Aloevera, chitosan and turmeric were applied individually and in combination form by exhaustion method on cotton, wool and rabbit hair. The treated materials were assessed for their antimicrobial activity. Aloevera has shown better antimicrobial activity than others when applied alone, and its antimicrobial activity has been increased by the addition of both chitosan and turmeric. This antimicrobial finishing was withstanding fully on cotton and wool substrates up to 20 washing cycles.

Enhancement of effect of Aloevera for its Antimicrobial property on Cotton and Protein fibers using Selected Additives

Dr.J. Jeyakodi Moses and L. Ammayappan

INTRODUCTION

In the textile and garment world, finishing plays a vital role for quality and value. In the abundance of various finishes, importance is given to antimicrobial finish since people take much care about health and hygiene. The textile consumers become much more aware of the deleterious effect that the microorganisms may have upon textiles and upon human hygiene. The consumers desire greater safety and better comfort by avoiding unpleasant odour. Nowadays, a number of finishing treatments are applied on textile garments depending upon the market values and customers taste. The finishes like bio washing, stone washing, enzyme washing, acid washing, denim washing, cool finishing and odour finishing are attracting the market. Apart from these, the anti microbial finish is considered very important on garment due to its effectiveness towards the quality of garments as well as the hygienic side of the customers. Therefore, it has been decided to impart anti microbial finish on cotton fabric, wool fiber and angora rabbit hair with anti microbial sources such as Aloevera, Chitosan and Turmeric at high pressure and high temperature. The fibers are opened at these conditions and facilitate polymeric reactions, hence making the finish permanent even after several washes. The ingredients used are eco friendly and give good effect to human skin in addition to values on garments. These materials with anti microbial finished effect could be used for the production of many valuable garments such as baby garments, formal and non formal garments and home furnishings.

Antimicrobial Finishing

The growth of microorganism on textiles can lead to functional, hygienic and aesthetic difficulties. The most trouble causing organisms are fungi and bacteria. Under very moist conditions algae can also grow on textiles but also troublesome only because that act as nutrient sources for fungi and bacteria. Fungi cause multiple problems to textile including discoloration colours stains and fiber damage, unpleasant odors and a slick, slimy feel. The growth rate of microbes can be astoundingly rapid. In an ideal condition (36-40oC , pH 5-9) one single bacteria cell can increase to 1048576 cells in just 7 hours. For antimicrobial treatments, reagents such as organic silicon quaternary ammonium compounds, halogenated diphenyl ether derivatives, nitrofurantoin, and organic nitrogen compounds are frequently used; among which organic silicon quaternary ammonium compounds are the most common. Antimicrobial activity is achieved by the quaternary ammonium compound cation, which grabs the bacterial anion, destroying the cell wall of the bacteria and causing the interior contents to exude, thus killing the bacteria. Antimicrobial finishes that control the growth and spread of microbes are more properly called biostats i.e. bacteriostats, fungistats. Products that actually kill microbes are biocides i.e. bactericides / fungicides (1, 2, 3).

Mechanisms of antimicrobial finishes

Antimicrobials can be divided into two types based on the mode of attack on microbes. The first type antimicrobial (Controlled release mechanism)is slowly released from a reservoir either on the fabric surface or in the interior of the fiber. This leaching type of microbial can be very effective against microbes on the fiber surface or in the surroundings environment. The second type of antimicrobial finish consists of molecules that are chemically bound to the fiber surfaces. These products can control only those microbes that are present on the fiber surface not in the surrounding environment. Bound antimicrobials because of their attachment to the fiber can potentially be abraded away or become deactivated and lose long term durability. The efficiency of antimicrobial finishes are extremely varied ranging from preventing cell production, blocking of enzymes, reaction with cell membrane to the destruction of the cell walls and poisoning the cell from within(4).

