2 research outputs found
Ultrafast Excited-State Dynamics in Shape- and Composition-Controlled Gold–Silver Bimetallic Nanostructures
In
this work, we have examined the ultrafast dynamics of shape-
and composition-controlled bimetallic Au/Ag core/shell nanostructures
with transient absorption spectroscopy (TAS) as a function of Ag layer
thickness (0–15 nm) and pump excitation fluence (50–500
nJ/pulse). Our synthesis approach generated both bimetallic nanocubes
and nanopyramids with distinct dipolar plasmon resonances and plasmon
dephasing behavior at the resonance. Lifetimes obtained from TAS at
low powers (50 nJ/pulse) demonstrated minimal dependence on the Ag
layer thickness, whereas at high power (500 nJ/pulse) a rise in electron–phonon
coupling lifetime (Ï„<sub>1</sub>) was observed with increasing
Ag shell thickness for both nanocubes and nanopyramids. This is attributable
to the stronger absorption of the 400 nm pump pulse with higher Ag
content, which induced higher electron temperatures. The phonon–phonon
scattering lifetime (Ï„<sub>2</sub>) also rises with increasing
Ag layer, contributed both by the increasing size of the Au/Ag nanostructures
as well as by surface chemistry effects. Further, we observed that
even the thinnest, 2 nm, Ag shell strongly impacts both Ï„<sub>1</sub> and Ï„<sub>2</sub> at high power despite minimal change
in overall size, indicating that the nanostructure composition also
strongly impacts the thermalization temperature following absorption
of 400 nm light. We also observed a shape-dependent trend at high
power, where Ï„<sub>2</sub> increased for the nanopyramids with
increasing Ag shell thickness and nanostructure size, but bimetallic
nanocubes demonstrated an unexpected decrease in Ï„<sub>2</sub> for the thickest, 15 nm, Ag shell. This was attributed to the larger
number of corners and edges in the nanocubes relative to the nanopyramids
Gold Nanoantenna-Mediated Photothermal Drug Delivery from Thermosensitive Liposomes in Breast Cancer
In
this work, we demonstrate controlled drug delivery from low-temperature-sensitive
liposomes (LTSLs) mediated by photothermal heating from multibranched
gold nanoantennas (MGNs) in triple-negative breast cancer (TNBC) cells
in vitro. The unique geometry of MGNs enables the generation of mild
hyperthermia (∼42 °C) by converting near-infrared light
to heat and effectively delivering doxorubicin (DOX) from the LTSLs
in breast cancer cells. We confirmed the cellular uptake of MGNs by
using both fluorescence confocal Z-stack imaging and transmission
electron microscopy (TEM) imaging. We performed a cellular viability
assay and live/dead cell fluorescence imaging of the combined therapeutic
effects of MGNs with DOX-loaded LTSLs (DOX-LTSLs) and compared them
with free DOX and DOX-loaded non-temperature-sensitive liposomes (DOX-NTSLs).
Imaging of fluorescent live/dead cell indicators and MTT assay outcomes
both demonstrated significant decreases in cellular viability when
cells were treated with the combination therapy. Because of the high
phase-transition temperature of NTSLs, no drug delivery was observed
from the DOX-NTSLs. Notably, even at a low DOX concentration of 0.5
μg/mL, the combination treatment resulted in a higher (33%)
cell death relative to free DOX (17% cell death). The results of our
work demonstrate that the synergistic therapeutic effect of photothermal
hyperthermia of MGNs with drug delivery from the LTSLs can successfully
eradicate aggressive breast cancer cells with higher efficacy than
free DOX by providing a controlled light-activated approach and minimizing
off-target toxicity