KR100346577B1 - Carrier specific to liver cell and the carrier-DNA conujugate - Google Patents

Abstract

The present invention relates to a cationic polymer compound (GCD) carrier prepared by introducing galactose group specifically binding to an asialoglycolic protein receptor of hepatocytes into chitosan and dextran for improving stability in an aqueous solution, and a complex of the carrier and DNA . GCD / DNA complexes were transfected only into hepatocytes and Hep G2 cells in the presence of an asialoglycoprotein receptor on the cell surface, and there was a specific interaction between the ASGR of the cell and the ligand of chitosan .

Description

The present invention relates to a hepatocyte-specific carrier and a complex thereof with DNA {Carrier specific to liver cell and the carrier-DNA conjugate}

The present invention relates to a DNA carrier specifically binding to a hepatocyte and a complex thereof with DNA, and more particularly, to a DAN carrier having high biocompatibility and high specificity for binding to hepatocytes, DNA complexes.

DNA can be introduced into living organisms as a body of living organisms to express a trait, and recently it is attracting attention as a new drug because it can treat genetic defects of major metabolizing enzymes. However, such a DNA material is susceptible to hydrolysis in the living body and has a low efficiency of putting it into a cell. To solve these problems, a drug delivery system (DDS) has been studied in which a DNA having a specific nucleotide sequence is transferred into a cell using a DNA carrier in order to put the gene therapy into practical use.

Among viral vectors that have been used as delivery systems in clinical trials until recently, viral vectors have been used because of their high transfection efficiency. However, this is not only complicated to manufacture, but also poses a problem of safety such as immunogenicity, possibility of infection, inflammation and the like, and now, nonviral carriers are in the spotlight.

Among the nonviral carriers, the most frequently used liposomes are mainly positive liposomes, for example, N - [1- (2,3-diol loxyoxy) propyl] -N, N, N -trimethylammonium chloride (DOTMA) USA, 84 , 7314 (1987)), alkylammonium (P. Pinnaduwage et al., &Quot; Use of Lipofection: A highly efficient, lipid-mediated DNA-transfection procedure ", Proc. Natl. Acad. Biochem. Biophys. Acta, 985 , 33 (1989)), cationic cholesterol derivatives (H. Farhood et al., " Effect of Cationic cholesterol derivatives on gene transfer and protein kinase C activity ", Biochem. Biophys, Acta 1111 , 239 (1992)), gramicidin (JY Legendre et al.," Cyclic amphipatic peptide-DNA complexes mediate hight-efficiency transfection of adherent mammalian cells " Proc. Natl. Acad. Sci. USA 90, 6077 (1993)) such as the plasma membrane as efficiently deuleogandago in combination with DNA There godoego. However, these liposomes are complicated to prepare, have a low inclusion rate in DNA having a large molecular weight, and have a large particle size.

In addition, cytotoxicity is also a major problem in the case of lipofectin, which is currently the most widely used (JH Felgner et al., "Enhanced gene delivery and mechanism studies with a novel series of cationic lipid formulations", J. Biol Chem., 28 , 2550 (1994)).

Recently, a positive polymer has been widely used as a DNA-introducing reagent, including diethylaminoethyldextran (L. Sompayrac et al., "Efficient infection ofmonkey cells with DNA of Simian virus 40", Proc. Natl. Acad. Sci. USA 12, 7575 (1981 )), poly (L- lysine) (Wu GY et al., "Receptor-mediated in vitro gene transformation by a soluble DNA carrier system ", J. Biol. Chem. 262, 4429 ( 1987)), histones (O. Boussif et al., &Quot; A versatile vector for gene and oligonucleotide transfer in cells in culture and in vivo: polyethyleneimine ", Proc. Natl. Acad. Sci. USA 9 2, 7297 4 , 372 (1993)), poly (ethyleneimine) (TM Chang et al., &Quot; Studies fo the " mechanism of cell intoxication by diphteria toxin fragment A-sialoorso-comucoid hybrid toxins. Edivence for utilization of an alternative receptor-mediated transpor T pathway ", J. Biol. Chem. 257, 12563 (1982)), cationic dendrimers (IA Simpson et al.," Hormonal regulation of mammalian glucose transport ", Ann. Biochem., 55 , 1059 (1986)).

