Biomaterial-Based Particulate Drug Carriers - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 8

or semi-synthetic, in which case selections of desired chain length
and degree of saturation are possible.
For protein-based microspheres and nanospheres , serum albumin
or gelatin seem to be the most-frequent raw material, but other proteins,
single or mixtures, can also be selected for the task [21-24].
Alginate and chitosan are prominent polysaccharides used as
raw materials for drug carriers [25-27].
Then there are also carriers that contain more than one type of
biomaterial: particles derived from living systems (Figure 1.2); new
carriers, made from a mixture of several biological components, such
as the collagomers (containing collagen and lipid) and gagomers
(containing hyaluronan and lipids), developed by our group [11-15].

1.2.2 Utilizing Nature's Sites for Targeting and

High-Affinity Binding

In the context of targeting, the ability of a drug-carrier formulation
to recognize and bind with high affinity to the target has already
been discussed in this chapter (Section 1.1.4). These recognition and
binding are key critical requirements to achieve successful therapy.
Using biomaterial-based drug carriers opens the door to
utilize the wide repertoire nature provides of sites — membrane-
embedded receptors, extracellular matrix components — that off er
recognition, specificity, and high-affinity binding. To simplify matters,
we will use from here on the term receptor as generic for all types
of recognition and binding sites off ered by the target, whether they
are a biochemically defined receptor or a protein weaved within the
ECM, or others. In the context of targeting, the term specificity has
dual meaning: specificity of the receptor to a given ligand serving
as the targeting agent; specificity of the receptor in terms of its
uniqueness to the therapeutic target. To diff erentiate between the
two, we will reserve the term “specificity” for the interaction of a
targeting agent with its receptor and apply the term “unique” to the
presence of a particular receptor at the therapeutic target compared
with the other locations within the living system.
The biological targeting agents can play a single or dual role
in biomaterial-based drug carriers. In the single role, which is the
prevalent mode, the targeting agent is attached to the carrier in a bond
that should be sufficiently stable to avoid separation of carrier and
targeter before reaching the target. Monoclonal antibodies (mAbs)