Encapsulation of Rosemary Oil in Ethylcellulose Microcapsules

8/13/2019 Encapsulation of Rosemary Oil in Ethylcellulose Microcapsules

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Vol.1. No.1. 2009 13

1. Introduction

Microencapsulat ion is one of the latest

technologies used for imparting an array of

unique characteristics to a garment. Particles

filled with active ingredients are applied to

the fabric or garments for long lasting effects.

Microencapsulated particles can be coated on

a textiles' surface or anchored (Chemically or

physically) onto the fi ber. As the wearer moves,

the capsules are activated and they release

the active ingredient in a controlled manner.

The active ingredients in the garment can be

moisturizers, vitamins, therapeutic smells,

essential oils, drugs and others [1,2,3,4,5,6,7,8,9,10]. The

properties of microcapsules (Figure 1), size,

shape, wall material, active substance release

mechanism, have had to be adapted to the

requirements of textile processing methods and

use of final products.

In our current research Rosemary oil

was encapsulated in ethylcellulose (EC)

microcapsules using the phase separation

method [11,12]; the prepared capsules were

analyzed by Scanning Electron Microscopy

(SEM) and Confocal Laser Fluorescence

Microscopy (CLSM). Prepared capsules were

grafted onto cotton textile substrate as mentioned

in literature[11]

; prepared textile materials were

analyzed by Confocal Laser Fluorescence

Microscopy.

2. Experimental

2-1 Materials

Ethylcellulose (EC) was purchased from

Encapsulation of Rosemary Oil in Ethylcellulose Microcapsules

B.Voncina1, O.Kreft2, V.Kokol1, W.T.Chen3

Dept. of Textile Materials and Design, University of Maribor, Maribor, Slovenia1,

Max-Planck-Institute of Colloids and Interfaces, Potsdam-Golm, Germany2

Dept. of Raw Material and Yarn Formations, Taipei, Taiwan, R.O.C.3

Abstract : In textiles, the major interest in microencapsulation is currently in the application of durable fragrances, skin softener,

phase-change materials, antimicrobial agents and drugs delivery systems onto texti le materials. In our research

Rosemary oil was encapsulated in ethylcellulose (EC) microcapsules using a phase separation method; the prepared

capsules were analyzed by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM).

The Rosemary oil content in the microcapsules was determined by using CLSM. Capsules were grafted onto cotton

textile substrate; the presence of microencapsulated Rosemary oil attached to textile materials was tested by CLSM.

Key words : Microencapsulation, ethylcellulose, confocal laser scanning microscopy, cellulose fi bers.



Textile and Polymer Journal14

Aldrich, Austria (Viscosity 4 cP, 5% in toluene/

ethanol 80:20, extent of labeling: 48% ethoxyl).

Rosemary oil was provided by Etol, Celje,

Slovenia. 1,2,3,4-Butane tetracarboxylic acid

(BTCA) by Merck, cyanamide (CA) and

fluorescence dye: fluorescein (FITC) from

Aldrich and sodium dodecylsulphate by Fluka

were used. All other chemicals were of analytical

reagent grade.

Pure cotton (Mass = 140 g/m2) was used

after it was first desized, scoured, bleached and

mercerized on continuous production equipment.

It was supplied by MTT, Maribor, Slovenia.

2-2 Test methods and analytical techniques

The microcapsule yield was determined as a

weight percent of the recovered microcapsules

after drying, divided by the initial amount of

ethylcellulose and oil employed.

Diameters and surface morphol ogy of

microcapsules were examined by scanning

electron microscopy (SEM). The samples were

coated with gold for 3.5 min using an Emscope

SC 500 and examined using a Philips XL30

ESEM operating in the secondary electron mode

at 10 KV accelerating voltage. The Quanta has

a tungsten based electron optical column with

a resolution of 3.5 nm and an ion resolution of

10 nm. Measurements were taken in vacuum at

different magnifications. Diameters of capsules

are presented as the mean value ± standard

deviation (SD) of fifty measurements.

