Poly(L-histidine)-Containing Polymer Bioconjugate Hybrid Materials as Stimuli-Responsive Theranostic Systems

For decades, researchers have aspired to develop materials for noninvasive treatment and monitoring of pathological conditions. Various organs, tissues, subcellular compartments, and their pathophysiological states can be characterized by their pH values. pH-dependent intracellular tumor targeting has received particular attention due to the unique acidic environment of the solid tumors created by physiological and metabolical abnormalities. Responsive nanocarriers, when exposed to these pH stimuli, respond quickly to the physicochemical changes by undergoing structural deformations, such as swelling and phase transition, which favors the drug release specifically at the diseased site. Recently, researchers have developed several new poly(L-histidine) (p(His))-based pH responsive systems for sustained drug release and molecular targeting. This review focuses on the p(His)-based pH responsive nanocarriers, which are utilized in biomedical applications such as anti-cancer drug delivery and nucleic acid delivery. (C) 2014 Wiley Periodicals, Inc.