Influence of phospholipid types and animal models on the accelerated blood clearance phenomenon of PEGylated liposomes upon repeated injection

Figures & data

Table 1. The injection project of effect of different type of phospholipids on ABC phenomenon in rats.

	First injection (empty liposomes)	Second injection (calcein liposomes)
A	NS	SPC
B	NS	EPC
C	NS	ESM
D	NS	DPPC
E	NS	HSPC
F	SPC	SPC
G	EPC	EPC
H	ESM	ESM
I	DPPC	DPPC
J	HSPC	HSPC

Table 2. Mean particle sizes and entrapment efficiency of the prepared liposomes (n = 6).

		Particle size of first dose		Particle size of second dose
Type of phospholipid	Entrapment efficiency (%)	Aved (nm)	PDI	Aved (nm)	PDI
SPC	22.7 ± 2.18	104.7 ± 8.2	0.234 ± 0.012	117.1 ± 9.3	0.162 ± 0.007
EPC	27.4 ± 1.24	97.3 ± 6.3	0.229 ± 0.017	120.3 ± 10.2	0.145 ± 0.008
ESM	23.3 ± 1.36	108.5 ± 5.5	0.168 ± 0.008	113.3 ± 11.7	0.164 ± 0.009
DPPC	16.5 ± 0.93	115.7 ± 10.1	0.236 ± 0.013	100.5 ± 4.3	0.217 ± 0.012
HSPC	17.1 ± 1.45	119.8 ± 12.7	0.187 ± 0.009	115.5 ± 7.4	0.157 ± 0.005

Figure 1. Blood clearance (0–4 h) of calcein in rats after a second injection of PEGylated liposomes made of different types of phospholipid (n = 6).

Figure 2. Liver (A) and spleen (B) biodistribution (4 h) of calcein in rats after a second injection of PEGylated liposomes made of different types of phospholipid (n = 6) (**p < 0.01).

Table 3. Change of pharmacokinetics parameters in rat after repeated injections of PEGylated liposomes made of different types of phospholipids (n = 6).

Type of phospholipid	AUCC/E	t1/2C/E
SPC	4.28^a,b	5.67^a,b
EPC	5.25^a,b	5.61^a,b
ESM	2.81^c,d	4.09^c,d
DPPC	1.84	3.28
HSPC	1.78	3.85

AUC_C/E: ratio of AUC of control group and experimental group; t_1/2C/E: ratio of t_1/2 of control group and experimental group. Unsaturated PL was compared with DPPC: ^ap < 0.1, ^cp < 0.05; unsaturated PL was compared with HSPC: ^bp < 0.01, ^dp < 0.05.

Figure 3. Anti-PEG IgM response following a single intravenous injection of empty PEGylated liposomes made of different types of phospholipids in rats (n = 6) (**p < 0.01).

Figure 4. Blood clearance (0–4 h) (A) and liver (B) and spleen (C) biodistribution (4 h) of calcein in mice after a second injection of PEGylated EPC liposomes (n = 6) (*p < 0.05, **p < 0.01).

Figure 5. Blood clearance (0–4 h) (A) and biodistribution (4 h) (B) of calcein in rabbits after a second injection of PEGylated EPC liposomes (n = 6) (**p < 0.01).

Figure 6. Blood clearance (0–4 h) and biodistribution (4 h) of calcein in guinea pigs after a second injection of PEGylated EPC liposomes (n = 6) (**p < 0.01).

Table 4. Change of pharmacokinetics parameters in different animal models after repeated injections of PEGylated liposomes (n = 6).

Type of animals	AUCC/E	t1/2C/E
Rat	5.25^a,b	5.61^a,b
Mice	4.64^a,b	4.25^a,b
Rabbits	2.44	1.98
Guinea pigs	1.83	1.72

AUC_C/E: ratio of AUC of control group and experimental group; t_1/2C/E: ratio of t_1/2 of control group and experimental group. PK of rats and mice was compared with those of rabbits: ^ap < 0.1; PK of rats and mice was compared with those of guinea pigs: ^bp < 0.01.

Table 5. Change of anti-PEG IgM level in different animals after a single intravenous injection of empty PEGylated liposomes in different kinds of animals (n = 6).

Type of animals	OD value of control group	OD value of experimental group
Rats	0.46 ± 0.08	1.57 ± 0.14^a
Mice	0.10 ± 0.07	1.14 ± 0.13^a
Rabbits	0.44 ± 0.12	1.34 ± 0.14^a
Guinea pigs	0.28 ± 0.03	0.68 ± 0.06^a

^ap < 0.01.