Description:TECHNICAL FIELD
The present invention relates to medical field. The present invention aims to provide a bilayered wound dressing material. More specifically, the invention provides a bilayered wound dressing material comprising a layer of synergistic a wound palliating composition on a substrate. The composition comprises extract of Centella asiatica, colloidal Silver, fibroin and a base. The invention also relates to a method preparation of the composition and its application as on to a substrate. The synergistic composition is applied in the form of froth on to the substrate to beget bilayered wound dressing material.
BACKGROUND AND PRIOR ART
It is ubiquitously known that wound dressing materials aid in protection and palliating wounds. Various types of wound dressings are known in the art like bandage, gauze either per se or supplemented with medicated gels, hydrocolloids, foams, and films. The medicated wound dressings provide the benefit of faster wound healing, better exudation and protection.
The patent document US 6,326,410 informs about a polyurethane foam that can be adopted in wound dressing. The polyurethane foam is used as a layer in the wound dressings, however the disclosed invention is very complex in its preparation due to involvement of many reagents. Another patent document US 11,730,854 relates to polyurethane material loaded with antimicrobial material Silver metal/ions that can be uses as a wound dressing material. The invention focusses on the addition of only Silver during the preparation of the polyurethane foam and thus is restricting in terms of the antimicrobial activity. The Indian patent application IN1737/DELNP/2005 discloses a polyurethane foam dressing for a wound filler, which includes a hydrophilic foam containing a plurality of open cells with a diameter of 50 to 400 microns and a plurality of pores with a diameter of 10 to 80 microns. According to the disclosure, the foam is produced by mixing and agitating a pre-polymer, foaming agent, crosslinking agent, injecting the resulting mixture into a mold, and foaming the mixture while it is injected into the mold.
The literature documents suggest usage of Centella Asiatica and fibroin in wound healing. A. Shukla et in Journal of Ethnopharmacology 65 (1999) 1–1 titled “In vitro and in vivo wound healing activity of asiaticoside isolated from Centella asiatica” informs about usage of Centella asiatica for wound healing. Lorenz Meinel in Biomaterials 26 (2005) 147–155 titled “The inflammatory responses to silk films in vitro and in vivo” discuss about the usage of silk films in wound healing.
The present invention aims to provide a bilayered wound dressing material wherein a wound palliating composition is adopted in the form of froth on a substrate.
SUMMARY OF INVENTION
Accordingly the present invention provides a bilayered wound dressing material comprising-
- froth form of wound palliating composition consisting extract of Centella asiatica, colloidal silver, Fibroin and a base; and
-a hydrophilic porous substrate.
A method of preparation of bilayered wound dressing material comprising- froth form of a wound palliating composition consisting of extract of Centella asiatica, colloidal silver, Fibroin and a base as foam; and a substrate- said method comprising acts of
a) preparing a solution of the base in water;
b) adding extract of Centella asiatica, colloidal Silver, Fibroin to the solution of base to obtain the suspension of wound palliating composition;
c) preparing froth form of the solution of the wound palliating composition;
d) coating the froth form of the composition on a substrate; and
e) drying to obtain the bilayered film.

BRIEF DESCRIPTION OF FIGURES
The features of the present invention can be understood in detail with the aid of
appended figures. It is to be noted however, that the appended figures illustrate only
typical embodiments of this invention and are therefore not to be considered limiting
of its scope for the invention.
Figure 1: illustrates the leaching of materials from a. Coated foam, b. Uncoated foam.
Figure 2: illustrates coating to get an uniform layer a. Froth coated foam, b. Film coated foam. Film coated layer requires double quantity of coating material to that of froth coated foam.
Figure 3: illustrates coating with equal amount of coating material (a). Froth coated foam, (b). Film coated foam.
Figure 4: illustrates (a). Froth Coated foam, (b). Film coated foam, Froth coating provides higher adsorption in to wet surface compared to film coated at 1 min and 30 minutes.
Figure 5: illustrates depictive picture of the leaching of medicaments on to bovine skin. a). Sample + Bovine skin; b). Sample placed on bovine skin; c). Leaching of medicaments after placing it on bovine skin.
