Nanoporous-Gold-Based Electrode Morphology Libraries for Investigating Structure–Property Relationships in Nucleic Acid Based Electrochemical Biosensors

Abstract

Nanoporous gold (np-Au) electrode coatings significantly enhance the performance of electrochemical nucleic acid biosensors because of their three-dimensional nanoscale network, high electrical conductivity, facile surface functionalization, and biocompatibility. Contrary to planar electrodes, the np-Au electrodes also exhibit sensitive detection in the presence of common biofouling media due to their porous structure. However, the pore size of the nanomatrix plays a critical role in dictating the extent of biomolecular capture and transport. Small pores perform better in the case of target detection in complex samples by filtering out the large nonspecific proteins. On the other hand, larger pores increase the accessibility of target nucleic acids in the nanoporous structure, enhancing the detection limits of the sensor at the expense of more interference from biofouling molecules. Here, we report a microfabricated np-Au multiple electrode array that displays a range of electrode morphologies on the same chip for identifying feature sizes that reduce the nonspecific adsorption of proteins but facilitate the permeation of target DNA molecules into the pores. We demonstrate the utility of the electrode morphology library in studying DNA functionalization and target detection in complex biological media with a special emphasis on revealing ranges of electrode morphologies that mutually enhance the limit of detection and biofouling resilience. We expect this technique to assist in the development of high-performance biosensors for point-of-care diagnostics and facilitate studies on the electrode structure-property relationships in potential applications ranging from neural electrodes to catalysts.

Inkjet-Printing of Nanoparticle Gold and Silver Ink on Cyclic Olefin Copolymer for DNA-Sensing Applications

“…This may be explained by the reduced accessibility of the pores for signal probes, which is possibly enhanced by electrostatic repulsion of the charged capture and signal probes. This assumption is supported by a study on pore-size restriction for hybridization [42], where pores appear to be accessible for functionalization with capture probes. Access of complementary DNA is strongly dependent on pore diameter and decreases for average pore diameters of about 65 nm.…”

“…The inkjet-printed structures of this work feature pore sizes in a comparable dimension and below (Figure 2b). Further work would be required to investigate whether an optimization of capture probe density, the use of neutral charge peptide nucleic acid probes [43] or the tuning of pore size e.g., by electrochemical coarsening [42] improves accessibility and hybridization efficiency.…”

Dealloying at High Homologous Temperature: Morphology Diagrams

“…Today electrochemical dealloying processes are used to design nanostructures for a variety of functions encompassing electrocatalysis [1][2][3] and biosensors [4][5][6][7] with additional applications being explored such as actuation [8][9][10][11] and structural composites. [12][13][14] To date, the targeted nanoscale morphologies include bi-continuous structures such as nanoporous gold (NPG) formed by a percolation dissolution mechanism [15][16][17][18] and so-called skin or core-shell nanoparticle structures, formed by a passivation-like process.…”

A review of microfabricated electrochemical biosensors for DNA detection

“…This makes the sensors more complex to manufacture, especially in a reproducible manner and despite many excellent results presented in literature with these nanostructured surfaces, only a few of these strategies are currently compatible with microfabrication processes. One example is the Şeker group, who used sputtering to deposit a mixed thin film of silver and gold before dealloying the silver in a nitric acid wet etch (Daggumati et al, 2015;Matharu et al, 2017). This resulted in a nanoporous thin film electrode, demonstrated in figure 3.…”