Liposomes prolong the therapeutic effect of anti-asthmatic medication via pulmonary delivery

Figures & data

Table 1 Effect of SPC content in VPG on the liposome particle sizes and the EE of SBS in the liposome suspension (mean ± SD, n = 3)

SPC/VPG (mg/g)	EE%a	Particle size (nm)
250	35.12 ± 0.99	33 ± 5.0
300	40.47 ± 0.14	47 ± 10
400	57.11 ± 0.11	57 ± 21
500	58.92 ± 0.07	58 ± 26

Note:

a P < 0.05 for comparison between any two groups using ANOVA test.

Abbreviations: EE, encapsulation efficiency; SBS, salbutamol sulfate; SD, standard deviation; SPC, soybean phosphatidylcholine; VPG, vesicular phospholipid gel.

Table 2 Optimization of EE (mean ± SD, n = 3) of SBS in VPG liposomes by hydration with different concentrations of isotonic agents

Isotonicagent	Concentration		EE (%)
	mg/mL	M
Glucose	19.2	0.11	60.32 ± 0.37
	38.4	0.21	61.52 ± 0.11
	50.4	0.28	63.99 ± 0.64
	76.8	0.43	65.75 ± 0.46
	115.2	0.64	66.29 ± 1.57
Mannitol	19.2	0.11	65.27 ± 0.60
	38.4	0.21	62.53 ± 0.81
	50.4	0.28	62.45 ± 0.87
	76.8	0.43	65.60 ± 0.56
	115.2	0.64	63.22 ± 1.20
Trehalose	19.2	0.06	61.09 ± 0.15
	38.4	0.11	61.95 ± 0.69
	76.8	0.22	60.71 ± 0.65
	95.8	0.28	64.50 ± 0.75
	115.2	0.34	65.27 ± 0.60
Lactose	19.2	0.06	60.46 ± 3.01
	38.4	0.11	63.70 ± 0.23
	76.8	0.22	70.71 ± 1.55a
	95.8	0.28	69.84 ± 0.77
	115.2	0.34	67.03 ± 0.47

Notes: The SBS concentration used for preparation of VPG liposomes was 83.4 mg/g. The average molar concentration of SBS in the aqueous phase of VPG was 0.28 M.

a P < 0.05 for comparison with other groups except for the molar concentration of lactose 0.28 M using analysis of variance test.

Abbreviations: EE, encapsulation efficiency; SBS, salbutamol sulfate; SD, standard deviation; VPG, vesicular phospholipid gel.

Figure 1 Effect of liposomes on the transport rate of SBS across Asian toad pulmonary membrane in vitro.

Notes: The concentrations of SBS in liposome suspension (●) and control solution (Δ) were 2.11 mg/mL and 2.22 mg/mL, respectively. Data were expressed as mean ± SD (n = 3).

Abbreviations: SBS, salbutamol sulfate; SD, standard deviation.

Figure 2A Fluorescence imaging of DiR SBS liposome disposition in rat lungs at different time points after intratracheal administration.

Abbreviations: SBS, salbutamol sulfate; DiR, 1,1′-dioctadecyltetramethyl indotricarbocyanine lodide.

Figure 2B Decrease of fluorescence intensity of DiR SBS liposomes in rat lungs after intratracheal administration.

Note: n = 3 for each time point.

Abbreviations: SBS, salbutamol sulfate; DiR, 1,1′-dioctadecyltetramethyl indotricarbocyanine iodide.

Table 3 Pharmacokinetic analysis of SBS in the plasma of rats after pulmonary administration of SBS liposome formulation or free SBS solution

Parameters	Liposome SBS	Free SBS solution
AUC0-∞ (ng/mL × h)	1376.58 ± 598.22	1471 ± 733.88
MRT (h)a	18.73 ± 2.54	8.09 ± 2.65
Cmax (ng/mL)	168.45 ± 77.94	1139.78 ± 180.61
Tmax (h)	2.38 ± 0.89	–b

Notes: Data were expressed as mean ± SD (n = 5).

a Student’s t-test: liposome SBS versus free SBS solution, P < 0.05;

b there was no T_max for free SBS solution.

Abbreviations: MRT, mean residence time; AUC_{0 h–∞}, area under the curves from time zero to infinity; SBS, salbutamol sulfate; SD, standard deviation.

Figure 3 SBS concentration in the plasma of rats at different time points after pulmonary administration of SBS liposome formulation or free SBS solution.

Note: Data were expressed as mean ± SD (n = 5).

Abbreviations: SBS, salbutamol sulfate; SD, standard deviation.

Table 4 Parameters of the various formulations of SBS in rat lungs after pulmonary administration (mean ± SD, n = 3)

Parameters	Liposome SBS	Free SBS solution
AUC0–∞ (μg/g × h)a	1061.37 ± 27.20a	173.05 ± 21.36
MRT (h)a	21.85 ± 1.41a	3.27 ± 0.07
Clearancea	6.39 ± 0.20a	44.31 ± 4.32

Notes:

a Student’s t-test: liposome SBS versus free SBS solution, P < 0.05.

Abbreviation: AUC_{0 h–∞}, area under the curves from time zero to infinity; MRT, mean residence time; SBS, salbutamol sulfate; SD, standard deviation.

Figure 4 SBS concentration in the lungs of rats at different time points after pulmonary administration of SBS liposome formulation or free SBS solution.

Note: Data were expressed as mean ± SD (n = 3).

Abbreviations: SBS, salbutamol sulfate; SD, standard deviation.

Figure 5 Anti-asthmatic effect periods in guinea pigs given saline, SBS solution, or SBS liposomes (n = 6 per group) before spraying of 0.4% histamine saline solution for 20 seconds at the rate of 70 L/minute.

Note: Anti-asthmatic effect was considered to be present when the animal did not twitch and fall down for at least 15 minutes (asthma latent period) after histamine treatment.

Abbreviation: SBS, salbutamol sulfate.