Biomedical Engineering Reference
In-Depth Information
(2)
Filter the obtained suspension with a filter paper and incubate in buf-
fer solution of pH = 4.5 for 24 h using a dialysis membrane bag for
characterization.
(3)
Add PAA 1 mL 0.02% PAA (
M
n
= 100 kDa) solution dropwise to 5 mL
0.02% CS solution (CS with molecular weight 80 kDa in 1% (w/v) acetic
acid solution) under magnetic stirrer.
2.3.3.3 Preparation of Drug-Loaded CS NPs
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For the most part, liposomes are used in drug encapsulation. The following
protocol describes the preparation of drug-loaded NPs:
(1)
Dissolve 50 mg of SP in 50-mL CS-PAA NPs that were prepared by polym-
erization of AA in CS solution with the CS molecular weight 80 kDa and
incubate for 48 h.
(2)
Separate the NPs from the aqueous phase by ultracentrifugation (Ultra
ProTM 80, Du Pont) with 50,000 rpm at 4 °C for 40 min.
(3)
Wash the SP loaded CS-PAA NPs with acetone three times.
(4)
Freeze in liquid nitrogen and lyophilize to obtain freeze-dried SP loaded
CS-PAA NPs.
2.3.4 Micelles
Micelles are spherical amphiphilic structures that have a hydrophobic core and a
hydrophilic shell.
155
The hydrophilic shell makes the micelle water soluble that
allows for intravenous delivery while the hydrophobic core carries a payload
of drug for therapy.
156
The nanoscale dimensions (diameter less than 50 nm)
157
and the hydrophilic shell of polymeric micelles serve as protection from elimi-
nation by the reticulo-endothelial system, thereby increasing their circulation
time and ability to deliver the drug to the target.
Polymeric micelles are biocompatible, highly stable in vitro and in vivo,
and can dissolve a broad variety of poorly soluble pharmaceuticals. This capa-
bility of micelles has led to the development of several types of drug-loaded
micelles that are currently being tested in preclinical and clinical trials.
142,157
Among polymeric micelles, a special group is formed by lipid-core micelles,
i.e., micelles formed by conjugates of soluble copolymers with lipids (such as
PEG-PE conjugate). Tumor may be targeted with micelles by exploiting the
enhanced permeability and retention (EPR) effect, by making micelles of stim-
uli-responsive amphiphilic block copolymers, or by attaching specific targeting
ligand molecules to the micelle surface.
158
2.4 CARBON NANOPLATFORMS
CNTs are among the most widely discussed NMs
159-169
and can be fabricated
into biodegradable nanostructures (cylindrical buckytubes). These structures
