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Title: Nanomaterials for intracellular fluorescence imaging and sensing
Author: dos Santos Almeida, Carina Marisa
ISNI:       0000 0004 6348 1913
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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This thesis explores the use of nanomaterials for bioimaging using conjugated polymer nanoparticles (CPNs) and porous silicon nanoneedles (PSNs) for intracellular biosensing. CPNs have recently started being used in biomedical research due to their outstanding optical properties, such as large extinction coefficients and high fluorescence brightness. Several strategies have been developed to stabilise their surface and provide functional groups for subsequent biomolecule conjugation. Peptides are highly customisable molecules and possess several advantages when compared to other capping ligands. A one-pot synthesis and peptide functionalisation method for CPNs using peptide amphiphiles was developed and it was shown that the presence of the peptide amphiphile did not affect the advantageous optical properties of CPNs. By using peptide amphiphiles with different characteristics, it was possible to tailor the cellular uptake of peptide-CPNs, proving the bioactivity of these nanoparticles. Importantly, none of the used peptide-CPNs demonstrated cell cytotoxicity. Other conjugated polymer (CPs) were used to synthesise peptide-CPNs of different colours, demonstrating the versatility of this method. PSNs have been developed for probing the intracellular environment for delivery or sensing. Access to the cytoplasm of cells is difficult using other methods and therefore PSNs are a suitable candidate for a biocompatible and minimally invasive approach. PSNs were functionalised to a cathepsin B (CTSB) protease cleavable peptide with an imaging moiety that would be released upon CTSB sensing. Optimal conditions for the biosensor assembly were determined in silicon chips. Moreover, two oesophageal cell lines were chosen for in vitro studies and their CTSB expression studied. Incubation of PSNs with cells showed tight interfacing without harming to cells. Finally, an intracellular pH sensor using PSNs was developed and it showed linear response in a biologically relevant window. Collectively, these results have contributed to new ways of interfacing functional nanomaterials with the cellular environment.
Supervisor: Stevens, Molly ; Porter, Alexandra Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral