Title of Invention

"A POLYPROPYLENE-GRAFT-POLY(ACRYLONITRILE-ACRYLAMIDE-ACRYLICACID) SUTURE"

Abstract The present invention relates to polypropylene monofilament grafted with preirradiated acrylonitrile monomer to obtain polypropylene grafted polyacrylonitrile suture, which on hydrolysis yields polypropylene-grafted poly(acrylonitrile/acrylamide/acrylicacid) suture of formula (1), followed by immobilization of drug to yield an antimicrobial polypropylene-grafted poly(acrylonitrile/acrylamide/acrylicacid)-drug composite suture. The invention also relates to a report of new polypropylene grafted suture of formula (l)obtained by hydrolysis and further relates to the process of preparation of said antimicrobial polypropylene sutures.
Full Text Antimicrobial Grafted Polypropylene Suture
Field of the invention
The present invention relates to pre-irradiated polypropylene monofilament grafted with acrylonitrile monomer to obtain modified polypropylene suture, which on hydrolysis followed by immobilization of drug results in antimicrobial grafted polypropylene sutures. The invention also relates to a report of new modified polypropylene suture obtained by hydrolysis and further relates to the process of preparation of said antimicrobial grafted polypropylene sutures.
Background and Prior art of the invention
The wound care is an important aspect in today's scenario which combines the comfort with the proper healing of the wound together. In many of the countries, the infection develops in the wounds a little later when a stich is applied. The invention relates to the development of a suture that may offer advantages over the present sutures in terms of the prevention of infection during stitching period.
Application of polypropylene as a suture material has long been known in the medical textile industry. Prolene sutures are available in the market, made up of polypropylene. This suture has certain advantages over other known sutures that it has inert nature and least tissue reactivity. Owing to its response as a foreign material to the body tissue, as well as the bacterial contamination at the site of its application, it can evoke the tissue reaction like inflammation, redness, swelling and wound infection that may lead to even the reopening of wound. Such discrepancies are more likely when there is no proper post-operation care and where wound closures are carried out in a non-sterilized environment. In several of the countries, such as in Asian countries the post-operation care is very little and bacterial infection is very prominent. However, there is no commercially available suture that may offer antimicrobial activity.
Applicants' previous work explains the use of radiation grafting of 2-hydroxyethylmethacrylate monomer onto polypropylene filament so that the antimicrobial drug such as 8-hydroxyquinoline may be immobilized on top of it (Gupta et al. J. Macromol. Sci., 30, 303 (1993). and J. Macromol. Sci., 27, 831 (1990)).
Gupta et al. Indian Patent No., 190584 (2003) describes antimicrobial sutures based on nylon filament developed by blending with the polyvinylpyrrolidone-iodine complex. The blending is a completely different approach than the grafting process. Blending involves the mixing of two polymers and then spinning it into a filament. So there is no chemical linkage between two polymers in the blending process. While in grafting, a monomer is polymerised in the presence of a pre-existing polymer so a chemical bond is created between the two polymers. Thus grafting process utilising a polymer and a monomer result in a single molecule.. Moreover, nylon sutures are known for the low knot security. The polypropylene suture offers better mechanical strength and the knot security as compared to the nylon sutures.
Gupta et al. J. ADDI. Polvm. Sci.. 69, 1343 1998 describes grafting of acrylonitrile onto polypropylene fibre. The objective of this work was to make the polypropylene fibre dyeable with dispersed dyes. The grafting of acrylonitrile introduces more amorphous volume and increases the accessibility of the dye into the fibre matrix. However, the product polypropylene grafted with acrylonitrile cited in this prior art has been further modified to achieve an objective which is very different from the objective of this citation. The present invention has developed a suture with multifunctional groups so that a drug may be effectively immobilized on top of that modified suture. However, the development of a suture has been in such a way that the nitrile group of the acrylonitrile grafted suture is hydrolysed so that the grafted suture with nitrile, amide and carboxylic groups is produced. The hydrolysed product polypropylene-grafted-acrylonitrile/acrylamide/acrylic acid is not reported in the prior art. This enables the hydrolysed product obtained to be new and novel.
