Synthesis and Cytotoxicity Studies of Gold Nanoparticle Systems
In this work, the immobilisation of different biomolecules on thioalkylated polyethelene glycol (PEG)-capped gold monolayer protected clusters (MPCs) has been successfully conducted. This followed a series of aqueous and nonaqueous synthetic protocols carried out to synthesize gold nanoparticles and MPCs of sizes ranging between 4 – 200 nm. Hetero-bifunctional PEG ligands possessing functionalities such as carboxyl, hydroxyl, biotin and nitrilotriacetic acid (NTA) were introduced resulting in stable, biocompatible gold MPCs, templates for biomolecular functionalisation reactions. Biomolecular functionalisation strategies such as carbodiimide coupling, biotin-avidin interaction and Ni-NTA-histidine interactions following the introduction of the bivalent hexadentate Ni(II) onto the NTA matrix of the MPCs, were conducted to formulate the biomolecular hybrid systems. A range of biomolecules including the cell-penetrating TAT peptide (YGRKKRRQRRR), mitogen-activated protein kinase (MAP kinase), streptavidin and fluorescent-labelled FAM-TAT peptide were successfully immobilised on the gold MPCs. The simplicity of the synthetic approaches and the stability of the resultant biomolecular systems strengthened their potential applications in targeted drug delivery, molecular recognition tools for diagnostics and in the purification, quantification and beneficiation of tagged fusion biomolecules. The colloidal gold nanoparticles, MPCs and bioconjugates were further investigated for inherent biologic effects through a series of end-point based in vitro assays. The cytotoxicity, namely the causation of necrotic cell death was studied using the neutral red assay on CHO22 cell line. All three system types showed benign cytotoxicity properties; demonstrating minor dose-dependence decline in cell viability through necrotic cell death. Additionally, dose-dependent patterns were also observed in the apoptosis-induction effects of these gold systems on CHO22 and CD4 expressing Jurkat cell lines. Overall, this work demonstrated facile protocols of synthesis for colloidal gold nanoparticles, MPCs and bioconjugates, and subsequently through in vitro cellular interaction assays, demonstrated these systems as useful tools for application in life sciences and related fields.
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