Array compositions and methods of making same

A method for making an array composition containing at least a first assay location having discrete sites comprising the steps of:

• (a) contacting a surface of a template structure, said surface comprising one or more sets of projections, with a moldable material;
• (b) removing said moldable material from said surface of said template structure, whereby said removed moldable material forms a molded layer with at least a first assay location comprising discrete sites, wherein each of said discrete sites is configured to hold a single microsphere;
• (c) applying a layer of adhesive to adhere said molded layer to a rigid support in order to maintain the molded layer in a planar configuration;
• and
• (d) randomly distributing microspheres on said molded layer such that individual discrete sites comprise microspheres, wherein said microspheres comprise at least a first and a second subpopulation, wherein said first subpopulation comprises a first bioactive agent and said second subpopulation comprises a second bioactive agent.

An array composition comprising:

• (a) a molded layer having an upper surface and a planar lower surface, wherein said upper surface comprises a first assay location comprising discrete sites, each of which is configured to hold a single microsphere;
• (b) a rigid support adhered to said planar lower surface and adapted to maintain said molded layer in a planar configuration;
• and
• (c) a population of microspheres comprising at least a first and a second subpopulation, wherein said first subpopulation comprises a first bioactive agent and said second subpopulation comprises a second bioactive agent, and wherein said microspheres are randomly distributed on said sites.