Development and evaluation of Ibuprofen-calcium alginate beads
SanchitaMandal a*, Sanat Kumar Basub,
a
Divisionof Pharmaceutics, H.K. College of Pharmacy, Jogeshwari (w)
Mumbai 400102
b
Ex-Professor, Division of Pharmaceutics, Department of Pharmaceutical
Technology, Jadavpur University, Kolkata 700032, INDIA
*Corresponding author: E-mail: sm_pharm@yahoo.co.in
ABSTRACT
THE objective of this study was to develop a sustained release dosage
form of Ibuprofen (IBP) using a natural polymeric carrier prepared in a
completely aqueous environment. IBP was entrapped in calcium alginate
bead prepared with sodium alginate by ionotropic gelation method using
calcium chloride as a crosslinking agent. The drug was incorporated
either into preformed calcium alginate gel beads (sequential method) or
incorporated simultaneously during the gelation stage (simultaneous
method). The beads were evaluated for particle size and surface
morphology using optical microscopy and SEM respectively. Beads
produced by the sequential method had higher drug entrapment. Drug
entrapment in the sequential method increases with increase in CaCl 2 and polymer concentration but decreased with increase in
drug concentration. And in the simultaneous method drug entrapment
increases when polymer and drug concentration were increased and it
increased to a certain extent with increase in CaCl2
concentration and further increase resulted in lower drug loading. FTIR
studies revealed that there is no interaction between drug and CaCl 2. XRD studies show that crystalline drug changed to
amorphous state after formulation. Release characteristics of the IBP
loaded calcium alginate beads were studied in enzyme free simulated
gastric and intestinal fluid.
Key words:
SodiumAlginate, Calcium alginate bead, Ibuprofen, ionotropic gelation.
INTRODUCTION
Among the most abundant natural polymers, polysaccharides are widely used
in pharmaceutical dosage forms as excipients like suspending agents,
emulsifying agents, tablet binders, gelling agents. With the advent of
macromolecular chemistry, the use of polysaccharides has been extended
towards new applications in pharmaceutical, biomedical, and agricultural
fields.
Sodium alginate, a hydrophilic biopolymer obtained from brown seaweeds has
been found to be highly promising with respect to drug delivery because of
its high biological safety [1]. Chemically, it is a polysaccharide composed
of varying proportion of D-mannuronic acid (M) and L-guluronic acid (G)
residues which are arranged in MM or GG blocks interspersed with MG
blocks[2]. In addition to its use as a thickening, gel forming and
colloidal stabilizing agent in food and beverage industries, it as also
used as binder in tablet formulation [3]. Its unique property of forming
water insoluble calcium alginate gel through ionotropic gelation with Ca +2 ions in simple and mild conditions has made possible to
encapsulate both macromolecular agents [4-6] and low molecular weight
therapeutic agents[7-9]. The current uses of alginate based devices are
mainly related to encapsulation of various classes of therapeutic agents.
In this study, IBP was incorporated into calcium alginate beads by
sequential and simultaneous methods. The effect of polymer and CaCl 2 concentration and that of IBP concentration on drug entrapment
(drug loading) and drug release characteristics were studied. The
drug-loaded beads were also characterized using different techniques.
MATERIALS AND METHODS
Ibuprofen (Indian Pharmacopoeia) (M/S Albert David Pvt. Limited, Kolkata,
India.), Sodium alginate (Fluka) 90 cps (1% w/v solution in water at 25°C),
Calcium chloride dihydrate (E. Merck, India). All other reagents were of
analytical grade.
Preparation of beads
For bead formation, 50ml of a 2-2.5% w/v aqueous solution of sodium
alginate was introduced dropwise from a glass syringe with a size-22 needle
into 100 ml of an aqueous calcium chloride solution being stirred at 400
rpm. The concentration of CaCl2 in the solution ranged from 1 %
w/v to 3% w/v. The stirring was continued for one hour and the calcium
alginate beads were harvested by filtration, washed with distilled water,
and dried overnight in air.
