Patent ID: 6964747

Claim:
A method of incorporating at least one dye into polymer microparticles comprising: (a) providing: (i) at least one first solvent in which the dye and the microparticle polymer are soluble; (ii) at least one second solvent in which the dye and the microparticle polymer are not or only weakly soluble, said first and second solvents being immiscible or at most partially miscible; (iii) at least one third solvent in which the dye and the microparticle polymer are not or only weakly soluble, said third solvent being miscible with the first and second solvents; (b) suspending the polymer microparticles in a designated volume of a mixture comprising at least one second solvent and at least one third solvent; (c) adding to said polymer microparticle suspension a dye solution comprising at least one first solvent and at least one dye dissolved therein, the amount of dye corresponding to the desired final state of dye incorporation in the microparticles; (d) adding to said polymer microparticle suspension at least one second solvent to induce substantially complete partitioning of the dye from the suspension liquid phase to the microparticles.