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Formulation and in vitro Evaluation of Quercetin Loaded
Polymeric Micelles
Composed of Pluronic P123 and TPGS
Liyan Zhao1,, Yikang Shi2,, Shaohua Zou3,, Min Sun1, Lingbing
Li1, and Guangxi Zhai1*
1 Department of Pharmaceutics, College of Pharmacy, Shandong
University, Jinan 250012, China
2 Institute of Biochemical and Biotechnological Drug, School of
Pharmaceutical Science, Shandong
University, Jinan 250012, China
3
Department of Pharmacy, Yantai Yuhuangding Hospital, Yantai
26400, China
These authors contributed equally to the work
* Corresponding author:
Guangxi Zhai, Ph.D.
Professor
Department of Pharmaceutics
College of Pharmacy, Shandong University
44 Wenhua Xilu, Jinan 250012, China
Tel: (86) 531-8838,2015.
E-mail: [email protected]
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Abstract
The objective of this study was to develop a polymeric delivery
system to improve the
solubility and biological activity of Quercetin (QT). QT loaded
mixed micelles,
composed of Pluronic P123 (P123) and D-a-tocopheryl polyethylene
glycol succinate
(TPGS) with proportion of 7:3 (QT-P/T), were prepared by
thin-film hydration
method. The average size of the mixed micelles was 18.43 nm, and
the encapsulating
efficiency for QT was 88.94 3.71%, drug-loading was 10.59 0.38%.
The solubility
of QT in QT-P/T was 5.56 mg/mL, which was about 2738-fold that
of crude QT in
water. Compared with the QT propylene glycol solution, the in
vitro release of QT
from QT-P/T presented the sustained-release property. The in
vitro cytotoxicity assay
showed that the IC50
values on MCF-7 cells for QT-P/T and QT loaded P123 micelles
(QT-P123) were 7.13 g/mL and 10.73 g/mL, respectively, while
7.23 g/mL and
14.47 g/mL on MCF-7/ADR cells. It could be concluded from the
results that
P123/TPGS mixed micelles might serve as a pharmaceutical
nanocarrier with
improved solubility and biological activity of QT.
Keywords: Quercetin, Polymeric Micelle, Pluronic P123, TPGS,
Cytotoxicity
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INTRODUCTION
Quercetin (QT, Fig.1), extracted and isolated from Sophora
japonica L, is the major
representative of the avonoid , and has a broad range of
biological activities and
pharmacological actions such as anti-oxidant activity,1-2
anti-inammatory,3-4
anti-diabete,5 anti-neural disorders,6 anti-tumor and
anti-proliferative effects on a
variety of human cancer cell lines.7-8 The in vitro and in vivo
studies have
demonstrated that QT may inhibit cancer cell growth by binding
to type II receptors,
which are over-expressed in a wide range of tumor tissues.9 In
spite of this wide
spectrum of pharmacological properties, the clinical studies of
QT have been
hampered due to the water insolubility (0.17-7.7 g/mL).10-12 In
order to improve its
solubility, QT has been encapsulated in cyclodextrins,13
liposomes,14 and chitosan
nanoparticles.
Recent studies show that encapsulation of hydrophobic drugs
inside polymeric
micelles is one of the most attractive alternatives.
15
16 Due to the nanosize and a
core-shell structure, polymeric micelles have been developed as
drug delivery systems
for various agents in therapeutic and diagnostic
applications,17-19 and as one promising
nanomedicine based technology, polymeric micelles as carriers
for anticancer drugs
have been evaluated in several clinical trials.20-21 For
example, SP1049C containing
doxorubicin in the mixed micelles of Pluronics L61 and F127 is
the first anti-cancer
micellar formulation to reach clinic evaluation and is
undergoing Phase II clinical
trials.
Pluronic P123 (P123), composed of PEO
22-23
20-PPO68-PEO20, is one of the most
common representatives of Pluronic copolymer.24 Here EO denotes
oxyethylene
OCH2CH2, and PO denotes oxypropylene OCH2CH(CH3). It is a
prominent feature
for P123 that can self-assemble into spherical micelle structure
constructed by EO as
a hydrophilic outer shell and PO as a hydrophobic inner core.25
The PO core can serve
as a pool and the hydrophobic drug can be incorporated into the
hydrophobic PO
core, while the hydrophilic corona maintains the dispersion
stability of Pluronic
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micelles. It was also demonstrated that P123 had a significant
cytotoxicity in the
multidrug resistant (MDR) cell lines to doxorubicin due to
inhibition of the
P-glycoprotein (P-gp) drug efflux transport system that was
over-expressed in these
cells.
