PROPYL CATIONIC PEPTIDE LIPIDS, SYNTHESIS METHOD THEREOF, AND APPLICATION THEREOF

Abstract

A class of propyl cationic peptide lipids is propyl cationic peptide lipid compounds having a general formula structure as follows. After the propyl cationic peptide lipids are dispersed in water, a cationic liposome with a particle size of approximately 100 nm is obtained. The cationic liposome can carry plasmid DNA (pDNA) or small interfering RNA (siRNA) into cells to realize the function of gene delivery, and is almost non-toxic to the cells.

##STR00001##

Claims

1. A propyl cationic peptide lipid having a structure of general formula I: ##STR00003## wherein, R.sub.1 is selected from C.sub.1-20 alkyl, x is selected from 1 to 6, AA is selected from lysine(Lys), ornithine(Orn), arginine(Arg), histidine(His), aspartic acid(Asp), alanine(Ala) or glycine(Gly).

2. The propyl cationic peptide lipid according to claim 1, wherein R.sub.1 is selected from C.sub.12, C.sub.14, C.sub.16, or C.sub.18 alkyl, x is selected from 2 to 4.

3. A method for synthesizing the propyl cationic peptide lipid according to claim 1, comprising the following steps: 1) preparing a peptide head intermediate by protecting amino group of amino acid with a protective reagent by means of orthogonal protection method: the amino acid being selected from Lys, Orn, Arg, His, Asp, Ala or Gly, the amino group protective reagent being di-tert-butyl dicarbonate (Boc2O), Fluorenylmethoxycarbonyl succinimide (Fmoc-OSu) or benzyl chloroformate (CbzCl), at a molar ratio of the protective reagent and the amino acid being 1:1 to 8:1, the reaction solvent being acetonitrile, toluene, acetone, tetrahydrofuran or water, the reaction time being 1 to 20 hours, and the reaction temperature being 0 to 100° C. After the reaction, the solvent being removed by rotary evaporation, followed by purification by means of recrystallization with a recrystallization solvent being an ethyl acetate/petroleum ether mixed solvent (v/v=3:1); 2) protecting the amino group of 3-amino-1,2-propanediol with Fmoc-OSu protective reagent, after acylation with an acylating agent, reacting the resultant with alkyl amine, to prepare a disubstituted propyl long carbon chain intermediate: the acylating agent being carbonyl diimidazole, at a molar ratio of the acylating agent and 3-amino-1,2-propanediol being 1:1 to 3:1, after acylation, the molar ratio of 3-amino-1,2-propanediol to the alkyl amine being from 1:1 to 8:1, the reaction solvent being 30 ml to 300 ml of toluene, dichloromethane, DMF or chloroform, the reaction time being 12 to 48 hours, the reaction temperature being 25˜100° C., after the reaction, the solvent being removed by rotary evaporation at 70° C., recrystallization being carried out with DMF, ethanol, ethyl acetate, water or ethanol/water mixed solvent; 3) linking the peptide head intermediate prepared in step (1) with the double long carbon chain intermediate prepared in step (2) via acylation: a. activating the peptide head intermediate firstly with an activating agent which is 2-(7-azobenzotriazole)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU), N,N′-dicyclohexyl carbonimide (DCC) or 1-hydroxybenzotriazole (HOBt), at a molar ratio of the peptide head intermediate to the activating agent being 1:1 to 1:8, the reaction temperature being 0 to 60° C., the reaction time being 0.5 to 24 hours; b. adding a solution of the double long carbon chain intermediate in dichloromethane, DMF or chloroform to the reaction solution in step a, after acylation, an amide bond being generated between the amino group of the intermediate and the carboxyl group of the peptide head intermediate, the peptide head intermediate reacting with the double long carbon chain intermediate at a molar ratio of 1:1 to 8:1, the reaction solvent being toluene, DMF, chloroform, acetone or methylene chloride, the reaction time being 12 to 96 hours, the reaction temperature being 20 to 100° C.; 4) removing the protective group with an amino de-protection agent which is 10% NaHCO.sub.3 (w/v) or trifluoroacetic acid, at a molar ratio of the de-protection agent and a lipoid compound being 1:1 to 1:2, the de-protection time being 1 to 8 hours, the de-protection temperature being 0 to 4° C., the product being purified by recrystallization to obtain a crude product, the recrystallization solvent being ethyl acetate, acetonitrile, ethanol, water or anhydrous ether; 5) carrying out purification by column chromatography after the recrystallization, the crude product being dissolved in chloroform and purified with a silica gel column, followed by elution with a mixed solvent of methanol/chloroform (at a volume ratio of 3:1), the solvent being removed by rotary evaporation, followed by lyophilization, to obtain a cationic peptide lipid compound containing one amino acid head; 6) synthesizing other propyl cationic peptide lipid using the cationic peptide lipid compound containing one amino acid head as a raw material: subjecting the peptide head intermediate prepared in step (1) and the cationic peptide lipid containing one amino acid head prepared in step (5) to amino activation and acylation, to obtain a cationic peptide lipid compound of which the head is 1 to 6 amino acid(s), at a molar ratio of the two being 1:8 to 8:1, the specific reaction conditions and purification method being the same as steps (3), (4) and (5).

4. A cationic peptide liposome prepared from the propyl cationic peptide lipid according to claim 1, wherein the cationic peptide liposome is a homogeneous and stable liposome which is positively charged on the surface thereof and has a particle size of about 100 nm formed by dispersing the propyl cationic peptide lipid in an aqueous phase.

5. A method for preparing the propyl cationic peptide liposome according to claim 4, wherein comprising the following steps: (1) dissolving the propyl cationic peptide lipid and an additive in chloroform or methanol according to a molar ratio of the two being 1:8 to 8:1, the additive being lecithin, sucrose esters, dioleoyl phosphatidylethanolamine (DOPE), dioleoyl phosphatidylcholine (DOPC) or cholesterol; (2) blowing the solution under nitrogen to form a uniform thin film, and drying in vacuum for 4 to 24 hours; (3) performing hydration at 10 to 80° C. with ethanol, ultrapure water or phosphate buffer for 1 to 10 hours, ultrasonic vibrating to transparent, to obtain the cationic peptide liposome with a concentration of 0.5 to 3 mg/ml.

