CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 52, 2016 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Petar Sabev Varbanov, Peng-Yen Liew, Jun-Yow Yong, Jiří Jaromír Klemeš, Hon Loong Lam, 
Copyright © 2016, AIDIC Servizi S.r.l., 

ISBN 978-88-95608-42-6; ISSN 2283-9216 
 

Sericin and Alginate Blend as Matrix for Incorporation of 

Diclofenac Sodium 

Jacyara M. M. Vidarta, Mariana Nakashimaa,Thiago L. da Silvaa, Paulo C. P. 

Rosab, Marcelino L. Gimenesc, Melissa G. A. Vieiraa, Meuris G. C. da Silvaa* 

aSchool of Chemical Engineering, University of Campinas, UNICAMP, 13083-825, Campinas – SP, Brazil 

bSchool of Pharmaceutical Sciences, University of Campinas, UNICAMP, 13083-859, Campinas – SP, Brazil 
cDepartment of Chemical Engineering, State University of Maringá, UEM, 87020-900, Maringá – PR, Brazil 

meuris@feq.unicamp.br 

Diclofenac sodium (DS) is a non-steroidal anti-inflammatory widely used clinically and has recurring side 

effects in gastrointestinal system. In addition, it requires multiple daily doses to maintain its therapeutic drug-

blood level. Therefore, the modification of the form of presentation of the DS becomes desirable to improve 

patient compliance and decrease side effects. Sericin is a globular protein that offers many desirable 

characteristics for the incorporation of drugs. It is presented in the silkworm cocoons (Bombyx mori) and is 

usually discarded in the wastewater of degumming silk processing. Sodium alginate is a natural 

polysaccharide extracted from brown seaweed that has an abundant use in drug delivery systems. The blend 

of sericin and alginate may provide characteristics more suitable for improving the encapsulation. The aim of 

the current work is to evaluate the content of DS incorporated in sericin/alginate particles. The sericin solution 

was obtained by degumming process in autoclave (1 kgf/cm2, 40 min) and the sodium alginate used was of 

analytical grade (Sigma-Aldrich). Blends of sericin and alginate with DS incorporated were produced in various 

formulations. These blends were dripped in CaCl2 solution, in the ionic gelation technique, in order to produce 

the particles. The different formulations used were compared by evaluating the efficiency of incorporation of 

DS in the sericin/alginate particles. Additionally, the surface morphology was analyzed by SEM - Scanning 

Electron Microscopy, and the size of the particles was evaluated by OM - Optical Microscopy. The results 

showed that the efficiency of incorporation reached values in the range of 91.1 ± 2.4 % to 75.5 ± 2.1 %, and 

the SEM analysis proved the incorporation of the drug in the blend matrix.  

1. Introduction 

Sericin is a water-soluble globular protein that is easily soluble in hot or boiling water and is extracted from the 

silkworm Bombyx mori cocoons (Cao and Zhang, 2016). Most of the sericin is removed during the silk 

processing and it is usually discarded in the wastewater (Zhang, 2002).This fact leads to environmental 

contamination due to the high oxygen demand for its degradation by microbes (Aramwit et al., 2012). 

Therefore, find viable means to recover sericin would bring environmental and economic benefits (Aramwit et 

al., 2012). Sericin is a biocompatible and biodegradable protein, besides being digestible because of its 

susceptibility to the action of proteolytic enzymes present in the human organism (Padamwar and Pawar, 

2004). To improve its properties, sericin can be cross-linked, copolymerized and blended with other polymers 

due to its polar side chain made of hydroxyl, carboxyl and amino groups (Dash et al., 2009). Because of its 

characteristics, sericin has wide applications in medical, pharmaceutical and cosmetic industries (Padamwar 

and Panwar, 2004). 

Alginate is a nontoxic, biocompatible and biodegradable polysaccharide polymer (Dalaty et al., 2016). Alginate 

has muco and bioadhesive properties, is resistant to acidic pH and has chemical versatility that makes 

possible modifications in its properties (Sosnik, 2014). Thanks to these aspects, alginate has been widely 

used in many pharmaceutical applications, such as development of mucoadhesive and controlled release 

                                

 
 

 

 
   

                                                  
DOI: 10.3303/CET1652058 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Vidart J. M. M., Nakashima M., da Silva T. L., Rosa P. C. P., Gimenes M. L., Vieira M. G. A., da Silva M. G. C., 2016, 
Sericin and alginate blend as matrix for incorporation of diclofenac sodium, Chemical Engineering Transactions, 52, 343-348  
DOI:10.3303/CET1652058   

343



delivery systems for drugs and proteins (Dalaty et al., 2016). Therefore, the sericin/alginate blend can provide 

good conditions for drug incorporation (Khandai et al., 2010). 