D-a-tocopheryl polyethylene glycol succinate (TPGS) has been
approved by FDA
as a water-soluble vitamin E nutritional supplement and drug
delivery vehicle.
26
27 It is
reported that TPGS can enhance the solubility of poorly soluble
drugs by micellar
solubilization.28 Recently, it is discovered that TPGS is one of
P-gp inhibitory
excipients.29-30 Co-administrating with TPGS, the cellular
uptake of doxorubicin on
Caco-2 cells is increased.31 And for amprenavir, a marketed
antiviral drug, TPGS has
been used clinically to enhance the bioavailability of the
drug.
In the present work, QT loaded P123/TPGS mixed micelles were
prepared by
thin-film hydration method. The physicochemical properties and
in vitro cytotoxicity
of the drug-loaded micelles were investigated.
32
MATERIALS AND METHODS
Materials
QT was purchased from Xian Senmu Biological Technology Co. Ltd
(Xian, China).
TPGS was supplied by Wuhan Yuancheng Co. Ltd (Wuhan, China).
P123,
3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide
(MTT), trypsin and
EDTA were purchased from Sigma-Aldrich (St. Louis, MO, USA).
Human breast
carcinoma cell line MCF-7 and its adriamycin-resistant
counterpart MCF-7/ADR
were donated by Institute of Biochemical and Biotechnological
Drug, School of
Pharmaceutical Science, Shandong University. Penicillin
streptomycin, RPMI 1640
and fetal bovine serum (FBS) were purchased from Gibco BRL
(Gaithersberg, MD,
USA). All other chemicals were of analytical grade.
Preparation of QT Loaded Micelles
QT loaded micelles were prepared by thin-film hydration
method.33-34 Briefly, 24mg
of QT and 10 mM of copolymer carriers composed of P123 and TPGS
with different
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proportions were dissolved in alcohol. The solution was
subsequently evaporated
under reduced pressure by rotary vacuum evaporation to obtain a
thin film of
drug/polymer mixture, and the film was further dried over night
at room temperature
to remove any residual. After that, the obtained film was
hydrated in 4mL of
de-ionized water under magnetic stirring at room temperature to
form a micellar
suspension. Non-incorporated crystalline drug was separated by
filtration through a
0.22 m lter membrane , and a yellow clear solution of QT loaded
mixed micelles
was obtained.
QT loaded P123 micelles (QT-P123) and empty micelles were
prepared according
to the same procedure.
Characterization of Micelles
Particle Size Distribution
Particle size distributions and mean diameters of the prepared
micelles were measured
using the BI-200SM based on the light dynamic scattering method
(DLS, Brookhaven
Instruments Corporation, USA) at a scattering angle of 90 at
room temperature. Each
freshly prepared sample was placed into a quartz cuvette without
additional treatment.
The size distributions were extracted from the autocorrelation
functions by the
CONTIN program.36
For each sample, the size was measured in triplicate.
Surface Morphology
The morphology of the QT-P/T was observed under transmission
electron microscope
(TEM, JEM-1200EX, JEOL, Tokyo, Japan), and the accelerating
voltage was 100 kv.
To prepare the TEM samples, a drop of micellar solution was
placed on a copper grid
and stained with phosphotungstic acid solution (2%, w/v) about
15 s. Subsequently
the sample was allowed to dry slowly in air and then examined
under TEM.
Zeta-potential
Zeta-potential of different micelle solution was determined
using Zeta Potential
Analyzer Instrument (Brookhaven Instruments Corporation, USA).
For each sample,
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zeta-potential measurement was repeated eight times.
Drug-loading and Entrapment Efficiency
The concentration of QT in the micelles was determined with
UV-Vis
spectrophotometer (UV-2102, Shanghai Instrument Ltd, China) at a
wavelength of
374 nm. The micellar solution was suitably diluted with alcohol
prior to determination.
