WO2018011822A1

WO2018011822A1 - An anti-microbial fabric impregnated with the conjugate of silver nano particles and aloe vera colloidal solution and a method of producing same

Info

Publication number: WO2018011822A1
Application number: PCT/IN2017/050279
Authority: WO
Inventors: Madhuri Sharon; Chinmay PHADKE
Original assignee: Shri A.P.D. Jain Pathashala (Trust)
Priority date: 2016-07-09
Filing date: 2017-07-07
Publication date: 2018-01-18

Abstract

The invention relates to an anti-microbial fabric impregnated with a conjugate of silver nano particles and Aloe vera (AgNP+Aloe) colloidal solution having anti-microbial property and size of 15-20nm made by synthesizing 2.5 mL of 30% ammonia solution was added to 5 mL of 10-2 M AgNO3 solution followed by addition of 5 Ml of the Aloe vera extract and a method of producing antimicrobial silver nano-particle and Aloe vera conjugated multi-purpose nano-fabric. The said method comprises steps of: a) preparation of Aloe vera gel extract and preparing required dilution with pure water; b) addition of silver nitrate stock to gel extract of step (a) for synthesis of silver nano particles (SNP); c) visual observation of color change to confirm completion of reaction in step (b); d) selecting desired shape of spherical monodispersed colloidal SNP-aloe having more active facets (electron dense facets) and strongest biocidal action and size of silver nanoparticles ranges from 20 – 40 nm. e) making visual, spectrophotometric & XRD characterization of synthesized SNP- aloe for synthesis of silver nanoparticles confirmed by its yellow colour formation; f) confirming the formation of silver nanoparticles by UV-Vis spectrophotometric characterization of SNP- aloe; g) coating SNP- aloe on desired fabric such as fabrics coated are cotton (a plant derived fabric), silk (an animal fabric) and polyester (a synthetic fabric).

Description

TITLE :-

"AN ANTI-MICROBIAL FABRIC IMPREGNATED WITH THE CONJUGATE OF SILVER NANO PARTICLES AND ALOE VERA COLLOIDAL SOLUTION AND A METHOD OF PRODUCING SAME"

FIELD OF THE INVENTION:-

The invention relates to a conjugate of silver nanoparticles and Aloe vera (AgNP+Aloe) having anti-microbial property, approximately of size 15-20nm. More particularly, the present invention is a conjugate to be coated onto cotton, silk and polyester fabric making the fabric anti-microbial and also method of producing fabric impregnated with the conjugate of silver nanoparticles and Aloe vera.

BACKGROUND OF THE INVENTION:-

A microorganism is an unicellular organism that lives in water, soil, hot springs, on the ocean floor, high in the atmosphere and deep inside rocks within the Earth's crust. Microorganisms are closely associated with health and welfare of human beings. They can cause skin infection through cuts, burns and wounds.

Ionic silver has a long history of use in treating wounds especially burn wounds. Moreover, silver sulfadiazine has been in use as an effective agent in the treatment of wounds that can be more effectively replaced by silver nanoparticle impregnated fabrics.

The question is why nanoparticles instead of silver ions? It is because, at nano-scale materials display unique properties, which bulk materials, do not. One of them is anti-microbial activity. Nanoparticles are already in use for clothing, food storage containers, filters, surgical instruments and consumer goods. The US Food and Drug Administration have also approved the use of a range of different silver-impregnated wound dressing fabrics. Silver nanoparticles are known to kill microbes by lysis as well as hampering the respiration of microbial cells.

The antimicrobial properties of silver have been known for thousands of years. Recently, silver nanoparticles have gained attention because of their antimicrobial activity which offers the possibility of their use for medical and hygiene purposes. Silver nanoparticles in different formulations and with different shapes and sizes exhibit variable antimicrobial activity that is due to its capability to enter the cells, inactivate the protein, even intercalate between the purine and pyrimidine base pairs of DNA; thus disrupting the hydrogen bonding between the two anti-parallel strands and denaturing the DNA molecule. Moreover, silver nanoparticles exhibit antimicrobial activity against both gram positive and gram negative microbes.

