The field of cancer nanomedicine is moving towards maturity thanks to innovative technologies and original nanomaterials. This is required to surpass the limitations of the previous generations of nanomedicines, such as biopersistence, experimental therapeutic approaches far from the clinic, long-term toxicity of heavy metals and other compounds used in nanoparticles. Here we show how laser processing is playing a crucial role for the realization of an emerging class of advanced inorganic nanomedicines based on nanoscale alloys. Nanoparticles of Au-Fe, Au-B, Fe-B and Fe-Ag alloys have been obtained by laser-assisted synthesis, even if most of them are thermodynamically unstable. These nanoalloys exhibited multiple appealing properties for imaging and therapy of cancer and have been designed to address the issues of previous nanostructured compounds for the treatment of cancer, by endowing mid-term biodegradability, complementarity and synergy of the theranostic functions. Therefore, laser technologies are contributing to the addition of new nano-tools for addressing the treatment of cancer with higher efficacy, feasibility and tolerability.
We investigate experimentally and theoretically plasmon-enhanced optical trapping of metal nanoparticles. We calculate
the optical forces on gold and silver nanospheres through a procedure based on the Maxwell stress tensor in the transition
T-matrix formalism. We compare our calculations with experimental results finding excellent agreement. We also
demonstrate how light-driven rotations can be generated and detected in non-symmetric nanorods aggregates. Analyzing
the motion correlations of the trapped nanostructures, we measure with high accuracy both the optical trapping
parameters, and the rotation frequency induced by the radiation pressure.
Polystyrene artificial opals are directly grown with embedded gold nanoparticles (NpAu) in their interstices. Reflectance spectra of samples having different sphere diameters and nanoparticles load clearly show a red shift of the photonic band gap as well as a reduction of its width without showing direct evidence of NpAu absorption. The case of transmission spectra is instead more complicated: here, overlapped to a broad NpAu absorption, a structure having unusual lineshape is detected. The infiltration of opal with NpAu removes the polarization dependence of the photonic band structure observed in bare opals. The lineshape of the absorption spectra suggest a spatial localization of the electromagnetic field in the volume where NpAu are confined thus enhancing its local intensity. This effect seems to be effective to stimulate optical nonlinearities of NpAu. Nanosecond transient absorption measurements on NpAu infiltrated opals indicate that a variation of transmission of about 10% is observed. Since this effect takes place within the pump pulse and since NpAu photoluminescence has been subtracted to the signal, we attribute it to an optical switching process.
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