Diclofenac sodium (DS) is a non-steroidal anti-inflammatory drug widely prescribed for its analgesic and anti-

inflammatory properties (Das and Subuddhi, 2015). This drug is used in the treatment of rheumatoid arthritis 

and osteoarthritis (Sinha et al., 2015). The biological half-life of DS is around 1 - 2 h and requires multiples 

dosing to maintain the therapeutic drug-blood level, what can cause adverse effects as gastritis, peptic 

ulceration and depression of renal functions (Nayak and Pal, 2011). A new matrix for DS can enable a 

sustained drug release with a minimal toxicity to the organism, which can reduce the drug side effects (Dutta 

and Sahu, 2012). 

In the present work, sericin/alginate particles with diclofenac sodium were prepared by ionic gelation method 

and the incorporation efficiency of DS was evaluated. The surface morphology was analyzed by Scanning 

Electron Microscopy (SEM) and the particles size was examined by Optical Microscopy (OM). 

2. Materials and Methods 

2.1 Materials 
The cocoons of silkworm were ceded by Bratac Silk Mills Company, Paraná, Brazil. Diclofenac sodium was 

provided by Pharmanostra, São Paulo, Brazil. Sodium alginate was purchased from Sigma-Aldrich, United 

Kingdom. Calcium chloride (CaCl2) was supplied by Neon, Brazil. Sodium phosphate tribasic, sodium 

hydroxide (NaOH) and hydrochloric acid (HCl) were provided by Dinâmica, Brazil. All the reagents were of 

analytical reagent grade purity. Deionized water (Milli Q) was utilized throughout the study. 

In order to investigate the DS efficiency incorporation, a simulated intestinal fluid (phosphate buffer pH 6.8) 

was freshly prepared by dissolving 38 g sodium phosphate tribasic in 500 mL of deionized water, followed by 

the addition of 1,500 mL HCl 0.1 mol/L. The pH was finally adjusted to 6.8 with NaOH 1 M or HCl 1 mol/L. 

2.2 Extraction sericin from cocoon of silkworm 
Sericin was extracted from silkworm cocoons employing the method presented in Silva et al. (2014). Firstly, 

40 g of cocoons, previously cleaned and cut, were added to 1 L of deionized water, and then, subjected to 

120 °C and gauge pressure of 1 kgf/cm2 for 40 min in autoclave (AV-18, Phoenix, Brazil). The sericin solution 

extracted was stored in a closed container at room temperature for 12 h, and thereafter, was frozen for 24 h. 

After this period, the solution was thawed at room temperature and filtered. The concentration of the sericin 

solution was adjusted to 2.5 % (w/v). 

2.3 Drug incorporation and preparation of particles 
In order to prepare the sericin/alginate blend, the sericin solution 2.5 % (w/v) was heated at 70 °C in autoclave 

for 10 min. The sodium alginate was added to the sericin solution at 55 °C, and the mixture was stirred at 

4,000 rpm. Then, DS was added to the sericin/alginate blend and dispersed with an Ultraturrax® (T18, IKA, 

USA) at 8,000 rpm until homogeneity was obtained. As shown in Table 1, particles at four different 

formulations were prepared using the ionic gelation method. The mixture of sericin, alginate and DS was 

added dropwise to a calcium chloride solution (3 % w/v), stirred continuously. After dripping, the particles were 

kept under stirring at 100 rpm for 30 min, and then washed with deionized water and dried at room 

temperature. 

Table 1: Formulations of sericin/alginate particles with diclofenac sodium (DS) incorporated 

Formulation Sericin (g) Alginate (g) DS (g) 

F1 2.5 1.25 2.0 

F2 2.5 2.60 2.0 

F3 2.5 3.30 2.0 

F4 - 4.00 2.0 

2.4 Determination of incorporation efficiency 
Accurately weighed 0.1 g of dried particles was added to 500 mL of phosphate buffer (pH 6.8), and kept 

overnight. Hence, the suspension was subjected to sonication for 15 min in a sonicator (1510RMTH, Branson, 

USA) and filtered through a 0.45 μm filter. The DS content in the filtrate was determined by spectrophotometer 

(UVmini1240, Shimadzu, Japan) at 276 nm. All determinations were carried out in triplicate. The incorporation 

efficiency was calculated by Eq(1). 

 100
Practical DS Content

Incorporation
Theoretical DS Content

 
(1) 

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2.5 Morphological examination and particles size 
The surface morphology of the formulated particles was analyzed by scanning electron microscopy (SEM). 

The samples were metalized with a thin layer of gold. The photomicrographs were taken at an acceleration 

voltage of 10 kV in electron microscope (440i, Electron Microscope LEO, England). 

The particle size of the prepared formulations was determined by optical microscopy (DC4-456H, National, 

EUA) using the software ImageJ (Dhirhi et al., 2016). The diameter of 500 particles was measured and the 

mean diameter was calculated for each formulation. Besides, the particle size distribution was investigated 

and the Gaussian model was adjusted. 

