Polymer brush functionalised nanopore sensors

Sammanfattning: Single-molecule studies on proteins could reveal a lot of information about their conformational dynamics, and processes such as misfolding and aggregation. This knowledge is valuable in providing a deeper understanding of molecular biology, and for understanding the link between proteins and various diseases. Traditional averaging methods are unable to capture the dynamic behaviour and identify rare states within the protein population. However, conducting single molecule measurements on proteins presents inherent challenges, for instance limited observation time of the protein or, in an attempt to extend observation time, the tethering of proteins to a surface, potentially disturbing their delicate three-dimensional structure. This thesis works towards the goal of developing a platform for long-term, non-intrusive single-molecule measurements on proteins. This is done by the integration of ionic current nanopore sensing with functional nanostructures. A novel nanochamber was fabricated through a combination of electron beam lithography, wet etching and controlled breakdown. This nanochamber, consisting of a cavity connected to two nanopores, is designed for protein trapping, where the nanopores would act as “gates”. Thus, the concept of macromolecular gating becomes central in protein trapping. The thesis demonstrates thermo-responsive gating for proteins using PNIPAM functionalised nanopore arrays, as well as voltage-gating for both DNA and proteins with a PEG-functionalised single nanopore sensor. The utilisation of a voltage-gated nanopore allows for ion current readout, confirming molecular translocation through the pore. To facilitate nanopore sensing at higher voltages beyond the gating threshold, a Fourier transform-based algorithm for ion current data filtering has been developed.