The prior art describes sutures which can also form the base to prepare anti microbial sutures, but the sutures obtained will still be associated with the following limitations:-
a) Poor mechanical strength and knot security of sutures.
b) Immobilization of limited class of drugs on sutures.
In order to overcome the above limitations, Applicant has developed a modified polypropylene grafted suture by adopting the step of hydrolysis of the polypropylene monofilament grafted polyacrylonitrile sutures and subsequently
immobilizing the anti microbial drug on to the product obtained by hydrolysis to achieve suture with anti microbial property which prevents the infection at the implanted site. Modification of polypropylene suture through a grafting technique using a reactive and suitable monomer followed by the immobilization of drug could be one of the main routes to overcome these problems.
The process that has been used for the modification of the polypropylene suture is radiation grafting and has been known since a long time. The preirradiation grafting of monomers has been used to modify the polymers for different applications
The radiation grafting is able to introduce the desirable properties in a polymer without much influencing its inherent characteristics. If the polymer is hydrophobic in nature, this may be transformed into a hydrophilic structure by careful selection and grafting with a hydrophilic monomer. The polymer therefore retains most of its inherent properties while it acquires additional properties imparted by the monomer. The modified suture, by virtue of the functional groups, offers sites which provides binding of hydrophilic and ionic drug molecule. Once the drug loaded suture comes in contact with the tissue, the sutures which absorbs water having hydrophilic character releases the drug to the surrounding tissues thereby preventing bacterial invasion.
The development of an antimicrobial suture is a new concept and reality. Not a single bio-stable suture is available in the market. Applicant's previous invention on Nylon sutures has led to the development of antimicrobial suture but it has not been in the market
Objects of Invention
Main object of the invention is to provide antimicrobial polypropylene grafted poly (acrylonitrile/acrylamide/acrylicacid)-drug composite suture.
An object of the invention is to provide hydrolysed polypropylene mono filament grafted with acrylonitirile monomer having hydrophilic nature.
Another object of the invention is to provide hydrolysed suture with polar carboxylic groups.
Yet another object of the invention is to provide hydrolysed suture loaded with drug to obtain antimicrobial PP grafted suture.
Yet another object of the invention is to provide modified PP sutures which release the drug slowly in the surrounding tissue.
Still yet another object of the invention is to provide an efficient process for the preparation of modified polypropylene grafted poly (acrylonitirile /acrylamide/acrylic acid) suture.
Yet another object of the invention is to provide a process for the immobilization of drug on modified polypropylene grafted acrylonitirile /acrylamide/acrylic acid sutures.
Still yet another object of the invention is to provide sutures having better mechanical strength and knot security.
Summary of the invention
The invention relates to an antimicrobial polypropylene-grafted-poly(acrylonitirile-acrylamide-acrylic acid)-drug composite suture. The invention also relates to a process for the preparation of the said sutures by grafting into pre-irradiated polypropylene filament suture with acrylonitile monomer under Co60 radiation doses of 5 kGy to 200 KGy at a temperature ranging between 50°- 80°C in a solvent, followed by the hydrolysis of the grafted polymers to obtain modified polypropylene grafted poly(acrylonitrile-acrylamide-acrylicacid) suture onto which antimicrobial drug is immobilized.
Detailed description of the invention
Accordingly the present invention provides an antimicrobial polypropylene-grafted-poly(acrylonitirile-acrylamide-acrylicacid)- suture of formula (I)
(Formula removed)

