2-photon-fabricated nano-fluidic traps for extended detection of single macromolecules and colloids in solution

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 timescales for single molecules in solution without immobilising 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-timescale analysis of single biomacromolecules and nanoscale colloids in solution. We use two-photon-based hybrid lithography in conjunction with soft lithography to fabricate nanofluidic devices with nano-trapping geometries down to 100 nm in height. We provide a rigorous description and characterisation of the fabrication route that enables the writing of nanoscopic 3D structures directly in photoresist and allows for the integration of nano-trapping and nano-channel geometries within micro-channel devices. Using confocal fluorescence burst detection, we validated the functionality of particle confinement in our nano-trap geometries through measurement of particle residence times. All species under study, including nanoscale colloids, α-synuclein oligomers, and double-stranded DNA, showed a three to five-fold increase in average residence time in the detection volume of nano-traps, due to the additional local steric confinement, in comparison to free space diffusion in a nearby micro-channel. Our approach thus opens-up the possibility for single-molecule studies at prolonged observational timescales to analyse and detect nanoparticles and protein assemblies in solution without the need for surface immobilisation.

Toward nanofluidics‐based mass spectrometry for exploring the unknown complex and heterogeneous subcellular worlds

“…They developed an approach to fabricate nanofluidic devices with nanotrapping geometries down to 100 nm in height, thus, enabling the confinement of biomacromolecules and colloids with specificity to some extent. 29 For mass spectrometry, the separation of complex samples prior to analysis is important to improve both sensitivity and specificity. In particular, target analytes are present in complex biological samples.…”

“…Nanofluidics is the study and application of fluids confined within nanostructures. [20][21][22][23][24]41 With the advancement of nanofab-rication over the past two decades, [25][26][27][28][29][30][31][32][33]34,35 nanostructures with various nanofluidic geometries such as nanopipettes, nanotubes, nanopores, and nanochannels have been fabricated, resulting in diverse abilities and great potential for a variety of applications. In particular, the use of these nanofluidic geometries allows the precise handling of fluid samples with ultrasmall volumes ranging from picoliter to zeptoliter (10 −21 L, zl) order.…”

Single-molecule sizing through nano-cavity confinement

“…We made use of a nano-fluidic device, previously developed in our laboratory, to measure particle residence times within nano-cavities. 26,27 A schematic of the fluidic platform is shown in Figure 3a, upper panel. The device consists of arrays of nano-cavities which are connected to nanofluidic channels.…”