Antibody-Functionalized Inorganic NPs: Mimicking Nature for Targeted Diagnosis and Therapy - Bioinspired Approaches for Human-Centric Technologies - page 2

cure many diseases. These range from the more conventional ones, like rheumatoid
arthritis, to different types of cancers, to more specialized pathologies (e.g., the
so-called rare diseases) (Chan and Carter 2010 ).
In the cancer field, monoclonal antibodies directed against clinically validated
tumor targets, such as tumor necrosis factors (TNF), or against human epidermal
growth factors overexpressed in certain types of tumors (such as lung and colon
cancer to cite only some examples) have been successfully proven to block tumor
growth (Dougan and Dranoff 2009 ). In the last 20 years, antibodies have been
exploited not only to promote the immune response but also as the Trojan horses to
deliver radionuclides in radio-immunotherapy: synergic effects due to the combi-
nation of radiotherapy with immunotherapy have improved the patient survival in
specific cancer types (Waldmann 2003 ).
Nanotechnology is now developing new promising materials for fighting cancer
(Nie et al. 2007 ). Among the proposed treatments that make use of inorganic
nanoparticles, we mention, for example, hyperthermia, which is based on the
local temperature increase directly to the tumor area. Even in this form of therapy,
the inspiration comes from nature: fever is indeed a body defense mechanism that
weakens bacteria and viruses and activates the immune response. Likewise, in case
of “artificially induced hyperthermia,” the generated heat will preferentially kill
tumor cells, which are more vulnerable than healthy cells to stress conditions, and
at the same time it should also activate the immune response. Magnetic, semi-
conductor and metal nanocrystals, consisting of crystalline clusters of atoms (from
few atoms up to several tens of atoms), are some of the nanomaterials which are
currently exploited as nano-heating probes for hyperthermia (Cherukuri et al. 2010 ;
Kumar and Mohammad 2011 ). These nanocrystals can be truly defined as a new
generation of “nanoimplants” for hyperthermia, as they have the unique advantage
of being actuated by a specific external source. This could be a radio frequency, in
the cases of magnetic nanoparticles, or a laser, in the case of plasmonic and
semiconductor nanoparticles. This offers the great advantage to generate a heat
gradient only in the proximity of the place where the nanoparticles are accumulated
and thus to specifically kill cells with whom these particles are associated
(for instance, a tumor mass). Moreover, their external activation can allow the
personalization of the treatment, for example, through multiple applications
depending on the specific clinical case. The same types of nanoparticles can be
also used as chemotherapeutic delivery tools operating via a triggered drug release
mechanisms, since the heat produced by the nanoparticles could additionally induce
the controlled release of drug molecules (either chemotherapeutic agents or short
oligonucleotides) associated to the nanoparticle.
Particularly interesting is the association of nanocrystals with thermo-responsive
polymers: this unique class of polymers can change their conformation as a result of
temperature variation; when increasing the temperature above a defined threshold,
the polymer structure undergoes a transition from a stretched to a coiled configu-
ration. If nanocrystals capable of eliciting hyperthermia are encapsulated in these
polymers, together with other payloads, the heat released by them will cause
mechanical shrinkage of the polymer and subsequent release of the payload.