Thermally reversible polyurethane hydrogels and cosmetic, biological and medical uses

Claim 1

A thermally reversible hydrogel, comprising water and a gel forming hydrophilic polyurethane polymer, produced by reacting under anhydrous conditions an alkylene diisocyanate, bicycloalkane diisocyanate in which the rings are connected via ring carbon atoms by a single bond, or dicycloalkylalkane diisocyanate in which the rings are connected via ring carbon atoms through an alkylene chain, with a glycol component comprising one or more polyoxyethylene glycols, optionally mixed with one or more lower molecular weight ethylene glycols, in a mole weight ratio of NCO/OH of from about 0.900/1 to about 0.980/1, the total glycol component having a number average molecular weight of from about 1000 to about 3500 and wherein the amount by weight of the diisocyanate in the anhydrous reaction mixture is from about 7% to about 20%, mixing the reaction product in an aqueous medium, heating the mixture with stirring until homogeneous, and cooling the mixture.

Claim 22

A method of delivering an active agent to a treatment zone comprising the steps of: (1) mixing the active agent with a thermally reversible hydrogel in its liquid state, the said hydrogel comprising water and a hydrophilic polyurethane polymer produced by reacting under anhydrous conditions, an alkylene diisocyanate, bicycloalkane diisocyanate in which the rings are connected via ring carbon atoms by a single bond, or dicycloalkylalkane diisocyanate in which the rings are connected via ring carbon atoms through an alkylene chain, with a glycol component comprising one or more polyoxyethylene glycols, optionally mixed with one or more lower molecular weight ethylene glycols, in a mole weight NCO/OH ratio of from about 0.900/1 to about 0.980/1, the total glycol component having a number average molecular weight of from about 1000 to 3500 and the percentage by weight of the diisocyanate in the anhydrous reaction mixture is from about 10% to about 15%, mixing the reaction product in an aqueous medium, heating the mixture with stirring until homogeneous, (2) lowering the temperature of the liquid hydrogel to convert it into the solid gel form with concomitant encapsulation therein of the active agent; (3) introducing the solid hydrogel containing the encapsulated active agent to the treatment zone; and (4) raising the temperature of the solid hydrogel to convert it to the liquid form, thereby freeing the active agent to exert its therapeutic effect at the treatment zone.

Claim 23

A method of delivering an active agent to a treatment zone comprising the steps of: (1) mixing the active agent with a thermally reversible hydrogel in its liquid state, the said hydrogel comprising water and a hydrophilic polyurethane polymer produced by reacting under anhydrous conditions, an alkylene diisocyanate, bicycloalkane diisocyanate in which the rings are connected via ring carbon atoms by a single bond, or dicycloalkylalkane diisocyanate in which the rings are connected via ring carbon atoms through an alkylene chain, with a glycol component comprising one or more polyoxyethylene glycols, optionally mixed with one or more lower molecular weight ethylene glycols, in a mole weight NCO/OH ratio of from about 0.900/1 to about 0.980/1, the total glycol component having a number average molecular weight of from about 1000 to 3500 and the percentage by weight of the diisocyanate in the anhydrous reaction mixture is from about 10% to about 15%, mixing the reaction product in an aqueous medium, heating the mixture with stirring until homogeneous, (2) lowering the temperature of the liquid hydrogel to convert it into the solid gel form with concomitant encapsulation therein of the active agent; (3) introducing the solid hydrogel containing the encapsulated active agent to the treatment zone; and (4) raising the temperature of the solid hydrogel to convert it to the liquid form, thereby freeing the active agent to exert its therapeutic effect at the treatment zone.