Vanderpoorten O, Babar AN, Krainer G, Jacquat RPB, Challa PK, Peter Q, Toprakcioglu Z, Xu CK, Keyser UF, Baumberg JJ, Kaminski CF, Knowles TPJ. "Nanofluidic Traps by Two-Photon Fabrication for Extended Detection of Single Macromolecules and Colloids in Solution" ACS Appl. Nano Mater. 5(2), 1995-2005 (2022) DOI | summary
Abstract:
The analysis of nanoscopic species, such as proteins and colloidal assemblies, at the single-molecule level has become vital in many areas of fundamental and applied research. Approaches to increase the detection time scales for single molecules in solution without immobilizing them onto a substrate surface and applying external fields are much sought-after. Here, we present an easy-to-implement and versatile nanofluidics-based approach that enables increased observational-time scale analysis of nanoscopic material building blocks such as single biomacromolecules and nanoscale colloids in solution. We use two-photon-based hybrid lithography in conjunction with soft lithography to fabricate nanofluidic devices with nanotrapping geometries down to 100 nm in height. We provide a rigorous description and characterization of the fabrication route that enables the writing of nanoscopic 3D structures directly in photoresist and allows for the integration of nanotrapping and nanochannel geometries within microchannel devices. Using confocal fluorescence burst detection, we validated the functionality of particle confinement in our nanotrap geometries through measurement of particle residence times. All species under study, including nanoscale colloids, α-synuclein oligomers, and double-stranded DNA, showed a 3- to 5-fold increase in average residence time in the detection volume of nanotraps, due to the additional local steric confinement, in comparison to free space diffusion in a nearby microchannel. Our approach thus opens up the possibility for single-molecule studies at prolonged observational-time scales to analyze and detect functionalized nanoparticles and protein assemblies in solution without the need for surface immobilization.