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. 2016;1(2):197-202.
doi: 10.1021/acssensors.5b00156. Epub 2015 Dec 17.

Electrochemiluminescence at Bare and DNA-Coated Graphite Electrodes in 3D-Printed Fluidic Devices

Gregory W Bishop  1 , Jennifer E Satterwhite-Warden  1 , Itti Bist  1 , Eric Chen  1 , James F Rusling  2
Affiliations

Electrochemiluminescence at Bare and DNA-Coated Graphite Electrodes in 3D-Printed Fluidic Devices

Gregory W Bishop et al. ACS Sens. 2016.

Abstract

Clear plastic fluidic devices with ports for incorporating electrodes to enable electrochemiluminescence (ECL) measurements were prepared using a low-cost, desktop three-dimensional (3D) printer based on stereolithography. Electrodes consisted of 0.5 mm pencil graphite rods and 0.5 mm silver wires inserted into commercially available 1/4 in.-28 threaded fittings. A bioimaging system equipped with a CCD camera was used to measure ECL generated at electrodes and small arrays using 0.2 M phosphate buffer solutions containing tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate ([Ru(bpy)3]2+) with 100 mM tri-n-propylamine (TPA) as the coreactant. ECL signals produced at pencil graphite working electrodes were linear with respect to [Ru(bpy)3]2+ concentration for 9-900 μM [Ru(bpy)3]2+. The detection limit was found to be 7 μM using the CCD camera with exposure time set at 10 s. Electrode-to-electrode ECL signals varied by ±7.5%. Device performance was further evaluated using pencil graphite electrodes coated with multilayer poly(diallyldimethylammonium chloride) (PDDA)/DNA films. In these experiments, ECL resulted from the reaction of [Ru(bpy)3]3+ with guanines of DNA. ECL produced at these thin-film electrodes was linear with respect to [Ru(bpy)3]2+ concentration from 180 to 800 μM. These studies provide the first demonstration of ECL measurements obtained using a 3D-printed closed-channel fluidic device platform. The affordable, high-resolution 3D printer used in these studies enables easy, fast, and adaptable prototyping of fluidic devices capable of incorporating electrodes for measuring ECL.

Keywords: 3D-printed fluidics; DNA oxidation; biosensing; electrochemiluminescence; stereolithography.

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Conflict of interest statement

Notes

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
3D-printed fluidic device with incorporated electrodes. (A) Side view of device equipped with 1/4 in.-28 threaded nuts and tubing for inlet/outlet access to the fluidic channel and a threaded nut in the center through which Ag/AgCl reference and graphite working and counter electrodes are integrated into the channel. (B) Bottom view of device. (C) Close-up bottom view of channel depicting (from left to right) 0.5 mm diameter graphite working, Ag/AgCl reference, and graphite counter disk electrodes surrounded by white plastic insulator. Flow of solution is from left to right in C. Channels are filled with 0.1 mM methylene blue in 0.1 mM KCl for visualization.
Figure 2
Figure 2
Photographs of electrodes integrated in a 3D-printed channel for ECL measurements. (A) Image of 0.5 mm working and counter pencil graphite electrodes and 0.5 mm Ag/AgCl reference electrode positioned in channel taken with bioimaging system CCD camera. ECL emitted by 18 (B), 45 (C), 90 (D), 180 (E), and 450 (F) μM [Ru(bpy)3]2+ in 0.2 M phosphate buffer (pH 7.5) and 100 mM TPA. A potential of +0.95 V vs Ag/AgCl was applied to the working electrode, and the exposure time for ECL images was 10 s. Scale bar represents 3 mm.
Figure 3
Figure 3
Relationship between average ECL response and concentration of [Ru(bpy)3]2+ for a single graphite working electrode in a 3D-printed fluidic device filled with [Ru(bpy)3]2+ in 0.2 M phosphate buffer (pH 7.5) and 100 mM TPA. Error bars correspond to one standard deviation (n = 4). Standard deviation is <4%, making error bars smaller than data points at low concentrations of [Ru(bpy)3]2+.
Figure 4
Figure 4
ECL response from [Ru(bpy)3]2+ with (PDDA/DNA)3-coated pencil graphite electrodes in a 3D-printed fluidic channel. ECL emitted from oxidized guanine bases within the (PDDA/DNA)3-modified electrode upon exposure to 180 (A), 450 (B), and 800 (C) μM [Ru(bpy)3]2+. (D) Linear relationship between DNA and ECL response. Error bars correspond to one standard deviation (n = 3). Error bars are smaller than data points at low concentrations of [Ru(bpy)3]2+.
Figure 5
Figure 5
Photographs of electrode arrays incorporated into 3D-printed channel. (A) Bottom view of 0.5 mm Ag/AgCl reference, stainless steel ring counter, and three 0.5 mm pencil graphite working electrodes. (B) ECL response from electrode array in 180 μM [Ru(bpy)3]2+ in 0.2 M phosphate buffer with 100 mM TPA. Scale bars represent 3 mm.
Scheme 1
Scheme 1
Basic Steps Used to Prepare of 3D-Printed Fluidic Devices
See this image and copyright information in PMC

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