Polysaccharides as Nanomaterials for Therapeutics - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 148

blocked by both free HA and anti-CD44 antibodies. Liposome uptake
was dependent on ligand density; however, as little as 0.1 HA molar
percent managed to facilitate targeting. In addition, doxorubicin
encapsulated in the oligosaccharide-decorated liposomes was
significantly more cytotoxic to CD44 overexpression cells in
comparison with free drug.

Figure 5.4 Hyaluronan-coated nanoparticles: (A) Hyaluronan-coated
liposome (tHA-LIP). (B) Paclitaxel-clusters coated with hyaluronan (PTX-
GAGs). See also Color Insert.

Another clinically relevant advantage of the liposomal HA coat
is cryoprotection [142]. Cryoprotection provides the liposomes
with a longer shelf life since it prevents the reversion of lyophilized
unilamellar liposomes to multilamellar liposomes upon rehydration.
The tested lyophilized tHA-LIP demonstrated the ability to retain
the same dimensions, zeta potentials, encapsulation efficiencies and
half-life of drug release of the original systems upon redispersion. HA
cryoprotects possibly by providing substitute structure-stabilizing
H-bonds.

5.5.3 Heparin- and Dextran-Coated Nanoparticles

Heparin has been shown to inhibit complement activation at diff erent
stages by increasing the activity of protein H [151]. Since the activation
of the complement system plays an important role in opsonization
and uptake of particles by the mononuclear phagocyte system (MPS),
surface modification of nanoparticles with heparin seemed promising
[151]. And indeed, a heparin coat significantly promoted long-term