Journal of Biomaterials and Nanobiotechnology, 2011, 2, 71-84
doi:10.4236/jbnb.2011.21010 Published Online January 2011 (http://www.SciRP.org/journal/jbnb)
71
Characterization and Biodegradation Studies for
Interpenetrating Polymeric Network (IPN) of
Chitosan-Amino Acid Beads
Manjusha Rani1, Anuja Agarwal1, 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
Received December 4th, 2010; revised December 16th, 2010; accepted December 20th, 2010.
ABSTRACT
The paper describes the synthesis of pH sensitive interpenetrating polymeric n etwo rk (IPN) beads composed of chitosan,
glycine, glutamic acid, cross linked with glutaraldehyde and their use for controlled drug release. The drug was loaded
into beads by varying their composition such as, amount of crosslinker glutaraldehyde, ratio of chitosan, glycine and
glutamic acid. The beads were characterized by fourier transform infrared (FTIR) spectroscopy to confirm the cross
linking reaction and drug interaction with crosslinked polymer in beads, Scanning Electron Microscopy (SEM) to un-
derstand the surface morphology and Differential scan ning calo rimetry (DSC) to find out the therma l stability o f beads.
X-Ray Diffraction (XRD) investigation was carried out to determine the crystalline nature of drug after loading into
chitosan-glycine-glutamic acid IPN beads. Results indicated amorphous dispersion of chlorpheniramine maleate (CPM)
in the polymeric matrix. The swellin g behavior of the beads a t 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 chlor-
pheniramine maleate (CPM) as a model drug. The swelling behavior and release of drug were observed to be dep end-
ent on pH, degree of cross linking and their composition. Th e results indicate that the cross linked IPN beads of chito-
san-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 ma-
trix.
Keywords: Cross-Linked Beads, Chitosan, Chlorpheniramine Maleate, Glycine, Glutamic Acid, Controlled Drug
Release
1. Introduction
Recently efforts have been made to design novel drug
dosage formulations so that more and more effectiveness
could be altered to the conventional dosage forms. To
achieve this goal controlled release technology had de-
veloped the commercial methodology by which pre de-
cided and reproducible release of drug up to therapeutic
level into a specific environment over a prolonged time
period could be maintained. Such drug delivery systems
function according to the changes in physiological sig-
nals with in the body and target the drug for the site of
action to minimize any side effect. Nano and micro beads
of polymers have been formulated using polymeric mate-
rial either synthetic or natural [1-3] origin. Therapeutic
molecules complexed by beads of polymers capable of
forming gel, may also be released by diffusion. Hence,
drug delivery system require polymeric matrix which
would be non toxic, biocompatible, biodegradable.
Chitosan is such a valuable natural biocompatible
polymer, nontoxic, biodegradable [4,5], mucoadhesive
[6,7], easily bio absorbable [8] and also posses gel form-
ing ability at low pH [9]. Moreover, it has antacid and
anti ulcer activities [10,11] which prevent or weaken
drug irritation in the stomach. All these interesting prop-
erties of chitosan make this natural polymer an ideal ele-
ment for formulating drug delivery devices [12-15] and
this material has been used to form drug carrying systems
for several biomedical purposes [16-20] and also for
gene therapy [21-23] to suture and wound healing [24]
materials, vascular grafts [25] and cartilage regeneration
[26] among many other applications [27,28].

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 72
Chitosan is obtained by N-deacetylation of chitin
which is naturally abundant muco polysaccharide and
forms the exoskeleton of crustaceans, insects etc. It is
well known to consist of 2-acetamido 2-deoxy
β-D-glucose through a β (1→4) linkage [29]. Thus, chi-
tosan is a hetero polymer having (1→4) 2-amino 2-deoxy
β-D-glucose unit with (1→4) 2-acetamido-2 deoxy
β-D-glucose units of original chitin in polymeric chain.
The ratio of 2-amino-2-deoxy β-D-glucose unit to
2-acetamido-2-deoxy β-D-glucopyranose is an important
parameter called as degree of deacetylation which deter-
mines its solubility and solution or gel forming properties.
