INJECTABLE THERMOSENSITIVE PLURONIC HYDROGELS COUPLED WITH BIOACTIVE MATERIALS FOR TISSUE REGENERATION

AND PREPARATION METHOD THEREOF

TECHNICAL FIELD

The present invention relates to an injectable thermosensitive pluronic derivative hydrogel coupled with a biologically active material for tissue regeneration, and a preparation method thereof.

BACKGROUND ART

Tissue engineering is a new technology emerged during the progress of science, and is a study which integrates and applies science and technology with basic concepts of life science, engineering, medicine, etc.

Tissue engineering is an application study which has an objective to understand the correlation between the structure and the function of tissues of a living body, and to maintain, enhance or restore the functions of a human body by means of artificial tissues which are transplantable into the human body, so as to replace damaged tissues or organs by normal ones or to regenerate the same.

Tissue engineering techniques using hydrogels are largely divided into two categories.

In one technique, a necessary tissue is extracted from a patient's body, and cells are separated from the tissue. Then, the cell is proliferated via a culture to a necessary amount, mixed with an injectable hydrogel, and then directly injected into the human body. Alternatively, the cell is cultured in a hydrogel outside the human body and then injected into the human body. In this technique, the transplanted hydrogel is converted to a gel in the human body due to the body temperature, positioned at a specific site, and supplied with oxygen and nutrition by diffusion of the body fluid. If blood is supplied through a blood vessel which is extended into the human body, the cell is proliferated and differentiated to generate new tissues and organs. Then, the hydrogel is discharged outside the body or decomposed to disappear.

In the other technique, a hydrogel and a specific drug are mixed, and the resulting mixture is directly injected into a living body. The mixture is converted to a gel due to the body temperature, and the hydrogel is gradually decomposed, by which the drug is delivered to the body for a long time at a suitable concentration.

For studying tissue engineering, it is important to prepare thermosensitive hydrogels that can be converted to a gel at around the body temperature and that are similar to tissues of a living body. It is required that the hydrogels for regeneration of tissues of the human body be converted to a gel at around the body temperature while maintained as a sol at room temperature, and have an affinity to cells so that the cells can generate tissues having a three-dimensional structure within the hydrogels, and also function as a barrier between transplanted cells and host cells.

The representative polymer hydrogels having such thermosensitivity include Pluronic (P. Holmqvist et al., Int. J. Pharm., 194, 103, 2000), poly(N-isopropylacrylamide) (PNIPAAm) (M. Harmon et al., Macromolecules, 36, 1 , 2003), hyaluronic acid (HA) (M. Ogiso et al., J. Biomed. Mater. Res., 39, 3, 1998), linear polyethyleneglycol (PEG)-polylactic acid/glycolic acid copolymer (PLGA)- polyethyleneglycol (PEG) (B. Jeong et al., J. Biomed. Mater. Res., 50, 2, 2000), linear polyethlyeneglycol (PEG)-polylactic acid (PLA)- polyethyleneglycol (PEG), star-shaped polylactic acid (PLA)- polyethyleneglycol (PEG), star-shaped poly-ε-caprolactone (PCL)- polyethyleneglycol (PEG) (S. Zhao et al., J. Func. Polym., 15, 1 , 2002) etc. Among them, only hyaluronic acid, and F127 and F68 of Pluronics are approved by the U.S. FDA as materials that can be injected to the human body.

Polynipaam has its own toxicity. Other hydrogels are disadvantageous in that they have relatively low mechanical properties, and do not have an affinity to cells sufficient to be used for tissue regeneration.

The pluronic hydrogels include F38, F68, F77, F77, F98, F108, F127, etc. beginning with 'F', L31 , L42, L43, L44, L62, L72, L101 , etc. beginning with 'L', and P75, P103, P104, etc. beginning with 'P' (respectively denoting trade names). All of these pluronic hydrogels have a structure of PEO-PPO-PEO, but different ratios or forms from one another. Among them, only F68 (molecular weight: 8,700) and F127 (molecular weight: 12,600) were approved by the U.S. FDA have been used as materials for a living body.

Pluronic F127 is a non-toxic copolymer (molecular weight: 12,600) of

polyethyleneoxide (PEO)-polypropyleneoxide (PPO)-polyethyleneoxide (PEO) in a molar ratio of 98:68:98, and has a temperature-dependent sol-gel conversion properties, and accordingly, it has been used as a material, in a mixture with other materials, for a living body. However, there has been no example to synthesize a derivative by chemically coupling biologically active materials with pluronic F127.

