WO2012086988A2

WO2012086988A2 - Artificial silk membrane having excellent flexibility and suturing ability and method of manufacturing the same

Info

Publication number: WO2012086988A2
Application number: PCT/KR2011/009826
Authority: WO
Inventors: You Young Jo; Hae Yong Kweon; Kwang-Gill LEE; Seok Woo Kang; Joo Hong Yeo; Soon Ok Woo; Sang Mi Han; Sung Hee Nam
Original assignee: Republic Of Korea(Management : Rural Development Administration)
Priority date: 2010-12-23
Filing date: 2011-12-20
Publication date: 2012-06-28
Also published as: WO2012086988A3; WO2012086988A9; KR20120071546A; KR101322337B1

Abstract

Disclosed herein is an artificial silk membrane, including: 50.00 ~ 99.99 wt% of silk fibroin; and 0.01 ~ 50.00 wt% of a salt. The artificial silk membrane is advantageous in that, when it is used as an artificial cerebral dura mater or a biomembrane, a surgical procedure and treatment can be easily carried out because it can ensure safety and can greatly improve flexibility.

Description

ARTIFICIAL SILK MEMBRANE HAVING EXCELLENT FLEXIBILITY AND SUTURING ABILITY AND METHOD OF MANUFACTURING THE SAME

The present invention relates to an artificial silk membrane and a method of manufacturing the same, and, more particularly, to an artificial silk membrane having excellent flexibility and suturing ability, which constitutes artificial cerebral dura mater or a biomembrane, and to a method of manufacturing the same.

Some patients to be subjected to a neurosurgical operation must make up a loss in cerebral dura mater with artificial cerebral dura mater. In this case, a patient’s cerebrum is sutured, so that the cerebrum is provided thereon with a protective layer, thereby reducing cerebral infection after a surgical operation on brain.

The cerebral dura mater, which is interposed between the skull and the cerebrum to cover the spinal marrow, functions to protect the spinal marrow and to prevent the spinal fluid from leaking. Generally, in the field of neurosurgery, cerebral dura mater is damaged when performing an operation on cerebral nervous tissue. Therefore, it is required to replace or repair the damaged cerebral dura mater after the operation, so that human cerebral dura mater lyophilized products have been used.

However, problems with the human cerebral dura mater lyophilized products are that uniformity cannot be secured and that it is difficult to supply theme. Further, it was reported that the human cerebral dura mater lyophilized products can cause Creutzfeldt-Jakob Disease (CJD) by means of the human cerebral dura mater, so that, currently, the use of the human cerebral dura mater lyophilized products is forbidden.

As alternatives to the human cerebral dura mater lyophilized products, artificial cerebral dura maters made of various synthetic materials were developed. For example, artificial cerebral dura mater made of a silicon material was developed. However, it was reported that, since artificial cerebral dura mater made of a silicon material does not decompose, it eternally remains in the body, so that it acts as a chronic irritant on peripheral tissues, thereby causing side effects.

Korean Patent Registration No. 10-100461475 discloses a collagen material including nonfibrous collagen layers and an ultrafine fibrous collagen layer disposed between the nonfibrous collagen layers, and proposes that this collagen material be used as a material for making up the loss of a biomembrane such as cerebral dura mater, pericardium, pleura, peritoneum, serosa or the like.

Korean Unexamined Patent Publication No. 10-2001-0052714 discloses a collagen material manufactured by charging biocompatible, biodegradable and bioabsorbable materials in a matrix which is a collagen fiber nonwoven fabric structure including ultrafine collagen fiber as a basic unit, and proposes that this collagen material be used in medical artificial membranes, such as artificial neurocanals, artificial spinal marrow, artificial esophagus, artificial organs, artificial blood vessels, artificial valves, artificial cerebral dura mater, etc.; artificial ligaments; artificial tendons; surgical sutures; surgical fillers; surgical reinforcing materials, artificial skin; artificial cornea; and the like.

Further, artificial cerebral dura mater manufactured using a biocompatible material was proposed. Such dura mater includes, for example, collagen-based or gelatin-based artificial cerebral dura mater. However, such artificial cerebral dura mater could not practically used because it cannot exhibit sufficient suturing ability when it is sutured with biological cerebral dura mater.