6. A propyl cationic peptide liposome/gene complex prepared from the propyl cationic peptide liposome according to claim 4, wherein the propyl cationic peptide liposome according to claim 4 and plasmid DNA (pDNA) or small interfering RNA (siRNA), by electrostatic interaction form homogeneous and stable nanoparticles dispersed in an aqueous phase.

7. A method for preparing the propyl cationic peptide liposome/gene complex according to claim 6, wherein comprising the following steps: (1) taking 0.5 to 8 μl the propyl cationic peptide liposome according to claim 4 and dispersing into 25 to 50 μl cell culture medium of DMEM or RPMI1640, mixing homogeneous to make a concentration being 0.02 μg/μl to 0.16 μg/μl; (2) diluting pDNA or siRNA in the cell culture medium DMEM or RPMI1640, mixing homogeneous 0.5 to 1.0 μl to make a plasmid concentration being 0.02 μg/μl; (3) mixing the two dilutions of (1) and (2) homogeneous according to a mass ratio between the liposome and gene of 1:1 to 8:1, placing at a room temperature for 10 to 40 min, to obtain the propyl cationic peptide liposome/gene complex.

8. The propyl cationic peptide liposome/gene complex according to claim 5, wherein the gene complex is applied in cell transfection.

Description

DESCRIPTION OF DRAWINGS

[0041] FIG. 1 is an infrared spectra of a propyl peptide lipid compound R.sub.12O;

[0042] FIG. 2 is a nuclear magnetic resonance hydrogen spectrum of a propyl peptide lipid compound R.sub.12O;

[0043] FIG. 3 is an infrared spectra of a propyl peptide lipid compound R.sub.14AO;

[0044] FIG. 4 is a nuclear magnetic resonance hydrogen spectrum of a propyl peptide lipid compound R.sub.14AO;

[0045] FIG. 5 is an infrared spectra of a propyl peptide lipid compound R.sub.16OKK;

[0046] FIG. 6 is a nuclear magnetic resonance hydrogen spectrum of a propyl peptide lipid compound R.sub.16OKK;

[0047] FIG. 7 is an infrared spectra of a propyl peptide lipid compound R.sub.18AOKK;

[0048] FIG. 8 is a nuclear magnetic resonance hydrogen spectrum of a propyl peptide lipid compound R.sub.18AOKK;

[0049] FIG. 9 is a particle-size diagram of propyl peptide liposomes;

[0050] FIG. 10 is a Zeta potential diagram of propyl peptide liposomes;

[0051] FIG. 11 is a diagram showing detection of the binding capacity of propyl peptide liposomes to plasmid DNA;

[0052] FIG. 12 is a diagram showing the green fluorescent protein expression in Hep-2 cells transfected by propyl peptide liposomes carrying plasmid pGFP-N2;

[0053] FIG. 13 is a diagram showing the luciferase expression in Hep-2 cells transfected by propyl peptide liposomes carrying plasmid pGL-3, detected by a microplate reader;

[0054] FIG. 14 is a diagram showing Luciferase gene silencing in A549 cells transfected by propyl peptide liposomes carrying siRNA;

[0055] FIG. 15 is a diagram showing cytotoxicity to Hep-2 during cells transfection by cationic peptide liposomes, detected by MTT colorimetry.

DETAILED DESCRIPTION OF EMBODIMENTS

[0056] To be helpful for further understanding the invention, preferable embodiments of the invention are described in combination with the following examples, but the following description is not a limitation to the claims of the invention but merely is further interpretation of features and advantages of the invention.

[0057] In this specification, the description is made by taking the following four kinds of propyl cationic peptide lipid compounds as examples: N-(1,2-bis-dodecyl amino formyloxopropyl) ornithine amide represented by R.sub.12O, containing an Orn cationic head, a urethane linkage and a 14 carbon propyl double hydrophobic tail chain; N-(1,2-bis-tetradecylamino formyloxypropyl) alanine ornithine amide (R.sub.14AO) containing an Ala-Orn dipeptide cationic head, a urethane linkage and a 14 carbon propyl double hydrophobic tail chain; N-(1,2-bis-hexadecylamino formyloxypropyl) ornithine dimeric lysine amide (R.sub.16OKK) containing an Orn-Lys-Lys tripeptide cationic head, a urethane linkage and a 16 carbon propyl double hydrophobic tail chain; N-(1,2-bis-octadecylamino formyloxypropyl) alanine-ornithine-dimeric lysine amide (R.sub.18AOKK) containing an Ala-Orn-Lys-Lys tetrapeptide cationic head, a urethane linkage and a 18 carbon propyl double hydrophobic tail chain.

Example 1

[0058] A synthesis method of the cationic peptide lipid compound R.sub.12O is as follows.

[0059] (1) 2 mmol L-Orn was weighted and dissolved in 15 ml of acetonitrile; 16 mmol Boc.sub.2O was dissolved in acetonitrile and added dropwise to an acetonitrile solution of ornithine, to react and generate a complex; 10 ml 20% sodium bicarbonate aqueous solution was added, and 2 g of anhydrous sodium carbonate and an appropriate amount of 8-hydroxyquinoline were added in batches; the mixture was stirred and reacted at room temperature for 4 hours to remove copper ions in the complex; then 2 mmol Fmoc-OSu was added to the aforesaid solution, followed by stirring at room temperature for 2 hours; the resultant was recrystallized with an ethyl acetate/petroleum ether mixed solvent, to obtain a peptide head intermediate Fmoc-L-Orn (Boc)-OH.

[0060] (2) 10 mmol 3-amino-1,2-propanediol was dissolved in 50 ml water, 10 mmol sodium bicarbonate was added, and then 10 mmol Fmoc-OSul was dissolved in 100 ml of acetone, slowly added dropwise and stirred overnight. Acetone was distilled off by rotary evaporation. 8.0 mmol of the above product was dissolved in a dichloromethane/toluene mixed solvent; 8.0 mmol CDI was dissolved in toluene, and the two were slowly added dropwise under protection by nitrogen to react at 25° C. for 12 hours. 1 mmol dodecylamine was dissolved in 5 ml toluene solution, and the mixture was slowly added dropwise to the aforesaid reaction solution, and reaction was further carried out at 25° C. for 24 hours. 3.0 mmol sodium hydroxide was added to the reaction solution to react for 1 hour. After completion of the reaction, the solvent was removed by rotary evaporation at 70° C., followed by recrystallization with acetonitrile/water (v/v=5:1), to obtain pale yellow solid, which was dried under vacuum. The resultant was recrystallized with DMF once again, to obtain a double long carbon chain intermediate R.sub.12.

