SIGCHI Conference Paper Format

Formulation and Characterization of Limonene Based
Microemulsions as Transdermal Delivery Carrier
Napaphak Jaipakdee, Faculty of Pharmaceutical Sciences, Khon Kaen University, Thailand,
[email protected]; Ekapol Limpongsa, Faculty of Pharmaceutical Sciences, Khon Kaen University,
Thailand, [email protected]; Thaned Pongjunyakul, Faculty of Pharmaceutical Sciences, Khon Kaen
University, Thailand, [email protected]
INTRODUCTION
surfactant or surfactant systems (T20-LAS at weight ratio
of 1:3, 1:1, 3:1) were prepared at weight ratios of 9:1 to 1:9
into different vials. These mixtures were titrated drop-wise
with deionized water. The point at which the mixture
became turbid or showed signs of phase separation was
considered as the end point of the titration.
Limonene (LMN), obtained from the lemon peel of Citrus
lemon, is a hydrocarbon lipophilic terpene. Terpenes are a
class of permeation enhancer classified as generally
regarded as safe due to their reversible effect on stratum
corneum and minimal irritancy (1, 7). LMN has been
reported as an effective permeation enhancer for several
molecules including indomethacin, ketoprofen, nicardipine
hydrochloride, sumatriptan succinate (4) and aclofenac (5).
Terpene microemulsions for transdermal delivery were
recently developed and reported as a promising tool for
curcumin delivery (6). Microemulsions (ME) are
thermodynamically stable, isotropic transparent dispersions
of oil, water and surfactant systems. MEs are currently of
interest as the drug delivery carriers due to several
advantages including drug solubilization improvement,
drug penetration enhancement, long term stability and ease
of preparation (3). The aim of this study was to formulate
and characterized LMN based ME. Minoxidil (Mx) was
used as a model drug for being low water solubility
property and due to its therapeutic application in the
treatment of alopecia.
Preparation of LMN based MEs
ME systems were obtained by mixing LMN, surfactant
system together, and adding precisely the mixture of watercosolvents to these oily phases with continuously stirring.
Characterization of LMN based MEs
The pH of MEs was determined using a pH meter (Corning
M250, Ciba Corning, UK). The viscosity was measured
using a viscometer (Model DV-III; Brookfield Engineering
Laboratories, MA). The average droplet size was
characterized using a Zetasizer Nano (Malvern, UK) at a
temperature of 25±1 C. The solubility of Mx in the
selected MEs was also determined.
RESULTS AND DISCUSSION
Surfactants
MATERIALS AND METHODS
T 20
T 80
LAS
HCO 40
Materials: d-Limonene (LMN) was purchased from
Fluka®Analytical (USA). Tween 20 (ECOTERIC 20; T20)
and Tween 80 (ECOTERIC 80; T80) were purchased from
Ajax Finechem (Australia). PEG-8 caprylic capric glyceride
(Labrasol; LAS) was kindly provided by Gattefossé,
France. PEG-40 hydrogenated castor oil (Nikkol HCO-40;
HCO 40) was provided by Nikko Chemicals (Japan).
Minoxidil was obtained S. Tong Chemicals (Thailand).
Smin (%, w/w)
Mx solubility (mg/ml)
54.7  1.0
59.3  0.8
45.3  0.5
52.9  1.7
7.9  0.1
4.0  0.3
12.6  0.2
2.9  0.4
Table 1. Surfactant efficiency (Smin) and drug solubility
(mean  SD, n=3)
[A]
LAS-T20
[B]
3:1 LAS-T20
1:1 LAS-T20
ME
1:3 LAS-T20
1:3
LAS to T20 Ratio
Screening study
The test surfactant was added drop by drop to the 1:1
weight ratio of LMN to water mixtures. Amount of
surfactant required to change the LMN-water mixture
appearance from turbid to transparent corresponded to the
Smin (2). The Mx solubility in different surfactants was also
carried out by shaking the excess amount of Mx in each
component at 32 ± 1 °C for 24 h. After filtration, the filtrate
was analyzed for Mx by HPLC assay.
1:1
3:1
0
20
40
60
Existence area of Microemulsion (%)
LMN
Water
Figure 1. Pseudo-ternary phase diagram [A] and
existence area of ME (%) [B] of systems composed of
LMN, water and mixtures of LAS and T20 at the ratio
of 3:1, 1:1 and 1:3, respectively.