Furthermore, artificial cerebral dura mater manufactured using collagen derived animal (cattle) was proposed. However, such artificial cerebral dura mater is problematic in that it can be infected by zooanthroponosis, such as mad cow disease or the like. Regardless of such serious defects, currently, there is not alternative product to the artificial cerebral dura mater using collagen derived animal (cattle).

[Cited references]

[Patent Documents]

Korean Patent Registration No. 10-100461475 "Collage material and manufacturing method thereof"

Korean Unexamined Patent Publication No. 10-2001-0052714 "Collage material and manufacturing method thereof"

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an artificial silk membrane having excellent flexibility and suturing ability, which constitutes artificial cerebral dura mater or a biomembrane, and a method of manufacturing the same.

Another object of the present invention is to provide an artificial silk membrane, which can secure safety at the time of a neurosurgical operation because it is biocompatible and transparent, and a method of manufacturing the same.

Still another object of the present invention is to provide an artificial silk membrane, which does not cause inflammation at the time of a neurosurgical operation and which does not have cytotoxicity, and a method of manufacturing the same.

Objects to be accomplished by the present invention are not limited to the above-mentioned objects, and the following descriptions will make these other objects clearly understandable by those skilled in the art.

In order to accomplish the above objects, an aspect of the present invention provides an artificial silk membrane, including: silk fibroin; and a salt.

Specifically, the artificial silk membrane may include: 50.00 ~ 99.99 wt% of the silk fibroin; and 0.01 ~ 50.00 wt% of the salt.

The salt may be any one selected from the group consisting of calcium chloride, sodium chloride, potassium chloride, and sodium acetate.

The artificial silk membrane may further include: more than 0 wt% but not more than 20 wt% of any one selected from the group consisting of carbon nanotube and fiber.

The artificial silk membrane may further include: more than 0 wt% but not more than 30 wt% of any one selected from the group consisting of collagen, gelatin, chitin, chitosan, keratin, cellulose, fibronectin, elastin, fibrinogen, fibromodulin, laminin, tenascin, vitronectin, alginate, hyaluronic acid, silk protein and derivatives thereof, agarose, polylactic acid (PLA), polyglycolic acid (PGA), a copolymer (PLGA) of polylactic acid and polyglycolic acid, polycaprolactone (PCL), poly{poly(ethyleneoxide)terephthalate-co-butyleneterephthalate} (PEOT/PBT), polyphosphoester (PPE), polyphosphagen (PPA), polyanhydride (PA), polyorthoester (POE}, poly(propylene fumarate)-diacrylate (PPF-DA}, and poly(ethylene glycol) diacrylate (PEG-DA}.

The artificial silk membrane may further include: one or more selected from the group consisting of antibiotics, antiviral agents, bactericides, nucleic acids, peptides, and proteins.

The artificial silk membrane may have a tensile strength of 2 ~ 100 MPa.

The artificial silk membrane may be used as an artificial cerebral dura mater or a biomembrane.

Another aspect of the present invention provides a method of manufacturing an artificial silk membrane, comprising the steps of: 1) mixing 0.01 ~ 50.00 wt% of a salt with 50.00 ~ 99.99 wt% of silk fibroin to prepare a mixed solution; and 2) pouring the mixed solution into a flat container and then drying the mixed solution to form an artificial silk membrane.

In step 2), the mixed solution may be poured into a flat container and then dried in a thermostatic chamber having a temperature of 20~80℃ and containing 20~80% of moisture.

The mixed solution dried in step 2) may be crystallized.

The crystallization of the dried mixed solution may be conducted by charging the dried mixed solution into a hermetic container having a relative humidity of 80% or more and then annealing the mixed solution with water.

The crystallization of the dried mixed solution may be conducted by immersing the container charged with the dried mixed solution into a mixed solvent in which a hydrophilic polar solvent of four carbon atoms or less and distilled water are mixed in a weight ratio of 70~90 : 10~30.

