Optifect Transfection Reagent is a pre-optimized formulation designed to ensure highly efficient gene delivery to a wide variety of cell lines transfected at low confluence or density (10%-70%) (Figure 1). Optifect Reagent can also be used with cells that are sensitive to Lipofectamine 2000 or other commercially available transfection reagents. Optifect Reagent facilitates high levels of protein expression from sparsely plated cells (Table 1). Useful in applications such as studies of cell surface proteins, post-transfection proliferation assays, or other situations where cells must be allowed to grow significantly following transfection. Optifect has been shown to be less toxic to cells compared to other commercially available transfection reagents.