DETAILED DESCRIPTION OF INVENTION
The foregoing description of the invention has been presented for the purpose of illustration. The embodiments described are not intended to be exhaustive or to limit the invention to the precise form disclosed, as many alternative variations and sequences are possible in light of this disclosure for a person skilled in the art in view of the figures and description. Additional features and advantages of the disclosure will be described hereinafter which form the focus of the description of the disclosure. It may further be noted that as used herein, the singular “a” “an” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by a person skilled in the art.
The present invention relates to a bilayered wound dressing material, comprising a wound palliating composition on a substrate.
In an embodiment of the present invention, the wound palliating composition comprises extract of Centella asiatica, colloidal Silver, fibroin and a base.
In another embodiment of present invention the wound palliating composition in suspension form comprises extract of Centella asiatica ranging from 0.4 %wt/wt to 3%wt/wt, colloidal Silver ranging from 0.02 %wt/wt to 0.3%wt/wt, and Fibroin ranging from 0.2 %wt/wt to 4%wt/wt and base is ranging from 14%wt/wt to 15%wt/wt which is coated on a Foam and dried to obtain double layered foam with wound contact layer comprising 2 %wt/wt to 15%wt/wt extract of Centella asiatica, 0.1 %wt/wt to 1.5%wt/wt of colloidal Silver , and 1 %wt/wt to 20%wt/wt of Fibroin and base is ranging from 70%wt/wt to 90%wt/wt.
The bilayered wound dressing material, wherein the composition in dry form on the bilayered wound dressing material comprises extract of Centella asiatica ranging from 6% w/w to 12.9% w/w, colloidal Silver ranging from 0.5% w/w to 1.2% w/w and Fibroin ranging from 3.5% w/w to 11.3% w/w and base is ranging from 74.4% w/w to 90% w/w.
In an embodiment of present invention, the wound palliating composition of extract of Centella asiatica, colloidal silver, Fibroin and a base as foam is maximum 30% of thickness of the bilayered film.
In an embodiment of the present invention, the base is selected from a group comprising Hydroxypropyl methyl cellulose, Hydroxy propyl cellulose, Polyvinylpyrrolidone (PVP), Polyvinyl alcohol (PVA), Albumin, Acrylate.
In an embodiment of the present invention, the substrate is a polymeric foamy material selected from a group comprising Polyurethane, Cellulose and other composite flexible porous materials.
In another embodiment of present invention, the substrate is Polyurethane foam.
The present invention also relates to a method of preparation of bilayered wound dressing material, comprising a wound palliating composition and a substrate, said method comprising acts of-
a) preparing a solution of a base in water;
b) adding extract of Centella asiatica, colloidal Silver, Fibroin to the solution of base to obtain a suspension of wound palliating composition;
c) preparing froth form of the suspension of the wound palliating composition;
d) coating the froth form of the composition on a substrate; and
e) drying to obtain the bilayered wound dressing material.
In an embodiment of the present invention, the synergistic composition is transformed in to froth form by mechanical milling or high shear homogenization to include the air bubbles and compared with an un-frothed suspension.
In another embodiment of present invention, drying of the wound palliating composition on the substrate is carried out at a temperature ranging from 40-80 °C with or without vacuum.
In another embodiment of present invention, the Specific gravity of froth form coating of suspension ranges from 0.5 to 1.0 and the viscosity ranges from 1800 mPas to 44200 mPas.

EXPERIMENTAL
The materials for the invention were obtained from commercial sources. The colloidal silver is obtained from Nano Research Labs, Jamshedpur Jharkhand. The Centella asiatica extract which is an alcoholic extract is obtained from Natural Remedies, Bangalore, Karnataka.
The fibroin is prepared by following method-
Step 1: Degumming of Cocoon
Bombyx mori bivoltine cocoons obtained from Central Silk Board, Bangalore Karnataka are thoroughly cleaned without any pupa and residuals. The cocoons are taken along with sodium bicarbonate solution and autoclaved at 110oC for 30 minutes. The degummed cocoons are separated, and collected. The degummed cocoons free of Sericin are washed with cold water, and dried in hot air oven at a temperature of 70°C.
