African Journal of Pharmacy an

African Journal of Pharmacy and Pharmacology, Vol. 4(2) pp. 035-054, February 2010
Available online
ISSN 1996-0816 (c) 2010 Academic Journals
Full Length Research Paper
A comparative study for interpenetrating polymeric
network (IPN) of chitosan-amino acid beads for
controlled drug release
Manjusha Rani1, Anuja Agarwal1, Tungabidya Maharana2 and Yuvraj Singh Negi2*
1Department of Chemistry, J. V. Jain College, Saharanpur (U. P.) India.
2Polymer Science and Technology Program, Department of Paper Technology,
Saharanpur Campus, Indian Institute of Technology, Roorkee, Saharanpur (U. P.) India.
Accepted 13 January, 2010
The paper addresses development of novel pH sensitive interpenetrating polymeric network (IPN)
beads composed of chitosan-glycine-glutamic acid cross linked with glutaraldehyde and their use for
controlled drug release. A comparative study has been carried out on these IPN beads with the beads
that of chitosan, chitosan-glycine and chitosan-glutamic acid cross linked with glutaraldehyde. The
beads were characterized by FTIR to confirm the cross linking reaction and drug interaction with cross
linked polymer in beads, scanning electron microscopy (SEM) to understand the surface morphology
and internal structure and DSC to find out the thermal stability of beads. The swelling behavior of the
beads at different time intervals was monitored in solutions of pH 2.0 and pH 7.4. The release
experiments were performed in solutions of pH 2.0 and pH 7.4 at 37°C using chlorpheniramine maleate
(CPM) as a model drug. The swelling behavior and release of drug were observed to be dependent on
pH, degree of cross linking and their composition. The results indicate that the newly constructed cross
linked IPN beads of chitosan-glycine-glutamic acid might be useful as a vehicle for controlled release of
drug. The kinetics of drug release from beads was best fitted by Higuchi’s model in which release rate
is largely governed by rate of diffusion through the matrix.
Key words: Cross-linked beads, chitosan, chlorpheniramine maleate, glycine, glutamic acid, controlled drug


Polymers from natural resources have been studied in
the recent past as the important material for biotech-
nological and biomedical application owing to their unique
characteristics such as biological compatibility with
natural environment, non-toxicity and biodegradability.
Deacetylated product of chitin provides a polysaccharide
(1 4) 2 amino-2 deoxy – D glucan which is known as
the chitosan and is one of the well known biodegradable
polymers metabolized by human enzymes. Chitosan can
be prepared as hydrogel beads, having a positive charge
at metabolic and physiological pH, bioadhesivity and
water holding capacity enhanced in tissues of human
body for extended period of time. Three dimensional hydro-
*Corresponding author. E-mail:
Tel: +91-132-2714328.

philic polymer network of hydrogel beads are capable of
retaining large amount of water or bio fluids. Hydrogels
are thermodynamically compatible with water and exhibit
swelling in aqueous media. Hydrogels has resemblance
with natural living tissues due to their high water retention
capacity. Cross linked hydrogel network can be obtained
by cross linking chitosan by using a cross linker like
glutaraldehyde. Their properties depend mainly on the
cross linked density (the ratio of moles of cross linking
agent to the moles of polymer repeating units). Formation
of hydrogel network requires a critical number of cross
links per chain and it forms porous struc-ture whose pore
size depends upon swelling of beads which in turn
depends on external environment.
Currently, chitosan is the preferred material for con-
trolled drug delivery devices (Machida et al., 1989; Chein
and Yie, 1983; Yao et al., 1994; Yuji et al., 1996; Chandy
and Sharma, 1992; Chandy and Sharma, 1993; Hou et al.,

036 Afr. J. Pharm. Pharmacol.
Table 1. Composition of IPN beads and alignment of the column (Glutaraldehyde %)
Bead type Chitosan (g) Glycine (g) Glutamic acid (g) 2% acetic acid (ml) Glutaraldehyde (%)







