FIB-milled plasmonic nanoapertures allow for long trapping times of individual proteins
Wayne Yang (TU Delft - BN/Cees Dekker Lab, Kavli institute of nanoscience Delft)
Madeleine van Dijk (TU Delft - Student Development, Kavli institute of nanoscience Delft)
Christian Primavera (Kavli institute of nanoscience Delft, Student TU Delft)
Cees Dekker (Kavli institute of nanoscience Delft, TU Delft - BN/Cees Dekker Lab)
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Abstract
We have developed a fabrication methodology for label-free optical trapping of individual nanobeads and proteins in inverted-bowtie-shaped plasmonic gold nanopores. Arrays of these nanoapertures can be reliably produced using focused ion beam (FIB) milling with gap sizes of 10–20 nm, single-nanometer variation, and with a remarkable stability that allows for repeated use. We employ an optical readout where the presence of the protein entering the trap is marked by an increase in the transmission of light through the nanoaperture from the shift of the plasmonic resonance. In addition, the optical trapping force of the plasmonic nanopores allows 20-nm polystyrene beads and proteins, such as beta-amylase and Heat Shock Protein (HSP90), to be trapped for very long times (approximately minutes). On demand, we can release the trapped molecule for another protein to be interrogated. Our work opens up new routes to acquire information on the conformation and dynamics of individual proteins.
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