Step 2:- Dissolution of Fibroin and desalting
The degummed cocoons are dissolved in a solution of Lithium bromide ( LiBr) in a ratio 1:20 w/w (Cocoon : LiBr) at 60-80oC for 4 hours with continuous stirring. It is desalted using dialysis or ultrafiltration chamber with 20 Kda membrane till the TDS of permeate reaches below 500 ppm. It is then concentrated and used.
Example 1
Step 1: Coating suspension preparation
100 g of Hydroxypropyl methyl cellulose is dissolved in 500 gm of hot water after complete dissolution, 0.6 g of colloidal silver, 3.9 g of Silk Fibroin and 7 g extract of Centella asiatica of added to the above solution under continuous stirring to get a uniform suspension. Finally, the suspension was made up to 1000 g to get the final coating suspension.
Step 2:
Processing: The uniform suspension is then passed though mechanical milling process in homogenizer at 6000 rpm vigorously to incorporate air bubbles to obtain a frothy mass of viscosity of about 13050 mPaS and specific gravity of 0.63.
Step 3:
Coating: The above coating suspension is coated on to a polyurethane to get a uniform coating of 40 mg /cm2 and drying under stream of hot air at a temperature of 60℃ C to get a bilayed foam, wherein 111.5 gram of the dry composition comprises- Base- 90% w/w, Centella asiatica- 6% w/w, Silk Fibroin- 3.5% w/w and Silver- 0.5 % w/w.
Example 2
Step 1:Coating Suspension preparation
100 g of Carboxymethyl cellulose is dissolved in 500gm of hot water, after complete dissolution, 0.6 g of colloidal silver, 3.9 g of Silk Fibroin and 7 g extract of Centella asiatica of added to the above solution under continuous stirring to get a uniform suspension. Finally, the suspension was made up to 1000 g to get the final coating suspension
Step 2: Processing
The uniform suspension is then passed though mechanical milling process in homogenizer at 6000 rpm vigorously to incorporate air bubbles to obtain a frothy mass of viscosity 14500 mPaS and specific gravity of 0.60.
Step 3: Coating
The above coating suspension is coated on to a foam substrate using a doctors scrapper blade to get a uniform coating of 50 mg /cm2 and dried under stream of hot air at a temperature of 70°C to get a bilayred dressing material, wherein 111.5 gram of dry composition comprises Base- 90% w/w, Centella asiatica- 6% w/w, Silk Fibroin- 3.5% w/w and Silver- 0.5 % w/w.
Example 3:
Step 1: Coating solution preparation
80 g Polyvinyl alcohol is dissolved in 500 gm of hot water maintained at a temperature of 80 °C, after complete dissolution, 0.6 g of colloidal silver, 6 g Silk Fibroin and 10 g extract of Centella asiatica are added under continuous stirring and the total suspension was made up to 1000 gms to get a uniform suspension.
Step 2:
Processing: The uniform suspension is then passed though mechanical milling process in homogenizer at 7000 rpm vigorously to incorporate air bubbles to obtain a frothy mass of viscosity of about 13450 mPaS and specific gravity of 0.68.
Step 3:
Coating: The above coating suspension was coated on to a nonwoven substrate using a doctors scrapper blade to get a uniform coating and dried under stream of hot air at a temperature of 65°C to get a bilayed foam, wherein 96.6 gram of dry composition comprises Base: 82.8% w/w, Centella asiatica 10.3% w/w, Silk Fibroin: 6.2% w/w, Silver- 0.6 % w/w.
Example 4:
Coating solution preparation: In an example, Hydroxypropyl methyl cellulose 100 g was dissolved in 600 g hot water at 70 °C, after complete dissolution, colloidal silver of 1.2 g, Silk Fibroin 9.5 g and extract of Centella asiatica of 12 g added to the above solution under continuous stirring to get a uniform suspension. Finally, the suspension was made up to 1000 g to get the final coating suspension
Processing: The uniform suspension is then passed though mechanical milling process in homogenizer at 7000 rpm vigorously to incorporate air bubbles to obtain a frothy mass of viscosity of about 15000 mPaS and specific gravity of 0.58.
