This study was aimed at formulating Paclitaxel (R)-loaded solid lipid nanoparticles (SLN) complexed with Herceptin (R). The physicochemical characterizations of the SLNs/Herceptin (R) complexes such as particle size and shape, zeta potential, drug incorporation efficiency or in vitro PTX and Herceptin (R) release were examined using zeta sizer, scanning electron microscopy and HPLC. The effect of formulation conditions on Herceptin (R) was assessed with SDS-PAGE. Cell culture studies were done via MIT assays in HER2-positive MDA-MB-453, and HER2-negative MDA-MB-231 breast cancer cells. Results showed that particle sizes of complexes were below 200 nm, with a positive zeta potential after addition of cationic agents and Herceptin (R). Paclitaxel (R)-loaded cationic SLN/Herceptin (R) complexes were more toxic to MDA-MB-453 cell line when compared to Paclitaxel (R)-loaded anionic and cationic SLNs. These in vitro results suggest that Paclitaxel (R) and Herceptin (R) could be simultaneously delivered using SLNs as delivery system whilst retaining the functionality of the antibody as targeting moiety. (C) 2016 Elsevier B.V. All rights reserved.