Chitosan is highly basic polysaccharide. It is soluble in
dilute acids. It posses property of forming hydrogels
which are highly swollen hydrophilic polymer network,
capable of absorbing large amounts of water and widely
used in controlled release system [30]. Recently, pH sen-
sitive hydrogels [31] have potential use in site specific
delivery of drug. Some of the most appealing character-
istics of chitosan are its bio adhesive properties and its
ability to promote cell proliferation and consequently,
tissue regeneration [27,28]. These properties of chitosan
are enhanced upon decreasing the polymer’s degree of
acetylation [32,33] and are of outmost importance for
biomedical engineering.
Beads are solid, spherical, micron or nano sized drug
carrier particles constituting a matrix type of structure.
Drug may be either absorbed at the spherical beads or
entrapped with in it. In other words, these are just like
vesicular system surround a cavity consisting drug per-
sists in polymeric solid. These polymeric beads are ad-
vantageous over pellets including relatively higher inter-
cellular uptake. Their charge properties influence the
uptake by intestinal epithelia. The beads obtained from
hydrophobic polymers have found to be higher uptake as
compared to the beads prepared from more hydrophilic
surfaces [34]. So nano / micro beads surface charges and
increased hydrophobicity of polymeric matrix have been
found to be effective for the gastrointestinal uptake in a
positive sense.
Our 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 to
investigate the swelling behavior and modeling drug re-
lease properties. No literature about such crosslinked
beads constituting chitosan with two amino acids are yet
found although there are some reports in the literature in
which tripeptide [35,36] have been used as spacer arm
group to obtain drug carrier beads. The synthesis of
polypeptide to be used as spacer arm in the polymer is a
complicated process. Therefore, we decided to use an
alternative to this approach. We planned a study to obtain
drug carrier beads of chitosan with constituent amino
acid of the polypeptide (to be used as a spacer arm)
which may be fruitful for further studies.
The present study includes the use of two amino acids
glycine and glutamic acid with cross linked chitosan
polymer. We had studied earlier [37] to find out differ-
ence in its characteristics, swelling behavior and drug
release with the cross linked chitosan beads and cross
linked chitosan amino acids beads containing only one
amino acid either glycine or glutamic acid.
2. Materials and Methods
Chitosan was purchased by India Sea Food, Kerala, and
was used as received. Its percentage of deacetylation
after drying was 89 %. Chlorpheniramine maleate (CPM)
i.e. 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.
2.1. Preparation of Semi-Interpenetrating
Polymer Network (IPN) Beads
Different IPN beads (G1-G8) 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 extruded 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 respec-
tively. The resultant beads were allowed to react with
glutaraldehyde solution as given in “Table-1” at 50˚C
for about 10 minutes. Finally the cross linked IPN beads
were successively washed with hot and cold water fol-
lowed by air drying.
Table 1. Composition of IPN beads.
Bead typeChitosan
(g)
Glycine
(g)
Glutamic
acid (g)
2%
acetic acid
(ml)
Glutaralde-
hyde
(%)
G1
G2
G3
G4
G5
G6
G7
G8
1.0
1.0
1.0
1.0
0.8
1.2
1.0
1.0
0.5
0.5
0.5
0.5
0.5
0.5
0.4
0.6
0.5
0.5
0.5
0.5
0.5
0.5
0.6
0.4
40
40
40
40
40
40
40
40
3.13
6.25
12.5
25.0
12.5
12.5
12.5
12.5

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 73
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.
2.2. Swelling Studies
Swelling behavior of chitosan beads (G1-G8) were stud-
ied in different pH (2.0 and 7.4) solutions. The percent-
age 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.
2.3. Drug Loading Assay
Accurately weighed (0.1g) drug loaded sample was kept
in 100 ml of 2% acetic acid for 48 hour. After centrifuga-
tion the CPM in the supernatant was assayed by spectro-
photometer at 193.5 nm.