Coating: The above coating suspension was coated on to a foam substrate using lip coater to get a uniform coating of 60 mg/cm2 and dried under stream of hot air at a temperature of 70°C to get a bilayed foam , wherein 122.7 gram of dry composition comprisies Base- 81.5% w/w Centella Asiatic- 9.7% w/w Silk Fibroin- 7.7% w/w and Silver: 0.9 % w/w.
Example 5:
Coating solution preparation: In an example, Hydroxypropyl methyl cellulose 92 g was dissolved by heating water after complete dissolution, colloidal silver of 1.5 g, Silk Fibroin solution 14 g and extract of Centella asiatica of 16 g added to the above solution under continuous stirring to get a uniform suspension.
Processing: The uniform suspension is then passed though mechanical milling process in homogenizer at 8000 rpm vigorously to incorporate air bubbles to obtain a frothy mass of viscosity of about 19600 mPaS and specific gravity of 0.59.
Coating: The above coating suspension was coated on to a foam substrate using lip coater to get a uniform coating of 60 mg/cm2 and dried under stream of hot air at a temperature of 60°C to get a bilayed foam, wherein 123.5 gram of dry composition comprises Base- 74.4% w/w, Centella asiatica- 12.9% w/w, Silk Fibroin- 11.3% w/w and Silver: 1.2 % w/w.
Example 6:
Comparison of non-coated commercially available material with the wound dressing material of present invention.
A hydrophilic polyurethane foam is cut in to the size of a glass side of size 2.5.cm x 10.0.cm. The glass slide is made wet with purified water to resemble the wound surface with exudate. As illustrated in the Figure 1 the coated PU foam: 5 and non-coated PU foam: 5) it may be noted that the coated PU foam releases the coated ingredients in to the wet surface, accordingly at actual wound conditions it gets released to the wound bed and participate in the wound healing process. However, in case of commercially available hydrophilic polyurethane foams causes only contact effects and does not participate in the wound healing. It is clear from the figure 1 that the coated PU foam leached coated ingredients on to a wet surface mimicking the skin, where as there is no leaching from uncoated foam.
Example 7
Comparison of film coated foam substrate with wound healing composition and froth foam coated substrate with synergistic composition:
To study the effectiveness of the adoption of wound healing synergistic composition of present invention as a foam in the bilayered film; it is compared with the bilayered wound dressing material wherein the wound healing synergistic composition of present invention is coated as a uniform film.
It is observed that to produce a uniform coating film (figure 2(b)) it takes about 120 mg/cm2 of the coating solution of synergistic composition while in case of froth coating the same uniformity is achieved at half of the coating solution of 60 mg/cm2 (Figure 2(a)). The reason being the froth with higher viscosity of 22000 mPaS penetrates less into the substrate. However, the non- froth synergistic composition penetrates in to pores of substrate and hence more amount of coating solution consumed to get a uniform layer. The information is tabulated in table -1 below.
Table 1: Comparison of the film and foam coated substrates with synergistic composition
Sl No Feature Film coated substrate Foam coated substrate
1 Amount of coating solution 100-120mg/cm2 50-60mg/cm2
2 Processability High penetration into substrate Low penetration into substrate
3 Uniformity and texture Low uniformity with cracks High uniformity with mat like texture

Example 8:
The wound healing synergistic composition (50-60 mg/cm2) is coated as froth and film on the substrate (figure 3(a) and 3(b). As indicated in the figure 3(a) froth coating produced a layer over the substrate with mat like texture different from the texture of the substrate. However, in case of film coating, the composition penetrated in to foam giving similar texture to that of substrate as shown in figure 3(b) respectively.
Example 9
The bilayered wound dressing material with film and foam coated synergistic compositions are placed on glass plates made wet with purified water. After 1 min and 30 minutes of the placement of the wound dressing material, they were removed carefully without disturbing the residual left layer on the glass plate. The results of the experiment are illustrated in Figure 4. As observed, the foam coated wound dressing material leaches the coated composition on the wet surface to a significantly higher extent compared to film coated foam. The information is tabulated in table -2 below.