As described above, when the artificial silk membrane of the present invention is used as an artificial cerebral dura mater or a biomembrane, surgical procedure and treatment can be easily performed because it can secure safety and can greatly improve flexibility.

Further, since the artificial silk membrane of the present invention can be formed into a thick silk membrane having a thickness of 300 ㎛ or more, the thickness thereof can be adjusted.

Further, the artificial silk membrane of the present invention does not obstruct a doctor’s view because it has flexibility and transparency. Further, the artificial silk membrane of the present invention allows a surgical procedure to be conducted more easily because it has excellent suturing ability.

Further, the artificial silk membrane of the present invention does not have cytotoxicity, and has water resistance functioning to protect the spinal marrow and to prevent the spinal fluid from leaking.

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a graph showing the extension rate of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention.

FIG. 2 is photographs showing the sections and surfaces of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention.

FIG. 3A is a photograph showing the transparency of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention.

FIG. 3B is a photograph showing the transparency of artificial silk cerebral dura mater made of conventional collagen derived from cattle.

FIG. 4 is a photograph showing the flexibility of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention.

FIG. 5 is a photograph showing the suturing ability of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention.

FIG. 6A is a graph showing the results of a cytotoxicity test of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention after culturing the artificial silk cerebral dura mater for 24 hours.

FIG. 6B is a graph showing the results of cytotoxicity test of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention after culturing the artificial silk cerebral dura mater for 48 hours.

FIG. 6C is a graph showing the results of cytotoxicity test of artificial silk cerebral dura mater made of an artificial silk membrane of the present invention after culturing the artificial silk cerebral dura mater for 72 hours.

Hereinafter, preferred embodiments of the present invention will be described.

The artificial silk membrane of the present invention includes: silk fibroin and a salt.

Silk fibroin is a protein constituting cocoon yarn (silk) together with sericin. Silk fibroin uniformly includes 18 kinds of amino acids. Silk fibroin, unlike keratin protein constituting wool fiber, includes a large amount of glycin and a large amount of alanine.

Most of the amino acids constituting a collagen protein, which is a major protein constituting human skin, are glycin and alanine constituting a fibroin protein. As such, the fibroin protein having an amino acid structure similar to that of human skin has excellent biocompatibility and does not cause inflammation. For this reason, the artificial silk membrane of the present invention can overcome apprehensions about stability.

A salt serves to make a stiff membrane formed of only silk fibroin flexible. For this reason, the artificial silk membrane of the present invention has flexibility. Further, the salt serves to increase the strength of the artificial silk membrane of the present invention.

Any kind of salt may be used as the salt. It is preferred that the salt be any one selected from the group consisting of calcium chloride, sodium chloride, potassium chloride, and sodium acetate.

As such, since the artificial silk membrane including the silk fibroin and the salt according to the present invention has excellent flexibility and strength, surgical procedure and treatment can be very easily conducted. Particularly, since the artificial silk membrane of the present invention has very excellent suturing ability, it has water resistance functioning to protect the spinal marrow and to prevent the spinal fluid from leaking. Therefore, the artificial silk membrane of the present invention is suitable for use as artificial cerebral dura mater.

Further, since the artificial silk membrane of the present invention has transparency, it can be safely treated at the time of an operation, and, since it does not have cytotoxicity, it can be widely used as a biomembrane.

The artificial silk membrane of the present invention may include 50.00 ~ 99.99 wt% of the silk fibroin and 0.01 ~ 50.00 wt% of the salt.

When the amount of the silk fibroin is less than 50.00 wt%, it is difficult to form an artificial silk membrane, and, when the amount thereof is more than 99.99 wt%, the flexibility of an artificial silk membrane is deteriorated.

Further, the amount of the salt is less than 0.01 wt%, the flexibility of an artificial silk membrane is deteriorated, and, when the amount thereof is more than 50.00 wt%, the formation of silk fibroin into an artificial silk membrane can be hindered.

The artificial silk membrane of the present invention may further include any one selected from the group consisting of carbon nanotubes and fiber. It is preferred that the amount thereof be more than 0 wt% but not more than 20 wt% based on the total amount of the artificial silk membrane. The amount of the silk fibroin and the amount of the salt may be adjusted depending on the amount of any one selected from the group consisting of carbon nanotube and fiber.