The drug-loading (DL%) and entrapment efficiency (EE%) of QT in
polymeric
micelles were calculated from the following equations:
DL% =
24,37
weight of the drug in micellesweight of the feeding polymer and
drug
EE% =
100% (1)
weight of the drug in micellesweight of the feeding drug
100% (2)
Critical Micelle Concentration (CMC)
In this study, CMC was analyzed by a fluorescence probe
technique using pyrene as a
hydrophobic probe.38-40 The concentration of encapsulated pyrene
in micelle phase
was determined using F-2500 fluorescence spectrometer (Hitachi,
Japan). Pyrene
dissolved in acetone was added to empty vials. After acetone
evaporation, a series of
micellar solutions were added to the vials. The final pyrene
concentration was 6.0
107
M, slightly below the saturation concentration of pyrene in
water at 25 C, and
the mixed solution was incubated overnight in the dark. All
samples were excited at
334 nm, and fluorescence spectra were recorded between 350 nm
and 500 nm. The
excitation and emission slit widths were set at 5 nm. Upon
formation of micelles,
pyrene would move into the inside of the micelles from the
aqueous phase, which
could result in an alteration in the intensity ratio of
I372/I383.
Solubility of QT in Water or Polymer Micelle Solution
The solubility of QT in water was determined as follows,
excessive crude QT powder
was added to 10 mL of de-ionized water, and then the resulting
mixture was stirred at
100 rpm at 25 C for 72 h and centrifuged at 10000 rpm for 15
min. The supernatant
was taken and filtrated through a 0.22 m lter membrane, and
subsequent ly, the
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content of QT in the obtained filtrate was analyzed with UV
method at 374 nm.
1 mL of QT loaded micelle solution was suitably diluted with
alcohol, and then the
resulting solution was analyzed with UV method at 374 nm, the
concentration of QT
in micelle solution was calculated and the solubility of QT in
polymer micelle
solution was obtained.
In vitro Release of QT from Micelles
The release of QT from the micelles was investigated by dialysis
method with 0.5%
Tween 80 solution as release medium. The solution containing 3.0
mg of QT was
introduced into a pre-swollen dialysis tube with a MWCO of
8KD-12KD (Xian
Luosenbo Co. Ltd, Xian, China), and the dialysis tube was
immersed into 200 mL
release medium at 370.5C with stirring speed at 100 rpm. At
predetermined time
intervals, 4 mL of the dissolution medium was withdrawn and the
same volume of
fresh medium was added. Then, the amount of released QT was
measured by UV-Vis
spectrophotometer at 374 nm, and the cumulative release
percentage (Q%) was
calculated. For comparison, the release of QT from propylene
glycol solution was
conducted under the same conditions.
41
Cytotoxicity in vitro
The cytotoxicity in vitro of drug loaded micelles was evaluated
on MCF-7 and
MCF-7/ADR using the MTT method.30,34,42 The cells were cultured
in RPMI-1640
medium, which was supplemented with 2 mM l-glutamine, 10% (v/v)
FBS, 100
units/mL penicillin G, 0.25 g/mL amphotericin B, and 100 g/mL
streptomicin at 37
C in a humidified 5% CO2
MCF-7 cell lines were seeded at the density of 310
sterile incubator. The medium was changed once every
two days. 3 cells per well in 96-well
plates and 8103 cells per well for MCF-7/ADR cells. After 24 h
incubation, 100 L
of medium containing the treatment agents such as QT DMSO
solution (the final
concentration of DMSO kept below 0.2%), empty micellar solutions
and drug loaded
micellar solutions of various concentrations was added. The
concentration of QT
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ranged from 0.5 to 60 g/mL. After additional 48 h incubation,
the cells were washed
twice with phosphate buffer saline (PBS). Subsequently, the
growth medium was
refreshed and 20 L of MTT solution (5 mg/mL) was added to each
well. The plates
were incubated at 37 C for another 4 h and the medium was
removed again. The
intracellular metabolized product formazan crystals were
dissolved by addition of 150
L of DMSO to each well. The absorbance was measured using a
multiwell scanning
spectrophotometer Model 680 (Bio-Rad, USA) with the test
wavelength at 570 nm
and the reference wavelength at 630 nm. Cell viability was
calculated by [absorbance
of cells exposed to micelles or drug] / [absorbance of cells
cultured without micelles
or drug] in percentage.
