9 research outputs found
Action of Gold Nanospikes-Based Nanoradiosensitizers: Cellular Internalization, Radiotherapy, and Autophagy
A major challenge
to achieve effective X-ray radiation therapy
is to use a relatively low and safe radiation dose. Various radiosensitizers,
which can significantly enhance the radiotherapeutic performance,
have been developed. Gold-based nanomaterials, as a new type of nanoparticle-based
radiosensitizers, have been extensively used in researches involving
cancer radiotherapy. However, the cancer therapeutic effect using
the gold nanoparticle-based radiotherapy is usually not significant
because of the low cellular uptake efficiency and the autophagy-inducing
ability of these gold nanomaterials. Herein, using gold nanospikes
(GNSs) as an example, we prepared a series of thiol-polyÂ(ethylene
glycol)-modified GNSs terminated with methoxyl (GNSs), amine (NH<sub>2</sub>-GNSs), folic acid (FA) (FA-GNSs), and the cell-penetrating
peptide TAT (TAT-GNSs), and evaluated their effects on X-ray radiotherapy.
For the in vitro study, it was found that the ionizing radiation effects
of these GNSs were well correlated with their cellular uptake amounts,
with the same order of GNSs < NH<sub>2</sub>-GNSs < FA-GNSs
< TAT-GNSs. The sensitization enhancement ratio (SER), which is
commonly used to evaluate how effectively radiosensitizers decrease
cell proliferation, reaches 2.30 for TAT-GNSs. The extremely high
SER value for TAT-GNSs indicates the superior radiosensitization effect
of this nanomaterial. The radiation enhancement mechanisms of these
GNSs involved the increased reactive oxygen species (ROS), mitochondrial
depolarization, and cell cycle redistribution. Western blotting assays
confirmed that the surface-modified GNSs could induce the up-regulation
of autophagy-related protein (LC3-II) and apoptosis-related protein
(active caspase-3) in cancer cells. By monitoring the degradation
of the autophagy substrate p62 protein, GNSs caused impairment of
autolysosome degradation capacity and autophagosome accumulation.
Our data demonstrated that autophagy played a protective role against
caner radiotherapy, and the inhibition of protective autophagy with
inhibitors would result in the increase of cell apoptosis. Besides
the above in vitro experiments, the in vivo tumor growth study also
indicated that X-ray + TAT-GNSs treatment had the best tumor growth
inhibitory effect, which confirmed the highest radiation sensitizing
effect of TAT-GNSs. This work furthered our understanding on the interaction
mechanism between gold nanomaterials and cancer cells and should be
able to promote the development of nanoradiosensitizers for clinical
applications
Soil water retention under different treatments.
<p>Soil water retention under different treatments.</p
Aggregate size fractions and mean weight diameter (MWD) under different treatments.
<p>Aggregate size fractions and mean weight diameter (MWD) under different treatments.</p
Soil physicochemical properties under different treatments.
<p>Soil physicochemical properties under different treatments.</p
Linear regression between soil organic carbon (SOC) and soil mean weight diameter (MWD).
<p>ârâ indicates pearson correlation coefficient, and ** indicate significance at <i>P</i><0.01.</p
Shape-Dependent Radiosensitization Effect of Gold Nanostructures in Cancer Radiotherapy: Comparison of Gold Nanoparticles, Nanospikes, and Nanorods
The shape effect
of gold (Au) nanomaterials on the efficiency of cancer radiotherapy
has not been fully elucidated. To address this issue, Au nanomaterials
with different shapes but similar average size (âŒ50 nm) including
spherical gold nanoparticles (GNPs), gold nanospikes (GNSs), and gold
nanorods (GNRs) were synthesized and functionalized with polyÂ(ethylene
glycol) (PEG) molecules. Although all of these Au nanostructures were
coated with the same PEG molecules, their cellular uptake behavior
differed significantly. The GNPs showed the highest cellular responses
as compared to the GNSs and the GNRs (based on the same gold mass)
after incubation with KB cancer cells for 24 h. The cellular uptake
in cells increased in the order of GNPs > GNSs > GNRs. Our comparative
studies indicated that all of these PEGylated Au nanostructures could
induce enhanced cancer cell-killing rates more or less upon X-ray
irradiation. The sensitization enhancement ratios (SERs) calculated
by a multitarget single-hit model were 1.62, 1.37, and 1.21 corresponding
to the treatments of GNPs, GNSs, and GNRs, respectively, demonstrating
that the GNPs showed a higher anticancer efficiency than both GNSs
and GNRs upon X-ray irradiation. Almost the same values were obtained
by dividing the SERs of the three types of Au nanomaterials by their
corresponding cellular uptake amounts, indicating that the higher
SER of GNPs was due to their much higher cellular uptake efficiency.