Because DNA is a negative polymer, it forms an ionic bond with a positive polymer. By making the surface charge of the prepared DNA complex positive, it is possible to increase the efficiency of introduction into a cell having a negative surface charge. Such a method has been pointed out that the DNA complex is liable to precipitate, is toxic and has no cell specificity, but a lot of research has been carried out because of its simple and sometimes high gene expression activity.

In addition, the cells also have been described in A. Daurey-Varsat (Receptor-mediated endocytosis: the intracellular transferrin and its receptor, Biochimie, 68 , 375 (1986)), insulin (GY Wu et al. Edidence for targeted gene delivery to Hep G2 hepatoma cells in vitro ", Biochemistry, 27, 887 (1988 )), transferrin (Wu GY et al.," Receptor-mediated gene delivery and expression in vivo ", J. Biol. Chem. 263, 14621 (1988)). Therefore, in order to increase the specificity to the cells, a cell-specific recognition sugar chain (VS Trubetskoy et al., "Use of N-terminal modified poly L-lysine and a tibody conjugate as a carrier for targeted gene delivery in mouse lung endothelian cells ", Bioconjugate Chem. 3, 323 (1992); FC MacLaughlin et al., J. Controlled Rel. 56 , 258 IE Uchegbu et al., &Quot; Polymeric chitosan-based vesicles for drug delivery ", J. Pharm. Pharmacol. 50, 453 (1998) Kindle studies were also conducted.

In order to effectively introduce the DNA compound into the cell, the positive charge of the positive polymer, the hydrophobic group, the ethylene glycol chain, and the specific recognition element such as the sugar chain, the antibody, and the receptor are controlled so that the introduction efficiency of the DNA into the cell is significantly improved In fact. However, even if the efficiency of introduction into the cell is advanced, in reality, in vivo DNA delivery still has problems of cytotoxicity, immunoreactivity and accompanying side effects, so that there is no cytotoxicity, There is still a challenge to develop a DNA carrier.

Accordingly, the present inventors have conducted extensive research and have developed a novel carrier which has no toxicity, is excellent in biocompatibility and specifically binds to hepatocytes to improve the efficiency of introduction of DNA into cells, and a complex with DNA.

Therefore, one object of the present invention is to provide a novel carrier which is free of toxicity, excellent in biocompatibility, and specifically binds to hepatocytes.

Another object of the present invention is to provide a complex of DNA and a carrier that is toxic and has excellent biocompatibility and specifically binds to hepatocytes.

1 is an IR spectrum of a lactobionic acid (LA), chitosan (GC) having a galactose group and a graft polymer (GCD) of chitosan and dextran having a galactose group.

Figure 2 is a graph of particle size according to the charge ratio of the GCD / DNA complex.

Figure 3 is a graph showing the turbidity of GC / DNA complexes and GCD / DNA complexes at various charge ratios.

Figure 4 is a circularly polarized dichroism (CD) spectrum of DNA and GCD / DNA complexes with various charge ratios.

5 is an electrophoresis picture of DNA and GCD / DNA complexes of various charge ratios.

Figure 6 is a transmission electron micrograph of GC / DNA complexes and GCD / DNA complexes at various charge ratios.

Figure 7 is a scanning electron micrograph of a GCD / DNA complex at various charge ratios.

8 is a fluorescence photograph of Chang liver cells and HeLa cells transfected with GCD / DNA and DOTAP / DNA.

FIG. 9 is a photograph showing the degree of transfection of GCD / decoy oligonucleotide complexes for cell growth of spleen kidney cells, Hep G2 cells, CT-26 cells and HeLa cells.

The present invention relates to a cationic polymeric substance carrier having a molecular weight of 10,000 to 30,000, which contains the following formula (1) as a main repeating unit.

Provided that m is an integer of 1 or more.

In the present invention, the compound is preferably a graft polymer of chitosan having galactose group and dextran, and the ratio of chitosan and dextran in the polymer is preferably 1: 4 to 1: 8 parts by weight.

The present invention also relates to a complex of the carrier represented by the above formula (1) and DNA.

Preferably, the complex is an ion-bound product, and the charge ratio of the double carrier to DNA is from 3: 1 to 7: 1.

Hereinafter, the carrier and the composite of the present invention will be described in more detail.

The carrier of the present invention represented by the formula (1) is a natural polymer, which is a non-toxic and biocompatible positive polysaccharide chitosan. The galactose group specifically binds to an asialoglycolic protein receptor of hepatocytes and dextran It is a cationic polymer compound into which a sugar chain is introduced.