2.4. 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 ali-
quots were withdrawn, filtered and assessed by recording
the absorbance at 193.5 nm. The cumulative CPM re-
lease was measured as a function of time.
2.5. Kinetic Analysis of Drug Release
A fair amount of work has been included in literature on
kinetics of drug release [38,39]. A large number of modi-
fied release dosage forms contain some sort of matrix
system and the drug dissolves from this matrix. The dif-
fusion pattern of the drug is dictated by water penetration
rate (diffusion controlled) and thus the Higuchi’s equa-
tion [40] 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.
2.6. Fourier Transform Infrared Spectra of IPN
Beads
FTIR spectra of IPN beads were recorded using a thermo
Nicolet Avatar 370 FT-IR spectrometer system using
KBr pellets.
2.7. 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 characterization of full and cross sec-
tioned IPN beads, magnification were applied to each
sample in order to estimate the morphology and interior
of the bead.
2.8. X-Ray Diffraction (XRD)
X-ray diffraction studies were performed by using
Bruker AXS D8 Advance using CuKα Nickel filter and
Copper as target at wavelength of 1.54 Å with goniome-
ter speed 2°/min.
2.9. Thermal Analysis
Thermal gravimetric analysis (TGA), Differential ther-
mal gravimetric (DTG) and Derivative thermal analysis
(DTA) were carried out simultaneously by using a Perkin
Elmer (PYRIS Diamond) 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 10°C/min under 200 ml/min flow rate of air or ni-
trogen atmosphere. Indium and gallium were used as
standards for temperature calibration.
3. Results and Discussion
3.1. Swelling Studies
The effect of pH, concentration of glutaraldehyde
crosslinker, chitosan and aminoacid on swelling behav-
iour of chitosan-glutamic-glycine beads has been evalu-
ated.
a) Effect of pH
Swelling studies to evaluate the effect of pH were car-
ried out in solution of pH 2.0 and pH 7.4. It was observed
that percentage of swelling is higher in acidic solution
(pH 2.0) than in alkaline solution (pH 7.4). We have also
performed a comparative study for pure chitosan, chito-
san-glycine, chitosan-glutamic acid and chito-
san-glycine-glutamic acid systems [37] and observed that
percentage of swelling for chitosan-glycine beads in

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 74
acidic solution was found to be higher than in basic solu-
tion which is due to inherent hydrophobicity of the chi-
tosan 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 acidic
solution which may be due to the presence of free car-
boxylic ends of the chitosan-glutamic acid IPN, 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
but at pH 7.4, their rate of swelling were intermediate
between chitosan-glutamic acid and chitosan-glycine
beads. Thus it was concluded that over all rate of swell-
ing was affected by glycine when chitosan-glycine-
glutamic acid beads were subjected to swelling studies.
b) Effect of glutaraldehyde
Swelling behaviour of crosslinked beads as a function
of time in pH 2.0 and pH 7.4 solutions having different
concentrations of glutaraldehyde are shown in “Fig-
ure-1(a)”.
It was observed that the swelling rate of the crosslinked
beads containing varying concentration of glutaraldehyde
follows the order G1>G2>G3>G4 i.e. swelling rates in-
creased with the decreased concentration of glutaralde-
hyde. When the cross linked beads are placed in the solu-
tion, the solution penetrates into the beads and the beads
subsequently 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 re-
laxation 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 dif-
fused into the bead to protonate the amino/imine groups
inside the beads and dissociating the hydrogen bonds
[41,42]. It has been observed that the swelling rates are
directly proportional to the degree of crosslinking. As the
higher crosslink density results in higher strength of the
beads and lower degree of swelling. Thus, the lowest
swelling rate is observed in case of G4 beads.
