Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells

Abstract

To circumvent the bottlenecks of non-flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil-water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm(-2) μM(-1), up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nM, and a wide linear range of 87 nM to 100 μM. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well-tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil-water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society.

Keywords: dopamine; graphene; living cells; platinum; sensors.

Figure 1

Schematic illustration of the fabrication of hybrid electrodes and their electrochemical sensing response towards DA released from living PC 12 cells.

Figure 2

(A, B) TEM images of a 2D assembled film of dendritic Pt NPs at low and high magnifications, respectively. (C) HRTEM image of a dendritic Pt NP.

Figure 3

A, B) Cross‐sectional SEM images of dendritic Pt NPs‐decorated rGO paper electrode at low and high magnifications, respectively. C) Top‐view SEM image of dendritic Pt NPs‐decorated rGO paper electrode. D) XRD patterns of rGO and Pt/rGO paper electrodes.

Figure 4

A) CV curves of the hybrid Pt/rGO paper electrode and a Pt foil electrode in 1 m H₂SO₄. Scan rate: 100 mV s⁻¹. The inset shows impedance plots of rGO and hybrid Pt/rGO paper electrodes in 0.1 m KCl containing 1.0 mm K₃Fe(CN)₆ and 1.0 mm K₄Fe(CN)₆. B) DPV curves of the hybrid electrode in blank bath solution and bath solution containing 0.15 mm AA, 0.003 mm DA, and 0.15 mm UA, showing the feasibility of selective detection.

Figure 5

A) DPV curves of rGO and Pt/rGO paper electrodes in PBS (0.1 m, pH 7.4) containing DA. B) CVs of the Pt/rGO paper electrode at different scan rates in PBS (0.1 m, pH 7.4) containing 10 μm DA. The inset shows the dependence of redox peak current density on the potential sweep rate. C) DPV responses to various concentrations of DA at the Pt/rGO paper electrode. The inset shows DPV curves at low concentrations of DA. It should be noted that not all of the curves at different concentrations are shown for the sake of clarity. D) Relationship between DPV current density and DA concentration. The inset shows the equivalent plot for low concentrations of DA.

Figure 6

A) Cell viability testing of the hybrid Pt/rGO paper working electrode after co‐culturing with PC 12 cells for several hours. B) DPV responses (from a to d) of the Pt/rGO paper electrode in a microplate well with cultured PC 12 cells in the presence of 0 mm (a), 35 mm (b), 85 mm (c), and 105 mm (d) K⁺ solution.