Conventional chiral molecularly imprinted polymers (CMIPs) are constrained by the “single template–single target” recognition mode, which limits their chiral recognition spectrum. To address this issue, this study exploited the common core scaffold of β-blockers as the entry point. (S)-1-(Isopropylamino)-3-phenoxy-2-propanol (S-IPP), a byproduct of metoprolol production, was selected as a dummy template, with 4-vinylpyridine and itaconic acid synergistically employed as dual functional monomers. A dummy template-based CMIPs monolithic capillary column (DT-CMIPs@capillary) was directly prepared via in situ polymerization within the capillary, and a DT-CMIPs-CEC enantioseparation system was subsequently established. Through systematic optimization of the monolithic column preparation conditions and CEC separation parameters, enantioseparation of eight β-blockers was successfully achieved to varying degrees, with resolution values (RS) ranging from 0.53 to 9.83 and following a clear gradient that correlated with the structural similarity of each analyte to the dummy template. This gradient was highly correlated with the structural similarity of each drug molecule, thereby validating the effectiveness of the dummy template strategy in broadening the recognition spectrum. Furthermore, static adsorption experiments were conducted to determine the selectivity factor (SF), and the correlation between SF and RS was systematically analyzed. On this basis, a preliminary chiral recognition mechanism model was proposed from three aspects: thermodynamic selectivity, kinetic mass transfer, and structural matching integrity. This study transforms the industrial byproduct S-IPP into a functional recognition element, providing a cost-effective and broad-spectrum platform for the chiral analysis of β-blocker drugs, while also offering theoretical insights and experimental reference for the design of dummy template-based imprinted materials.
Olodaterol, indacaterol, and formoterol are the most frequently abused β2-agonists. The World Anti-Doping Agency (WADA) has imposed a threshold limit of 40 ng/mL for formoterol in urine and a total ban on olodaterol and indacaterol. Therefore, it is urgent to develop sensitive analytical methods for the identification and quantification of the three compounds. Herein, for the first time, we fabricated a sulfur rich covalent organic framework supported silver-nanoparticle (Ag-SCOF) substrate for surface enhanced Raman spectroscopy (SERS). Benefiting from the strong Ag-S covalent bonds, silver nanoparticles can be firmly anchored on the SCOF matrix to effectively suppress nanoparticle aggregation and improve substrate stability. Target β2-agonists can be enriched into electromagnetic hot spots via Ag-N interactions, thereby greatly amplifying Raman signals. The analytical enhancement factor of this substrate reaches 3.89 × 105. The limits of detection (LODs) for olodaterol, indacaterol, and formoterol reach 8.61 × 10⁻8, 8.03 × 10⁻8, and 9.63 × 10⁻8 g·mL⁻1, respectively. This Ag-SCOF SERS platform achieves rapid (within 3 min), fingerprint-based simultaneous detection, overcoming the drawbacks of conventional methods such as high cost, long assay time and low specificity. The proposed method fully meets the detection requirements of WADA regulations and food safety monitoring, and has great potential for on-site analysis of real samples.
As a key degradation product of adenosine triphosphate, the continuous increase in hypoxanthine (Hx) levels serves as a precise biochemical indicator of declining freshness in meat products. Therefore, it is vital to determine the Hx level in meat foods to ensure food safety. In this work, a highly donor-acceptor (D-A) conjugated manganese phthalocyanine-based covalent organic polymer (MnPc-COP) was employed as a nanozyme to mediate colorimetric-photothermal dual-modal sensing of Hx through an enzymatic cascade reaction with the assistance of xanthine oxidase (XOD). The MnPc-COP network, comprising homogeneously distributed Mn-N4 atomic sites and triazine rings, exhibited superior peroxidase (POD)-like activity. This feature endowed the MnPc-COP with the ability to decompose H2O2, which was generated from Hx by XOD, into O2•− via a POD activity-triggered reaction. Subsequently, the resulting O2•− oxidized the colorless TMB to form blue oxTMB. This process also led to a temperature elevation upon irradiation with near-infrared light. As a result, the MnPc-COP-based colorimetric and photothermal sensor demonstrated low limits of detection of 0.31 and 0.71 µM within wide linear ranges of 1.0 to 150.0 µM, respectively, together with high selectivity, good reproducibility, and excellent practicality for the detection of Hx in real meat foods. This dual-mode sensing platform holds great promise for the development of portable and intelligent devices, enabling real-time, on-site monitoring of meat freshness to better ensure food safety and quality control.
Aflatoxin B1 (AFB1) is a highly hazardous Group Ⅰ carcinogen that widely contaminates grain products. To realize rapid on-site detection, we developed an electrochemical sensor based on electrochemically modified graphene–carbon nanotube composite paper (EMCP), Prussian blue (PB), Au-Ag bimetallic nanoparticles and an aptamer–molecularly imprinted polymer (Apt-MIP) dual-recognition system. Density functional theory calculations were used to optimize the molecularly imprinted polymer, and machine learning was introduced to enhance the quantitative accuracy of electrochemical signals. The sensor displays a wide linear range of 10− 4–103 ng/mL with a low detection limit of 5.6 × 10− 2 pg/mL, and exhibits excellent stability, reproducibility, and selectivity. When applied to real soybean, peanut and corn samples, the recoveries ranged from 98.0
The timely and accurate identification of Escherichia coli (E. coli) plays a pivotal role in controlling foodborne infections and safeguarding public well-being. We designed a dual-mode sensing strategy based on manganese dioxide nanosheets (MnO2 NS) to detect E. coli through colorimetric and fluorescent methods. E. coli could catalyze the conversion of p-benzoquinone (BQ) to hydroquinone (HQ) via an enzymatic reaction. Subsequently, HQ reduced MnO2 NS to Mn2+, leading to a decrease in the oxidase-like activity of MnO2 NS towards 3, 3’, 5, 5’-tetramethylbenzidine (TMB) and amplex red (AR). As a result, based on the changes in absorbance at 652 nm and fluorescence intensity at 582 nm, E. coli was detected in the ranges 1.0 × 101 − 1.0 × 106 CFU/mL and 1.0 × 101 − 1.0 × 108 CFU/mL, respectively. The limits of detection were 1 CFU/mL and 5 CFU/mL, respectively. Furthermore, this MnO2 NS-based colorimetric and fluorescent sensing strategy enabled accurate detection of E. coli in spiked milk samples. In summary, the developed strategy demonstrates significant potential for practical applications in foodborne pathogen detection.