c) Effect of chitosan
Effect of varying weight ratio of chitosan on swelling
behaviour of crosslinked beads containing same quantity
of glutaraldehyde have been studied in acidic (pH 2.0)
and basic (pH 7.4) solutions and results are presented in
“Figure-1(b)”. The percentage of swelling of the
crosslinked beads having the same concentration of
crosslinker decreases with increasing concentration of
chitosan i.e. G5>G3>G6. It can be explained as the per-
centage of chitosan increased from G5 (44.4%) to G6
(a)
(b)
(c)
Figure 1. (a) Swelling behavior of crosslinked beads as a
function of time in solution pH 2.0 and pH 7.4 at 37˚C hav-
ing different percentage of glutaraldehyde; (b) Swelling
behavior of crosslinked beads as a function of time in solu-
tion pH 2.0 and pH 7.4 at 37˚C having different weight ratio
of chitosan; (c) Swelling behavior of crosslinked beads as a
function of time in solution pH 2.0 and pH 7.4 at 37˚C hav-
ing different weight ratio of amino acids.
(55.5%) through G3 (50%), the percentage of amino ac-
ids which act as a spacer decreased from G6 (55.5%) to
G5 (45.4%) through G3 (50%), the pore size of the beads
decreases and the penetration of pH solution into the
beads became difficult, which resulted in lesser degree of
swelling further, swelling percentage was higher in
acidic medium than in alkaline medium.
d) Effect of amino acids
The results obtained by changing in amino acids com-
position i.e. decrease in glutamic acid and increase in

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 75
glycine concentration of crosslinked beads having same
concentration of glutaraldehyde are given in “Fig-
ure-1(c)” have observed that the increase in concentra-
tion of glycine decreased the swelling percentage of
crosslinked beads in basic solution i.e. G8<G3<G7 while
increased in acidic solution (i.e. G7<G3<G8). It may be
due to the different behaviour of glycine and glutamic
acid as spacer arm in chitosan-amino acid beads towards
different pH [37].
3.2. Scanning Electron Microscopy Studies
SEM micrographs of dried beads (G1-G8) and their sur-
face morphology are shown in figure 2. It was concluded
from “Figure 2” that the beads were nearly spherical or
some what oval in shape this may be due to different
composition of crosslinked beads due to which solution
viscosity varied and beads varied in shape from spherical
to oval or elongated as we know that solution with de-
creased viscosity can be extruded easily as spherical bead
through a syringe. The approximate size of beads varied
from 0.08 to 0.15 mm. Cross linked chitosan amino acid
beads (G1-G8) had rough, rubbery, fibrous and folded
surfaces. With the highest concentration of cross linker,
in case of G4 the chains come closer to each other and
exhibit a regular, fibrous structure but with decreasing
concentration of glutaraldehyde as in case of G3, G2 and
G1 beads the structural morphology changes to layered
and big fibrous bunches. Rubbery morphology is ob-
served in case of lowest percentage of glutaraldehyde i.e
in G1 beads. Although having same degree of crosslinker
(i.e 12.5 % glutaraldehyde) G5 and G6 beads constituting
varied concentration of chitosan, while G7 and G8 beads
constituting Varied concentration of glycine and glu-
tamic acid also shown variation in surface morphology as
shown in “Figure 2”.
3.3. Fourier Transform Infrared Spectra Studies
“Figure 3(a)” shows the FTIR spectra of chitosan pow-
der, glutamic acid, glycine and G1-G8 drug unloaded
beads. FTIR spectra of chitosan powder curve has shown
two peaks around 894 cm-1 and 1171 cm-1 corresponding
to saccharide structure [43]. The observed peak at
1613cm-1 can be assigned as amino absorption peak. The
absorption peak for amide were observed at 1639 cm-1
and 1319 cm-1 and observed peak at 1384 cm-1 was as-
signed to CH3 symmetrical deformation mode [44,45]. 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 deacetylation
of chitosan. Peak observed at 2924 cm-1 is typical of C-H
stretching vibration. simultaneously the peak assigned for
amino absorption at 1613 cm-1 in original chitosan
broadened or disappered in cross linked beads and a new
Figure 2. Scanning Electron Microscopy (SEM) photo-
graphs of crosslinked beads (G1-G8) and their magnified
photographs showing surface morphology (G1*-G8*).