Drug loading was carried out by two methods, designated as sequential
method and simultaneous method. In the sequential method, calcium alginate
beads were prepared as described in the previous paragraph. The wet beads
were then immersed and stirred for 1hr in a solution containing IBP
(concentration ranging from 2-3 % w/v), filtered and washed with distilled
water. IBP loaded calcium alginate beads were obtained by subsequent
drying. In the simultaneous method, the gelation of beads by calcium ions
occurred simultaneously with the drug loading into the beads. The sodium
alginate solution was introduced dropwise into CaCl2 solutions
(concentration ranging from 1-3 %w/v) which also contained IBP
(concentration ranging from 2-3% w/v). After 1hr of interaction, the beads
were removed from the counter ion solution. The drug loaded beads were
washed and dried in a manner similar to that of blank beads (beads without
drug).
Drug Entrapment Efficiency
Alginatebeads (20 mg) were accurately weighed in an electronic balance
(Precisa XB 600 MC, Precisa Instrument Ltd; Switzerland), immersed in 250
ml USP phosphate buffer (PB) solution (PH-6.8), and shaken for 2h on a
mechanical shaker. The beads were crushed and further shaken for 1h. The
solution was filtered and an aliquot following suitable dilution was
analyzed at 222 nm in a UV-Visible spectrophotometer (model Cary-50
Bio-spectrophotometer, VARIAN, Australia)) and the content of the beads was
determined using a calibration curve constructed using PB solution of PH
6.8. The reliability of the above analytical method was judged by
conducting recovery analysis at three levels of spiked drug solution in the
presence or absence of the polymers for three consecutive days. The
recovery averaged 98.45±2.68 %. DEE was determined using the following
relation:
DEE (%) = (Determined drug content / Theoretical drug content) ×100
Particle size distribution
The particle size determination of IBP loaded calcium alginate beads were
carried out using an optical microscope along with a stage micrometer
having an accuracy of 0.01mm. A suspension of beads in liquid paraffin was
prepared in a beaker and then one drop of the same was dropped on a clean
glass slide and covered with a cover slip. The average sizes of 100 beads
were determined for each formulation using the calibration factor. The
average diameter of the beads was calculated using the following formula:X
=
X = average particle diameter, Xi = Individual diameter of
beads, N = Number of beads
Scanning Electron Microscopy
The surface morphology of drug loaded beads obtained from various
percentages of polymer, CaCl2 and drug were studied by using a
scanning electron microscope (model JEOL JSM-6360, Japan). The beads were
mounted on an appropriate stub and then coated with carbon and gold (100
and 50Å thickness respectively) sputter module in a vacuum evaporator in an
argon atmosphere. The coated samples were then observed under scanning
electron microscope operated at 15KV.
Furrier Transformed Infra Red analysis
The IR analysis of pure drug, polymer, and drug loaded beads prepared by both the methods were
analyzed with FTIR spectrophotometer (Shimadzu FTIR-8400, Japan). All the
samples were crushed with potassium bromide to get pellets at 600kg cm-2. Spectral scanning was done in the range of 400-4000 cm -1.
X-ray Diffraction Study
To understand the crystalline state of the drug in the polymer matrix, the
X-ray diffraction pattern of drug loaded beads was performed and compared
with that of pure drug. Powder forms of the samples were exposed to Cu
radiation (30kv × 15mA) in a wide-angle X-ray diffractometer
(MiniflexgonioMeter, Japan). The instrument was operated in continuous mode
in increments of 1°/min and scanned over a 2Ɵ range of 10 to 90°.
In-vitro Drug Release Study
In-vitro drug release study was carried out in acidic solution 0.1(N) HCl
(PH-1.2) and in USP PB solution (PH 6.8) using USP-ll dissolution rate test
apparatus (model TDP-06P Electro Lab, Mumbai, India). 20 mg beads were
placed in 500 ml acidic solution or 500 ml PB solution (37±1˚C) and rotated
with paddle at 75 rpm. Aliquot was withdrawn at different times and
replenished immediately with the same volume of fresh solution. Undiluted
or suitably diluted withdrawn samples were analyzed spectrophotometrically
at 220 nm for acidic solution and 222 nm for PB solution. The amount of
drug released in acidic solution and PB solution were calculated from the
calibration curves drawn respectively, in 0.1(N) HCl and PB solution (PH
6.8). Each release study was conducted four times.
