Rapid Prototyping of Electrochemical DNA Detection Sensors
Authors: Woo Stephen , Gabardo Christine , Soleymani Leyla 
Published: February 2020

Molecular diagnostic technologies can greatly improve the management of infectious diseases by offering reduced infection to detection window periods, rapid sample-to-answer times, and strain-specific pathogen identification1. In spite of great promise, these technologies have not made the predicted impact in resource poor regions with a high infectious disease burden. Handheld and chip-based nucleic acid detection systems are simple and inexpensive solutions that are envisioned to highly impact the diagnostic needs of these areas; however, their translation from the research lab to the marketplace has often been a lengthy process. To overcome this hurdle, we have developed a rapid prototyping method for fabricating integrated biosensing and sample preparation devices in a matter of hours.
The fabrication method is focused on using multiple benchtop processes for creating hierarchical materials that are tunable in multiple lengthscales. Tunability in macroscale is achieved by using a CAD-driven craft cutter to create a shadow mask on a self-adhesive vinyl layer immobilized on a shrinkable polymer substrate. Gold thin films are deposited on the electrode by sputtering, and the gold-modified polymer substrate is heated in order to induce micro/nanostructuring on the gold substrate by shrinking the underlying substrate. For the purpose of DNA detection, these wrinkled gold electrodes are modified with a self-assembled monolayer of thiolated DNA probes, which is used for capturing specific DNA targets.
In this work, we used the newly developed rapid prototyping method to create a multiplexed electrochemical DNA detection sensor. Through electrochemical measurements we demonstrated the surface area of these wrinkled electrodes to be six times larger than the surface area of planar electrodes of the same footprint. This allows more probe molecules to be immobilized on wrinkled electrodes compared to planar electrodes as indicated by fluorescence measurements. Furthermore, we combined these probe modified wrinkled electrodes with an electrocatalytic reporter system2, and successfully demonstrated that large signal changes (~100 % increase) are achieved when complementary targets are introduced, while negligible signal changes are observed in case of non-complementary targets. In addition, wrinkled electrodes transduce larger signal changes when compared to their planar electrode counterparts.
In summary, we have developed a rapid prototyping method that is ideal for developing multi-scale electrodes for biosensing applications. In this work, we have demonstrated its application to electrochemical DNA sensing; however, this method can be used for creating systems that integrate sensing devices with sample preparation devices including bacterial lysis and magnetic separation 3components.
(1) Gallarda, J.; Dragon, E. Blood Screening by Nucleic Acid Amplification Technology: Current Issues, Future Challenges. Mol. Diagnosis
2000, 5.
(2) Lapierre, M. A.; Keefe, M. O.; Taft, B. J.; Kelley, S. O.; Merkert, E. F.; College, B.; Hill, C. Electrocatalytic Detection of Pathogenic DNA Sequences and Antibiotic Resistance Markers. 2003, 75, 6327–6333.
(3) Hosseini, a.; Soleymani, L. Benchtop Fabrication of Multi-Scale Micro-Electromagnets for Capturing Magnetic Particles. Appl. Phys. Lett.
2014, 105, 074102.

Figure 1