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School of Physical and Chemical Sciences

Palma Group Research

The Palma group’s research focusses on the controlled assembly of functional nanostructures using a multidisciplinary approach spanning chemistry, biology, and physics. We use molecular interactions to drive the self-organisation of different building blocks including carbon nanotubes and DNA nanostructures for the development of functional devices as well as the investigation of fundamental biological and physical processes.

Carbon nanotubesFigure 1. CNT-protein hybrid (top left), CNT-quantum dot (QD) hybrid (top right), and schematic for CNT-aptamer biosensors (bottom).

Carbon nanotubes (CNTs) form a key part of our research, and they can be thought of as rolled up single-layer sheets of hexagonally-ordered carbon atoms. Due to their chemical structure, they have several interesting properties that we look to exploit. They can be considered conductive nanosized wires, and therefore can be used as components in nanoscale electrical devices. We can functionalise CNTs covalently and non-covalently while controlling the placement of single moieties. We have demonstrated the attachment of single proteins and nanoparticles specifically to the ends of CNTs (see figure 1), where we investigated their electronic interactions at the single-molecule level. We have also demonstrated the functionalisation of CNT sidewalls with aptamers, which are short DNA sequences which can selectively bind to specific molecules. These aptamer-functionalised CNTs can be used in the fabrication of biosensors by aligning them between electrodes where the concentration of stress biomarkers could be monitored via the electrical current.

Using DNA as a structual material Figure 2. DNA origami functionalised with three nanoparticles in defined locations (above), and schematic of patterns of functionalised DNA origami for cell spreading investigations.

Another key aspect of our work involves using DNA as a structural material. Due to DNA’s predictable interactions between bases, we can design sequences to function as simple linkers in end-functionalised CNT hybrids. We designed CNT-nanoparticle hybrids where by changing length of the DNA sequences we could control the distance between CNT and nanoparticle. In addition, we have used DNA as a linker where we could reversibly assemble and disassemble DNA-functionalised CNTs through the addition of various stimuli. Aside from simple structural uses of DNA, we can design large structures called DNA origami, where the DNA is “folded” into 2D shapes. We use these structures as scaffolds for the organisation of molecules and nanomoieties at the single-molecule level with nanometre precision. We have previously demonstrated the assembly of specific numbers of nanoparticles on DNA origami, where the nanostructures were placed in precise locations on a patterned substrate (see figure 2). Furthermore, we have decorated DNA origami with cell-binding peptides and proteins in order to investigate their cooperative behaviour in the spreading of cancer cells.

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