A protocol was selected and optimized using design of experiments to produce gold nanostar particles that meet all essential parameters. Six batches of nanostar particles were then manufactured at various scales from 500ml to 5l, and all batches were characterized. Analysis found that gold nanostars can be manufactured at different volumes and have potential applications as plasmonic sensors, theranostics, and providing a blue test line in lateral flow immunoassays. Nanostars were shown to have stronger Raman scattering than nanospheres using surface enhanced Raman spectroscopy.

1. Fabrication
Following a matrix analysis of existing published and in-house methods, a protocol was selected for optimisation and scale up. To ensure the development of a robust methodology, a
Design of Experiments system was used; incorporating 2 dimensional factorial design, to determine and optimise the critical factors affecting particle morphology. Following several
screens, a design space was created which resulted in the production of a particle that meets all essential parameters. Successful optimisation of this process then followed and six
batches of nanostar particles were manufactured at a variety of scales (500ml, 1L, 2L and 5L) to determine robustness of the manufacturing method. All batches were subsequently
characterised using the methodology detailed below.
Fabrication and Characterisation of
Gold Nanostars
K. Warner1, K. Thomson2, P. Gancitano3
1 BBI Solutions, Cardiff, CF14 5DX, UK
2 BBI Solutions, Dundee, DD2 1NH, UK
3 Centre for Molecular Nanometrology, University of Strathclyde, Glasgow, G1 1RD, UK
kellywarner@bbisolutions.com
Introduction
BBI Solutions has been a world leader in the development and manufacture of lateral flow immunoassays and diagnostic reagents for over 25 years.
While the mechanisms of production and characteristics of spherical gold nanoparticles have been extensively described, an increased interest has
been observed in anisotropic nanoparticles during the last decade; including bi-pyramids, nanorods, nanowires and nanostars, due to the novel
physical properties offered.
Recent studies have been carried out on the unique optical properties that gold nanostars possess which can provide insight into some of their
potential applications. BBI has undertaken an internal development project to fabricate and characterise gold nanostars to better understand their
unique optical properties and apply them in current applications to determine their potential uses.
Discussion and Potential Applications
Analysis of the data obtained indicates that gold nanostars can be manufactured at a range of volumes.
Analysis of current literature indicates gold nanostars have already been identified as potential plasmonic sensors and theranostics primarily due to the unique optical properties
presented versus conventional spherical particles. In addition to these applications, feasibility studies conducted by BBI Solutions indicate that nanostar particles can be conjugated to
antibodies and used within lateral flow immunoassays to provide a blue test line versus standard red gold nanospheres.
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Acknowledgements
The authors would like to acknowledge the support of the Particle Synthesis and New Product Development groups at BBI Solutions for assistance in development, Dr Samuel Mabbott
for assistance in SEM analysis and Keir Thomas for his unending support and encouragement.
Characterisation
Samples were analysed using a Phillips CM12 Transmission Electron Microscope (TEM)
Images were taken using a MegaView III camera (using iTEM software) at a variety of
magnifications to illustrate particle size and shape.
UV-Visible Spectrophotometer Transmission Electron Microscopy (TEM)
Samples were analysed using a Hitachi UV-Vis Spectrophotometer
Samples were scanned from 1000nm - 400nm at supplied stock to determine the absorbance
spectra.
Comparison of the absorbance spectra of Nanostar Particles (Batches 16975 - 16980)
manufactured at various volume scales
0
0.2
0.4
0.6
0.8
1
1.2
1.4
350 450 550 650 750 850 950 1050
Absorbance
Wavelength (nm)
16975 - 500ml
16976 - 1L
16977 - 1L
16978 - 1L
16979 - 2L
16980 - 5L
Scanning Electron Microscopy (SEM)
Samples were analysed using a FEI Quanta 250 FEG Environmental
Scanning Electron Microscope. (SEM)
Surface Enhanced Raman Spectroscopy (SERS)
Initial experimentation indicated that the best dye to use with gold nanostars at λex = 785 nm
was Malachite Green Isothiocyanate (MGITC). To compare the Raman scattering of gold
nanostars and spherical gold particles, gold nanostars (Batch 16967) and 40nm spherical
gold particles (BBI Solutions) were incubated with 10 µM MGITC.
SERS spectra were taken using a Snowy Range Sierra 2.0. The SERS spectra of MGITC
was provided for comparison.
Scale bar on images to provide reference of individual star sizes
a
dc
b
0
200
400
600
800
1000
1200
1400
1600
1800
2000
200 400 600 800 1000 1200 1400 1600 1800 2000
Intensity
Raman shift (cm-1)
Nanospheres Nanostars
MGITC (no NPs)
SERS spectra of MGITC functionalised Nanostar particles, MGITC functionalised 40nm
nanospheres and MGITC as a control
SEM images of Nanostar Particles (Batches 16975, 16976, 16979 and16980) manufactured at various
volumes (a-500ml, b-1L, c-2L, d-5L)