Carbon nanotube or fiber such as nanocellulose serves to improve the physical properties of the artificial silk membrane while maintaining the transparency of silk fibroin. When the carbon nanotube or the fiber is include in an amount of more than 20 wt% based on the total amount of the artificial silk membrane, the transparency or the like of the artificial silk membrane can be deteriorated.

Further, the artificial silk membrane of the present invention may further include: more than 0 wt% but not more than 30 wt% of any one selected from the group consisting of collagen, gelatin, chitin, chitosan, keratin, cellulose, fibronectin, elastin, fibrinogen, fibromodulin, laminin, tenascin, vitronectin, alginate, hyaluronic acid, silk protein and derivatives thereof, agarose, polylactic acid (PLA), polyglycolic acid (PGA), a copolymer (PLGA) of polylactic acid and polyglycolic acid, polycaprolactone (PCL), poly{poly(ethyleneoxide)terephthalate-co-butyleneterephthalate} (PEOT/PBT), polyphosphoester (PPE), polyphosphagen (PPA), polyanhydride (PA), polyorthoester (POE}, poly(propylene fumarate)-diacrylate (PPF-DA}, and poly(ethylene glycol) diacrylate (PEG-DA}.

The term “transparent” or “transparency” used in the present specification includes a transparent state that is transparent to such a degree that the inside of the artificial silk membrane can be observed, in addition to a completely transparent state.

The artificial silk membrane of the present invention can be manufactured using only the silk fibroin and salt, but a biocompatible material may also be added as long as it does not deteriorate the transparency and physical properties of the artificial silk membrane. The biocompatible material may be added in an amount of 30 wt% or less based on the total amount of the artificial silk membrane. When the amount of the biocompatible material is more than 30 wt%, there is a problem in that the transparency or the like of the artificial silk membrane is deteriorated.

The artificial silk membrane of the present invention can be manufactured by adding various physiologically-active materials. The physiologically-active materials can be used without limitations as long as they do not have negative effects on the structure and function of the artificial silk membrane.

For example, the physiologically-active materials used in the present invention may be one or more selected from the group consisting of antibiotics, antiviral agents, bactericides, nucleic acids, peptides, and proteins. The physiologically-active materials, such as antibiotics, antiviral agents, bactericides and the like, serve to prevent the artificial silk membrane from being infected. The protein is any one selected from the group consisting of hormones, cytokines, enzymes, antibodies, growth promoters, transcriptional regulators, vaccines, structural proteins, ligand proteins, receptors, cell surface antigens, and receptor antagonizing substances.

It is preferred that the tensile strength of the artificial silk membrane of the present invention be 2 ~ 100 MPa.

Meanwhile, the artificial silk membrane of the present invention is manufactured by mixing a liquid salt with liquid silk fibroin to prepare a mixed solution, pouring the mixed solution into a flat container and then drying the mixed solution. The mixed solution may include 50.00 ~ 99.99 wt% of silk fibroin and 0.01 ~ 50.00 wt% of a salt.

The mixed solution poured into the flat container may be dried by casting. That is, the mixed solution pored into the flat container is cast and dried using a solution-film-forming method to manufacture the artificial silk membrane of the present invention.

Further, the mixed solution poured into the flat container may be dried in a thermostatic chamber having a temperature of 20~80℃ and containing 20~80% of moisture to manufacture the artificial silk membrane of the present invention.

As described above, any kind of salt may be used as the salt. The salt may be any one selected from the group consisting of calcium chloride, sodium chloride, potassium chloride, and sodium acetate.

Meanwhile, the artificial silk membrane of the present invention may be manufactured by charging the mixed solution into a flat container, drying the mixed solution and then crystallizing the dried mixed solution.

Further, the crystallization of the dried mixed solution may be conducted by immersing the container charged with the dried mixed solution into a mixed solvent in which a hydrophilic polar solvent of four carbon atoms or less and distilled water are mixed in a weight ratio of 70~90 : 10~30. Examples of the hydrophilic polar solvent of four carbon atoms or less may include, but are not limited to, lower alcohols, such as methanol, ethanol, propanol, etc.