In order to prepare the carrier compound of the present invention of Formula 1, galactosylated chitosan (GC) is prepared by introducing a galactose group into chitosan.

Provided that n> x and x is an integer of 1 or more.

The preparation of GC of formula (2) is carried out by a reaction between chitosan and a substance having a galactose group such as lactobionic acid (LA). The reaction is coupled via an active ester intermediate in the presence of 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide hydrochloride (EDC) and a detailed description of this reaction can be found in Hermanson et al., &Quot; Immobilized affinity ligand techniques, Academic press, San Diego, 1992, which is incorporated herein by reference.

Next, the GCD of Formula 1 is prepared by grafting the GC of Formula 2 with hydrophilic dextran.

Provided that m is an integer of 1 or more.

The synthesis of dextran and GC is a reductive amination reaction in which the ratio of GC to dextran is in the range of 1: 4 to 1: 8 By weight. If the amount is less than 1: 4 parts by weight, GCD does not have sufficient water solubility. On the contrary, when the ratio exceeds 1: 8, excess GCD must be added to form a complex with DNA.

The galactose group introduced into the GCD of the present invention having the above formula (1) has a receptor-ligand specificity to the asialoglycolic protein receptor (ASGR) hepatocyte, and the receptor-mediated endocytosis Lt; / RTI > Furthermore, due to dextran introduced into GCD, the stability in an aqueous solution is further improved and the effect as a therapeutic agent for liver disease is further enhanced.

When the GCD of the present invention is mixed with DNA in an aqueous solution, the GCD of the present invention, which is a cationic polymer, and the anionic polymer DNA form electrostatic complementary bonds, that is, complex formation. The preferable charge ratio of such GCD / DNA complex is preferably 3: 1 to 7: 1 for GCD: DNA. If the charge ratio is less than 3: 1, there is a disadvantage that the complex is incompletely formed. Conversely, if the charge ratio is more than 7: 1, the complex size is increased and the transfection efficiency is decreased.

Since the GCD / DNA complex of the present invention is transfected only to the hepatocytes present on the cell surface, the genetic defect of the major metabolic enzyme can be treated by effectively introducing the DNA into hepatocytes.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but these are merely examples of the present invention and are not intended to limit the scope of the present invention.

Preparation Example 1: Preparation of chitosan (GC) having a galactose group [

Chuna (M _n ≈ 4,000) and dextran (M _n ≈ 5,900) were purchased from Funakoshi Chemical Company and DNA (sodium salt, from salmon testes) was purchased from Sigma. All other reagents were used without further purification.

N, N ', N' -tetramethylethylenediamine (TEMED) (Aldrich, USA) / HCl buffer (30 ml) was added to 300 ml of 10 mM N, (pH 4.7), 27.6 g of EDC (93.07 × 1.5 mM) was added, and the mixture was allowed to stand at room temperature for 3 days. The product was dialyzed against distilled water using a dialysis membrane (Spectra / Por7 membrane; MWCO = 3,500) for 4 days to obtain GC. The resulting GC was analyzed by infrared spectroscopy and the results are shown in Fig. 1 (Fig. 1 (b)).

Preparation Example 2: Preparation of graft polymer (GCD) of chitosan and dextran having a galactose group [

GCD was synthesized by reductive amination reaction. 0.5 g of the GC prepared in Preparation Example 1 and 2.5 g of dextran corresponding to 20 mol% of chitosan were dissolved in 0.07 M acetate buffer (pH 5.0), and then sodium cyanohydride corresponding to 10 times the number of moles of dextran . The product was purified using a dialysis membrane (MWCO = 12,000 to 14,000). Purified GC and GCD were confirmed using a gel permeation chromatograph. The composition ratio of GC and GCD was determined by NMR (Bruker, 600 MHz, Germany), and infrared spectroscopic analysis was performed to confirm the reaction between chitosan and LA and dextran. The results are shown in Fig. 1 (Fig. 1 (c) .

Fig. 1 shows IR spectra of LA, GC and GCD, wherein (a) is LA, (b) is GC and (c) is IR spectrum of GCD. Comparing FIGS. 1 (a) and 1 (b), it can be seen that in the case of GC prepared by reacting chitosan with LA, the carboxyl group (1730 cm ^-1 ) existing in the LA of the spectrum disappears, It reacts with amine groups. However, since dextran is structurally similar to chitosan in GC and dextran in FIG. 1 (c), the disappearance of a specific band of dextran, which is distinguished from chitosan, The progress of the reaction can be indirectly confirmed by the decrease in the intensity of the primary amine group (1550 cm ^-1 ) present and the increase in the OH group (3450 cm ^-1 ) of dextran compared to the amide group (1640 cm ^-1 ) .

