In this paper, we address the problem of Optimal Content Delivery (OCD) in Dynamic Spectrum Access (DSA) networks, where the source of a flow sends data traffic to the destination in exchange for some monetary benefit, such as a subscription fee. Also, each intermediate secondary node incurs a cost for routing traffic. We propose a path auction based content delivery mechanism in which each secondary node announces its cost (considered as private information) to the auction mechanism. Based on the announced costs, the optimal flow rate between the end nodes is determined, a multi-path route is chosen and payments are made to the nodes that route traffic, such that the profit of the source node is maximized in sending data to the destination. Furthermore, the auction mechanism is strategy-proof, i.e., it can induce the intermediate nodes to truthfully declare their costs. We provide polynomial time algorithms for implementing our auction based content delivery mechanism in DSA networks.