This paper proposes a leader-follower based target detection model for mobile molecular communication networks. The proposed model divides application functionalities of molecular communication networks over the two types of mobile bio-nanomachine: leader and follower bio-nanomachines. Leader bio-nanomachines distribute in the environment to detect a target and create an attractant gradient around the target. Follower bio-nanomachines move based on the attractant gradient made by leader bio-nanomachines, approach the target and perform necessary functionalities such as releasing drug molecules. The functional division demonstrated through the model facilitates the design and development of molecular communication networks as it can reduce the number of functionalities that need to be implemented on individual bio-nanomachines.