The substitution values of galactose and dextran residue bound to chitosan in the GC of Preparation Example 1 and GCD of Production Example 2 were 12.8% and 20.2%, respectively, which were confirmed by NMR measurement.

≪ Preparation Example 3: Preparation of GCD / DNA complex >

To calculate the charge ratio, DNA was calculated as one charge per molecular weight of 330, and GCD was calculated as the average value of all polymers including galactose and dextran moiety. DNA was made to display fluorescence using ethidium bromide. Spontaneous complex formation was induced by mixing DNA (30 μg / ml) and GCD polymer solution in a 3: 1 charge ratio in 10 mM phosphate buffer (PBS, pH 7.4) in 150 mM NaCl. PBS was added to the final DNA The concentration was adjusted to 10 / / ml and left at room temperature for 12 hours. The formation of the complex was confirmed by electrophoresis at 100 V for 30 minutes in 1.0% agarose gel using Tris-acetate (TAE) running buffer. The results are shown in Fig.

Hereinafter, the results of measurement of various physicochemical properties according to the composition ratio and the charge ratio of the GCD / DNA complex of the present invention are shown.

≪ Test Example 1: Measurement of particle size according to charge ratio of GCD / DNA complex >

GCD / DNA complexes were formed in the same manner as in Preparation Example 3, except that the charge ratios of GCD / DNA were 1, 3, 5, and 7, respectively, and their particle sizes were measured. The composite particle size was measured with an electrophoresis light scattering spectrophotometer (ELS 8000, Otsuka Electronics, Ltd., Osaka, Japan) at 25 ° C and a scattering angle of 90 °. The results are shown in Fig.

Referring to FIG. 2, the particle size of the GCD / DNA complex decreases as the ratio of GCD to DNA increases, and has a minimum value of about 200 nm at a charge ratio of 5. In the case of GCD, in addition to the dextran present on the surface of the complex, the (+) electric charge on the surface of the complex is increased, It is believed that this prevents the accumulation of DNA by the electrostatic repulsive force caused by the electrostatic repulsion.

≪ Test Example 2: Measurement of turbidity of GCD / DNA complex >

GCD / DNA complexes having charge ratios of 1, 3, 5 and 7 were prepared in the same manner as in Preparation Example 3, above. The prepared GCD / DNA complex was dissolved in 10 mM PBS buffer containing 150 mM NaCl, and sonicated at 30 W for 2 minutes using an ultrasonic 410 sonicator (Hwa-Shin Instrument Co., Korea). The dispersion stability of the composite was measured at 500 nm using a UV-VIS spectrophotometer (Uvikon 923, Kontron Instruments, Italy) and the results are shown in FIG. In addition, a GC / DNA complex having a charge ratio of 3 was prepared by the same method, and the turbidity was measured. The results are shown in FIG.

Referring to FIG. 3, in the GC / DNA case with a charge ratio of 3 (FIG. 3 (a)), a complex of GC and DNA without a hydrophilic dextran residue showed a gradual increase in turbidity This means that aggregation is formed. Especially at high charge ratios (5 and 7: not shown), they precipitated rapidly even in the early stages of complex formation. However, the turbidity of the GCD / DNA complex suspension (FIGS. 3 (b) to 3 (e)) showed a gradual decrease in turbidity between the charge ratios of 1 and 3, This is believed to be due to the tight structure and the large side chains of the GCD completely surrounding the (-) charge of the DNA at around the charge ratio of 5, and this trend is expected to be closely related to the particle size results of FIG.

These results suggest that the GCD / DNA complex is more stable than the GC / DNA complex and that the dextran side chain present in the GCD / DNA complex is effective in preventing particle aggregation.

≪ Test Example 3: Circular polarization dichroism analysis (CD) >

CD analysis was performed to compare and analyze the secondary structure of DNA and charge ratio 1, 3, and 5 GCD / DNA complexes. The complexes used were those produced in turbidity measurements and the CD spectra were averaged over six scans as measured by a spectrophotometer (Jasco model J-715). The results are shown in Fig.

