Chemical-gradient directed self-assembly of hydrogel fibers

We demonstrate and investigate how a propagating acidic wave in a solution of dibenzoyl-L-cystine (DBC) can lead to the orientation and alignment of self-assembled fibers constituting a hydrogel. Taking advantage of its pH-induced self-assembly, a hydrogel composed of parallel fibers can be formed by propagating a pH gradient front from one part of a cell to the other. The diffusing species (typically the ion pair H+–Cl−) control the velocity of the pH-gradient front and, therefore, their diffusion rate should match the gelation rate so as to attain complete orientation.