Modified starch (cationized)-alginate beads containing aceclofenac: Formulation optimization using central composite design

RESEARCH ARTICLE

Modified starch (cationized)–alginate beads containingaceclofenac: Formulation optimization using centralcomposite design

Jadupati Malakar1, Amit Kumar Nayak2 and Arindam Das1

1 Department of Pharmaceutics, Bengal College of Pharmaceutical Sciences and Research, Durgapur, West Bengal, India2 Department of Pharmaceutics, Seemanta Institute of Pharmaceutical Sciences, Mayurbhanj, Odisha, India

Sustained aceclofenac release cationized starch–alginate beads were developed through ionotropic

gelation. The effects of sodium alginate and cationized starch amounts as independent process

variables on drug encapsulation, and drug release were optimized using central composite design.

The optimized beads showed drug encapsulation efficiency of 88.26 � 3.78% and cumulative drug

release of 26.28 � 1.21% after 6 h of dissolution. The average size of all these beads ranged from

1.08 � 0.08 to 1.48 � 0.18 mm. The developed beads were characterized by scanning electron

microscope, Fourier transform-infrared spectroscopy, and powder X-ray diffraction. The in vitro

dissolution of these beads showed prolonged sustained release of aceclofenac over 6 h, which

followed first-order model with anomalous (non-Fickian) diffusion mechanism. The swelling and

degradation of the optimized beads were influenced by pH of test mediums. These newly developed

beads were found suitable for sustained delivery of aceclofenac for prolonged period.

Received: November 6, 2012

Revised: January 23, 2013

Accepted: January 30, 2013

Keywords:

Aceclofenac / Cationized starch / Central composite design / Sodium alginate / Sustained release

1 Introduction

Starch is known as a cost-effective biodegradable polymer with

excellent biocompatibility [1]. Starch is able to produce quite

stable products in biological environment. However, native

starch alone is almost completely broken down after its oral

ingestion [2]. To improve the properties of starch as sustained

drug release matrices, modifications of functional groups of

starch and/or compounding with other polymers as blends have

been proposed [3–8]. In the literature, various native starches

and modified starches were blended with different polymers to

develop sustained drug delivery formulations [9–16].

Cationized starches are important industrial derivatives of

starches, in which starches are given a positive ionic charge by

introducing ammonium, amino, imino, sulfonium, or phos-

phonium groups [17, 18]. Cationized starches are mainly used

in the field of waste water treatment as flocculants, in the

manufacturing of textiles as additives and adhesives [19, 20].

The wide spread utilization of cationized starches in various

industries is based on their relatively low-price, non-toxicity, and

biodegradability [20]. Recently, cationized starch is one of the

modified starch materials, which was investigated as excipients

for the development of sustained release drug delivery systems

[2]. To the best of our knowledge, quaternary ammonium

introduced cationized starch (Scheme 1) has not been pre-

viously investigated as polymeric-blend with alginate for the

development of sustained release drug delivery systems.

Sodium alginate, an anionic copolymer of mannuronic and

guluronic acid residues, has been widely used in biomedical

applications due to its biodegradability and biocompatibility

[21]. It undergoes ionotropic gelation in the presence of metal

cations like Ca2þ, Ba2þ, Al3þ, etc. due to ionic interaction

between these cations and carboxylic acid groups of alginate

[21, 22]. However, ionotropically-gelled alginate based beads

suffer from some major limitations like drug loss during bead

preparation due to leaching of drugs through the pores [23].

Colour online: See the article online to view Figs. 1–5, 9, and 10 incolour.

Correspondence: Dr. Amit Kumar Nayak, Seemanta Institute ofPharmaceutical Sciences, Mayurbhanj 757086, Odisha, IndiaE-mail: [email protected]: þ91-06791-222238

Abbreviations: DEE, drug encapsulation efficiency; FTIR,Fourier transform-infrared; LOQ, limit of quantification;P-XRD, powder X-ray diffraction

DOI 10.1002/star.201200231Starch/Starke 2013, 65, 603–612 603

� 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.starch-journal.com

Therefore, many modifications of alginate beads based on the

use of another polymer as blend with alginate were investigated

for the use in drug delivery applications [21–27]. In the current

study, the combination of cationized starch and sodiumalginate

was used as polymer-blend to develop a polymeric matrix for

sustained drug release applications. Aceclofenac was used as

model drug in the present study to evaluate the sustained drug

release potential of the cationized starch–alginate beads pre-

pared using ionotropic gelation.

