Indian Journal of Fibre & Textile Research

Vol. 37, December 2012, pp. 321-325

Micro-encapsulation and nano-encapsulation of denim fabrics with herbal extracts

M Sumithra1,a

& N Vasugi Raaja2

1Department of Costume Design and Fashion, PSG College of Arts and Science, Coimbatore 641 014, India 2Department of Textiles and Clothing, Avinashilingam Institute for Home Science and Higher Education for Women,

Coimbatore 641 043, India

Received 27 July 2011; revised received and accepted 27 February 2012

The present study focuses on the micro-encapsulation and nano-encapsulation to the 100 % cotton denim fabric using three

herbal extracts of Ricinus communis, Senna auriculata and Euphorbia hirta to impart their antimicrobial efficiency by finishing

the methanol extracts of these herbs on the denim fabric. The combinations of the herbal extract mix Ricinus communis + Senna

auriculata + Euphorbia hirta (1:3:2) and the conditions used as per the AATCC 147 (20kgf/cm2 pressure and 20m/min rpm

speed) for direct application to denim using exhaustion method give the best results in terms of antimicrobial efficiency. To

enhance the durability of the finished fabric, micro-encapsulation and nano-encapsulation of the herbal extracts are performed

and the results show good resistance for microbes even after 30 industrial washes against the test bacterial strains.

Keywords: Antimicrobial activity, Cotton, Denim fabric, Medicinal herbs, Micro-encapsulation, Nano-encapsulation,

Wash durability

1 Introduction

Consumers are now aware of the fact that bacteria can

grow and survive on fabrics commonly used in

healthcare environments for more than ninety days, thus

contributing to the transmission of diseases1, 2

.

Antimicrobial finishes using natural sources has been

the current vogue that promotes natural and ecofriendly

life style3. An innovative approach is to find out the

possibility of making the cloth microbial resistant by

applying the plant extracts containing active substances4.

These natural antimicrobial substances are not only

ecofriendly but are also taken from renewable sources5.

Microbial growth, especially bacteria, in textile materials

can result in the deterioration of fabric properties,

development of foul smells, skins irritation, and cross

infections6. Microbes are small organisms that cannot be

seen by the naked eye. They include a variety of micro–

organisms like bacteria, algae and fungi7. Encapsulation

is a process by which small solid, liquid or gaseous

substrates are covered by a polymeric or inorganic shell.

The resulting capsules or particles generally range from

micrometers to millimeters in size8.

Applications of micro-encapsulation include

controlled release of the active components, particle

coating, flavor stabilization, taste masking,

physical/chemical stabilization, improvement of shelf

life and prevention of exposure of the active material to

the surroundings 9. Two common technologies can be

used to obtain such nano-capsules and micro-capsules,

namely the interfacial polymerization of a monomer and

the interfacial deposition of a preformed polymer10

.

Denim has gained much popularity not by merely

complementing a rugged style, but by becoming suitable

for any occasion. Denim is being worn irrespective of

demographic differences11

. Denim is so durable because

only the warp yarns go through the dyeing process,

while the weft yarn is left natural without undergoing

any chemical process. This is the advantage of yarn dyed

fabric over piece dyed fabric12

.

The scope for denim wear is increasing

tremendously every year and its worldwide market

share has increased unpredictably in the last few

decades. Consumer’s needs are fine-tuned towards the

latest developments and new styles; they are also

aware of special finishes and process treatments given

to the garment to make them eco friendly and user

friendly. The present study focuses on the screening

for the antimicrobial activity of the natural herbs and

providing the denim fabric with the antimicrobial

finish from the screened herbal extracts. The

combinations and conditions are followed as per the

AATCC 147 methods. The study also aimed at using

micro-encapsulation and nano- encapsulation

techniques to increase the washing durability of the

antimicrobial finish provided from the herbal extracts.

__________________ aTo whom all the correspondence should be addressed.

E-mail: mithrasumi6@rediffmail.com

INDIAN J. FIBRE TEXT. RES., DECEMBER 2012

322

2 Materials and Methods

2.1 Materials

100% cotton denim fabric (GSM 219.4 g/m2, and

twill weave), sourced from the market, was used for

the application of antimicrobial finish. The herbs

Ricinus communis (leaves), Senna auriculata (leaves)

and Euphorbia hirta (leaves, stem and flower) were

used for obtaining the antimicrobial extract. The

plants and their parts were collected from Coimbatore

district, Tamil Nadu, south – east coast of India.