Hereinafter, the present invention will be described in detail with reference to the following Example and Experimental Example. However, the Example and Experimental Example are set forth to illustrate the present invention, and the scope of the present invention is not limited thereto.

＜Example 1＞ Manufacture of artificial silk membrane

A cocoon (silk) was used as a sample. The cocoon was scoured with Marseilles soap at 100℃ to remove sericin therefrom.

The scoured silk was dissolved in an aqueous solution, in which calcium chloride, ethanol and water were mixed in a molar ratio of 1:2:8, at 80℃ for 20 minutes to obtain an aqueous silk solution.

This aqueous silk solution was dialyzed with distilled water for 3 days using a dialysis membrane (MWCO=12,000) to remove salts and ethanol therefrom, thus obtaining an aqueous silk fibroin solution.

The concentration of the obtained aqueous silk fibroin solution was about 2.5%. In order to increase the concentration thereof to 7 ~ 8%, the aqueous silk fibroin solution was concentrated using PEG 20,000 (polyethylene glycol).

Subsequently, 0.01 ~ 50.00 wt% of a calcium chloride solution was added to 50.00 ~ 99.99 wt% of the concentrated aqueous silk fibroin solution and then uniformly mixed using a stirrer to form a mixed solution. Then, the mixed solution was charged into a flat container, and was then dried in a thermostatic chamber having a temperature of 25℃ and containing 50% of moisture to manufacture an artificial silk membrane (Hereinafter, referred to as “artificial silk membrane of the present invention”).

＜Experimental Example 1＞ Experiment on the structural characteristics and physical properties of artificial silk membrane

The thickness of the artificial silk membrane of the present invention was measured by a thickness meter, and the structure thereof was observed by FT-IR analysis.

The surface and section of the artificial silk membrane of the present invention were observed using a scanning electron microscope (SEM).

The tensile strength and extension rate of the artificial silk membrane of the present invention were measured using a tension tester.

＜Experimental Example 2＞ Experiment on cell culture and cytotoxicity

For the cytotoxicity test, L929 fiber embryo cells, purchased from ATCC, were inoculated in a MEM culture medium including 10% of cattle serum, 50 ㎍/ml of streptomycin and 100 U/ml of penicillin such that 10,000 cells were inoculated per well of the MEM culture medium, and then cultured for 24 hours.

The artificial silk membrane of the present invention was cut into a size of 1×1cm, and then 1 g of the silk membrane sample is introduced into 10 ml of culture medium. Thereafter, the silk membrane sample was eluted in a CO2 incubator at 37℃ for 24 hours.

The eluted sample continuously diluted, and was then treated with the previously cultured cells. The survival rate of cells was evaluated using an MTT method.

＜Result 1＞ Results of manufacture of artificial silk membrane

An artificial silk membrane manufactured only using silk fibroin was transparent and had a thickness of 300 ㎛ or less. However, the thickness of the artificial silk membrane of the present invention can be adjusted to 300㎛ or more or 500㎛ or more.

When the conventional artificial silk membrane manufactured by only silk fibroin has a thickness of 300 ㎛ or more, it may lose transparency which is an advantage thereof. However, the artificial silk membrane of the present invention may have both transparency and thickness.

＜Result 2＞ Results of experiment on the structural characteristics and physical properties of artificial silk membrane

As seen in Table 1 and FIG. 1, the artificial silk membrane of the present invention has flexibility, elasticity and suturing ability. Further, as seen in the sections and surfaces of FIG. 2 (the upper photographs of FIG. 2 show the section and surface of the conventional artificial silk membrane manufactured by only silk fibroin, and the lower photographs of FIG. 2 show the section and surface of the artificial silk membrane of Example 1), the artificial silk membrane of the present invention has smooth and even sections and surfaces as well as a thickness of 300㎛ or more.

The artificial silk membrane of the present invention was extended to 356.7%. As a result, the extension rate thereof was greatly improved.

