1

HERBAL ANTIMICROBIAL FINISH USING

MICROENCAPSULATION TECHNIQUE

D.Gopalakrishnan - Author

Herbs were screened for their antimicrobial activity and extract preparation

process has been standardised. The herbal extracts were applied on cotton

fabrics directly by pad-dry-cure method with cross-linking agent Citric acid.

The antimicrobial activity of the finished fabrics was assessed against bacteria

that normally exist in textile environment like staphylococcus aureus and

Escherichia coli. To enhance the durability of the finish and controlled release,

the extracts were microencapsulated using simple Coacervation technique.

From the experiment it has been observed that microencapsulated finish

application retained its antimicrobial activity for more number of washes than

the direct application. . Comparing the screened herbs, neem proved to be best

in inhibiting bacterial growth.

INTRODUCTION:

Clothing and textile materials are carriers of microorganisms such as

pathogenic bacteria, odour-generating bacteria and fungi and it also act as good

media for the growth of microorganisms. Antimicrobial fabrics gained

significant importance in the recent years due to its wide acceptance as surgical

apparels, baby clothing, and undergarment etc.1

Antimicrobial finishes on

fabrics can protect human beings against microbes. The application of

antimicrobial textile finishes at present is confined to specialty products in the

medical, technical, industrial, home furnishing and apparel categories2.

Although, number of commercial antimicrobial agents have been introduced in

the market, their compliance with the regulation imposed by international

bodies like EPU is still a critical issue. Hence, there is significant development

in investigation of Eco-friendly, natural antimicrobial finish from herbs for

application on textile substrates.

2

Microencapsulation, a new technique emerging rapidly and widely used in

Pharmaceutical, chemical, cosmetic, agriculture and food processing and in

recent years to textile finishing3. In textiles the major interest in

microencapsulation is currently in the application of durable fragrances and

skin softeners. Other applications include insect repellants, dyes, vitamins,

antimicrobial agents, phase-change materials and medical applications, such as

antibiotics, hormones and other drugs4. In microencapsulation, an active core

material is encapsulated in a shell of limited permeability, so that the active

core material is protected from the external environment till required or to

affect the controlled release of the active core to achieve desired delay until the

right stimulus is encountered4. It is technique that allows liquid or solid agents

such as drugs, proteins, hormones, fertilizers, pesticides, dyes, cosmetics and

fragrances to be encapsulated by a suitable barrier wall. Of the

microencapsulation processes, the process of coacervation has been a major

research tool in polymer chemistry. Coacervation is the separation into two

liquid phases in colloidal systems5.

In this present investigation, herbal plant extracts are used as antimicrobial

finishing agents. Cotton fabrics are finished with these agents by pad-dry-cure

method with cross-linking agent like Citric acid. To retain the activity for

longer time and its controlled release, the extracts were microencapsulated by

simple coacervation technique.

An extensive study has been conducted to asses the antimicrobial effectiveness

and comparison of direct application and microencapsulated samples in terms

of antimicrobial activity and wash fastness was made and the findings are

discussed in the paper.

TREATMENT METHODS:

Materials:

Bleached 100% cotton fabric with the following specification was used for the

application of finish.

3

EPI : 80

PPI : 64

Count : 40s Carded.

Weave : plain.

Antimicrobial Herbs:

Six different medicinal plants were screened. Table1 shows the medicinal plant

and their specific part used.

Table 1. List of medicinal plant extracted

Sl.No Medicinal plants

Part used Common name Botanical name

1. Neem Azadirachta indica Leaves, Oil

2. Prickly chaff flower Achyranthes zaspera Leaves

3. Aloe-vera Aloe barbadensis Leaves

4. Thumbai Leucas cephalotes Leaves

5. Mexican daisy Tridax procumbens Leaves

6. Kuppaimeni Indian Acalpha Leaves

Extraction Method:

Leaves of medicinal plants were collected and shadow dried and made

into fine powder. Active substances were extracted from the plants by

Methanolic extraction method.

Application of herbal extracts on fabric:

Methanolic extracts of active substance were diluted with water to M: L of

1:20 and at 5% concentration, applied on fabric by pad-dry-cure method. Then

it is dried at 80C for 15 min. In order to improve the durability the sample

treated were post treated with cross-linking agent like Citric acid.