Aceclofenac is a non-steroidal anti-inflammatory drug

(NSAID) with short half-life (4 h) indicated for the sympto-

matic treatment of pain and inflammation [27, 28]. It is also

used in the treatment of arthritis, osteoarthritis, and rheuma-

toid arthritis [27]. Due to its short half-life, its recommended

dose is considered as 200 mg daily in divided doses. To

reduce dosing frequency and adverse effects during prolong

treatment, sustained release dosage of aceclofenac, which will

be able to deliver aceclofenac at a slow release rate over an

extended period of time is essential.

Central composite design is widely used for formulation

and process optimization in the field of drug delivery develop-

ment [21, 22]. It is a response surface design, which provides

information about effects of individual factors and pair wise

interactions of various individual effects. In the current inves-

tigation, the circumscribed central composite design as a

suitable statistical tool for the formulation optimization of

cationized starch–alginate beads containing aceclofenac was

employed. In addition to identifying an optimal combination

of cationized starch–alginate blend for the development of

modified starch (cationized)–alginate beads containing ace-

clofenac with high drug encapsulation and sustained drug

release was analyzed by the central composite design.

2 Materials and methods

2.1 Materials

Aceclofenac (B. S. Trader Pvt. Ltd., India), sodium alginate

(Central Drug House, India), modified starch (cationized,

amylose–amylopectin ratio ¼ 27:73; Shuvam Starch Chem

Pvt. Ltd., India), and calcium chloride (Mark Specialties

Pvt. Ltd, India) were used. All other chemicals used were

of analytical grade.

2.2 Methods

2.2.1 Preparation of cationized starch–alginate beads

containing aceclofenac

Briefly, required amount of cationized starch was dissolved in

deionized water (10 mL) using magnetic stirring for 30 min

at 508C. Then, required amount of sodium alginate was added

into the previously prepared starch solution with continuous

magnetic stirring for 30 min. Afterwards, aceclofenac was

added to the mixture gel of sodium alginate and starch for

each formulation maintaining polymer to drug ration 2:1,

and mixed thoroughly using a homogenizer (Remi Motors,

India). The final starch–sodium alginate mixture gels

containing aceclofenac were ultrasonicated for 5 min for

debubbling. The resulting dispersion was then added via a

21-gauge needle drop wise into 100 mL of 10% w/v CaCl2solution. Added droplets were retained in the CaCl2solution for 15 min to complete the curing reaction. The

wet beads were collected by decantation. These wet beads

were washed two times with distilled water and dried at 378Cfor overnight. The dried beads were stored in a desiccator

until used.

2.2.2 Experimental design

A central composite design (spherical type, single center point

and a ¼ 1.414) was employed for the formulation optimiz-

ation of cationized starch–alginate beads containing aceclo-

fenac. The amount of sodium alginate (X1) and cationized

starch (X2) as polymeric blend were defined as the selected

independent formulation variables (factors); while drug

encapsulation efficiency (DEE, %), and drug release at 6 h

(R6 h, %) were analyzed as dependent variables (responses).

The process variables (factors) and levels with experimental

values are reported in Table 1. In Table 2, the matrix of the

design including investigated factors and responses are also

shown. Design-Expert 8.0.6.1 software (Stat-Ease Inc., USA)

was used for generation and evaluation of experimental

design. The polynomial mathematical model generated

by circumscribed central composite design is the following

[21, 22]:

Y ¼ b0 þ b1X1 þ b2X2 þ b3X1X2 þ b4X12 þ b5X

22 (1)

where, Y is the response; b0 is the intercept, and b1, b2, b3, b4,b5 are regression coefficients. X1 and X2 are individual effects;

X 21 and X2

2 are quadratic effects; X1 X2 is the interaction effect.

One-way ANOVA was applied to estimate the significance of

the model (p < 0.05).

Scheme 1. Molecular structure of quaternary ammoniumintroduced cationized starch.

604 J. Malakar et al. Starch/Starke 2013, 65, 603–612


2.2.3 Determination of viscosity of polymer-blend

The viscosities of various polymer-blends as 10 mL aqueous

solutions were determined by using a Brookfield DV III

ultra V 6.0 RV cone and plate rheometer (Brookfield engin-

eering laboratories, Middleboro, MA) using spindle rpm 1 at

258C. The software used for calculation was Rheocalc V2.

