Decoding of array sensors with microspheres

A method of decoding the position of bioactive agents attached to microspheres on an array substrate comprising:

• a) providing an array substrate comprising a population of microspheres comprising at least a first and a second subpopulation, wherein the microspheres of each subpopulation comprise:
• i) a bioactive agent;
• ii) at least a first and a second identifier binding ligand (IBL), wherein said first and second IBLs are different from said bioactive agent and wherein said IBLs are attached to said microsphere;
• and
• b) detecting both the first and second IBLs to decode the position of each of said bioactive agents on said substrate.

A method of decoding the position of a bioactive agent on an array substrate comprising:

• a) providing an array substrate comprising randomly distributed microspheres, wherein each microsphere comprises:
• i) a bioactive agent;
• and
• ii) a combination of different identifier binding ligands (IBLs), wherein said combination uniquely identifies said bioactive agent;
• b) adding a first decoder binding ligand (DBL) to the array substrate, wherein the first DBL binds to an IBL in said combination;
• c) identifying the position of the IBL that binds to the first DBL;
• d) adding a second DBL to the array, wherein the second DBL binds to another IBL in said combination;
• e) identifying the position of the IBL that binds to the second DBL;
• and
• f) decoding the position of said bioactive agent on said array substrate based on the position on the array substrate of the IBLs that bind the first and the second DBLs.