Magnetic solid-phase extraction based on a polydopamine-coated Fe3O4nanoparticles absorbent for the determination of bisphenol A, tetrabromobisphenol A, 2,4,6-tribromophenol, and (S)-1,1’-bi-2-naphthol in environmental waters by HPLC

Preparation of amphiphilic poly(divinylbenzene-co-N-vinylpyrrolidone)-functionalized polydopamine magnetic nanoadsorbents for enrichment of synthetic cannabinoids in wastewater

Concerns have been raised about synthetic cannabinoids (SCs), which are among the most often trafficked and used illegal substances. An analytical method that holds promise for determining illicit drug use in the general population is wastewater-based epidemiology (WBE). Unfortunately, the concentration of SCs in wastewater is often extremely low on account of their hydrophobic nature, thus presenting a significant obstacle to the accurate detection and quantification of SCs using WBE. In this study, we present novel magnetic nanomaterials as amphiphilic adsorbents for pretreatment of wastewater using magnetic solid phase extraction (MSPE). Polydopamine-modified Fe3O4 nanoparticles were used as the magnetic core and further functionalized with poly(divinylbenzene-N-vinylpyrrolidone). Coupled with UHPLC-MS/MS analysis, an analytical method to simultaneously detect nine SCs at trace-levels in wastewater was developed and validated, enriching 50 mL wastewater to 100 μL with limits of detection (LOD) being 0.005-0.5 ng L-1, limits of quantification (LOQ) being 0.01-1.0 ng L-1, recoveries ranging from 73.99 to 110.72%, and the intra- and inter-day precision's relative standard deviations less than 15%. In comparison to the time-consuming conventional column-based solid phase extraction, the entire MSPE procedure from sample pre-treatment to data acquisition could be finished in one hour, thus largely facilitating the WBE method for drug surveillance and control.

Preparation of poly(methacrylic acid-co-ethylene glycol dimethacrylate)-functionalized magnetic polydopamine nanoparticles for the extraction of six cannabinoids in wastewater followed by UHPLC-MS/MS

Phytocannabinoids and their synthetic analogs (natural and synthetic cannabinoids) are illicit drugs that are widely abused worldwide. Wastewater-based epidemiology (WBE) is an objective approach for the estimation of population-level exposure to a wide range of substances, especially drugs of abuse. However, the concentrations of cannabinoids in wastewater are extremely low (frequently at the levels of nanograms per liter), and the existing pretreatment procedures for wastewater have the disadvantages of time-consumption or low extraction recoveries. This study aimed to propose a novel poly (methacrylic acid-co-ethylene glycol dimethacrylate)-functionalized polydopamine-coated Fe₃O₄ nanoparticle (Fe₃O₄@PDA@poly (MAA-co-EGDMA)) as an adsorbent, and provide a highly sensitive quantitative analytical technique for the detection of five synthetic cannabinoids (SCs: 5 F-EDMB-PINACA, FUB-APINACA, MDMB-4en-PINACA, MDMB-FUBINACA, and PB-22) and one cannabis-related human metabolite (THC-COOH) in wastewater. The magnetic adsorbents were fully characterized by transmission electron microscopy (TEM), infrared spectroscopy (IR), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS). Subsequently, an MSPE-UHPLC-MS/MS method was developed and validated for the determination of six trace analytes in wastewater. The validation results showed that the method has limits of quantification as low as 0.1-1.0 ng/L. Additionally, the recoveries ranged from 62.81 to 124.02%, and the relative standard deviations (RSDs) of intraday and interday precision were less than 15%. This MSPE-UHPLC-MS/MS method was successfully applied to real wastewater samples, and the whole analytical process of one sample from pretreatment to the obtained quantitative results was completed in less than 30 min. Thus, the proposed method based on Fe₃O₄@PDA@poly (MAA-co-EGDMA) is a convenient, rapid, sensitive and reliable method for the determination of trace psychoactive drugs in wastewater.

Potential of sodium dodecyl sulfate micellar solutions as eluents in magnetic dispersive micro-solid phase extraction with polydopamine-coated magnetite nanoparticles. Application to antidepressant drugs