The above results indicated that the radiation enhancement effects
were determined by the amount of the internalized gold atoms. Therefore,
to achieve a strong radiosensitization effect in cancer radiotherapy,
it is necessary to use Au-based nanomaterials with a high cellular
internalization. Further studies on the radiosensitization mechanisms
demonstrated that ROS generation and cell cycle redistribution induced
by Au nanostructures played essential roles in enhancing radiosensitization.
Taken together, our results indicated that the shape of Au-based nanomaterials
had a significant influence on cancer radiotherapy. The present work
may provide important guidance for the design and use of Au nanostructures
in cancer radiotherapy
Enhanced Radiosensitization of Gold Nanospikes via Hyperthermia in Combined Cancer Radiation and Photothermal Therapy
Metallic
nanostructures as excellent candidates for nanosensitizers
have shown enormous potentials in cancer radiotherapy and photothermal
therapy. Clinically, a relatively low and safe radiation dose is highly
desired to avoid damage to normal tissues. Therefore, the synergistic
effect of the low-dosed X-ray radiation and other therapeutic approaches
(or so-called âcombined therapeutic strategyâ) is needed.
Herein, we have synthesized hollow and spike-like gold nanostructures
by a facile galvanic replacement reaction. Such gold nanospikes (GNSs)
with low cytotoxicity exhibited high photothermal conversion efficiency
(η = 50.3%) and had excellent photostability under cyclic near-infrared
(NIR) laser irradiations. We have demonstrated that these GNSs can
be successfully used for in vitro and in vivo X-ray radiation therapy
and NIR photothermal therapy. For the in vitro study, colony formation
assay clearly demonstrated that GNS-mediated photothermal therapy
and X-ray radiotherapy reduced the cell survival fraction to 89% and
51%, respectively. In contrast, the cell survival fraction of the
combined radio- and photothermal treatment decreased to 33%. The synergistic
cancer treatment performance was attributable to the effect of hyperthermia,
which efficiently enhanced the radiosensitizing effect of hypoxic
cancer cells that were resistant to ionizing radiation. The sensitization
enhancement ratio (SER) of GNSs alone was calculated to be about 1.38,
which increased to 1.63 when the GNS treatment was combined with the
NIR irradiation, confirming that GNSs are effective radiation sensitizers
to enhance X-ray radiation effect through hyperpyrexia. In vivo tumor
growth study indicated that the tumor growth inhibition (TGI) in the
synergistically treated group reached 92.2%, which was much higher
than that of the group treated with the GNS-enhanced X-ray radiation
(TGI = 29.8%) or the group treated with the GNS-mediated photothermal
therapy (TGI = 70.5%). This research provides a new method to employ
GNSs as multifunctional nanosensitizers for synergistic NIR photothermal
and X-ray radiation therapy in vitro and in vivo
Glutathione-Depleting Gold Nanoclusters for Enhanced Cancer Radiotherapy through Synergistic External and Internal Regulations
The
therapeutic performance of cancer radiotherapy is often limited by
the overexpression of glutathione (GSH) in tumors and low radiation
sensitivity of cancerous cells. To address these issues, the facilely
prepared histidine-capped gold nanoclusters (Au NCs@His) were adopted
as a radiosensitizer with a high sensitization enhancement ratio of
âŒ1.54. On one hand, Au NCs@His can inherit the local radiation
enhancement property of gold-based materials (external regulation);
on the other hand, Au NCs@His can decrease the intracellular GSH level,
thus preventing the generated reactive oxygen species (ROS) from being
consumed by GSH, and arrest the cells at the radiosensitive G2/M phase
(internal regulation)
Construction of Smart Glutathione SâTransferase via Remote Optically Controlled Supramolecular Switches
A supramolecular
switch strategy that can reversibly âturn-onâ
and âturn-offâ glutathione S-transferase (GST) is presented,
which provides a proof-of-concept for a simple but efficient way to
regulate the catalytic function of natural enzymes. This design is
demonstrated by incorporating azobenzene/cyclodextrin-based supramolecular
hostâguest systems into the catalytic pocket of GST. The photoisomerization
of <i>trans</i>- and <i>cis</i>-azobenzene leads
to supramolecular complexation and dissociation of cyclodextrin, and
thereby controls the enzymatic activity of GST by tuning substrate
accessibility. This photoswitchable catalysis is reversible over multiple
stimulus cycles. Furthermore, its capability is affected by the spatial
size and binding affinity of different cyclodextrins, as well as the
modification sites of azobenzene. The remote optical modulation method
could offer great opportunities in the effort to create âsmartâ
catalysts