JP2008120888A - Biodegradable copolymer and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable copolymer which can be adapted to biological flexible tissues and has flexibility, to provide a method for producing the same, to provide a biodegradable copolymer cross-linked product obtained by further imparting an elastic dynamic characteristic (elastic deformation) to the biodegradable copolymer, and to provide a medical treatment material using the biodegradable copolymer and the biodegradable copolymer cross-linked product. <P>SOLUTION: This biodegradable copolymer obtained by copolymerizing ε-caprolactone with a reactive functional group-having cyclic depsipeptide. The biodegradable copolymer cross-linked product obtained by treating the biodegradable copolymer with a cross-linking agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a biodegradable copolymer having excellent biocompatibility and high flexibility, and a method for producing the same.

  With the innovation and diversification of medical technology, the importance of biodegradable polymers in the medical field is increasing, and degradation controlled drug delivery devices, sutures, bone fixation materials, hemostasis Applications such as adhesives and anti-adhesion membranes that require biodegradable absorbable polymers that can be broken down into non-toxic components in vivo and metabolized and absorbed are increasing. Among them, materials for tissue engineering (regenerative medicine) have attracted particular attention in recent years. In the GTR (guided tissue regeneration) method, which is a tissue engineering technique, cells are cultured using a biodegradable material as a scaffold, and the degradable polymer that provided the scaffold disappears as cells grow and form tissues. Aims to be replaced with normal tissue. (Non-Patent Document 1)

  In this way, medical biodegradable polymer materials can be used for a wide variety of purposes, and the physical properties (biodegradation rate, mechanical properties, bioadhesiveness, etc.) required for each application differ. Yes. For example, temporary substitutes for hard tissues such as bones require the same mechanical properties (hardness and toughness) as bone tissues, whereas materials used in contact with soft tissues such as organs, Flexibility that does not damage the organ when stressed is required. Further, the requirements for cell adhesion are completely opposite between the adhesion-preventing film and the tissue adhesive. Furthermore, the tissue engineering material is required to exhibit a degradation profile suitable for different cell growth rates depending on the target tissue.

  Furthermore, in order to enable recognition from the cell side by specific interaction, it is also an important requirement that chemical modification such as immobilization of a cell affinity ligand is possible. In other words, not only is biocompatibility and safety superior, it is desirable to be able to supply variations in biodegradable materials that satisfy different requirements in terms of biodegradation rate, mechanical and biochemical characteristics, and chemical reactivity. Yes.

  On the other hand, biological materials such as collagen, gelatin, and fibrin have been used as medical materials so far, but in recent years, infectious diseases such as bovine spongiform encephalopathy (BSE), Creutzfeldt-Jakob disease, AIDS, and hepatitis. Problems have arisen and it has become clear that natural products are not necessarily safe. There are many voices that manufacturers that provide medical materials make synthetic polymers ideal as materials that do not vary depending on the raw materials, are easy to control quality, and do not contain risk factors derived from living organisms. The biodegradable synthetic polymers that have been most frequently studied and used as medical materials so far are poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), and poly-DL-lactic acid (PDLLA). The copolymer is a polylactic acid polymer.

  Polylactic acid is a constituent of the body, lactic acid is a metabolite in the body, is highly safe, has relatively high biocompatibility, is highly crystalline, and can be set to high mechanical strength. The use of has been considered. PLLA, the most common polylactic acid, is synthesized by ring-opening polymerization of L-lactide or direct condensation of L-lactic acid, and has high crystallinity and high strength, so it can be used as a bone support plate and bone fixation screw. It has become. (Non-patent Document 2) However, because PLLA has high crystallinity, depending on the purpose of use, the degradation rate is too slow, and since it is hard and lacks flexibility, it has a drawback that it is poor in adaptability to soft tissues.

  Thus, for example, Patent Document 1 discloses a polymer comprising a sequence based on about 20 to 35 wt% ε-caprolactone and about 65 to 80 wt% glycolide and having a tensile strength of at least 30,000 psi and a Young's modulus of less than 350,000 psi. A sterilized surgical product comprising a molded body and a method for producing the polymer are disclosed. Since the glycolide-caprolactone copolymer disclosed in Patent Document 1 and a surgical product molded from the copolymer have excellent flexibility and mechanical strength, they are used as surgical sutures in the form of monofilaments. There are advantages you can do. However, they are hydrolyzed too quickly and degrade rapidly in vivo. Therefore, it is not satisfactory as a surgical suture or material for an affected part having a long healing period.

  In addition, as a lactide-caprolactone copolymer, for example, Patent Document 2 discloses a biodegradable medical product formed from a copolymer containing 95 to 65 mol% lactic acid units and 5 to 35 mol% caprolactone units. A molded article and a method for producing the same are disclosed. Since the copolymer and the medical molded article disclosed in Patent Document 2 have flexibility, there is an advantage that they can be used as a surgical suture in the form of a monofilament. However, since the mechanical strength is low and the decomposition rate in the living body is too slow, it is not preferable because it exists longer in the living body than necessary. It has already been found that materials that remain in the body for a long time cause many secondary diseases such as inflammation and carcinogenesis.

  Furthermore, the materials that have been developed so far have such low stretchability that it can be said that they have no ability to recover deformation such as tension and compression, and it has become a challenge today to modify this property. . In particular, in the medical field, development of materials having mechanical properties similar to those of tissues and organs in the living body is expected. It has been found that when an artificial material having a mechanical characteristic completely different from that of an organ in a living body is implanted, a biological reaction due to a difference in followability to expansion and contraction occurs in the living body. For example, in the case of an artificial blood vessel, the blood vessel in the living body expands and contracts due to blood pressure. However, in a conventional artificial blood vessel, a material having no stretchability causes a secondary strain at the anastomosis portion between the artificial blood vessel and the blood vessel. It has been found that a natural reaction is induced, and the development of a material having elasticity similar to that of blood vessels is also eagerly desired in a scaffold for revascularization using a biodegradable material. Since the same phenomenon occurs in other organs, the development of biodegradable materials having stretchable properties is expected.

  By the way, while maintaining or improving the excellent properties of polylactic acid polymers such as PLLA, attempts have been made to expand applications and control physical properties by chemical modification. For example, Non-Patent Documents 3 to 6 include polymer synthesis techniques such as random and block copolymerization with a cyclic comonomer having a functional group, a polymerization reaction using a functional molecule having a hydroxyl group as a starting species, and graft polymerization. Utilizing this, lactic acid copolymers having various molecular forms (random, block, graft, branched structure) and chemical properties (reactive functional groups, hydrophilicity / hydrophobicity) have been synthesized.

  Specifically, 1) depsipeptide-lactic acid / random copolymer having a reactive functional group on the side chain (Non-patent Documents 7 to 10), 2) depsipeptide-lactic acid / block copolymer having a reactive functional group on the side chain Polymers (Non-Patent Documents 11 to 12), 3) Comb-shaped polylactic acid (Non-Patent Documents 13 to 14), 4) Hyperbranched polylactic acid (Non-patent Document 15), 5) Polylactic acid grafted polysaccharide (Non-patent Document) 16-17) and the like are synthesized.

  As described above, various polylactic acid-based polymers have been developed. However, they have biocompatibility, can be easily chemically modified, can control biodegradation behavior as needed, and can be adapted to soft tissues. At present, a material having a degree of flexibility and stretchability has not been obtained yet.

  For example, surgical sutures are required not to be toxic in the body, to have moderate smoothness, and to have high knot strength. In order to impart these properties, for example, a suture comprising a bioabsorbable polymer such as a lactide or glycolide homopolymer or copolymer is used as a composition comprising a film-forming polymer such as polycaprolactone or ethylene oxide polymer. Sutures covered with (Patent Documents 3 and 4) have been proposed. However, taking the degradation period of a copolymer of polylactic acid and polycaprolactone as an example, polylactic acid alone takes nearly one year and polycaprolactone takes more than two years, so both copolymers are completely degraded in vivo. There was a problem that it took more than one year to do. As a result, there is also a problem that extraneous matter remains longer than the period necessary for normal wound healing. Furthermore, since neither polylactic acid nor polycaprolactone has a reactive functional group, there is a problem that it is difficult to modify the polymer function by chemical modification only with the copolymer of both.

  Another example is poly (depsipeptide-lactide) intended for use as a scaffold material for tissue engineering. Non-patent documents 18 and 19 propose a copolymer of carboxy side chain or amino side chain depsipeptide and lactic acid as a material. Due to the effects of these polar functional groups, cell adhesion by charging and three-dimensional cell adhesion have been studied. However, since polylactic acid is used, it has a property of lacking flexibility and stretchability, and there is a problem that sufficient soft tissue compatibility has not been achieved.

On the other hand, as a synthesis example of a compound having both biodegradability and elasticity, a dehydrated polycondensate of glycerin and sebacic acid described in Non-Patent Document 20 can be mentioned. In Non-Patent Document 20, the dehydrated polycondensate of glycerin and sebacic acid exhibits rubber elasticity, and at the same time, its cell adhesion, tissue compatibility, and biodegradability are studied. However, the production of this polymer requires a dehydration reaction under high temperature and reduced pressure conditions, and it is difficult to adjust the degree of cross-linking because a cross-linked product is created directly from the monomer. Little information about the monomers is available. The degradation rate after 60 days is about 17%, and it is difficult to say that the biodegradability is excellent.
JP 59-82865 JP-A 64-56055 Japanese Patent Publication No.2-12106 Japanese Patent Publication No. 5-53137 Langer R, et al: Tissue engineering. Science 1993, 260: 920-926, Freed LE, et al: J Biomed Mater Res 1993, 27: 11-23. Hidehito Tsuji et al .: Polylactic acid for medical treatment, pharmaceutical preparation and environment. Kyoto, Kobunshi Shuppankai, 1997, 149-160, edited by Biodegradable Plastics Study Group: Biodegradable Plastics Handbook. Tokyo, N. TS, 1995, 279-291, 666-730. Yuichi Oya: Present status and new development of biodegradable polymers. Artificial organ 1999, 28: 582-589 Yuichi Oya, Goro Ouchi: New polylactic acid polymers as biodegradable biomaterials. Polymer processing 1999, 48: 530 Yuichi Oya: Synthesis of a novel biodegradable polymer based on polylactic acid and its application as a biomaterial. Polymer Papers 2002, 59: 484-498 Ouchi Goro, Oya Yuichi: New polylactic acid-based medical materials. Future materials 2002, 2: 30-35. Ouchi T, et al: Macromol Chem Rapid Commun 1993, 14: 825-831. Ouchi T, et al: Macromol Chem Phys 1996, 197: 1833-1833. Ouchi T, et al: J Polym Sci Part A: Polym Chem 1997, 35: 377-383. Ouchi T, et al: J Poly Sci Part A: Poly Chem 1998, 36: 1283-1290. Ouchi T, et al: Designed Monom Polym 2000, 3: 279-287. Ouchi T, et al: J Polym Sci Part A: Polym Chem 2002, 40: 1218-1225. Tasaka F, et al: Macromolecules 1999, 32: 6386-6389 Tasaka F, et al: Macromolecules 2001, 34: 5494-5500. Tasaka F, et al: Macromol Rapid Commun 2001, 22: 820-824. Ohya Y, et al: Macromolecules 1998, 31: 4662-4665. Ohya Y, et al: Macromol Chem Phys 1998, 199: 2017-2022. Ohya Y, et al: J. MoI. Biomed. Mater. Res. , 65A, 79 (2003) Ohya Y, et al: J. MoI. Biomat. Sci. Polym. Edu. , 15, 111 (2004) Wang Y, et al: Nature Biotech. 20,602 (2002)

  An object of this invention is to provide the biodegradable copolymer provided with the softness | flexibility adaptable to a biological soft tissue, and its manufacturing method. Another object of the present invention is to provide a crosslinked biodegradable copolymer obtained by further imparting elastic mechanical properties (elastic deformation) to the biodegradable copolymer. Furthermore, it aims at providing the medical material using these biodegradable copolymer and biodegradable copolymer crosslinked material.

  As a result of intensive studies to solve the above problems, the present inventor has obtained a biodegradation obtained by copolymerizing a cyclic depsipeptide having a reactive functional group such as an amino group, a carboxyl group, or a hydroxyl group and ε-caprolactone. It was found that the sex copolymer has high flexibility as well as excellent biocompatibility and biodegradability. Moreover, it discovered that the biodegradable copolymer crosslinked material to which the elastic mechanical characteristic was provided is obtained by processing this biodegradable copolymer with a predetermined | prescribed crosslinking agent. Based on this knowledge, this has been further developed to complete the present invention.

  That is, the present invention provides the following degradable copolymer and degradable copolymer cross-linked product.

  Item 1. A biodegradable copolymer obtained by copolymerizing a cyclic depsipeptide having a reactive functional group and ε-caprolactone.

  Item 2. Item 2. The biodegradable copolymer according to Item 1, wherein the reactive functional group is an amino group.

  Item 3. Formula (A):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, n represents an integer of 1 to 10, x represents 2 to 100, y represents 10 to 1000, and x / (x + y) is 0.01. The arrangement of each unit of x and y is not limited to the order of the above arrangement.
Item 3. The biodegradable copolymer according to item 2, represented by:

Item 4. R ¹ in the general formula (A) represents a hydrogen atom, n represents 4, x represents 5 to 50, y represents 50 to 800, and x / (x + y) represents 0.02 to 0.30. Item 4. The biodegradable copolymer according to Item 3, wherein

  Item 5. Item 5. The biodegradable copolymer according to any one of Items 1 to 4, wherein the number average molecular weight (Mn) is 1,000 to 100,000.

  Item 6. Item 6. The biodegradable copolymer according to any one of Items 1 to 5, wherein the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) is 1.0 to 5.0.

  Item 7. Item 7. The biodegradable copolymer according to any one of Items 1 to 6, wherein the glass transition temperature is −60 to −10 ° C.

  Item 8. Item 8. The biodegradable copolymer according to any one of Items 1 to 7, which has a melting point of 30 to 80 ° C.

  Item 9. Item 9. The biodegradable copolymer according to any one of Items 1 to 8, wherein the heat of fusion is -70 to 0 J / g.

  Item 10. Item 10. The biodegradable coagulation according to any one of Items 1 to 9, wherein the number average molecular weight decreases by 20 to 90% in 28 days when the biodegradation behavior is immersed in a phosphate buffer solution (PBS) at 37 ° C. Polymer.

  Item 11. When the biodegradable copolymer is cut out into a dumbbell shape having a thickness of 0.2 to 0.5 mm, a width of 2.2 mm, a length of 18 mm, and a total length of 40 mm, and a tensile test is performed. Item 11. The biodegradable copolymer according to any one of Items 1 to 10, wherein the breaking strength is 5 to 20 MPa, the Young's modulus is 50 to 350 MPa, and the strain at break is 100 to 600%.

  Item 12. Item 12. A crosslinked biodegradable copolymer obtained by treating the biodegradable copolymer according to any one of Items 1 to 11 with a crosslinking agent.

  Item 13. Item 13. The biodegradable copolymer crosslinked product according to Item 12, wherein the crosslinking agent is a polyisocyanate.

  Item 14. Item 13. The biodegradable copolymer crosslinked product according to Item 12, wherein the crosslinking agent is an aliphatic polyisocyanate and / or an alicyclic polyisocyanate.

  Item 15. Item 12. A medical material comprising the biodegradable copolymer according to any one of Items 1 to 11.

  Item 16. Item 15. A medical material comprising the biodegradable copolymer crosslinked product according to any one of Items 12 to 14.

  Item 17. Formula (A):

(Wherein R ¹ is a hydrogen atom or a methyl group, n is an integer of 1 to 10, x is 2 to 100, y is 10 to 1000, and x / (x + y) is 0.01 to 0. .90, and the arrangement of each unit of x and y is not limited to the order of the arrangement described above.)
A biodegradable copolymer represented by the general formula (3):

(In the formula, Z represents a benzyloxycarbonyl group, and R ¹ , n, x and y are the same as above.)
A process for reacting a compound represented by the formula with a debenzyloxycarbonyl agent.

  The biodegradable copolymer of the present invention can be obtained by copolymerizing a cyclic depsipeptide having a reactive functional group derived from an amino acid component and ε-caprolactone at a specific composition ratio. As a result, the degradation rate of polycaprolactone, which has conventionally been slow in biodegradation, can be improved, and high flexibility that is not found in polydepsipeptides is imparted. Taking advantage of this flexibility, it is also useful as a medical material such as a tissue regeneration scaffold.

  In addition, since a reactive functional group is introduced into the biodegradable copolymer, it can be chemically modified, and a crosslinked product rich in elasticity can be obtained by crosslinking treatment. The crosslinked body is used as a medical material such as a tissue regeneration scaffold material that is particularly required to have elasticity.

  Furthermore, the degradation rate can be easily adjusted by copolymerizing cyclic depsipeptide and ε-caprolactone at a specific composition ratio.

1. Biodegradable copolymer The biodegradable copolymer of the present invention is obtained by copolymerizing a cyclic depsipeptide having a reactive functional group such as an amino group, a carboxyl group, or a hydroxyl group with ε-caprolactone.

  Depsipeptide generically means a copolymer of α-amino acid and α-hydroxy acid. The α-amino acid has a reactive functional group in the side chain, and examples of the reactive functional group include a carboxyl group, an amino group, a hydroxyl group, and a thiol group, and an amino group is particularly preferable. Polydepsipeptides include random and block copolymers of the α-amino acid and α-hydroxy acid (eg, lactic acid, glycolic acid, etc.), and the α-amino acid and α-hydroxy acid (eg, lactic acid, glycolic acid, etc.). ) And an alternating copolymer.

  Specifically, the general formula (A):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, n represents an integer of 1 to 10, x represents 2 to 100, y represents 10 to 1,000, and x / (x + y) is 0. And the arrangement of each unit of x and y is not limited to the order of the arrangement.).

R ¹ represents a hydrogen atom or a methyl group, preferably a hydrogen atom. When R ¹ is a methyl group, the carbon atom to which the methyl group is bonded can be an asymmetric carbon. In the copolymer of the present invention, the configuration of the asymmetric carbon may be (R) isomer, (S) isomer, or a mixture thereof.

  Although n shows the integer of 1-10, Preferably it is an integer of 1-5, More preferably, it is 4.

In general formula (A), x and y represent the average number of each unit in the copolymer, and are determined from ¹ HNMR and GPC. For example, in the copolymer of n = 4 in the general formula (A), NMR peak δ (ppm) due to the side chain portion of the cyclic depsipeptide unit: 2.95-3.17 (2H, -CH ₂ CH ₂ CH ₂ CH ₂ NH ₂ ) and NMR peak δ (ppm) due to caprolactone unit: 2.25-2.34 (2H, -CO CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ OH) Then, x and y are obtained from this value and the molecular weight of the main chain obtained by GPC.

  Further, as described above, the arrangement of each unit of x and y may be random or block.

  x is 2 to 100, preferably 5 to 50, and more preferably 10 to 30.

  y is 10 to 1,000, preferably 50 to 800, and more preferably 100 to 500.

  x / (x + y) is 0.01-0.90, preferably 0.02-0.30, more preferably 0.04-0.20. When x is in this range, biodegradability and tissue compatibility are imparted to the copolymer of the present invention, and flexibility is imparted.

  The copolymer of the present invention has a number average molecular weight (Mn) of 1,000 to 100,000, preferably 5,000 to 100,000, more preferably 10,000 to 50,000, and a weight average molecular weight (Mw). ) Is 1,000 to 300,000, preferably 5,000 to 300,000, more preferably 10,000 to 150,000. Further, the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight, which is an index of molecular weight distribution, is 1.0 to 5.0, preferably 1.0 to 4.0, more preferably 1.0 to 3. .8. The number average molecular weight and the weight average molecular weight can be measured using a known method such as GPC (solvent: dimethylformamide).

  The glass transition temperature of the copolymer of the present invention is −60 to −10 ° C., preferably −50 to −30 ° C. The melting point is 30 to 80 ° C, preferably 30 to 50 ° C. The heat of fusion is -70 to 0 J / g, preferably -55 to 0 J / g.

  As the biodegradation behavior of the copolymer of the present invention, when it is immersed in a phosphate buffered water solution (PBS) at 37 ° C., the decrease rate of the number average molecular weight in 28 days is 20 to 90%, preferably 60 to 90. %. The number average molecular weight is measured using GPC.