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL PROBLEM TO BE SOLVED

Therefore, it is an object of the present invention to provide an injectable thermosensitive pluronic hydrogel for tissue regeneration, to which biologically active materials are coupled, and which has an excellent cell affinity while maintains the thermosensitivity of the conventional pluronic hydrogel itself.

TECHNICAL SOLUTION

To achieve the above object, the present invention provides an injectable pluronic hydrogel having thermosensitivity and cell affinity by coupling a conventional pluronic polymer with a compound having a polymerizable double bond and a functional group, through which a biologically active material such as a ligand peptide or a growth factor can be introduced, while maintaining the thermosensitivity of the conventional pluronic polymer, followed by directly introducing a biologically active material

which can improve cell affinity. Herein, the polymerizable double bond can be later used for a polymerization, if desired.

Therefore, the present invention relates to an injectable thermosensitive pluronic hydrogel for tissue regeneration, and a preparation method thereof.

The injectable thermosensitive pluronic hydrogel for tissue regeneration according to the present invention has a structure in which a thermosensitive pluronic F127 polymer is coupled with a biologically active material such as a ligand peptide having a cell affinity or a growth factor through methacryloxyethyltrimellitic acid.

The ligand peptide having a cell affinity is at least one selected from the group consisting of Arg-Gly-Asp (RGD), Arg-Glu-Asp-Val (REDV), Leu-Asp-Val (LDV), Tyr-lle-Gly-Ser-Arg (YIGSR), Pro-Asp-Ser-Gly-Arg (PDSGR), Ile-Lys-Val-Ala-Val (IKVAV) and Arg-Asn-lle-Ala-Glu-lle-lle- Lys-Asp-Ala (RNIAEIIKDA). It has been known that RGD and PDSGR enhance adhesion of almost all cells, REDV and LDV enhance proliferation of vascular endotheliocytes, YIGSR enhance proliferation of vascular cells, and IKVAV and RNIAEIIKDA enhance proliferation of nerve cells.

The growth factor is at least one selected from the group consisting of a transforming growth factor (TGF-β), an insulin-like growth factor (IGF), an epithelia growth factor (EGF), a nerve cell growth factor (NGF), a vascular endothelial growth factor (VEGF), a fibroblast growth factor (FGF), a hepatocyte growth factor (HGF) and a platelet-derived growth factor (PDGF).

In the injectable thermosensitive pluronic hydrogel for tissue

regeneration according to the present invention, methacryloxyethyltrimellitic acid used for coupling pluronic F127 with a biologically active material is the one derived from 4-methacryloxyethyltrimellitic anhydride (4-META) or 2-methacryloxyethyltritrimellitic anhydride (2-META). The following Formula 1 shows a specific example of an injectable thermosensitive pluronic hydrogel (META-pluronic F127-R) for tissue regeneration according to the present invention, in which pluronic F127 is coupled with a biologically active material through 4-methacryloxyethyltritrimellitic anhydride.

Formula 1 :

wherein -PEO-PPO-PEO- represents pluronic F127, and R represents the biologically active material as defined above.

A preparation method for the injectable thermosensitive pluronic hydrogel for tissue regeneration according to the present invention comprises:

(1) reacting a thermosensitive pluronic hydrogel with methacryloxy- ethyltritrimellitic anhydride at room temperature to obtain methacryloxy- ethyltritrimellitic anhydride-pluronic polymer (META-pluronic F127); and

(2) coupling the obtained methacryloxyethyltritrimellitic anhydride-pluronic polymer with a ligand peptide having a cell affinity or a

growth factor to obtain a methacryloxyethyltritrimellitic anhydride-pluronic derivative hydrogel to which a biologically active material is coupled.

In step (1), the methacryloxyethyltritrimellitic anhydride may be 4-methacryloxyethyltritrimellitic anhydride (4-META) or 2-methacryloxyethyl- tritrimellitic anhydride (2-META). The 4-META which has been used as a conventional dental adhesive has no toxicity and a relatively excellent mechanical property. 4-META or 2-META has a double bond at its one end, so as to enable polymerization, and an anhydride group at the other end, capable of being converted to a carboxyl group which can be used to couple a biologically active material.