[0061] (3) The prepared peptide head intermediate Fmoc-L-Orn (Boc)-OH and an activating agent HATU were dissolved at a molar ratio of 1:8 in a toluene solution, and the activation was carried out at 0° C. for 24 hours, and then a toluene solution of the double long carbon chain intermediate R.sub.12 was added so that the peptide head intermediate reacted with the double long carbon chain intermediate according to a molar ratio of 8:1, followed by amidation reaction at 20° C. for 96 hours; after the reaction was completed, the solvent was removed by rotary evaporation at 70° C. The resultant was dissolved with a solvent of dichloromethane/trifluoroacetic acid=2/1 (v/v), and placed at 4° C. for 8 h to release the protective group Boc; then the product was dissolved by 20 ml 10% NaHCO.sub.3 solvent, reacted for 1 hour, to remove Fmoc group.

[0062] (4) After being recrystallized with ethyl acetate and acetonitrile for four times, the product was dissolved in chloroform, and the crude product was purified by a silica gel column and then was eluted with a methanol/chloroform (volume ratio 3:1) mixed reagent. The solvent was removed by rotary evaporation, and the resultant was lyophilized, to obtain a propyl cationic peptide lipid R.sub.12O containing one ornithine head and a 12C double long carbon chain, of which the structural characterization is shown by FIG. 1 and FIG. 2.

[0063] Its structure is characterized as below: .sup.1H NMR (400 MHz, CD.sub.3OD) δ:0.86 (6H, CH.sub.3), 1.25 (36H, (CH.sub.2).sub.9), 2.95 (2H, CH.sub.2NH.sub.2), 3.08 (2H, CH.sub.2NH), 3.30 (2H, OCHCH.sub.2), 3.93 (2H, CHNH.sub.2), 4.01 (2H, OCH.sub.2CH), 5.02 (1H, OCHCH.sub.2). .sup.13C NMR (400 MHz, CD.sub.3OD) δ: 12.98 (CH.sub.3), 23.09 (CH.sub.3CH.sub.2), 30.02 ((CH.sub.2).sub.8), 37.98 (CH.sub.2NH), 40.13 (CH.sub.2NHCH), 40.75 (CH.sub.2NH.sub.2), 52.76 (CHNH, CHNH.sub.2), 63.91 (OCH.sub.2CH), 71.45 (OCH.sub.2CHO), 158.80 (NHCOO), 169.15 (NHCOCH). IRν/cm.sup.−1: 3289 (ν.sub.NH), 2930 (ν.sub.CH), 1679 (ν.sub.C═O), 1540 (δ.sub.NH), 1190 (ν.sub.CN).

Example 2

[0064] A synthesis method of the cationic peptide lipid compound R.sub.14AO is as follows.

[0065] (1) 10 mmol L-Ala was weighted and dissolved in 100 ml of acetonitrile; 12 mmol Boc.sub.2O was dissolved in acetonitrile and added dropwise to an acetonitrile solution of Ala; the mixture was stirred and reacted at room temperature for 2 hours, and then the solvent was removed by rotary evaporation at 70° C., followed by recrystallization with an ethyl acetate/petroleum ether mixed solvent, to obtain a peptide head intermediate L-Ala (Boc)-OH.

[0066] (2) 10 mmol 3-amino-1,2-propanediol was dissolved in 50 ml water, 10 mmol sodium bicarbonate was added, and then 20 mmol Fmoc-OSul was dissolved in 100 ml acetone, slowly added dropwise and stirred overnight. Acetone was distilled off by rotary evaporation. 5.0 mmol of the above product was dissolved in a dichloromethane/toluene mixed solvent; 5.0 mmol CDI toluene solution was added under protection by nitrogen to react at 80° C. for 2 hours. 12 mmol toluene solution of tetradecylamine was slowly added dropwise to the aforesaid reaction solution, and reaction was further carried out at 80° C. for 2 hours. 3.0 mmol sodium hydroxide was added to the reaction solution to react for 1 h. After completion of the reaction, the solvent was removed by rotary evaporation at 70° C., followed by recrystallization with acetonitrile/water (v/v=5:1), to obtain pale yellow solid. The resultant was recrystallized with DMF once again, to obtain a double long carbon chain intermediate R.sub.14.

[0067] (3) The prepared peptide head intermediate L-Ala (Boc)-OH and an activating agent HATU were dissolved at a molar ratio of 1:1 in a toluene solution, and the activation was carried out at 60° C. for 0.5 hour, and then a toluene solution of the double long carbon chain intermediate R.sub.14 was added (the peptide head intermediate and the long carbon chain intermediate reacted according to a molar ratio of 1:1); followed by amidation reaction at 40° C. for 48 hours; after the reaction was completed, the solvent was removed by rotary evaporation at 70° C. The resultant was dissolved with a solvent of dichloromethane/trifluoroacetic acid=3/1 (v/v), and placed at 4° C. for 2 hours to release the protective group Boc; then the product was dissolved by a dioxane solvent, and 2 ml 10% NaHCO.sub.3 was added to react for 2 hours, to remove Fmoc group; then the solvent was removed by rotary evaporation at 70° C.

[0068] (4) The product was recrystallized with acetonitrile twice and then recrystallized with ethyl acetate twice. After that, the product was dissolved in chloroform, and the crude product was purified by a silica gel column and then was eluted with a methanol/chloroform (volume ratio 3:1) mixed reagent. The solvent was removed by rotary evaporation at 70° C., and the resultant was lyophilized, to obtain a propyl cationic peptide lipid compound containing one alanine head.

[0069] (5) 10 mmol L-Orn was weighted and dissolved in 30 ml acetonitrile, and 20 mmol Boc.sub.2O was dissolved in acetonitrile, and the mixture was added dropwise to the acetonitrile solution of ornithine, and a complex was generated after reaction. 15 ml 10% sodium bicarbonate aqueous solution was added, and 3 g of anhydrous sodium carbonate and an appropriate amount of 8-hydroxyquinoline were added in batches; the mixture was stirred and reacted at 30° C. for 2 hours to remove copper ions in the complex; then 12 mmol Fmoc-OSu was added to the aforesaid solution, followed by stirring at 30° C. for 2 hours; the solvent was removed by rotary evaporation after the reaction completed, and the resultant was recrystallized twice with an ethyl acetate/petroleum ether system, to obtain a peptide head intermediate Fmoc-L-Orn (Boc)-OH.

