Low-Copy Number Protein Detection by Electrode Nanogap-Enabled Dielectrophoretic Trapping for Surface-Enhanced Raman Spectroscopy and Electronic Measurements

Abstract

We report a versatile analysis platform, based on a set of nanogap electrodes, for the manipulation and sensing of biomolecules, as demonstrated here for low-copy number protein detection. An array of Ti nanogap electrode with sub-10 nm gap size function as templates for alternating current dielectrophoresis-based molecular trapping, hot spots for surface-enhanced Raman spectroscopy as well as electronic measurements, and fluorescence imaging. During molecular trapping, recorded Raman spectra, conductance measurements across the nanogaps, and fluorescence imaging show unambiguously the presence and characteristics of the trapped proteins. Our platform opens up a simple way for multifunctional low-concentration heterogeneous sample analysis without the need for target preconcentration.

Sub‐5 nm Metal Nanogaps: Physical Properties, Fabrication Methods, and Device Applications

“…Highly efficient lab‐on‐a‐chip devices are possible because the electronic detection technology can be mass‐produced with high yield and then coupled to widely used spectroscopic instruments. Lesser‐Rojas et al developed a multifunctional real‐time characterization device that could measure the Raman spectra and conductance across nanogaps and simultaneously perform fluorescence imaging during protein molecule trapping . However, the reported bioelectronic signal simply indicated the appearance of a molecule.…”

Brownian Motion and Large Electric Polarizabilities Facilitate Dielectrophoretic Capture of Sub‐200 nm Gold Nanoparticles in Water

“…In addition to artificial sub‐micron nanoparticles, DEP has recently been applied to smaller biological nano‐objects: proteins, nucleic acids, and extracellular vesicles . In the case of proteins and nucleic acids, the required very high electric field gradients are achieved using sub‐micron and nanometer‐scale electrode gaps, that concentrate the electric field gradients in extremely small volumes.…”

“…[27] DEP is of interest for the development of lab-on-chip analysis methods, [28] and has been used to concentrate plasmonic particles for various modes of Raman spectroscopy. [27,29] In addition to artificial sub-micron nanoparticles, DEP has recently been applied to smaller biological nano-objects: proteins, [30][31][32][33][34] nucleic acids, [35,36] and extracellular vesicles. [37,38] In the case of proteins and nucleic acids, the required very high electric field gradients are achieved using sub-micron and nanometer-scale electrode gaps, that concentrate the electric field gradients in extremely small volumes.…”

Detection of total protein in milk using phosphomolybdic acid-mediated surface-enhanced Raman spectroscopy

“…Nanosubstrates with special ‘hot spots’ were also developed for protein determination . Lesser‐Rojas et al recently reported a method for low‐copy number protein determination in the ‘hot spot’ based on a set of nanogap electrodes . Nevertheless, all the aforementioned methods have complex procedures for the synthesis of nanosubstrates, which may restrict their application to simple and quick protein detection.…”

“…[25,26] Lesser-Rojas et al recently reported a method for low-copy number protein determination in the 'hot spot' based on a set of nanogap electrodes. [27] Nevertheless, all the aforementioned methods have complex procedures for the synthesis of nanosubstrates, which may restrict their application to simple and quick protein detection. Moreover, the specificity of those methods for target analytes also restricts their application to routine detection of total protein.…”