Control of the stepwise self-assembly process of a pH-responsive amphiphilic 4-aminoquinoline-tetraphenylethene conjugate

Controlling the kinetic processes of self-assembly and switching their kinetic properties according to the changes in external environments are crucial concepts in the field of supramolecular polymers in water for biological and biomedical applications. Here we report a new self-assembling amphiphilic 4-aminoquinoline (4-AQ)-tetraphenylethene (TPE) conjugate that exhibits kinetically controllable stepwise self-assembly and has the ability of switching its kinetic nature in response to pH. The self-assembly process of the 4-AQ amphiphile comprises the formation of sphere-like nanoparticles, a transition to short nanofibers, and their growth to long nanofibers with similar to 1 mu m length scale at room temperature (RT). The timescale of the self-assembly process differs according to the pH-responsivity of the 4-AQ moiety in a weakly acidic to neutral pH range. Therefore, after aging for 24 h at RT, the 4-AQ amphiphile forms metastable short nanofibers at pH 5.5, while it forms thermodynamically favored long nanofibers at pH 7.4. Moreover, the modulation of nanofiber growth proceeding spontaneously at RT was achieved by switching the kinetic pathway through changing the pH between 7.4 and 5.5.

Automated summary

In this study, a new amphiphilic 4-aminoquinoline (4-AQ)-tetraphenylethene (TPE) conjugate was reported, which exhibited kinetically controllable stepwise self-assembly and the ability to switch its kinetic nature in response to pH. The self-assembly process of the 4-AQ amphiphile involved the formation of sphere-like nanoparticles, a transition to short nanofibers, and their growth to long nanofibers at room temperature. The time scale of the self-assembly process varied depending on the pH-responsiveness of the 4-AQ moiety.