In this paper, the potential of micellar solutions of the anionic surfactant sodium dodecyl sulfate (SDS) as eluents in dispersive micro-solid phase extraction (D-μSPE) using polydopamine-coated magnetite nanoparticles (Fe₃O₄@PDA NPs) for the extraction and preconcentration of seven basic drugs (bupropion, citalopram, fluoxetine, mianserin, nomifensine, trimipramine, and viloxazine) is explored for the first time (to the best to our knowledge) and compared with conventional hydro-organic eluents. The impact of the sample solution pH, Fe₃O₄@PDA NPs and PDA coating amounts and extraction time on the extraction efficiency (EE), as well as the composition of the eluent on the overall efficiency (OE) are studied. Under the selected experimental conditions (50 mg of Fe₃O₄@PDA NPs, 100 μL of 1 M NH₃, 5 min of extraction time and 0.15 M SDS at pH 2.6 as eluent), EE and OE values were higher than 90% for all compounds and for the most hydrophobic compounds (trimipramine, fluoxetine and mianserin), respectively. The results shown in this paper demonstrate the suitability of Fe₃O₄@PDA NPs as a sorbent for the extraction of antidepressants as well as the advantages of using SDS micellar solutions over classic hydro-organic eluents containing methanol, acetonitrile or tetrahydrofuran. Finally, the stability and reusability of the Fe₃O₄@PDA NPs is proven.

Pseudo-template molecularly imprinted polymeric fiber solid-phase microextraction coupled to gas chromatography for ultrasensitive determination of 2,4,6-trihalophenol disinfection by-products

2,4,6-trihalorophenol disinfection by-products (DBPs) have strong toxicity to be needed for monitoring. In this study, two kind of molecularly imprinted polymeric fibers were prepared using 2,4,6-trichlorophenol as template and tricuronic phloroglucinol (MOP) as pseudo-template, respectively. The two fibers were assembled as solid phase microextraction (SPME) fiber to extract 2,4,6-trihalophenol DBPs from water and detect them by gas chromatography coupled to electron capture detector (GC-ECD). The results of F-test and t-test stated that there are significant difference in the analytical results of 2,4,6-trichlorophenol between using the fiber based on 2, 4, 6-trichlorophenol as template and MOP as pseudo-template. It was found that the carry-over of template (2,4,6-trichlorophenol) leaked from the fiber in GC thermal desorption, resulting in the wrong quantitative analytical result for 2,4,6-trichlorophenol in water. Hence, molecularly imprinted polymeric fibers based on MOP as pseudo-template was applied for the determination of 2,4,6-trihalophenol DBPs in water combined with GC-ECD. The selectivity of the fiber for 2,4,6-trihalophenol DBPs was investigated and demonstrated. Under the optimized condition, the method has much lower limit of detection (0.5-1.1 pg mL^-1) than most reported methods. The method was applied for the determination of 2,4,6-trihalophenol DBPs in environmental water and the relative recoveries were found to be in the range from 77.1% to 105.6% and the relative standard deviation was 0.5-9.4%. 2,4,6-tribromophenol was found at concentration of 0.054 ng mL^-1 in a swimming pool.

Amino-based magneto-polymeric-modified mixed iron hydroxides for magnetic solid phase extraction of phenol residues in environmental samples

Mixed iron hydroxides (MIHs) modified with different amino-based polymeric materials, including aminopropyltriethoxysilane, polydopamine, diaminobenzoic acid, polyaniline, and polyphenylenediamine, were comparatively investigated as sorbents for the extraction of phenol compounds. Polyphenylenediamine-modified mixed iron hydroxides (MIH@PPDA) showed high adsorption capability for most target analytes. Its ferromagnetic behavior, with a magnetization of 17.38 emu g^-1, was sufficient for subsequent use in magnetic solid-phase extraction (MSPE). The functional groups, morphology, and magnetic properties of this magnetic nanomaterial were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction, and CHN analysis. High-performance liquid chromatography with a photodiode array detector was used to quantify phenol compounds. The experimental parameters affecting the efficiency of the entire MSPE process were optimized. Good linearity in the range of 0.5-1000 µg L^-1 was obtained (depended on the compound). The detection and quantitation limits varied from 0.01 to 0.3 µg L^-1 and 0.03 to 0.9 µg L^-1, respectively. The enrichment factors for all phenol compounds were in the range of 80-285. The precision in terms of intra- and inter-day relative standard deviations were below 5.8% and 6.2%, respectively. The developed MSPE method was applied to analyze phenol compounds in diverse samples, including soil, drinking water, and fruit. Relative recoveries of 76.7-130.1% were obtained. The MIH@PPDA magneto-polymeric sorbent exhibits good stability and is reliable for a variety of phenol compounds.

Air-assisted liquid-liquid microextraction based on the solidification of floating deep eutectic solvents for the simultaneous determination of bisphenols and polycyclic aromatic hydrocarbons in tea infusions via HPLC

Deep eutectic solvents (DESs) are a new class of green "designer solvent"; its physicochemical properties can be easily tuned by adjusting DES' constituents, chemical ratio and water content. In this study, three hydrophobic DESs with low viscosity, low density, and melting points close to room temperature were designed and synthesized. Based on these DESs, an air-assisted liquid-liquid microextraction technique was developed based on the solidification of floating DESs for the simultaneous determination of bisphenols and polycyclic aromatic hydrocarbons (PAHs) via HPLC. The microextraction parameters were optimized via the Plackett-Burman design and response surface methodologies. The method shows satisfactory linearity (R² ≥ 0.9928), a low limit of detection (0.16-0.75 μg L^-1) and satisfactory precision (≤2.3%), and was successfully applied for the simultaneous determination of bisphenols and PAHs from tea infusions with satisfactory recoveries (82.0-116.6%). This method is simple, rapid, economical, environmentally compatible, dispersive solvent-frees and centrifugation-free, and has promising applications in food safety.

