Design and Development of Theranostic Nanomedicines - Nanotechnology for Biomedical Imaging and Diagnostics - page 440

like other types of theranostic nanoparticles, dendrimers can be delivered to a
tumor region through both passive and active targeting mechanisms. For example,
several drug-loaded dendrimers have been reported to be efficiently uptaken in
prostate cancers through epr effect [151, 152]. For active targeting, many dendrimers
that specifically target receptors overexpressed by cancers have been developed
through bioconjugation with targeting molecules on the surface. For example,
paMaM has been conjugated with antibodies [153], aptamers [154], and peptides
[155] to target psMa and α v β 3 -integrin overexpressed by prostate cancer cells.
Two strategies have been reported for dendrimer synthesis, including divergent
and convergent growth methods [156]. in the divergent method, synthesis begins
with a desired functional core, and a branch component is constructed stepwise
around the core to produce a core-shell structure [157]. Most commercially avail-
able dendrimers, such as paMaM and ppi dendrimers, are synthesized using the
divergent method. The convergent method starts with synthesis of the peripheral
branches (dendrons) and proceeds inward to a reactive focal point at the root [157].
one example of dendrimers developed using convergent approach is dendritic
poly(ether-imide)s [158].
The ability to carry various biologically active molecules in a well-defined and
controlled manner makes dendrimers stand out as a promising theranostic platform.
a recent study reported by al-Jamal et al . uses a g6 polylysine dendrimer loaded
with DoX (DoX-DM) as the theranostic agent [159]. The retention of DoX-DM
was monitored by live whole-animal fluorescence imaging using fluorescence of
DoX as the signal. in a lung cancer xenograft mouse model, DoX-DM showed
enhanced therapeutic efficacy than free DoX.

15.4.2 polymeric nanoparticles

some would refer to the end of twentieth and beginning of the twenty-first century as
the era of polymers. polymers are everywhere in our lives, from a coffee cup to a seat
on an airplane to medicines and devices we use every day. no surprise, polymers
became materials of choice for nanosystem development in drug delivery and
imaging in the past several decades. in fact, polymers have been mentioned so far
throughout this chapter but mostly in supporting roles.
here, we'd discuss polymers in more depth and how they seem to be able to carry
on the biggest weight when it comes to theranostic nanomedicine design. in their
recent review on polymerasomes (or polymeric vesicles), De oliveira et al . [160]
argue that polymers are here to help us solve remaining problems in modern therapeu-
tics such as efficacy, specificity, and controlled release of drugs to diseased tissues.
There is yet much left to be done, and polymers may offer the most. polymerasomes
can be designed to respond to specific triggers (ph, temperature, magnetic field),
carry drugs and targeting agents, and include multiple imaging modalities [160]. in
that respect, polymerasomes are similar to liposomes but with one key difference—
polymers allow for much more versatile chemistry and engineering over liposomes
built primarily with lipids and also give us higher chemical stability and good bio-
degradable properties. so here, we discuss polymers in respect of their role as a