RESULTS AND DISCUSSION
Particle Size Distribution
The particle size will directly affect the bio-distribution and
circulation time in vivo of
the carriers.43
The micelle size obtained by DLS depends on both the block
copolymer
composition and the drug loading. After the micelle was formed,
the micelle size was
mainly influenced by the interaction of the hydrophobic
fractions. The mean diameter
of QT-P/T (18.43 nm) was smaller than that of QT-P123 (29.04
nm). This might be
attributed to the influence of copolymer composition, in
copolymer carrier kept
constant at 10 mM, part of P123 molecules was replaced by TPGS
with a smaller
molecular weight and a smaller hydrophobic group than P123, so
QT-P/T showed a
significantly smaller hydrophobic volume than that of QT-P123,
which might result in
The average size and size distribution for empty micelles and
drug
loaded micelles were presented in Fig.2. The average size of
empty P123 micelles and
mixed micelles composed of P123/TPGS was under 10 nm with rather
narrow size
distribution patterns. An increasing in the average size after
QT loading was observed
from 8.85 nm (Fig.2(C)) to 29.04 nm (Fig.2(A)) for P123 micelles
and from 9.45 nm
(Fig.2(D)) to 18.43 nm (Fig.2(B)) for mixed micelles composed of
P123/TPGS with
the molar ratio at 7:3, respectively.
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smaller size.
Stable and small particle sizes (
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block length, the nature and block length of the outer shell for
micelle.46
The solubility of QT in the obtained QT-P/T micelle solution was
5.56 0.34
mg/mL, while only 2.03 0.44 g/mL for that of QT in water. That
is to say, the
solubility of QT in the polymeric micelles was about 2738-fold
that of crude QT in
water.
Based on
these reasons, copolymer carriers composed of P123 and TPGS with
different
proportions were studied. As shown in Table 1, the DL% of the
QT-P/T with the molar
ratio of P123 to TPGS at 7:3 (10.59 0.38%) was higher than that
of QT-P123 (8.25
0.32%). This result might be related to the stable reaction
among the aromatic ring
in TPGS, PO groups in P123 and incorporated drug. However, when
the proportion
was at 5:5, the EE% (37.95 3.27%) and DL% (5.84 0.50%) were
markedly
decreased. The possible reason was that QT-P/T with the molar
ratio of P123 to TPGS
at 5:5 showed a significantly smaller hydrophobic volume than
that of QT-P123 or
QT-P/T with the molar ratio of P123 to TPGS at 7:3.
Critical Micelle Concentration (CMC)
Pluronic copolymers consist of ethylene oxide (EO) and propylene
oxide (PO) blocks,
and can undergo self-assembly into spherical micelles in aqueous
solution.40
The CMC value for micellar solution made from P/T with the molar
ratio of P123
to TPGS at 7:3 or P123 was as low as 1.9310
CMC
was a parameter indicative of the micelles stability in vitro
and in vivo. In this study,
it was measured by fluorescence technique with the pyrene as a
hydrophobic probe.
The CMC value was obtained by plotting the ratio of I372/I383 of
the emission
spectra profile vs the concentration of copolymers as shown in
Fig.6. This ratio of
I372/I383 was decreased with increasing the concentration of
copolymer.
-5 M (Fig.6 (A)) or 1.9710-5 M (Fig.6
(B)), respectively, which was in accordance with previous
report.47
The addition of
TPGS did not result in notable variation in the CMC. Because of
the low CMC, the
micelles had high stability and ability to maintain integrity
even upon extreme
dilution in body.
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In vitro Release of QT from Micelles
The in vitro release of QT from micellar formulation under sink
condition was
investigated by dialysis method with 0.5% Tween 80 solution as
release medium. As
shown in Fig.7, only 15% of QT was released from QT-P/T and
QT-P123 within the
first 4 h, while almost all QT was released from the propylene
glycol solution during
the same time period. After 60 h, 20-30% of the initially
incorporated drug still
existed in the micelles. The result indicated that the micelles
showed a
sustained-release property for the incorporated QT, which was
similar to the reported
studies.33,48,49 The released mechanism of QT from micelles
might be related to the
drug diffusion and the polymer material erosions or swelling.50
It was noticed that the
release of QT from mixed micelles was faster than that of P123
micelles. It could be
explained that the addition of TPGS enlarged the ratio of
hydrophilic part in the
mixed micelles and facilitated water molecules into the core of
the micelles, leading
to more hydrophilic channels.