4, there is no significant difference between the spectrum (FIG. 4 (a)) of the DNA alone and the CD spectrum (FIG. 4 (b) It can be seen that the DNA does not change its secondary structure even after complexing with GCD.

≪ Test Example 4: Electrophoretic analysis >

A GCD / DNA complex was prepared and subjected to agarose gel electrophoresis in the same manner as in Preparation Example 3, except that the charge ratio of GCD to DNA was changed. Further, DNA was also subjected to agarose gel electrophoresis, and the results are shown in Fig. The composition of each lane is as follows.

Lane 1: 0.25 [mu] g DNA

Lane 2: 0.25 DNA of DNA + 0.0025 ((2.5 ng) of GCD

Lane 3: 0.25 DNA of DNA + 5 ng of GCD

Lane 4: 0.25 DNA of DNA + 10 ng of GCD

Lane 5: 0.25 DNA of DNA + 25 ng of GCD

Lane 6: 0.25 占 퐂 of DNA + 50 ng of GCD

Referring to FIG. 5, when DNA is used, the DNA migrates to the (+) charged side due to electrical interaction because the DNA carries a negative charge. However, when forming a complex with GCD, +), And it is not moved due to the large size of the composite. Lane 1 shows two types of plasmid DNA, supercoiled and nick-type bands, and lanes 2 to 6. As the ratio of GCD in the sample increases, the intensity of DNA staining into the gel And the staining intensity of the non-migrating DNA staying in the stomach as a complex increases. These results are interpreted as the proportion of the complex increases as the ratio of GCD to DNA increases, and therefore the amount of stays in the upper part increases.

≪ Test Example 5: Transmission Electron Microscopy (TEM) >

The charge ratio of the complex has a significant effect on the compaction of the DNA. Transmission electron microscopy (TEM) was performed to examine the shape of the composite.

First, GC / DNA complexes with charge ratios 1 and 3 and GCD / DNA complexes with charge ratios 1 and 7 were prepared by the same method as above, and then the morphology of these complexes was determined using TEM (JEM 1010, JEOL, Japan) Respectively. Observations were made by dropping the complex drop to the copper grid and then negative staining for 30 seconds with 1% uranyl acetate solution. The grid was completely dried for 10 minutes and then observed with an electron microscope. The results are shown in Fig.

Referring to FIG. 6, the GC / DNA complex has an extended cohesive morphology (FIG. 6 (a)), while the GCD / DNA complex has a spherical smaller and compacted form compared to GC / DNA 6 (b)).

≪ Test Example 6: Scanning Electron Microscope (SEM) >

GCD / DNA complexes having charge ratios 1, 3 and 5 and a charge ratio of 3 after ultrasonic treatment were prepared by the same method as above, and then examined by scanning microscope. Observations were made by dropping a drop of the composite onto a stud and drying at room temperature. The sample was then coated with gold using a JEOL JFC-110E ion sputtering machine (Japan). SEM observation was performed using a JSM 5410LV scanning electron microscope (JEOL, Japan). The results are shown in Fig. As can be seen in FIG. 7, the GCD / DNA complex has a spherical compacted form.

≪ Test Example 7: ASGR specificity of GCD / DNA complex >

Hereinafter, the ASGR specificity of the GCD / DNA complex of the present invention will be described. In this example, Chang River cells in which ASGR exists on the cell surface and helper cells without these receptors (J. You et al., "Enhancement of transfection efficiency using ligand-modified lipid vesicles", J. Ferment. Bioeng. , 85 , 525 (1998)) were measured for the effect of GCD / DNA complexes on gene transformation.

The DNA used in this experiment is pEGFP-1, which synthesizes a green fluorescent protein in the cytoplasm, which encodes the C-terminus of a green fluorescent protein with a 35-fold stronger fluorescence intensity than the wild-type green fluorescent protein (J. Sambrook et al , &Quot; Molecular cloning " 2nd ed., 1989). GCD / DNA complexes were prepared with 50 ng of GCD synthesized by the above method and 0.25 g of pEGFP, and then the kidney and helper cells were transfected. Similarly, 2 [mu] g of DOTAP (N- [1- (2,3, -dioloyloxy) propyl] -N, N, N-trimethylammonium chloride) without cell specificity as a commercially available cationic lipid and pEGFP 0.25 ≪ / RTI > DOTAP / DNA complexes were prepared, and window stem cells and helper cells were transfected. The results are shown in Fig.

