Schiff's base as a stimuli-responsive linker in polymer chemistry

Abstract

Schiff-base reactions are widely used in the field of chemistry. With many advantages, such as mild reaction conditions and high reaction rates, they were employed for protecting various functional groups and synthesizing a series of organic ligands. In polymer chemistry, they can serve as potential pH-responsive linkers in polymer chains because of their sensitive responses to changes in the pH value. With certain particular designs, the Schiff-base structure can cooperate with other reversible covalent bonds or supra-molecular interactions to form assemblies or gels, providing various functions and applications. This article aims to give a critical review of the recent literature on the Schiff-base reactions used in polymer chemistry and how they serve as a way of linking structures together. We will also cover some of the important developments on the functions and applications of these polymers.

Injectable polymeric hydrogels for the delivery of therapeutic agents: A review

“…Schiff's base reactions can occur without any chemicals or catalysts under physiological conditions and thus have attracted considerable interest for the fabrication of injectable in situ-forming hydrogels. Another advantageous characteristic of Schiff's base reactions is a controllable reaction rate with respect to the pH of the medium environment [43]. However, aldehyde-containing molecules can affect bioactive factors or tissue extracellular matrix molecules by reacting with amine groups.…”

Galactosylated pullulan–curcumin conjugate micelles for site specific anticancer activity to hepatocarcinoma cells

“…The faster release of curcumin at acidic pH is attributed to the easy breakage of ester linkages at this pH. In addition to that, the Schiff's base formed between LANH 2 and Pu Ald is sensitive to acidic pH [42] leading to the fastest release among the conditions studied. It can also be seen that at both pH, compared to the release pattern of Pu-Cur SA, LANH 2 -Pu Ald-Cur SA shows higher curcumin release.…”

pH‐ and β‐cyclodextrin‐responsive micelles based on polyaspartamide derivatives as drug carrier

“…[10][11][12] The imine linkage is relatively stable in neutral and alkaline environment, although higher acidity destroys it, which can serve as potential pH-responsive linkers in polymer. 13,14 Zhu and coworkers 15 prepared a conjugate containing benzoic imine linkage between the doxorubicin (Dox) moiety and polymeric backbone which is broken when pH is reduced to 5.8, leading to the rapid release of Dox. Jackson and Fulton synthesized core crosslinked star polymers possessing aldehyde or amine functions through reversible imine bond formation.…”