In step (1), pluronic F127 and META are put into a reactor in a molar ratio of 1 :2.2, the reactor is charged with nitrogen at room temperature, and then a reaction is performed for 20-24 hours, to obtain META-pluronic F127 which is a derivative of pluronic F127. In step (2), a biologically active material is added to the META-pluronic

F127 prepared in step (1) in a molar ratio of 1 :2.2, and then the resulting mixture is reacted using 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide (EDC) or 1 -cyclohexyl-3-(2-morpholinoethyl)carbodiimidemeto-p-toluene sulfonate (CMC), to obtain META-pluronic F127-R, wherein R represents a biologically active material as defined above.

In the present invention, 4-META having a double bond and a carboxyl group is coupled with the conventional thermosensitive pluronic F127 hydrogel, thereby enabling polymerization and introduction of a biologically active material. Furthermore, the introduction of a ligand peptide or growth

factor to META-pluronic F127 makes it possible to prepare an injectable thermosensitive hydrogel, a cell affinity of which is improved. Therefore, the pluronic hydrogels of the present invention is useful for regenerating tissues or organs by means of tissue engineering technique. The following Reaction Scheme 1 shows an example for preparing the injectable thermosensitive pluronic hydrogel according to the present invention, comprising coupling a biologically active material to a derivative of pluronic F127 using 4-methacryloxyethyltritrimellitic anhydride.

Reaction Scheme 1 :

Pluronic F127 4-META

META-Pluronic F127

META-Pluronic F127-R {R: Bioactive materials)

wherein R represents a biologically active material as defined above.

EFFECTS OF THE INVENTION

According to the present invention, 4-META or 2-META having a double bond to enable polymerization and a carboxyl group is coupled to the conventional thermosensitive pluronic F127 hydrogel to obtain META- pluronic F127, and then a biologically active material such as a ligand peptide or a growth factor is introduced to the obtained META-pluronic F127 hydrogel

to obtain an injectable thermosensitive pluronic hydrogel having excellent a cell affinity such as a cell proliferation and a cell differentiation, while maintaining the thermosensitivity of the conventional pluronic hydrogel. The injectable thermosensitive pluronic derivative hydrogel according to the present invention has an excellent cell affinity while maintaining the thermosensitivity of the conventional pluronic hydrogel, and thus, it can be suitably used for the regeneration of artificial tissues or organs through a topical injection using a syringe, without a surgical operation.

EXAMPLES

Hereinafter, the present invention will be illustrated in more detail with reference to the following examples. The following examples are provided merely to illustrate, not to limit the scope of the present invention thereto.

In the following examples, the thermosensitivity of the hydrogel was measured at 15-90 ⁰ C with a tube tilting method, and the size of the micelles was measured with a dynamic light scattering (DLS) while changing temperature. The critical micelle temperature (CMT) was measured at 10-60 ⁰ C with ultraviolet rays. Cell culture experiments were carried out by setting the concentration of the hydrogel according to the present invention to be 20% by weight. After culturing segmented tissue cells (cartilage cells, vascular cells, nerve cells, vascular endothelial cells, etc.) or stem cells (adipose stem cells, bone marrow stem cells, cord-blood stem cells, muscular stem cells, embryonic stem cells, etc.) were cultured, and cell proliferation and differentiation were observed, so as to evaluate an affinity to cells.

Example 1

Pluronic F127 having a weight average molecular weight of about

12,700 and 4-META were mixed in a molar ratio of 1 :2.2, and the resulting mixture was completely dissolved in toluene in a ratio of 1 :4 by weight. After charging the reactor with nitrogen gas in order to prevent contact with moisture, and the inlet of the reactor was sealed. Pyridine was added to the reactor using a syringe while stirring so as to have a ratio of 1 :25 by volume with the mixture. The resulting mixture was reacted at room temperature for 20-24 hours with stirring and then was poured into 1000ml of cold ether to precipitate.

The yield of the obtained META-pluronic F127 hydrogel was more than

90%, and according to the results of a sol-gel experiment, it was discovered that its thermosensitivity was maintained although the sol-gel transition temperature was lowered by approximately 2-3 ⁰ C compared with the conventional pluronic F127. The micelle size of the obtained META-pluronic

F127 hydrogels was increased by approximately 10nm compared with that of the conventional pluronic F127, and the critical micelle temperature was lowered by approximately 10 ⁰ C depending on its concentration compared with that of the conventional pluronic F127.

