Biomedical Engineering Reference
In-Depth Information
(PLA), poly-glycolic acid (PGA), poly-lactic glycolic acid (PLGA), poly(
ε
-
caprolactone), polyglutamic acid, and polymalic acid, and their copolymers
are among the most extensively studied.
142
These polymers are usable for NP
formulation, biocompatible, and have been used in surgery for 30 years and
have shown biocompatibility.
146
The drug release rate that is controlled by the
polymer degradation can be controlled by adjusting the molecular mass of the
PNPs; in the case of copolymers, their composition and microstructure can be
used to control the drug release.
147
2.3.2.1 Synthesis of PLGA NPs
148
A solvent diffusion method is used to prepare PLGA NPs. The protocol is as
follows:
148
(1)
PLGA, 50 mg, was dissolved in 3.0 mL acetone.
(2)
This PLGA solution was added to 30 mL of 0.2% poly(ethylene-
alt
-maleic
anhydride (PEMA) through a syringe pump at a rate of 20 mL/h with stir-
ring at 200 rpm in a hood to evaporate the acetone. PEMA was utilized as a
surfactant to increase the number of carboxyl groups on the particles.
149
(3)
Collect the NPs by centrifugation at 15,000 rpm for 45 min.
(4)
Wash the NPs with double-distilled water three times.
The sizes and zeta potentials of the PLGA NPs can be determined using a DLS
system.
2.3.2.2 Synthesis of PLA NPs
150
Materials
: D,L-lactide (from Aldrich, Milwakee, USA); monomethoxy PEG
(
M
w
5000 Da) and stannous octoate (Sigma Chemical, St Louis, USA). Puri-
fied tetanus toxoid (TT,
M
w
150,000 Da, 85-95% monomeric) dissolved at 10
mg/mL in PBS, pH 7.4 (Massachusetts Biological Laboratories, Boston, MA).
Cholic acid (sodium salt, purity 99%), pepsin A from porcine stomach mucosa,
and pancreatin from porcine pancreas (Sigma Quı´mica, Madrid, Spain).
The polymer NPs were prepared by the double emulsion technique as previ-
ously described.
151,152
(1)
Place 50 mL of the TT solution and emulsify in a 1-mL solution of PLA or
PLA-PEG (50 mg) in ethyl acetate by sonication (Branson 250, Sonifier
®
)
for 15 s (20 W).
(2)
Add 2 mL of aqueous sodium cholate solution (1% w/v).
(3)
Sonicate the emulsion for 15 s (20 W).
(4)
Dilute the emulsion in 100 mL sodium cholate solution (0.3% w/v).
(5)
Evaporate the solvent rapidly under vacuum (Rotavapor R-114, Buchi,
Switzerland).
(6)
Collect the NPs by centrifugation at 22,000
g
for 30 min (Avanti™ 30,
Beckman, Spain).
(7)
Purify by washing three times with double-distilled water.
