This work presents a facile method of fabricating paper-based nano biosensors using conductive ink composed of graphene nanoflakes (GNF) and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) conductive polymer for the detection of cytokines. Cytokines, a class of regulatory proteins, are important physiological and pathological markers for prognosis and diagnosis of diseases like cancer and Alzheimer’s, as well as for monitoring the response to injury. Tumor necrosis factor (TNF)-α (17.5 kDa), a pro-inflammatory cytokine, ranges from 10 pg/mL in healthy human serum, to \~300 pg/mL in patients with autoimmune disease \[1\]. Even though single layer graphene-based nano biosensors have been able to detect cytokines down at the pg/mL level, their fabrication is expensive. Here, using dip coating with our conductive ink and commercial paper substrates (e.g. Whatman® filter paper), we measured TNF-α from 0.8-800 pg/mL using electrochemical impedance spectroscopy based immunosensing in the frequency range of 10 kHz to 100 mHz. We improved the viscosity and stability of the conductive ink through adjusting the ratio of GNF and PEDOT-PSS in solvent. Additionally, we achieved proper mixing of the ink components by using a FlackTek® speedmixer. During this mixing process, GNF can curl up, and additionally get doped with PEDOT-PSS through π-π interactions, thereby increasing the charge carrier mobility of GNF and hence sensitivity for biosensing \[2,3\]. Moreover, we investigated paper-based substrates (Whatman® and Fabriano®) with different porosity and wettability to obtain flexible sensors with stable conductive films. Our results show that Whatman® filter paper with larger porosity than Fabriano® paper provides stable conductive film by providing pathways to connect top and bottom conductive layers through the open pores. We coated paper-based substrates multiple times to improve the stability of the coated film and control the channels for ion conduction in the nano biosensor. Using brief atmospheric plasma-based dry oxidation, we increased the number of active sites on the sensor surface for TNF-α antibody attachment via EDC-NHS chemistry. To determine the presence and distribution of GNF and PEDOT-PSS, we characterized sensor substrates by scanning electron microscopy and Raman spectroscopy. This research paves the way towards economically viable and flexible paper-based biosensors using techniques like screen printing for sensitive detection of cytokines.

 

References:

\[1\] E. B. Aydın, M. Aydın, and M. K. Sezgintürk, “A highly sensitive immunosensor based on ITO thin films covered by a new semi-conductive conjugated polymer for the determination of TNFα in human saliva and serum samples,” Biosens. Bioelectron., vol. 97, pp. 169–176, Nov. 2017, doi: 10.1016/j.bios.2017.05.056.

\[2\] Liu, Wei, Vijesh A. Tanna, Benjamin M. Yavitt, Christos Dimitrakopoulos, and H. Henning Winter. "Fast production of high-quality graphene via sequential liquid exfoliation." ACS applied materials & interfaces 7, no. 49 (2015): 27027-27030.

\[3\] Chen, Qianli, Fatemeh Zabihi, and Morteza Eslamian. "Improved functionality of PEDOT: PSS thin films via graphene doping, fabricated by ultrasonic substrate vibration-assisted spray coating." Synthetic Metals 222 (2016): 309-317.


Graphene-Conductive, Polymer-Coated, Paper-Based Nano Biosensor for Cytokine Detection

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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