Table 2: Comparison of leaching of the film and foam coated susbstrates in the bilayered wound dressing materials.

Time Foam coated substrate Film coated substrate
Initial weight Final weight Leached amount Initial weight Final
weight Leached amount
1 minute 722mg 711mg 11mg 650mg 641mg 9mg
30 minutes 717mg 695mg 22mg 597mg 586mg 11mg

Example 10:
Analysis of antimicrobial activity of bilayered wound dressing
A petri plate having media and culture E.coli is taken using spread-plate technique. Bore wells are made in the media for inserting the sample. The bilayered wound dressing material, Silver coated polyurethane foam samples are cut to a size of 0.5cm X 0.5cm and inserted in the well and wet the sample by adding sterilized water. The antimicrobial activity is compared with streptomycin.
The study enabled to check the antimicrobial activity of Silver (Ag) coated Polyurethane(PU) foam with bilayered wound dressing material of present invention. As indicated in the table 3, the bilayered wound dressing material is found to have higher zone of inhibition as compared to the Silver (Ag) coated PU foam.
Table 3: Study of antimicrobial activity
No Sample Zone of Inhibition
1 Streptomycin (16PPM) 2cm
2 Silver coated PU Foam 1.2 cm
3 Bilayered wound dressing 1.5 cm

Example 11:
Validation of release of wound healing material from the bilayered wound dressing material on bovine skin. Comparison of bilayered wound healing materials with film coating and foam coating of wound healing synergistic composition.

The release of wound healing material from the bilayered wound dressing material is also validated using a piece of bovine skin. The bilayered wound dressing material with froth coating is placed on a wet bovine skin and firm application is ensured by gently pressing. A minutes later the wound dressing material is removed from the skin (figure 5). The figure 5 (c) clearly indicate that there is transfer of wound healing synergistic composition from bilayered wound healing dressing material to bovine skin. Thus, the material of present invention provides higher leaching to wet surface.
, Claims:
WE CLAIM
1. A bilayered wound dressing material comprising-
- froth form of wound palliating composition consisting extract of Centella asiatica, colloidal silver, Fibroin and a base; and
-a hydrophilic porous substrate.
2. The bilayered wound dressing material as claimed in claim 1, wherein the wound palliating composition of extract of Centella asiatica, colloidal silver, Fibroin and a base as foam is maximum 30% of thickness of the bilayered film.
3. The bilayered wound dressing material as claimed in claim 1, wherein the composition comprises extract of Centella asiatica ranging from 6% w/w to 12.9% w/w, colloidal Silver ranging from 0.5% w/w to 1.2% w/w and Fibroin ranging from 3.5% w/w to 11.3% w/w and base is ranging from 74.4% w/w to 90% w/w.
4. The bilayered wound dressing material as claimed in claim 1, wherein the base is selected from a group of Hydroxypropyl methyl cellulose, Hydroxypropyl cellulose, Polyvinyl alcohol and Polyvinyl Pyrrolidone.
5. The bilayered wound dressing material as claimed in claim 1, wherein the substrate is a polymer selected from a group comprising of hydrophilic polyurethane and cellulose.
7. A method of preparation of bilayered wound dressing material comprising- froth form of a wound palliating composition consisting of extract of Centella asiatica, colloidal silver, Fibroin and a base as foam; and a substrate- said method comprising acts of
a) preparing a solution of the base in water;
b) adding extract of Centella asiatica, colloidal Silver, Fibroin to the solution of base to obtain the suspension of wound palliating composition;
c) preparing froth form of the solution of the wound palliating composition;
d) coating the froth form of the composition on a substrate; and
e) drying to obtain the bilayered wound dressing material.
8. The method of preparation as claimed in claim 7, wherein the froth form of synergistic composition is by removing or adding air bubbles.
9. The method of preparation as claimed in claim 7, wherein the removing of the air bubbles is by resting of the solution for a period ranging from 4hr to 24hr; and addition of air bubbles is by a method selected from a group comprising homogenization, emulsification, or milling for a period ranging from 1min to 30 min.
10. The method of preparation as claimed in claim 7, wherein the drying is by hot air at a temperature ranging from 40℃ to 80 ℃.