الفهرس 
general introduction
pre - formulation screeingOnly 14 pages are availabe for public view
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Abstract
Summary
Lipid Drug Delivery Systems for Brain Targeting
Brain drug delivery is a major challenge, despite the increased blood flow due to
the poor access of neurotherapeutics to the central nervous system. This is attributed to
the presence of the brain blood barrier (BBB) which is considered a physical anatomical
barrier, a transport barrier, an enzymatic barrier and an immunological barrier.
The intranasal route is considered one of the most important non-invasive
strategies of enhancing the brain drug delivery. This is due to its large surface area and
highly vascularised nasal epithelium which ensures high degree of absorption and
transport into the systemic circulation. Moreover, the olfactory pathway allows direct
delivery to the brain bypassing the blood brain barrier. However, poor contacts of the
formulations with the nasal mucosa as well as low absorption of polar drugs are some of
the major limitations which should be overcome when considering this route
SLNs offer a drug delivery system capable of enhancing brain drug delivery due
to its lipophilic nature allowing drug permeation across the nasal epithelium, moreover,
its nanosized particulate nature facilitates its nasal and brain cellular uptake. The
transport of SLNs to the brain depends on the characteristics of the SLNs themselves
rather than the entrapped drug. Two of the most important characteristics are the particle
size and the surface charge. Small particle size (< 200 nm) is required for enhanced
uptake to the brain, while the surface charge in enhancing the transport of nanoparticles
across the BBB is controversial.
Galantamine hydrobromide (GalHBr) is an acetylcholine esterase inhibitor used
for the treatment of mild to moderate Alzehimer’s disease. It is a hydrophilic drug which
limits its uptake to the brain cells. It suffers frequent dosing due to its short half life time
(7 h). Moreover, its oral administration leads to several side effects like nausea, vomiting,
diarrhea, weight loss and loss of appetite.
Summary
180
The aim of this study was to develop an intranasal drug delivery system capable
of enhancing brain delivery of GalHBr to give higher bioavailability and reduce its side
effects. This was planned to be achieved through a comparative study between anionic,
cationic and chitosan SLNs; to study the influence of surface charge on the drug brain
uptake and to decrease dosing frequency by increasing residence time in the nasal cavity.
The work in this thesis was divided to three chapters:
4. Chapter one: Preliminary study for optimization of various formulation
parameters for the preparation of anionic plain SLNs
5. Chapter two: Preparation and evaluation of galantamine hydrobromide loaded
anionic, cationic and chitosan SLNs
6. Chapter three: Biological studies on galantamine hydrobromide loaded anionic,
cationic and chitosan SLNs formulations
Chapter I: Preliminary study for optimization of various formulation parameters for
the preparation of anionic plain SLNs
In this chapter, Plain anionic SLNs were prepared utilizing the hot high shear
homogenization followed by sonication method. At first a preliminary study was carried
out using different formulation parameters including different lipids with different
concentrations (1, 3, 5, 7.5 and 10 wt%) in the presence of either tween80 or Brij®78
(3wt%). Then the effect of various surfactants concentrations (3, 5, 7 and 10 wt%) were
studied on the optimum selected lipid types (Precirol5®ATO, Compritol888®ATO and
GMS) and concentration (7.5wt%). Poloxamer188 was added to all the prepared
formulations at constant concentration 3 wt%. The parameters measured were the particle
size (PS), polydispersity index (PDI) and zeta potential (ʓ) of anionic SLNs.
Concerning the results obtained, it was noticed that increasing both surfactants
concentrations (Brij®78 and Tween80) increased the particle size significantly. However,
the reverse occurred with GMS/Brij®78 systems. The ʓ values were recognized to be
lowered with increasing surfactants concentrations except with GMS/Tween80 SLNs
were an increase in ʓ values were observed.
Summary
181
Chapter II: Preparation and evaluation of Galantamine hydrobromide loaded anionic,
cationic and chitosan SLNs
In this chapter, the drug (GalHBr) was loaded in the plain SLNs prepared in the
previous chapter. Sodium deoxycholate (SDC) was added at a molar ratio 1:1 to the drug.
Hot high shear homogenization was done at speed 24000 rpm for 5 min followed without
further ultrasonication.
Afterwards, a full factorial design was constructed for further optimization of the
preparation of GalHBr loaded anionic SLNs. The three independent variables were the
surfactant concentration (3%, 5%, 7 and 10%), the surfactant type (Brij78 and Tween80)
and the lipid type (Precirol5®ATO, Compritol888®ATO and GMS). The dependent
variables investigated PS and zeta potential, however, the experimental model was
insignificant for entrapment efficiency (EE%).
Based on the results of the factorial design experiments for optimization of
GalHBr loaded anionic SLNs, we can conclude that increasing surfactants concentration
significantly decreased the mean PS and the ʓ.
