Gel Microdrop Composition and Method of Using the Same

A method comprising,

• a) combining:
• i. a monomer for a polymer;
• ii. an effector particle that releases an effector molecule;
• iii. a first reporter particle that emits a first optically detectable signal;
• iv. a second reporter particle that emits a second optically detectable signal that is distinguishable from the first optically detectable signal, to produce a particle-containing composition;
• b) making droplets of said particle-containing composition;
• and
• c) polymerizing the monomers;
• to produce a gel microdrop composition comprising:
• a polymer matrix,
• an effector particle that releases an effector molecule into said polymer matrix;
• said first reporter particle;
• and
• said second reporter particle;
• wherein said effector particle and said first and second reporter particles are encapsulated by said polymer matrix and wherein an alteration of said first or second optically detectable signal caused by selective interaction of said candidate effector molecule with one of said first or second reporter particles indicates that said candidate effector molecule is a selective binding agent.