Figure 1.

(a) Scheme showing the control of the probe density, during the synthesis of PLL-OEG-Mal polymers, which provides the targeted probe density and cDNA binding at the substrate upon immobilization of the modified PLL. x and y indicate the percentages of oligo(ethylene glycol) and maleimide grafted to the PLL side chains, respectively. (b) Synthesis of PLL-OEG-Mal. PLL is reacted with desired relative ratios of Mal-OEG₄-NHS (y = 0–9.1%) and methyl-OEG₄-NHS ester (x = 15.9–29.1%) to give the final modified PLL with the desired degrees of functionalization.