[0070] (6) The cationic peptide lipid compound containing one alanine head prepared in step (4) reacted with the amino protected ornithine peptide heat intermediate Fmoc-L-Orn (Boc)-OH prepared in step (5) at a molar ratio of 8:1, followed by amino acid activation and amidation, to obtain a propyl cationic peptide lipid R.sub.14AO containing an Ala-Orn dipeptide cationic head and a 14C double long carbon chain. Specific reaction conditions and purification method are the same with steps (3) and (4), and the structural characterization is shown by FIG. 3 and FIG. 4.

[0071] Its structure is characterized as below: .sup.1H NMR (400 MHz, CD.sub.3OD) δ: 0.88 (6H, CH.sub.3), 1.26 (44H, (CH.sub.2).sub.11), 2.89 (2H, CH.sub.2NH.sub.2), 3.06 (2H, CH.sub.2NH), 3.32 (2H, OCHCH.sub.2), 3.93 (2H, CHNH.sub.2), 4.04 (2H, OCH.sub.2CH), 4.97 (1H, OCHCH.sub.2). .sup.13C NMR (400 MHz, CD.sub.3OD) δ: 12.91 (CH.sub.3), 22.98 (CH.sub.3CH.sub.2), 30.04 ((CH.sub.2).sub.10), 38.18 (CH.sub.2NH), 39.56 (CH.sub.2NHCH), 40.71 (CH.sub.2NH.sub.2), 52.79 (CHNH, CHNH.sub.2), 63.96 (OCH.sub.2CH), 71.24 (OCH.sub.2CH), 158.12 (NHCOO), 168.55 (NHCOCH). IRν/cm.sup.−1: 3320 (ν.sub.NH), 2900 (ν.sub.C═O), 1675 (ν.sub.C═O), 1540 (δ.sub.NH), 130 (ν.sub.CN).

Example 3

[0072] A synthesis method of the cationic peptide lipid compound R.sub.16OKK is as follows.

[0073] (1) 10 mmol L-Orn was weighted and dissolved in 15 ml of acetonitrile; 80 mmol Boc.sub.2O was dissolved in acetonitrile, and the mixture was added dropwise to an acetonitrile solution of ornithine, and a complex was generated after reaction; 20 ml 20% sodium bicarbonate aqueous solution was added, and 2 g of anhydrous sodium carbonate and an appropriate amount of 8-hydroxyquinoline were added in batches; the mixture was stirred and reacted at room temperature for 4 hours to remove copper ions in the complex; then 10 mmol Fmoc-OSu was added to the aforesaid solution, followed by stirring at room temperature for 2 hours; the resultant was recrystallized with an ethyl acetate/petroleum ether mixed solvent, to obtain a peptide head intermediate Fmoc-L-Orn (Boc)-OH.

[0074] (2) 5 mmol 3-amino-1,2-propanediol was dissolved in 50 ml acetone, 5 mmol sodium bicarbonate was added, and then 7 mmol Fmoc-OSul was dissolved in 50 ml of acetone, slowly added dropwise and stirred overnight. Acetone was distilled off by rotary evaporation. 2.0 mmol of the above product was dissolved in a dichloromethane solvent; 2.0 mmol CDI was dissolved in toluene, and the two were slowly added dropwise under protection by nitrogen to react at 40° C. for 24 hours. 2 mmol hexadecylamine was dissolved in 10 ml toluene solution, and the mixture was slowly added dropwise to the aforesaid reaction solution, and reaction was further carried out at 40° C. for 48 hours. 5.0 mmol sodium hydroxide was added to the reaction solution to react for 2 hours. After completion of the reaction, the solvent was removed by rotary evaporation at 70° C., followed by recrystallization with acetonitrile/water (v/v=5:1), to obtain pale yellow solid, which was dried under vacuum. The resultant was recrystallized with DMF once again, to obtain a double long carbon chain intermediate R.sub.16.

[0075] (3) The prepared peptide head intermediate Fmoc-L-Orn (Boc)-OH and an activating agent HATU were dissolved at a molar ratio of 1:2 in a toluene solution, and the activation was carried out at room temperature for 2 hours, and then a toluene solution of the double long carbon chain intermediate R.sub.16 was added so that the peptide head intermediate reacted with the double long carbon chain intermediate according to a molar ratio of 1:2, followed by amidation reaction at 40° C. for 48 hours; after the reaction was completed, the solvent was removed by rotary evaporation at 70° C. The resultant was dissolved with a solvent of dichloromethane/trifluoroacetic acid=2/1 (v/v), and placed at 4° C. for 1 hour to release the protective group Boc; then the product was dissolved by a dioxane solvent; then 30 ml 10% NaHCO.sub.3 solvent was added and reacted for 2 hours, to remove Fmoc group.

[0076] (4) After the product was recrystallized with acetonitrile and then recrystallized with petroleum ether four times, the product was dissolved in chloroform, and the crude product was purified by a silica gel column and then was eluted with a methanol/chloroform (volume ratio 3:1) mixed reagent. The solvent was removed by rotary evaporation at 70° C., and the resultant was lyophilized, to obtain a propyl cationic peptide lipid compound containing one ornithine head.

[0077] (5) 2 mmol L-Lys was weighted and dissolved in 15 ml of acetonitrile; 2 mmol Boc.sub.2O was dissolved in acetonitrile, and then the mixture was added dropwise to an acetonitrile solution of lysine; 1 mmol copper sulfate pentahydrate was added, and (LysBoc).sub.2Cu complex was generated after the reaction; 10 ml 20% sodium bicarbonate aqueous solution was added, and 2 g of anhydrous sodium carbonate and an appropriate amount of 8-hydroxyquinoline were added in batches; the mixture was stirred and reacted at room temperature for 4 hours to remove copper ions in the complex; then 2 mmol Fmoc-OSu was added to the aforesaid solution, followed by stirring at room temperature for 2 hours; the resultant was recrystallized with an ethyl acetate/petroleum ether system, to obtain a peptide head intermediate Fmoc-L-Lys (Boc)-OH.

