Chemistry Reference
In-Depth Information
inner aqueous channels, revealed a similar diffusion profi le with the same
slope, 1.2
0.1 h
− 1/2
. PEN, which populates the outer interfacial region, is less
disturbed in its diffusion, causing a release profi le with a slope of 2 h
− 1/2
. Nev-
ertheless, this interesting mechanism of the drug migration from the H
II
meso-
phase in the presence of CPP molecules co-solubilized within the mesophase
should be further investigated.
±
8.4
SOLUBILIZATION AND DELIVERY OF BIOMACROMOLECULES
Solubilization of biomacromolecules into LLCs is of great practical interest.
Mezzenga et al. (2005) investigated the effects of confi ning polymeric forms
of glucose in the water domains of liquid crystals composed of monoglyceride
and water solutions. Using rheological and SAXS methods, the authors studied
the effect of sugar concentration and molecular weight on cubic-to-H
II
transi-
tions by further solubilization of maltose and dextran I in the system. It was
found that higher concentrations of sugars resulted in a decrease of the Pn3m-
H
II
transition temperature, as a consequence of the Hofmeister effect. However,
no dependence on molecular weight of the sugar was observed. In the case
of a polymeric sugar, as soon as the end-to-end distance of the polymer
approached the diameter of water channels, its molecular weight made it more
diffi cult for the guest molecule to fi t within narrow water channels. Dextrans
of larger molecular weights than dextran I did not fi t into the water channels
of the cubic phases, inducing a phase separation. Moreover, it was noticed that
dextran I, solubilized into the Ia3d phase channels, induced the appearance of
a Pn3m phase, which possesses larger water channels. Hence, when the chain
end-to-end distance of the polysaccharide approached the diameter of the
water channels, it induced phase transitions toward structures with different
topologies, thus enhancing the solubilization capacity of large sugars.
Peptides and proteins are increasingly considered for the development
of new therapeutic compounds (Dass and Choong, 2006; Kumar et al., 2006).
Peptides of various sizes are currently tested for a broad spectrum of diseases,
including skin cancer, acne, psoriasis, hypertension, hepatitis, and rheumatism.
These biomacromolecules are usually found to be very effective, and in most
cases low doses of them are needed for good medical treatment. Nevertheless,
when delivered orally, these peptides and proteins are susceptible to cleavage
by various enzymes, mainly the human digestive proteases, leading to practi-
cally poor bioavailability and poor pharmaceutical effi cacy. As a result of these
critical limitations, excessively large doses of the peptide-based drugs are
usually required to obtain therapeutic effects in vivo, which in turn often cause
a wide range of hazardous side effects (Dass and Choong, 2006; Kumar et al.,
2006). This is the main reason the medical application of these otherwise high
potential therapeutics is currently very limited, and even those few that are
used at the present time are far from being effi cient. In this respect, LLCs
seem to be promising candidates as alternative delivery means for various
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