Example 2

META-pluronic F127 prepared in Example 1 was completely dissolved in 2-morpholinoethansulfonic acid (MES) buffer solution in a molar ratio of

1 :15 by weight, and then EDC was added to the resulting solution so as the molar ratio between META-pluronic F127 and the EDC to be 1 :2.1 , thereby activating carboxyl group. After stirring the mixture for 2 hours, RGD was added to the reaction mixture so as the molar ratio between META-pluronic F127 and RGD to be 1 :2.1. Then, the mixture was reacted at room temperature for 24 hours, dialyzed for 3 days, and then freeze-dried for 3 days.

The yield of the prepared META-pluronic F127-RGD hydrogesl was more than 90%, and according to the results of test for thermosensitivity, its thermosensitivity was maintained although the sol-gel transition temperature was lower compared with that of the conventional pluronic F127 by approximately 3-4 °C . The prepared META-pluronic F127 hydrogel exhibits the increase of micelle size compared with META-pluronic F127 by approximately 10-15nm depending on its concentration, and the critical micelle temperature was lowered compared with that of META-pluronic F127 by approximately 10-15 ^° C .

As a result of the test for adhesion to bone marrow cells, the prepared META-pluronic F127-RGD hydrogel exhibited an improvement of approximately 90% in cell affinity compared with the conventional thermosensitive pluronic F127 hydrogel.

Example 3

META-pluronic F127-YIGSR was prepared in the same manner as described in Example 2 except that RGD and EDC were replaced by YIGSR,

a ligand peptide relating to a vascular cell proliferation, and CMC. The yield of the prepared META-pluronic F127-YIGSR hydrogel was more than 90%, and its thermosensitivity was maintained although the sol-gel transition temperature was lower compared with the conventional pluronic F127 by approximately 3-4 ⁰ C . The prepared META-pluronic F127-YIGSR hydrogel exhibited increase of approximately 5-1 Onm in micelle size compared with META-pluronic F127-RGD depending on its concentration, and the critical micelle temperature was lowered compared with that of META-pluronic F127-RGD by approximately 5-10°C depending on its concentration. As a result of the test for proliferation of vascular cells, the prepared

META-pluronic F127-YIGSR exhibited an improvement of approximately 80% in cell affinity compared with the conventional pluronic F127.

Example 4 META-pluronic F127-IKVAV was prepared in the same manner as described in Example 2 except that IKVAN, a ligand peptide relating to a nerve cell proliferation, instead of RGD, was used. The yield of the prepared META-pluronic F127-IKVAV hydrogel was more than 90%, and its thermosensitivity was maintained although the sol-gel transition temperature was lower compared with the conventional pluronic F127 by approximately 3-5°C . The prepared META-pluronic F127-IKVAV hydrogel exhibited increase of approximately 5-1 Onm in micelle size compared with META-pluronic F127-RGD depending on its concentration, and the critical micelle temperature was lowered compared with that of the conventional pluronic

F127-RGD by approximately 5-10 ⁰ C depending on its concentration.

As a result of the test for proliferation of nerve cells, the prepared META-pluronic F127-IKVAV hydrogel exhibited an improvement of approximately 90% in cell affinity compared with the conventional pluronic F127 hydrogel.

Example 5

META-pluronic F127-REDV was prepared in the same manner as described in Example 2 except that REDV, a ligand peptide relating to an intravascular cell proliferation, instead of RGD, was used. The yield of the prepared META-pluronic F127-REDV hydrogel was more than 90%, and its thermosensitivity was maintained although the sol-gel transition temperature was lower compared with the conventional pluronic F127 by approximately 2-3 ^° C. The prepared META-pluronic F127-REDV hydrogel exhibited increase of approximately 5-1 Onm in micelle size compared with META-pluronic F127-RGD depending on its concentration, and the critical micelle temperature was lowered compared with that of META-pluronic F127-RGD by approximately 5-10 ^° C depending on its concentration.

As a result of the test for proliferation of intravascular cells, the prepared META-pluronic F127-IKVAV hydrogel exhibited an improvement of approximately 80% in cell affinity compared with the conventional pluronic F 127 hydrogel.