1985; Miyazaki et al., 1981; Lee et al., 1997). The use in
the development of oral sustained release preparation is
based on the intra gastric floating tablets of chitosan
(Sheth and Tossounian, 1984; Inouye et al., 1988).
Moreover, the antacid and anti ulcer charac-teristics of
chitosan prevents or weaken drug irritation in the
stomach (Hou et al., 1985). Therefore, chitosan has great
potential for its use as a suitable carrier in controlled drug
delivery systems. However, there have been some
reports on chitosan based beads cross linked with
glutaraldehyde as oral drug delivery system com-posed
of chitosan and one of the amino acids like glycine
(Gupta and Ravi Kumar, 2000), glycine, glutamic acid
(Kumari and Kundu, 2008) and alanine (Kumari and
Kundu, 2007) to obtain beads for oral drug delivery. Our
present study is an attempt to develop cross linked beads
composed of chitosan and two amino acids as spacer
groups cross linked with glutaraldehyde for sustained
release of chlorpheniramine maleate as a model drug
and to compare it with cross linked beads of chitosan and
chitosan-amino acid. We have prepared four types of
beads cross linked with glutaraldehyde (a) chitosan (b)
chitosan-glutamic acid (c) chitosan-glycine (d) chitosan-
glycine-glutamic acid having different composition to
investigate the comparative swelling behavior and
modeling drug release properties.

Chitosan was purchased by India Sea Food, Kerala and was used
as received. Its percentage of deacetylation after drying was 89%.
Chlorpheniramine maleate (CPM), C16H19ClN2C4H4O4 was obtained
as a gift sample from Sarthak Biotech Pvt. Ltd., HSIDC, Haryana,
India. Glutaraldehyde, glycine and monosodium glutamate were
procured from SD Fine Chemicals Ltd., Mumbai, India, Sisco
Research Laboratories Pvt. Ltd., India and Reidal Chemicals, India
respectively. All other chemicals used were of analytical grade.
Double distilled water was used in throughout the studies.

Preparation of semi-interpenetrating polymer network (IPN)
Different IPN beads (A1 – A7) varying in composition were prepared
separately. Their composition is described in Table 1. Weighed
quantity of chitosan and amino acid were dissolved in 40 ml of 2%

acetic acid by weight and stirred for three hours using magnetic
stirrer at room temperature. The homogeneous mixture was extru-
ded in the form of droplets using a syringe into NaOH-methanol
solution (1:20 w/w) under stirring condition at 400 rpm. The beads
were washed with hot and cold water respectively. The resultant
beads were allowed to react with glutaraldehyde solution as given
in Table 1 at 50°C for about 10 min. Finally, the cross linked IPN
beads were successively washed with hot and cold water followed
by air drying.
Drug loaded beads of same composition were also prepared
separately by adding a known amount of CPM (150 mg, 200 mg)
respectively to the chitosan, amino acid mixture before extruding
into the NaOH- methanol solution.

Swelling studies
Swelling behavior of chitosan beads (A1 – A7) were studied in
different pH (2.0 and 7.4) solutions. The percentage of swelling for
each sample at time t was calculated using the following formula.
Percentage of swelling = {(Wt -Wo)/Wo} x 100
Where; Wt = weight of the beads at time t after emersion in the
solution. Wo = weight of the dried beads.

Drug loading assay
Accurately weighed (0.1 g) drug loaded sample was kept in 100 ml
of 2% acetic acid for 48 h. After centrifugation the CPM in the
supernatant was assayed by Spectrophotometer at 193.5 nm.

Drug release studies
The drug release experiments were performed at 37°C under
unstirred condition in acidic (pH 2.0) and basic (pH 7.4) solution.
Beads (0.1 g) containing known amount of the drug were added to
the release medium (30 ml). At pre decided intervals, samples of 2
ml aliquots were withdrawn, filtered and assessed by recording the
absorbance at 193.5 nm. The cumulative CPM release was
measured as a function of time.

Kinetic analysis of drug release
A fair amount of work has been included in literature on kinetics of
drug release (Agnihotri et al., 2004; Laszlo et al., 2006). A large
number of modified release dosage forms contain some sort of
matrix system and the drug dissolves from this matrix. The diffusion

Rani et al. 037
Figure 1(a). Swelling behavior of cross linked A1-A4 beads as a function
of time in solution pH 2.0 and pH 7.4 at 37°C.
pattern of the drug is dictected by water penetration rate (diffusion
controlled) and thus the Higuchi’s equation (Higuchi, 1963)
relationship applies
Mt/M = k t 1/2
Where; Mt/M is the fractional drug release at time t and k is a
constant related to the structural and geometric properties of the
drug release system. According to Higuchi’s model, an inert matrix
should provide a sustained drug release over a reasonable period
of time and yield a reproducible straight line when the percentage of
drug released is plotted versus the square root of time.