Antimicrobial chemicals

Antimicrobials for controlled release
Benzimidazol derivatives, salicylanilides and alkylolamide salts of undecylenic acid are applied with resin precondensates. Application of these chemicals with resin precondensate improves durability to laundering, but also deactivation by reaction with the resin may occur. A variety of modified fibers have been developed by incorporation of 0.5-2.0 % of organic nitro compounds such as 5-nitrofurfural before primary wet or dry spinning. Regenerated celluloses can be modified with carboxylic or disulphonic acid groups followed by immersing in a solution of cationic antimicrobials which are then fixed to the cellulose by salt bonds. One of the most widely used antimicrobial chemical is 2,4,4'-trichloro-2'-hydroxy diphenyl ether known as triclosan which is applied in presence of a dispersing agent and a binder. A novel approach to the controlled release of antimicrobials is microencapsulation.

Bound antimicrobials

Quaternary ammonium compounds such as octadecyl-amino-dimethyl-trimethoxy-silyl ammnonium chloride and polyhexamethylene biguanide can be applied with siloxane polymer by pad-dry-cure technique. The polymer immobilizes the antimicrobial part of the molecule (the quaternary nitrogen) and provides necessary durability to launderings. The antimicrobial effect of cationically charged materials is thought to involve interaction of the cationic molecule with anionic phospholipids in the microbe's cell wall (5, 6, 7, 8).

Chitosan

Chitin is an analogous of cellulose with N-acetyl groups instead of hydroxyl groups in position C2 modification. Chitin is converted into chitosan by alkali treatment. Alkali splits N-Acetyl groups into free amino groups (75-95%) that provide fungi static and bacteriostatic effects. It is chemically called as beta-(1,4)-2-(amino)-2-deoxy-D-glycopyranose.In aquous solution at pH < 6.5 , it is its protonated form and behaves like a cationic polyelectrolyte and interacting with negatively charged molecules. It can be applied by microencapsulation or by reactive bonding to cellulose and by cross linking of chitosan. The chitosan finish includes high absorbency properties, moisture control, non-allergic, non-toxic and biodegradable properties to textiles (9).

Aloevera

Aloevera is a natural plant, gives maximum extent of is aloe gel which has very good anti microbial effect together with other functional properties suitable for textiles. The aloe gel contains over 75 different ingredients including vitamins, minerals (Sodium, potassium, calcium etc.), enzymes (amylase and lipase & carboxy-peptidase), sugars(glucose & mannose), anthraquinones or phenolic compounds (Barbaloin, lsobarbaloin & Anthrone-C-glycosides), lignin, saponins, sterols, amino acids and salicylic acid. These componenets are bactericidal against Pseudomonas a., Klebsiella p., Serratia m., Citrobacter, Enterobacter c., Strep. Pyogenes and agalactiae and inhibited the growth of Mycobacterium, Trichophyton, and Bacillus subtilis (10).

Turmeric

Turmeric is the dried rhizome of the plant Curcuma domestica, a perennial herb. The active constituents of turmeric are the flavonoid, curcumin and volatile oils including tumerone, atlantone, and zingiberone. Other constituents include sugars, proteins, and resins. The best-researched active constituent is curcumin, which comprises 0.3 to 5.4% of raw turmeric and chemically called as 1-7-diaryl-1,6-diene-3,5-dione. It inhibits growth of various bacteria like S. aureus, S. paratyphi, Trichophyton gypseum and Mycobacterium tuberculosis in concentrations varying from 1 in 20,000 to 1 in 640,000. The essential oils show marked anti-microbial activity against gram negative organisms and gram-positive organisms. The essential oil fractions from C. longa rhizomes of various habitats exhibit fungistatic activity particularly against Aspergillus niger and Physalospora tucumanesis (11).

Experimental

Materials

The materials with the following specification are taken for this study. 100% Cotton fabric (plain weave, Count: 80s, EPI- 78 and PPI-60), Bharath Merino wool fiber (27 micron fineness, 3" length) and Angora Rabbit hair (16 micron fineness and 4" length). The protein fibers are mild scoured prior to finishing application.

Antimicrobial agents

Chitosan, with a deacetylation of 90% or above was procured from Central Marine Fisheries Research Institute, Kochi-682 018. Aloevera was procured in gel form and commercial turmeric was procured in powder form. All other chemicals were laboratory grade reagents.

