The results accrued in the last few years have clearly showed that recombinant antibodies, and specifically single-
domain antibodies, represent valid alternatives to conventional IgGs for in vivo imaging. It does not simply mean that
antibody fragments can substitute full-length antibodies, but that they are substantially more suitable for some applications
and can perform other functions for which no real alternative is available. Brain imaging with multi-functional probes is
an evident example, but the promising results obtained with micro-PET and –SPECT in murine models could lead in short
time to a revolutionary change in clinical diagnostics. Brilliant applications of single-domain antibody-dependent imaging
have enabled us to understand how the tracer mass and avidity can be engineered to modulate pharmacokinetic features
such as clearance, tumor penetration, and binding affinity with the aim of optimizing specific responses. The potential of
these reagents and the increasing interest for them is evidenced by the exponential growth of publications and the multiplication
of the proposed applications in which they are used. This review wishes to provide an update of this fast moving
subject and to indicate what may be the next foreseeable technical progress.
Keywords: Antibody functionalization, fresh tumor cells, imaging, nanobodies, PET/SPECT, phage display panning, singledomain
antibodies, tumor clonal variability.
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