Investigating self-assembling nanomaterials (Sans) within a biological environment

  • Gennaro Dichello

    Student thesis: Doctoral Thesis


    Nanomaterials are defined as structures possessing one or more dimensions
    below 100 nanometres in size. They display unique properties that arise as a
    result of quantum behaviours, owing to their high surface area to volume
    ratios. Self-assembling nanomaterials (SANs), where individual components
    referred to as “building blocks” spontaneously organise into complex
    structural arrangements, is a prominent field that offers technological
    innovation within medicine and beyond. To effectively exploit this approach in
    healthcare however, a high-level of behavioural understanding within
    biological systems is required, which has yet to be ascertained.
    Accordingly, work undertaken in this thesis aimed to investigate how gold
    nanoparticles self-assemble and interact within a biological environment.
    Molecular recognition and electrostatic attraction, two different underpinning
    mechanisms of self-assembly were studied. Based on findings within this
    thesis, the latter approach was chosen for further development.
    Corresponding functional gold nanoparticles were incorporated into
    PEGylated liposomes using a novel method and extensively characterised.
    Comparative cytotoxicity evaluation was carried out in vitro on a male
    Chinese hamster lung fibroblast cell line (V79), employing MTT and LDH
    assays. Investigations focused on identifying any differences in biological
    response after treatment with individually dispersed gold nanoparticles and
    as they underwent in situ self-assembly. Cellular uptake and any ensuing
    self-assembly was investigated using a combination of electron microscopy
    and elemental analysis on thin-sectioned specimens.
    Results presented in this thesis reveal that both electrostatic interactions and
    molecular recognition facilitate self-assembly under aqueous conditions.
    Within a biologically relevant medium however, considerable nanoparticlebiomolecule
    complex formation occurs and only particles exploiting
    electrostatic interactions persist to self-assemble. Gold nanoparticles were
    capable of being encapsulated within liposomes by exploiting electrostatic attractions between oppositely charged lipids and ligands on particle
    surfaces. The novel method resulted in variable internalised gold to lipid
    ratios, hypothesised to result from differing magnitudes of electrostatic
    attraction during preparation. At clinically relevant concentrations, gold
    nanoparticles functionalised with cationic or anionic ligands did not display
    significant cytotoxicity. A significant difference in cytotoxicity was displayed
    as they underwent in situ assembly however. Cellular internalisation of gold
    was evidenced, with nanoparticles seen to accumulate and reside within
    cellular vacuoles, but no confirmation of self-assembly was obtained.
    In conclusion, the current work provides further knowledge regarding the
    feasibility, risk and current limitations associated with utilising and evaluating
    nanomaterials for in-situ self-assembly within biological environments.
    Extensive interactions shown to occur between initial building blocks and
    biological components can hinder self-assembly activity, highlighting the
    importance of rational design when manufacturing SANs. Individual
    nanoparticles were encapsulated within surface-modified liposomes,
    demonstrating a possible strategy towards implementing further control over
    SANs. Cellular studies identified a difference in toxicity between individual
    building blocks and their assembled suprastructures, demonstrating that
    unique biological responses could arise from the self-assembly of SANs.
    Evaluation of intracellular self-assembly and the ability to differentiate
    between individual building blocks, assembled suprastructures and cellular
    components is inherently difficult. Current techniques and approaches
    require further development to enable routine and reliable assessment of
    analogous in situ self-assembling nanosystems.
    Date of AwardNov 2017
    Original languageEnglish
    Awarding Institution
    • University of Brighton
    SupervisorDipak Sarker (Supervisor)

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