2.2.4 Determination of drug content

An UV–VIS Spectrophotometer (Thermo Spectronic UV-1,

USA) with matched quartz cell corresponding to 1 cm path

length and spectral bandwidth 1 nm was employed for

determination aceclofenac. Aceclofenac stock solutions of

100 mg/mL were prepared for both the drugs, prepared on

the day of analysis by suitable dilution of the stock solution

with distilled water. The stock solution of aceclofenac further

diluted with distilled water to get a series of drug solutions,

i.e. 2–10 mg/mL. Then all samples were scanned separately in

the range of 200–350 nm to detect lmaxs for aceclofenac. The

lmax were found to be 273 nm for the aceclofenac. A linear

relationship between absorbances and concentration was

found in the calibration curve (Y ¼ 0.318 X þ 0.0011,

R2 ¼ 0.9992).

LOD and limit of quantification (LOQ) were estimated and

calculated for validation by taking the SD of the y-interceptand slope of the calibration curve. The formula for determi-

nation of LOD and LOQ are given below:

LOD ¼ 3a

S(2)

LOQ ¼ 10a

S(3)

where a is referred as SD of y-intercept and S is referred as

slope of the standard curve.

The values of LOD and LOQ were determined 0.0189 and

0.0628, which confers the sensitivity of the method.

2.2.5 Determination of DEE (%)

Accurately weighed 100 mg of prepared beads from each

batch were taken separately and were crushed using pestle

and mortar. The crushed powders of these beads were placed

in 500 mL of phosphate buffer, pH 7.4, and kept for 24 h with

occasionally shaking at 37 � 0.58C. After the stipulated time,

the mixture was stirred at 500 rpm for 20 min using a mag-

netic stirrer. The polymer debris formed after disintegration

of beads was removed filtering through Whatman1 filter

paper (No. 40). The drug content in the filtrate was deter-

mined using a UV–VIS spectrophotometer (Thermo

Spectronic UV-1, USA) by measuring absorbance at lMax

of 273 nm. The DEE of beads was calculated using this

following formula:

DEE; % ¼ Actual drug content in beads

Theoretical drug content in beads� 100 (4)

2.2.6 Determination of bead size

Diameters of these formulated beads were measured using

digital slide calipers (CD-600 CS, Mitutoyo Corporation, Japan)

by inserting the beads in between the space of two metallic

plates and diameter of resultant beads were displayed in the

digital screen of the previously calibrated equipment. The

average size was then calculated bymeasuring the diameter of

three sets of 20 beads from each batch.

2.2.7 Surface morphology analysis

The surface morphology of the formulated beads was ana-

lyzed by scanning electron microscope (SEM) (JEOL, JSM-

5800, Japan). Beads were gold coated and mounted on a brass

stub using double-sided adhesive tape and under vacuum in

an ion sputter with a thin layer of gold (3–5 nm) for 75 s and

at 20 kV to make them electrically conductive and their

morphology was examined.

Table 1. Factors and levels of the circumscribed centralcomposite design

Normalized

levels

Experimental settings

Sodium

alginate (mg) (X1)

Cationized

starch (mg) (X2)

�1.414 179.29 79.29

�1 200.00 100.00

0 250.00 150.00

1 300.00 200.00

1.414 320.71 220.71

Table 2. Experimental plan and observed response values fromrandomized run in central composite design

Experimental

formulations

Factors Responsesa)

Sodium

alginate

(mg) (X1)

Cationized

starch

(mg) (X2) DEE (%)b) R6 h (%)c)

F-1 200.00 100.00 58.66 � 1.36 38.74 � 1.56

F-2 200.00 200.00 69.65 � 2.83 35.82 � 1.62

F-3 300.00 100.00 64.85 � 1.92 35.46 � 1.70

F-4 300.00 200.00 75.50 � 2.38 30.08 � 1.24

F-5 179.29 150.00 59.85 � 1.22 38.80 � 1.54

F-6 320.71 150.00 68.82 � 2.60 32.62 � 1.33

F-7 250.00 220.71 76.32 � 2.54 31.75 � 1.38

F-8 250.00 79.29 60.56 � 1.08 37.62 � 1.80

F-9 250.00 150.00 64.88 � 2.03 36.11 � 1.82

a) Observed response values: Mean � SD (n ¼ 3);b) DEE (%) ¼ Drug encapsulation efficiency (%);c) R6 h (%) ¼ drug release at 6 h.

Starch/Starke 2013, 65, 603–612 605


2.2.8 Fourier transform-infrared (FTIR) spectroscopy

Samples were reduced to powder and analyzed as KBr pellets

by using a FTIR spectroscope (Perkin–Elmer Spectrum RX I).

The pellet was placed in the sample holder. Spectral scanning

was taken in wavelength region between 3700, and 400/cm at

a resolution of 4/cm with 1 cm/s scan speed.