In an embodiment of the present invention provides polypropylene-grafted-poly(acrylonitirile-acrylamide-acrylic acid)- drug composite antimicrobial suture.
Another embodiment of the present invention provides a grafted polypropylene suture of formula (1) having tensile strength upto 3.4 gpd.
Yet another embodiment of the present invention provides a grafted polypropylene suture of formula (1) having knot security upto 22gpd.
Still another embodiment of the present invention provides a suture the drug is an antimicrobial agent,
Yet another embodiment of the present invention provides the use of an antimicrobial agent selected from a group consisting of hydrophilic or ionic drug for immoblising on to sutures.
Still yet another embodiment of the present invention is provides antimicrobial agent used is selected from a group consisting of ciprofloxacin, tetracycline, 8-hydroxyquinoline, benzoic acid or its pharmaceutically acceptable salts
Another embodiment of the present invention provides an antimicrobial grafted polypropelne suture which is effective against infection caused by E.Coli, K.pneumonia and S. aureus.
Still yet another embodiment of the present invention provides a process for the preparation of polypropylene-grafted-poly (acrylonitirile-acrylamide-acrylic acid) - drug composite suture comprising steps of:
a. preparing polypropylene monofilament suture by melt spinning of the
polypropylene polymer using an extruder,
b. grafting by preirradiation of the suture of step (a) in presence of air
to create hydroperoxide group known fact grafting further the suture
of step (b) with acrylonitrile monomer using Co60 radiation under
radiation doses ranging between 5kGy to 200kGy over a period of
15 minutes to 6h.. h, at a temperature ranging between of 50°-80°C
in a solvent containing optionally an acid to obtain PP grafted
polyacrylonitrile suture,
c. hydrolysing the PPgrafted suture of step (c) obtained by treating with
an alkali solution to yield (polypropylene)-graft-poly(acrylonitirile-
acrylamide-acrylic acid) suture of formula (I).
d. immobilizing the drug onto the suture of step(d), and
e. obtaining polypropylene-graft poly(acrylonitirile/acrylamide/acrylic acid)- drug composite antimicrobial suture.
Still another embodiment of the present invention provides the use of a solvent selected from a group consisting of dimethylformamide(DMF),DMF-water mixture,acetone and methylethylketone for grafting.
Yet another embodiment of the present invention provides also the use of an acid, preferably sulfuric acid for grafting.
Still yet another embodiment of the present invention provides the use of an alkali solution selected from a group consisting of sodium hydroxide or potassium hydroxide solution for hydrolysis of PP grafted polymer.
The suture development was carried out by pre-irradiation grafting of acrylonitrile monomer onto polypropylene suture. Polypropylene suture was irradiated in air with gamma radiation for sufficient time to activate the suture and create radical sites. The irradiation doses were selected in the range of 10-200kGy. Subsequently, the activated suture was grafted with acrylonitrile monomer of different monomer concentrations in a solvent at a temperature ranging between 50 and 80°C. The grafting in the range of 1-24% is achieved. The acrylonitrile grafted polypropylene suture is subsequently hydrolysed under alkaline conditions so that a fraction of nitrile groups are converted into amide and carboxyl groups respectively. The innovation therefore relates to the development of apolypropylene-grar?-poly(acrylonitrile-acrylamide-acrylic acid)-drug composite antimicrobial suture for clinical applications.
(Formula removed)


