Mixtures of two cationic proteins were used to prepare protein-DNA gel particles, employing associative phase separation and interfacial diffusion (Morán et al., 2009a). By mixing the two proteins, we have obtained particles that displayed higher loading efficiency and loading capacity values than those obtained in single-protein systems. However, nothing is known about the adverse effects on haemocompatibility and cytotoxicity of these protein-DNA gel particles. Here, we examined the interaction of protein-DNA gel particles obtained by two different preparation methods, and their components, with red blood cells and established cells. From a haemolytic point of view, these protein-DNA gel particles were demonstrated to be promising long-term blood-contacting medical devices. Safety evaluation with the established cell lines revealed that, in comparison with proteins in solution, the cytotoxicity was reduced when administered in the protein-DNA systems. In comparison with large-sized particles, the cytotoxic responses of small-sized protein-DNA gel particles showed to be strongly dependent of both the protein composition and the cell line being the tumour cell line HeLa more sensitive to the deleterious effects of the mixed protein-based particles. The observed trends in haemolysis and cell viabilities were in agreement with the degree of complexation values obtained for the protein-DNA gel particles prepared by both preparation methods.