Characterization of IPN beads
FTIR spectra of IPN beads
FTIR spectra of IPN beads were recorded using a thermo Nicolet
Avatar 370 FT-IR spectrometer system using KBr pellets.

Scanning electron microscopy (SEM)
The shape and surface morphology of the beads were examined
using FESEM QUANTA 200 FEG model “(FEI, the Netherlands
make)” with operating voltage ranging from 200 V to 30 kV. FESEM
micrographs were taken after coating the surfaces of bead samples
with a thin layer of gold by using BAL-TEC-SCD-005 Sputter Coater
(BAL-TEC AG, Balzers, Liechtenstein company, Germany) under
argon atmosphere. SEM was used to perform textural charac-
terization of full and cross sectioned IPN beads, magnification were
applied to each sample in order to estimate the morphology and
interior of the bead.

Thermal analysis
Thermal gravimetric analysis (TGA), Differential thermal gravimetric
(DTG) and Derivative thermal analysis (DTA) were carried out
simultaneously by using a (PYRIS Diamond). TG/DTA thermal
analyzer model DSC-7, supplied by Perkin Elmer and the data was
processed and analyzed by PYRIS muse measure and standard
analysis software (V. 3.3U; #. 2002 Seiko instruments Inc.). The

sample was kept in alumina pan, the reference material was
alumina powder and study was carried out at heating rate of
10°C/min under 200 ml/min flow rate of air or nitrogen atmosphere.
Indium and gallium were used as standards for temperature

Swelling studies
The percentage swelling of chitosan beads (A1 – A4)
cross linked with glutaraldehyde in solution of pH 2.0 and
7.4 is shown in Figure 1(a). It was observed that swelling
rate followed order as follows
At pH -2.0 A2 < A1 <A3 <A4
At pH 7.4 A3 < A1 <A4 <A2
When the cross linked beads were placed in the solution,
the solution penetrates into the bead and the beads sub-
sequently try to swell. Generally, the swelling process of
the beads in pH < 6 involves the protonation of amino/
imine groups in the beads and mechanically relaxation of
the coiled polymeric chains. Initially during the process of
protonation, amino/imine groups of the bead surface
were protonized which led to dissociation of the hydrogen
bonding between amino/imine group and other groups.
Afterward, protons and counter ions diffused into the
bead to protonate the amino/imine groups inside the
beads and dissociating the hydrogen bonds. (Gupta and
Kumar, 2000; Gupta and Kumar, 2001). For chitosan –
glycine beads percentage of swelling in acidic solu-
tion was found to be higher than in basic solution which is
due to inherent hydrophobicity of the chitosan beads
dominating at high pH value, thus preventing faster
swelling in neutral and alkaline media but in case of
chitosan-glutamic acid beads, percentage of swelling in
basic solutions was found to be higher than in acidity

038 Afr. J. Pharm. Pharmacol.

Figure 1(b). Swelling behavior of cross linked A4-A7 beads as a function of time in
solution pH 2.0 and pH 7.4 at 370C.
in acidic solution which may be due to the presence of
free carboxylic ends of the chitosan-glutamic acid IPN
and the free carboxylic ends are more likely to be
attacked by basic solution.
In case of chitosan-glycine-glutamic acid beads, their
rate of swelling was also found to be higher at pH 2.0
than chitosan-glutamic acid and chitosan-glycine beads
and at pH 7.4, their rate of swelling is intermediate
between chitosan-glutamic acid and chitosan-glycine
beads. Thus it was concluded that over all rate of
swelling was affected by glycine when chitosan-glycine-
glutamic acid beads were subjected to swelling studies.
The swelling behavior of the cross linked chitosan-
glycine-glutamic acid beads (A4 – A7) as a function of
time in solution pH 2.0 and pH 7.4 has been shown in
Figure 1(b). It was observed that the swelling rate was
decreased on increasing concentration of cross linker
glutaraldehyde. The observed swelling rates of A4 cross
linked beads were found to be higher than the swelling
rates of A5 bead, because in A5 beads the higher
concentration of glutaraldehyde increased the degree of
cross linking, which decreased the degradation of cross
linked polymer. Further, the percentage of swelling was
found to be higher in acidic solution than in basic
The change in amino acids composition, (that is,
decrease in glutamic acid concentration and increase in
glycine concentration) of cross linked bead (A6) having
same concentration of glutaraldehyde as compare to A4
bead has also been studied and observed that the
increase in concentration of glycine decreased the swel-
ling percentage of chitosan-glycine-glutamic acid beads
in basic solution while increased in acidic solution.
The percentage of swelling of the cross linked beads

