Bionanoelectronics Platform with DNA Molecular Wires Attached to High Aspect-Ratio 3D Metal Microelectrodes

Abstract

In this study, the investigation of attachment of DNA molecular wires and ropes to high aspect-ratio three-dimensional (3D) metal microelectrodes and their subsequent electrical characterization as part of a bionanoelectronics platform is reported. The 3-D microelectrode architecture consists of mainly high aspect-ratio microelectrode structures (75 μm height and above) patterned from relatively thick layers of negative tone photoresist and covered by sputtered gold on their top surface. DNA attachments on 3-D microelectrode structures was demonstrated using oligonucleotide-DNA self-assembly and thiol-gold covalent bonding. Further, DC and AC electrical characterization of double-stranded λ-DNA molecular wires in a dry environment and suspended between high aspect-ratio 3D microelectrodes 75 μm away from the substrate (to heights unprecedented so far in the literature which thereby eliminate interference of substrate) is presented. Electrical characterizations based on I-V and AC impedance analysis of several repeatable data points of attachment with varying λ-DNA concentration (500 ng/μL to 1.5 ng/μL) showed measurable and significant conductivity of λ-DNA molecular wires with some band-gap; thereby establishing it as semi-conductor at low-frequencies (<100 Hz) and a very good conductor at high-frequencies (∼1 MHz). We believe that the research presented here represents a significant departure from previous studies and makes unique contributions through (i) more accurate direct conductivity measurement of DNA molecular wires facilitated by suspension of the DNA away from the substrate, and (ii) AC impedance measurement of DNA molecular wires in dry-state attachment (relevant for long-term viability studies) that suggest metal-type low impedance at high-frequencies. The significant conductivity of λ-DNA molecular wires (similar to metals) observed at high-frequencies (|Z| < 5 KΩ) opens up substantial opportunities.

Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity

“…Glassy carbon (GC) is a very attractive material for use in neural interfaces as it has been demonstrated to have good electrical properties, to be chemically inert and electrochemically stable, and amenable to being fabricated into a variety of geometries25262728293031. However, only recently has GC been considered for such a use, mainly due to new enabling technologies that allow for pattern transfer and the integration of GC electrodes into thin-film polymeric substrates192021.…”

AC electrical characterisation and insight to charge transfer mechanisms in DNA molecular wires through temperature and UV effects

“…Lithography of microelectrodes, that form component of the bionanoelectronics chip shown in Fig. 2, consists of the traditional negative photolithography processes [21,[35][36][37].…”

“…Electrical resistance measurements were performed on the microelectrode structures where l-DNA was successfully attached. The AC electrical characterisations of the DNA molecular wire were carried out in a dry environment after washing the chip with DI water [21]. Typically, about 2-3 hours are needed before stable measurements can be recorded.…”

“…Therefore we believe that there is unmet research need for three key aspects: namely, (i) AC conductivity in DNA molecular wires with particular focus on role of frequency, (ii) understanding how long‐term and external effects and parameters such temperature, UV irradiation, electric field and frequency of current source affect electrical conductivity of DNA molecular wires and (iii) testing validity of the leading CT theories – especially in AC – through not only direct measurement methods, which are very difficult and imprecise, but also through repeatable indirect methods. In a previous paper, we had demonstrated attachment of DNA molecular wires and ropes to high aspect‐ratio three‐dimensional (3D) metal microelectrodes and their subsequent electrical characterisation as part of a bionanoelectronics platform [21]. In this research, we extend the work to investigation of AC conductivity under long‐term effects such as UV irradiation and temperature, and we report on sets of experiments that orthogonalise the different competing parameters that could influence experimental findings in electrical conductivity of DNA molecular wires.…”

Dependence of Shape and Geometry of Microelectrodes in Manipulating Polarizable Particles like DNA through Electro-kinetic Effects

“…Moreover the triangular shape of the electrode facilitated the chance of a single molecule being bridged between the electrodes. Recently, Vahidi 25 , et al confirmed that triangular metal electrodes were the most suitable form of electrode configuration which would result in attachment of DNA molecules at the electrodes with high aspect ratio. Figure 7 shows SEM images of λ-DNA being bridged between two metal electrodes.…”