Next consideration is why Aloe vera extract coated silver nanoparticles? Aloe leaf's colourless gel and exudates have been used therapeutically since sixteenth century. Even now this gel is used in medicine and cosmetics as anti-wrinkle creams, moisturizers, sun-screens, hair care products, wound healing, treatments of burns, frostbites, inflammation etc. The Aloe gel is composed of water 99% of the fresh weight of dry weight of the gel 25% are monosaccharide and polysaccharides as well as twenty of the twenty two essential amino acids, enzymes, lectin, lipids, minerals (calcium, magnesium, potassium and sodium all in significant quantities), lactates & salicylates, phenolics and 8 of the 13 recognized vitamins.

The present work pertains to fabric impregnated with biogenically synthesized silver nano-particles using Aloe vera extract. The nano particles are coated with the skin rejuvenating chemicals of Aloe vera. Hence it is more effective in treating and healing burn wounds and skin infections.

PRIOR ART:-

Silver has long history of being used as a healing and anti-bacterial agent by civilizations throughout the world. Long before the development of modern pharmaceuticals, silver was employed as a germicide and antibiotic. Silver nitrate is well known germicides, antiseptics and disinfectants (Luisa Filipponi and Dunan Sutherland, 2010). Silver ions inhibit bacterial growth, suppress respiration and metabolism and induce cell death. Silver toxicity has been shown towards many strains of bacteria, both gram negative and gram positive (Thakur et al. 2013). However, silver is not considered toxic to cardiovascular, nervous or reproductive systems in humans. There are patents declaring silver-coated nano fibers/ fabrics used in filtration system for pathogen removal (Patent by Jin Hu). There are many patents related to synthesis of silver NP and its various other applications. There are no documents found to show an anti-microbial fabric impregnated with the conjugate of silver nano particles and Aloe vera colloidal solution and/ or a method of producing same.

With recent advancement in nanotechnology incorporation of silver nano- particles (SNP) and Aloe into numerous consumer products have taken place; because nano particles exhibit higher effectiveness due to their smaller size and higher surface to volume ratio than the larger particles. Moreover, SNP-Aloe has very low toxicity towards mammalian cells. Sharon's group has published an article declaring silver nanoparticles to be antimicrobial (Thakur et al 2013).

Following are a list of publications regarding antimicrobial properties of silver nanoparticles:

1. M. Thakur, S. Pandey, A. Mewada, R. Shah, G. Oza & Madhuri Sharon. Understanding the stability of silver nanoparticles bio- fabricated using Acacia arabica (Babool gum) and its hostile effect on microorganisms. Spectrochimica Acta Part A: Mol.& Biomol. Spectroscopy. 109 (2013) 344-347

2. N. Duran, P.D. Marcato, R. De Conti, O. L. Alves, F. T. M. Costa & M. Brocchi. Potential Use of Silver Nanoparticles on Pathogenic Bacteria, their Toxicity and Possible Mechanisms of Action. J. Braz. Chem. Soc, Vol. 21, No. 6, 949-959, 2010. P. Jain, T. Pradeep Potential of Silver Nanoparticle-Coated Polyurethane Foam as an Antibacterial Water Filter. Published online 18 February 2005 in Wiley InterScience

A S M Raja and G Thilagavathi, T Kannaian. Synthesis of spray dried polyvinyl pyrrolidone coated silver nano powder and its application on wool and cotton for microbial resistance. Indian journal of fibre and textile research Vol.35, March 2010, pp.59-64

Y. Li, P. Leung, L. Yao, Q. W. Song, E. Newton Antimicrobial effect of surgical masks coated with nanoparticles. Journal of Hospital Infection (2006) 62, 58-63

Jun Sung Kim, Eunye Kuk, MS, Kyeong Nam Yu, MS, Jong-Ho Kim, MS, Sung Jin Park, BS, Hu Jang Lee, DVM, PhD, So Hyun Kim. Antimicrobial effects of silver nanoparticles. Nanomedicine: Nanotechnology, Biology, and Medicine 3 (2007) 95- 101

Linda Teufel and Bernhard Red. Improved methods for the investigation of the interaction between textiles and microorganisms. Lenzinger Berichte, 85 (2006), 54-60

