Spontaneous preparation of small unilamellar liposomes

Claim 1

A process for the spontaneous preparation of small unilamellar liposomes comprising, without additional energy input, dispersing (a) a homogeneous layer of a phospholipid of the formula ##STR2## wherein m is zero or one, one of R 1 and R 2 is hydrogen, hydroxy or C 1 -C 4 -alkyl and the other is alkyl, alkenyl, alkoxy or alkenyloxy, each of 10-20 carbon atoms, or is acyloxy of 10-50 carbon atoms, R 3 is hydrogen or C 1 -C 4 -alkyl, and R 4 is hydrogen, C 1 -C 7 -alkyl, carboxy-lower alkyl, 2-aminoethyl, 3- amino-n-propyl, 2-methylaminoethyl, 3-methylamino-n-propyl, 2-dimethylaminoethyl, 3-dimethylamino-n-propyl, 2-amino-2-carboxyethyl, 3-amino-3-carboxy-n-propyl, 2-trimethylammonioethyl, 2-triethylammonioethyl, 3-tri-methylammonio-n-propyl, 3-triethylammonio-n-propyl, 2-hydroxyethyl, 2,3-dihydroxypropyl, 2-methoxyethyl, 3-methoxy-n-propyl, 2,3-ethylenedioxypropyl, 2,3-(2,2-propylene)dioxypropyl, 2-chloro- or 2-bromoethyl, 2- or 3-chloro-n-propyl or 2- or 3-bromo-n-propyl, or a carbohydrate radical of 5 to 12 carbon atoms, or, if R 1 and R 2 are hydrogen or hydroxy and R 3 is hydrogen, is a steroid radical, and an additional phospholipid of the formula A, wherein each of R 1 and R 2 independently of the other are alkyl, alkenyl, alkoxy or alkenyloxy, each of 10-20 carbon atoms, or is acyloxy of 10-50 carbon atoms, R 3 is hydrogen or C 1 -C 4 -alkyl and R 4 is C 1 -C 7 -alkyl, carboxy-lower alkyl, 2-aminoethyl, 3-amino-n-propyl, 2-methylaminoethyl, 3-methylamino-n-propyl, 2-dimethylaminoethyl, 3-dimethylamino-n-propyl, 2-amino-2-carboxyethyl, 3-amino-3-carboxy-n-propyl, 2-trimethylammonioethyl, 2-triethylammonioethyl, 3-trimethylammonio-n-propyl, 3-triethylammonio-n-propyl, 2-hydroxyethyl, 2,3-dihydroxypropyl, 2-methoxyethyl, 3-methoxy-n-propyl, 2,3-ethylenedioxypropyl, 2,3-(2,2-propylene)dioxypropyl, 2-chloro- or 2-bromoethyl, 2- or 3-chloro-n-propyl or 2- or 3-bromo-n-propyl, or a carbohydrate radical of 5 to 12 carbon atoms; or of a phospholipid of the formula A, wherein m is zero or one, each of R 1 and R 2 independently of the other is alkyl, alkenyl, alkoxy, or alkenyloxy, each of 10-20 carbon atoms, or is acyloxy of 10 to 50 carbon atoms, and R 3 and R 4 are hydrogen and optionally an additional phospholipid of the formula A wherein m is zero or one, each of R 1 and R 2 independently of the other is alkyl, alkenyl, alkoxy, or alkenyloxy, each of 10-20 carbon atoms, or is acyloxy of 10 to 50 carbon atoms, and R 3 is hydrogen or C 1 -C 4 -alkyl, and R.sub. 4 is C 1 -C 7 -alkyl, carboxy-lower alkyl, 2-aminoethyl, 3-amino-n-propyl, 2-methylaminoethyl, 3-methylamino-n-propyl, 2-dimethylaminoethyl, 3-dimethylamino-n-propyl, 2-amino-2-carboxyethyl, 3-amino-3-carboxy-n-propyl, 2-trimethylammonioethyl, 2-triethylammonioethyl, 3-trimethylammonio-n-propyl, 3-triethylammonio-n-propyl, 