@ Sunita,

Washing is just a process for removing anything that is extra, if you are coating PLL for tissue culture I would recommend to wash with DPBS instead of DI water. At some places we use water to kill the cells, through osmotic shock.

OK thank you so much

Excess soluble PLL may be toxic to your cells. Rinsing the plates with sterile water or PBS will remove soluble PLL and not greatly affect the PLL that is bound to the substratum