Polymeric macroinitiators for signal amplification in AGET ATRP-based DNA detection

We report here the use of polylysine (PLL) as a carrier to bring multiple polymerization reaction initiators to surface-affixed PNA/DNA duplexes for signal amplification in polymerization-based DNA detection. Two primary benefits of the described approach have been demonstrated in this report: (1) positively charged PLL as the initiator carrier binds to PNA/DNA duplexes electrostatically; thus eliminates the need for chemical modification of each individual DNA probes prior to detection and provides a universal DNA detection scheme. (2) Furthermore, each PLL molecule brings multiple polymerization reaction initiators to each hybridization event, which leads to significantly improved detection sensitivity. Systematic investigation shows the use of longer PLL (∼215 lysine residues per chain) has yielded thicker polymer films in comparison to that of a shorter PLL (∼27 lysine residues per chain). An optimal percentage of lysine moieties modified on each PLL molecule has been determined that allowed maximum polymer growth from each modified lysine group without compromising vital electrostatic binding between unmodified amino groups and negatively charged DNA. Quantitative DNA detection has been demonstrated where the detection limit has been improved for approximately 60 times compared to the previously reported value in single-initiator-tagged DNA detection.