Zeolitic imidazolate framework-8 coated Fe3O4@SiO2 composites for magnetic solid-phase extraction of bisphenols

A new magnetic composite material ZIF-8 coated Fe₃O₄@SiO₂ was employed for preconcentration and detection of trace BPs in water and plastic products.

Electrochemical determination of tetrabromobisphenol A in water samples based on a carbon nanotubes@zeolitic imidazole framework-67 modified electrode

Carbon nanotubes@zeolitic imidazole framework-67 (CNTs@ZIF-67), a conductive composite was prepared from carboxylic carbon nanotubes and a cobalt–imidazole framework. It possesses an excellent adsorption capacity (92.12 mg g⁻¹) for the flame retardant tetrabromobisphenol A (TBBPA). The composite was characterized by transmission and scanning electron microscopy, FTIR and X-ray diffractometry. It was then used to modify an acetylene black electrode. Electrochemical studies showed the current response of the modified electrode to be larger than that of electrodes modified with CNTs-COOH or ZIF-67 only. Electrochemical impedance spectroscopy showed this material combination to improve the conductivity of ZIF-67. The addition of perfluorodecanoic acid further improves the response. The sensor is stable, reproducible, and has a linear range of 0.01–1.5 μM TBBPA concentration, with a 4.2 nM detection limit (at S/N = 3). The sensor was successfully applied to the detection of TBBPA in spiked rain and pool water samples.

Carbon nanotubes@zeolitic imidazole framework-67 (CNTs@ZIF-67), a conductive composite was prepared from carboxylic carbon nanotubes and a cobalt–imidazole framework.

Fabrication of glucose-derived carbon-decorated magnetic microspheres for extraction of bisphenols from water and tea drinks

Glucose-derived carbon-decorated magnetic microspheres were synthesized by an easy hydrothermal carbonization method and used as a high-efficiency adsorbent to extract bisphenols in water and tea drinks. The as-prepared carbon-decorated magnetic microspheres had a well-defined core-shell structure with a shell thickness of about 5 nm. The microspheres possessed high saturation magnetization at 60.8 emu/g and excellent chemical stability in aqueous solution. The experimental parameters affecting the extraction efficiency, including extraction time, pH, adsorbent dosage, desorption solvents, desorption time, and solution volume were evaluated. Electrostatic and π-π interactions were the major driving forces during extraction. Overall, a new magnetic solid-phase extraction method of determining bisphenols was developed on the basis of as-prepared magnetic microspheres. The method had a wide linear range, low limits of detection (0.03-0.10 µg/L), and high recoveries (85.4-104.6%).

Targeted delivery of hesperetin to cartilage attenuates osteoarthritis by bimodal imaging with Gd2(CO3)3@PDA nanoparticles via TLR-2/NF-κB/Akt signaling

The progressive degeneration of cartilage marks the advancement of osteoarthritis (OA), which requires specific targeted treatment for effective cartilage repair. However, there is still no efficient cartilage delivery system or novel magnetic resonance (MR) contrast agent (CA). Herein, we report the synthesis of a novel class of MR CA, Gd₂(CO₃)₃-based nanoparticles (NPs), from a simpler and "greener" approach than previous ones. After the coating of polydopamine (PDA) onto the Gd₂(CO₃)₃ core, we further anchored a cartilage-targeting peptide and loaded hesperetin (Hes) into NPs (Hes-Gd₂(CO₃)₃@PDA-PEG-DWpeptide, HGdPDW), showing excellent cartilage affinity and MR suitability. Additionally, the synthesized HGdPDW exerted significant protective effects against IL-1β stimulation, as shown by the decreased apoptosis and inflammation and increased maturation of chondrocytes in vitro. More importantly, RNA-seq analyses showed the significant reduction of TLR-2 in IL-1β-treated chondrocytes, and this reduction was followed by the inactivation of NF-κB/Akt signaling, leading to the protective effect of HGdPDW. By the establishment of anterior cruciate ligament transection (ACLT) OA mice, the bimodal MRI/IVIS imaging demonstrated the effective cartilage-binding ability of HGdPDW in OA knees with low cytotoxicity, which alleviated the gradual degeneration of articular cartilage in vivo by inhibiting TLR-2 in chondrocytes. Taken together, these results suggest that HGdPDW could target cartilage effectively, thereby protecting chondrocytes from apoptosis and inflammation via TLR-2/NF-κB/Akt signaling. We hope this new class of MRI CA could be applied in not only other fields using MRI technology but also the treatment of general cartilage-related diseases; this application will undoubtedly extend the treatment of OA clinically.