RESULTS AND DISCUSSION
In this investigation, a simple and inexpensive method was developed for
the preparation of calcium alginate beads. Crosslinking of sodium alginate
was done using CaCl2 and IBP was loaded in the same. Various
compositions of the formulation variables were used for the present study
are given intable 1.
Formulation code
|
Formulation variables
|
|
Conc. of CaCl2 (% w/v)
|
Conc. of sodium alginate (%w/v)
|
Drug (% w/v)
|
A1
|
1
|
2
|
2
|
A2
|
1
|
2
|
3
|
A3
|
1
|
2.5
|
2
|
A4
|
1
|
2.5
|
3
|
B1
|
2
|
2
|
2
|
B2
|
2
|
2
|
3
|
B3
|
2
|
2.5
|
2
|
B4
|
2
|
2.5
|
3
|
C1
|
3
|
2
|
2
|
C2
|
3
|
2
|
3
|
C3
|
3
|
2.5
|
2
|
C4
|
3
|
2.5
|
3
|
Table 1:
Composition of IBP loaded calcium alginate beads prepared by sequential and
simultaneous method.
Particle size was in the range of 1005 µm to 1075 µm for the beads obtained
using the sequential method and 1057 µm to 1207 µm for those from the
simultaneous method(table 2). The particle size of the beads prepared by
the simultaneous method decreases with increased in CaCl2
concentration.
Formulation code
|
Mean particle size (µm±sd, n=3)
|
Drug loading
(% ±sd , n=3)
|
Sequential method
|
A3
|
1065±0.01
|
53.22±0.02
|
B3
|
1060±0.01
|
58.15±0.01
|
C2
|
1057±0.01
|
45.21±0.02
|
C3
|
1005±0.25
|
62.15±0.01
|
C4
|
1075±0.01
|
56.28±0.05
|
Simultaneous method
|
A4
|
1207±0.5
|
46.89±0.01
|
B2
|
1158±0.75
|
52.02±0.03
|
B3
|
1151±0.25
|
55.32±0.01
|
B4
|
1106±0.25
|
58.28±0.02
|
C4
|
1057±0.50
|
55.60±0.03
|
Table 2:
Effect of sodium alginate, CaCl2, and IBP concentration on
particle size, and drug loading.
Scanning Electron Microscopy
The surface morphology of the prepared beads was studied by scanning
electron microscopy (SEM) and the SEM photographs are given in figure 1.
SEM photographs of the blank beads when compared with drug loaded beads
show difference in surface morphology for both the sequential and
simultaneous method. Smoothness increase when drug was loaded in the beads.
The SEM photographs of the drug loaded beads (fig. 1[A]) show that the drug
is dispersed in the polymeric matrix without having any coat, which further
confirms that this system is a polymeric matrix system for beads prepared
by both sequential and simultaneous methods.
FIGURE 1: [A] SEM photographs of IBP loaded calcium alginate beads prepared
by sequential method (a) Drug loaded bead (b) After dissolution
[B] SEM photographs of IBP loaded calcium alginate beads prepared by
simultaneous method (c) Drug loaded bead (d) after dissolution
The SEM photographs presented in the fig. 1[B] also show difference in
surface morphology of the prepared beads before and after the completion of
in-vitro dissolution study for both the sequential and simultaneous
methods. The surface of beads after dissolution was rougher than before
dissolution.
Drug loading
Drug loading was found to be in the range of 42-62% for beads prepared by
the sequential method and 39-58% for the simultaneous method. Drug loading
was found to be directly proportional to polymer concentration [10] in both
the methods. But the effect of crosslinking agent and drug concentration on
drug loading was different in both methods.
Higher loading efficiency was obtained as the concentration of alginate
increased. This may be attributed to the greater availability of active
calcium binding sites in the polymeric chains and consequently, the greater
degree of crosslinking as the quantity of sodium alginate increased [11].