Nelson Duran, Priscyla D. Marcato, Gabriel I. H. De Souza, Oswaldo L. Alves, and Elisa Esposito. Antibacterial effect of Silver nanoparticles produced by fungal process on textile fabrics and their effluent treatment. Journal of Biomedical Nanotechnology Vol.3, 203- 208, 2007

P. Gupta, M. Bajpai, and S. K. Bajpai. Investigation of Antibacterial Properties of Silver Nanoparticle-loaded Poly (acrylamide-co-itaconic acid)-Grafted Cotton Fabric. The Journal of Cotton Science 12:280- 286 (2008)

M. Kostic, N. Radio, B.M. Obradovic, S. Dimitrijevic, M. M. Kuraica, P. Skundric. Antimicrobial textile prepared by silver deposition on dielectric barrier discharge treated cotton/polyester fabric. Chemical Industry & Chemical Engineering Quarterly 14 (4) 219-221 (2008) DISADVANTAGES OF PRIOR ART:

Most of the application of silver nanoparticles coated fabric is for making nasal masks.

There are many Chinese companies manufacturing silver nano particles coated mask, declaring it to be antimicrobial mask.

Though it is a fact that silver nanoparticles are antimicrobial, but for that an exposure period is required. Whereas when human beings inhale through silver NP coated mask, microbes come in contact with nano silver for a very short duration, which is not enough to kill microbes. Hence these masks are not effective.

To use silver NP coated fabric it is important that these fabrics should be used for the applications where it comes in contact with these microbes for at least 20 minutes.

Most of the Silver nano-particles synthesis is by chemical methods, which may have residual chemicals, thus making it non-biocompatible. When human skin cells grown in a Petri dish were exposed to nano-silver particles 7-20 nm in size, concentration-dependent changes to cell morphology including abnormal size, shrinkage and rounded appearance were observed at concentrations above 6.25 μg/mL. Another paper describes the result of exposure to nano silver in a wound dressing used to treat a severe burn victim. After a week of treatment with a wound dressing impregnated with nanosilver, the patient developed reversible signs of liver toxicity and a grayish discoloration of his face similar to that found in patients diagnosed with argyria (Environmental Impacts of Nanosilver, Kristen M. Kulinowski).

Moreover, if they are used for killing microbes that infect through human skin it may harm the normal cells of the skin. So it is better to synthesize silver NP biogenically as they will be more biocompatible as compared to chemically synthesized silver NP. There is no nano silver coated antimicrobial fabric that has any skin rejuvenating molecules attached to it. Hence, after killing the microbes lodged onto the skin it is desirable to provide assistance to skin recovery.

OBJECT OF THE INVENTION:-

It an object of the present invention to create an anti-microbial fabric impregnated with the conjugate of silver nano particles and Aloe vera colloidal solution and a method of producing same.

It is another object of the present invention to provide a method of producing antimicrobial silver nano-particle and Aloe vera conjugated multi-purpose nano-fabric biogenically as they will be more biocompatible.

STATEMENT OF THE INVENTION:-

Accordingly, the present invention provides an anti-microbial fabric impregnated with the conjugate of silver nano particles and Aloe vera, made by coating the silver nano particles and Aloe vera colloidal solution wherein the preferred fabric is either cotton (cellulose) or silk or polyester etc.

Accordingly, the present invention provides a conjugate of silver nanoparticles and Aloe vera (AgNP+Aloe) colloidal solution having antimicrobial property and size of 15-20nm made by synthesizing 2.5 mL of 30% ammonia solution was added to 5 mL of 10-2 M AgNO3 solution followed by addition of 5 ml of the Aloe vera extract.

The invention also provides a method of producing anti-microbial fabric that comprises steps of:

a. preparation of Aloe vera gel extract and preparing required dilution with pure water; b. preparation of 10^"2 M Silver Nitrate (AgNO₃) Stock solution, that was further diluted to form different concentrations ranging from 100 - 500 ppm of silver;

c. adding of the said Silver Nitrate Stock of step (b) with 30% ammonia to the said gel extract of step (a) for synthesizing;

d. the said concentration of AgNO₃ adjusted to 10^"3 M by making up the final volume to 50 imL with water;

e. visual observation of color change in step (c) to confirm completion of reaction in step (b);

f. selecting desired shape of spherical mono dispersed colloidal SNP-aloe having more active facets (electron dense facets) and strongest biocidal action and size of silver nanoparticles that ranges from 20 - 40 nm;

g. making visual, spectrophotometric & XRD characterization of synthesized SNP- aloe for synthesis of silver nanoparticles confirmed by its yellow colour formation;

h. confirming the formation of silver nanoparticles by UV-Vis spectrophotometric characterization of SNP- aloe;

i. the testing in steps (f), (g) and (h) makes product conjugate silver nano Aloe vera colloidal solution ready for acceptable.

