Novel mucus-penetrating liposomes as a potential oral drug delivery system: preparation, in vitro characterization, and enhanced cellular uptake

Figures & data

Figure 1 Particle size and zeta potential of liposomes with different amounts of Pluronic^®.

Table 1 Particle size, polydispersity, and zeta potential of unmodified liposomes, Pluronic^® PF127-inlaid liposomes, and Pluronic PF127-adsorbed liposomes

Formulation	Mean diameter (nm)	PI	Zeta-potential (mV)
Unmodified liposomes	191.7 ± 11.2	0.195 ± 0.011	−8.93 ± 1.67
PF127-inlaid liposomes	185.6 ± 8.9	0.103 ± 0.005	−4.12 ± 2.32
PF127-adsorbed liposomes	203.2 ± 13.7	0.206 ± 0.034	−3.54 ± 1.37

Note: Data were shown as mean ± standard deviation (n = 3).

Abbreviation: PI, polydispersity index.

Figure 2 (A) Transmission electron micrographs of unmodified liposomes, Pluronic^® F127-inlaid liposomes and Pluronic F127-adsorbed liposomes. (B) Particle size change in liposomes after incubation at 37°C for 2 hours and 4°C for 2 hours or 12 hours. (C) Influence of Triton X-100^® on relative absorbance at 400 nm of unmodified liposomes (■), PF127-inlaid liposomes (●), and PF127-adsorbed liposomes (▾).

Figure 3 (A) Cumulative amounts of coumarin 6 in liposomes transported through intestinal mucus as a function of time. Unmodified liposomes (■), Pluronic^® F127-inlaid liposomes (●), Pluronic F127-adsorbed liposomes (▾). (B) Percentage of cumulative amounts of coumarin 6 loaded in liposomal formulations transported through intestinal mucus layer after one hour (n = 3; data shown as the mean ± standard deviation).

Abbreviations: lip, unmodified liposomes; PBS, phosphate-buffered solution.

Table 2 Permeability value for coumarin 6-loaded unmodified liposomes, Pluronic^® PF127-inlaid liposomes and Pluronic PF127- adsorbed liposomes transported through intestinal mucus

Formulation	Papp (×10^−7cm/s)	R
Unmodified liposome	1.88 ± 0.23	–
PF127-inlaid liposomes	12.37 ± 1.05	6.58 ± 0.56
PF127-adsorbed liposomes	11.64 ± 1.16	5.84 ± 0.62

Notes: Data shown as mean ± standard deviations (n = 3).

Abbreviations: P_app, the apparent permeability coefficient; R, permeation enhancement ratio.

Figure 4 Confocal laser scanning microscopy and flow cytometry histogram of cellular uptake of coumarin 6-loaded liposomes, Pluronic^® F127-inlaid liposomes, and Pluronic F127-adsorbed liposomes (green fluorescence) into Caco-2 cells. Nuclear staining was performed by DAPI (blue staining). The image was representative of three experiments with similar results.

Figure 5 Effects of the different endocytotic inhibitors and temperature on the uptake of unmodified liposomes (A), Pluronic^® F127-inlaid liposomes (B), and Pluronic F127-adsorbed liposomes (C) into Caco-2 cells.

Abbreviations: M-βCD/TV, methyl-β-cyclodextrin + lovastatin; CPZ, chlorpromazine; CYD, cyclochalasin D; lip, liposomal nanocarriers.

Figure 6 Schematic presentation of different liposomal nanocarriers. Green represents the polyethylene oxide chain of Pluronic^® F127; red represents the polyoxypropylene chain of Pluronic F127.