber-mat-based solid-phase sensor for sensitive ratiometric fluorescent sensing and fine visual colorimetric detection of tetracycline.

Sensitive and real-time tetracycline (TC) monitoring method is of great significant for food safety and human health. Herein, a novel TC dynamic sensing mode based on a solid-phase nanofiber mat (NFM) sensor SP@COF/SDBS/PS NFM was constructed for the first time, where spiropyran-modified covalent organic framework (SP@COF) with red emissions (λem = 620 nm) was used as the reference fluorescence. Utilizing the adsorptive interaction between SP@COF/SDBS/PS NFM and TC, a PS-TC-SDBS supramolecular complex with a large rigid structure was formed, thus enhancing the fluorescence of TC (λem = 550 nm). The dynamic solid-phase sensing mode is unique and can be employed to selectively adsorb TC, with reduced interference by impurities in complex samples, and thus the sensitive TC ratiometric fluorescent sensing with a detection limit of 2.14 nM, and fine visual colorimetric detection with polychromatic wide color range (red-orange-yellow-green) was realized.

Efficient and simple simultaneous adsorption removal of multiple aflatoxins from various liquid foods.

In this study, a polydopamine modified nanofibers membrane (PDA-PS NFsM) was prepared and evaluated as the adsorbent for simultaneous removal of a variety of aflatoxins in various liquid foods, including edible oil, soy sauce and milk, rice vinegar and liquor. The removal efficiency for every single aflatoxin from all samples involved above was more than 76.5% within 1 h at 25 °C, except the liquors with higher ethanol content, for which the efficiency was lower. Moreover, PDA-PS NFsM can be removed directly after the adsorption process without any subsequent separation. The results suggested that the adsorption mechanism of the aflatoxins onto PDA-PS NFsM was chemisorption-based spontaneous endothermic reaction and aflatoxins were adsorbed by electrostatic interaction, hydrogen bonding and π-π interaction. This study confirmed that the PDA-PS NFsM has a good practical application potential in the simultaneous removal of a variety of aflatoxins from various liquid foods.

Efficient, rapid and simple adsorption method by polydopamine polystyrene nanofibers mat for removal of multi-class antibiotic residues in environmental water.

Polydopamine polystyrene nanofibers mat (PDA-PS NFsM) was prepared as an adsorbent for the simultaneous removal of multiple antibiotic residues in environmental water for the first time. PDA-PS NFsM can directly be used to adsorb 18 antibiotic residues belonging to 8 classes without any pretreatment of water samples. The adsorption process was completed within 5 min. All antibiotics could be removed at the same time, and the removal rate of each target was above 85%. Moreover, the used PDA-PS NFsM can be easily separated from the environmental water by taking out directly, and can be reused for 10 times after simple regeneration. The thermodynamic and kinetic properties of PDA-PS NFsM adsorption of antibiotic residues were further investigated consequently. It was found that the adsorptions of PDA-PS NFsM to the targets were spontaneous and endothermic process (ΔG<0, ΔH>0, ΔS>0). The results of adsorption kinetic experiments illustrated that the adsorption process was rapid, the adsorption equilibrium of which can be reached in 5 min. Adsorption isotherm experiments proved that the adsorption process of PDA-PS NFsM was consistent with Langmuir adsorption (R2 > 0.994), and the maximum adsorption capacity of PDA-PS NFsM towards all targets were 123.76 mg g-1. The developed method is rapid and simple, and can efficiently adsorb and remove a variety of antibiotics in environmental water, which has good practical application prospect.

[Determination of tetracycline and fluoroquinolone residues in fish by polydopamine nanofiber mat based solid phase extraction combined with ultra performance liquid chromatography-tandem mass spectrometry].