having the same concentration of cross linker decreased
(A7 < A4) with increasing concentration of chitosan (A7 >
A4). It can be explained as the percentage of amino
acids acting as a spacer increased in A4 beads (25 %)
as compared to A7 beads (22.7 %) and also chitosan
percentage decreased in A4 beads (50 %) as compared
to A7 beads (54.5 %), the pore size of A7 beads also
decreased and the penetration of solution into the beads
become difficult, which result in lesser degree of swelling
(Kumari and Kundu, 2008).
SEM studies

SEM micrographs of dried beads (A1 – A7) and their
surface morphology are shown in Figures 2a and b while,
the cross sectioned dried beads and their internal
structure are shown in Figures 3a and b. It was
concluded from Figures 2a and b that the beads were
nearly spherical or some what oval in shape and their
approximate size varied from 1.2 to 1.8 mm. Cross linked
chitosan amino acid beads (A2 – A7) had rough, rubbery,
fibrous and folded surfaces as com-pared to chitosan
beads (A1) which had relatively smooth surfaces with
few wrinkles. With the higher concentration of cross
linker, in case of A5 the chains come closer to each other
and exhibit a regular, fibrous structure as compared to A4
having lower concentration of glutaraldehyde. A7 beads
constituting higher concentration of chitosan showed
more regular fibrous surfaces as compared to A4 due to
the smaller concentration of spacer amino acid. Due to
this reason the chain came closer to each other despite
of having the same degree of cross linker. The internal

Rani et al. 039

Figure 2a. SEM photographs of chitosan-amino acid cross linked beads (A1 – A4) and their morphology
(A1*- A4*).

040 Afr. J. Pharm. Pharmacol.

Figure 2b. SEM photographs of chitosan-amino acid cross linked beads (A5 – A7) and their Morphology (A5*- A7*).

Rani et al. 041
Figure 3a. SEM photographs of cross sectioned chitosan-amino acid cross linked beads (A1 – A4)
and their internal structure (A1*- A4*).

042 Afr. J. Pharm. Pharmacol.
Figure 3b. SEM photographs of cross sectioned chitosan-amino acid cross linked beads (A5 – A7)
and their internal structure (A5*- A7*).
structure of beads appeared to have micro pores as were
seen in SEM (Figures 3a and b).

FTIR studies
Figure 4(a) shows the FTIR spectra of chitosan powder,
glutamic acid, glycine and A1 – A7 drug unloaded beads.
An FTIR spectrum of chitosan powder curve (A) has
shown two peaks around 894 and 1171 cm -1 corres-
ponding to saccharide structure (Yoshioka et al., 1990).
The observed peak at 1613cm -1 can be assigned as
amino absorption peak. The absorption peak for amide
were observed at 1639 and 1319 cm -1 and observed
formation mode (Peng et al., 1994; Sannan et al., 1978).
A broad band appearing around 1083 cm -1 indicated
the >CO-CH3 stretching vibration of chitosan. Another

broad band at 3450 cm -1 was due to the amine N-H
symmetric stretching vibration which might be due to
typical of C-H stretching vibration. simultaneously the
peak assigned for amino absorption at 1613 cm -1 in
original chitosan broadened or disappeared in cross
linked beads and a new peak appearing at about 1567
cm -1 due to imine bond (-C=N-) which was formed as a
result of cross linking reaction between amino group in
chitosan and aldehydic group in glutaraldehyde (Bellamy,
1980; Lee et al., 1999) in curve A5 – A7. However this
was due to the overlapping of peaks corresponding to –
the original chitosan with that of imino (-C=N-) stretching
group of chitosan and aldehyde group of glutaraldehyde
in A2 – A4. A reaction taking place in the formation of

Rani et al. 043
Figure 4(a). FTIR spectra of glutamic acid (A), glycine (B), chitosan powder (C) and drug unloaded cross
linked beads (A1 – A7).
cross-link is as follows
-NH2 + O=HC- -N=CH-
Amino aldehyde imino
(Chitosan) (Glutaraldehyde) (Cross link)
On increasing the glutaraldehyde concentration, the peak

in A5. All the curves A1 to A7 showed additional peaks of
amino acid. FTIR spectral data of drug loaded beads in
Figure 4b were used to confirm the chemical stability of
CPM in chitosan amino acid beads. FTIR spectra of pure
CPM drug (curve D) and CPM loaded cross-linked beads
(A1 – A7) in Figure 4b were compared with drug unloaded
cross-linked beads (A1 – A7) in Figure 4a.

