Esculetin-tailored molecularly imprinted polymer for selective enrichment of Esculetin in complex herbal matrices

Iniferter-mediated surface imprinting precisely controls uniform 13 nm polymer shells. • Ultrahigh adsorption capacity of 70.92 mg/g, over threefold higher than reported MIPs. • 4-VP functional monomer ensures high selectivity via hydrogen bonding (IF = 2.08). • Rapid adsorption reaches equilibrium within 2 h, following pseudo-second-order kinetics. • Excellent reusability, retaining 85.9% capacity after five adsorption-desorption cycles. As a coumarin compound with important biological activity, esculetin (ESC) is widely found in complex matrices such as herbal medicines. Due to its low content and severe matrix interference, efficient and highly selective enrichment is essential prior to analytical detection and practical application. In this study, surface molecularly imprinted nanomicrospheres (SMIMs), a type of molecularly imprinted polymer (MIP) with specific recognition ability for ESC, were successfully prepared based on surface molecular imprinting technology combined with initiation–transfer–termination polymerization, using ESC as the template molecule, 4-vinylpyridine (4-VP) as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent. The morphology, structure, and properties of the polymers were systematically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) surface area analysis. The results showed that the prepared imprinted polymers were spherical nanoparticles with uniform particle size, good dispersion, and well-developed surface pores. The adsorption experiments showed that the adsorption capacity of the SMIMs for ESC was significantly higher than that of the non-imprinted polymers (NIMs). The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity reached 70.92 mg/g at 298 K, indicating excellent specific recognition performance. Analysis of real samples demonstrated that SMIMs can be successfully applied for the selective enrichment of esculetin in Herba Lysimachiae, with its content significantly increasing from 247.37 μg/kg to 645.96 μg/kg. The analytical method exhibited high accuracy (recoveries of 92.15%–104.21%) and good reproducibility (RSD < 5.0%). More importantly, the near-100% matrix effect (97.05%–104.24%) demonstrates the excellent anti-interference capability of the material when dealing with complex natural product matrices, thereby ensuring the reliability of the analytical results. This study provides new materials and methodological support for the specific enrichment and highly sensitive detection of trace bioactive components in herbs. Download: Download high-res image (123KB) Download: Download full-size image