Abstract
Several
examples of nanosized therapeutic and imaging agents have been proposed
to date, yet for most of them there is a low chance of clinical
translation due to long-term in vivo retention and toxicity risks. The
realization of nano-agents that can be removed from the body after use
remains thus a great challenge. Here, we demonstrate that
non-equilibrium gold-iron alloys behave as shape-morphing nanocrystals
with the properties of self-degradable multifunctional nanomedicines.
DFT calculations combined with mixing enthalpy-weighted alloying
simulations predict that Au-Fe solid solutions can exhibit
self-degradation in aqueous environment if the Fe content exceeds a
threshold that depends upon element topology in the nanocrystals.
Exploiting a laser-assisted synthesis route, we experimentally confirm
that non-equilibrium Au-Fe nanoalloys have a 4D behavior, that is the
ability to change shape, size and structure over time, becoming
ultrasmall Au-rich nanocrystals. In vivo tests
show the potential of
these transformable Au-Fe nanoalloys as efficient multimodal contrast
agents for magnetic resonance imaging and computed x-ray absorption
tomography and further demonstrate their self-degradation over time,
with a significant reduction of long-term accumulation in the body, when
compared to benchmark gold or iron oxide contrast agents. Hence, Au-Fe
alloy nanoparticles exhibiting 4D behavior can respond to the need for
safe and degradable inorganic multifunctional nanomedicines required in
clinical translation.
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