For Rosemary oil content in capsules

two methods were used; in first one the oil

in capsules was removed by extraction and

from the differences in capsules mass before

and after extraction the amount of oil was

determine; in the second method the proportion

of empty capsule space was determine by using

CLSM. Confocal images were taken with a

Leica confocal scanning system mounted to a

Leica Aristoplan and equipped with a 100x oil

immersion objective with a numerical aperture

(NA) of 1.4. For visualization, FITC was used to

stain the capsules.

2-3 Preparation of EC microcapsules

and Rosemary essential oil content

determination

EC microcapsules were prepared as reported

in the literature [11]. In order to determine the

Rosemary essential oil content in capsules two

methods were used.

The Rosemary oil content in EC microcapsules

has been determined by pouring them into

cyclohexane and ultrasonicating for 1 min

to extract Rosemary oil from the capsules.

The oil content (ROC) expressed in percent

was determined from the mass differences

of microcapsules containing Rosemary oil

(mECRO) and capsules after oil extraction

(MEC). Five repeated measurements were



Vol.1. No.1. 2009 15

carried out.

The following equation was used:

mECRO-mEC

ROC= 100% mECRO

EC microcapsules contain around 30% of

Rosemary oil.

In the second method, where Confocal Laser

Scanning Microscopy was used, we placed

one drop of an aqueous capsule suspension

containing essential oil onto a microscope glass

slide and mixed it with a fluorescein solution

(0.1 mg/ml H2O). Capsules without Rosemary

oil were treated likewise and acted as a negative

control. Within a few seconds, the fluorescein

penetrated the capsules wall and the overa ll

fluorescence intensity within the boundary of

one capsule was determined by CLSM (Figure 2).

The flourescence intensity of an identical region

outside the capsule was used for calibration

and set to 100 percent (Figure 2). Ten repeated

measurements were carried out. By comparison

of the fluorescence intensity of the capsule area

with fluorescence intensity of the same blank

area it is possible to estimate the proportion of

empty capsule space. The average empty space

in prepared capsules was 40%.

2-4 Grafting of EC microcapsules on textile

substrate using BTCA

EC microcapsules were linked onto cotton via

grafting with 1,2,3,4-butanetetracarboxylic acid

(BTCA) as described in literature[6,11]

. Empty

and with Rosemary oil loaded microcapsules

grafted on textile materials were analysed by

using CLSM.

3. Results and discussions

3-1 Analysis of ethylcellulose microcapsules

From the SEM shown in Figure 1 it was

observed that EC microcapsules had a regular

spherical shape. Microcapsules in the 10-90µm

size range were obtained.

Figure.1. SEM image of EC microcapsules containingrosemary oil (1000× magnification).

The size and degree of sphericity of

the microcapsules depend on the stirring

speed employed in the encapsulation. Table

1 presents the inf luence of the s t i r r ing

speed on microcapsule diameter and on

microencapsulation yield. Reducing the stirring

speed increases the size of microcapsules. The

yield of microencapsulation was measured by

comparing the total weight of the microcapsules

with the combined weight of the polymer and

oil. Good results in terms of recovery, shape

and size distribution were obtained in the case

of blank microcapsules (Table 1). The presence




Table1. Influence of the stirring speed on yield of microencapsulation and diameter of microcapsule.

OilStirrer speed,

rpm

Yield,

%

Diameter± SDa,

µm

Rosemary oil

350 68 72±8

500 58 43±13

750 67 42±5.6

1000 50 20±5.1

Blank microcapsules 350 75 78±15

aeach value represents the mean± standard deviation (SD) of fifty measurements

3-2 Rosemary oil content determination

The Rosemary oil content (ROC) of 30%

was determined from the mass differences of

microcapsules containing Rosemary oil and

capsules after oil extraction by using ultrasound.