35
Cytotoxicity in vitro
The in vitro cytotoxicity of QT-P/T and QT-P123 was assessed on
MCF-7 and
MCF-7/ADR cells with QT DMSO solution as control. The empty
micelles of P/T
and P123 with the same copolymer concentrations as QT-P/T and
QT-P123 were used
as control, too. The cells were incubated for 48 h in the
presence of the micelles or
free QT, and then their survival was analyzed using the MTT
assay. The viability of
MCF-7 and MCF-7/ADR cells after incubation with various
formulations of QT and
empty micelles was presented in Fig.8. The IC50
It was reported that P123 did not display obvious cytotoxicity
to HDF broblast
cells.
values on MCF-7 cells for free QT in
DMSO solution, QT-P/T, and QT-P123 were 16.32 g/mL, 7.13 g/mL
and 10.73
g/mL, respectively, while 16.87 g/mL, 7.23 g/mL and 14.47 g/mL
on
MCF-7/ADR cells (Fig.8 (A,C)). The results demonstrated that
QT-P/T showed a
higher cytotoxicity compared to the free drug and QT-P123 on
both MCF-7 and
MCF-7/ADR cells.
51 However, in this study, it was obvious that the empty
micelles of P/T and P123
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displayed cytotoxicity on MCF-7 and MCF-7/ADR cell lines, and
the cytotoxicity of
P/T empty micelles was higher than that of P123 empty micelles
(Fig.8 (B,D)). This
could be explained with addition of the TPGS. TPGS in the mixed
micelles might act
as P-glycoprotein inhibitor to reduce drug efflux. Moreover,
animal studies of human
cancer xenografts found that TPGS could effectively suppress
tumor growth. The
anticancer activity of TPGS was reported to be related to its
unique apoptosis-
inducing properties via the generation of reactive oxygen
species (ROS). ROS could
damage DNA, proteins, and fatty acids in cells, resulting in
apoptotic cell death.30
Therefore, QT-P/T showed higher cytotoxicity and might be
considered as an
effective anticancer drug delivery system for cancer
chemotherapy compared with
QT-P123.
CONCLUSIONS
The mixed polymeric micelles, composed of P123 and TPGS with the
proportion of
7:3, exhibited higher encapsulating efficiency and drug-loading
for QT. The average
size of QT loaded mixed micelles was 18.43 nm, and zeta
potential was -10.18 mV.
The solubility of QT in QT-P/T was 5.56 mg/mL, which was about
2738-fold that of
crude QT in water. Compared with the free drug, QT-P/T showed a
significantly
enhanced cytotoxicity. Based on these results, it can be
concluded that the polymeric
micelles formulation developed in this study may be considered
as a promising
delivery system for QT.
Acknowledgements: This work is partly supported by a research
grant
(No.2008GG10002012) from Department of Shandong Science and
technology, P. R.
China.
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19
Table 1 EE% and DL% of QT in micelles at 10 mM copolymers (n =
5)
Composition (molar ratio) EE% DL%
P123 (10) 87.06 3.80 8.25 0.32
P123:TPGS (5:5) 37.95 3.27 5.84 0.50
P123:TPGS (7:3) 88.94 3.71 10.59 0.38
Liyan Zhao, et al., Table 1
-
20
Captions
Fig.1 The structure of QT.
Fig.2 DLS particle size distribution of QT-P123 (A), QT-P/T (B),
empty P123
micelles (C), and empty P/T mixed micelles (D).
Fig.3 TEM image of QT loaded P123/TPGS mixed micelles
(19,0000).
Fig.4 Schematic illustration of QT loaded micelle composed of
P123 and TPGS.
Fig.5 Photographic images of QT-P/T (A), QT-P123 (B) and QT
suspension (C).
Fig.6 Plot of I372/I383 vs concentrations of copolymers in
deionized water.
Copolymers of P123/TPGS (7:3) (A); P123 (B)
Fig.7 Release proles of QT from QT-P123 (), QT-P/T () and the
propylene glycol
solution () in 0.5% Tween 80 solution at 37 C. Each point
represents average
SD (n = 3).