j. coating of the said conjugate silver nano Aloe vera solution of step (i) on desired fabric preferably cotton (a plant derived fabric) or silk (an animal fabric) or polyester (a synthetic fabric).

REFERENCE TO DRAWINGS:-

The invention is described with reference to accompanying drawing wherein: Figure 1 shows visual observation of synthesized SNP- aloe;

Figure 2 shows UV-Vis spectrophotometric characterization of SNP- aloe;

Figure 3 shows XRD analysis of SNP- aloe;

Figure 4 shows Table 1 ; Figure 5 shows TEM image of 10-20 nm SNP;

Figure 6 demonstrates biocidal activity of different concentrations of SN;

Figure 7 demonstrates biocidal activity of SNP-Aloe fabrics (Silk, Polyester, & Cotton);

Figure 8 demonstrates biocidal activity of SNP-Aloe fabrics (Silk, Polyester, & Cotton against Klebsiella pneumoniae, as tested by KIRBY BAUER METHOD;

Figure - 9 shows below demonstrates Biocidal activity of SNP-Aloe fabrics (Silk, Polyester, & Cotton) against S. aureus as tested by KIRBY BAUER METHOD;

Figure - 10 shows FTIR spectrum of AgNP + Aloe;

Figure - 1 1 shows AgNP+Aloe coated (A) Hosiery fabric & (B) Bandage fabric.

Both showing (as indicated by arrow) silver nanoparticles (AgNP+Aloe)

Figure 12 shows Graphical presentation of formation of AgNP+Aloe ;

Figure 13 shows formula of Possible Mechanism of biosynthesis of

AgNP+Aloe through quinones present in fresh Aloe vera leaf extract.

DESCRIPTION OF THE INVENTION:-

A conjugate of Silver nanoparticles and Aloe vera (AgNP+Aloe) having antimicrobial property and size of 15-20nm.

The antimicrobial AgNP+Aloe is yellow colloidal solution (Figure 1 ). The intensity of yellow color increased with increase in concentration of silver nanoparticles. Its morphology and size were determined by UV-Vis Spectrophotometer (Figure 2) and HRTEM (High Resolution Transmission electron microscopy) (Figure 5). Synthesis of silver nano particle was further confirmed by XRD (X-Ray Diffraction) analysis (Figure 3).

Another aspect of the present invention is that this conjugate can be coated onto Cotton, Silk and Polyester fabric making the fabric anti microbial (Table 1 ). The most suitable fabric was found to be cotton (cellulose); as it could inhibit the maximum growth of both gram positive and gram negative pathogenic bacteria.

METHOD OF MAKING AgNP+Aloe

A novel method of unique biogenic synthesis of AgNP+Aloe was used, which was as follows:

For the synthesis of silver nanoparticles, 2.5 mL of 30% ammonia solution was added to 5 mL of 10-2 M AgNO3 solution followed by addition of 5 Ml of the Aloe Vera extract.

The concentration of AgNO₃ was adjusted to 10^"3 M by making up the final volume to 50 mL with water

First step:

a. preparation of Aloe vera gel extract {Aloe vera is a cosmetical herb that contains an array of chemicals for healthy skin and is known to have skin rejuvenating property) with pure water;

b. preparation of 10^"2 M Silver Nitrate (AgNOa) Stock solution, that was further diluted to form different concentrations ranging from 100 - 500 ppm of silver;

c. addition of Silver Nitrate Stock 30% ammonia to gel extract;

d. the concentration of AgNO₃ was adjusted to 10^"3 M by adding require volume of pure water;

e. visual observation of color change is noted to confirm completion of reaction; f. thus synthesized of spherical mono dispersed colloidal AgNP+Aloe has shape-dependent interaction with the bacterial cells.

g. the nanoparticles of desired shape having more active facets (electron dense facets ) and strongest biocidal action are selected. h. the size of silver nanoparticles ranges from 15 - 20 nm. The antibacterial activity is size dependent. Smaller particles exhibit enhanced antimicrobial activity than larger particles. Because, smaller nano particles have large surface to volume ratio, hence increased antibacterial activity (Figure 12).

