118
C. de Julián Fernández and F. Pineider
n-IR region where the first optical window, at around 700–800 nm, is present. This
allows the development of in-vivo plasmon-assisted imaging techniques, but also for
the application of photo-thermal therapy [130, 132, 134, 135] for deeper tissues.
Besides their plasmonic properties, gold nanostructures are investigated in
biomedicine for their low cytotoxicity, biocompatibility and inertness [4, 93, 139,
140] and/or the established and wide possibilities of functionalization of Au surfaces
with large number of molecules and materials [4, 5, 139, 141, 142]. The plasmonic
moiety—attached to another active component—can assure the protection of the
active component to chemically and biologically reactive or aggressive media. The
gold moiety can cover the active component in such a way to reduce its toxicity
or its release rate. Hence, plasmonic nanostructures are considered as key actuators for biomedical applications like drug delivery and genetic manipulation but
also for environment sustainability [4, 8, 139, 141]. These questions are particularly
important for applications in which magnetic nanoparticles are involved: except the
Fe oxides (magnetite or maghemite), most of magnetic compounds are chemically
oxidisable, reactive, and considered cytotoxic [140, 143, 144]. Hence the term “magnetoplasmonic” is also employed to define also hetero-nanostructures in which the
magnetic moiety is covered by an Au layer or by Au NPs. Nowadays strong activity
is performed in the understanding of the clearance, retention and toxicity of several
MP nanostructures [145–148].
Concerning magnetic applications, MP NPs are now appealing for biomedical
applications (some cases represented in Fig. 5.4), and are being considered also for
catalysis and environmental applications. Like bare magnetic nanoparticles, the MP
NPs can be moved and placed or concentrated in a region, tissue or on device using
magnetic fields [113, 149]. These systems allow also the active particle concentration
and guiding for in-vivo and in vitro biomedical applications [35, 36, 113, 133, 134,
149, 150] and improvements of concentration or separation for biomedical analysis
[151–157]. They have also been employed as contrast agents using Nuclear Magnetic
Resonance (NMR) [36, 62, 66, 157–162] and ultrasound biomedical imaging techniques [163, 164]. Several studies have demonstrated the improved relaxivity features
of MP NPs, faster relaxation times (T1) than the commercial particles and promising
T2 dephasing times. This has been observed both in Au–Fe 3 O 4 heterostructures [157,
161, 162] and in weakly magnetic AuFe alloy-based NPs [27, 128] showing how the
novel magnetic structures of these hybrid materials can improve the properties of bare
magnetic particles. Finally, the heat generation of the MP NPs irradiated by radiofrequency magnetic field and its employment for cancer therapy was demonstrated [62,
81, 92, 94, 97, 121, 165–168]. The aim is to produce externally a local heating that
can induce the apoptosis of cancer cells, the thermal induced release of drug or the
activation or increase of efficiency of drugs. In addition, a novel approach of cancer
therapy based on magnetomotive activity, mechanical or stress-induced damages
produced by the rotation of the magnetic particles into the cellular target, was developed considering MP nanostructures [169, 170]. In this case the capping of Au layer
of the magnetic moiety allows the surface functionalization, low cytotoxicity and it
ensures the chemical and mechanical stability during the rotation or vibration of the
particles into the cells.
C. de Julián Fernández and F. Pineider
n-IR region where the first optical window, at around 700–800 nm, is present. This
allows the development of in-vivo plasmon-assisted imaging techniques, but also for
the application of photo-thermal therapy [130, 132, 134, 135] for deeper tissues.
Besides their plasmonic properties, gold nanostructures are investigated in
biomedicine for their low cytotoxicity, biocompatibility and inertness [4, 93, 139,
140] and/or the established and wide possibilities of functionalization of Au surfaces
with large number of molecules and materials [4, 5, 139, 141, 142]. The plasmonic
moiety—attached to another active component—can assure the protection of the
active component to chemically and biologically reactive or aggressive media. The
gold moiety can cover the active component in such a way to reduce its toxicity
or its release rate. Hence, plasmonic nanostructures are considered as key actuators for biomedical applications like drug delivery and genetic manipulation but
also for environment sustainability [4, 8, 139, 141]. These questions are particularly
important for applications in which magnetic nanoparticles are involved: except the
Fe oxides (magnetite or maghemite), most of magnetic compounds are chemically
oxidisable, reactive, and considered cytotoxic [140, 143, 144]. Hence the term “magnetoplasmonic” is also employed to define also hetero-nanostructures in which the
magnetic moiety is covered by an Au layer or by Au NPs. Nowadays strong activity
is performed in the understanding of the clearance, retention and toxicity of several
MP nanostructures [145–148].
Concerning magnetic applications, MP NPs are now appealing for biomedical
applications (some cases represented in Fig. 5.4), and are being considered also for
catalysis and environmental applications. Like bare magnetic nanoparticles, the MP
NPs can be moved and placed or concentrated in a region, tissue or on device using
magnetic fields [113, 149]. These systems allow also the active particle concentration
and guiding for in-vivo and in vitro biomedical applications [35, 36, 113, 133, 134,
149, 150] and improvements of concentration or separation for biomedical analysis
[151–157]. They have also been employed as contrast agents using Nuclear Magnetic
Resonance (NMR) [36, 62, 66, 157–162] and ultrasound biomedical imaging techniques [163, 164]. Several studies have demonstrated the improved relaxivity features
of MP NPs, faster relaxation times (T1) than the commercial particles and promising
T2 dephasing times. This has been observed both in Au–Fe 3 O 4 heterostructures [157,
161, 162] and in weakly magnetic AuFe alloy-based NPs [27, 128] showing how the
novel magnetic structures of these hybrid materials can improve the properties of bare
magnetic particles. Finally, the heat generation of the MP NPs irradiated by radiofrequency magnetic field and its employment for cancer therapy was demonstrated [62,
81, 92, 94, 97, 121, 165–168]. The aim is to produce externally a local heating that
can induce the apoptosis of cancer cells, the thermal induced release of drug or the
activation or increase of efficiency of drugs. In addition, a novel approach of cancer
therapy based on magnetomotive activity, mechanical or stress-induced damages
produced by the rotation of the magnetic particles into the cellular target, was developed considering MP nanostructures [169, 170]. In this case the capping of Au layer
of the magnetic moiety allows the surface functionalization, low cytotoxicity and it
ensures the chemical and mechanical stability during the rotation or vibration of the
particles into the cells.