In Vivo Evaluation of Novel pH-sensitive mPEG-Hz-Chol Conjugate in Liposomes: Pharmacokinetics, Tissue Distribution, Efficacy Assessment

Figures & data

Scheme 1. pH-sensitive liposomes following the change of pH value.

Scheme 2. The structure of mPEG-Hz-Chol.

Table 1. Stability of plain liposomes and pH-sensitive liposomes with change of particle sizes with different media at 37°C for 1 h, 12 h, 24h

		Plain liposomes		pH-sensitive liposomes
	Time (h)	PBS	PBS+FBS	PBS	PBS+FBS
Before freez-drying	1	138.5±3.8	140.4±4.1	137.6±4.5	142.3±4.3
	12	175.1±5.7	224.6±7.2	185.4±8.1	246.8±7.9
	24	213.7±6.5	258.9±6.3	237.5±5.9	284.2±8.8
After freez-drying	1	157.1±6.8	198.6±9.3	181.5±6.8	234.7±8.7
	12	226.4±6.3	247.6±7.7	238.9±8.1	245.2±9.3
	24	312.6±9.5	346.8±6.8	294.2±5.4	322.7±8.5

Figure 1. Plasma concentration profiles of PTX after intravenous administration in rats. Taxol^®(PTX-INJ ▀), PTX in plain liposome (PTX-PL •) and modified liposome (PTX-ML ▴). (mean±S.D., n = 5)

Table 2. The main pharmacokinetics parameters after intravenous administration of injection, PL and ML to rats (mean±S.D. n=5)

		Plain	Modified
Parameters	Taxol^®	Liposomes	Liposomes
tl/2α(h)	0.12±0.06	0.16±0.15	0.16±0.06
tl/2β(h)	1.93±0.64	2.22±1.24	3.64±1.38*
V(L/kg)	0.40±0.28	0.26±0.20	0.33±0.16
CL(L/h/kg)	0.46±0.10	0.34±0.09	0.16±0.11*
AUC((mg/ml)h)	15.80±3.31	21.96±7.82	23.06±3.60*
MRT(h)	1.55±0.53	2.46±0.99	3.31±0.54*

* Significantly different from Taxol^® (p<0.05).

Table 3. AUC (0-tn) ((mg/ml)*h or (mg/g)*h) of PTX in blood and tissues (n=6)

Tissue	Taxol^®	PTX-PL	PTX-ML
Blood	29.2788	42.4602	88.1039
Heart	60.293	49.0285	36.2822
Liver	224.0518	890.5646	534.0974
Spleen	69.3386	456.7069	224.5975
Lung	96.9596	121.4949	80.9712
Kidney	53.4846	50.9218	91.0696

Table 4. MRT (0-tn) (h) of PTX in blood and tissues (n = 6)

Tissue	Taxol^®	PTX-PL	PTX-ML
Blood	1.2322	2.7616	5.4299
Heart	2.1977	2.2973	2.4284
Liver	2.2374	7.8998	6.3563
Spleen	2.436	6.5144	7.3836
Lung	2.4401	4.4692	3.6345
Kidney	1.61	2.6644	5.0527

Table 5. In vivo antitumor effect of Taxol ^®, plain liposomes and pH-sensitive liposomes in tumor bearing mice model

	Body weight (g)		Tumor value (cm ^3)
Drug	Before i.v.	After i.v.	Before i.v.	After i.v.	Tumor weight (g)
Saline	21.91±0.07	25.00±1.58	0.14±0.02	1.17±0.20	0.52±0.12
Taxol	24.59±1.48	24.56±0.25	0.17±0.09	0.71±0.26*	0.31±0.03*
Plain liposomes	24.50±1.12	22.44±1.01	0.16±0.07	0.67±0.22*	0.26±0.08*
pH-sensitive liposomes	24.13±1.36	22.13±0.83	0.15±0.06	0.62±0.19*	0.21±0.10**

Data represent mean value±SD, n=5.

*p< 0.05, **p < 0.01, compared with normal saline group.

Figure 2. The PTX concentration of three groups (Taxol, PTX-PL and PTX-ML) in tissues at different time points (0.25, 0.5, 1, 2, 4, 6, 8, 12, 24 h) (mean±S.D., n = 6).

Figure 3. Change of body weight after injection in BALB/c mice inoculated with Heps cancer cells. Taxol^® (•), plain liposome (▴) and pH-sensitive liposome (▾) was intravenously injected (20 mg/kg). Normal saline (▀) was injected as a control. The zero point of X-axis indicates the first day of PTX injection. Each data represents the mean±standard deviation (n = 5).

Figure 4. The effect of PTX on the inhibition of tumor growth in BALB/c mice inoculated with Heps cancer cells. Taxol^® (•), plain liposome (▴) and pH-sensitive liposome (▾) was intravenously injected (20 mg/kg). Normal saline (▀) was injected as a control. The zero point of X-axis indicates the first day of PTX injection. Each data represents the mean±standard deviation (n = 5).

Figure 5. Pathology section of tumor with different PTX formulation. Normal saline as a control (A), Taxol^® (B), plain liposome (C) and pH-sensitive liposome (D). (hematoxylin and eosin,original magnification ×200).