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 [46,47] in curve G1-G8. How-
ever, this was due to the overlapping of peaks corre-
sponding to –NH- stretching vibrations in -NH-COCH3 at
1639 cm-1 of the original chitosan with that of imino-
G1
G2
G3
G4
G5
G6
G7
G8
G1*
G2*
G3*
G4*
G5*
G6*
G7*
G8*

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 76
(a)
(b)
Figure 3. (a) FTIR spectra of glutamic acid (A), glycine (B),
chitosan powder (C) and drug unloaded crosslinked beads
(G1-G8); (b) FTIR spectra of pure chlorpheniramine
maleate (CPM) drug (D) and drug loaded crosslinked be ads
(G1-G8).
(-C=N-) stretching at 1567cm-1 of the newly formed
structure between amino group of chitosan and aldehyde
group of glutaraldehyde in G1-G8. A reaction taking
palace in the formation of crosslink is as follows
-----NH2 + O=HC ----- → ----N=CH-----
Amino aldehyde imino
(chitosan) (glutaraldehyde) (cross link)
On increasing the glutaraldehyde concentration, the
peak corresponding to 1567 cm-1 was sharpened and dis-
tinct in G4. All the curves G1 to G8 showed additional
peaks of amino acid.
FTIR spectral data of drug loaded beads in “Figure
3(b)” 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 crosslinked beads
(G1-G8) in “Figure 3(b)” were compared with drug
unloaded crosslinked beads (G1-G8) in “Figure 3(a)”.
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
band at around 864 cm-1 due to aromatic C-Cl stretching.
When drug was incorporated into the crosslinked chito-
san–amino acid beads, along with all the characteristic
band of the crosslinked chitosan and amino acids, addi-
tional 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.
3.4. X-Ray Diffraction Studies
X ray diffractograms of chitosan, glycine, glutamic acid
and drug unloaded beads (G1-G8) are presented in
“Figure 4(a)” and also of pure CPM drug and drug
loaded beads (G1-G8) are shown in “Figure 4(b)”. XRD
peaks depends on the crystal size. The diffraction pattern
of pure chitosan has the characteristic peaks at 2θ of 12
to 16, 20 and 29. All the drug unloaded beads (G1 to G8)
in “Figure 4(a)” show the similar peaks as that of chito-
san. CPM drug has shown characteristic intense peaks at
2θ of 12 to 35, however, these peaks are not observed in
CPM loaded beads (G1-G8) in “Figure 4(b)” but instead,
the diffractograms of both the drug loaded and drug
unloaded beads are almost identical, indicating the
amorphous dispersion of drug after entrapment into
polymeric chitosan-amino acid beads. No crystal of drug
were found in the drug loaded beads upto the detection
limit [48,49].
3.5. Thermal Analysis
Thermal gravimetric analysis (TGA) experiment were
carried out on chitosan, glutamic acid, glycine and cross
linked drug unloaded beads [G1-G8] and the curve ob-
tained are presented in “Figure 5(a)” which clearly
shows that approximately 10% weight loss by chitosan

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 77
(a)
(b)
Figure 4. (a) X-ray Diffraction (XRD) graphs of glutamic
acid (A), glycine (B), chitosan powder (C) and drug
unloaded crosslinked beads (G1-G8); (b) X-ray Diffraction
(XRD) graphs of pure chlorpheniramine maleate (CPM)
drug (D) and drug loaded crosslinked beads (G1-G8).
powder (curve A) below 100˚C due to loss of free water.
After this, weight loss remains constant up to 249˚C. A
sudden weight loss is observed after 249˚C and the total
weight loss at 400˚C is about 60%, while as the
crosslinking density increased from G1 to G4 the weight
loss percent decreased continuously upto 47% at 400˚C.
This shows that cross linking of chitosan with glutaral-
dehyde increases its thermal stability.
