Nanoelectrode Arrays Fabricated by Thermal Nanoimprint Lithography for Biosensing Application

Abstract

Electrochemical sensors are devices capable of detecting molecules and biomolecules in solutions and determining the concentration through direct electrical measurements. These systems can be miniaturized to a size less than 1 µm through the creation of small-size arrays of nanoelectrodes (NEA), offering advantages in terms of increased sensitivity and compactness. In this work, we present the fabrication of an electrochemical platform based on an array of nanoelectrodes (NEA) and its possible use for the detection of antigens of interest. NEAs were fabricated by forming arrays of nanoholes on a thin film of polycarbonate (PC) deposited on boron-doped diamond (BDD) macroelectrodes by thermal nanoimprint lithography (TNIL), which demonstrated to be a highly reliable and reproducible process. As proof of principle, gliadin protein fragments were physisorbed on the polycarbonate surface of NEAs and detected by immuno-indirect assay using a secondary antibody labelled with horseradish peroxidase (HRP). This method allows a successful detection of gliadin, in the range of concentration of 0.5–10 μg/mL, by cyclic voltammetry taking advantage from the properties of NEAs to strongly suppress the capacitive background signal. We demonstrate that the characteristics of the TNIL technology in the fabrication of high-resolution nanostructures together with their low-cost production, may allow to scale up the production of NEAs-based electrochemical sensing platform to monitor biochemical molecules for both food and biomedical applications.

Graphene-Based Field-Effect Transistor for Ultrasensitive Immunosensing of SARS-CoV-2 Spike S1 Antigen

“…Furthermore, among top-down lithography, electron beam lithography (EBL) showed the ability to create synthetic surfaces with sub-50 nm spatial resolution and a well-defined control of the topographical features to decorate the electrode with high-resolution nanostructures. 40 Graphene-based FETs were fabricated by the conventional Scotch-tape exfoliation process on SiO 2 /Si substrate, followed by standard EBL and metallization with 5/50 nm Cr/Au. 41 − 43 The S1-Ab were raised in-house 15 and covalently conjugated with graphene, using carbodiimide chemistry.…”

“…The major advantage of this FET sensor over other published FET devices is that, here, in-housed generated Spike S1 antibodies were used for the sensing, which reduces the overall cost of sensor fabrication. Furthermore, among top-down lithography, electron beam lithography (EBL) showed the ability to create synthetic surfaces with sub-50 nm spatial resolution and a well-defined control of the topographical features to decorate the electrode with high-resolution nanostructures . Graphene-based FETs were fabricated by the conventional Scotch-tape exfoliation process on SiO 2 /Si substrate, followed by standard EBL and metallization with 5/50 nm Cr/Au. − The S1-Ab were raised in-house and covalently conjugated with graphene, using carbodiimide chemistry. , Interaction of S1-Ag with graphene-conjugated S1-Ab results in the redistribution of local doping, thus the change in resistance of graphene, which can rapidly be detected as an output as illustrated in Scheme .…”

Nanoimprinted arrays of glassy carbon nanoelectrodes for improved electrochemistry of enzymatic redox-mediators

“…The polycarbonate film was patterned by indenting the pillars in the PC, i.e., forcing the displacement of the polymer from the area of the pillars on the stamp during the NIL thermomechanical cycle. Details on the fabrication of the stamp are carefully described elsewhere [31] and summarized in Scheme S1 in Supplementary Material.…”

“…Arrays of nanoelectrodes were fabricated by NIL, applying to GC platelets the procedure described previously for BDD thin film electrodes [31]. Briefly, a polycarbonate film was spin-coated at 2000 rpm on a thick layer of GC prepared by pyrolysis of a polymeric photoresist.…”

“…In the NIL process, a specific nanostructured mold is used to indent the same nanostructures in a thin thermoplastic film deposited on a substrate while the latter is in a melt state, i.e., during a thermomechanical cycle. This method can be used to generate arrays of nanoholes which can act as slightly recessed nanoelectrodes [31], as schematized in Supplementary Material, Scheme S1. Polycarbonate was used by Tormen and co-workers as the polymeric layer on which the nanoholes were imprinted on BDD substrates.…”