The following examples further illustrate the embodiments within the scope of the present invention. The examples are given solely for the purposes of illustrations and not to be construed as limitations of the present invention as many variations are possible without departing from its scope.
Examples Example 1 - General Procedure
(a) Preparation of Polypropylene monofilament suture:
The polypropylene monofilament suture is prepared by melt spinning of the polymer using an extruder. The radiation grafting into polypropylene sutures carried out with acrylonitrile using a Co60 radiation under radiation doses of 5kGy to 200kGy. The grafting is carried by pre-irradiation of the polypropylene suture with radiation under air to create hydroperoxide groups and subsequent contact with the monomer at elevated temperature.
(b) Grafting reaction
The polypropylene filament is placed in the tube and exposed to the gamma radiation under air. The filament is therefore activated by the oxidation process and is subsequently used for the grafting reaction. The exposed filament is placed in a reaction tube and the monomer solution in a solvent is added to the tube. The top of the tube is fitted with a gas inlet and nitrogen is passed through the tube so that air may be excluded from the grafting medium. The reaction tube is subsequently placed in the water bath thermostat controlled at a given temperature. The tube is kept in the bath for a desired period and after the completion of grafting.
In the following figure, the influence of the radiation dose on the degree of grafting at a monomer concentration of 10% is shown. Higher the radiation dose, the higher is the degree of grafting. The grafting is further enhanced considerably when the monomer concentration is increased
(Formula removed)