Second Step:

This step was to confirm and characterize the product.

• Visual observation: Synthesis of silver nanoparticles was confirmed visually by its yellow colour formation. (Figurel )..

• UV-Vis Spectrophotometric characterization: is done to confirm the formation of silver nanoparticles. The peak of silver nanoparticles of 100ppm - 400 ppm was obtained at 420 nm which indicates silver nanoparticles. An intense absorption peak was obtained at 405 nm of 500 ppm silver nanoparticles which indicates the presence of spherical or roughly spherical silver nanoparticles. According to UV- vis spectrophotometric analysis use of 500 ppm showed best nanoparticle formation. (Figure 2)

• High Resolution Transmission Electron Microscopy: was done to see the morphology of the product (Figure 5)

• X-ray Diffraction (XRD) Analysis: the XRD patterns of the sample shown in Fig.3 shows a peak at 38 confirms silver nanoparticle formation; as for silver nano particle diffraction angle [2Θ in degree] is 38,

• FT-IR analysis - Fourier transforms infrared spectroscopy analysis: is done for identification of biomolecules present in the synthesized Ag nanoparticles. FTIR spectra peaks at 3435.58 cm-1 , 3099.36 cm-1 , 2778.24 cm-1 , 1701 .39 cm-1 , 1376.24 cm-1 , 546.55 cm-1 and confirm the presence of different Functional groups like Alcohol (O-H), Amine (-NH-), Alkene (=C-H, - C=C), Alkane (-C-H), and Carbonyl (-C=O). This functional groups confirm the presence of protein (Amino Acid) that are responsible for the bioreduction of Ag+ ion as well as stabilization of nanoparticles. Moreover it suggests that the biological molecules have coated the silver nanoparticles. (Figure 10)

Possible Mechanism of biosynthesis of AgNP+Aloe through quinones present in fresh Aloe vera leaf extract shown in figure 13.

Third Step:

• This invention provides a method of coating AgNP+Aloe on desired fabric

• Fabrics coated are Cotton (a plant derived fabric), Silk (an animal fabric) and Polyester (a synthetic fabric),

• Coating of AgNP+Aloe on fabric can be done by either

(i) Spray Method i.e. spraying a known concentration of AgNP+Aloe on the desired fabric and drying the fabric at 50 - 90°C

or

(ii) Dip Method where fabric is dipped in a known concentration of AgNP+Aloe for known time followed by drying at 50 - 90°C.

• Coating of AgNP+Aloe on fabric was confirmed by SEM (Figure 1 1 )

Fourth Step:

Antimicrobial testing of AgNP+Aloe coated fabric

• Antimicrobial activity of AgNP+Aloe & AgNP+Aloe -coated fabric was confirmed by exposing microbial cultures of different microbes grown on specific media; using (i) Standard agar-well technique in this method, the microorganism is grown on agar plate having a well in the centre. To these wells SNP is added which diffuses through the depth of agar and inhibits the growth of microorganisms and a zone of inhibition is obtained. This method is used to find out the concentration of silver nanoparticles that is susceptible to microorganisms and

(ii) Disk diffusion method (Kirby Bauer Method), in this method silver nanoparticle is absorbed on the surface of agar seeded with microorganism. This method is used to check the efficacy of AgNP+Aloe coated fabric against particular microorganism.

Microbes tested were 8 skin infecting microbes i.e. Staphylococcus aureus, Streptococcus pyogenes, Micrococcus spp., Corynebacterium sp. Pseudomonas aeruginosa, Pasteurell multocida, Capnocytophaga canimorsus, Bartonella sp., Klebsiella rhinoscleromatis, and Vibrio vulnificus as well as 5 other pathogenic microbes - Corynebacterium diphtheria, Eschericia coli, Klebsiella pneumoniae, Mycobacterium tuberculosis and Salmonella typhi. (Figure 6, 7, 8, 9)

Cultures of these microbes were maintained under aseptic conditions.

