Immobilization of binding agents

A method of preparing an array of at least one binding agent on a solid support surface, which method comprises the steps of:

• (1) providing a solid support having a surface area bearing a functional group, which surface area is hydrophilic having a contact angle with water of less than about 25 degrees,
• (2) reacting the functional group on the solid support surface area with an activating agent to form a reactive group capable of coupling the binding agent or agents, wherein the activating agent is selected to form a reactive group which is sufficiently less polar than the functional group to make the activated solid support hydrophobic having a contact angle with water of at least about 40 degrees,
• (3) selectively dispensing at each of a plurality of predefined discrete regions on the activated solid support surface area a predetermined volume of an aqueous liquid medium containing binding agent to couple the binding agent to the solid support surface area via the reactive group, the hydrophobic state of the activated surface area substantially preventing extension and spreading of the aqueous liquid medium when applied thereto, and
• (4) deactivating unreacted reactive groups on the solid support surface area to more polar groups to make the solid support surface area hydrophilic having a contact angle with water of less than about 25 degrees.