Hydrolysis of Polypropylene grafted poly acrylonitrile suture:
Hydrolysis of the grafted sutures is carried out by using different concentrations of sodium hydroxide at different temperatures in a thermostat water bath for different time periods. Subsequently, the sutures are taken out and washed thoroughly with double distilled water. These sutures are placed in 2% hydrochloric acid for 2 h to convert alkali salt of carboxyl groups into free carboxylic groups. Finally, sutures are washed with distilled water several times till washings were free from the acid to obtain modified polypropylene grafted poly(acrylonitrile/acrylamide/acrylicacid) suture.
(c) Drug immobilization
The modified PP grafted sutures of are immersed in a 20 % aqueous solution of tetracycline hydrochloride for 24 h. The samples are taken out, washed thoroughly with distilled water and dried under vacuum at 40°C for 2 h. The percent addon of the drug is calculated by the following expression.
(Formula removed)

where, Wd is the weight of the drug immobilized sample and Wt is the weight of the sample before immobilization.
d) Antimicrobial assay(in vitro)
Nutient Agar plates is prepared by dissolving 31 gms of readymade Muller Hinton agar (Hi Media Laboratories, Mumabai) in 1 litre water and the pH is adjusted to 7.3±0.2. The contents are sterlised by autoclaving at 15 lbs pressure (121C) for 30 minutes. The media when still hot, is poured in sterile petriplates (approximately 20 ml), and were allowed to coll so that the agar solidified. The composition of nutrient agar medium is beef extract 3 gm/litre, peptone 5 gm/litre, NaCI 8gm/ litre and agar 15gm/ litre.
The antimicrobial properties of the drug loaded sutures are assesed against E. coli, K. pneumonia and S. aureus. Nutrient agar plates were prepard and a lawn of bacteria were laid over the plate using a sterile cotton swab. A weighed amount of drug immobilized suture is placed on the plate using sterile forcep. An unmodified suture is palced in each plate as control. The plates are
incubated at 37°C for 24 h and the clear zone around the sample was measured the next day as a measure of antimicrobial activity of the drug loaded suture.
(e)Animal Studies(in vivo)
The resistance of modified sutures to infection against S. aureus is studied in vivo on albino rats. Suture are stiched on approximately 2.5 cm area parallel and equidistant from vertebral column after shaving and sterlizing it with 70 % ethyl alcohol. The designated number of bacteria was injected into the tisue around the middle of each suture. The number of bacteria at the implantation site varied in the range of 104-105. The sutures are analyzed for infection growth on 1st and 3rd post operative day of suturing. Some of the drugs that may be used for the immobilization are as follows:
Ciprofloxin, 8-hydroxyquinolin, Tetracycline, Benzoic acid or its pharmaceutically acceptable salts
Example 2
PP filament is exposed to 45kGy radiation followed by acrylonitriie grafting on irradiated PP filament is carried out using 20% acrylonitriie monomer concentration in DMF at 60°C. The graft yield obtained is1.5%.
Example 3
PP filament is exposed to 45kGy radiation followed by acrylonitriie grafting on irradiated PP filament is carried out using 80% acrylonitriie monomer concentration in methylethylketone at 60°C. The graft yield obtained is 5%.
Example 4
PP filament is exposed to 45kGy radiation followed by acrylonitriie grafting on irradiated PP filament is carried out using 80% acrylonitriie monomer concentration in DMF/water and sulfuric acid is added to this mixture at 60°C. The graft yield obtained is 12% due to the acceleration effect of the sulfuric acid
Example 5
PP filament is exposed to 100kGy radiation followed by acrylonitriie grafting on irradiated PP filament is carried out using 80% acrylonitriie monomer
concentration in DMF/water and sulfuric acid(0.05 mole/I) is added to this mixture at 60°C. The graft yield obtained is 16%.
Example 6
PP filament is exposed to 10OkGy radiation followed by acrylonitnle grafting on irradiated PP filament is carried out using 80% acrylonitnle monomer concentration in DMF/water and sulfuric acid(0.05 mole/I) is added to this mixture at 60°C. The graft yield obtained is 24%.
Example7
PP filament is exposed to 200kGy radiation followed by acrylonitrile grafting on irradiated PP filament is carried out using 80% acrylonitrile monomer concentration in DMF/water and sulfuric acid(0.05 mole/I) is added to this mixture at 80°C. The graft yield obtained is 28%.
Example 8
PP filament is exposed to 45kGy radiation followed by acrylonitrile grafting on irradiated PP filament is carried out using 60% acrylonitrile monomer concentration in DMF/water and sulfuric acid(0.05 mole/I) is added to this mixture at 80°C. The graft yield obtained is 8%. The tensile strength of the suture is found to be 2.9 gpd and the knot strength of the suture is 1.8gpd.
Example 9
PP monofilament is grafted using acrylonitrile monomer by adapting any one of the processes mentioned in above examples to obtain PP grafted polyacrylonitrile suture. The drug mobilization of this suture could not be achieved.
Example 10
PP filaments with a graft level of 2-28% as per examples above were hydrolyzed with 20% sodium hydroxide solution of for 4h. The reaction is carried out at 50°C. The carboxyl content of 0.5-1.26 mmol/g is achieved. The tensile strength of the suture is in the range of 2.2-3.4 gpd. The knot strength of the suture is 1.6-22gpd.
Example 11
PP filaments with a graft level of 8% were hydrolyzed with 10% sodium hydroxide solution for 4h. The reaction is carried out at 50°C. The carboxyl content of 0.3 mmol/g is achieved. The tensile strength of the suture is 2.8 gpd and the knot strength of the suture is 1.8gpd
Example 12
PP filaments with a graft level of 8% were hydrolyzed with 10% sodium hydroxide solution of 10% for 4h at 50°C. The carboxyl content of 0.3 mmol/g is achieved. The water uptake is 5.6%. This is followed by immobilization of tetracycline hydrochloride on the hydrolysed grafted PP suture. The drug loading is in the range of 0.5-6.5%.
Example 13
PP filaments with a graft level of 8% were hydrolyzed with sodium hydroxide solution. The drug loading is 2.5mg/g. The in-vitro studies showed that the drug released for 4 days.
(Formula removed)
Example 14
PP filaments with a graft level of 8% and the tetracyclinehydrochloride loading of 2.5 mg/g is subcutaneously implanted in mouse. The observations showed that the E. coli infection originated in unmodified sutures but the modified sutures did not show any infection and inflammation.
Example 15
PP filaments with a graft level of 8% acrylonitrile are immobilized with tetracycline hydrochloride. The drug could not be immobilized on the grafted suture.
Example 16
PP filaments with a graft level of 8% and the tetracycline loading of 2.5 mg is subcutaneously implanted in mouse. The modified sutures did not show any appreciable inflammation and tissue reaction.
(Formula removed)