Micro-encapsulation method- Coacervation methods:

Method 1:

The microencapsulation was carried out at room temperature of 35C, using

gelatin as wall material and herbal extracts as core material. Thereafter,

4

acetone was added drop by drop with continuous stirring till precipitation of

microencapsulated antimicrobial is complete. The solution was decanted and

the microcapsules were obtained as a liquid dispersion.

Method 2:

In this method, Microencapsulation was carried out at the temperature of 40C

to 50C with neem oil as core material and gelatin as wall material. Sodium

sulphate and formaldehyde were used as hardening agents to form the

microcapsules. The mixture was freeze-dried to get powdered form of the

encapsulated material.

Method 3:

Gelatin microcapsules containing neem oil as core were prepared by this

method. Neem oil was added to the gelatin and the reaction medium acidified

to pH 2.0 by addition of Hydrochloric acid 1M. It is followed by emulsification

and slow addition of NaOH 1M upto pH 5.0 and the stirring was continued.

Cross linking of the gelatin precipitated around oil droplets was performed by

the addition of glutataldehyde 25% aqueous solution. The pH was constantly

adjusted to 5.0 the final product was collected after a decantation of the

reaction medium, and then freeze-dried.

Method of application: The microcapsules were applied on to the fabric using

binder by pad-dry- cure method.

Evaluation of Microencapsulated fabric under SEM:

The samples were treated from microcapsules of all the herbs and

they were observed visually and the topography or morphology of the fabric

samples was analysed using high-resolution scanning electron microscopy

with suitable accelerating voltage and magnifications. The scanning electron

micrographs were used for confirming the availability and their alignment of

microcapsules in textiles.

Antimicrobial Assessment:

5

Antimicrobial activity was ascertained by

qualitative method and quantitative test methods.

Antimicrobial Assessment of textile materials – Parallel streak Method

(AATCC 147 1993):

Specimens of test material and their corresponding untreated

controls of same material were placed in intimate contact with nutrient agar,

which has been previously streaked with an inoculum of test bacterium. After

incubation, a clear area of interrupted growth underneath and along the sides of

test material indicated antibacterial activity of the specimen.

Antimicrobial Assessment of textile materials – Agar Diffusion

Method( SN 195920):

Treated and Untreated control samples were placed in intimate contact

with bacteriostasis agar which was previously inoculated with a day culture (Slant

cultures) of the test organisms. After incubation, it was assessed by visual

examination as well as under a microscope with 40x enlargement. The evaluation

was made on the basis of absence or presence of an effect of bacteria in the contact

zone under the specimen and the possible formation of a zone of inhibition around

the test specimen.

Quantitative test : Reference or Confirmatory test ( Combined AATCC

100 and Hohstein modified test- Challenge test- JIS L 1902):

Swatches of treated and untreated materials were qualitatively assessed by

Parallel streak and Agar Diffusion method. Those showing activity were

evaluated quantitatively. Test and Control samples were inoculated with test

organisms. After incubation the bacteria were eluted from the swatches by

shaking in known amounts of neutralizing solution. The number of bacteria

present in this liquid was determined and the percentage reduction by the treated

specimen was calculated.

Wash Durability of finished fabrics ( AATCC 124 1996):

6

The fabric specimens were subjected to standard home

laundering practices and the residual antimicrobial activity was measured by

shake flask method (AATCC 100 1993) after 5 wash cycles and efficiency

was measured in terms of percent bacterial reduction.

Antimicrobial Activity of fabrics treated with herbs- Agar diffusion test

and parallel Streak Method:

Fig 1 shows the agar diffusion result of neem, aloe vera, thumbai

and prickly chaff against S.aureus and E.coli. It was found that neem showed

higher zone of inhibition of 53mm against S.aureus and 26mm against E.coli

when comparing to all other herbs screened.

Figure 1: Antimicrobial activity of herbs – Agar Diffusion Method.

7

Figure 2 shows the activity of the herbs against S.aureus and E.coli assessed

by Parallel streak method. It was found that the zone of inhibition is higher in

the case of neem treated fabric that is about 4.9 against S.aureus and the

activity against E.coli is 2.5mm which is reduced to fullest extent for all herbs.

Fig 2:Antimicrobial activity of herbs – Parallel Streak method

Preparation and evaluation of Microcapsules :

Microcapsules were prepared by using Alginate and gelatin as

Wall material and antimicrobial agent as core material by different methods.

8

The gelatin – based capsules shows more uniformity compared to alginate

based capsules and are bigger in size. Microcapsules are examined under

various magnification levels by means of image analysis light microscopy and

its is depicted in fig 3.

Fig 3: Evaluation of microcapsules formed by Coacervation process at

various magnification.

9

Evaluation of Microcapsule treated fabric under SEM:

The prepared Microcapsules were applied on to the fabric by

pad dry cure method and the presence of capsules were examined and

confirmed at different Magnification levels under SEM. Fig 4 shows the SEM

photographs of all samples at different magnification levels.

FIG 4:Evaluation of microcapsules treated fabric under SEM

4 a 4b

10

4a – Evaluation of microcapsule treated fabric under SEM at the magnification

level of 1000X

4b – Evaluation of microcapsule treated fabric under SEM at the

magnification level of 2000X

Wash Durability for neem treated samples:

It is found that the microencapsulated finish application has more

durability in terms of antimicrobial activity after washing than the direct

application.

Conclusions:

This work is a new attempt in combining the properties of Eco-friendly

antimicrobial and controlled release of microcapsules on cotton textiles. The

following works are successfully carried out. An eco friendly herbal

antimicrobial finish has been developed for cotton textile fabrics. Extracts have

been applied by direct pad-dry-cure method and microcapsule finish

application method. Microcapsules were prepared with neem, prickly chaff

flower, aloe vera and Mexican daisy extracts as core material and alginate,

gelatin as wall material. The capsules have been evaluated for its dimension

using Image Analysis Microscope and antimicrobial activity using AATCC

Test standards for antimicrobial in textiles. Durability was found to better in

microencapsulated finish than the direct application. The presence of

microcapsules in the finished sample was visualized by

SEM (Scanning Electron Microscope) and photographs were taken at various

magnification levels.

References:

11

1. R.B.Chavan , " Developments in environment friendly functional finishes

for cotton fabrics and garments ", NCM , December 2003 pp26.

2. Helmut Mucha, Dirk Hofer, Sigrid Assfalg & Maximilian Swerev,

Melliand International, 8(5) 2002, pp148.

3. Ramesh and rane ,' encapsulation Techniques- The novel approach to

textile finishing ",International dyer, July 2004, pp14.

4. Aggarwal et al, "Microencapsulation process and applications in textile

processing", Colourage, August 1998.

5. Gomes and Baptisa, " Microencapsulation of acid dyes in mixed lecithin /

surfactant liposomic structures", Textile Research Journal, 71(2), Feb 2001

pp153-156.

6. Hidekazu Yoshizawa," trends in Microencapsualtion research" KONA

No.2, 2004,pp23-31.

7. Edward," Antimicrobial Finishing for Speciality Textiles", International

Dyer, December 2002.

8. Ian Holme," Antimicrobials impart durable freshness", International Dyer,

December 2002.

9. Ian Holme," Versatile technology comes of age", International Dyers,

august 2003, pp9-12.

10. Gordon Nelson," Application of Microencapsulation in Textiles",

International Journal of Pharmaceutics, 242,2002,pp55-62.

11. Mucha H ," Antimicrobial finishes and modifications", Melliand

International vol.8 ,May 2002,pp148-151.

12. Nelson.G ," Microencapsulaes in Textile coloration and finishing", Review

of progress in coloration, 1991,21,pp72-85.

13. Nelson .G," Microencapsulation in textile finishing", Review of progress in

coloration, 2001,31,57-64.

14. Ian Holme ," Microencapsulation: the changing phase of finishing", Textile

magazine 2004 no.4, pp7-10.

12

15. Gokhan Erkan and Merih sariisik," Microencapsulation processes and

applications in textile processing", Colourage , August 1998.

16. Reza Arshady," Microspheres and Microcapsules- a survey of

manufacturing techniques –part II : Coacervation ", Polymer Engineering

and Science, Mid August ,1990, vol30 pp 905-924.