Referring to FIG. 8, it can be seen that both GCD / DNA and DOTAP / DNA complex are transfected in the case of the case of a river cell (FIG. 8 (a)) and green fluorescence is observed under UV irradiation, (FIG. 8 (b)), it can be observed that only DOTAP / DNA is transfected. From these results, it can be seen that GCD / DNA complexes are transfected into cells via ASGR.

≪ Test Example 8: Possibility of use of GCD in the treatment of liver cancer &

The GCD of the present invention was synthesized for the purpose of treating genetic defects in cells having hepatocyte specificity. In this study, we investigated the possibility of GCD to be used in the treatment of liver cancer by complexing GCD with a gene that synthesizes a protein that inhibits cell growth.

Preparation of decoy oligonucleotide

YB-1 belongs to the Y-box protein family and plays an important role in cell growth. The decoy nucleotide, a YB-1 transcription factor, is known to inhibit the function of the YB-1 gene - activating transcription factor and decrease the expression of YB-1 . The decoy oligonucleotides were synthesized in the form of single strands by an automatic oligonucleotide synthesizer, annealed through complementation of DNA, and their nucleotide sequence was 5'-GGGTCAGGTGGGCAGATTGACAGTACCACT-3 '.

Cell line and cell culture

Hela cells (human cervical cancer cells) and CT-26 (mouse adenocarcinoma cells) were cultured in Dubelccos' modified Eagle medium (DMEM, Gibco BRL, Paris, France) Liver cancer cells) and spleen kidney cells were cultured in a minimal essential medium (MEM). All culture media supplemented with 10% fetal bovine serum (FBS). Cells were maintained at 37 [deg.] C in 5% CO ₂ incubator.

Transfection Protocol

HeLa, CT-26, Hep G2, and Chang River were cultured in a 5% CO ₂ incubator at 37 ° C in a medium containing 10% FBS, and placed in a 22 mm culture plate at a density of 5 × 10 ⁴ / 70% confluency. The GCD / DNA complex diluted with serum-free medium was added to the culture plate and incubated at 37 ° C in 5% CO ₂ atmosphere for 6 hours. After the treatment, the serum-free medium was changed to a fresh medium containing serum and re-cultured for 3 days . Cells transfected with YB-1 transcription factor decoy oligonucleotides were removed from the culture plate and the number of cells was measured. The results are shown in Fig.

In this experiment, the inhibition of cell growth by the GC / decoy nucleotide complex was not measured because the relatively large size of these complexes and the instability in aqueous solution were not suitable for receptor-mediated intracellular entry. It was seen that GCD / decoy nucleotide complexes were transfected in the spleen kidney cells and Hep G2 cells with ASGR on the cell surface to inhibit cell growth at a concentration of GCD (50 ng) / decoy nucleotide (0.25 g) (Fig. 9 a) and (b)), the effect was somewhat lower than DOTAP. However, in CT-26 and HeLa cells without ASGR, GCD / decoy nucleotides did not undergo transfection. In contrast to DOTAP (F. Tang et al., Synthesis of a single-tailed cationic lipid and investigation of its transfection, J. Control. Rel . 62 , 345 (1999)), The cationic GCD, which is expected to be highly toxic, showed little toxicity. When it was complexed with decoy nucleotide, it showed no toxicity due to the dispersed charge density. These results suggest that GCD conjugates can be used for hepatocyte-specific gene delivery systems.

As described above, the GCD carrier according to the present invention can be effectively used in a hepatocyte-specific gene transfer system. The DNA / GCD complex specifically binds to hepatocytes, has no toxicity, and has high biocompatibility Do.

Claims (6)

A polymer compound having a molecular weight of 10,000 to 30,000 and containing the following formula (1) as a main repeating unit. Provided that m is an integer of 1 or more. The polymer compound according to claim 1, wherein the galactose group-containing chitosan (GC) and dextran are contained in a weight ratio of 1: 4 to 1: 8. The polymer compound according to claim 2, wherein the chitosan (GC) having a galactose group is a compound represented by the following formula (2). Provided that n> x and x is an integer of 1 or more. A complex of the polymer compound of claim 1 with DNA. 5. The complex of claim 4, wherein the charge ratio of the carrier of claim 1 to DNA is between 3: 1 and 7: 1. A therapeutic agent for liver disease comprising the complex of claim 4 as an active ingredient.