Table 1

	Maxim load (N)	Maximum extended length (mm)	Maximum extension rate (%)
Artificial silk membrane manufactured by only silk fibroin (control)	42.4	2.96	14.8
Artificial silk membrane of the present invention (thick artificial silk membrane)	55.8	71.34	356.7

Further, as seen in FIGS. 3A and 3B, since the artificial silk membrane of the present invention has transparency, the surgical procedure and treatment of a neurosurgical operation can be safely carried out.

Further, as seen in FIG. 4, the artificial silk membrane of the present invention has excellent flexibility, and, as shown in FIG. 5, it maintains a suturing ability suitable for operations.

＜Result 3＞ Results of cytotoxicity test

The cytotoxicity test of the artificial silk membrane including calcium chloride and silk according to the present invention was carried out. The test showed that the survival rate of cells was nearly 100% regardless of the concentration of extracts.

Therefore, it can be seen that both silk and calcium chloride included in the artificial silk membrane of the present invention do not have cytotoxicity.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

An artificial silk membrane, comprising: silk fibroin; and a salt.
The artificial silk membrane according to claim 1, comprising: 50.00 ~ 99.99 wt% of the silk fibroin; and 0.01 ~ 50.00 wt% of the salt.
The artificial silk membrane according to claim 1, wherein the salt is any one selected from the group consisting of calcium chloride, sodium chloride, potassium chloride, and sodium acetate.
The artificial silk membrane according to claim 1, further comprising: more than 0 wt% but not more than 20 wt% of any one selected from the group consisting of carbon nanotubes and fiber.
The artificial silk membrane according to claim 1, further comprising: more than 0 wt% but not more than 30 wt% of any one selected from the group consisting of collagen, gelatin, chitin, chitosan, keratin, cellulose, fibronectin, elastin, fibrinogen, fibromodulin, laminin, tenascin, vitronectin, alginate, hyaluronic acid, silk protein and derivatives thereof, agarose, polylactic acid (PLA), polyglycolic acid (PGA), a copolymer (PLGA) of polylactic acid and polyglycolic acid, polycaprolactone (PCL), poly{poly(ethyleneoxide)terephthalate-co-butyleneterephthalate} (PEOT/PBT), polyphosphoester (PPE), polyphosphagen (PPA), polyanhydride (PA), polyorthoester (POE}, poly(propylene fumarate)-diacrylate (PPF-DA}, and poly(ethylene glycol) diacrylate (PEG-DA}.
The artificial silk membrane according to claim 1, further comprising: one or more selected from the group consisting of antibiotics, antiviral agents, bactericides, nucleic acids, peptides, and proteins.
The artificial silk membrane according to claim 1, wherein the artificial silk membrane has a tensile strength of 2 ~ 100 MPa.
The artificial silk membrane according to any one of claims 1 to 7, wherein the artificial silk membrane is used as an artificial cerebral dura mater or a biomembrane.
A method of manufacturing an artificial silk membrane, comprising the steps of:

1) mixing 0.01 ~ 50.00 wt% of a salt with 50.00 ~ 99.99 wt% of silk fibroin to prepare a mixed solution; and

2) pouring the mixed solution into a flat container and then drying the mixed solution to form an artificial silk membrane.
The method of manufacturing an artificial silk membrane according to claim 9, wherein the salt is any one selected from the group consisting of calcium chloride, sodium chloride, potassium chloride, and sodium acetate.
The method of manufacturing an artificial silk membrane according to claim 9, wherein, in step 2), the mixed solution is poured into a flat container and then dried in a thermostatic chamber having a temperature of 20~80℃ and containing 20~80% of moisture.
The method of manufacturing an artificial silk membrane according to claim 9, wherein the mixed solution dried in step 2) is crystallized.
The method of manufacturing an artificial silk membrane according to claim 12, wherein the crystallization of the dried mixed solution is conducted by charging the dried mixed solution into a hermetic container having a relative humidity of 80% or more and then annealing the mixed solution with water.
The method of manufacturing an artificial silk membrane according to claim 12, wherein the crystallization of the dried mixed solution is conducted by immersing the container charged with the dried mixed solution into a mixed solvent in which a hydrophilic polar solvent of four carbon atoms or less and distilled water are mixed in a weight ratio of 70~90 : 10~30.