044 Afr. J. Pharm. Pharmacol.
Figure 4(b). FTIR spectra of pure CPM drug (D) and drug loaded cross linked beads (A1 – A7).
CPM has shown characteristic band at 2966 and 2917
cm -1 due to aliphatic C-H stretching. The band at 1619
and 1588 cm -1 due to C=N stretching vibration. While
those of 1476 and 1432 cm -1 are due to aromatic C=C
stretching vibration. CPM has also shown characteristic
When drug was incorporated into the crosslinked
chitosan-amino acid beads, along with all the characteris-

tic band of the cross linked chitosan and amino acids,
additional band have appeared due to the presence of
CPM in the matrix. It indicates that CPM has not
undergone any chemical change with in the beads.

TGA experiments were carried out on chitosan, glutamic

Rani et al. 045
Figure 5(a). TG curves for chitosan powder (A), glutamic acid (B), glycine (C) and drug unloaded cross
linked beads (A1-A7).
acid, glycine and cross linked drug unloaded beads A1 –
A7 and the curve obtained are presented in Figure 5a
which clearly shows that approximately 10% weight loss

free water. After this, weight loss remains constant up to
249°C. A sudden weight loss is observed after 249°C and

046 Afr. J. Pharm. Pharmacol.
Figure 5(b). TG curves for pure CPM drug (D) and drug loaded cross linked beads (A1-A7).

the total weight loss at 400°C is about 60%, where as
pure chitosan cross linked beads (A1) shows weight loss
after 200°C and weight loss at 400°C is approximately
46%, lesser than chitosan powder this shows that cross
linking of chitosan with glutaraldehyde increases its
thermal stability. Similarly, chitosan-glutamic acid, chitosan-
glycine and chitosan-glycine-glutamic acid beads show
weight loss at 400°C about 50, 43, and 45% respectively
which clearly indicate that chitosan amino acid specially,

chitosan-glycine-glutamic acid beads are as thermally
stable as chitosan beads (A1) and thermal stability of
chitosan-glycine-glutamic acid beads is greater than
chitosan-glutamic acid beads and slightly lesser than that
of chitosan-glycine beads.
TG curves for CPM model drug (curve D) and drug
loaded crosslinked beads (A1 – A7) are shown in Figure
5b. CPM drug lost about 67% weight between 208 and
274°C (curve D) which was due to the decomposition of

Rani et al. 047
Figure 6(a). DTG curves for chitosan powder (A), glutamic acid (B), glycine (C) and drug unloaded
cross linked beads (A1 – A7).
of drug above its melting point. Melting point of CPM is
134°C and such a huge loss in weight was not shown by
drug loaded beads A1 – A7. This concluded that the drug
is quite stable with in the beads. DTG thermograms of
pure chitosan, glutamic acid, glycine and cross linked
beads A1 – A7 are presented in Figure 6a. These
indicated the rate of weight loss for chitosan powder was
highest at 290°C and cross linked chitosan beads showed

lesser rate of weight loss at 244°C. On comparing A1 –
A4 beads it can be concluded that chitosan-glutamic
acid-glycine beads were found to be most stable as the
loss weight at highest temperature (271°C) as compared
to chitosan beads at 244°C, chitosan-glutamic acid beads
at 249°C and chitosan-glycine beads at 268°C. DTG
curves for CPM drug and drug loaded crosslinked beads
are shown in Figure 6b. Curve D for pure CPM drug have

048 Afr. J. Pharm. Pharmacol.

Figure 6(b). DTG curves for CPM drug (D) and drug loaded crosslinked beads (A1-A7).
peaks for weight loss at 134, 207 and 256°C.
The comparison of drug unloaded beads A1-A7 in
Figure 6a and drug loaded beads A1 – A7 in Figure 6b
showed almost similar peaks with same rate of weight
lost also proved drug stability in the polymeric matrix.
DTA thermograms for pure chitosan, glutamic acid,
glycine and cross linked drug unloaded beads (A1 – A7)
are presented in Figure 7a. Thermograms for chitosan
powder showed one endothermic peak at 65°C due to
loss of free water and one exothermic peak at 296°C due
to chemical transformation. Glutamic acid gives two and
glycine gives one endothermic peak in their thermo
grams. While in case of (A1 – A4) beads only one exo
thermic peak is observed. It was concluded that chitosan-

glycine-glutamic acid beads are the most stable as in
thermo grams for A1 – A4 beads exothermic peak moves
towards higher temperature (240 to 274°C). DTA thermo
grams for pure CPM drug and drug loaded beads A1-A7
are represented in Figure 7(b). In case of CPM drug
(curve D) one endothermic peak and one exothermic
peak were observed. One at 134°C which corresponds to
melting process and other at 254°C to chemical
Drug loaded beads (A1 – A7) showed almost similar
thermo grams in which no peaks were observed at 134
and 254°C indicating the amorphous dispersion of drug
into the beads (Agnihotri and Aminabhavi, 2006; Kulkarni
et al., 2007).

Rani et al. 049
Figure 7(a). DTA curves for chitosan powder (A), glutamic acid (B), glycine (C) and drug
unloaded cross linked beads (A1 – A7).
Drug loading assay

When (1 g) drug loaded sample was kept in 100 ml 2%
acetic acid, the total drug released after 48 h was found
to be 78 µg and 142 µg for the beads incorporated with

150 and 200 mg of CPM respectively.

Drug release study
Figures 8a and b shows the release profile of CPM

050 Afr. J. Pharm. Pharmacol.
Figure 7b. DTA curves for CPM drug (D) and drug loaded cross linked beads (A1-A7).
from chitosan beads (78 µg of drug loaded bead) at
various time intervals in acidic (pH 2.0) and basic (pH
7.4) at 37°C. There was a burst release initially for the
first hour in both acidic and basic media followed by a
moderate release for next four hours and finally an
almost constant release of CPM from the matrix for the
studied period of 48 h. The amount and percentage of drug

released followed the order of swelling of beads. It is
because the release rate depends on swelling of the
beads. It was noticed that drug release was pH
dependent and followed the following order in acidic and
basic medium
At pH 2.0 A2<A1<A3<A4
Figure 8(a). Release of CPM for A1 – A4 beads (78 µg CPM
loaded beads) vs time in solution pH 2.0 and pH 7.4 at 37°C

Figure 8(b). Release of CPM for A4 – A7 beads (78 µg CPM
loaded beads) vs time in solution pH 2.0 and pH 7.4 at 37°C.

At pH 7.4 A3<A1<A4<A2
It has also been observed that the amount and
percentage of drug released were much higher in acidic
medium than in alkaline medium in case of chitosan (A1)
and chitosan-glycine (A3) beads while in case of
chitosan-glutamic acid (A2) beads, the release rate in
acidic and basic medium were entirely different and
amount and percentage of drug released was lower in
acidic media and higher in alkaline media. This may be
due to the different chemical structures of glycine and
glutamic acid.
The reason may be due to the presence of two
carboxylic ends of the cross linked chitosan-glutamic acid
beads. Since carboxylic group is more susceptible to be

