Lyophilization method and apparatus for producing particles

A method for producing particles comprising:

• providing a solution comprising a solvent and a solute;
• providing a supercritical fluid;
• mixing the solution and the supercritical fluid together to form a mixture at a first pressure and temperature that sufficient to maintain the supercritical fluid in a supercritical state;
• providing an expansion chamber maintained at a temperature below the freezing point of the solution;
• flowing the mixture across a pressure drop into the expansion chamber to form frozen droplets that comprise the solute and frozen solvent;
• and
• freeze-drying the frozen droplets to sublime the frozen solvent from the frozen droplets and thereby produce solid solute particles that are substantially free of solvent.

A method for producing particles comprising:

• providing a solution comprising a solvent and a solute;
• providing a first supercritical fluid and a second supercritical fluid, the first supercritical fluid having a higher freezing point than the second supercritical fluid;
• mixing the solution, the first supercritical fluid and the second supercritical fluid together to form a mixture;
• providing an expansion chamber that is maintained at a temperature below the freezing point of the solution;
• flowing the mixture across a pressure drop through a nozzle having a contra-current, co-axial, single or multiple opening configuration into the expansion chamber to form a spray of frozen droplets that comprise the solute and frozen solvent, wherein the first supercritical fluid component operates as a blowing or expanding agent and the second supercritical fluid component operates as a freezing agent;
• and
• freeze-drying the frozen droplets to sublime the frozen solvent from the frozen droplets and thereby produce solid solute particles that are substantially free of solvent.