Methods

Pretreatment for Cotton

The semi bleached cotton fabric is subjected to hydrogen peroxide bleaching to increase absorbency and whiteness as per standard recipe (12).

Pretreatment for wool fiber and Angora Rabbit hair

The formic acid treatment is given for wool fiber and Angora rabbit hair. The bath is set with 10% (owm) formic acid and the material is entered at room temperature and treated for 30 minutes. Then it is washed with cold water and rinsed with cold water and dried.

Antimicrobial Treatment

The required quantity of antimicrobial reagents are taken and set in a bath. The sample is entered into the antimicrobial bath with pH 5-6 adjusted with acetic acid. The bath temperature is raised to boil and it is kept at this temperature for 30 minutes. After 30 minutes, the bath is cooled to room temperature and the sample is taken out and rinsed with warm water. Finally they are washed with cold water and dried. Antimicrobial agents used in different proportions and combinations are as follows.

1. Aloevera- 5 gpl
2. Turmeric- 5 gpl
3. Chitosan- 3 gpl
4. Turmeric- 5 gpl Chitosan- 3 gpl
5. Aloevera- 5 gpl Turmeric- 5 gpl
6. Aloevera 5gpl Chitosan- 3 gpl
7. Aloevera 5gpl Turmeric- 5 gpl Chitosan- 3 gpl

Assessment of Antimicrobial activity of control and finished samples

The antimicrobial activity of control and finished samples is determined as per standard described by Quinn. The amount of bacterial and fungal growth in inoculated and incubated samples is determined through serial dilution (10-1,10-2 and 10-3) and subsequent inoculation of sterile agar. The numbers of bacterial and fungal colonies are counted visually using a microscope (13). The wash fast test was carried out according to ISO6330-1984E, with a precision washer, which conducts 5, 10, 15, and 20 washings, and then the antimicrobial characteristics were measured.

RESULTS AND DISCUSSION

Antimicrobial activity of finished samples without pretreatment

Tables 1 & 2 show the bacterial and fungal observation in cotton, wool and rabbit hair that are treated with aloevera, chitosan and turmeric individually without any pretreatment. It depicts that without pretreatment, the residual impurities present in the natural fibers have influence for the microbial growth. This trend is continued even for the combined treatment of antimicrobials. So it was decided to pretreat the fibers in order to improve the efficacy of antimicrobial activity.

Antibacterial activity of finished samples with pretreatment

Table 3 shows the antimicrobial assessment in terms of bacterial observation in cotton, wool and rabbit hair that are treated with aloevera, chitosan and turmeric individually and by their combination. It is observed that the bacterial growth is reduced after application of antimicrobial agents either alone or in combination. When the antimicrobial agents are applied alone in cotton fabric, the antimicrobial activity is better in aloevera treatment than chitosan and turmeric, while in protein fibers it is in the order of aloevera >turmeric> chitosan. Aloevera contains different components such as polysaccharides, anthroquinones, salicylic acids, amino acids etc. It is noted that acemannon (polysaccharide) and salicylic acid help to promote antimicrobial activity and it has been enhanced by amino acids, minerals (zinc) and saponins (14). The antimicrobial activity of chitosan is differed with respect to fibers and the reason is explained as follows. It is assumed that chitosan sorption on cotton fiber and protein fiber is due to ionic interaction between the negative charges (hydroxyl groups in the cellulose fibers and carboxylate groups in protein fiber) and the protonated amino groups of chitosan and to the H-bonding between the hydroxyl groups of fiber and similar groups in chitosan as well as van der Waals' forces. These interactions are known to be weak and hence chitosan affinity for cotton and wool can be generally regarded as weak and so it is not able to give durable antimicrobial activity when applied alone (15, 16, 17). Curcumin (18), the main component of turmeric have only phenolic groups, which are forming only hydrogen bonding with hydroxyl groups of cellulose and amino / hydroxyl groups of protein. Since the molecular size of curcumin is smaller than the chitosan, its exhaustion is higher than chitosan in the fiber and so its antibacterial effect is slightly better than chitosan.