2.2.9 Powder X-ray diffraction (P-XRD) analysis

Samples were exposed to Cu Ka radiation (40 kV � 20 mA) in

a wide-angle X-ray diffractometer (Siemens D5000, Munich,

Germany). The instrument was operated in the step-scanmode

in increments of 0.0508 2u. The angular range was 00 to 500 2u,and counts were accumulated for 1 s at each step.

2.2.10 In vitro drug release studies

The release of the aceclofenac from various beads containing

aceclofenac was tested using a dissolution apparatus USP/BP/

IP (Campbell Electronics, India). The baskets were covered

with 100-mesh nylon cloth to prevent the escape of the beads.

The dissolution rates were measured at 37 � 18C under

50 rpm speed. Accurately weighed quantities of starch-blended

calcium alginate beads containing aceclofenac equivalent to

100 mg aceclofenac were added to 900 mL of simulated

gastric fluid (pH 1.2). The test was carried out in

simulated gastric fluid (pH 1.2) for 2 h, and then, continued

in simulated intestinal fluid (pH 7.4) for next 4 h. Five milli-

liters of aliquots were collected at regular time intervals,

and the same amounts of fresh dissolution medium were

replaced into dissolution vessel to maintain the sink condition

throughout the in vitro drug release experiment. The collected

aliquots were filtered, and suitably diluted to determine the

absorbance using a UV–VIS spectrophotometer (Thermo

Spectronic UV-1, USA) by measuring absorbance at lMax of

273 nm.

2.2.11 Analysis of in vitro drug release kinetics and

mechanism

The in vitro drug release data were evaluated kinetically in

different mathematical models [21, 25]:

Zero-ordermodel: Q ¼ ktþQ0 (5)

where Q represents the drug released amount in time t, andQ0 is the start value of Q; k is the rate constant.

First-ordermodel: Q ¼ Q0ekt (6)

where Q represents the drug released amount in time t, andQ0 is the start value of Q; k is the rate constant.

Higuchimodel: Q ¼ kt0:5 (7)

whereQ represents the drug released amount in time t, and kis the rate constant.

Korsmeyer-Peppas model: Q ¼ ktn (8)

where Q represents the drug released amount in time t, k is

the rate constant and n is the diffusional exponent, indicative

of drug release mechanism.

The Korsmeyer-Peppas model was employed in in vitro

drug release behavior analysis of beads to distinguish com-

peting mechanisms: Fickian (diffusion-controlled) release,

non-Fickian (anomalous) release, and case-II transport (re-

laxation-controlled release) [29]. When n is�0.43, it is Fickianrelease. The n-value between 0.43 and 0.85 is defined as non-

Fickian release. When n � 0.85, it is case-II transport [29].

2.2.12 Swelling behavior measurement

Swelling measurement of optimized beads containing ace-

clofenac were carried out in two different aqueous media:

simulated gastric fluid (pH 1.2), and simulated intestinal fluid

(pH 7.4). Beads (100 mg) were placed in vessels of dissolution

apparatus (Campbell Electronics, India) containing 500 mL

respective media. The experiment was carried out at

37 � 18C under 50 rpm paddle speed. The swelled beads

were removed at predetermined time interval and weighed

after drying the surface by using tissue paper. Swelling index

was determined using the following formula:

Swelling index

¼ Weight of beads after swelling�Dryweight of beads

Dryweight of beads� 100

(9)

2.2.13 Statistical analysis

Statistical optimization was performed using Design-Expert

8.0.6.1 software (Stat-Ease Inc., USA). All measured data are

expressed as mean � SD.

3 Results and discussion

3.1 Optimization

In the central composite design (spherical type, single center

point, and a ¼ 1.414), total nine experimental formulations

of cationized starch–alginate beads containing aceclofenac

were proposed by Design-Expert 8.0.6.1 software for two

independent process variables (factors): amount of sodium

alginate (X1) and amount of cationized starch (X2) (Table 1).

The effects of these independent variables on DEE, and R6 h

were investigated as optimization response parameters in the

current investigation. Overview of the experimental plan and

observed response values is presented in Table 2. The Design-



Expert 8.0.6.1 software provided suitable polynomial model

equations involving individual main factors and interaction

factors for each investigated responses after fitting these data.

These models were evaluated statistically by applying one-way

ANOVA (p < 0.05), which is shown in Table 3.

