Stimuli-responsive chitosan as an advantageous platform for efficient delivery of bioactive agents

Despite a diverse range of active pharmaceutical agents currently at our disposal, high morbidity rate diseases continue to pose a major health crisis globally. One of the important parameters in this regard is the controlled cargo delivery at desired sites. Among a variety of synthetic and natural macromolecular systems, chitosan, an abundant biopolymer, offers a platform for tailored architectures that could have high loading capacity of cargo, target and deliver. Stimuli directed accumulation of vehicles and drug release is an area of direct relevance to biomedical applications. In this review, we highlight essential characteristics of modified chitosan that present themselves for efficient response through an internal (glutathione, reactive oxygen species, pH, temperature, enzymes, and chemical/electrical potential gradient), and external stimuli (ultrasound, light, mechanical stimuli, magnetic and electrical fields). With a brief review of the pertinent properties of chitosan that are relevant to biology, the design and critical evaluation of varied chitosan-based platforms is discussed. Future directions in exploiting important features of chitosan in this area can be derived from the presented comparative evaluation of the current literature in drug delivery.