  When the thickness of the test site of the copolymer of the present invention is 0.2 to 0.5 mm, the width is 2.2 mm, the length is 18 mm, and the test piece is 40 mm in length, cut into a dumbbell shape, and this is subjected to a tensile test. The breaking strength is 5 to 20 MPa, preferably 5 to 10 MPa, the Young's modulus is 50 to 350 MPa, preferably 50 to 100 MPa, and the strain at break is 100 to 600%, preferably 300 to 600%.

  The biodegradable copolymer of the present invention can be produced, for example, as follows.

(In the formula, Z represents a benzyloxycarbonyl group, and R ¹ , n, x and y are the same as above.)
The compound represented by the above (1) can be produced according to, for example, T. Ouchi, et. Al., Macromol. Chem. Phys. 197, 1823-1833 (1996), etc. ) Is represented by a commercially available product.

  The compound represented by the above (1) and (2) is subjected to ring-opening polymerization using a catalyst (such as tin 2-ethylhexanoate) to obtain the compound represented by the above (3), which is debenzyloxycarbonyl The biodegradable copolymer represented by the above (A) can be obtained by conversion to a free amino group by an agent (for example, HBr / acetic acid or the like). Each step of this reaction can be carried out using a conventional method.

2. Cross-linked biodegradable copolymer Furthermore, a cross-linked biodegradable copolymer having elasticity can be produced by treating the biodegradable copolymer with a crosslinking agent.

  When the reactive functional group of the biodegradable copolymer is an amino group, examples of the crosslinking agent include polyisocyanates and polycarboxylic acid active esters.

  Examples of the polyisocyanates include aliphatic polyisocyanates and alicyclic polyisocyanates.

  Examples of the aliphatic polyisocyanate include diisocyanate [trimethylene diisocyanate, tetramethylene diisocyanate, 1,6-diisocyanatohexane (hexamethylene diisocyanate, HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2- Butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl captroate etc.], polyisocyanate [ Lysine ester triisocyanate, 1,4,8-triisocyanate octane, 1,6,11-triisocyanate undecane, 1,8-diisocyanate-4-isocyanate DOO methyl octane, 1,3,6-triisocyanate hexane, 2,5,7-trimethyl-1,8-diisocyanate-5-isocyanatomethyl octane] can be exemplified.

  Examples of the alicyclic polyisocyanate include diisocyanate [1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl. Cyclohexane (isophorone diisocyanate, IPDI), 4,4'-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 1,3- or 1,4-bis (isocyanate) Methyl) cyclohexane etc.], polyisocyanate [1,3,5-triisocyanatecyclohexane, 1,3,5-trimethylisocyanatecyclohexane, 2- (3-isocyanate) (Lopyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 2- (3-isocyanatopropyl) -2,6-di (isocyanatomethyl) -bicyclo (2.2.1) Heptane, 3- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3- Isocyanatopropyl) -bicyclo (2.2.1) heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- ( 2-Isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) -he Tan, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanate propyl) - bicyclo (2.2.1) heptane, etc.] can be exemplified. These polyisocyanates can be used alone or in combination of two or more.

  As the polycarboxylic acid active esters, the following formula is represented in the molecule:

The compound which has at least 2 or more active ester represented by these is illustrated.

  Specific examples include dicarboxy oligos and polyethylene glycols whose both ends are activated with N-hydroxysuccinimide (NHS) represented by the following formula.

(In the formula, p represents an integer of 1-5, and q represents an integer of 1-1000.)
The crosslinking reaction proceeds by reacting the biodegradable copolymer and the crosslinking agent in a solvent. The ratio of the crosslinking agent to the biodegradable copolymer is such that the active site of the crosslinking agent (for example, isocyanate group of polyisocyanate) is 0.5 to 1 with respect to 1 equivalent of amino group in the biodegradable copolymer. 0.5 equivalent, preferably 1.0-1.2 equivalent.

  As the reaction solvent, for example, DMF, DMSO, chloroform and the like are used. The reaction temperature is usually room temperature, and the reaction time is usually about 12 to 48 hours.

  After completion of the reaction, the sample is washed with a solvent (for example, methanol, chloroform, etc.) and then dried to obtain a crosslinked product.

  The glass transition temperature of the crosslinked product of the present invention is −50 to −20 ° C., preferably −45 to −30 ° C. Moreover, although melting | fusing point should just be 30-50 degreeC, what does not show melting | fusing point is preferable. The heat of fusion is -50 to 0 J / g, preferably -10 to 0 J / g.

  As the biodegradation behavior of the crosslinked product of the present invention, when immersed in a phosphate buffer solution (PBS) at 37 ° C., the decrease rate of the test piece weight on the 28th is 10 to 60%, preferably 30 to 50%. is there.

  The test piece of the cross-linked body of the present invention was cut into a dumbbell shape having a thickness of 0.2 to 0.5 mm, a width of 2.2 mm, a length of 18 mm, and a total length of 40 mm, and fractured when subjected to a tensile test. The strength is 1 to 30 MPa, preferably 1 to 12 MPa, the Young's modulus is 1 to 150 MPa, preferably 1 to 5 MPa, and the strain at break is 100 to 1000%, preferably 250 to 800%.

3. Applications The biodegradable copolymer of the present invention has biodegradability and flexibility, and the biodegradation rate can be adjusted by controlling the copolymer composition. The crosslinked biodegradable copolymer of the present invention has biodegradability, stretchability, flexibility and elasticity.

  The material obtained by the present invention can be molded into a film, thread, or sponge, and a biodegradable material having flexibility and elasticity can be developed. In particular, a biodegradable material having rubber elasticity can be developed for the crosslinked body. These can be applied as, for example, medical materials and medical products, electrical appliances, general shaped articles typified by furniture, plastic bottles, containers for general food and drink industries typified by prepared food containers, and the like.

  The material of the present invention can be suitably used as a medical material (material). For example, in vivo indwelling materials used for regeneration of soft tissues and tissues that require elasticity such as blood vessels and muscles (myocardium, skeletal muscle, smooth muscle, etc.) are highly mechanically compatible. Useful as. For example, biodegradable implant materials, tissue regeneration scaffold materials, wound coverings around movable sites, and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

In the following, “G” represents glycolic acid, “K” represents lysine, “CL” represents ε-caprolactone, and “r” represents random.
[Example 1]
Synthesis of poly (ε-caprolactone-depsipeptide) random copolymer (1) Place 1000 mg (3.12 mmol) of cyclo [Glc-Lys (Z)] in a 100 ml eggplant-shaped flask and freeze it using liquid nitrogen Drying was performed. In a 115 ° C oil bath, cyclo [Glc-Lys (Z)] is once melted, followed by 6,778 mg (59.4 mmol) of ε-caprolactone and 25.3 mg (62.5 μmol, M / I = 1,000) of 2- After adding ethyl ethylhexanoate and repeating deaeration and argon substitution for about 20 sets, a polymerization reaction was performed for 6 hours. Here, a cyclodepsipeptide cyclo [Glc-Lys (Z)] introduction rate of 15 mol% is assumed.

  After a predetermined time, the reaction mixture was dissolved in a small amount of chloroform and precipitated in a large amount of diethyl ether / methanol mixed solvent (9/1). The precipitate was collected and dried under reduced pressure for 24 hours to obtain 7,250 mg of a white solid [PGK (Z) -r-CL].

FIG. 1 shows ¹ H NMR (CDCl ₃ ) of the compound [PGK (Z) -r-CL] (Before deprotection).
(2) 2,000 mg of the compound [PGK (Z) -r-CL] obtained in (1) above is dissolved in 5 ml of trifluoroacetic acid, and 2.20 ml (3 equivalents to the protecting group) under ice-cooling. Of 25% -HBr / CH ₃ COOH was added and stirred for 1 hour. The reaction mixture was precipitated in cold diethyl ether, and the collected precipitate was dried under reduced pressure for 24 hours to obtain a brown solid. The obtained polymer was dissolved in 5 ml of chloroform, desalted with 1.22 ml (3 equivalents to the protecting group) of triethylamine, and precipitated in a cold diethyl ether / methanol mixed solvent (9/1). The precipitate was collected and dried under reduced pressure for 24 hours to obtain 1,530 mg of a white solid [PGK-r-CL]. FIG. 1 shows ¹ H NMR (CDCl ₃ ) of the compound [PGK-r-CL] (After deprotection).

  From FIG. 1, it was x = 19 and y = 408.

¹ H NMR (CDCl ₃ ), δ (ppm); 1.38 (2H, -COCH ₂ CH ₂ C H ₂ CH ₂ CH ₂ OH), 1.57-1.72 (4H, -COCH ₂ C H ₂ CH ₂ C H ₂ CH ₂ OH), 1.78-1.92 (6H, -C H ₂ C H ₂ C H ₂ CH ₂ NH ₂ ), 2.25-2.34 (2H, -COC H ₂ CH ₂ CH ₂ CH ₂ CH ₂ OH), 2.95-3.17 (2H, -CH ₂ CH ₂ CH ₂ C H ₂ NH ₂ ), 3.95-4.07 (2H, -COCH ₂ CH ₂ CH ₂ CH ₂ C H ₂ OH), 4.08-4.16 (1H, -COC H (CH ₂ ) ₃ NHCOCH ₂ O-), 4.48-4.75 (2H, -COCH (CH ₂ ) ₃ NHCOC H ₂ O-).

[Examples 2 to 4]
Copolymers were obtained by reacting in the same manner as in Example 1 except that the cyclodepsipeptide cyclo [Glc-Lys (Z)] introduction rate was changed to 10, 15, and 20 mol%. In this case, the values of (x, y) were (21,230), (29,177), and (21,127), respectively.

[Comparative Example 1]
Polycaprolactone (PCL) was obtained by reacting in the same manner as in Example 1 except that the cyclodepsipeptide cyclo [Glc-Lys (Z)] introduction rate was 0 mol%.

[Test Example 1]
Molecular weight measurement The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the copolymer (PGK-r-CL) of Examples 1 to 4 and PCL of Comparative Example 1 were subjected to gel filtration chromatography (TOSOH, Tosoh GPC). -8020 series system). The results are shown in Table 1. 3 mg of the polymer was dissolved in 0.5 ml of DMF, and this was passed through a 0.2 μm pore filter to remove solids such as dust, and then it was driven into the apparatus using a syringe.

[Test Example 2]
Thermal analysis test (DSC)
Thermal analysis of the copolymer [PGK-r-CL] of Examples 1 to 4 and PCL of Comparative Example 1 was performed as follows. 5 mg of polymer was weighed and placed in an aluminum pan, which was placed in a DSC apparatus and measured. Measurement temperature range: −100 to 100 ° C., heating rate: 10 ° C./min, cooling uses liquid nitrogen. Heat of fusion: ΔH (J / g) was calculated from the area of the melting point peak. The crystallinity: Xc (mol%) was determined by the formula: Xc = ΔH / ΔHtheo. × 100 (ΔHtheo. = 142 [J / g]).

  The results are shown in Table 2 and FIG.

  From this result, it was found that as the introduction rate of cyclodepsipeptide unit increased, the glass transition point and melting point decreased, the heat of fusion decreased, and the crystallinity decreased.

[Test Example 3]
Biodegradability test of PGK-r-CL and PCL
A cast film prepared from PGK-r-CL and PCL was cut out to 20mm x 5mm, weighed, and a small piece of these films was immersed in PBS (pH = 7.4, I = 0.14) prepared in advance at 37 ° C. . After a predetermined time (1, 2, 4, 7, 14, 28 days), the film was taken out, washed with ultrapure water and freeze-dried, and then the weight of the film was measured to calculate the weight reduction rate. The film was dissolved and the molecular weight reduction rate (solvent: DMF) was measured by GPC to confirm the biodegradation behavior.

  From this, it was confirmed that the biodegradability rate was increased when the depsipeptide introduction rate was increased. This is due to an increase in the proportion of hydrophilic and fast biodegradable depsipeptide moieties in the main chain and the decrease in crystallinity shown above. It is thought to be a thing. The results are shown in FIG.

[Test Example 4]
Tensile test of PGK-r-CL and PCL The tensile test of the copolymer obtained in Examples 1 and 2 was performed. Specifically, PGK-r-CL film and PCL film are cut out in a dumbbell shape with a test site thickness of 0.2 to 0.5 mm, a width of 2.2 mm, a length of 18 mm, and a test piece length of 40 mm. The tensile test was conducted at 5 mm / min.

  The results are shown in Table 3 and FIG.

  According to this, even if a depsipeptide is introduced into the molecular chain, the flexibility of PCL is not lost, but it is rather easy to deform.

[Example 5]
Preparation of cross- linked product using poly (ε-caprolactone-depsipeptide) / random copolymer In the cross- linking reaction, the amount of the cross-linking agent was adjusted so that all amino groups contained in the main chain were reacted. In the case of PGKCL (GK / CL = 4/96), first, 300 mg of PGKCL was dissolved in dehydrated DMF so as to be 20 wt%, and then 16.0 μl of hexamethylene diisocyanate (0.5 equivalent to the amino group) After irradiating with ultrasonic waves for 30 minutes, the crosslinking reaction was allowed to proceed at room temperature. After substituting the solvent from DMF to chloroform and methanol, a crosslinked product was obtained by drying under reduced pressure for 48 hours. A schematic diagram of the crosslinked product is shown in FIG.

[Examples 6 and 7]
The PGKCL (GK / CL = 9/91) and PGKCL (GK / CL = 14/86) obtained in Examples 2 and 3 were reacted in the same manner as in Example 5 to obtain copolymer crosslinked products (Examples). 6 and 7) were obtained.

[Test Example 5]
Thermal analysis test (DSC)
About the crosslinked body of Examples 5-7, it carried out similarly to the said Test example 2, and conducted the thermal analysis test. The results are shown in Table 4. Moreover, the photograph which shows the external appearance of each sample is shown in FIG.

  The heat of fusion: ΔH (J / g) and the crystallinity: Xc (mol%) were determined in the same manner as in Test Example 2.

  According to this, compared with the polymer before cross-linking (Examples 1, 2 and 3 in Table 2), the glass transition point is not much changed, but the melting point is slightly lowered and the heat of fusion is greatly reduced. I understood that. In particular, in Example 7 where the introduction rate of depsipeptide units was high, it was found that the melting point disappeared and non-crystallinity was exhibited.

[Test Example 6]
Tensile test About the crosslinked body obtained in Examples 5-7, the tensile test was done as follows.

  500 mg of poly {(Glc-Lys) -random-CL} was dissolved in 5 ml of DMF and cast into a Teflon (registered trademark) petri dish. 16 μl of hexamethylene diisocyanate was added thereto, and the crosslinking reaction was allowed to proceed at room temperature for 24 hours. After substituting the solvent from DMF to chloroform and methanol, it was dried under reduced pressure for 48 hours to obtain a crosslinked film having a thickness of 250 μm.

  The prepared crosslinked film was cut into a dumbbell shape having a thickness of 0.2 to 0.5 mm, a width of 2.2 mm, a length of 18 mm, and a total length of 40 mm, and a tensile test was performed at 1 mm / min. It was.