Tetracyclines and fluoroquinolones are common antibacterial drugs used in aquaculture, and their residues may pose a risk to human health. The low concentration of drug residues and complex matrixes such as fats and proteins in aquatic products necessitate the urgent development of efficient sample pretreatment methods. Solid phase extraction (SPE) is the most common sample pretreatment method, in which the core is an adsorbent. Compared with traditional SPE adsorbents, nanofiber mat (NFsM) has more interaction sites because of their large specific surface area. Furthermore, NFsMs modified with specific functional groups can significantly improve the extraction efficiency of tetracyclines and fluoroquinolones. Polydopamine (PDA) is spontaneously synthesized by the oxidative self-polymerization of dopamine-hydrochloride in alkaline solutions (pH>7.5). Because of its rich amino and catechol groups, PDA can form π-π stacking, electrostatic attraction, hydrophobic interaction, and hydrogen bonding interactions with target molecules. By exploiting the above advantages, polystyrene (PS) NFsM, as a template, was prepared by the electrostatic spinning method, and PDA-PS NFsM was obtained by functional modification of PDA through self-polymerization. Fourier transform infrared spectroscopy (FT-IR) and field-emission scanning electron microscopy (FESEM) were used to characterize the synthesized PS NFsM and PDA-PS NFsM. It was proved that PDA was successfully modified on the PS NFsM, with the SEM images revealing a rough outer core shell structure and an inner honeycomb structure. Subsequently, the handmade SPE column with PDA-PS NFsM was completed. A novel and efficient screening analytical method based on PDA-PS NFsM for the simultaneous determination of three tetracyclines (tetracycline (TET), chlortetracycline (CTC), and oxytetracycline (OTC)) and three fluoroquinolones (enrofloxacin (ENR), ciprofloxacin (CIP), and norfloxacin (NOR)) in fish by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established. The SPE procedure was optimized to develop an efficient method for sample preparation. Evaluate parameters including the amount of NFsM usage, ionic strength, flow rate of the sample solution, composition of eluent, and breakthrough volume were investigated. Only (20±0.1) mg of PDA-PS NFsM was sufficient to completely adsorb the targets, and the analytes retained on NFsM could be eluted by 1 mL of formic acid-ethyl acetate (containing 20% methanol) (1∶99, v/v). The residues were redissolved in 0.1 mL 10% methanol aqueous solution containing 0.2% formic acid. In addition, no adjustment of the pH and ionic strength of the sample solutions was required, and the breakthrough volume was 50 mL. The limits of detection (LODs) and limits of quantification (LOQs) of the six target compounds were measured at 3 times and 10 times the signal-to-noise ratio (S/N), respectively. The LODs and LOQs were 0.3-1.5 µg/kg and 1.0-5.0 µg/kg, respectively. The linear ranges of the six target compounds were LOQ-1000 µg/kg, and the coefficient of determination (R2) was greater than 0.999. To evaluate the accuracy and precision, blank spiked samples at three levels (low, medium, and high) were prepared for the recovery experiments, and each level with six parallel samples (n=6). The recoveries ranged from 94.37% to 102.82%, with intra-day and inter-day relative standard deviations of 2.38% to 8.06% and 4.10% to 9.10%, respectively. To evaluate the purification capacity of PDA-PS NFsM, the matrix effects before and after SPE were calculated and compared. Matrix effects before SPE were -12.98% to -38.68%. After the completion of SPEbased on PDA-PS NFsM, the matrix effect of each target analyte was significantly reduced to -2.15% to -7.36%, which proved the significant matrix removal capacity of PDA-PS NFsM. Finally, the practicality of this method was evaluated by using it to analyze real samples. This SPE method based on PDA-PS NFsM is efficient, practical, and environmentally friendly, and it has great potential for use in the routine monitoring of drug residues in fish.

Toxic and active material basis of Aconitum sinomontanum Nakai based on biological activity guidance and UPLC-Q/TOF-MS technology.

BACKGROUND: As a folk medicine, Aconitum sinomontanum Nakai (Ranunculaceae, Gaowutou, in Chinese) is used by traditional healers to treat many disorders, including pain and inflammatory diseases, but it exhibits the toxic side effects. This study aimed to obtain toxic extract parts from A. sinomontanum roots and to further evaluate the antinociceptive and anti-inflammatory effects of toxic extract parts on mice. This work also aimed to identify various chemical compositions of the toxic and active extract parts and evaluate the safety profile of this plant. METHODS: Experimental drugs (petroleum ether, chloroform, ethyl acetate, n-butanol, alcohol and water extracts) were obtained through systematic solvent extraction from 95 % ethanol extract from A. sinomontanum roots. An acute toxicity test was conducted to compare the toxicity of different extracts administered at the maximum dose to screen a highly toxic extract. In pharmacodynamic activity analysis, the antinociceptive activity of the A. sinomontanum toxic extract was assessed using an acetic acid-induced abdominal writhing model and a hot plate test. Anti-inflammatory activity was assessed in terms of xylene-induced inflammation. Ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS) was performed to establish a chromatographic fingerprint and to identify various chemical components of the toxic and active extract. RESULTS: Chloroform, water and n-butanol extracts elicited significant toxic effects and had LD50 of 89.65, 1805.40 and 24409.41 mg/kg, respectively. Antinociceptive and anti-inflammatory activities indicated that the chloroform extract significantly alleviated (p < 0.01) the pain induced by acetic acid with an inhibition rate of 44.7 % (5.9 mg/kg) and 50.4 % (17.7 mg/kg). The chloroform extract also significantly (p < 0.01) increased the latency time during the hot plate test. The latency time at 5.9 and 17.7 mg/kg increased from 15.6 ± 4.1 s to 47.3 ± 6.4 s and from 16.3 ± 3.8 s to 49.8 ± 7.6 s (p < 0.01), respectively, 2 h after treatment. In the inflammatory test, the chloroform extract significantly reduced (p < 0.01) the xylene-induced mouse ear oedema with an inhibition rate of 45.48 % (5.9 mg/kg) and 51.46 % (17.7 mg/kg), respectively. This result indicated that A. sinomontanum chloroform extract was also the active extract part of A. sinomontanum. Phytochemical analysis revealed the presence of alkaloids in the chloroform extract. A total of 30 compounds were detected, and 23 compounds, including lappaconine, ranaconidine, 8-O-acetylexcelsine, sinomontanine H, finaconitine, lappacontine, N-dacetyllappaconitine, ranaconitine and isolappaconitine, were identified. CONCLUSIONS: A. sinomontanum chloroform extract possesses antinociceptive and anti-inflammatory activities and exhibits significant toxic effects. Phytochemical analysis indicated that some alkaloids may be the main bioactive ingredient responsible for the toxicity and efficacy of A. sinomontanum. This work contributes to the determination of the safety of the medicinal use of A. sinomontanum roots.