TG curves for CPM model drug (curve D) and drug
loaded crosslinked beads (G1-G8) are shown in “Figure
5(b)”. CPM drug lost about 67% weight between 208˚C
and 274˚C (curve D) which was due to the decomposi-
tion 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 G1-G8 containing drug.
This concluded that the drug is quite stable with in the
beads.
Differential thermal gravimetric (DTG) thermograms
of pure chitosan, glutamic acid, glycine and cross linked
beads G1-G8 are presented in “Figure 6(a)”. These in-
dicated the rate of weight loss for chitosan powder was
highest at 290˚C and cross linked chitosan beads showed
lesser rate of weight loss between 222 to 271˚C. On
comparing G1-G4 beads it can be seen that G4 beads
were found to be most stable as they lose weight at
minimum rate approximately 371μg/min at 255˚C as
compared to G1 beads (3.47 mg/min) at 245˚C, this con-
cluded that crosslinking made the beads more stable.
Variation of chitosan concentration (G5 to G6 beads) and
amino acid composition (G7 and G8 beads) give almost
equally stable as that of G3 beads.
DTG curves for CPM drug and drug loaded
crosslinked beads (G1-G8) are shown in “Figure 6(b)”.
Curve D for pure CPM drug have peaks for weight loss
at 134˚C, 207˚C and 256˚C. The comparison of drug
unloaded beads G1-G8 in “Figure 6(a)” and drug loaded
beads G1-G8 in “Figure 6(b)” showed almost similar
peaks with approximate same rate of weight lost also
proved equally drug stability in the polymeric matrix
Containing drug.
Derivative thermal analysis (DTA) thermograms for
pure chitosan, glutamic acid, glycine and cross linked
drug unloaded beads (G1-G8) are presented in “Figure
7(a)”. 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 transfor-
mation. Glutamic acid gives two and glycine gives one
endothermic peak in their thermo grams. While in case of
(G1-G8) beads only one exothermic peak is observed. It
was concluded that crosslinked chitosan-glycine-
glutamic acid G1-G8 beads are the equally stable.
DTA thermo grams for pure CPM drug and drug
loaded beads G1-G8 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 294˚C to

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 78
(a)
(b)
Figure 5. (a) Thermal gravimetric analysis (TGA) curves
for chitosan powder (A), glutamic acid (B), glycine (C) and
drug unloaded crosslinked beads (G1-G8); (b) Thermal
gravimetric analysis (TGA) curves for pure chlor-
pheniramine maleate (CPM) drug (D) and drug loaded
crosslinked beads (G1-G8).
(a)
(b)
Figure 6. (a) Differential thermal gravimetric (DTG) curves
for chitosan powder (A), glutamic acid (B), glycine (C) and
drug unloaded crosslinked beads (G1-G8); (b) Differential
thermal gravimetric DTG) curves for chlorpheniramine
maleate (CPM) Jdrug (D) and drug loaded crosslinked
beads (G1-G8).

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 79
(a)
(b)
Figure7. (a) Derivative thermal analysis (DTA) curves for
chitosan powder (A), glutamic acid (B), glycine (C) and
drug unloaded crosslinked beads (G1-G8); (b) Derivative
thermal analysis (DTA) curves for chlorpheniramine
maleate (CPM) drug (D) and drug loaded crosslinked be ads
(G1-G8).
chemical transformation. Drug loaded beads (G1-G8)
showed almost similar thermo grams in which no peaks
were observed at 134˚C and 294˚C indicating the amor-
phous dispersion of drug into the beads [50, 51].
3.6. Drug Release Studies
Drug loading assay studies shows that the beads loaded
with 150 mg and 200 mg of CPM respectively actually
released 78 µg and 142 µg of drug respectively on bio-
degradation of 0.1 g of beads in 100 ml of 2 percent ace-
tic acid after 48 hours. “Figure 8(a), 8(b) and 8(c)”
shows the release profile of CPM from chitosan beads
loaded (78 µg of drug) at various time intervals in acidic
(pH 2.0) and basic (pH 7.4) solutions 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 hour. 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 as the amount and per-
centage of drug released were much higher in acidic me-
dium than in alkaline medium in case of G1 to G8 beads.