Fig.8 Viability of MCF-7 cells after incubation with various
formulations of QT (A),
and empty micelles (B); Viability of MCF-7/ADR cells after
incubation with
various formulations of QT (C), empty micelles (D). Each point
represents
average SD (n = 3).
-
21
Fig.1 The structure of QT.
Liyan Zhao, et al., Fig. 1
-
22
20 25 30 35 40 450.0
0.1
0.2
0.3
0.4
0.5
A
in cl
ass
Diameter (nm)10 15 20 25 30 35
0.00
0.05
0.10
0.15
0.20
0.25 B
in cl
ass
Diameter (nm)
10 15 20 25 30 350.00
0.05
0.10
0.15
0.20
0.25 B
in cl
ass
Diameter (nm)
4 6 8 10 12 14 16 18 200.00
0.05
0.10
0.15
0.20
0.25 D
in cl
ass
Dimameter (nm)
Fig.2 DLS particle size distribution of QT-P123 (A), QT-P/T (B),
empty P123
micelles (C), and empty P/T mixed micelles (D).
Liyan Zhao, et al., Fig. 2
-
23
Fig.3 TEM image of QT loaded P123/TPGS mixed micelles
(19,0000).
Liyan Zhao, et al., Fig. 3
-
24
Fig.4 Schematic illustration of QT loaded micelle composed of
P123 and TPGS.
Liyan Zhao, et al., Fig. 4
-
25
Fig.5 Photographic images of QT-P/T (A), QT-P123 (B) and QT
suspension (C).
Liyan Zhao, et al., Fig. 5
-
26
11.11.21.31.41.51.61.71.8
0 20 40 60 80 100 120 140 160
mM/mL
I372
/I383
A
11.11.21.31.41.51.61.71.8
0 20 40 60 80 100 120 140 160
mM/mL
I372
/I383
11.11.21.31.41.51.61.71.8
0 20 40 60 80 100 120 140 160
mM/mL
I372
/I383
A
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
0 20 40 60 80 100 120 140 160
mM/mL
I372/I383
B
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
0 20 40 60 80 100 120 140 160
mM/mL
I372/I383
B
Fig.6 Plot of I372/I383 vs concentrations of copolymers in
deionized water.
Copolymers of P123/TPGS (7:3) (A); P123 (B)
Liyan Zhao, et al., Fig. 6
-
27
0
20
40
60
80
100
120
0 10 20 30 40 50 60
Time (h)
Cum
ulat
ive
rele
ase
(% free QTQT-P/TQT-P123
Fig.7 Release proles of QT from QT-P123(), QT-P/T() and the
propylene glycol
solution () in 0.5% Tween 80 solution at 37 C. Each point
represents average
SD (n = 3).
Liyan Zhao, et al., Fig. 7
-
28
Fig.8 Viability of MCF-7 cells after incubation with various
formulations of QT (A), and empty micelles (B); Viability of
MCF-7/ADR cells after incubation with various
formulations of QT (C), empty micelles (D). Each point
represents average SD (n =
3).
Liyan Zhao, et al., Fig. 8
A
0
20
40
60
80
100
120
0 20 40 60 80
Concentration (g/ml)
Cel
l via
bilit
y QT-P/TQT-P123 free QT
B
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80
Concentration (g/ml)
Cel
l via
bilit
y
empty P/T empty P123
C
0
20
40
60
80
100
120
0 20 40 60 80
Concentration (g/mL)
Cel
l via
bilit
y
QT-P/T QT-P123free QT
D
0
20
40
60
80
100
120
0 20 40 60 80
Concentration (g/ml)
Cel
l via
bilit
y
empty QT-P/T
empty QT-P123
Materials and MethodsMaterialsPreparation of QT Loaded
MicellesCharacterization of MicellesParticle Size
DistributionDrug-loading and Entrapment EfficiencyCritical Micelle
Concentration (CMC)In vitro Release of QT from MicellesCytotoxicity
in vitroParticle Size DistributionSurface Morphology and
Zeta-potentialBoth QT-P123 and QT-P/T were negatively charged with
zeta-potential of about -4.08 mV and -10.18 mV, respectively. While
the empty P123 micelles were almost neutral (0.78 mV) and the
zeta-potential of the empty P/T micelles was -7.48 mV. The
structu...Critical Micelle Concentration (CMC)In vitro Release of
QT from MicellesCytotoxicity in vitroConclusionsReferences