Preparation and evaluation of temperature and magnetic dual-responsive molecularly imprinted polymers for the specific enrichment of formononetin

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.

Molecularly Imprinted Polymers for Dispersive (Micro)Solid Phase Extraction: A Review

The review describes the development of batch solid phase extraction procedures based on dispersive (micro)solid phase extraction with molecularly imprinted polymers (MIPs) and magnetic MIPs (MMIPs). Advantages and disadvantages of the various MIPs for dispersive solid phase extraction and dispersive (micro)solid phase extraction are discussed. In addition, an effort has also been made to condense the information regarding MMIPs since there are a great variety of supports (magnetite and magnetite composites with carbon nanotubes, graphene oxide, or organic metal framework) and magnetite surface functionalization mechanisms for enhancing MIP synthesis, including reversible addition-fragmentation chain-transfer (RAFT) polymerization. Finally, drawbacks and future prospects for improving molecularly imprinted (micro)solid phase extraction (MIMSPE) are also appraised.

Formononetin protects against cisplatin‑induced acute kidney injury through activation of the PPARα/Nrf2/HO‑1/NQO1 pathway

Acute kidney injury (AKI) is characterized by an abrupt deterioration of renal function. Formononetin (FOR) protects against cisplatin (CIS)‑induced AKI, and it has various potential pharmacological and biological effects, including anti‑inflammatory, antioxidative and anti‑apoptotic effects. The current study investigated the role of FOR in CIS‑induced AKI. Rats were treated with CIS to establish an AKI model, followed by treatment with FOR. HK‑2 cells were treated with CIS, FOR, GW6471 [a peroxisome proliferator‑activated receptor α (PPARα) antagonist], eupatilin (a PPARα agonist) and nuclear factor erythroid 2‑related factor 2 (Nrf2) small interfering RNA (siNrf2), and cell proliferation and apoptosis were determined by MTT and flow cytometry assays. The mRNA and proteins levels of PPARα, Nrf2, heme oxygenase‑1 (HO‑1) and NAD(P)H quinone dehydrogenase 1 (NQO1) were measured by reverse transcription‑quantitative PCR and western blotting. The results demonstrated that FOR attenuated the histopathological changes, the levels of blood urea nitrogen, creatinine, TNF‑α and IL‑1β, and the MDA content and MPO activity, whereas it enhanced CAT activity in the AKI rat model. Furthermore, FOR and eupatilin promoted cell viability and CAT activity, and increased the levels of PPARα, Nrf2 and HO‑1 and NQO1, but suppressed apoptosis and MPO activity, and reduced the levels of MDA, TNF‑α and IL‑1β in CIS‑treated HK‑2 cells. Notably, the aforementioned effects were reversed by GW6471 treatment or siNrf2 transfection. In conclusion, FOR protects against CIS‑induced AKI via activation of the PPARα/Nrf2/HO‑1/NQO1 pathway.

Extraction of activated epimedium glycosides in vivo and in vitro by using bifunctional-monomer chitosan magnetic molecularly imprinted polymers and identification by UPLC-Q-TOF-MS

In this work, efficient, sensitive bifunctional-monomer chitosan magnetic molecularly imprinted polymers (BCMMIPs) were fabricated and successfully applied to concentrate the metabolites of Epimedium flavonoids in rat testis and bone that were later analyzed using UPLC-Q-TOF-MS. Using chitosan and methacrylic acid as co-functional monomers, BCMMIPs exhibited a large adsorption capacity (7.60 mg/g), fast kinetics (60 min), and good selectivity. Chitosan is bio-compatible and non-toxic, and methacrylic acid provides multiple hydrogen bond donors. The BCMMIPs were injected into rat testis to specifically enrich the total flavonoid metabolites in vivo and were used to extract metabolites from bone in vitro. The results showed that the BCMMIPs coupled with UPLC-Q-TOF-MS successfully identified 28 compounds from testis and 18 compounds from bone, including 19 new compounds. This study provided a reliable protocol for the concentration of metabolites from complex biological samples, and several new metabolites of Epimedium flavonoids were found in vivo and in vitro.

Specific adsorption of tetracycline from milk by using biocompatible magnetic molecular imprinting material and evaluation by ECD

Biocompatible magnetic molecularly imprinted polymers (BMMIPs) were prepared with Zein for the first time, and were used to enrich tetracycline compounds selectively. Innovative combination of BMMIPs and electrochemistry to obtain lower detection line to satisfy industrial detection demands. Using Zein as the crosslinking agent, the polymers were synthesized on the surface of Fe₃O₄ particles. The scanning electron microscope, transmission electron microscope and X-ray diffraction technologies were used to characterize BMMIPs. Through optimization, BMMIPs attained large adsorption capacity (236.40 mg/g) with fast kinetics (40 min) and followed the Langmuir isotherm and pseudo-second-order kinetic models. BMMIPs had good recognition ability, the selective factors of oxytetracycline, chlortetracycline, doxycycline were 4.78, 4.23, and 3.39, respectively. Excellent linearity was attained in the range of 0.025-500 μg/mL, with low detection limits and low quantitation limits of 0.025 and 0.083 μg/mL. According to our exploring, BMMIPs was ideal materials for enrichment of tetracycline in complex biological samples.

Rapid measurements of curcumin from complex samples coupled with magnetic biocompatibility molecularly imprinted polymer using electrochemical detection

Curcumin widely exists in food, and rapid selective and accurate detection of curcumin have great significance in chemical industry. In this experiment, a new magnetic biocompatibility molecularly imprinted polymer was prepared with nontoxic and biocompatible Zein to adsorb curcumin selectively. The polymer has high biocompatibility, good adsorption capacity, and specific adsorption for curcumin. Combined with portable electrochemical workstations, the polymer can be used to detect curcumin rapidly and cost-effectively. Using curcumin as a template and Zein as the crosslinking agent, the polymers were synthesized on the surface of Fe₃ O₄ particles for solid phase extraction. The experimental results showed that the polymer reached large adsorption capacity (32.12 mg/g) with fast kinetics (20 min). The adsorption characteristic of the polymer followed the Langmuir isotherm and pseudo-second-order kinetic models. Hexacyanoferrate was used as electrochemical probe to generate signals, and the linear range was 5-200 µg/mL for measuring curcumin. The experimental analysis showed that the polymer was an ideal material for selective accumulation of curcumin from complex samples. This approach has been successfully applied to the determination of curcumin in food samples with electrochemical detection, indicating that this is a feasible and practical technique.

Surface molecularly imprinted polymers prepared by two-step precipitation polymerization for the selective extraction of oleanolic acid from grape pomace extract

Surface molecularly imprinted polymers were successfully prepared by a novel two-step precipitation polymerization method. The first-step allowed the formation of 4-vinylpyridine divinylbenzene and trimethylolpropane trimethacrylate copolymeric microspheres. In the second-step precipitation polymerization, microspheres were modified with a molecularly imprinting layer of oleanolic acid as template, methacrylic acid as functional monomer, and divinylbenzene/ethylene glycol dimethacrylate as cross-linker. The obtained polymers had an average diameter of 4.43 μm and a polydispersity index of 1.011; adsorption equilibrium was achieved within 40 min, with adsorption capacity reaching 27.4 mg/g. Subsequently, the polymers were successfully applied as the adsorbents of molecularly imprinted solid-phase extraction to separate and purify the oleanolic acid from grape pomace. The content of oleanolic acid in the grape pomace extract was enhanced from 13.4 to 93.2% after using the molecularly imprinted solid-phase extraction process. This work provides an efficient way for effective oleanolic acid separation and enrichment from complex matrices, which is especially valuable in industrial production.