2.2 Preparation of Herbal Extracts

The collected plants were dried in a temperature

range of 100 – 140ο C, as they cannot be stored without

drying, thus avoiding the breakdown of important

compounds and contamination by microorganisms.

Garbling, the separation of that portion of the plant,

which is to be used, from other parts of the plants, dirt

and other extraneous matter, was done manually by

hand. Grinding or mincing of the leaves was carried

out in a mixer. The fine powder obtained after grinding

was used for extraction. Each 100 g of the powdered

plant material was refluxed in a Soxhlet apparatus in

1000 mL of methanol. After overnight incubation, the

supernatant was filtered through Whatmann No.1 filter

paper and the filtrate was dried to evaporate the organic

solvent at room temperature.

2.3 Finishing of Herbal Extracts on Denim Fabric

The denim fabric, purchased from K.G. Denim Ltd,

Coimbatore, was used for the study. The fabric

sample was given a primary wash with distilled water,

air-dried and then used for herbal finishing. The fabric

was finished with herbal extract by dip method. The

fabric was immersed in the extract for 30 min,

air-dried and then used for the antibacterial

assessment using standard bacterial strains.

2.4 Evaluation of Antibacterial Activity

In the preliminary screening, the herbal extracts with

antibacterial activity were mixed in various

combinations and conditions used for their

combinatorial antibacterial property by AATCC 147

test method. The AATCC plates were prepared by

pouring 15 mL of AATCC media in to sterile petri

plates. The plates were allowed to solidify for 5 min

and 0.1% inoculums suspension of the isolated wound

predominates were swabbed uniformly and the

inoculum was allowed to dry for 5 min. The herbal

extract finished denim fabric having the diameter of

23 mm was placed on the surface of medium and the

plates were kept for incubation at 37 ºC for 24 h. At the

end of incubation, zone of inhibition formed around the

fabric was ensured in millimeter and recorded. 2.5 Micro-encapsulation of Herbal Extracts

Microcapsules containing herbal extract were formed

by the addition of sodium alginate followed by spraying

into the calcium chloride solution by means of a sprayer.

The droplets were retained in the calcium chloride

solution for 15 min to harden the capsules. The

microcapsules were obtained by decantation and

followed by repeated washing with isopropyl alcohol

and then drying at 45 °C for 12 h. The microcapsules

were applied on the fabric by exhaustion method using

8% citric acid (cross-linking agent). The fabric was kept

immersed in the solution (ML ratio 1: 20) for 30 min at

50 ºC in water bath. After finishing, the fabric was

removed, squeezed and dried at 80 ºC in the oven for

5 min and then cured at 120 ºC for 2 min. The

antibacterial activity of the microcapsule-finished fabric

was analyzed by AATCC 147 test method. 2.6 Nano-encapsulation of Herbal Extracts

The herbal extracts prepared were encapsulated

using bovine albumin fraction as the wall material and

the nano particles as the core material.

