Bioengineering of Solution Processed Graphene for the Development of Ultrasensitive Flexible Biosensing Platform
Authors: Halder Arnab , Hemanth Suhith , Keller Stephan Sylvest , Ulstrup Jens , Chi Qijin 
Published: February 2020

Development of low-cost, flexible and ultrasensitive biosensing platforms for rapid detection of different human metabolites is of great importance for the healthcare, pharmaceuticals and biomedical diagnostics sectors. Synthesis of novel functionalized nanomaterials with high surface area is a key step in the fabrication of high flexible biosensing devices1. Flexible biosensors are one of the most promising next generation wearable self-monitoring devices, as material flexibility is very crucial to attach on a patient’s body part and maintaining the mechanical stability as well as the sensing responses2. In recent years, graphene based materials have invoked a new era for developing smart hybrid material based biosensors. Graphene could offer a perfect solution as an ideal signal transducer for the development of low-cost bioelectronics devices3.

Functionalization can transform graphene into a versatile platform for different electrochemical applications4,5. Based on biocompatible engineering functionalization of graphene oxide (GO), we have designed a flexible biosensing platform that can successfully detect various clinically important human metabolites. Herein, we describe a facile synthesis approach for novel electroactive polymer functionalized reduced graphene oxide (RGO) architecture for biosensing applications. A 3D network of highly branched polymer with free amine groups was used for this purpose. Firstly, the polymer helps for the reduction of GO to RGO and to achieve higher conductivity of the material. Secondly, the free amine groups in the polymer chains are available for the further functionalization with redox moieties. Finally, the polymer-functionalized graphene matrix can offer a biocompatible microenvironment for the accommodation of various enzymes for the development of enzyme-based biosensors. The analysis of XPS and FT-IR spectroscopies reveals the successful functionalization of graphene. Following the synthesis, the functionalized graphene matrix was loaded with different enzymes through electrostatic interaction and the enzyme loading are evaluated by UV-VIS spectroscopy. Furthermore, the enzyme-graphene nanohybrid matrix was converted to a printing ink and printed on a flexible PET substrate. The flexible integrated biosensing electrodes were tested electrochemically for biosensing applications for clinically important analytes such as glucose, cholesterol and uric acid.

The immobilized enzymes on this material retained their catalytic activity and indicated that the functionalized RGO based flexible integrated device can successfully mediate bioelectrocatalytic electron transfer for biosensing applications. This new flexible electroactive platform exhibits excellent stability, selectivity, reproducibility, and fast response time for biosensing purposes and can offer great promises for the fabrication of new low-cost integrated biosensing devices.

References

1. Turner, A. P. F. Biosensors: sense and sensibility. Chem. Soc. Rev.
42,3184–96 (2013).

2. Gao, W. et al. Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis. Nature
529,509–514 (2016).

3. Lee, H. et al. A graphene-based electrochemical device with thermoresponsive microneedles for diabetes monitoring and therapy. Nat. Nanotechnol.(2016). doi:10.1038/nnano.2016.38

4. Zhang, M., Hou, C., Halder, A., Ulstrup, J. & Chi, Q. Interlocked graphene–Prussian blue hybrid composites enable multifunctional electrochemical applications. Biosens. Bioelectron.1–8 (2016). doi:10.1016/j.bios.2016.02.044

5. Zhang, M., Halder, A., Hou, C., Ulstrup, J. & Chi, Q. Free-standing and flexible graphene papers as disposable non-enzymatic electrochemical sensors. Bioelectrochemistry
109,87–94 (2016).

Acknowledgements

A.H. & Q.C. acknowledge DFF-FTP grant (the Danish Research Council for Technology and Production Science) (Project No. 12-127447) for funding. This project is also supported by Poul V. Andersens Foundation Grant (Project No. 65716).

Figure 1