By using CLSM (The second method mentioned

in paragraph 2.3), the representative CLSM

images of empty EC microcapsules and ECmicrocapsules containing Rosemary oil were

studied. Figure 2 presents microcapsules without

Rosemary oil "embedded" in fluorescent dye.

By comparison of the fluorescence intensity of

the capsule area with fluorescence intensity of

the same blank area it is possible to estimate

the proportion of empty capsule space. The

average empty space in prepared capsules was

determined to be 40%. Figure 3 a presents CLSM

images of microcapsules containing essential

oil "embedded" in fluorescence dye and empty

microcapsule "embedded" in fluorescence dye

as Figure 3. In the case when microcapsules

contain hydrophobic Rosemary essential oil

(Figure 3a) the penetration of the hydrophilic

fluorescence dye into capsule's porous systems is

hindered, while in the case of empty capsules the

hydrophilic fluorescent dye can penetrate into

capsules easily.

of oil causes deficiencies of the microcapsule

recovery. In order to facilitate the encapsulation

of oil, this should have a density comparable to

that of the aqueous external phase and complete

immiscibility with the external phase. The

density of Rosemary oil is 0.91 g/ml which could

explain the slight decrease in yield of Rosemary

oil microencapsulation.



Vol.1. No.1. 2009 17

Figure.2. Microcapsules without Rosemary oil

"embedded" in fluorescent dye.

Figure.3. Microcapsule containing essential oil

"embedded" in fluorescence dye (a) and empty

microcapsule "embedded" in fluorescence dye (b).

3-3 Microcapsules on textile substrate

Prepared microcapsules containing Rosemary

oil and microcapsules without Rosemary oil were

covalently bound to hydroxyl groups of cellulose

by using BTCA. Grafting of microcapsules onto

textile materials occurred at 110°C for 2 min

thus some of the essential oil might evaporated

through the microcapsule walls. When textile

material grafted with empty microcapsules was

embedded in fluorescence dye solution, the dye

penetration into microcapsules was indicated

by the capsules colouring green (Figure 4a), on

the other hand, fluorescence dye penetration

into microcapsules was hindered when textile

materials was grafted with microcapsules

containing Rosemary oil. This can be indicated

by black microcapsules on image b in Figure 4.

We can conclude that heating of microcapsules

containing Rosemary oil at 110°C for 2 min

during the grafting process does not have a

significant influence on the Rosemary oil content

of microencapsulated textile material.

a)

b)




Figure.4. Microcapsules without Rosemary oil on

textile materials "embedded" in fluorescence dye, a)and microcapsules containing Rosemary oil on textile

materials "embedded" in fluorescence dye, b).

4. Conclusion

This work described the preparation of

EC microcapsules containing Rosemary oil

by th e ph ase separ at ion me tho d. The size

range of EC microcapsules depends on the

stirring speed employed during encapsulation.

Reducing the stirring speed increased the size

of microcapsules. The Rosemary oil content in

microcapsules was determined by extraction of

oil in cyclohexane by ultrasound and CLSM. We

observed that the oil content is about 30% and

that the empty space in capsule is around 40%.

We can conclude that results obtained from both

methods are comparable; EC microcapsules

have in average 40% of empty space which

are is fully occupied by Rosemary oil. Further,

microcapsules were grafted onto cotton textile

substrate and the presence of Rosemary oil in

microcapsules bonded onto textile materials was

tested by CLSM. We observed that after grafting

of microcapsules on textile materials at elevated

temperature the Rosemary oil is still present in

microcapsules. This indicates that grafting of

EC microcapsules containing Rosemary oil onto

textile materials at 110°C for 2 min by using

BTCA is appropriate method to prepare textile

materials for cosmetic application.

Acknowledgement

We are grateful to European project MTKD-

CT-2005-029540 POLYSURF, for its financial

support.

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Encapsulation of Rosemary Oil in Ethylcellulose Microcapsules