3. Results and Discussion 

3.1 Incorporation efficiency 
Figure 1 shows the effect of sericin and alginate concentration in the DS incorporation efficiency of the 

formulations prepared in accordance with Table 1. The incorporation efficiencies found were 91.1 ± 2.4 % to 

F1, 82.5 ± 3.6 % to F2, 77.9 ± 3.7 % to F3 and 75.5 ± 2.1 % to F4. It was noticed that the incorporation 

efficiency increased by increasing sericin proportion in the blend; therefore, sericin significantly contributes to 

the incorporations of the DS. 

 

Figure 1: Effect of blend composition in the DS incorporation efficiency 

3.2 Morphological examination (SEM) 
The surface morphology of the sericin/alginate/DS particles (F1, F2 and F3) and alginate/DS particles (F4) 

was visualized by SEM and is presented in Figure 2. By analyzing the F1 micrograph with magnification of 

150×, it was found that it has no clear-cut boundaries and has poorly defined shape, what does not favor the 

reproducibility of these particles. Spherical particles with a rough and rugged surface were observed in F2 and 

F3 micrographs with magnification of 150×. F4 micrographs indicated oval particles and a very rough and 

rugged surface too. Thus, it was evident from the SEM micrographs that balanced concentrations of sericin 

and alginate, as in F2 and F3, favor the sphericity of the particles. Drug crystals of DS were seen on the cross-

section of the particles at magnification of 3,000× for all formulations. Besides, it is verified that roughness 

increased by increasing alginate proportion in the blend. It can be inferred that the F4 particles (alginate/DS) 

possibly release the drug in its dissolution medium (gastric or enteric) more rapidly when compared to 

particles containing sericin in its composition, since the surface has greater roughness and therefore, its 

contact surface is higher. Consequently, particles containing sericin can contribute to the sustained release of 

the DS present in the matrix and maybe reduce the drug side effects. 

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Figure 2: Micrographs of formulations evaluated (as shown in table 1). (a) Particle with DS incorporated 

(Magnification of 150x). (b) Cross-section of the particle (Magnification of 3,000x) 

3.3 Particles size 
Figure 3 shows the effect of blend composition on particle size distribution and Table 2 presents the mean 

diameter of particles, in conjunction with the adjusted coefficient of determination for normal (Gaussian) 

F1 (a) F1 (b) 

F2 (b) F2 (a) 

F3 (b) F3 (a) 

F4 (a) F4 (b) 

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distribution fitting. By analyzing Figure 3, it can be seen that the size distribution of particles obtained for all 

formulations, except for F1, follow the normal distribution. The values of the mean diameters obtained for each 

formulation and the adjusted coefficient of determination (Ra2) are shown in Table 2, from which it is verified 

that the best fit is given to particles F2 with Ra2 = 0.9885. This result may indicate a better reproducibility of F2 

particles when compared to the others, once its distribution is symmetrical. 

 

Figure 3: Effect of blend composition on particle size distribution. 

Table 2: Particles size and distribution fitting. 

Formulation Mean Diameter  

(mm) 

Ra2 

F1 1.55 ± 0.42 0.9274 

F2 1.26 ± 0.15 0.9885 

F3 1.18 ± 0.14 0.9759 

F4 1.46 ± 0.20 0.9704 

By the evaluation of all the results presented, it was found that F2 and F3 particles showed the best properties 

for drug incorporation. These formulations exhibited good incorporation efficiency values, spherical particles 

with well-defined shape and size distribution according to normal distribution indicating increased 

reproducibility. 

Although F1 incorporation efficiency is the highest obtained from all the formulations developed, it was found 

from SEM analysis that it does not present a well-defined shape, which may limit the reproducibility of these 

particles, just as was observed by the size distribution curve and higher standard deviation of the mean 

diameter. 

F4 particles presented lower incorporation efficiency among all the other formulations, indicating the influence 

of sericin in the DS incorporation. The SEM micrographs showed an oval shape and higher roughness, which 

can negatively influence the drug release. The particle size distribution following a normal distribution model 

indicates that the particles are reproductive. 

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4. Conclusions 

In this study, sericin/alginate particles containing diclofenac sodium were successfully prepared employing 

ionic gelation method. The presence of sericin in the particles composition favors the drug incorporation, as 

verified by the increasing incorporation efficiency with the increasing sericin proportion in the blend. The SEM 

analysis showed that balanced concentrations of sericin and alginate, as in F2 and F3, favor the sphericity of 

the particles, and that the roughness surface increased by the increasing alginate proportion in the blend. 

Therefore, particles containing sericin can contribute to the sustained release of the DS present in the matrix 

and can possibly reduce the drug's side effects. For all formulations, except F1, the values of adjusted 

coefficient of determination were close to unity to normal fit modeling, indicating that the particle size 

distribution follows normal distribution and that the particles are reproductive. F2 and F3 particles showed the 

best properties for drug incorporation by the evaluation of all results presented. 

Acknowledgments 

The authors thank the BRATAC Company for providing the silkworm cocoons, CNPq (Proc. 470615/2013-3 

and 300986/2013-0), CAPES and FAPESP (Proc. 2015/13505-9) for financial support. 

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