This can be explained by the fact that the release of drug
due to diffusion through the swollen beads depends
mainly on the percentage of swelling of beads. Initially
the burst release of drug was observed due to the fast
penetration of the solvent into the crosslinked beads. Af-
ter few hours, a steady state was reached, due to the
equilibrium concentration gradient and then a constant
drug release was observed. At pH 7.4 there is less swell-
ing thus drug entrapped in the beads could not be re-
leased easily, however, at pH 2.0 the beads were swollen
to a higher percentage, leading to faster release of drug.
It was observed in “Figure 8(a)” that the drug release
rate increases with the decrease in crosslink density. This
may be due to the fact that the diffusion of drug from
IPN depends on the pore size of the polymer network
which will decrease with increase in degree of crosslink-
ing.
The release profile of CPM drug has been checked for
the beads having varying amount of chitosan for the
same amount of amino acids and glutaraldehyde (12.5%).
It was observed from “Figure 8(b)” that the G5 beads
having smaller weight of chitosan gave higher release
rates and slowest release rate was observed in case of G6
beads containing higher concentration of chitosan. This
may be due to containing more chitosan, the amount of
available amino acids acting as spacer group became low
and there was possibility of formation smaller mesh size
volume, which in turn might decrease the rate of swelling
as well as drug release.

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 80
(a)
(b)
(c)
Figure 8. (a) Release of chlorpheniramine maleate (CPM)
from 78 µg CPM loaded beads vs time in solution pH 2.0
and pH 7.4 at 370C having different percentage of glutaral-
dehyde; (b) Release of chlorpheniramine maleate (CPM)
from 78 µg CPM loaded beads vs time in solution pH 2.0
and pH 7.4 at 370C having different weight ratio of chitosan;
(c) Release of chlorpheniramine maleate (CPM) from 78 µg
CPM loaded beads vs time in solution pH 2.0 and pH 7.4 at
370C having different weight ratio of amino acid.
The drug release rates of CPM drug have also been
studies for the beads having different composition of
amino acids (i.e. glycine and glutamic acid) and results
shown in “Figure 8(c)”. It was observed that on increas-
ing the amount of glycine or decreasing the amount of
glutamic acid in G8 bead increased the rate of drug re-
lease in acidic solution while decreased in basic solution.
These results are quite similar to the results observed for
swelling rate. 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 glu-
tamic acid. Since carboxylic group is more susceptible to
be 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 glutamic acid in beads.
In case when glycine and glutamic acid both amino acid
are used for as spacer arm group within the chitosan
beads, the amount and percentage of drug release were
higher in acidic medium than in basic medium. This con-
cluded that glycine showed dominant effect over glu-
tamic acid and over all effect was governed by glycine.
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 “Figure 9(a), 9(b) and 9(c)”. 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 in-
creased 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 de-
pends on the percentage of swelling of beads.
3.7. 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
the kinetic data of drug release. Linear plots of percent
cumulative amount release versus square root of time for
IPN beads constituting 78 µg CPM drug are shown in
“Figure 10(a), 10(b) and 10(c)”and similar linear plots
are also shown in “Figure 11(a), 11(b) and 11(c)” for
IPN beads constituting 142 µg CPM drug which demon-
strating that the release from the crosslinked polymeric
microsphere matrix is diffusion controlled and obeys the
Higuchi’s model [52]. The constant k, presented in “Ta-
ble-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 have been found to be lower in solution of pH
7.4 than in solution of pH 2.0. However, the values were
smaller which indicate mild interaction between the drug
//
24 48
//
24 48
//
24 48

Current Distortion Evaluation in Traction 4Q Constant Switching Frequency Converters 81
Table 2. Results of drug release mechanism by fitting data in Higuchi’s model for CPM loaded beads.
