Preparation of chitosan-modified magnetic Schiff base network composite nanospheres for effective enrichment and detection of hippuric acid and 4-methyl hippuric acid

ZIF-based boronic acid modified molecular imprinted polymers in combination with silver nanoparticles/glutathione coated graphene oxide adsorbent for the selective enrichment of ellagic acid

This study focuses on the extraction of ellagic acid (EA), a valued phenolic compound, from agricultural waste chestnut shell samples. A novel approach is introduced using a combination of boronic acid-modified molecularly imprinted polymer (ZIF@B@MIP) and a nanocomposite of graphene oxide-coated silver nanoparticles (GO@Ag@GSH) to enhance EA enrichment. ZIF@B@MIP precisely captured EA through boronate affinity-based molecular imprinting recognition. ZIF@B@MIP employs boronate affinity-based molecular imprinting recognition to precisely capture EA, while GO@Ag@GSH provides ample adsorption sites. The synergistic effect of ZIF@B@MIP and GO@Ag@GSH demonstrates excellent enrichment capability and selectivity for EA. High-performance liquid chromatography (HPLC) is employed for sensitive EA detection, achieving a maximum adsorption capacity of 46.25 mg g-1 and an imprinting factor of 3.01. The adsorption capacity to different structural analogue was investigated, and the selectivity coefficient was used to evaluate the selectivity, and its value was 1.16-3.01. The method successfully enriches EA in chestnut shell samples with a recovery rate of 95.6 %-110.1 %. This research presents an innovative approach for effective phenolic components enrichment from natural resources for pharmaceutical and biochemical applications.

Harnessing Small-Molecule Analyte Detection in Complex Media: Combining Molecularly Imprinted Polymers, Electrolytic Transistors, and Machine Learning

Small-molecule analyte detection is key for improving quality of life, particularly in health monitoring through the early detection of diseases. However, detecting specific markers in complex multicomponent media using devices compatible with point-of-care (PoC) technologies is still a major challenge. Here, we introduce a novel approach that combines molecularly imprinted polymers (MIPs), electrolyte-gated transistors (EGTs) based on 2D materials, and machine learning (ML) to detect hippuric acid (HA) in artificial urine, being a critical marker for toluene intoxication, parasitic infections, and kidney and bowel inflammation. Reduced graphene oxide (rGO) was used as the sensory material and molecularly imprinted polymer (MIP) as supramolecular receptors. Employing supervised ML techniques based on symbolic regression and compressive sensing enabled us to comprehensively analyze the EGT transfer curves, eliminating the need for arbitrary signal selection and allowing a multivariate analysis during HA detection. The resulting device displayed simultaneously low operating voltages (<0.5 V), rapid response times (≤10 s), operation across a wide range of HA concentrations (from 0.05 to 200 nmol L-1), and a low limit of detection (LoD) of 39 pmol L-1. Thanks to the ML multivariate analysis, we achieved a 2.5-fold increase in the device sensitivity (1.007 μA/nmol L-1) with respect to the human data analysis (0.388 μA/nmol L-1). Our method represents a major advance in PoC technologies, by enabling the accurate determination of small-molecule markers in complex media via the combination of ML analysis, supramolecular analyte recognition, and electrolytic transistors.

Immobilized horseradish peroxidase on boric acid modified polyoxometalate molecularly imprinted polymer for biocatalytic degradation of phenol in wastewater: Optimized immobilization, degradation and toxicity assessment

The degradation of phenol from wastewater is crucial for environmental protection. Biological enzymes, such as horseradish peroxidase (HRP), have shown great potential in the degradation of phenol. In this research, we prepared a hollow CuO/Cu2O octahedron adsorbent with a carambola matrix shape through the hydrothermal method. The surface of the adsorbent was modified by silane emulsion self-assembly, where 3-aminophenyl boric acid (APBA) and polyoxometalate (PW9) were combined with silanization reagents and grafted onto the surface. The adsorbent was then molecularly imprinted with dopamine to obtain boric acid modified polyoxometalate molecularly imprinted polymer (Cu@B@PW9@MIPs). This adsorbent was used to immobilize HRP, which served as a biological enzyme catalyst from horseradish. The adsorbent was characterized, and its synthetic conditions, experimental conditions, selectivity, reproducibility, and reusability were evaluated. The maximum adsorption amount of HRP under optimized conditions was 159.1 mg g-1, as determined using high-performance liquid chromatography (HPLC). At pH 7.0, the immobilized enzyme showed a high efficiency of up to 90.0% in removing phenol, after 20 min of reaction with 25 mmol L-1 H2O2 and 0.20 mg mL-1 Cu@B@PW9@HRP. Growth tests of aquatic plants confirmed that the adsorbent reduced harm. Gas chromatography-mass spectrometry (GC-MS) tests revealed that the degraded phenol solution contained about fifteen phenol derivatives intermediates. This adsorbent has the potential to become a promising biological enzyme catalyst for dephenolization.

