Lipid nanoparticles in anti-breast cancer drug delivery systems and drug-membrane interactions
Current anticancer drugs are plagued with lack of sustained effect and poor delivery. Many current studies focus on the use of drug carriers, particularly lipid nanoparticles as new drug delivery systems. In this study, a nanostructured lipid carrier (NLC) was formulated to serve as a carrier...
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| Format: | Thesis |
| Language: | English |
| Published: |
2014
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| Online Access: | http://psasir.upm.edu.my/id/eprint/70806/1/FPV%202014%2012%20-%20IR.pdf http://psasir.upm.edu.my/id/eprint/70806/ |
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| Summary: | Current anticancer drugs are plagued with lack of sustained effect and poor
delivery. Many current studies focus on the use of drug carriers, particularly
lipid nanoparticles as new drug delivery systems. In this study, a
nanostructured lipid carrier (NLC) was formulated to serve as a carrier for
tamoxifen (TAM). The study is also undertaken to determine the drugmembrane
interaction through the use of liposomes as a membrane model.
Hence, the main objectives of this study are to develop and determine the
physicochemical and biological properties of NLC loaded with TAM (TAMNLC),
and to determine the interaction between the trimethoxybenzoyl
analogue of catechin gallate (TMCG) and lipid membrane.
The NLC and TAM-NLC were prepared by high pressure homogenisation
method. The lipid phase consisted of hydrogenated palm oil, olive oil and
phosphatidylcholine as the lipid phase, while the aqueous phases are
polysorbate 80, sorbitol, thimerosal and double-distilled water. The major
components in the formulation were carefully chosen based on the absence
of cytotoxicity towards a normal cell line (murine fibroblasts, BALB/c 3T3).
The physicochemical characteristics of NLC, i.e. particle size, zeta potential
(ZP), thermal profile, crystallinity, morphology and stability were assessed by
photon correlation spectroscopy (PCS), laser doppler velocimetry, differential
scanning calorimetry (DSC), wide-angle X-ray diffractometry (WAXD),
transmission electron microscopy (TEM) and spectrophotometry, respectively.
The release kinetics of TAM-NLC was determined by the Franz diffusion cell
system while its cytotoxicity was determined in vitro on the human breast
(MCF-7) and mouse mammary (4T1) cancer cell lines. To determine the
drug-membrane interaction, a dried lipid film of 1,2-dipalmitoyl-sn-glycero-3-
phosphocholine (DPPC) was used to form liposomes and to entrap TMCG
and quinone methide (QM, metabolite of TMCG) separately. The interaction
of drug with the model membrane was assessed by DSC, WAXD, smallangle
X-ray diffractometry (SAXD) and Fourier-transform infrared (FTIR). The
PyMOL software was used to construct the molecular model of drug and
membrane interaction.The study showed that hydrogenated palm oil, trilaurin and docosanoic acid
were significantly less cytotoxic than palmitin. Since surfactants influenced
the physicochemical properties of the NLC, polysorbate 20 and 80 were
assessed for use in the NLC formulation. The NLC formulated with
polysorbate 80 showed good compatibility with the lipid phase, while
polysorbate 20 caused destabilisation of the nanoparticles that resulted in
phase separation during storage. With polysorbate 80 as surfactant, the
NLCs are relatively spherical, with an average size of 102.8 nm, zeta
potential of -30.57 mV, and possessed superior particle surface area to
volume ratios. The transition temperature of NLC formulated with polysorbate
80 was 55.85 °C, which was lower than that formulated with polysorbate 20
or unprocessed lipid. The results indicated that NLC formulated with
polysorbate 80 is of lower crystallinity and this was confirmed by WAXD. The
NLC was also shown to be of low cytotoxicity to BALB/c 3T3 cell line. The
NLC incubated with foetal bovine serum-supplemented media did not show
increase in particle size, suggesting that its stability is good and practicality
for use in intravenous administration. The stability of TAM-NLC was
determined by storage at physiological pHs. The formulation is more stable at
pH 7.4 (blood pH) even though its ZP was lower compared to pH 2.3
(stomach pH). The release of TAM from TAM-NLC followed first-order
kinetics, while showing high cytotoxicity to MCF-7 and 4T1 cell lines with halfminimal
inhibitory concentration of 5.56 and 5.19 μg mL-1, respectively.
To determine the drug-membrane interaction, TMCG was used as the
prodrug model and liposomes as the cell membrane model. The DSC
analysis showed that TMCG was incorporated into DPPC membranes and
had intercalated in-between the phospholipids molecules while reducing the
cooperativity and lowering the transition temperature of the gel to liquidcrystalline
phase. In addition, TMCG did not affect the macroscopic bilayer
organisation of the liposomes; instead it decreased the thickness of the
bilayer by forming an interdigitated gel phase. Quinone methide, the active
form of TMCG however, showed limited interaction with the phospholipid
bilayer indicating that a superficial interaction had occurred between QM and
the phospholipid membrane with a weak gel stabilising effect and decreased
hydrogen-bonding pattern of the interfacial region of the phospholipid. These
results concur with the molecular dynamics simulation studies, which showed
that TMCG was incorporated into the membrane phospholipid palisade while
QM was excluded and interacted weakly with the polar portion of the lipid
bilayer.
In conclusion, the study showed that the optimised NLC formulation with low
cytotoxicity is a superior vehicle for encapsulation and carriage of TAM. The
TAM-NLC developed in this study showed controlled-released characteristics,
good stability at physiological pH with potential for tumour targeting. The
study also reinforced the reliability of liposomes as cell membrane models,
and TMCG interacts very well with it. |
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