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to efficiently expand cells and develop robust cell-based models for in vitro drug screening, in vivo-like cell culture conditions — such as dynamic perfusion and 3d growth — are required. here, we show results on a study in which we cultured CompoZr® Zinc finger nuclease-modified U2oS osteosarcoma cells under 3d perfusion cell culture conditions. CompoZr Zinc finger nuclease (Zfn) technology was used to insert the gene encoding red fluorescent protein (RfP) into U2oS’s genome to report the presence of β-actin (U2oS RfPACtB). these cells regularly show an epithelial-like morphology when grown on 2-dimensional (2d) tissue culture plates. however, U2oS RfP-ACtB cells maintained in 3d perfusion bioreactor cell culture conditions showed different cell morphology, enhanced β-actin-RfP expression, cell proliferation, and collagen deposition when compared to U2oS RfP-ACtB growing in 3d static cell culture conditions. therefore, the 3d perfusion bioreactor is a better platform for in vitro cell culture and cell-based models. Introduction Current cell-based assays for drug screening are mostly based on oversimplified cell culture platforms. for instance, both standardized cell lines and primary cells are grown in 2d dishes under static conditions, creating a simplified cellular model without the complexity of target organs or tissue1. A recent study that compared a 3d in vitro model, a mouse model, and a traditional 2d model showed the 3d model has a better genotypic correlation to spontaneous tumor formation found in vivo2. Besides 3d cell culture conditions, perfusion is another factor of interest for drug screening models3. 3d static growth is sometimes not good enough because static cultures deliver suboptimal nutrition/waste exchange conditions that may limit cell growth. there is, therefore, a need to develop a 3d dynamic perfusion cell-based platform for growing optimal cell cultures. Carlos E. Caicedo-Carvajal, Ph.D. Qing Liu, Ph.D. 3D Biotek, LLC. Technology Center of New Jersey, North Brunswick, New Jersey Qing Liu, Ph.D., is an expert in biomaterials, tissue engineering, and in vitro tissue model for drug screening. Carlos E. Caicedo-Carvajal, Ph.D., has worked in several areas of Biomedical Engineering, including 3D tissue organization and engineering of 3D in vitro models for tissue regeneration and drug screening. A Novel 3D perfusion Bioreactor may 2012 sigma.com/biowire 25