Construction of pseudo-ternary phase diagram
The phase diagrams were constructed using water titration
method at ambient condition. Briefly, mixtures of oil with
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Compositions (% w/w)
Physicochemical characteristics
RX
LMN
Surfactants
[LAS : T20]
Surfactant
amount
Co-solvent
L1
4
3:1
30.0
L2
12
3:1
L3
8
L4
4
a
DI
water
pH
Viscosity
(cP)
Average droplet
b
size (nm)
Mx Solubility
(mg/ml)
33.0
33.0
5.7 ± 0.1
15.8 ± 0.2
15.2 ± 3.1
32.9 ± 1.3
50.0
19.0
19.0
5.8 ± 0.1
26.8 ± 0.2
12.5 ± 0.5
26.2 ± 0.2
1:1
40.0
26.0
26.0
5.7 ± 0.1
18.3 ± 0.2
15.5 ± 2.8
30.1 ± 0.9
1:3
50.0
23.0
23.0
5.8 ± 0.1
51.0 ± 0.4
8.6 ± 0.1
29.5 ± 0.2
a
Co-solvent was a mixture of ethanol and propylene glycol at a volume ratio of 1:3;
b
Polydispersity index ranged between 0.09–0.14.
Table 2: Compositions of LMN based MEs (% w/w) and the corresponding physicochemical characteristics.
Deionized water
CONCLUSION
Isopropyl alcohol
In this study, the novel LMN based ME systems for
transdermal delivery were constructed using T20 and LAS
as surfactant systems. The efficacy of the developed LMN
based MEs as a permeation enhancer system shall be
further investigated.
Butanol
Ethanol
Propylene glycol
0
50
100
150
Mx solubility (mg/ml)
ACKNOWLEDGEMENTS
Figure 2. Solubility of Mx in various solvents at 32C
(mean  SD, n=3)
This work was supported by the Thailand Research Fund
(MRG5480035), the Commission on Higher Education and
Khon Kaen University, Ministry of Education, Thailand.
In order to find a suitable surfactant for LMN, the S min and
Mx solubility were determined (Table 1). LAS and T20
were selected as the surfactant system of LMN MEs. Phase
diagrams were constructed in order to find out the
concentration range of components for the existing range of
MEs (Figure 1). The area of region changed slightly in size
with increasing the ratio of T20. According to ME areas in
the phase diagrams, LMN based ME at different component
ratios were formulated (Table 2). In the case of MEs which
will be used as drug delivery systems, drug loading is a
critical factor for formulation designation. Considering the
solubility of Mx in LMN (<0.1 mg/ml), LAS, T20 and
water (3.0  0.1 mg/ml), it was found necessary to add a cosolvent to increase solubility of the loading drug in the ME
systems. Among the solvent tested, propylene glycol and
ethanol showed the highest Mx solubilizing effects (Figure
2) and therefore were used as co-solvents.
REFERENCES
1. Aqil, M.; Ahad, A.; Sultana, Y. and Ali, A. Status of
terpenes as skin penetration enhancers. Drug Discov.
Today. 12 (23/24), 1061-1067 (2007).
2. Djekic, L. and Primorac, M. The influence of
cosurfactants and oils on the formation of
pharmaceutical microemulsions based on PEG-8
caprylic/capric glycerides. Int. J. Pharm. 352, 231–239
(2008).
3. Fanun, M. Microemulsions as delivery systems. Curr.
Opin. Colloid Interface Sci. 17, 306–313 (2012).
4. Femenía-Font, A.; Balaguer-Fernández, C.; Merino, V.;
Rodilla, V. and López-Castellano, A. Effect of chemical
enhancers on the in vitro percutaneous absorption of
sumatriptan succinate. Eur. J. Pharm. Biopharm. 61, 50–
55 (2005).
5. Lee, J.; Lee, Y.; Kim, J.; Yoon, M. and Choi, Y.W.
Formulation of microemulsion systems for transdermal
delivery of aceclofenac. Arch. Pharm. Res. 28(9), 10971102 (2005).
6. Liu, C-H.; Chang, F-Y. and Hung, D-K. Terpene
microemulsions for transdermal curcumin delivery:
Effects of terpenes and cosurfactants. Colloids Surf., B.
82, 63–70 (2011).
7. Sapra, B.; Jain, S. and Tiwary, A.K. Percutaneous
permeation enhancement by terpenes: mechanistic view.
AAPS J. 10(1), 120-132 (2008).
The developed LMN ME vehicles (L1 - L4) were isotropic,
transparent oil-in-water dispersions with the pH range
between 5.7-5.8 and the mean droplet size range from 8.6 ±
to 15.5 nm (Table 2). The highest viscosity value of L4
(51.03 cP) which contained 1:3 of LAS to T20 relative to
those L1 - L3 (15.8 - 26.8 cP) might be because of the
higher viscosity of T20 as compared to that of LAS. The
solubility of MX in MEs ranged from 26.2 – 32.9 mg/ml of
which increased with the content of co-solvent in the
formulations. Additionally, visual examination showed that
all LMN ME developed were stable after being subjected to
freeze–thaw cycles, indicating that the systems were
thermodynamically stable for long periods.
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