The herbal extract enclosed bovine serum albumin

protein was prepared by coacervation process followed

by cross-linking with glutaraldehyde. After

glutaraldehyde treatment, for purification the solution is

put in rotary vaccum evaporator to remove the organic

solvent and then centrifuged at 4 ºC at 10,000 rpm and

then suspended in 0.1M phosphate buffer (pH 7.4). Then

Lyophilized with mannitol (2% w/v). The herbal extract

was incubated with the required protein solution

(2% w/v) for an hour at room temperature. The pH of

the solution was adjusted to 5.5 by 1M HCL using

digital pH meter. Then ethanol was added to the solution

in the ratio of 2:1 (v/v). The rate of ethanol addition was

carefully controlled at 1 mL per min. The coacervate so

formed was hardened with 25% glutaraldehyde for 2 h

to allow cross-linking of protein. Organic solvents were

then removed under reduced pressure by rotary vacuum

evaporator and the resulting nanocapsules were purified

by centrifugation (10,000 rpm) and at 4 ºC. Pellets of

nanocapsules thus obtained were then suspended in

phosphate buffer (pH 7.4; 0.1 M) and each sample was

finally lyophilized with mannitol (2% w/v). The

nanocapsules obtained were further dried by

lyophilisation and then applied on the cotton fabric by

exhaustion method using 8% citric acid as binder. The

fabric was finished following the conditions M:L ratio

SUMITHRA & RAAJA: MICRO-ENCAPSULATION AND NANO-ENCAPSULATION OF DENIM FABRICS

323

1:20, binder (citric acid) 8%, temperature 55 ºC and time

30 min. The antibacterial activity of the nanocapsules

finished fabric was determined by AATCC 147 test

method.

2.7 Wash Durability Test

The microcapsules finished denim fabric and

nanocapsules finished denim fabric were analyzed for

their wash durability by subjecting the sample to

washing and testing their antibacterial efficiency. The

denim fabric was subjected to washing by industrial

machines and the antibacterial activity of the washed

fabric was assessed by AATCC 147 test method.

2.8 Scanning Electron Microscopy

The scanning electron microscopy was used for

confirming the binding of microcapsules and

alignment on to the fabric sample.

3 Results and Discussion

3.1 Determination of Antibacterial Activity of Finished Fabric

The finished fabric was assessed for the antibacterial

activity by AATCC 147 test method against Escherichia

coli and Staphylococcus aureus. The zone of inhibition

for the fabrics finished with methanolic extract of

Ricinus communis, Senna auriculata and Euphorbia

hirta is 0 (no bacterial growth), 25 and 24mm

respectively for Escherichia coli and 27, 30, 29 mm

respectively for Staphylococcus aureus.

The methanolic extract of the herbs is found to be

efficient in providing antibacterial activity to the

finished fabric. Of the three herbs used, the methanolic

extract of Senna auriculata is found to give maximum

antibacterial activity compared to the other two herbs.

The best herbal combination is selected to be 1:3:2 of

Ricinus communis, Senna auriculata and Euphorbia

hirta respectively. A treated fabric is having very good

antibacterial properties to both Gram positive and

Gram negative micro-organisms. The treated fabrics do

not allow the growth of bacteria under the test

specimens. The zone of inhibition values indicate that

the herbal extracts not only prevent the growth of

bacteria under the fabric but also leaches out and kills

the bacteria. The growth rate of bacteria is 2.7 × 109

cfu/mL for E.coli, and 2.4 × 109 cfu/mL for S. aureus.

Antibacterial activity of ajwain seeds extract treated

fabrics using qualitative and quantative methods has also

been reported13

. Antibacterial property of extract alone

clearly shows extended zone of inhibition (20-30 mm)

for both types of microorganism (Gram positive and

Gram negative) when analyzed by AATCC 147 (parallel

streak method). Test results show that all treated fabrics

have very good antimicrobial property to both

Staphylococcus aureus and Klebsiella pneumonice

micro-organisms. The treated fabrics do not allow the

growth of bacteria under the test specimen. In all the

cases, there is a good zone of inhibition ranging from

11.9 mm to 14.5 mm for Staphylococcus aureus and

from 6.9 mm to 7.1 mm for Klebsiella pneumonice.

Nascimenta et al.14

showed that the extracts from basil,

clove, guava, jambolan, lemon balm, pomegranate,

rosemary and thyme show antimicrobial activity to at

least one of the tested microorganisms. The extracts

from clove and jambolan show the highest activities, i.e.

they are able to inhibit 9 (64.2 %) and 8 (57.1 %) types

of microorganisms of interest respectively. 3.2 Micro-encapsulation of Herbal Extract

In order to increase the durability of the finished

fabric, the effective herbal combination is

microencapsulated by ionic gelatin method. The

antibacterial activity of the finished fabric and the

fabric after washes have been tested and the results

are presented in Table 1.

