The present studies explored the possibility of immobilizing phosphocholine (PC) liposomes on the surface of graphene oxide (GO) which was pre-adsorbed with two kinds of enzymes, horseradish peroxidase and glucose oxidase. The transmission electron microscope images showed that the PC liposomes adsorbed onto the GO surface kept integrity. By using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-encapsulated liposomes, a one-step colorimetric assay for glucose was developed. In the presence of glucose, the GO nanocomposites catalyzed the cascade enzymatic reaction producing colorimetric signals directly. Under the optimal conditions, the GO nanocomposites produced linearly increased colorimetric signal with increased concentrations of glucose ranging from 50 to 500 μM. The detection limit was 33 μM. The GO nanocomposites also exhibited good selectivity for the detection of glucose and were able to detect glucose in human serum.

Preparation and application of graphene oxide nanocomposites loaded with enzymes and liposomes
    Abstract
        Graphical abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Equipment
        2.3 Preparation of liposomes
        2.4 Preparation of PBA-GOx and PBA-HRP
        2.5 Preparation of GO nanocomposites
        2.6 Colorimetric determination of glucose
    3 Results and discussions
        3.1 Preparation of GO-GHL nanocomposites
        3.2 Verify the mobilization of liposomes and enzymes on GO
        3.3 Feasibility of the one-step colorimetric detection of glucose
        3.4 Optimization of preparation conditions for the GO-GHL nanocomposites
        3.5 Optimization of experimental conditions for glucose detection
        3.6 Detection of glucose
        3.7 Detection of glucose in real samples
        3.8 Stability of the GO-GHL nanocomposite
    4 Conclusion
    Anchor 22
    Acknowledgements 
    References

• Yifan Yu(School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, People’s Republic of China)
• Ruyuan Wang(School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, People’s Republic of China)
• Meilin Li(School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, People’s Republic of China)
• Shanshan Li(School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, People’s Republic of China)
• Aiping Fan(School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, People’s Republic of China)