2-hydroxyethyl, 2,3-dihydroxypropyl, 2-methoxyethyl, 3-methoxy-n-propyl, 2,3-ethylenedioxypropyl, 2,3-(2,2-propylene)dioxypropyl, 2-chloro- or 2-bromoethyl, 2- or 3-chloro-n-propyl or 2- or 3-bromo-n-propyl, or a carbohydrate radical of 5 to 12 carbon atoms in an aqueous phase which is raised to a pH-value at least 11 or (b) a homogeneous layer of a phospholipid of the formula A wherein m is 0 or 1, one of R 1 and R 2 is hydrogen, hydroxy or C 1 -C 4 -alkyl, and the other is alkyl, alkenyl, alkoxy or alkenyloxy, each of 10 to 20 carbon atoms, or is acyloxy of 10 to 50 carbon atoms, R 3 is hydrogen, and R 4 is lower alkyl which is substituted by an ammonio group and an additional phospholipid of the formula A wherein each of R 1 and R 2 independently of the other are alkyl, alkenyl, alkoxy or alkenyloxy, each of 10-20 carbon atoms, or is acyloxy of 10-50 carbon atoms, R 3 is hydrogen or C 1 -C 4 -alkyl and R 4 is C 1 -C 7 -alkyl, carboxy-lower alkyl, 2-aminoethyl, 3-amino-n-propyl, 2-methylaminoethyl, 3-methylamino-n-propyl 2-dimethylaminoethyl, 3-dimethylamino-n-propyl, 2-amino-2- carboxyethyl, 3-amino-3-carboxy-n-propyl, 2-trimethylammonioethyl, 2-triethylammonioethyl, 3-trimethylammonio-n-propyl, 3-triethylammonio-n-propyl, 2-hydroxyethyl, 2,3-dihydroxypropyl, 2methoxyethyl, 3-methoxy-n-propyl, 2,3-ethylene- dioxypropyl, 2,3-(2,2-propylene) dioxypropyl, 2-chloro- or 2-bromoethyl, 2- or 3-chloro-n-propyl or 2- or 3-bromo-n-propyl, or a carbohydrate radical of 5 to 12 carbon atoms; or of a phospholipid of the formula A, wherein m is 0 or 1, each of R 1 and R 2 independently of the other is alkyl, alkenyl or alkenyloxy, each of 10 to 20 carbon atoms, or is acyloxy of 10 to 50 carbon atoms, R 3 is hydrogen, and R 4 is lower alkyl which is substituted by an ammonio-lower alkylammonio group and an additional phospholipid of the formula A wherein each of R 1 and R 2 independently of the other are alkyl, alkenyl, alkoxy or alkenoxy, each of 10-20 carbon atoms, or is acyloxy of 10-50 carbon atoms, R 3 is hydrogen or C 1 -C 4 -alkyl and R 4 is C 1 -C 7 -alkyl, carboxy-lower alkyl, 2-aminoethyl, 3-amino-n-propyl, 2-methylaminoethyl, 3-methylamino-n-propyl, 2-dimethylaminoethyl, 3-dimethylamino-n-propyl, 2-amino-2-carboxyethyl, 3-amino-3-carboxy-n-propyl, 2-trimethylammonioethyl, 2-triethylammonioethyl, 3-trimethylammonio-n-propyl, 3-triethylammonio-n-propyl, 2-hydroxyethyl, 2,3-dihydroxypropyl, 2-methoxyethyl, 3-methoxy-n-propyl, 2,3-ethylenedioxypropyl, 2,3-(2,2-propylene)dioxypropyl, 2-chloro- or 2-bromoethyl, 2- or 3-chloro-n-propyl or 2- or 3-bromo-n-propyhl, or a carbohydrate radical of 5 to 12 carbon atoms, in an aqueous phase which is lowered to a pH-value of about or less than about 1 and the aqueous phase is neutralized with a physiologically acceptable acid or base and the unilamellar liposomes obtained are separated from multilamellar liposomes.