This requires the synthesis of several DNA-b-PPOs with different molecular weights and different block length ratios of the biological and organic polymer segments. Previously, the DNA-b-PPO was assembled by a grafting onto approach on the solid phase that included coupling of a phosphoramidite PPO to the oDNA that is bound to the solid support as the key step of the synthesis. However, this synthetic protocol cannot directly be translated to the microfluidic system since in the last step harsh deprotecting conditions (conc. ammonia) were required.
Instead we plan to introduce a mild coupling procedure that is compatible with the microfluidic environment. Since attachment of the synthetic polymer to immobilized DNA has proven to work in excellent yields,( Alemdaroglu FE, Ding K, Berger R, Herrmann A, Angew. Chem. Int. Ed. 45: 4206-4210, 2006 ) the oDNA will be bound to the chip surface by hybridization with the complementary oDNA that had been previously immobilized chemically within the microfluidic device. To join both segments, the oDNA as well as the polymer contain complementary end-groups like carboxyl and amine functionalities that can be coupled by addition of mild activating agents like carbodiimides. A similar strategy successfully resulted in amphiphilic DNA-b-polyisoprene.( Teixeira F, Rigler P, Vebert-Nardin C, Chem. Commun. 11: 1130-1132, 2007) Release of the block copolymers will be achieved by dehybridzation e.g. by a shift of the pH. (This is the synthesis of DNA block copolymers in microfluidics)