[0078] (6) The cationic peptide lipid compound containing one ornithine head was taken as a raw material to react with the amino protected lysine heat intermediate prepared in step (5) at a molar ratio of 1:2, followed by amino acid activation and amidation; wherein the specific reaction conditions and purification method are the same with steps (3) and (4). A propyl cationic peptide lipid R.sub.16OKK containing a cationic head with a structure of one ornithine and two lysines, and a 16C double long carbon chain, is obtained, of which the structural characterization is shown by FIG. 5 and FIG. 6.

[0079] Its structure is characterized as below: .sup.1H NMR (400 MHz, CD.sub.3OD) δ: 0.89 (6H, CH.sub.3), 1.29 (52H, (CH.sub.2).sub.13), 2.90 (4H, CH.sub.2NH.sub.2), 3.18 (6H, CH.sub.2NH), 3.33 (2H, OCHCH.sub.2), 3.93 (2H, CHNH.sub.2), 4.15 (2H, OCH.sub.2CH), 4.88 (1H, OCHCH.sub.2). .sup.13C NMR (400 MHz, CD.sub.3OD) δ: 13.01 (CH.sub.3), 22.85 (CH.sub.3CH.sub.2), 29.78 ((CH.sub.2).sub.12), 39.04 (CH.sub.2NH), 40.33 (CH.sub.2NHCH), 41.28 (CH.sub.2NH.sub.2), 52.87 (CHNH, CHNH.sub.2), 63.90 (OCH.sub.2CH), 71.45 (OCH.sub.2CHO), 157.0 (NHCOO), 169.0 (NHCOCH). IRν/cm.sup.−1:3430 (ν.sub.NH), 2920 (ν.sub.CH), 1670 (ν.sub.C═O), 1255 (ν.sub.CN).

Example 4

[0080] A synthesis method of the cationic peptide lipid compound R.sub.18AOKK is as follows.

[0081] (1) 20 mmol L-Ala was weighted and dissolved in 100 ml of acetonitrile; 40 mmol Boc.sub.2O was dissolved in acetonitrile and added dropwise to the acetonitrile solution of Ala; the mixture was stirred and reacted at room temperature for 2 hours, and then the solvent was removed by rotary evaporation at 70° C., followed by recrystallization with an ethyl acetate/petroleum ether mixed solvent, to obtain a peptide head intermediate L-Ala (Boc)-OH.

[0082] (2) 15 mmol 3-amino-1,2-propanediol was dissolved in 80 ml acetone, 10 mmol sodium bicarbonate was added, and then 40 mmol Fmoc-OSul was dissolved in 80 ml of acetone, slowly added dropwise and stirred overnight. Acetone was distilled off by rotary evaporation. 10 mmol of the above product was dissolved in a dichloromethane solvent; 14 mmol CDI was dissolved in toluene, and the two were slowly added dropwise under protection by nitrogen to react at 40° C. for 24 hours. 10 mmol octadecylamine was dissolved in 10 ml toluene solution, and the mixture was slowly added dropwise to the aforesaid reaction solution, and reaction was further carried out at 40° C. for 48 hours. 2.0 mmol sodium hydroxide was added to the reaction solution to react for 2 h. After completion of the reaction, the solvent was removed by rotary evaporation at 70° C., followed by recrystallization with acetonitrile/water (v/v=5:1), to obtain pale yellow solid, which was dried under vacuum. The resultant was recrystallized with DMF once again, to obtain a double long carbon chain intermediate R.sub.18.

[0083] (3) The prepared peptide head intermediate L-Ala (Boc)-OH and an activating agent HATU were dissolved at a molar ratio of 1:2 in a toluene solution, and the activation was carried out at room temperature for 2 hours, and then a toluene solution of the long carbon chain intermediate R.sub.18 was added so that the peptide head intermediate reacted with the long carbon chain intermediate according to a molar ratio of 1:2, followed by amidation reaction at 40° C. for 48 hours; after the reaction was completed, the solvent was removed by rotary evaporation at 70° C. The resultant was dissolved with 10 ml trifluoroacetic acid solvent, and placed at 4° C. for 2 hours to release the protective group Boc; then the product was dissolved by 20 ml 10% NaHCO.sub.3 solvent and reacted for 0.5 hour, to remove Fmoc group.

[0084] (4) The product was recrystallized with acetonitrile twice and then recrystallized twice with a mixture solvent of ethanol and water (volume ratio 5:1). After that, the product was dissolved in chloroform, and the crude product was purified by a silica gel column and then was eluted with a methanol/chloroform (volume ratio 3:1) mixed reagent. The solvent was removed by rotary evaporation at 70° C., and the resultant was lyophilized, to obtain a propyl cationic peptide lipid compound containing one alanine head.

[0085] (5) 10 mmol L-Orn was weighted and dissolved in 15 ml of acetonitrile; 80 mmol Boc.sub.2O was dissolved in acetonitrile, and the mixture was added dropwise to an acetonitrile solution of ornithine, and a complex was generated after reaction; 20 ml 20% sodium bicarbonate aqueous solution was added, and 2 g of anhydrous sodium carbonate and an appropriate amount of 8-hydroxyquinoline were added in batches; the mixture was stirred and reacted at room temperature for 4 hours to remove copper ions in the complex; then 10 mmol Fmoc-OSu was added to the aforesaid solution, followed by stirring at room temperature for 2 hours; the resultant was recrystallized with an ethyl acetate/petroleum ether system, to obtain a peptide head intermediate Fmoc-L-Orn (Boc)-OH.

[0086] (6) The cationic peptide lipid compound containing one alanine head prepared in step (4) was taken as a raw material to react with the amino protected ornithine heat intermediate Fmoc-L-Orn (Boc)-OH prepared in step (5) at a molar ratio of 1:4, followed by amino acid activation and amidation; wherein the specific reaction conditions and purification method are the same with steps (3) and (4). That is, a propyl cationic peptide lipid containing an Ala-Orn dipeptide cationic head, and an 18C double long carbon chain was obtained.

[0087] (7) 5 mmol L-Lys was weighted and dissolved in 30 ml of acetonitrile; 5 mmol Boc.sub.2O was dissolved in acetonitrile, and then the mixture was added dropwise to an acetonitrile solution of lysine; 1 mmol copper sulfate pentahydrate was added, and a (LysBoc).sub.2Cu complex was generated after the reaction; 10 ml 20% sodium bicarbonate aqueous solution was added, and 2 g of anhydrous sodium carbonate and an appropriate amount of 8-hydroxyquinoline were added in batches; the mixture was stirred and reacted at room temperature for 4 hours to remove copper ions in the complex; then 5 mmol Fmoc-OSu was added to the aforesaid solution, followed by stirring at room temperature for 2 hours; the resultant was recrystallized with an ethyl acetate/petroleum ether system, to obtain a peptide head intermediate Fmoc-L-Lys (Boc)-OH.

[0088] (8) The cationic peptide lipid compound containing an Ala-Orn dipeptide head prepared in step (6) was taken as a raw material to react with the amino protected lysine peptide head intermediate Fmoc-L-Lys (Boc)-OH prepared in step (7) at a molar ratio of 1:8, followed by amino acid activation and amidation; wherein the specific reaction conditions and purification method are the same with steps (3) and (4). That is, a propyl cationic peptide lipid R.sub.18AOKK containing four amino acid heads, and an 18C double long carbon chain was obtained, of which the structural characterization is shown by FIG. 7 and FIG. 8.

[0089] Its structural characteristics are as follows: .sup.1H NMR (400 MHz, CD.sub.3OD) δ: 0.88 (6H, CH.sub.3), 1.28 (60H, (CH.sub.2).sub.15), 2.94 (4H, CH.sub.2NH.sub.2), 3.16 (8H, CH.sub.2NH), 3.34 (2H, OCHCH.sub.2), 3.92 (2H, CHNH.sub.2), 4.15 (2H.sub.2OCH.sub.2CH), 4.33 (1H, CHNH), 4.89 (1H.sub.2OCHCH.sub.2). .sup.13C NMR (400 MHz, CD.sub.3OD) δ: 13.12 (CH.sub.3), 22.65 (CH.sub.3CH.sub.2), 28.85 ((CH.sub.2).sub.16), 39.13 (CH.sub.2NH), 40.34 (CH.sub.2NHCH), 40.99 (CH.sub.2NH.sub.2), 52.72 (CHNH, CHNH.sub.2), 63.78 (OCH.sub.2CH), 71.25 (OCH.sub.2CHO), 157.10 (NHCOO), 169.0 (NHCOCH). IRν/cm.sup.−1: 3435 (ν.sub.NH), 2925 (ν.sub.CH), 1675 (ν.sub.C═O), 1255 (ν.sub.CN).

[0090] From Example 1 to Example 4, it is easy for a person skilled in the art to see that all of the respective propyl cationic peptide lipids according to the invention and an alkyl alcohols feedstock can generate a propyl long carbon chain intermediate via acylating 3-amino-1,2-propanediol with an acylating agent diethylenetriamine, and that the intermediate undergoes the condensation reaction with a carboxyl group of an amino acid through esterification and amidation, to generate a propyl cationic peptide lipid containing 1 to 8 amino acids, followed by a series of similar separation and purification methods to remove impurities to obtain a pure product.

Example 5 Preparation of a Cationic Peptide Liposome Using R.SUB.12.O

[0091] 1 mg a cationic peptide lipid R.sub.12O was weighted and was dissolved together with cholesterol at a molar ratio of 8:1 in 1 ml trichloromethane solvent; after they were fully dissolved, the resultant solution was blown into a uniform thin film under nitrogen, and dried in vacuum for 12 hours so that the solvent totally volatilized (at a vacuum degree of −0.09 MPa, room temperature); 1000 μl of ultrapure water was added to perform hydration at about 80° C. for 2 hours; then, ultrasonic vibration was performed at the ultrasonic frequency of 100 Hz to be clear and transparent, to obtain a cationic peptide liposome in the concentration of 1 mg/ml.

Example 6 Preparation of a Cationic Peptide Liposome Using R.SUB.14.AO

[0092] 0.5 mg of a cationic peptide lipid R.sub.14AO was weighted and dissolved in 1 ml trichloromethane, and then a sucrose ester (a molar ratio of R.sub.14AO to sucrose ester is 1:1) was added; after they were fully dissolved, the resultant solution was blown into uniform thin film under nitrogen, and dried in vacuum for 4 hours so that the solvent totally volatilized (at a vacuum degree of −0.09 MPa, room temperature); the resultant product was immersed with 1 ml of ultrapure water for 6 hours to release the film, which was subjected to ultrasonic vibration at 20° C. (at the ultrasonic frequency of 100 Hz) to be clear and transparent, to obtain a cationic peptide liposome in the concentration of 0.5 mg/ml.

Example 7 Preparation of a Cationic Peptide Liposome Using R.SUB.16.OKK

[0093] 1.5 mg a cationic peptide lipid R.sub.16OKK was weighted and was dissolved together with a co-lipid DOPE (a molar ratio of R.sub.16OKK to DOPE is 2:1) in 1 ml trichloromethane; after they were fully dissolved, the resultant solution was blown into uniform thin film under nitrogen, and dried in vacuum for 8 hours so that the solvent totally volatilized (at a vacuum degree of −0.09 MPa, room temperature); 1 ml phosphate buffer was added to perform hydration for 4 hours; then, ultrasonic vibration was performed at 55° C. at the ultrasonic frequency of 100 Hz to be clear and transparent, to obtain a cationic peptide liposome R.sub.16OKK in the concentration of 1.5 mg/ml.

Example 8 Preparation of a Cationic Peptide Liposome Using R.SUB.18.AOKK

[0094] A cationic peptide lipid R.sub.18AOKK and DOPC (the cationic peptide liposome was 3 mg) at a molar ratio of 3:1 were accurately weighted and dissolved in 1 ml a mixture solvent of methanol and trichloromethane, wherein methanol:trichloromethane=1:2 (volume ratio); after they were fully dissolved, the resultant solution was blown into uniform thin film under nitrogen, and dried in vacuum for 5 h so that the solvent totally volatilized (at a vacuum degree of −0.09 MPa, room temperature); then, 200 μl absolute ethanol at approximately 55° C. was added to release the film; 800 μl a buffer was added, and ultrasonic vibration was repeatedly performed at about 35° C. (at the ultrasonic frequency of 100 Hz) to be clear and transparent, to obtain a cationic peptide liposome in the concentration of 3 mg/ml.

