Elsevier

Analytica Chimica Acta

Volume 1146, 15 February 2021, Pages 155-165
Analytica Chimica Acta

Layer-by-layer assembly strategy for fabrication of polydopamine-polyethyleneimine hybrid modified fibers and their application to solid-phase microextraction of bioactive molecules from medicinal plant samples followed by surface plasmon resonance biosensor validation

https://doi.org/10.1016/j.aca.2020.11.016Get rights and content

Highlights

  • A new PVDF@polydopamine@polyethyleneimine@xanthine oxidase fiber was fabricated.

  • The fabricated fibers exhibited highly desired extraction performance.

  • The fabricated fibers were applied to real medicinal plants samples.

Abstract

A solid-phase microextraction method is introduced to overcome limitations of classical phytochemical pattern of identifying bioactive compounds, including tedious and time-consuming separation and purification step and consumption of large amounts of organic solvents, which was non-environmentally- friendly. In this proposed method for solid-phase microextraction, polyvinylidene fluoride fibers@polydopamine@polyethyleneimine@receptor as a solid part of the extractors were pushed into sample solution of medicinal plants, and the procedure was followed by stirring and easily dissociation of receptor binding ligands in organic solvent through pulling out of the functionalized fibers. Xanthine oxidase was chosen as the model receptor, while isoacteoside was selected as the model inhibitor. Several effecting parameters were optimized by experimental design, including temperature, ion strength and pH. Nine bioactive components were obtained from extract of Plantago depressa by using the established solid-phase micro-extraction method. The limit of detection and limit of quantification of the nine components ranged from 0.0008 to 0.03 mg mL−1 and from 0.001 to 0.016 mg mL−1, respectively. The RSD values of intra-day and inter-day precisions ranged from 0.24% to 2.19% and 0.62%–2.84%, respectively. The average recoveries of the nine components were from 95.06 to 104.03% with relative standard deviation (RSD) values from 1.02 to 2.90% for Plantago depressa. The RSD values of stability of the nine components ranged from 1.36% to 2.74%, which satisfied the requirements of an analytical method. In addition, surface plasmon resonance biosensor was utilized to corroborate the binding affinity between these compounds and receptor. The avidity values of these ligands corresponded well with their IC50 values. The results confirmed that polydopamine and polyethyleneimine hybrid modified polyvinylidene fluoride fibers based solid-phase microextraction method was successfully utilized for locating bioactive compounds of medicinal plants.

Introduction

Traditional phytochemical pattern of identifying bioactive compounds, which consists of tedious separation and purification steps, consumes several months of time and yields a lot of organic wastewater, cannot meet the green and environmentally-friendly requirements of pharmaceutical industry in the new stage [1]. Thus, solid-phase microextraction (SPME) is introduced due to the reduced operation times and low reagent consumptions. SPME has been applied in various analytical fields such as environmental [[2], [3], [4]] and food analysis [5], bioanalysis [6], etc. Among them, affinity SPME is more interesting to us [7,8]. For affinity SPME, the receptor or antibody are immobilized onto the surface of a modified fiber or capillaries. Reactive groups of receptor or antibody form linkages with the solid support. The receptor–ligand or antibody-antigen interaction is specific, which leads to the extraction of the desired compounds from the sample.

In the current, a plethora of modifications to the SPME technique were developed to adapt the SPME procedure to receptors. For instance, polydopamine (PDA) has received more and more attention as it exhibits a strong adhesive property to many materials through spontaneous oxidative self-polymerization [9]. PDA layer could be utilized for secondary immobilization reactions since it contains functional groups which can be fabricated with various biomolecules, such as proteins, and enzymes etc. via Michael addition or Schiff base formation. Thus, PDA was widely used for the biomimetic surface modification. Polyethylenimine (PEI) is a cationic polymer, which contains the amine group and two carbon aliphatic CH2CH2 spacers [10]. The negatively charged receptors will be easily bound to fibers coated with PEI.

Herein, as a showcase, we proposed the layer-by-layer assembly strategy for preparing PVDF fibers@PDA@PEI@receptors for efficient SPME of xanthine oxidase (XOD) binding ligands from medicinal plant samples. The schematic of fabrication of the functionalized PVDF fibers for SPME of XOD inhibitors (XOIs) from herbal mixtures is present in Fig. 1. XOIs are typically used for treating nephropathy and renal stone diseases linked to hyperuricemia. In addition, in order to cross-validate the results, surface plasmon resonance biosensor (SPR) [11,12] are utilized for probing the interaction between XOD and ligands. Avidity value (pD2) of these ligands are calculated and plotted against their IC50 values.

Section snippets

Reagents

XOD (from bovine milk, EC:1.1.3.22), dopamine hydrochloride (DA), polyethyleneimine (PEI, 25 kDa), EDC, NHS and ethanolamine hydrochloride (ETA) were obtained from Sigma Co. Allopurinol was supplied by Aladdin Bio- Chem Technology Co. Anti-xanthine oxidase antibody (rabbit polyclonal) was purchased from Bioss Bio-technology Co. Polyvinylidene fluoride fibers (PVDF) were purchased from H-Filtration Membrance Technology & Engineering Co. The rhizome of Plantago depressa was obtained from Qingyang

Characterization of PVDF@PDA@PEI@XOD fibers by using SEM

The morphology of the PVDF fibers, PVDF@PDA fibers, PVDF@PDA@PEI fibers, PVDF@PDA@PEI@XOD fibers were characterized by using SEM. The front and vertical picture of PVDF fibers are present in Fig. 2a–b. The inner diameter and outer diameter of PVDF fibers were measured as 0.9 mm and 1.2 mm, respectively. As is shown in Fig. 2c–f, different surface structures were observed for the fabricated PVDF fibers at different stages, which were different from the smooth surface of PVDF fibers. SEM image in

Conclusion

In this work, the XOD functionalized PVDF fibers was fabricated by using layer-by-layer assembly strategy. Under the optimized conditions, PVDF @PDA@PEI@XOD fibers with high extraction efficiency for isoaceoside was obtained, which was then applied to extract XOD binding ligands from crude extract of Plantago depressa samples prior to UHPLC-Q-TOF-MS analysis. The developed SPME method showed good performance. It should be noticed that seven new XOD inhibitors were identified by using the SPME

CRediT authorship contribution statement

Yi Tao: Conceptualization, Methodology, Supervision, Writing - review & editing. Lin Chen: Data curation, Visualization, Investigation, Writing - original draft. Enci Jiang: Software, Validation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This study was supported by the National Natural Science Foundation of China (No.81703701) and Natural Science Foundation of Zhejiang Province (No.LY21H280008). The authors would like to thank the anonymous reviewers for their invaluable suggestions that helped improve the manuscript.

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