Example 6

META-pluronic F127-TGF-β was prepared in the same manner as described in Example 2 except that TGF-β, a growth factor, was used instead of RGD. As a result of a sol-gel experiment, thermosensitivity of META-pluronic F127-TGF-β was similar to that of the conventional pluronic F127-hydrogel although the sol-gel transition temperature was lowered compared with the conventional pluronic F127 hydrogel by approximately 2-3 ^° C . The prepared META-pluronic F127- TGF-β exhibited increase of approximately 5-1 Onm in micelle size compared with META-pluronic F127-RGD depending on its concentration, and the critical micelle temperature was lowered compared with that of META-pluronic F127-RGD by approximately 5-1O ⁰ C depending on its concentration.

As a result of an experiment for the differentiation of chondrocyte using fat stem cells, META-pluronic F127-TGF-β exhibited an improvement in cell affinity in which its differentiation is approximately 90% higher than that of the conventional pluronic hydrogel.

Example 7

META-pluronic F127-EGF was prepared in the same manner as described in Example 6 except that EGF, a growth factor, was used instead of RGD and CMC was used instead of EDC. As a result of a sol-gel experiment, the thermosensitivity of META-pluronic F127-EGF was similar to that of the conventional pluronic F127 hydrogel although it was lowered compared with the conventional pluronic F127 hydrogel by approximately 2-3 ⁰ C. The prepared META-pluronic F127-EGF exhibited increase of approximately

5-1 Onm in micelle size compared with META-pluronic F127-RGD depending on its concentration, and the critical micelle temperature was lowered compared with that of META-pluronic F127-RGD by approximately 5-1O ⁰ C depending on its concentration. As a result of an experiment for the differentiation of osteocyte using cord-blood stem cells, META-pluronic F127-EGF hydrogel exhibited an improvement in cell affinity in which its differentiation is approximately 80% higher than that of the conventional pluronic hydrogel.

Example 8

META-pluronic F127-NGF was prepared in the same manner as described in Example 6 except that NGF, a growth factor, was used instead of RGD. As a result of a sol-gel experiment, the thermosensitivity of the obtained META-pluronic F127-NGF was similar to that of the conventional pluronic F127 hydrogel although it was lowered compared with the conventional pluronic F127 hydrogel by approximately 2-3 ⁰ C . The META-pluronic F127-NGF exhibited increase of approximately 5-1 Onm in micelle size compared with META- pluronic F127-RGD depending on its concentration, and the critical micelle temperature was lowered compared with that of META-pluronic F127-RGD by approximately 5-10 ⁰ C depending on its concentration.

As a result of an experiment for the differentiation of nerve cells using bone marrow stem cells, META-pluronic F127-NGF exhibited an improvement in cell affinity in which its differentiation is approximately 90% higher than that

of the conventional pluronic hydrogel.

Example 9

META-pluronic F127-VEGF was prepared in the same manner as described in Example 6 except that VEGF, a growth factor, was used instead of RGD. As a result of a sol-gel experiment, the thermosensitivity of the obtained META-pluronic F127-VEGF was similar to that of the conventional pluronic F127 hydrogel although it was lowered compared with the conventional pluronic F127 hydrogel by approximately 2-3 °C. The prepared META-pluronic F127-VEGF exhibited increase of approximately 5-1 Onm in micelle size compared with META- pluronic F127-RGD, and the critical micelle temperature was lowered than META-pluronic F127-RGD by approximately 5-10 °C .

As a result of an experiment for the differentiation of vascular endothelial cells using embryonic stem cells, META-pluronic F127-VEGF exhibited an improvement in cell affinity in which its differentiation was approximately 80% higher than that of the conventional pluronic hydrogel.

As described above, the pluronic hydrogel according to the present invention exhibits the increase of cell affinity to the specific cells or cell differentiation into the specific cells by approximately 80-90% compared the conventional pluronic F127 hydrogel, while it maintains the thermosensitivity of the conventional fluronic hydrogel. The puronic hydrogel according to the present invention exhibits increase in micelle size compared with the conventional pluronic F127 hydrogel by approximately 10-15nm depending on

its concentration, and the critical micelle temperature was lowered than the conventional pluronic F127 hydrogel by approximately 10-15 ^° C depending on its concentration.

It will also be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.