The antibacterial analysis shows that the

microcapsules of the herbal extract finished denim fabric

shows activity for the sample after 20 washes, They

exhibit potential for antimicrobial activity against

Staphylococcus aureus and Escherichia coli. It is

observed that the microencapsulated herbal extracts

possess a very good resistance for microbes even after

15 washes. Thilagavathi et al.15

defined the

antimicrobial efficiency in terms of bacterial reduction

percentage for directly applied and herbal microcapsules

applied fabric samples. It is clear that the herbal extracts

both directly applied and microencapsulated posses

better activity against Staphylococcus aureus than

Table 1—Antibacterial activity of the microcapsules and

nanocapsule finished fabrics

Zone of bacteriostasis

mm

(microcapsule)

Zone of inhibition,

mm

(nanocapsule)

Samples

E.coli S.aureus E.coli S.aureus

Finished

fabric

24 33 30 35

Finished

fabric after

10 washes

0 30 29 33

Finished

fabric after

20 washes

0 27 28 30

Finished

fabric after

30 washes

0 0 24 25

INDIAN J. FIBRE TEXT. RES., DECEMBER 2012

324

against Escherichia coli. It is also found that directly

applied herbal extract samples do not show much

activity after 10 washes. This is because the extracts are

coated only on the surface without any firm bonding and

get removed by washing. This was ascertained when the

structure of microcapsules was studied by scanning

electron microscopy using image analysis technique.

The antimicrobial efficacy by quantitative method in

terms of bacterial reduction and the wash durability of

antimicrobial activity was studied by agar diffusion

method (AATCC 124). The sample exhibits potential for

antimicrobial activity against Staphylococcus aureus and

Escherichia coli. It is observed that the

microencapsulated herbal extracts possess a very good

resistance for microbes even after 15 washes. So, in

order to increase the durability of the fabric, the herbal

extracts are nano-encapsulated and the antibacterial

activity of the fabrics is presented hereunder.

3.3 Nano-encapsulation of Herbal Extract

The nanocapsules of the herbal extracts are

finished on the denim fabric by exhaustion method

and the antibacterial activity of the finished fabric as

well as for the fabric samples after washes are studied

(Table 1 and Fig. 1). The results show that the fabric

finished with nanocapsules prepared from herbal

extracts is able to retain the antimicrobial activity

even after 40 industrial washes, thereby providing

long term durability to the finished fabric. El-molla

et al.16

pointed out that for imparting antibacterial

properties, nano-sized silver, titanium dioxide and

zinc oxide are used. The effect of TiO2 nano particles

concentration with and without using 4% PUA binder

on antimicrobes on either screen printed or pigment

dyed silk fabric shows that the use of PUA binder

alone has no effect on the antimicrobial property. But

upon using TiO2 in either printing paste or in ink

preparation, good results are observed against

Escherichia coli and Staphylococcus aureus. Also, the

results obtained in case of printing are better than

those obtained in case of dyeing.

3.4 SEM Study

SEM photographs of nanocapsule finished fabric

and the fabrics after 10, 20 and 30 washes are shown

in Figs 2 & 3 at different magnification levels. It is

Fig. 1—photographs showing zone of inhibition of nanoencapsuled denim fabrics [(a) for E. coli , (b) for S. aureus, (c) for E. coli after

10, 20 and 30 washes, and (d) for S. aureus after 10, 20 and 30 washes]

Fig. 2 SEM photographs of nanocapsules finished fabrics under

different magnifications [(a) × 250, (b) × 500.(c) × 1,000 and

(d) × 3,000]

SUMITHRA & RAAJA: MICRO-ENCAPSULATION AND NANO-ENCAPSULATION OF DENIM FABRICS

325

clear that the nanoencapsules adhere not only on the

surface, but also penetrate into the interstices of the

yarn and fabric. This clearly indicates that the

nanoencapsules are bonded well to the fabric surface

even after 30 washes.

4 Conclusion

The results show promising use of these herbal

extracts (Ricinus communis, Senna auriculata and

Euphorbia hirta) as source of antimicrobial finishing

on denim fabric. The extract finished fabric shows

maximum antibacterial activity against both

Escherichia coli and Staphylococcus aureus. The

durability of the herbal finishing is increased by

micro-encapsulation and nano-encapsulation methods;

the results show antimicrobial effect even for the

washed fabrics against the standard strains.

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Fig. 3—SEM photographs of nanocapsules finished fabrics after

10, 20 and 30 washes under different magnifications

[(a) × 250, (b) × 500, (c) × 1,000 and (d) × 3,000]