Poly-D-lysine (PDL) coated microtiter and multiwell plates are designed to enhanced cell binding to polystyrene surfaces for certain cell-based assays and procedures. Plastic surfaces that are coated with this synthetic polymer possess a uniform net positive charge. This uniform net positive charge is preferred by certain cell types and can subsequently enhance cell attachment, growth and differentiation of these cell types, especially under serum-free and/or low serum conditions. PDL coated surfaces often improve attachment and growth of primary neurons, glial cells, neuroblastomas, and a variety of transfected cell lines. In addition, PDL coated surfaces are often used to reduce cell detachment that often occurs during multiple washing steps that are associated with cell-based assays.