Rani et al. 051

attacked by the basic solution, the drug release in the
acidic medium was less due to the interaction of acidic
solution with the polar group of beads. In case of
chitosan-glycine-glutamic acid beads, the amount and
percentage of drug release were higher in acidic medium
than in basic medium.
This concluded that glycine showed dominant effect
over glutamic acid and over all effect was governed by
glycine. Further, the release experiments were performed
for the beads with varying weight ratio of glutaraldehyde
(A5), amino acids (A6) and chitosan (A7). The observed
drug release was in following order
At pH 2.0 A7<A5<A4<A6
At pH 7.4 A6<A5<A7<A4.
It has been observed that beads (A5) having higher
concentration of glutaraldehyde showed lower release
rates as compared to beads (A4) having lower concen-
tration of glutaraldehyde. This was due to increase in
cross linked density, as the diffusion of drug from the
IPN depends on the pore size of polymer network
which increases with decrease in degree of cross linking.
The higher release rate was observed in case of bead A6
constituting higher concentration of glycine at pH 2.0
while slower release rate is observed at pH 7.4, this may
be due to the fact that chitosan-glycine beads show
higher swelling rates in acidic solution than in basic
solution while chitosan-glutamic acid beads possess
reverse behavior. Similarly, slower released rate was
observed for beads A7, having higher concentration of
chitoan than the beads A4 having lower concentration of
chitosan. Hence on, decreasing chitosan concentration
the release rate has found to be increased. Similar
results have been obtained by some researchers (Kumari
and Kundu, 2008; Kumari and Kundu, 2007).
To check the reproducibility of the result, the release
profile of CPM from the chitosan beads loaded with
higher amounts of drug (142 µg of drug loaded beads)
has also been studied in acidic pH 2.0 and basic pH 7.4
media as shown in Figures 9a and b. The release
pattern of the drug loaded beads has been found to be
similar irrespective of the amount of the drug loaded.
These observations have suggested that the total amount
of drug release from the chitosan beads has increased
with the increase in concentration of CPM. However, the
percentage of CPM released from the beads loaded with
a higher amount of drug was found to be lower in
comparison to the beads loaded with a lower amount.
This concluded that the mechanism of the drug release
due to the diffusion through swollen beads depends on
the percentage of swelling of beads.

Kinetic analysis of drug release.
In order to have an insight into the mechanism of drug
release behaviour, Higuchi’s model were best fitted into

052 Afr. J. Pharm. Pharmacol.

Figure 9a. Release of CPM forA1-A4 beads (142 µg CPM loaded
bead) vs. time in solution pH 2.0 and pH 7.4 at 37°C.

Figure 9b. Release of CPM for A4-A7 beads (142 µg CPM loaded
bead) vs. time in solution pH 2.0 and pH 7.4 at 37°C.

the kinetic data of drug release. Linear plots of percent
cumulative amount release versus square root of time is
shown in Figure 10 demonstrating that the release from
the crosslinked polymeric microsphere matrix is diffusion
controlled and obeys the Higuchi’s model (Jameela et al.,
The constant k, presented in Table 2 was calculated
from the slope of the linear portion of plot of percentage
of cumulative drug released versus the square root of
time. The value of k for the release process has been
found to be lower in solution of pH 7.4 than in solution of
pH 2.0 except for A2 beads. However, the values were
smaller which indicate mild interaction between the drug
and polymeric matrices (Orienti et al., 1996; Ganza-
Gonzalez et al., 1999).

Figure 10a. Plots showing drug release profile from A1-A4
beads (78 µg CPM loaded) in solution pH 2.0 and pH 7.4 by
fitting the Higuchi’s equation.

A4 pH 2 A5 pH 2 A6 pH 2 A7 pH 2
A4 pH 7.4 A5 pH 7.4 A6 pH 7.4 A7 pH 7.4
0 1 2 3
t 1/2

Figure 10b. Plots showing drug release profile from A4-A7 beads
(78 µg CPM loaded) in solution pH 2.0 and pH 7.4 by fitting the
Higuchi’s equation.
The observations of the present study have shown that
chitosan-glycine-glutamic acid beads posses a pH
dependent swelling behavior. It can be used successfully
for the formulation of controlled drug delivery devices.
They have optimum entrapping capacity for the studied
drugs and provide a sustained release of drugs for
extended periods which make them appropriate for
delivery of drug at a controlled rate.

Authors are grateful to Prof. B. Gupta, Bioengineering

Rani et al. 053
Table2. Results of drug release mechanism by fitting data in Higuchi’s model for CPM loaded beads.
pH 2.0 pH 7.4


CPM loaded beads with
78 µg 142 µg 78 µg 142 µg
K S.D. R K S.D. R K S.D. R k S.D R


.12 ±
.19 ±
.26 ±
.22 ±
.28 ±
.21 ±




± 012
± 015
± 015







Figure 10c. Plots showing drug release profile from A1-
A4 beads (142 µg CPM loaded) in solution pH 2.0 and
pH 7.4 by fitting the Higuchi’s equation.
Figure 10d. Plots showing drug release profile from A4-A7
beads (142 µg CPM loaded) in solution pH 2.0 and pH 7.4
by fitting the Higuchi’s equation.

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chitosan sample and technical help.

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