Microbes were cultured on Nutrient broth: having following composition:

Peptone 1 g/l

NaCI 0.5g/l

Beef extract 0.3g/l

pH set at 7.4

0.26g nutrient broth was dissolved in 20ml D/W

Sub-culturing was carried out by inoculating loopful of culture in 20ml nutrient broth and was incubated at 37^Qc for 24 hrs.

Testing antimicrobial activity of silver nanoparticles coated fabrics by Kirby Bauer method (Disk Diffusion Method)

0.1 ml of test microorganisms was plated on nutrient agar. 2cm² of test (silver coated) fabric and control fabrics placed and gently pressed on the agar plate.

It was incubated at 37 °c for 24 hrs.

The zone of inhibition was recorded after 24 hours.

The antimicrobial activity test are presented in figures 6 to 9.

Figure 5 demonstrates TEM images of silver nanoparticles. According to TEM analysis the silver nanoparticle found to be 10-20 nm. This image shows no agglomeration of silver nanoparticles.

Figure 6 demonstrates Biocidal activity of different concentrations of

SNP.

Figure 7 demonstrates biocidal activity of SNP-Aloe fabrics (Silk, Polyester, & Cotton) against E. coli as tested by KIRBY BAUER METHOD.

Figure 8 demonstrates biocidal activity of SNP-Aloe fabrics (Silk, Polyester, & Cotton,) against Klebsiella pneumoniae, as tested by KIRBY BAUER METHOD.

Figure 9 below demonstrates Biocidal activity of SNP-Aloe fabrics (Silk, Polyester, & Cotton) against S. aureus as tested by KIRBY BAUER METHOD.

Figure 10 shows FTIR spectrum of AgNP + Aloe. It is done for identification of biomolecules from Aloe vera present in the synthesized Ag nanoparticles. FTIR spectra shows 6 peaks at 3435.58 cm-1 ,

3099.36 cm-1 ,

2778.24 cm-1 ,

1701 .39 cm-1 ,

1376.24 cm-1 &

546.55 cm-1

These peaks indicate presence of different Functional Groups like Alcohol (O-H),

Amine (-NH-),

Alkene (=C-H), Alkene (- C=C),

Alkane (-C-H), &

Carbonyl (-C=O) respectively.

These functional groups confirm the presence of protein (Amino Acid) that are responsible for the bio-reduction of Ag+ ion as well as stabilization of nanoparticles. Moreover it suggests that the biological molecules have coated the silver nanoparticles.

• Figure - 1 1 shows SEM of AgNP+Aloe coated fibers of

(A) Hosiery fabric &

(B) Bandage fabric.

Presence of silver nanoparticles (AgNP+Aloe)

on the fibers are indicated by arrows silver nanoparticles

• Figure 12 shows Graphical presentation of formation of AgNP+Aloe .

The yellow coloured spherical structure depicts silver nanoparticle; to which various molecules of functional groups are attached

• Figure 13 shows formula of Possible Mechanism of biosynthesis of AgNP+Aloe through reducing agents present in fresh Aloe vera leaf extract.

EXAMPLES OF THE INVENTION:-

The present invention is further illustrated by the following specific examples. The examples are provided for illustration only and should not be construed as limiting the scope of the invention in any way.

Example: 1

Biosynthesis of Silver nanoparticles:

In a typical biosynthesis production scheme of silver nanoparticles according to the present invention, 10 ml of the Aloe vera leaf extract (prepared in a ratio of 1 :1 ) was further diluted and the final volume was made up to 20 ml. The mixture was then boiled for a while. 100 μΙ of 50,000 ppm silver nitrate solution was added to the boiling extract. Color change was observed within few minutes, which preliminarily indicated the synthesis of SNP-Aloe.

Example: 2

Characterization of SNP-Aloe:

Optical spectroscopy has been widely used for the characterization of nano- materials. In the examples described herein, two different spectroscopy techniques were used to fully characterize the silver nanoparticles produced. They include UV visible spectroscopy (see e.g., FIG.2), and FTIR (see e.g., FIG. Y). The UV-Vis spectroscopic measurements were recorded on a Shimadzu dual-beam spectrophotometer. The UV absorbance peak was observed at 405 nm.