Main advantages:
1) The invention provides an antimicrobial polypropylene grafted suture for preventing bacterial and fungicidal invasion;
2) The invention provides a suture with good mechanical strength and knot security.
3) The invention provides a modified suture having polar carboxylic groups facilitating the immobilization of the antimicrobial drug on the suture.
4) The invention provides a suture which releases the drug slowly over a period of 4 days.










We claim:
1. A polypropylene-graft-poly(acrylonitirile-acrylamide-acrylicacid) suture of formula
(I)
(Formula Removed)
2. A suture as claimed in claim 1 further comprising an immobilized drug to obtain polypropylene-graft-poly (acrylonitirile-acrylamide-acrylic acid) - drug composite antimicrobial suture.
3. A suture as claimed in claim 1 has tensile strength up to 3.4 gpd.
4. A suture as claimed in claim 1 has knot security up to 22 gpd.
5. A suture as claimed in claim 2, wherein the drug is an antimicrobial agent.
6. A suture as claimed in claim 5, wherein the antimicrobial agent is selected from the group consisting of ciprofloxacin, tetracycline, 8-hydroxyquinoline, benzoic acid or its pharmaceutically acceptable salts.
7. A suture as claimed in claim 2 is effective against infection caused by E. Coli, K. pneumonia and S. aureus.
8. A process for the preparation of suture of claim 2, the said process comprising steps of:
a. preparing polypropylene monofilament suture by melt spinning of the
polypropylene polymer using an extruder,
b. grafting by preirradiation of the suture of step (a) in presence of air to create
hydroperoxide group known fact [please confirm grafting further the suture of
step (b) with acrylonitrile monomer using Co60 radiation under radiation doses
ranging between 5kGy to 200kGy over a period of 15 minutes to 6 hours at a
temperature ranging between of 50°-80°C in a solvent containing optionally an
acid to obtain PP grafted polyacrylonitrile suture,
c. hydrolyzing the PP grafted suture of step (c) obtained by treating with an
alkali solution to yield (polypropylene)-graft-poly(acrylonitirile-acrylamide-
acrylic acid) suture of formula (I).
d. immobilizing the drug onto the suture of step (d), and
e. obtaining polypropylene-graft poly(acrylonitirile/acrylamide/acrylic acid)-
drug composite antimicrobial suture of claim 2.
9. A process of claim 8, wherein in step (c) the solvent used is selected from a group consisting of dimethylformamide (DMF), DMF-water mixture, acetone and methylethylketone.
10. A process of claim 8, wherein the acid used is a mineral acid.
11. A process of claim 10, wherein the mineral acid is sulphuric acid
12. A process of claim 8, wherein in step (d) the alkali solution used is selected fro a group consisting of sodium hydroxide or potassium hydroxide solution.
13. A process of claim 8, wherein in step (e) the drug is an antimicrobial agent.
14. A process of claim 13 wherein the antimicrobial agent is selected from a group consisting of hydrophilic or ionic drug.
15. A process of claim 12, wherein the drug is selected from a group consisting of Ciprofloxin, 8-hydroxyquinonline, tetracycline, Benzoic acid or its pharmaceutically acceptable salts.
16. A process of claim 8, wherein in step (f) the suture obtained is effective against infection caused by E. Coli, K. pneumonia and S. aureus.

Documents:

1050-DEL-2004-Abstract-(05-03-2012).pdf

1050-del-2004-abstract.pdf

1050-DEL-2004-Claims-(05-03-2012).pdf

1050-del-2004-claims.pdf

1050-DEL-2004-Correspondence Others-(05-03-2012).pdf

1050-DEL-2004-Correspondence Others-(15-02-2012).pdf

1050-del-2004-Correspondence Others-(22-05-2012).pdf

1050-del-2004-correspondence-others.pdf

1050-del-2004-description (complete).pdf

1050-del-2004-Form-1-(22-05-2012).pdf

1050-del-2004-form-1.pdf

1050-del-2004-Form-13 (05-03-2012).pdf

1050-del-2004-form-18.pdf

1050-del-2004-Form-2-(22-05-2012).pdf

1050-del-2004-form-2.pdf

1050-del-2004-form-26.pdf

1050-del-2004-form-3.pdf

1050-del-2004-form-5.pdf

1050-DEL-2004-GPA-(15-02-2012).pdf


Patent Number 252546
Indian Patent Application Number 1050/DEL/2004
PG Journal Number 21/2012
Publication Date 25-May-2012
Grant Date 22-May-2012
Date of Filing 07-Jun-2004
Name of Patentee INDIAN INSTITUTE OF TECHNOLOGY
Applicant Address HAUZ KHAS, NEW DELHI-110016, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 ANJUM, NISHAT TECHNOLOGY, HAUZ KHAS, NEW DELHI-110016, INDIA.
2 REVAGADE, NILESH TECHNOLOGY, HAUZ KHAS, NEW DELHI-110016, INDIA.
3 BHUVANESH GUPTA TECHNOLOGY, HAUZ KHAS, NEW DELHI-110016, INDIA.
4 SYED KALIMUL HAQUE GULREZ TECHNOLOGY, HAUZ KHAS, NEW DELHI-110016, INDIA.
5 HARPAL SINGH TECHNOLOGY, HAUZ KHAS, NEW DELHI-110016, INDIA.
PCT International Classification Number C08K 3/20
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA