Ultradense Synthetic Gene Brushes on a Chip

Dense brushes of linear DNA polymers are assembled on a biochip with approximately 30 nm between anchorage points, amounting to a few mega-base-pairs/microm(3). In bulk solution, a barrier incurs to conjugate more than two end-functionalized DNAs. However, such doublets bind the surface with almost equal efficiency to singlets, suggesting that extended brush buildup reduces the barrier. On-chip transcription reveals that doublets are roughly 2-fold inefficient compared to singlets, a manifestation of the interaction of the enzymatic machinery with the dense brush. Synthetic gene brushes made of DNA conjugates provide simple means to regulate expression on a chip.