In order to perform FTIR studies of the results, films of nanoparticles were produced with KBr pellets (HPLC grade) in 1 :100 ratio. The FTIR system used was a Perkin Elmer instrument. In addition, the spectrum showed the presence of active biomolecules in the plant extract of Aloe vera this confirms the synthesis of silver nanoparticles.

The X-ray diffraction analysis pattern (XRD) of the product of the reaction of silver nitrate solution with the Aloe vera extract, shown in FIG. 3, confirms the crystalline nature of the SNPs synthesized according to the method described in Example 1 . The XRD analysis pattern indicates characteristic peak at 2 theta (in degrees) values of 38.

Transmission Electron Microscopy (TEM) images of the product of the reaction of silver nitrate solution with the Aloe vera extract were obtained to further confirm synthesis of the silver nanoparticles, which were exhibited as individual silver particles and also a number of aggregates. A TEM image is shown in FIG. 5. The morphology of the nanoparticles observed was variable. Spherical shapes ranging from around 10-20 nm were observed.

WORKING OF THE INVENTION:- PREPARATION OF ALOE LEAF EXTRACT -

To prepare the leaf extract, 100 gm of aloe leaf pulp was crushed using mortar and pestle and 100 ml distilled water was added to it. The crushed extract was filtered through two layers of muslin cloth and centrifuged at 3000 rpm for 5 minutes. The supernatant was taken as plant extract

SYNTHESIS OF SNP -

• To 10ml of aloe leaf extract (prepared as mentioned above) 10ml of distilled water was added and was then boiled for 1 min.

• 100μΙ of 50,000 ppm AgNO₃ solution was added to the boiling extract.

• Boiling was continued till the color of reactant changed to brown i.e.

Approximately after 5 minutes of the reaction due to the production of SNPs.

FABRIC COATING METHOD

Various methods of coating nanoparticles onto fabric have been tried. The principal behind the coating is that SNPs can bind covalently with the proteins and functional groups of natural fabrics such as it binds to cytokinin binding protein of cotton and keratin of silk; whereas in synthetic fabric it binds to the ester group of polyester. The best method of working is as follows:-

^■ Fabrics to be coated were soaked for 15 minutes in 500ppm SNP-Aloe solution.

^■ These fabrics are then air dried at 60^QC for 10 minutes.

^■ The dried fabrics were washed thrice with distilled water to remove any unbound SNP before the final drying.

^■ The washed fabrics were finally air dried at 60^QC and ready for application.

ANTI-MICROBIAL ACTIVITY STUDY METHODS

1 . The anti-microbial activity study of the SNP-Aloe was done by a universally recognized method: Agar-Well Method. ¹ 0.1 ml of microorganism is added in cool molten agar based media, poured in the petri-dish and culture was allowed to solidify.

^■ Small well is bored in the centre of agar plate and filled with 100 μΙ of SNP solution.

¹ The culture was then incubated at 37 °c for 16 hrs.

^■ The SNP diffuses through the depth of agar and the zone of inhibition, due to microbial death is formed.

^■ This method was used to find out the desired concentration of SNP to be loaded onto fabrics.

The anti-microbial activity study of the SNP-Aloe coated fabrics was done by a universally recognized method: Disc Diffusion (Kirby Bauer) method.

^■ In this method 2cm² of test and control fabrics was placed on the surface of nutrient agar plate (seeded with 0.1 ml of test microorganism) and gently pressed.

^■ Plate was incubated at 37 °c for 24 hrs and the zone of inhibition was measured.

Claims

WE CLAIM:-

1 . An anti-microbial fabric impregnated with the conjugate of silver nanoparticles and aloe vera made by coating the said silver nano particles and aloe vera colloidal solution.

2. An anti-microbial fabric impregnated with the conjugate of silver nanoparticles and aloe vera made by coating the said silver nano particles and Aloe vera colloidal solution as claimed in claim 1 ; wherein a conjugate of Silver nanoparticles and Aloe vera (AgNP+Aloe) colloidal solution having anti-microbial property and size of 15-20nm is made by synthesizing 2.5 imL of 30% ammonia solution and addition to 5 imL of 10-2 M AgNO3 solution further followed by addition of 5 imL of the Aloe vera extract.