Example 9 Measurement of Particle Size and Zeta Potential of Liposomes

[0095] Particle Size and Zeta potential of the prepared cationic peptide liposomes were measured using a laser scattering particle size analyzer (HORIBA nanoparticle size analyzer SZ-100) under conditions of 25° C. and a light scattering angle of 90°. 20 μl of the cationic peptide liposomes prepared in Example 5 to Example 8 were taken by a pipette and diluted in 1 ml ultrapure water; they respectively underwent measurement of particle size and Zeta potential, and the results are shown in FIG. 9 and FIG. 10. FIG. 9 shows average particle size of four kinds of propyl peptide liposomes, and FIG. 10 shows Zeta potential of four kinds of propyl peptide liposomes.

[0096] As shown by the results, the liposomes formed from the four kinds of propyl cationic peptide lipids all had a particle size of about 100 nm, within the range of effective particle size for transfection(<1 μm), and the Zeta potential was positive, and its absolute value was larger than 30 mV, which proves that the liposomes had relatively good electrostatic stability.

Example 10 Preparation of a R.SUB.12.O Liposome/DNA Complex

[0097] A propyl cationic peptide liposome was prepared in the method as mentioned in Example 5. 0.5 μg of the 1 mg/ml liposome R.sub.12O was taken and diluted with a serum-free DMEM culture medium to 25 μl; 0.5 μg of 0.5 mg/ml plasmid DNA was taken and diluted with a serum-free DMEM culture medium to 25 μl; the two dilutions (a mass ratio of the liposome to DNA is 1:1) were mixed and slightly vortexed, incubated at room temperature for 10 min, to obtain a R.sub.12O liposome/DNA complex.

Example 11 Preparation of a R.SUB.14.AO Liposome/DNA Complex

[0098] A propyl cationic peptide liposome was prepared in the method as mentioned in Example 6. 1 μg of the 0.5 mg/ml liposome R.sub.14AO was taken and diluted with a serum-free DMEM culture medium to 25 μl; 0.5 μg of 0.5 mg/ml plasmid DNA was taken and diluted with a serum-free DMEM culture medium to 25 μl; the two dilutions (a mass ratio of the liposome to DNA is 2:1) were mixed and slightly vortexed, incubated at room temperature for 20 min, to obtain a R.sub.14AO liposome/DNA complex.

Example 12 Preparation of a R.SUB.16.OKK Liposome/DNA Complex

[0099] A propyl cationic peptide liposome was prepared in the method as mentioned in Example 7. 3.0 μg of the 1.5 mg/ml liposome R.sub.16OKK was taken and diluted with a serum-free DMEM culture medium to 25 μl; 0.5 μg of 0.5 mg/ml plasmid DNA was taken and diluted with a serum-free DMEM culture medium to 25 μl; the two dilutions (a mass ratio of the liposome to DNA is 6:1) were mixed and slightly vortexed, incubated at room temperature for 30 min, to obtain a R.sub.16OKK liposome/DNA complex.

Example 13 Preparation of a R.SUB.18.AOKK Liposome/DNA Complex

[0100] A propyl cationic peptide liposome was prepared in the method as mentioned in Example 8. 4.0 μg of the 3.0 mg/ml liposome R.sub.18AOKK was taken and diluted with a serum-free DMEM culture medium to 25 μl; 0.5 μg of 0.5 μg/μl plasmid DNA was taken and diluted with a serum-free DMEM culture medium to 25 μl; the two dilutions (a mass ratio of the liposome to DNA is 8:1) were mixed and slightly vortexed, incubated at room temperature for 40 min, to obtain a R.sub.18AOKK liposome/DNA complex.

Example 14 Preparation of a Propyl Cationic Peptide Liposome/siRNA Complex

[0101] Propyl cationic peptide liposomes were prepared in the methods as mentioned in Example 5 to Example 8. 0.9 μg of the 1 mg/ml R.sub.14AO was taken and diluted with a serum-free DMEM culture medium to 25 μl; 0.3 μg of the 0.3 μg/μl siRNA was taken and diluted with a serum-free DMEM culture medium to 25 μl; the two dilutions (a mass ratio of the liposome to siRNA is 3:1) were mixed and slightly vortexed, incubated at room temperature for 20 min, to obtain a R.sub.14AO liposome/siRNA complex.

Example 15 Electrophoretic Delay Experiment of the Combination of a Liposome and a Plasmid DNA

[0102] Agarose gel electrophoresis delay experiment was employed to detect corresponding charge ratios upon different mass ratios of the propyl cationic peptide liposomes to the plasmid DNA and further obtain an effective ratio for compression. The peptide liposomes and the plasmid DNA were diluted in 25 μl of a serum-free DMEM culture medium respectively according to a mass ratio being 0:1, 0.5:1, 1:1, 2:1. 3:1, 4:1, 6:1, 8:1; the dilutions were mixed and slightly vortexed, incubated at room temperature for 20 min; 2 μl of 6×DNA loading buffer was added in order to 20 μl of the above-mentioned complexes of peptide liposomes and plasmid DNA; the mixtures were uniformly mixed and loaded in order in loading holes of 1.2% agarose gel; the voltage was set to be 90 V to perform electrophoresis for 40 minutes. A nucleic acid dye solution NA-Red was added when the gel was prepared, so the DNA delay was directly observed in a gel imaging system Gene Genius Bio-imaging System (SYNGENE company). Electrophoresis results are shown in FIG. 11. Wherein, lanes 1 to 8 correspond to liposome/DNA complexes in which the mass ratios of the cationic peptide liposomes to DNA are 0:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 6:1, 8:1, respectively. A is an electrophoretogram of the combination of a propyl peptide liposome R.sub.16OKK and DNA, B is an electrophoretogram of the combination of a propyl peptide liposome R.sub.18AOKK and DNA, C is an electrophoretogram of the combination of a propyl peptide liposome R.sub.12O and DNA, and D is an electrophoretogram of the combination of a propyl peptide liposome R.sub.14AO and DNA.

[0103] As shown by results in FIG. 11, peptide liposomes prepared from R.sub.16OKK, R.sub.18AOKK and R.sub.14AO all can effectively compress pDNA. Along with gradual increase in the concentration of the peptide liposomes, free DNA bands are gradually weakened, and when N/P is larger than 2:1, DNA can be completely compressed by the liposome. The liposome prepared from R.sub.12O has relatively poor capability of compressing DNA.

