Biomaterial-Based Particulate Drug Carriers - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 7

an antibody against a specific membrane-embedded receptors, in a
given cell line — is brought here as an example [16-20]. Incubating
immunoliposomes with cells that express the specific receptor
usually results in high affinity binding, whereas blocking the
receptors prior to binding with free antibody or administering such
liposomes to cells that do not express the specific receptor results in
negligible binding [16-20]. Such results are important experimental
evidence for a key requirement of carrier-mediated drug targeting
— the recognition and high affinity binding between the liposome-
bound Ab and the specific receptor. Such results may even have
higher relevance if local administration is intended. In such cases,
the cell monolayer becomes a model system for the designated
tissue. In vitro binding and recognition are not, however, evidence
of drug targeting that should, as already discussed in this section, be
pursued in an animal model.

1.2 Biomaterial-Based Particulate Drug Carriers:

Advantages and Drawbacks

1.2.1 A Wide Choice of Raw Materials

The continuous ability to make new synthetic raw materials, in
addition to those already available, makes the pool of synthetic raw
materials available for the construction of drug carriers practically
infinite. Against this background, claiming the wide choice of
biological raw material for drug carriers may seem odd. Yet, we wish
to point out that the existing pool is quite large.
For liposomes and other lipid-based particles , there is a wide
choice of lipids for liposomes and other lipid-based carriers. Such
carriers can be made from a single lipid: phospholipids such as
phosphatidylcholine, phosphatidylserine, phosphatidylinositol,
and others (although not from phosphatidylethanolamine alone);
sphingomyelin, ceramides [1, 3, 11, 14-21]. Liposomes can also be
made from a mixture of lipids, and in that case, cholesterol, fatty acids,
and phosphatidylethanolamine can be included in the formulation
[1, 3, 11, 14-21]. For a given lipid, there are further choices
depending on its source: biological, in which case the hydrocarbon
chains can be a mixture of sizes and degrees of saturation; synthetic