Preparation and evaluation of photo-responsive hollow SnO2 molecularly imprinted polymers for the selective recognition of kaempferol

Kaempferol Molecularly Imprinted Monolithic Columns Prepared by a Surface Imprinting Method and Their Applications to Direct Separation of Flavonoids From Ginkgo Leaves by Liquid Chromatography

In this study, kaempferol molecularly imprinted monolithic columns (MIMCs) featuring a homogeneous pore structure and high separation ability were successfully prepared by surface imprinting on silica monoliths. These columns were then used to separate flavonoids from the hydrolysate of Ginkgo leaves. The preparation process involved three simple steps: preparation of silica monoliths, functionalization of the silica surface, and polymerization of the imprinting system onto the silica surface. The resulting MIMCs exhibited a homogeneous pore structure, high surface area (>100 m2/g), high porosity (ca. 74%), and good permeability (3.0 - 3.9 × 10-15 m2). The chromatographic separation performance of the MIMCs prepared on amino-functionalized silica monoliths was significantly superior to those prepared on thiol and vinyl-functionalized silica monoliths. The MIMCs prepared on amino-functionalized silica monoliths (I.D. 4.6 × 20 mm) could nearly achieve baseline separation of four structurally similar flavonoids: genistein, kaempferol, isorhamnetin, and quercetin. In addition, these MIMCs exhibited excellent selectivity in the chromatographic separation of flavonoids from the hydrolysate of Ginkgo leaves. However, when used as SPE adsorbents, the MIMCs prepared on thiol and vinyl-functionalized silica monoliths were superior to those on amino-functionalized silica monoliths in terms of purification of flavonoids from the Ginkgo hydrolysate. This study may be of instructive significance to the facile preparation of MIMCs for the high-selectivity separation and analysis of target components in complex natural systems.

Stimuli-Responsive Molecularly Imprinted Polymers: Mechanism and Applications

Molecularly imprinted polymers (MIPs) are very suitable for extraction, drug delivery systems, and sensors due to their good selective adsorption ability, but the difficulty of eluting templates during synthesis and the limitation of application scenarios put higher demands on MIPs. Stimuli-responsive MIPs (SR-MIPs) can actively respond to changes in external conditions to realize various functions, which provides new ideas for the further development of MIPs. This paper reviews the multiple response modes of MIPs, including the common temperature, pH, photo, magnetic, redox-responsive and rare gas, biomolecule, ion, and solvent-responsive MIPs, and explains the mechanism, composition, and applications of such SR-MIPs. These SR-MIPs and the resulting dual/multiple-responsive MIPs have good selectivity, and controllability, and are very promising for isolation and extraction, targeted drug delivery, and electro-sensor.

Preparation and Application of Molecularly Imprinted Polymers for Flavonoids: Review and Perspective

The separation and detection of flavonoids from various natural products have attracted increasing attention in the field of natural product research and development. Depending on the high specificity of molecularly imprinted polymers (MIPs), MIPs are proposed as efficient adsorbents for the selective extraction and separation of flavonoids from complex samples. At present, a comprehensive review article to summarize the separation and purification of flavonoids using molecular imprinting, and the employment of MIP-based sensors for the detection of flavonoids is still lacking. Here, we reviewed the general preparation methods of MIPs towards flavonoids, including bulk polymerization, precipitation polymerization, surface imprinting and emulsion polymerization. Additionally, a variety of applications of MIPs towards flavonoids are summarized, such as the different forms of MIP-based solid phase extraction (SPE) for the separation of flavonoids, and the MIP-based sensors for the detection of flavonoids. Finally, we discussed the advantages and disadvantages of the current synthetic methods for preparing MIPs of flavonoids and prospected the approaches for detecting flavonoids in the future. The purpose of this review is to provide helpful suggestions for the novel preparation methods of MIPs for the extraction of flavonoids and emerging applications of MIPs for the detection of flavonoids from natural products and biological samples.