Several needle assemblies and intracellular delivery devices that are used for the delivery of prophylactic and/or therapeutic material (i.e., delivered agents) into a tissue of a subject are disclosed. Preferably, the needle assemblies and/or the intracellular delivery devices comprise needles and/or needle electrodes, which are disposed in an array (e.g., a Y-type array having three outer needles and a center needle), wherein each needle in the array has a closed end and a plurality of apertures along each needle barrel, and the apertures on the needle barrels of the outer needles of the array are positioned to deliver the delivered agent toward the apertures of the center needle and/or an adjacent needle, but not outside of the active zone defined by the area within the needle array and the apertures on the needle barrel of the center needle are positioned to deliver the delivered agent toward the outer needles.