Antibody-Functionalized Inorganic NPs: Mimicking Nature for Targeted Diagnosis and Therapy - Bioinspired Approaches for Human-Centric Technologies - page 16

proteins with different functional properties, and, if properly engineered, also their
immune response can be modulated. Today, thanks to biotechnological advances,
chimeric antibodies can be prepared directly, although the production costs for such
materials are not affordable yet. Moreover, because of the native function of the
antibodies, the injection of large amounts of nanoparticle-bound antibodies could
trigger an immune response, even when this effect is not desired for therapeutic
purposes. This issue is strictly related to the poor control over the conjugation
chemistry and to the estimation of the average number of antibody molecules per
nanoparticle, which is often presumed rather than realistic. New methods are
certainly needed to prepare nanoparticles with a precise number of antibody
molecules.
Finally, another critical point, which is often underestimated but should be
mentioned, regards the biological fragility of the biomolecules. Precautions need
to be undertaken when handling free or nanoparticle-bound antibodies, as some
denaturing conditions need be avoided. The list includes the use of high-energy
radiations, organic solvents, buffers with extreme pH conditions, and high temper-
atures, to cite the most important ones. Additionally, the storage conditions and the
sterilization methods need to be assessed and adjusted to each specific case in order
to preserve the bioactivity of the nanoparticle-conjugated antibodies and to prolong
the lifetime of the bound antibodies (Fig. 1.3 ).
1.6 Applications of the Ab-NP Conjugates in In Vivo
Studies: From Imaging to Therapy
Before proceeding with the presentation of the Ab-NP-based applicative studies, a
brief premise will follow in order to frame the overview of this section. The term
“in vivo” is generally referred to studies performed with living whole animals,
preferably mammals, in which structure and organization of the organs, progression
of diseases, and the overall response to an external treatment can be associated to
those of humans. In vivo testing is a crucial and indispensable step for the validation
of new pharmaceuticals and to provide new medical insights prior to clinical
testing. Mice are the most commonly used animal models in research because of
the low cost, ease of handling, availability, and short life, which allows to monitor
the effects of a treatment on a reasonable time scale. On the other hand, cancer is
certainly the most studied human disease, at both clinical and preclinical levels
because of its high incidence and uncertain prognosis. Despite improved under-
standing of cancer biology and significant progress in detection technologies and
therapeutic protocols, major concerns are due to late and invasive cancer diagnosis,
poor efficacy of the therapies, and high percentage of relapse (DePinho 2000 ; Hahn
and Weinberg 2002 ; Sherr 2004 ). Most of the current treatments cannot discrimi-
nate between tumor and healthy cells, leading to systemic toxicity and low accu-
mulation of the treating agents at the target site.