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.