Concerning the GalHBr loaded cationic SLNs a preliminary study was carried for
optimization of the formulation parameters including stearyl amine (SA) concentration as
a positive charge inducer (0.14%,0.3%, 0.56% and 1% ) and the SDC concentration (low
and high molar ratios to the drug). The results showed that SA could be added as a
positive charge inducer at a concentration 0.56% and 1:1 molar ratio of SDC:GalHBr.
GalHBr loaded cationic SLNs had smaller PS relative to their anionic counterparts with a
reversed ʓ and decreased EE%. An in vitro release study was carried out and showed that
cationic SLNs had more sustained release of GalHBr than anionic SLNs.
Furthermore, a modification was done by addition of low molecular weight
chitosan to nasal mucoadhesion. First, a preliminary study was carried for optimization of
the formulation parameters including chitosan (CS) concentration. The results revealed
that 0.15%w/v produced SLNs with PS and ʓ values greater than their cationic
counterparts. However, their EE% were diminished.
Summary
182
The in vitro release study outlined that CS SLNs had a more sustained release of
GalHBr than cationic and anionic SLNs, respectively.
In addition, GalHBr loaded anionic, cationic and chitosan SLNs were visualized
using transmission electron microscope (TEM), where the TEM micrographs confirmed
the spherical or quasi spherical shape of SLNs with smooth surface and no obvious
particle aggregation except chitosan SLNs which exhibited reversible particle
agglomeration.
Further characterization of SLNs by performing DSC confirmed the reduction in
the crystallinity of the solidified lipid mixtures creating more space for drug
accommodation and enhancing the EE% of GalHBr. In addition, the disappearance of the
drug peak indicated its amorphous nature or molecular dispersion within the SLNs.
Chapter III: Biological studies on Galantamine hydrobromide loaded anionic, cationic
and chitosan SLNs formulations
In this chapter, biological investigations including pharmacokinetic studies in plasma
and brain, drug targeting efficiency, nose to brain direct transport and histopathological
examinations were performed on male Wister albino rats, which were divided into five
groups as follow:
i. group 1 received IV GalHBr solution
ii. group 2 received IN GalHBr solution.
iii. group 3 received IN GalHBr loaded anionic SLNs (7.5%GMS+10%Brij®78+3%
poloxamer188+1:1molar ratio of Drug:SDC)
iv. group 4 received IN GalHBr loaded cationic SLNs (7.5%GMS+10%Brij®78+3%
poloxamer188+1:1molar ratio of Drug:SDC+ 0.56%SA)
v. group 5 received IN GalHBr loaded chitosan SLNs
((7.5%GMS+10%Brij®78+3% poloxamer188+1:1molar ratio of Drug:SDC+
0.56%SA+0.15%w/v chitosan).
Summary
183
GalHBr was administered in a dose of 0.22 mg/kg (20 μL) in each nostril. GalHBr
concentrations in blood and brain tissue samples were collected for the following 6 hours
at different time intervals, viz., 4, 6, 10, 15, 30, 45, 60, 120, 180 and 360 min and then
assayed using LC/ MS-MS mass spectrometer. The histopathological study was done by
daily administration of the GalHBr dose for 14 days.
The pharmacokinetic parameters in rat plasma showed that GalHBr concentration
only lasted for 3 hours after IN administration of GalHBr solution compared to 6 hours
after IN administration of the three SLNs formulations. On the other hand, GalHBr
reached its maximum concentration in rat plasma 10, 7 and 11 min following IN
administration of anionic, cationic and chitosan SLNs, respectively. However, it reached
its maximum concentration in rat plasma 4 min following IV administration of GalHBr
solution. Chitosan and anionic SLNs showed higer Cmax and AUC0-360min in rat plasma
than cationic SLNs. They also showed higher absolute bioavailability values (94.5,
56.6%) than cationic SLNs (22.25%). This was due to their longer blood circulation with
t1/2> two hours and MRT approximately 3 hours.
The pharmacokinetic parameters in rat brain showed that intranasal administration of
GalHBr solution achieved maximum drug concentration after 11 min and only lasted for
one hour compared to 6 hours for other formulations. It showed the lowest Cmax,
AUC0-360min, and MRT in rat brain. Anionic SLNs showed the highest t½ and MRT as it
lasted for 2.9 h in brain, while both cationic and chitosan SLNs showed a MRT of 2.7 h.
The transport study showed that anionic SLNs possessed the highest drug targeting
efficiency to the brain (DTE %) followed by the cationic SLNs and then chitosan SLNs.
In addition, the main GalHBr transport pathway to rat brain for the anionic and the
cationic SLNs was the olfactory route, while for the chitosan SLNs the drug transport
took place via the systemic route. Moreover, the brain/blood ratio of anionic, cationic and
chitosan SLNs were 24.2, 22.8 and 3.8 fold higher when compared to IN GalHBr solution
Summary