A miniaturized solid-phase extraction adsorbent of calix[4]arene-functionalized graphene oxide/polydopamine-coated cellulose acetate for the analysis of aflatoxins in corn

A calix[4]arene-functionalized graphene oxide/polydopamine-coated cellulose acetate adsorbent was fabricated for the pre-concentration of aflatoxins. The highly porous developed adsorbent does not produce the high backpressure that normally occurs in particle-packed cartridges and its large surface area helps to improve adsorption. The highly efficient adsorption of aflatoxins by the hybrid adsorbent is facilitated via hydrogen bonding and hydrophobic and π-π interactions. Polymerization time, amount of calix[4]arene-functionalized graphene oxide, type and volume of desorption solvent, sample pH, sample volume, and sample flow rate were optimized. The linearity of aflatoxin B1 was in the range of 0.01-10.0 μg/kg, aflatoxin B2 was in the range of 0.02-10.0 μg/kg and aflatoxin G1 and aflatoxin G2 were in the range of 0.050-10.0 μg/kg. The limits of detection were 0.01 μg/kg for aflatoxin B1, 0.02 μg/kg for aflatoxin B2 and 0.05 μg/kg for aflatoxin G1 and aflatoxin G2. The developed calix[4]arene-functionalized graphene oxide/polydopamine-coated cellulose acetate adsorbent was successfully utilized for the analysis of aflatoxins from corn samples and the extraction efficiency was satisfactory with obtained recoveries from 83.0 to 106.7%. Moreover, fabricated adsorbent is easy to prepare, inexpensive, and can be reused.

Ultrasensitive magnetic field-assisted surface plasmon resonance immunoassay for human cardiac troponin I

An ultrasensitive surface plasmon resonance (SPR) immunoassay was developed for the specific detection of human cardiac troponin I (cTnI), a principle diagnostic marker for myocardial damage. The thin gold film evaporated on a glass slate, which was employed as the SPR sensing film, was modified by hollow gold nanoparticles (HGNPs) and polydopamine (PDA) sequentially, and then was immobilized with antibodies for specific recognition of target analyte. Electronic coupling of the surface plasmon waves originating from the HGNPs and the gold film leads to the remarkable amplification of SPR response. The PDA film modified on the gold film via self-polymerization of dopamine (DA) facilitates the direct immobilization of capture antibodies (cAb). To separate and enrich the target analyte, PDA-wrapped magnetic multi-walled carbon nanotubes (MMWCNTs-PDA) were conjugated with detection antibodies (dAb) and used as the extracting agent for the magnetic extraction of cTnI in sample. Large surface area of MMWCNTs-PDA ensures its loading capacity for dAb, as well as its extraction efficiency for cTnI. By serving as the "vehicles" for fast delivering the concentrated analyte to the SPR sensing surface, MMWCNTs-PDA-dAb also overcomes the disadvantage of slow diffusion-limited mass transfer and matrix interference effect in regular patterns. The combination of the above improvements results in the significant sensitivity enhancement of the SPR immunoassay. The concentration of cTnI with minimum detectable SPR response obtained by the present assay is 1.25ngmL^-1, which is 1000-fold lower than that obtained by the traditional SPR immunoassay based on PDA-modified gold film.

Acetylene black paste electrode modified with molecularly imprinted polymers/graphene for the determination of bisphenol A

A novel nanocomposite of molecularly imprinted polymers and graphene sheets was fabricated and used to obtain a highly conductive acetylene black paste electrode with high conductivity for the detection of bisphenol A. The two-dimensional structure and the chemical functionality of graphene provide an excellent surface for the enhancement of the sensitivity of the electrochemical sensor and the specificity of molecularly imprinted polymers to improve detection of bisphenol A. The synergistic effect between graphene and molecularly imprinted polymers confers the nanocomposite with superior conductivity, broadened effective surface area and outstanding electrochemical performance. Factors affecting the performance of the imprinted sensor such as molecularly imprinted polymers concentration, foster time and scan rate are discussed. The sensor successfully detects bisphenol A with a wide linear range of 3.21 × 10^-10 to 2.8 × 10^-1 g/L (R = 0.995) and a detection limit of 9.63 × 10^-11 g/L. The fabricated sensor also possessed high selectivity and stability and exhibits potential for environmental detection of contaminants and food safety inspection.