6. Novel Polyglycerin-Phospholipids for Decomposable Liposomes
For pH sensitive Liposome
SUNBRIGHT DSPE-PG8 series designs for pH-sensitive Liposomal drug.
Use of these lipids enables researchers to obtain highly efficient pH-sensitive carriers for efficient cytoplasmic delivery of bioactive molecules. As the example of carriers, we have designed pH-sensitive liposomes. These liposomes are stable at physiological pH, but become destabilization and/or fusogenic under acidic conditions.
Mechanism action of pH-sensitive liposomes obtained from DSPE-PG8 series
New "Decomposable Liposome" by using DSPE-PG8 series shows very high responsibility at slightly acidic condition, around pH7.0 and effective releasability of the encapsulated drugs.
【Procedure】 Pyranine loaded liposomes (lipid concentration 0.02mM) were added to 25 mM MES and 125 mM NaCl buffer of varying pHs at 37℃ and fluorescence intensity of the suspension was monitored by using a spectrofluorometer after 15 minutes of adding. 100% release was achieved by adding Triton X- 100 (final concentration 0.1 %) to the liposome suspension.
Cytoplasmic delivery of fluoresccent dye by pH-sensitive liposomes
【Procedure】 Rhodamine-DPPE(Rh-PE), EPC and/or DSPE-PG8MG were taken in eggplant flask as content of Rh-PE 0.1 molar percent, appropriate amount of solvent was placed therein, and the content was dissolved at 40°C. Next, the solvent was distilled off under reduced pressure using a rotary evaporator to yield a lipid film. Then, pyranine 47.5mM dissolved buffer solution (pH 7.4) was added, and the lipid was hydrated with stirring. DC 2.4 cells(1×105) were seeded on glass-bottomed culture dishes and incubated for two days. The cells were washed with PBS and reincubated with fresh medium(500μl). Then, the liposomes suspension(1.0mM of liposomal lipid, 500μl) were added to the dishes (final concentration of liposomal lipid: 0.5mM), and the cells were incubated for 4h. After the incubation with the liposomes, the ceIls were washed with PBS and were observed using a confocal laser scanning microscope(CLSM).