Single-molecule methods have been rapidly developing with the appealing prospect of
transforming conventional analytical techniques. The selective recognition of proteins and small molecules is a major motivation in developing single-molecule detection and diagnostic techniques. However, challenges remain especially in improving detection sensitivity,
selectivity and controlling molecular transport. This is compounded by the complexities in selectively detecting small molecules in biological fluids. In this thesis, we address these limitations by showing a direct fabrication method for an analytical sensor that integrates the advantages of nanopores, field-effect transistors (FET) and selective recognition of target
analytes, for simultaneous single-molecule detection and manipulation of DNA, proteins and small molecules such as neurotransmitters.
In the first part of this thesis, a controlled and easy fabrication method for nanopore field-effect transistors was developed in terms of electrodeposition, facilitating the implementation of fabricated analytical sensors for the gating of molecular transport. It was demonstrated that
the perfect alignment of nanopore and FET enables the gating of molecular transport across nanopore to be switched on/off in real-time. More importantly, surface functionalization of the gate electrode can be used to fine-tune transport properties enabling more active control
over translocation velocity and capture rates by orders of magnitude.
Based on the established sensing platform, a novel sensing strategy was presented for selective sensing of proteins and neurotransmitters at the single-molecule level. Aptamers were attached to the surface of the gate electrode for selectively recognizing different analytes. Our
results elucidated that, protein-aptamer interactions are able to generate unique fingerprints allowing for monitoring and extracting real-time binding affinity by target-induced conformational changes. The gating of binding affinity was revealed in terms of controlling protein transport. Importantly, by enhancing the affinity of aptamers, selective single-molecule
detection of neurotransmitters at fM concentration was demonstrated in biological fluids such as human serum. The selective detection of neurotransmitters has yet to be achieved using solid-state nanopores. This approach was proved to be versatile for different types of
neurotransmitters, including dopamine, serotonin and acetylcholine. Further development of such a strategy may enable the improvement of nanopore sensors towards different 4 biologically important applications such as protein fingerprinting and multiplexed sensing of
different molecular targets. An outlook was made on a range of sensing modes developed on this multifunctional platform with different dynamic ranges for in-vivo monitoring of neuron activities using functionalised nanopipettes.