3. An anti-microbial fabric impregnated with the conjugate of silver nanoparticles and aloe vera made by coating the said silver nano particles and Aloe vera colloidal solution as claimed in claim 1 ; wherein the said fabric is either cotton (cellulose) or silk or polyester.

4. A method of producing antimicrobial silver nano-particle and aloe vera conjugated colloidal solution as claimed in claim 1 , 2 and 3 comprising steps:

a. preparation of Aloe vera gel extract and preparing required dilution with pure water;

b. preparation of 10^"2 M silver nitrate (AgNO₃) stock solution and diluting it to form different concentrations ranging from 100 - 500 ppm of silver;

c. adding of the said silver nitrate stock of step (b) with 30% ammonia to the said gel gel extract of step (a) for synthesysing; d. the said concentration of AgNO3 adjusted to 10^"3 M by making up the final volume to 50 imL with water;

e. visual observation of color change in step (c) to confirm completion of reaction in step (b); f. selecting desired shape of spherical monodispersed colloidal SNP-aloe having more active facets (electron dense facets) and strongest biocidal action and size of silver nanoparticles ranges from 20 - 40 nm;

h. confirming the formation of silver nanoparticles by UV-Vis spectrophotometric characterization of SNP- Aloe.

The method of producing colloidal solution as claimed in claim 4, wherein extraction of aloe vera is done from 100 gm of aloe leaf by crushing the aloe leaf using mortar and pestle and adding 100 ml distilled water to it; filtering extract through two layers of muslin cloth and centrifuging at 3000 rpm for 5 minutes; and taking supernatant as plant extract.

The method of producing colloidal solution as claimed in claims 4 and 5, by carrying out silver nano particle synthesis comprising steps:

I. adding of 10 ml of aloe leaf with 10ml of distilled water;

II. boiling for 1 minute aloe leaf extract in step (I) ;

III. adding of 100μΙ of 50,000 ppm AgNO₃ solution to the boiling extract of step (II);

IV. continuing the boiling in step (III) till changing of the color of reactant to brown.

A method of producing anti-microbial fabric as claimed in claim 1 ,2 and 3 comprising steps:

b. preparation of 10^"2 M silver nitrate (AgNOa) stock solution and diluting it to form different concentrations ranging from 100 - 500 ppm of silver;

c. adding of the silver nitrate stock of step (b) with 30% ammonia to the gel extract of step (a) for synthesizing; d. the concentration of AgNO3 adjusted to 10^"3 M by making up the final volume to 50 imL with water;

f. selecting desired shape of spherical monodispersed colloidal SNP-aloe having more active facets (electron dense facets) and strongest biocidal action and size of silver nanoparticles ranging from 20 - 40 nm;

g. making visual, spectrophotometric & XRD characterization of synthesized SNP- Aloe for synthesis of silver nanoparticles confirming its yellow colour formation;

i. carrying out the test to confirm formation of conjugate silver nano Aloe vera colloidal solution;

k. coating of the said conjugate silver nano Aloe vera solution of step (i) on desired fabric such as cotton (a plant derived fabric), silk (an animal fabric) and polyester (a synthetic fabric).

8. The method of producing anti-microbial fabric as claimed in claim 7, wherein coating SNP- aloe on fabric is by spraying a colloidal solution on the desired fabric and drying the fabric at 50 - 90°C, confirming the coating by FTIR.

9. The method of producing nano-fabric as claimed in claims 7, wherein coating SNP-aloe on fabric is by dipping in SNP-aloe colloidal solution for 1 - 10 min followed by drying at 50 - 90°C and confirming the coating by FTIR.

10. The method of producing nano-fabric as claimed in claim 7, wherein the said dip coating comprising of steps:- i. soaking fabrics to be coated for 1 - 10 min minutes in 500ppm SNP-Aloe solution; air drying the said soaked fabrics at 60^QC for 10-20 minutes;

washing the said dried fabrics with distilled water to remove any unbound SNP before the final drying;

air drying the washed fabrics at 60^QC.