Effective extraction of the metabolites of toluene and xylene based on a postsynthetic-modified magnetic covalent organic polymer

Toluene and xylene are volatile organic compounds, and long-term exposure to toluene and xylene may cause brain structure and nervous system damage. To evaluate exposure to toluene and xylene in the environment, it is usually possible to monitor their metabolites in organisms, hippuric acid (HA) and methylhippuric acid (MHA). In this work, we designed a new magnetic solid phase extraction (MSPE) sorbent, zirconium postsynthetic-modified magnetic covalent organic polymer (Fe₃O₄@COP-COOZr), for purifying and enriching HA and 4-MHA. Zirconium ions were immobilized on the magnetic COP surface by postsynthetic modification without the use of additional coating layers or chelating ligands. The developed Fe₃O₄@COP-COOZr interacted with HA and 4-MHA through the π-π stacking effect and electrostatic interactions, as well as strong chelation with coordinatively unsaturated zirconium sites. The promising affinity material of Fe₃O₄@COP-COOZr in MSPE had high stability and recyclability. The established MSPE-HPLC-UV method showed low sorbent consumption (10 mg) and high sensitivity (LODs less than 0.1 μg L^-1), and can be used for the analysis of HA and 4-MHA in real samples. The recoveries of the proposed method in real urine samples for the simultaneous determination of HA and 4-MHA were in the range of 83.5-103.2 %, and the RSDs were 0.9-7.1 %.

Post-synthetic modification of a magnetic covalent organic framework with alkyne linkages for efficient magnetic solid-phase extraction and determination of trace basic orange II in food samples

Efficient magnetic solid phase extraction using covalent organic frameworks (COFs) can find important applications in food safety. In this work, a sulfonate-functionalized magnetic COF (Fe₃O₄@COF-SO₃Na) was synthesized by self-polycondensation of two-in-one monomer 1,6-bis(4-formylphenyl)-3,8-bis((4-aminophenyl) ethynyl)) pyrene (BFBAEPy) on the surface of aminated Fe₃O₄ and a thiol-yne click reaction. It was further adopted as an adsorbent for the efficient magnetic solid-phase extraction (MSPE) of basic orange II. The selective adsorption experiment indicated that it displayed selective adsorption ability to basic orange II due to the ion exchange, hydrogen bonds, and π-π interactions. Under the optimized conditions, the proposed MSPE method coupled with HPLC-DAD showed excellent linearity in the range of 0.05-0.5 µg/mL (R² = 0.9997) for basic orange II. The lower limits of detection (LODs) for basic orange II were 1.0-1.4 µg/L for three food samples: yellow croaker, paprika and dried bean curd. The recoveries were 90.1-98.8% with relative standard deviations (RSDs) below 4.2%. Therefore, this work provides an effective strategy to modify magnetic COFs as absorbents in MSPE. Due to the tunability of functional groups in thiol‑yne click reactions, the functional groups of magnetic COFs can be readily designed to enrich their multifunctional applications. Meanwhile, this work proposed a new method to detect trace amounts of basic orange II in food samples.

One-step fabrication of COF-coated melamine sponge for in-syringe solid-phase extraction of active ingredients from traditional Chinese medicine in serum samples

In this study, a covalent organic framework (COF)-TpBD-supported melamine sponge (MS) was fabricated through a one-step hydrothermal method. The obtained monolithic column was then applied in in-syringe solid-phase extraction (IS-SPE) for the separation of three volatile ingredients from serum samples. Given credit for the superior adsorption capacity of the COF and the homogeneous microporous property of MS, the developed column exhibited satisfactory separation of the targets. And the dominating adsorption mechanism was the hydrophobic interaction forces between TpBD and targets and the high mass transfer efficiency provided by the large pore structure of MS. The results of dynamic adsorption showed that the MS@TpBD column displayed much better adsorption performance than blank MS and TpBD. And it has featured great reusability up to 5 cycles and obtained satisfied recovery values (87.9 ~ 110.3%) in serum samples. As a result of sample clean-up, this column offers low limit of detections (LODs) down to 0.014, 0.010, and 0.020 μg/mL, respectively. In summary, we believe that this convenient separation column has prominent application promise in the fields of separating activity ingredients in biological samples.

Magnetic Ti3C2 MXene Nanomaterials for Doxorubicin Adsorption from Aqueous Solutions: Kinetic, Isotherms, and Thermodynamic Studies

In this work, the magnetic Ti₃C₂ MXene functionalized with β-cyclodextrin was prepared and characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. The synthesized nanomaterial was used as an adsorbent to adsorb doxorubicin from aqueous solutions, and the experimental parameters that affected the adsorption efficiency were investigated. In addition, the adsorption characteristics including adsorption kinetics, adsorption isotherm, and thermodynamics were researched comprehensively. The adsorption kinetics of doxorubicin followed a pseudo-second-order kinetic model, which indicated that adsorption was the rate-limiting step, and the maximum adsorption capacity was 7.35 μg mg^-1 by shaking for 60 min at pH 7.0. The adsorption isotherm was well described using the Freundlich model, which implied that multilayer adsorption took place over the prepared nanomaterial for doxorubicin adsorption. The negative values of Gibbs free energy change (ΔG ⁰ < 0) demonstrated that doxorubicin adsorption was a spontaneous process. The positive values of entropy change (ΔS ⁰ > 0) implied that doxorubicin adsorption was an increasing random process. Enthalpy change values were positive (ΔH ⁰ > 0) and indicated that the adsorption of doxorubicin was endothermic. The adsorption percentage of doxorubicin remained in the range of 41.05-44.09%, and the relative standard deviation (RSD) based on the adsorption percentage through five replicate adsorption and desorption processes was 2.8%. These results indicated that the magnetic Ti₃C₂ MXene nanomaterials can be an effective adsorbent to adsorb DOX from aqueous solutions.