Redox- and pH-responsive cysteamine-modified poly(aspartic acid) showing a reversible sol-gel transition.

Synthesis and characterization of a pH- and redox-sensitive hydrogel of poly(aspartic acid) are reported. Reversible gelation and dissolution are achieved both in dimethylformamide and in aqueous medium via a thiol-disulphide interconversion in the side chain of the polymers. Structural changes are confirmed by Raman microscopy and rheological measurements. Injectable aqueous solutions of thiolated poly(aspartic acid) can be converted into mechanically stable gels by oxidation, which can be useful for drug encapsulation and targeted delivery. Reduction-facilitated release of an entrapped drug from disulphide cross-linked hydrogels is studied.