Biomaterial-Based Particulate Drug Carriers - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 14

Local, intra-tumoral injection of biomaterial-based particulate
carriers such as liposomes has been applied in cancer therapy [60,
61]. Local injections can be applied for therapeutic indications other
than cancer, such as infectious diseases, osteoarthritis, and local
anesthesia. The benefits of replacing treatment with free drug, with
drug-carrier formulations, with emphasis on biomaterial-based
particulate carriers has already been discussed in the previous
sections. For treatments of chronic diseases by local injections, drug-
carrier formulations may provide an additional benefit by extending
the time intervals between injections.
Local injections still require local targeting (Figure 1.4). To that
end, the carrier should localize close to the cells in which the drug
operates, bind with high affinity, and remain at the site performing as
a slow-release drug depot on a time scale of several weeks or more.
Needless to say, for carriers expected to remain within the body for
prolonged periods, the properties of biomaterial-based carriers
(Figure 1.2) are particularly advantageous. As to favored particle size,
for these types of treatments, microparticles are probably preferable
to nanoparticles. The larger particles usually provide for higher drug
loads and do better in avoiding internalization within cells. Such
evasion is obviously needed, since internalization of a drug-carrier will
lead to relatively fast release of the drug at once, thus losing the slow-
release drug-depot performance. Treatment of osteoarthritis (OA)
by intra-articular injection to an inflamed rat knee is brought here to
illustrate additional potential benefits for carrier-mediated therapy
using microparticles. A single injection of an NSAID encapsulated in
collagomers (5 μm diameter) or of an NSAID and a corticosteroid co-
encapsulated in the same hyaluronan-coated MLV (1-2 μm diameter)
reduced inflammation over a 3 week time from two- to fourfold better
than untreated controls and free drug [11, 12, 14].

1.3.4 Oral Administration of Drug-Carrier Formulations

The oral route is among the most patient-friendly and the prevailing
option (when possible) for drugs that need to reach the circulation
either as the final destination or for distribution to their targets. The
oral route is not currently feasible for drugs that are biologicals—
peptides, proteins, and nucleic acids. Such drugs, when administered
in free form, do not survive the hostile gastrointestinal tract (GIT)
intact and in active form, suff ering acutely from deficiencies of