Biomedical Engineering Reference
In-Depth Information
2.3.2.3 Characterization of Polymer NMs
The particle size and zeta potential of NPs can be determined, respectively, by
photon correlation spectroscopy (PCS) and laser Doppler anemometry (LDA)
using a Mastersizer
®
(Malvern Instruments, UK). The copolymer composition
and number-average molecular weight can be studied by
1
H NMR spectroscopy
at 400 MHz using D-chloroform as a solvent.
2.3.3 Chitosan
153
The chitosan for this methodology was first refined twice by dissolving it in
dilute acetic acid solution, filtered, precipitated with aqueous NaOH, and dried
in vacuum at RT
153
resulting in 90% deacetylation. The weight-average molecu-
lar weights of chitosan were 40, 80, 100, 200, and 300 kDa that were established
by viscometric methods.
154
The potassium persulfate (K
2
S
2
O
8
) was purified by
dissolving in DI water and recrystallized water and acrylic acid (AA) was dis-
tilled under reduced pressure in nitrogen atmosphere. Silk peptide powder was
used as the model drug.
2.3.3.1 Preparation of Chitosan-Poly(Acrylic Acid) (CS-PAA) NPs
by Polymerization
153
The following protocol is followed for the preparation of CS-PAA.
(1)
Dissolve chitosan in 50-mL AA in the ratio of 1:1 ([aminoglucoside
units]:[AA]) with magnetic stirring. (Maintain the AA in all experiments at
3 mmol).
(2)
When the solution becomes clear, add 0.1 mmol of K
2
S
2
O
8
.
(3)
Maintain the pH at 4.0.
(4)
Heat to 70 °C under a stream of nitrogen and magnetic stirring until an
opalescent suspension is produced.
(5)
Cool down the reaction to RT.
(6)
Filter the reaction mixture with filter paper to remove any polymer aggrega-
tion.
(7)
Dialyze in a buffer solution of pH 4.5 for 24 h using a dialysis membrane
bag with a molecular weight cut-off of 10 kDa.
2.3.3.2 Preparation of CS-PAA NPs by Dropping Method
153
CS-PAA NPs can also be prepared by mixing positively charged CS and nega-
tively charged PAA using the dropping method as follows:
(1)
Add 1 mL of 0.02% CS solution (CS with a molecular weight of 80 kDa
dissolved in 1% (w/v)acetic acid solution) dropwise to 5 mL 0.02% PAA
(
M
n
= 100 kDa) aqueous solution with magnetic stirring to form the
opalescent suspension.
