Date Published: October 21, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Shuyao Huang, Jiating Zheng, Qian Yang, Guosheng Chen, Jianqiao Xu, Yong Shen, Yimin Zhang, Gangfeng Ouyang.
Although bile acids (BAs) have been suggested as important biomarkers for endocrine diseases, the identification and quantification of different BAs are still challenges due to their enormous species and wide range concentrations. Herein, a copolymer probe based on β‐cyclodextrin (β‐CD) is fabricated through a simple in‐mold photopolymerization for the selective extraction of BAs. Through the unique stereochemical affinity between BAs and the cavity of β‐CD, the custom probe shows superior enriching capacities to series BAs. Moreover, the outstanding extraction ability is proved to be consistent in various interfering conditions, including pH changing and the addition of complex matrix. Further comparison shows that the stereostructure of the nucleus of BAs plays a vital role during the formation of the β‐CD/BA complex, indicating the potential for efficient extraction of other BAs, including their structural analogues or some unknown ones. The developed probe is used for solid phase microextraction, and the limits of detection are lower than 0.075 ng mL−1 by coupling to high performance liquid chromatography‐tandem mass analysis. The results in this study highlight the potential for effective improvement of immediate detection and profiling of BAs in real samples, which will make a tremendous impact in the analytical field or clinical diagnosis.
Bile acids (BAs) are the amphipathic products of cholesterol metabolism in vertebrates,1 playing fundamental roles in physiological processes,2, 3 or acting as signaling molecules of systemic endocrine functions.3, 4 It has been suggested for long that changes of BAs levels could be linked to tumor formation5, 6 in different organs, such as the esophagus,7 stomach,8 and small intestine9 or liver injury.10 Herein, comprehensive profiling and quantification of BAs will be vital for the diagnostic, therapeutic, and prognostic management of the related diseases.
A novel PEG/β‐CD copolymer SPME probe was fabricated through a simple in‐mold photopolymerization method and utilized for extracting BAs in biofluids. Different from traditional separation methods based on polarity similarity, the developed probe showed extremely high extraction capacity to BAs because of the unique stereochemical selectivity between BAs and the cavity of β‐CD. Moreover, the high enrichment efficiency was proved to be free from the matrix interfering, including the pH changing, the competitive extraction by other endogenous molecules and the protein fouling, which is vital for direct extraction from the highly complex biofluid samples. Further comparison demonstrated that the stereostructure of the nucleus of BAs played the vital role during the formation of β‐CD/BA complex, indicating the potential for efficient extraction of unknown BAs or their structural analogues. It is believed to bring significant improvement to BAs identification by the developed method, which is of great importance in disease diagnosis, biomarker profiling, or metabolomics studies. As in vivo SPME has been well‐developed and widely applied in analyzing pharmaceuticals or endogenous substances,35, 36 in vivo detection or instant determination based on this method is expected to be realized in the future.
The Synthesis of Beta‐Cyclodextrin Methacrylate (β‐CD‐MA): Vinyl group was derived on β‐CD by a simple esterification reaction (Figure S1, Supporting Information). Β‐CD (5.67 g, 0.005 mol) was weighted and dissolved in dry dimethyl formamide (DMF, 30 mL) in a flask. Then methacrylic anhydride (7.70 g, 0.050 mol) was added and the mixture was stirred at 500 rpm for 12 h at 80 °C under reflux. After the reaction finished, residue was filtered and large amount of chloroform was poured into the filtrate. The precipitation was three times washed by acetone, then collected and dried in vacuum at 20 °C for 24 h. The product was stored at −20 °C to avoid oxidation until use.
The authors declare no conflict of interest.