When the antimicrobials are applied in combination, the antibacterial effect is better in aloevera combination than non-aloevera combination. It is clearly noted that the antibacterial effect of aloevera has been enhanced by the addition of other antimicrobials i.e. chitosan and turmeric. In non-aloevera combination i.e. chitosan and turmeric, the interactions between chitosan / turmeric and the functional groups (OH, COOH, NH2) of fibers may be weak and so its antibacterial effect is lesser than aloevera combination. Generally fibers treated with supramolecular compounds such as aloevera, they achieve new functional properties by the selective inclusion of other chemical species into the fiber - fixed cavities (pores or binding sites) . Furthermore the complexes substances may be released from the substrate in a special dosage depending on the surrounding conditions. In aloevera combination, the sorbed chitosan, which is rich in protonated amino groups increases the attractive forces to nucleophiles and enhanced their uptake by fibers. Also the amino acids present in the aloevera form salt linkages with functional groups in the fibers and increase the uptake of the other antimicrobials into the fiber matrix by ionic interaction and hydrogen bonding. The charged state of the new functional groups attacks the cell wall of the bacteria and reduces the microbial growth (19). These lead to maximum exhaustion of antimicrobials and improve their antimicrobial activity.
It is that observed that compared to untreated fibers the pretreated fibers shown better antimicrobial activity since pretreatment leads to increase in the hydrophilic nature of the fiber surface and increased swelling in water(20). This results in the removal of diffusion barrier of the fiber surface and increases the exhaustion of the antimicrobials inside the fiber as well as coating on fiber surface (as seen in Figure 1). This leads to durable antimicrobial finishing to the fibers.

Antifungal activity of finished samples with pretreatment

Table 4 shows the fungal observations in cotton, wool and rabbit hair which are treated with three natural antimicrobials alone and in combination. Among three antimicrobials, aloevera shows better antifungal effect in protein fiber than cotton fibers. The antifungal property on theses materials is also similar to those of an antibacterial property. The antimicrobial agents have phenolic groups (aloevera and turmeric) and anthroquinone groups (aloevera) that have the property of binding microbial proteins, thus inhibiting their growth and so exhibit both antibacterial and antifungal activity (21,22) . The antifungal effect of aloevera both in cotton and protein fiber has been enhanced by the addition of other antimicrobials i.e. chitosan and turmeric, while other combination i.e. chitosan and turmeric shows lesser antifungal effect.

Antimicrobial activity of finished samples with respect to laundering

From the results in table 3 and 4, it is noted that combined application of three antimicrobial agents have better antimicrobial activity than other combinations. So that combination is applied to these three fibers and the durability of the finishing with respect to laundering is assessed. Table 5 and 6 show the effect of washings on antimicrobial assessment in terms of bacterial as well as fungal observations on three fiber substrates that are finished with three antimicrobial agents in combination. It is observed that there are no bacteria as well as fungal growth in the finished fibers up to 20 washings and after 25 washings there is very less bacteria observed in protein fibers and fungi in cotton fibers.

CONCLUSIONS

From the studies based on the applications of anti-microbial agents on cotton fabric, wool fiber and Angora rabbit hair, the following conclusions are achieved.
For the effective results, pre treatments on the cotton fabric, wool fiber and Angora rabbit hair are necessary to achieve good anti microbial effects.
Natural anti-microbial agents, Aloe Vera, Chitosan and Turmeric, are well effective on cotton fabric, wool fiber and Angora rabbit hair.
These natural anti-microbial agents provide higher effectiveness when applied in combinations.
The anti microbial effect on the cotton and protein fibers applied with combination of anti microbial agents (Aloe Vera, Chitosan and Turmeric) is durable even after twenty washes.

ACKNOWLEDGEMENT

Authors are thankful to Dr. R.Ruthramoorthy, Principal, and Dr. M.Kumaravel, Head, Department of Chemistry, PSG College of Technology, Coimbatore for their encouragement and permission to present this article. Authors also thankful to Omega Ecotech Products India Pvt. Ltd., for antimicrobial assessment and Director Central Marine Fisheries Research Institute, Kochi-682 018 for supply of chitosan.

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