Gold nanostars: surfactant-free synthesis, 3D modelling, and two-photon photoluminescence imaging

Abstract

Understanding the control of the optical and plasmonic properties of unique nanosystems—gold nanostars—both experimentally and theoretically permits superior design and fabrication for biomedical applications. Here, we present a new, surfactant-free synthesis method of biocompatible gold nanostars with adjustable geometry such that the plasmon band can be tuned into the near-infrared region ‘tissue diagnostic window’, which is most suitable for in vivo imaging. Theoretical modelling was performed for multiple-branched 3D nanostars and yielded absorption spectra in good agreement with experimental results. The plasmon band shift was attributed to variations in branch aspect ratio, and the plasmon band intensifies with increasing branch number, branch length, and overall star size. Nanostars showed an extremely strong two-photon photoluminescence (TPL) process. The TPL imaging of wheat-germ agglutinin (WGA) functionalized nanostars on BT549 breast cancer cells and of PEGylated nanostars circulating in the vasculature, examined through a dorsal window chamber in vivo in laboratory mouse studies, demonstrated that gold nanostars can serve as an efficient contrast agent for biological imaging applications.

Gold nanostars for efficient in vitro and in vivo real-time SERS detection and drug delivery via plasmonic-tunable Raman/FTIR imaging

“…13,37 Thus, gold nanostars are unique materials with an intense surface plasmon band that affords absorption in the near-infrared region. [21][22][23][24][25][26] with MTX-nanostars during 48 hours of incubation using the Perkin Elmer Spotlight 400 system for the FTIR and the LabRAM HR Evolution spectrometer for the SERS maps.…”

“…[17][18][19][20] They display two surface plasmon bands consistent to the transverse and longitudinal surface plasmon bands in the visible (520 nm) and the near-infrared regions, respectively 15 Thus, gold nanostars are special materials with an intense surface plasmon band that affords absorption, fluorescence [21][22][23] and light scattering 24,25 in the near-infrared region, inducing two-photon luminescence phenomena. 26 Hexadecyltrimethylammonium bromide (CTAB) is a common material for gold nanostar synthesis. CTAB provides a cationic detergent to stabilizing agent during the preparation of gold nanostars.…”

Gold Nanostar Substrates for Metal-Enhanced Fluorescence through the First and Second Near-Infrared Windows

“…40,43 First, spherical citrate-stabilized 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Figure S1). Since no changes to these spectra were detected, the reaction is already complete within seconds of AA addition.…”

“…Therefore, the 30 s of stirring time were selected, like previous reports, 40 as an adequate stirring time that confidently ensured that the formation of AuNS had been completed.…”

Spatial Analysis of Metal–PLGA Hybrid Microstructures Using 3D SERS Imaging

“…[42] Adding 5 mL of 34 × 10 −3 m citrate solution to 95 mL of boiling 0.5 × 10 −3 m HAuCl 4 solution under vigorous stirring and then maintaining boiling for 15 min, seed particles were formed. 50 nm AuNSs with an LSPR maximum at 750 nm, were prepared by adding 2.5 mL Synthesis of Silver Nanoparticles: A modification of a previously reported approach was used to prepare 30 nm Ag NPs.…”