For the sequential method, batch C3 had the highest drug loading (62%) and
the use of drug concentrations greater than 2% w/v did not result in
further enhancement of drug loading.
It was observed that the efficiency of loading IBP into the calcium
alginate beads by the simultaneous method was lower than by the sequential
method [12]. For the simultaneous method, batch B4 had the highest drug
loading (58%). When the drug loading was carried out by the simultaneously
with the gelation of alginate by Ca+2, the counterion solution
contained both the drug molecule and CaCl2. The drug molecules
and Ca+2 ions diffuse in the same direction, from the solution
into the sodium alginate solution and competed simultaneously for common
binding sites along the alginate chains. The amount of associated Ca +2 ions (and the drug molecules) in the beads was a function of
the concentration ratio of CaCl2: IBP in the solution.
Increase in CaCl2 concentration from 1 to 3%, polymer
concentration from 2 to 2.5% and drug concentration from 2 to 3% resulted
in a corresponding increase in the drug entrapment from the 53% to 62%,
from 45% to 62% and decrease from 62% to 42% respectively for the
sequential method. Similarly in the simultaneous method increase in drug
entrapment from 47% to 58%, from 52% to 58% and from 55% to 58%
respectively was observed.
Furrier Transformed Infra Red analysis
FTIR spectral data were used to confirm the chemical stability of Ibuprofen
in alginate beads. FTIR spectra of pure drug, sodium alginate, IBP loaded
calcium alginate beads prepared by sequential and simultaneous method were
compared infig. 2.The characteristics bands corresponding to C=O stretching
and –OH stretching of IBP appeared in FTIR spectrum respectively at 1720cm -1 and 2956cm-1. The spectra obtained from drug
loaded beads prepared by both the methods, indicate the presence of the
characteristics bands of the drug at almost the same wave number.
FIGURE 2: FTIR spectra of IBP (A), Sodium alginate (B), IBP loaded beads
prepared by sequential method(C), IBP loaded beads prepared by simultaneous
method(D)
X-ray Diffraction Study
In order to confirm the physical state of the drug in the beads, data for
the X-ray diffraction studies of the pure drug, polymer, empty beads and
beads containing the drug carried out is shown in fig. 3. No characteristic
XRD pattern was observed in the case of drug loaded beads. Thus from the
X-ray diffraction data of the drug loaded beads, it can be inferred that
the drug was not present in the crystalline state in the bead matrix. It
was in the amorphous state. This clearly indicated that changes in the
crystalline state of the drug occurred during the preparation of the beads
by this ionotropic gelation method.
FIGURE 3: X ray diffractogram of IBP (A), Sodium alginate (B), IBP loaded
beads prepared by sequential method(C), IBP loaded beads prepared by
simultaneous method(D)
In-vitro drug release
The release profile of IBP in enzyme free simulated gastric fluid (SGF)
followed by enzyme free simulated intestinal fluid (SIF) from the calcium
alginate beads prepared under different conditions have been represented in
fig. 4-6. The drug release from the alginate beads depends on the
penetration of the dissolution medium into the beads, the eventual swelling
and dissolution of alginate matrix and the dissolution of the drug
subsequent to leaching through the swollen matrix. In SGF alginate beads
prepared by the sequential method IBP releases about 30-40 % drug in first
2h. And after that rest of the drug releases in the SIF which continues
upto 9h where by it releases 82-89% of the drug. It was found that drug
release is accompanied by a burst release which may be due to the highly
water soluble nature of the drug.
FIGURE 4: Effect of sodium alginate concentration on IBP release from
calcium alginate beads (a) Sequential method (b) simultaneous method.