pH 2.0
CPM loaded beads with
pH 7.4
CPM loaded beads with
78 µg 142 µg 78 µg 142 µg
Beads
type
k S.D. R k S.D. R k S.D. R k S.D. R
G1 0.30 ± 0.017 0.99 0.205 ± 0.008 0.99 0.20± 0.019 0.99 0.13 ± 0.008 0.98
G2 0.31 ± 0.035 0.99 0.19 ± 0.009 0.99 0.16± 0.015 0.99 0.095 ± 0.005 0.99
G3 0.26 ± 0.030 0.99 0.20 ± 0.015 0.99 0.10± 0.009 0.99 0.083 ± 0.008 0.99
G4 0.22 ± 0.025 0.99 0.195 ± 0.015 0.99 0.08± 0.008 0.95 0.073 ± 0.009 0.99
G5 0.30 ± 0.026 0.99 0.19 ± 0.005 0.99 0.14± 0.014 0.99 0.097 ± 0.009 0.99
G6 0.22 ± 0.024 0.99 0.19 ± 0.015 0.99 0.085± 0.005 0.99 0.081 ± 0.009 0.99
G7 0.20 ± 0.022 0.99 0.175 ± 0.014 0.99 0.17± 0.016 0.99 0.12 ± 0.009 0.99
G8 0.28 ± 0.031 0.99 0.20 ± 0.011 0.99 0.06± 0.005 0.98 0.069 ± 0.008 0.98
(a)
(b)
(c)
Figure 9. (a) Release of chlorpheniramine maleate (CPM)
from 142 µg CPM loaded bead vs time in solution pH 2.0
and pH 7.4 at 370C having different percentage of glutaral-
dehyde; (b) Release of chlorpheniramine maleate (CPM)
from 142 µg CPM loaded bead vs time in solution pH 2.0
and pH 7.4 at 370C having different weight ratio of chitosan;
(c) Release of chlorpheniramine maleate (CPM) from 142
µg CPM loaded bead vs time in solution pH 2.0 and pH 7.4
at 370C having different weight ratio of amino acid.
and polymeric matrices [53,54].
4. Conclusion
The observations of the present study have shown that
(a)
(b)
//
24 48
//
24 48
//
24 48

Characterization and Biodegradation Studies for Interpenetrating Polymeric Network (IPN) of Chitosan-Amino Acid Beads 82
(c)
Figure 10. (a) Plots showing drug release profile from 78 µg
chlorpheniramine maleate (CPM) loaded beads in solution
pH 2.0 and pH 7.4 by fitting the Higuchi’s equation having
different percentage of glutaraldehyde; (b) Plots showing
drug release profile from 78 µg chlorpheniramine maleate
(CPM) loaded beads in solution pH 2.0 and pH 7.4 by fitting
the Higuchi’s equation having different weight ratio of chi-
tosan; (c) Plots showing drug release profile from 78 µg
chlorpheniramine maleate (CPM) loaded beads in solution
pH 2.0 and pH 7.4 by fitting the Higuchi’s equation having
different weight ratio of amino acid
(a)
(b)
(c)
Figure 11. (a) Plots showing drug release profile from 142
µg chlorpheniramine maleate (CPM) loaded beads in solu-
tion pH 2.0 and pH 7.4 by fitting the Higuchi’s equation.
having different percentage of glutaraldehyde; (b) Plots
showing drug release profile from 142 µg chlorpheniramine
maleate (CPM) loaded beads in solution pH 2.0 and pH 7.4
by fitting the Higuchi’s equation having different weight
ratio of chitosan; (c) Plots showing drug release profile
from 142 µg chlorpheniramine maleate (CPM) loaded beads
in solution pH 2.0 and pH 7.4 by fitting the Higuchi’s equa-
tion having different weight ratio of amino acid.
chitosan-glycine-glutamic acid beads posses a pH de-
pendent 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 ex-
tended periods which make them appropriate for delivery
of drug at a controlled rate.
5. Acknowledgement
Authors are thankful to Prof. B. Gupta, Bioengineering
Laboratory, Textile Department, IIT, Delhi for gifting
chitosan sample.
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