The model equation relating DEE as response became:

DEE ð%Þ ¼ 47:49þ 0:08X1 � 0:12X2 þ 7:90

� 10�4X 22 ½R2

¼ 0:9961; F-value ¼ 154:25; p < 0:05�: (10)

It can be noted that the coefficients, b3 and b4 of the model

equation relating DEE had no statistical significance

(p > 0.05), since the statistic p-value of b3 and b4 were

0.8139 and 0.8533, respectively.

The model equation relating R6h as response became:

R6 h ð%Þ ¼ 31:33þ 0:04X1 þ 0:11X2 � 2:46� 10�4X1X2

� 3:02� 10�4X22 ½R2 ¼ 0:9991; Fvalue

¼ 669:27; p < 0:05�: ð11ÞIt can be noted that the coefficient, b4 of the model

equation relating R6 h had no statistical significance

(p > 0.05), since the statistic p-value of b4 were 0.0721,

respectively.

The three-dimensional response surface graph is very

useful in learning about the main and interaction effects of

the independent variables (factors), whereas two-dimensional

contour graph gives a visual representation of values of the

response [25, 29]. The three-dimensional response surface

graphs relating DEE (%) and R6 h (%) generated by the

Design-Expert 8.0.6.1 software are presented in Figs and 2,

respectively. The two-dimensional contour graphs relating

DEE and R6 h are presented in Figs and 4, respectively.

The three-dimensional response surface plot relating DEE

(Fig. 1) depicted the increase in DEE with the increasing of

both the sodium alginate amount (X1), and cationized starch

amount (X2). On the other hand, the three dimensional

response surface plots relating R6 h (Fig. 2) also indicated

the decrease in R6 h with the increasing of both the sodium

alginate amount (X1), and starch amount (X2) in the formu-

lated cationized starch–alginate beads containing aceclofenac.

All these contour plots relating measured responses

(Figs and 4) were found to be nonlinear, indicating nonlinear

relationships between two independable variables (here,

sodium alginate amount, X1 and cationized starch amount,

X2) on all measured responses (DEE and R6 h), investigated in

this study.

A constraint to maximize the DEE and minimize the R6 h

was to set the goal to locate the optimum settings of inde-

pendent variables for the optimized formula by the central

composite design based on the criterion of desirability. To get

the desired optimum responses, independable variables (fac-

tors) were restricted to 200.00 mg � X1 � 500.00 mg, and

50.00 mg � X2 � 400.00 mg; whereas the desirable ranges

of responses were restricted to 85% � DEE � 100%, and

25% � R6 h � 30%. The overlay plot indicating the region

of optimal process variable settings was presented in Fig. 5. In

order to validate and check the optimization capability of

thesemodels generated, optimized cationized starch–alginate

beads containing aceclofenac was prepared using one of the

optimal process variable settings proposed by the design. The

selected optimal process variable setting used for the formu-

lation of optimized cationized starch–alginate beads contain-

ing aceclofenac was X1 ¼ 270.00 mg and X2 ¼ 270.00 mg.

Table 3. Summary of ANOVA for the response parameters

Source

Sum of

squares d. f.a)

Mean

square F square

p-Value

prob > F

(a) For DEE (%)b)

Model 337.70 5 67.54 154.25 0.0008 (S)

X1 76.42 1 76.42 174.53 0.0009 (S)

X2 241.21 1 241.21 550.88 0.0002 (S)

X1 X2 0.03 1 0.03 0.07 0.8139 (NS)

X 21 0.02 1 0.02 0.04 0.8533 (NS)

X 22 11.34 1 11.34 25.90 0.0147 (S)

(b) For R6 h (%)c)

Model 77.33 5 15.47 669.27 <0.0001 (S)

X1 39.43 1 39.43 1706.18 <0.0001 (S)

X2 34.45 1 34.45 1490.87 <0.0001 (S)

X1 X2 1.51 1 1.51 65.47 0.0039 (S)

X 21 0.17 1 0.17 7.44 0.0721 (NS)

X 22 1.66 1 1.66 71.88 0.0034 (S)

X1 and X2 represent the main effects (factors); X21 and X 2

2 are the

quadratic effect; X1 X2 is the interaction effect.a) d.f. ¼ degree of freedom.b) DEE (%) ¼ drug encapsulation efficiency (%).c) R6 h (%) ¼ drug release at 6 h.

Figure 1. Response surface graph showing the effect ofsodium alginate amount (mg) and cationized starch amount(mg) on DEE (%).