  The results are shown in Table 5 and the stress-strain curve in FIG. The crosslinked films of Examples 6 and 7 had no yield point and exhibited elastic deformation. The elongation at break was 255-711% and the Young's modulus was as low as 2-5 MPa, indicating that the film was flexible and tenacious.

  In addition, the crosslinked film recovers to its original shape even after stress such as pulling and twisting (shape recovery rate 91.6%), so this crosslinked film has a wide range of elastic properties. It was shown to have. The behavior is shown in FIG. It was found that the obtained crosslinked product exhibited a function (elastic deformation) as an elastomer.

[Test Example 7]
Cross-linked biodegradability test
Cross-linked PGKCL (14/86) was prepared in the form of a film, this film was cut out to 20mm x 5mm, weighed, and small pieces of these films were prepared in PBS (pH = 7.4, I = 0.14). After a predetermined time (1, 2, 4, 7, 14, 28, 42 days), the film was taken out, washed with ultrapure water and freeze-dried, and then the weight of the film was measured to calculate the weight reduction rate. The results are shown in FIG.

  Similarly, an uncrosslinked PGKCL (14/86) film and a polycaprolactone (PCL) film were also tested. The result is shown in FIG.

  From FIG. 9, it was found that the crosslinked product had a slower degradation rate than the uncrosslinked polymer, but this was due to the influence of crosslinking, and it was found that elution as a water-soluble low-molecular oligomer was inhibited. It was.

¹ H NMR (CDCl ₃ ) of compound [PGK (Z) -r-CL] and compound [PGK-r-CL] are shown. The result of the thermal analysis test of the copolymer [PGK-r-CL] of Examples 1-4 and PCL of the comparative example 1 is shown. The result of the biodegradability test of PGK-r-CL and PCL is shown. The result of the tensile test of PGK-r-CL and PCL is shown. The schematic diagram of the crosslinked body of Example 5 is shown. The external appearance photograph of the crosslinked body of Examples 5-7 is shown. The result of the tensile test of a crosslinked body is shown. It is a photograph which shows that a crosslinked body film has the mechanical characteristic which can be expanded-contracted. The result of the biodegradability test of a crosslinked body film, an uncrosslinked body film, and a PCL film is shown.

Claims (17)

  A biodegradable copolymer obtained by copolymerizing a cyclic depsipeptide having a reactive functional group and ε-caprolactone.   The biodegradable copolymer according to claim 1, wherein the reactive functional group is an amino group. Formula (A):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, n represents an integer of 1 to 10, x represents 2 to 100, y represents 10 to 1000, and x / (x + y) is 0.01. The arrangement of each unit of x and y is not limited to the order of the above arrangement.
The biodegradable copolymer of Claim 2 represented by these. R ¹ in the general formula (A) represents a hydrogen atom, n represents 4, x represents 5 to 50, y represents 50 to 800, and x / (x + y) represents 0.02 to 0.30. The biodegradable copolymer according to claim 3, wherein   The biodegradable copolymer according to any one of claims 1 to 4, wherein the number average molecular weight (Mn) is 1,000 to 100,000.   The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight is 1.0 to 5.0, The biodegradable copolymer according to any one of claims 1 to 5.   The biodegradable copolymer according to any one of claims 1 to 6, which has a glass transition temperature of -60 to -10 ° C.   Melting | fusing point is 30-80 degreeC, The biodegradable copolymer in any one of Claims 1-7.   The biodegradable copolymer according to any one of claims 1 to 8, wherein the heat of fusion is -70 to 0 J / g.   The biodegradability according to any one of claims 1 to 9, wherein when the biodegradation behavior is immersed in a phosphate buffer solution (PBS) at 37 ° C, the number average molecular weight decreases by 20 to 90% in 28 days. Copolymer.   When the biodegradable copolymer is cut out into a dumbbell shape having a thickness of 0.2 to 0.5 mm, a width of 2.2 mm, a length of 18 mm, and a total length of 40 mm, and a tensile test is performed. The biodegradable copolymer according to any one of claims 1 to 10, which has a breaking strength of 5 to 20 MPa, a Young's modulus of 50 to 350 MPa, and a strain at break of 100 to 600%.   A crosslinked biodegradable copolymer obtained by treating the biodegradable copolymer according to any one of claims 1 to 11 with a crosslinking agent.   The biodegradable copolymer crosslinked product according to claim 12, wherein the crosslinking agent is a polyisocyanate.   The biodegradable copolymer crosslinked product according to claim 12, wherein the crosslinking agent is an aliphatic polyisocyanate and / or an alicyclic polyisocyanate.   The medical material containing the biodegradable copolymer in any one of Claims 1-11.   The medical material containing the biodegradable copolymer crosslinked material in any one of Claims 12-14. Formula (A):

(Wherein R ¹ is a hydrogen atom or a methyl group, n is an integer of 1 to 10, x is 2 to 100, y is 10 to 1000, and x / (x + y) is 0.01 to 0. .90, and the arrangement of each unit of x and y is not limited to the order of the arrangement described above.)
A biodegradable copolymer represented by the general formula (3):

(In the formula, Z represents a benzyloxycarbonyl group, and R ¹ , n, x and y are the same as above.)
A process for reacting a compound represented by the formula with a debenzyloxycarbonyl agent.

Images