关键词: 药物载体, 聚集体, 氢键, 离子调控

In this paper, an amphiphilic copolymer poly(2,2'-(1,10-diaza-[18]crown-6-1,10-diyl)diethyl 5-((adenin-9-yl)- methyl)isophthalate) (PDCAI) was designed and synthesized by simulating the chemical structure of DNA. We observed its self-organized morphology in the aqueous solution and in potassium solution with scanning electron microscopy (SEM), amphiphilic copolymer PDCAI spontaneously aggregated into strip aggregates in aqueous solution, and which could change into a rod, nanotube or helical rod aggregates in KNO₃ solution. In addition, the molecular recognition between copolymer PDCAI and thymine substrate has been studied via FT-IR, and it is found that C₂=O of thymine had recognized with PDCAI through complementary nucleobases in aqueous solution, the C₂=O stretching band of thymine at 1737 cm^-1 shifted to 1710 cm^-1 after recognition, however, the band of the C₄=O of thymine did not change at 1677 cm^-1. Meanwhile we attempted to regulate the molecular recognition of copolymer PDCAI with thymine substrate with K⁺, we surprisingly found that hydrogen bonding occurs on C₄=O of thymine when it recognized with PDCAI in KNO₃ solution, the C₄=O stretching band of thymine at 1677 cm^-1 shifted to 1671 cm^-1, however, the band of the C₂=O of thymine did not change at 1737 cm^-1 after recognition. It proves that the recognizing conformation of thymine re-organized during identification process due to the transition of aggregation form of PDCAI. And we further confirmed and studied the hydrogen bond formation and fracture process by variable temperature FT-IR, which formed at room temperature gradually broke while temperature rising from 25℃ up to 115℃, when temperature was above 115℃, hydrogen bonds broke completely, thymine and PDCAI return to their pre-recognition state. The formations of hydrogen bonds between adenine in the polymer and thymine substrate in nanospheres could enhance their interaction and loading capacity. The results have reference value for research of molecular characteristics of polymer which spontaneously formed spiral, preparation of helical polymer, and nucleic acid imitation drug carriers and its function regulation.

Key words: drug carriers, aggregates, hydrogen bond, ion regulation