Starch/Starke 2013, 65, 603–612 607


Table 4 lists the results of experiments with predicted

responses by the mathematical models and those actually

observed. The optimized beads containing aceclofenac

(F-O) showed DEE of 88.26 � 3.78% and R6 h of

26.28 � 1.21%. The small error-values (2.55 and �4.04,respectively) indicate that mathematical models obtained

from the central composite design were well fitted.

3.2 Viscosity of polymer-blend

The viscosities various polymer-blends used for the prep-

aration of cationized starch–alginate beads containing aceclo-

fenac were measured and these results were presented in

Table 5. The viscosities of various polymer-blends used

ranged from 567.55 � 20.44 to 889.20 � 51.45 cps. The

result showed that the viscosity of these polymer-blends

was found increased with the increasing of cationized starch

amount.

3.3 DEE

The DEE of all these beads containing aceclofenac was within

the range between 58.66 � 1.36 and 88.26 � 3.78% (Tables 1

and 4). It was observed that DEE of these beads was increased

with the increment of both the sodium alginate and cation-

ized starch amount. The increased DEE with the increasing

amount of sodium alginate and cationized starch in these

beads may be due to the increase in viscosity of the polymer-

blend solutions with the increasing amount of polymer

addition. This might have prevented drug leaching from

the prepared beads to the cross-linking solution. In addition,

the increasing amount of sodium alginate in polymer-blend

Figure 2. Response surface graph showing the effect ofsodium alginate amount (mg) and cationized starch amount(mg) on R6 h (%).

Figure 3. Contour graph showing the effect of sodium alginateamount (mg) and cationized starch amount (mg) on DEE (%).

Figure 4. Contour graph showing the effect of sodium alginateamount (mg) and cationized starch amount (mg) on R6 h (%).

Figure 5. The overlay plot indicating the region of optimal pro-cess variable settings.



solution might have elevated the cross-linking by CaCl2through availing more numbers of anionic sites of alginates

for ionic cross-linking by calcium ions [30].

3.4 Bead size

The average size of these formulated dried beads containing

aceclofenac ranged from 1.08 � 0.08 to 1.48 � 0.18 mm

(Table 5). Increasing the bead size was found with the increas-

ing amount of the polymers, sodium alginate, and cationized

starch into bead formulations containing aceclofenac. This

might be attributed due to the increase in viscosity of the

polymer-blend (cationized starch and sodium alginate)

solutions with incorporation of both the polymers in increas-

ing ratio that in turn increased the droplet size during

addition of the polymer blend solution to the cross-linking

solution.

3.5 Surface morphology

The morphological analysis of the optimized beads contain-

ing aceclofenac (F-O) was visualized by SEM at different

magnifications and is presented in Fig. 6a and b. The SEM

photograph of these beads at lower magnification (60�)showed spherical shape with a rough surface (Fig. 6a).

Detailed examination of the bead surface topography at

higher magnification (500�) revealed wrinkles and channels

on its surface (Fig. 6b).

3.6 FTIR spectroscopy

The FTIR spectra of sodium alginate, cationized starch, blank

beads, optimized beads containing aceclofenac and pure ace-

clofenac are shown in Fig. 7a–e. In the FTIR spectra of sodium

alginate, cationized starch, and blank beads (Fig. 7a–c), the

characteristic peaks of the natural polysaccharides were

observed within the range, 3600–3200/cm as strong and broad

absorption band peaks due to –OH stretching along with some

complex bands in the region of 1200–1050/cm due to –C–O

and –C–O–C– stretching vibrations. In addition, the absorption

bands in the region 930–820/cm and 785–730/cm were also

observed due to vibrational modes of pyranose rings of poly-

saccharides. In the FTIR spectra of sodium alginate and blank

beads (Fig. 7a and c), presence of strong asymmetric stretching

absorption band near 1630/cm and weaker symmetric stretch-

ing band near 1400/cm were supporting the presence of

carboxylate anion of alginate structure. In the FTIR spectrum

of cationized starch (Fig. 7b), a characteristic band at 1491.80/

cm was observed due to –C–N bond for cationic quaternary

ammonium groups. In the spectrum of blank beads (Fig. 7c),

the strong asymmetric stretching absorption band of alginate

was found to shift towards lower wave number (�40/cm);

while the band assigned to the –C–N bond of cationized starch

also shifted towards lower wave number (�10/cm). These

displacements of bands could be due to interpolyelectrolyte

interaction between carboxylic groups of alginate chain and

quaternary ammonium groups of cationized starch. The FTIR

spectrum of aceclofenac (Fig. 7e) showed that principal peaks

at 3027.73 and 2936.75/cm (due to aromatic and aliphatic –C–

H stretching vibrations, respectively), a band at 1717/cm (due

to C––O stretching), a sharp band at 1771.97/cm (due to C––O

stretching of carboxylic acid), band at 3319.64/cm (due to

Table 4. Results of experiments for confirming optimization capability

Code

Factors Responsesa)

