Biomaterial-Based Particulate Drug Carriers - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 10

receptor expression between cancer and normal cells may not be
enough to ensure that carriers endowed by these targeters will be
sufficiently selective to the cancer cells over normal cells [29, 33,
37-38]. In summary, target-uniqueness needs to be verified case by
case, and drive targeter selection.

1.2.3 Lower Risks of Adverse Eff ects, Toxicity, and

Undesirable Immune Responses

Carrier essential requirements, designed to avoid problems
introduced by the carrier itself, have been discussed earlier in
this chapter (Section 1.1.2 and Figure 1.2). In these respects,
biomaterial-based drug carriers provide significant potential
advantages over carriers made of synthetic materials, or a mix of
synthetic and biological materials. The biomaterial-based carriers
— including targeting moieties of biological origin — are expected
to be biocompatible and biodegradable. Carriers composed from,
or containing, non-biological matter may have compatibility issues
and, if not biodegradable, may require invasive procedures for
their removal post drug-load delivery as, for example, in the case
of antibiotic-loaded cement particles applied to control/prevent
osteomyelitis [41]. Compared with carriers containing synthetic
materials, the biomaterial-based carriers have lower potential to
be toxic, to generate adverse eff ects, and to stimulate the immune
system in undesirable directions. The boundary between recognition
as self and non-self is delicate as can be exemplified by regular vs.
cationic liposomes. Regular liposomes made from biological lipids,
containing, for example, PC, cholesterol, and PE, are safe in all
respects discussed here (see also Figure 1.2) as are also liposomes
of the same composition carrying HA as the targeting agent [13, 15,
30, 31, 39]. Cationic liposomes containing these biological lipids, but
also a synthetic cationic lipid are toxic and immunogenic [42-44].

1.2.4 Drawbacks of Biomaterial-Based Particulate

Drug Carriers

Despite their many advantages, discussed in the previous sections,
there are drawbacks to particulate carriers made from biological
materials. The shortcomings start from the very fact that the raw
materials are of biological origin. These include: material scarcity;