Communication overWireless Nanosensor Networks (WNSNs) is envisioned to experience different challenges due to having unique features such as specialized nano-antenna behavior, short transmission range, limited operating capabilities, etc. Among all these features, nano-antenna behavior plays a noteworthy role on overall network-level performance. To the best of our knowledge, the role is yet to be investigated in the literature from the perspective of directional nano-antenna. Therefore, in this paper, we present a model of directional nano-antenna and analyze behavior of the nano-antenna through simulation conducted by CST microwave studio. Furthermore, using directional nano-antennas, we propose a new propagation loss aware routing protocol for WNSNs with a view to ensuring minimum path loss along with a delicate balance among different network-level performance metrics such as throughput, end-toend delay, and energy consumption. In addition, to evaluate the performance of our proposed protocol and compare that against the performances of existing alternatives, we incorporate the nano-antenna model and our proposed protocol in ns-2 simulator after performing necessary customizations in the simulator. We perform rigorous simulation in ns-2 and confirm efficacy of our proposed protocol through the simulation results.