Sodium

alginate (mg)

Cationic

starch (mg)

DEE (%)b) R6 h (%)c)

Predicted

value

Observed

value Error (%)d)

Predicted

value

Observed

value Error (%)d)

F-O 270.00 270.00 90.57 88.26 � 3.78 2.55 25.26 26.28 � 1.21 �4.04

a) Observed response values: Mean � SD (n ¼ 3).b) DEE (%) ¼ Drug encapsulation efficiency(%).c) R6 h (%) ¼ drug release at 6 h.d) Error (%) ¼ [Difference between predicted value and observed value/predicted value] �100.

Table 5. Viscosity of polymer-blend solution and meandiameters of various formulated cationized starch–alginate beads containing aceclofenac

Formulation

codes Viscositya) (cps)

Mean

diameter (mm)b)

F-1 662.82 � 23.28 1.12 � 0.09

F-2 698.44 � 27.03 1.25 � 0.10

F-3 707.65 � 38.53 1.38 � 0.14

F-4 796.67 � 43.60 1.48 � 0.18

F-5 567.55 � 20.44 1.08 � 0.08

F-6 712.20 � 38.08 1.47 � 0.20

F-7 822.78 � 52.17 1.26 � 0.11

F-8 624.20 � 18.72 1.15 � 0.08

F-9 680.46 � 30.03 1.21 � 0.08

F-O 889.20 � 51.45 1.46 � 0.19

a) Mean � SD; n ¼ 3.b) Mean � SD; n ¼ 20.

Starch/Starke 2013, 65, 603–612 609


secondary N–H rocking vibrations), and two sharp peaks at

716.11/cm (due to 1, 2 di-substituted C–Cl stretching) [27]. In

the FTIR spectrum of optimized beads containing aceclofenac

(Fig. 7d), various characteristic peaks of blank beads and

aceclofenac appeared clearly. The FTIR analysis confirmed

the compatibility of the aceclofenac with the cationized

starch–alginate matrix.

3.7 P-XRD analysis

P-XRD patterns of pure aceclofenac and optimized cationized

starch–alginate beads containing aceclofenac (F-O) are shown

in Fig. 8. P-XRD of pure aceclofenac (a) showed significant

peak characteristic peaks at 18.58, 19.18, 22.68, 24.28, 25.98(2u). These significant characteristic peaks of aceclofenac also

appeared in the P-XRD pattern of the optimized beads con-

taining aceclofenac. However, the intensity of these peaks

referred to the crystalline nature of pure aceclofenac

decreased significantly in the optimized beads containing

aceclofenac, which could be due to the effect of polymer or

formulation process.

3.8 In vitro drug release

The in vitro drug release studies were carried out for various

cationized starch–calcium alginate beads containing aceclo-

fenac in the 0.1 N HCl (pH, 1.2) for first 2 h and then, in

phosphate buffer (pH, 7.4) for next 4 h. All these cationized

starch–alginate beads containing aceclofenac showed pro-

longed release of aceclofenac over 6 h (Fig. 9). Aceclofenac

release from these beads in the acidic medium was <16%

after 2 h for all these beads containing aceclofenac due to the

shrinkage of alginate at acidic pH. The trace amount of drug

release could probably be due to the presence of drug crystals

onto bead surface. After that, drug release was observed faster

in phosphate buffer (pH, 7.4) comparatively, due to the higher

swelling rate of these beads in phosphate buffer. The per-

centage drug released from cationized starch–alginate beads

containing aceclofenac in 6 h (R6 h) was within the range of

26.28 � 1.21 to 38.80 � 1.54%, and was found to be lower

with the increasing of both sodium alginate and cationized

starch amount. In case of beads, containing higher polymer

contents, themore hydrophilic property of the polymers could

probably binds better with water to form viscous gel structure.

This might blockade the pores on the surface of beads and

could sustain the drug release from these formulated beads.

Figure 6. Scanning electron microphoto-graph of optimized cationized starch–algi-nate beads containing aceclofenac (F-O):60� (a), and 500� (b).

Figure 7. The FTIR spectra of sodium alginate (a), cationizedstarch (b), blank cationized starch–calcium alginate beads (c),cationized starch–calcium alginate beads containing aceclofenac(F-O) (d), and pure aceclofenac (e).

