A syringe includes a cartridge and a second chamber. The cartridge includes a first chamber, a second end, and a locking mechanism. The second end is movable within the first chamber between a first position and a second position. The locking mechanism has a locked configuration and an unlocked configuration and prevents movement of the second end within the first chamber while in the locked configuration. The locking mechanism includes: a flexible arm having a first end coupled to the second end of the cartridge and a second free end; a tab coupled to the second free end; and a groove in the inner surface of the chamber configured to receive the tab. The cartridge is moveable within the second chamber.