Liposome Formulation of Paclitaxel with Enhanced Solubility and Stability

Figures & data

FIG. 1 The effect of CH-to-lipid molar ratio on (A) the entrapment efficiency (%) of paclitaxel in the liposomes and (B) the changes of the mean particle size of liposome containing 10% cholesterol (molar percent to lipid). The liposomes were prepared using 5.4% (w/v) S₁₀₀PC with various CH-to-lipid molar ratio of cholesterol. The amount of paclitaxel loaded in the formulation was 0.6 mg/mL, and the hydration medium was PBS (pH 4.0) containing 3.0% (v/v) of Tween 80.

TABLE 1 Effect of lipid and paclitaxel contents on the entrapment of paclitaxel in the liposome

		Amount of paclitaxel (mg/mL)
Lipid	Lipid content (%, w /v)	Loading in formulation^a	In final liposome solution^b	EE%^c	Mean particle size (nm)	Lipid/paclitaxel molar ratio^d
S75PC	5.40	0.60	0.40 ± 0.01	54.98 ± 0.03	178.9 ± 3.4	102.69
	5.40	1.00	0.83 ± 0.02	55.13 ± 1.53	183.4 ± 4.4	61.62
	5.40	1.50	1.13 ± 0.03	54.67 ± 2.26	186.1 ± 1.6	41.08
	5.40	2.00	1.82 ± 0.02	55.96 ± 1.54	190.0 ± 2.1	30.81
	5.40	2.50	1.90 ± 0.08	38.83 ± 0.30	223.0 ± 5.9	24.65
	6.00	2.00	1.78 ± 0.04	63.30 ± 0.83	186.0 ± 2.6	34.23
	7.00	2.00	1.77 ± 0.02	67.35 ± 0.54	189.7 ± 2.8	39.94
	8.50	2.00	1.72 ± 0.01	70.35 ± 1.98	190.3 ± 4.9	48.49
	10.00	2.00	1.76 ± 0.03	72.64 ± 0.56	188.9 ± 4.7	57.05
	12.00	2.00	1.81 ± 0.03	84.65 ± 3.23	191.9 ± 5.0	68.46
S100PC	5.40	0.60	0.44 ± 0.02	54.42 ± 1.31	177.5 ± 3.2	102.69
	5.40	1.00	0.87 ± 0.04	56.20 ± 1.29	178.4 ± 3.3	61.62
	5.40	1.50	1.05 ± 0.001	54.22 ± 1.37	175.3 ± 1.6	41.08
	5.40	2.00	1.56 ± 0.01	56.74 ± 2.23	180.2 ± 2.0	30.81
	5.40	2.50	1.66 ± 0.03	41.61 ± 2.33	220.0 ± 6.1	24.65
	6.00	2.00	1.65 ± 0.02	59.77 ± 1.60	182.5 ± 4.1	34.23
	7.00	2.00	1.57 ± 0.03	65.60 ± 0.95	176.2 ± 3.4	39.94
	8.50	2.00	1.61 ± 0.02	70.08 ± 2.48	181.5 ± 3.0	48.49
	10.00	2.00	1.70 ± 0.01	75.36 ± 0.56	181.1 ± 3.4	57.05
	12.00	2.00	1.78 ± 0.03	76.87 ± 0.42	185.7 ± 3.2	68.46

The liposomes were prepared using S₇₅PC or S₁₀₀PC with cholesterol (cholesterol-to-lipid molar ratio = 10:90). The hydration medium was PBS (pH 4.0) containing 3.0% (w/v) of Tween 80.

Data represent the mean ± standard deviation of three or more determinations.

^aInitial paclitaxel content loaded in the liposome formulations.

^bFinal paclitaxel content in liposome solutions after filtration using the extruder (0.2 μ m pore size).

^cEE(%) = amount of paclitaxel in liposome pellet (μ g)/amount of paclitaxel in liposome suspension (μ g)× 100

^dActual amount of paclitaxel was determined after separating liposome using ultrafiltration method.

FIG. 2 Effect of lipid types on the entrapment efficiency (%) of paclitaxel and paclitaxel content in liposome (%). The liposomes were prepared using 10% (w/v) of various lipids with cholesterol (CH-to-lipid molar ratio = 10:90) and were loaded with 3.5 mg/mL paclitaxel (lipid-to-paclitaxel molar ratio is 32.6). The hydration medium was PBS (pH 4.0) containing 3.0% (v/v) of Tween 80.

TABLE 2 Effect of PEG 400 on the entrapment of paclitaxel in the liposome

Lipid	PEG 400 (%, v/v) in hydration medium	Zeta potential (mV)	EE (%)	Paclitaxel in liposome solution (mg/mL)	Paclitaxel content in liposome (%)^a
S100PC	0	−7.93 ± 0.78	70.83 ± 2.75	3.39 ± 0.27	2.09 ± 0.12
	2	−7.08 ± 0.14	75.63 ± 2.84	3.18 ± 0.06	2.14 ± 0.09
	5	−6.42 ± 0.80	89.26 ± 3.05	3.18 ± 0.07	2.53 ± 0.07

The liposomes were prepared using 10% (w/v) of phosphatidylcholine (S₁₀₀PC), cholesterol (cholesterol-to-lipid molar ratio = 10:90) and 3.5 mg/mL of paclitaxel. The hydration medium was phosphate buffer saline (pH 4.0) containing 3.0% (v/v) Tween 80.

Data represent the mean ± standard deviation of three independent determinations.

^aContent(%) = amount of paclitaxel in freeze - dried liposome (mg)/amount of freeze - dried liposome (mg)× 100

*p < 0.05, compared with the liposome without PEG 400.

FIG. 3 (A) Effect of sucrose on the change of the mean particle size of liposome before (•) and after (ˆ) freeze drying. The liposomes were prepared using 10%% (w/v) of S₁₀₀PC with cholesterol (CH-to-lipid molar ratio = 10:90) and were loaded with 3.5 mg/mL paclitaxel. The hydration medium was PBS (pH 4.0) containing 3.0% (v/v) Tween 80 and 5% (v/v) PEG 400. Liposome particles were separated by ultrafiltration and were suspended with distilled water containing various concentrations (molar ratio to lipid) of sucrose before freeze drying. (B) Change of particle size of liposome containing sucrose as a lyoprotectant (sugar-to-lipid molar ratio = 2.3) at room temperature when freeze-dried liposome powder was reconstituted with 0.9% (w/v) NaCl solution.

TABLE 3 Cytotoxicity of paclitaxel in 1:1 blend of Cremophor® EL and ethanol (Taxol®) and in various liposome formulations against MDA-MB-231 human breast cancer cells after 24 h incubation

Type of lipid	Zeta potential (mV)	IC50 (nM)
Control (free paclitaxel)	—	133.57 ± 5.88
S100PC only	−6.42 ± 0.80	140.59 ± 8.48
S100PC+8% stearylamine	20.00 ± 1.15	117.19 ± 10.14^+
S100PC+1% phosphatidylserine	−11.60 ± 2.25	165.02 ± 11.80^+

The liposomes were prepared using 10% (w/v) of S₁₀₀PC with cholesterol (cholesterol-to-lipid molar ratio = 10:90) and 5% PEG 400, and were loaded with various concentrations of paclitaxel. The hydration medium was PBS (pH 4.0) containing 3.0% (v/v) of Tween 80. Sucrose (sugar-to-lipid molar ratio = 2.3) was added as a lyoprotectant.

Data represent the mean ± standard deviation (n = 4–6).

*;p < 0.05 compared with the control.

+;p < 0.05 compared with S₁₀₀PC only group.