Method For Selecting Desired Level Of Dye Loading And Controlling Loading Of Polymer Microparticles

Abstract

Solute-loaded polymer microparticles are obtained by immersing microparticles in a bath comprising a selected solute dissolved in a ternary solvent system. A first solvent of the ternary system is a strong solvent for both the solute and the polymer from which the microparticle was formed. A second solvent is a weak solvent or non-solvent for the solute and the polymer (tuning solvent). A third solvent is a weak solvent or non-solvent for the solute and polymer, but serves as a co-solvent with respect to the first and second solvents in that it is miscible with both the first and second solvents. The amount of solute incorporated into the microparticles is controlled by adjusting the ratio of solute with respect to the microparticle polymer, and by adjusting the composition of the ternary solvent system, principally the amount of tuning solvent. The method is particularly useful for providing libraries of combinatorially encoded microparticles containing distinguishable dye loadings, particularly distinguishable fluorescent dye loadings.

1 . A method for modulating the solute loading of polymer microparticles comprising:
 (a) providing:
 (i) at least one first solvent in which the solute and the microparticle polymer are soluble; 
 (ii) at least one second solvent in which the solute 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 solute and the microparticle polymer are not or only weakly soluble, said third solvent being miscible with the first and second solvents; 
   (b) forming a suspension of said 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 solution comprising a solute dissolved in said first solvent whereby the solute is taken up by the microparticles to provide a suspension of microparticles characterized by a desired concentration of said solute in the microparticles;   (d) changing the concentration of said solute in at least a portion of the microparticles to a selected second solute concentration by adding to the microparticle suspension or fraction thereof a selected amount of the solute, a selected amount of at least one second solvent, or combination of solute and second solvent, whereby less than complete partitioning of the solute from the suspension liquid phase to the microparticles takes place.   
     
     
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