(Maximum SEM ±3.70%, n= 4).
i. Effect of polymer
To study the effect of sodium alginate concentration on IBP release, two
different concentrations, 2 and 2.5% w/v were used. Fig. 4 shows the
influence of the concentration of sodium alginate solution on Ibuprofen
release behavior from calcium alginate loaded beads prepared by sequential
and simultaneous method. Lower concentrations of sodium alginate led to
faster drug release, with 89.05±0.178% of drug release within 9h in
sequential method. Increase in alginate concentration decreases the release
rate. Thus the results indicate that drug release was directly proportional
to sodium alginate concentration [11, 13]. The principal gelation or
cross-linking of sodium alginate with CaCl2 is based on the
tight junction between the guluronic acid residues [14]. The number of the
apparent cross-linking points formed within increases with increasing
alginate concentration in the formulation. This can be correlated with the
particle size studies where as the alginate concentration increased the
particle size decreased due to the formation of more rigid and compact
matrix, consequently retarding the IBP release.
In the case of IBP loaded calcium alginate beads prepared by simultaneous
method similar behavior was also observed.
FIGURE 5: Effect of CaCl2 concentration on IBP release from
calcium alginate beads (a) Sequential method (b) simultaneous method.
(Maximum SEM ±2.50%, n= 4).
ii. Effect of CaCl2
The release behavior of calcium alginate beads prepared by sequential
method with different concentrations of CaCl2 (1-3% w/v) is
indicated in fig. 5. Drug release was sustained from 38% to 30 % in SGF for
2h and 89% to 82 % in SIF fluid upto 9h with increasing CaCl2
concentration. Thus in the sequential method as the concentration of
crosslinking agent increased, drug release decreased. Beads prepared with
3% w/v CaCl2 showed the most sustained release effect due to
more crosslinking resulting in the formation of amore rigid gel network and
hence greater sustained release characteristics. It was confirmed by
particle size studies, where the size of the beads was found to be
decreased as the concentration of crosslinking agent increased [10]. It was
also evident from the literature [14] that diffusion of drug from alginate
matrix decreased as the concentration of CaCl2 solution
increased in sequential method, probably due to more number of
cross-linking with sodium alginate.
In simultaneous method IBP releases was sustained from 30% to 37% in SGF
for 2h and from 93% to 82% in SIF upto 9h (Fig. 5). But in case of
simultaneous method 3% crosslinking agent does not show the highest
sustained effect. It may be due to the low drug loading [12].
FIGURE 6: Effect of IBP concentration on IBP release from calcium alginate
beads (a) Sequential method (b) simultaneous method. (Maximum SEM ±3.30%,
n= 4).
iii. Effect of drug concentration
It was found that drug releases within the 1st hour indicative
of a burst effect. This could be attributed to the highly water soluble
nature of the drug. Similar result was found by Ray et al, [15] during
preparation of diltiazem resin complex loaded carboxymethyl xanthan beads.
The effect of drug concentration during in-vitro drug release study does
not affect the drug release from the calcium alginate beads. The drug
concentration was varied from 2 to 3% w/v to study the effect of drug
release shown infig. 6.IBP release from beads prepared by sequential method
(batch C3) which contained 2% w/v IBP shows more sustained effect with drug
loading of about 62%.
But in case of simultaneous method (batch B4) which contains 3% w/v drug
shows the more sustained effectwith drug loading of about 58%. It was found
that drug release was greatly dependent on the drug loading.
CONCLUSION
Ibuprofen was entrapped in calcium alginate bead prepared with sodium
alginate by ionotropic gelation method using calcium chloride as a
crosslinking agent. The drug was incorporated by two methods, sequential
and simultaneous method. Beads produced by the former method had higher
drug entrapment. The beads were evaluated for drug entrapment, particle
size and release characteristics in enzyme free simulated gastric and
simulated intestinal fluid. The drug entrapment in sequential method
increases with increased CaCl2 and polymer concentration but it
decreased with increased drug concentration. And in simultaneous method
drug entrapment increases with polymer and drug concentration increased and
it increased to a certain extent with increase in the concentration of CaCl 2 and after further increase it decreased. Drug release was
directly proportional to the polymer concentration for the drug loaded
beads prepared by both the methods. Increase in CaCl2
concentration retarded the drug release in sequential method and for the
simultaneous method the retardation in drug release is upto a certain
concentration of CaCl2. The drug concentration exhibits a drug
loading dependent effect on the release behavior in both the methods.
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