A delivery system is described that includes a polymer network that can incorporate a therapeutic peptide for targeted delivery to a cell, e.g., a cancer cell. The polymer network can secure the therapeutic peptide via two different mechanisms. First, a polymer of the network can interact with the therapeutic peptide via charge/charge interaction to form a complex with the peptide, thereby holding the peptide within the network. Second, the polymer network can be crosslinked, providing another level of securement for holding the therapeutic peptide within the network. The two levels of securement can be reversible, and following delivery of the network to the interior of a targeted cell reversal of the securement mechanisms can release the therapeutic peptide within the cell.