Example 16 In Vitro Biological Evaluation Experiments

[0104] (1) Experiment of Carrying pGFP-N2 Plasmid to Transfect Cells

[0105] Hep-2 cells were seeded in a 24-well cell culture plate; the cell concentration per well was about 1.0×10.sup.5; after incubation for 24 h, the cell density became 80 to 90% on the transfection date. The liposome and the pGFP-N2 plasmid were combined respectively according to a ratio of 1:1, 2:1, 3:1, 4:1, 6:1 and 8:1, and the total volume after the combination was 100 μl. The resultant complexes were added to a cell culture plate and cultured for 4 to 5 hours; then the culture medium was replaced with a culture medium containing 10% serum and antibiotics, followed by culturing for 48 hours. A product GFP expressed by a green fluorescent protein gene could lase green fluorescence with a peak of 508 nm. An inverted fluorescence microscope was used to analyze the gene expression. Positive cells emitted bright green fluorescence, while negative cells none. The more GFP positive cells are, the stronger signal becomes, indicating higher transfection efficiency. The observation magnification is 20×10.

[0106] The results are shown in FIG. 12. When the mass ratio of the liposome and DNA was 3:1, the liposome could transfect Hep-2 cells at high efficiency, and the intensity of the green fluorescence is obviously higher than that of the urethane-type cationic liposome DDCTMA, and the intensity of the green fluorescence protein is significantly increased as compared with a commercial reagent Lipofectamine 2000.

[0107] (2) Experiment of Carrying pGL-3 Plasmid to Transfect Cells

[0108] The method of culturing cells is the same as the above-mentioned step (1). The liposome and the pGL-3 plasmid were combined respectively according to a ratio of 1/1, 2/1, 3/1, 4/1, 6/1 and 8/1, and the total volume after the combination was 100 μl. The resultant complexes were added to a cell culture plate, which was gently shaken to mix the complexes uniformly. Then, culturing was performed under 5% CO.sub.2 (incubator) at 37° C. for 4 to 5 hours; then the culture medium was replaced with a culture medium containing 10% serum and antibiotics, followed by culturing for 48 hours. After the transfection, the cells were washed with DPBS once; 600 μl lysate was added to each well; after 20 min, the cells were transferred to a 96-well whiteboard, and 80 μl Promega E151A detection fluid was added to each well. The relative enzyme activity was detected by Synergy 2 multifunctional microplate reader (BioTek). The total protein content was measured using Pierce BAA Protein Assay kit of Thermo Electron as a standard control. After the measurement of protein, the transfection efficiency can be expressed as RLU/mg protein.

[0109] Results of the experiments are shown in FIG. 13. The four liposomes all can carry pGL3 plasmid to transfect Hep-2 cells, and the transfection efficiency was higher than that of the urethane-type cationic liposome DDCTMA. Wherein, the liposome R.sub.16OKK had the highest transfection efficiency when N/P was 4:1, and it was 2.5 times as high as the transfection efficiency of the urethane-type cationic liposome DDCTMA, it was twice as high as the transfection efficiency of the commercial reagent Lipofectamine 2000, and it was 10 times as high as the transfection efficiency of DOTAP.

[0110] (3) RNA Interference Experiments

[0111] Cell plating was not counted, and substantially confluent A549 cells were taken and added to a 12-well plate by 2 ml per well, and cultured for 24 h to a cell density of about 50 to 60%. 200 μl of a liposome/siRNA complex was added to each well to perform transfection for 18 h; then, the resultant product was changed to be cultured in a growth culture medium for 30 h. Then, the cells were washed with DPBS once; 600 μl lysate was added to each well; after 20 mins, 20 μl cells per well were transferred to a 96-well whiteboard, and 80 μl promega E151A detection fluid was added to each well. The relative enzyme activity was detected by a multifunctional microplate reader (BioTek). 5 μl lysate was added to a 96-well transparent plate, and a total protein content was measured using Pierce BAA Protein Assay kit of Thermo Electron as a standard control.

[0112] FIG. 14 shows the capability of silencing Luciferase gene when A549 cells were transfected by four kinds of propyl peptide liposomes carrying siRNA. siRNA and Control are controls. As shown by the results, after A549 cells were transfected by the four kinds of propyl peptide liposomes, the expression level of Luciferase gene were inhibited to different degrees, and the silencing efficiency increased by about 40 to 50% as compared with the commercial reagent Lipofectamine 2000. Wherein, liposome R.sub.16OKK/siRNA and R.sub.18AOKK/siRNA resulted in the luciferase gene silencing efficiency of 60 to 75% as compared with the blank control, and resulted in the significantly improved silencing efficiency, compared with the urethane-type cationic liposome/gene complex DDCTMA and the commercial reagent DOTAP.

[0113] (4) Study of Cytotoxicity (MTT Colorimetry)

[0114] MTT method was used to perform cytotoxicity test on cationic liposomes having the relatively high transfection efficiency, and the commercial cell-transfecting reagents Lipofectamine 2000 and DOTAP were taken as controls. Hep-2 cells were seeded in a 96-well cell culture plate, and 100 μl cell culture medium (containing double antibody and serum) was added to each well, the concentration being about 1.0×10.sup.6 cells per well; culturing was performed for 24 hours so that the cell density became 80 to 90% on the transfecting date. The growth culture medium was removed, and the resultant was washed with 100 μl culture medium, which was then replaced with equivalent (100 μl) culture medium. The liposomes and the plasmid DNA were combined according to a ratio of 1:1, 2:1, 3:1, 4:1, 6:1, 8:1, respectively and added to a cell culture plate. After cell culture for 24 hours, 20 μl MTT (Sigma, 5 mg/ml) was added to each well to culture and incubate for 4 to 4.5 h. Then the culture medium was discarded, and 150 μl DMSO was added to make cells lysis, and its absorbance was measured by microplate reader at a wavelength of 570 nm. Taking the absorbance of the blank control (non-transfected cells) as 100%, percentage of survival transfected cells was calculated according to a calculation formula: cell survival rate (%)=[A].sub.sample/[A].sub.control×100%.

[0115] The experiment results are shown in FIG. 15, in which the horizontal ordinate represents the prepared propyl cationic peptide liposomes, and the mass ratio of the liposomes to DNA is 1:1 to 8:1. The four liposomes all had little toxicity to Hep-2 cells, and the cell survival rates were 90 or more. The cell survival rates were significantly improved, compared to the urethane-type cationic lipid gene complex (DDCTMA), the commercial reagents Lipofectamine 2000 and DOTAP.