Biomaterial-Based Particulate Drug Carriers - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 11

isolation from the biological source and purification to the degree
required for therapeutic agents may be difficult to achieve and cause
extensive material loss: batch-to-batch reproducibility of each raw
material is also a tough call. Quite obviously, not every biomaterial
has to be isolated from the biological source, some — for example
many types of lipids that constitute a major type of material in
biomaterial-based carrier — are commercially available. In such
cases, the raw material issues are similar to those of regular synthetic
materials, and discussion of such issues is beyond the scope of the
present communication. Another aspect of biological raw material
that can cause problems in the biological milieu is species specificity,
especially for carrier components that are proteins. Conventional
phospholipids are usually less restricting in that respect — for example,
phosphatidylcholine obtained from soybean can be used without
immune limitations for drug carriers administered to mammals. The
least restricting in this respect is hyaluronan. It has been approved for
clinic use in ocular surgery and osteoarthritis treatment, from both
non-mammalian and mammalian sources. As to the biomaterial-based
particle itself, drawbacks include: the need to develop the production
processes from the inventing lab to industrial levels; sterilization
processes; batch-to-batch reproducibility and size uniformity.
A common thread throughout the drawbacks, whether arising
from the raw materials or the particle, are high costs, which may
significantly exceed those of drug carriers made from synthetic
materials.
We would like to stress, however, that not all drawbacks are
encountered with each biomaterial-based particulate drug carrier.
Weighing the advantages over the drawbacks should be done on
a case-by-case basis, and frequently the benefits outweigh the
limitations.

1.3 Particle Size, Route of Administration, and

Therapeutic Needs

1.3.1 The Conceptual Approach and Definitions of

Passive and Active Targeting

The conceptual approach discussed in this section concerns the
selection of particle species and dimensions, for carrier-mediated