Human serum albumin encapsulated gold nanoclusters: effects of cluster synthesis on natural protein characteristics

B. A. Russell, B. Jachimska, I. Kralka, P. A. Mulheran, Y. Chen

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Abstract

The differences in physiochemical properties between native Human Serum Albumin (HSA) and HSA encapsulated gold nanoclusters (HSA-AuNCs) are characterised. The molecules light absorbance (UV/Vis), electrophoretic mobility, dynamic viscosity, density, hydrodynamic radius (DLS), absorption (QCM) and chemical bonding (XPS) characteristics were studied. The UV/Vis and DLS data shows the formation of large aggregates for HSA-AuNCs between pH 4-6 which is not observed for native HSA. This observation was further supported by QCM measurements showing a large increase in mass adsorbed at pH 6 between HSA and HSA-AuNCs. The DLS data also reveals a hydrodynamic radius of 12nm for HSA-AuNCs, nearly double that of 7nm for native HSA at pH higher than 6, suggesting the formation of compact HSA-AuNCs dimers. The electrophoretic mobility data for both HSA-AuNCs and HSA were converted to zeta potentials. The zeta potential of HSA-AuNCs was seen to be more negative between pH6-12, suggesting that the protein surface is interacting with unreacted gold salt anions. Measurements of density and viscosity were also found to be in agreement with previous data suggesting HSA-AuNCs forms aggregates. XPS data also suggests that not all reactants are used up during the HSA-AuNCs synthesis and positive side chains play a part in the initial synthesis stages. It was concluded that HSA-AuNCs most likely form dimers at natural and high pH. Between pH 4-6 HSA-AuNCs form very large aggregates limiting their use as a fluorescent probe in this pH range. It was also found that the native characteristics of HSA are altered upon HSA-AuNCs synthesis which needs to be taken into consideration when applying HSA-AuNCs as a fluorescent probe in all fluorescent imaging and sensing.
Original languageEnglish
Number of pages7
JournalJournal of Materials Chemistry B
Early online date29 Sep 2016
DOIs
Publication statusE-pub ahead of print - 29 Sep 2016

Keywords

  • gold nanoclusters
  • human serum albumin
  • physiochemical properties
  • light absorbance
  • electrophoretic mobility
  • dynamic viscosity
  • density
  • hydrodynamic radius
  • absorption
  • chemical bonding
  • fluorophores

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