Figure 8. P-XRD pattern of pure aceclofenac (a), and optimizedcationized starch–calcium alginate beads containing aceclofenac(F-O) (b).



The in vitro drug release data from various cationized starch–

alginate beads containing aceclofenac were evaluated kineti-

cally using various mathematical models like zero order, first

order, Higuchi, and Korsmeyer-Peppas model. The results of

the curve fitting into these above-mentioned mathematical

models are given in Table 6. When respective correlation

coefficients of these beads were compared, the aceclofenac

release from these beads was found to follow First-order

model (R2 ¼ 0.9950 to 0.9989) over a period of 6 h. The value

of release exponent (n) determined from in vitro drug release

data of various cationized starch–alginate beads containing

aceclofenac ranged from 0.64 to 0.80, indicating anomalous

(non-Fickian) diffusion mechanism for drug release [30]. The

anomalous diffusion mechanism of drug release demon-

strates both diffusion controlled, and swelling controlled drug

release from cationized starch–alginate beads containing

aceclofenac.

3.9 Swelling behavior

The swelling behavior of optimized cationized starch–

alginate beads containing aceclofenac was evaluated in

0.1 N HCl, pH 1.2, and phosphate buffer, pH 7.4. The swel-

ling behaviors of these beads in both pH, 0.1 N HCl (pH 1.2),

and phosphate buffer (pH 7.4) are shown in Fig. 10. The

swelling index of optimized beads containing aceclofenac was

lower in 0.1 N HCl in comparison with that of the phosphate

buffer, initially. This occurred due to shrinkage of alginate at

acidic pH [17]. Maximum swelling was noticed at 1–2 h in

phosphate buffer, pH 7.4 and after which, erosion and dis-

solution of these beads took place. The swelling behavior of

optimized beads in alkaline pH could be explained by the ion

exchange phenomenon between the calcium ion of cross-

linked beads and the sodium ions present in phosphate buffer

due to influence of calcium-sequestrant phosphate ions [30].

This could result in disaggregation of cationized starch–algi-

nate matrix structure leading to matrix erosion and dissol-

ution of swollen beads.

4 Conclusions

Cationized starch–alginate beads for sustained release of ace-

clofenac were successfully developed by central composite

design through ionotropic gelation method. The effects of

sodium alginate and cationized starch amounts as independ-

ent process variables on the properties of these newly devel-

oped beads containing aceclofenac like drug encapsulation and

drug release were optimized and analyzed based on the

response surface methodology. These developed beads con-

taining aceclofenac were excellent combination of high drug

encapsulation and suitable sustained drug release pattern over

prolonged period. The in vitro drug release from these beads

followed first-order model with anomalous (non-Fickian) dif-

fusion mechanism. The swelling and degradation of the opti-

mized beads were influenced by pH of test mediums. These

properties of the newly developed beads could possibly be

Figure 9. In vitro drug release from various cationized starch–alginate beads containing aceclofenac [Mean � SD, n ¼ 3].

Table 6. Results of curve fitting of the in vitro aceclofenac releasedata from different cationized starch–alginate beadscontaining aceclofenac

Formulation

code

Correlation coefficient (R2)

Release

exponent (n)

Zero

order

First

order Higuchi

Korsmeyer-

Peppas

F-1 0.9893 0.9950 0.8479 0.9567 0.66

F-2 0.9765 0.9984 0.7897 0.9501 0.71

F-3 0.9614 0.9989 0.7990 0.9224 0.69

F-4 0.9655 0.9971 0.6958 0.9417 0.80

F-5 0.9864 0.9974 0.8553 0.9539 0.64

F-6 0.9692 0.9972 0.7412 0.9439 0.76

F-7 0.9622 0.9981 0.7434 0.9226 0.72

F-8 0.9831 0.9980 0.8186 0.9532 0.68

F-9 0.9783 0.9070 0.7611 0.9488 0.74

F-O 0.9508 0.9964 0.7462 0.9047 0.69

Figure 10. Swelling behavior of optimized cationized starch–alginate beads containing aceclofenac in 0.1 N HCl, pH 1.2 andphosphate buffer, pH 7.4 [Mean � SD, n ¼ 3].

Starch/Starke 2013, 65, 603–612 611


advantageous in terms of advanced patient compliance with

reduced dosing interval. This type of polymeric beads can also

be exploited for sustained release drug delivery of other drugs

and can be commercially processed easily.

The authors have declared no conflict of interest.

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Modified starch (cationized)-alginate beads containing aceclofenac: Formulation optimization using central composite design