Smart stimuli-responsive drug carriers (STRDCs) are a hot topic in current chemical and pharmaceutical research, owing to their merits of controlled release of drugs relying on unique stimuli-responsive mechanisms. Well-designed STRDCs could efficiently improve drug bioavailability and reduce side effects in vivo, thus they are of great potential in future clinical treatments. Cyclodextrin (CD)-based drug carriers, which have the ability to control drug delivery in temporal, spatial and dosage in a more precise fashion, have made tremendous progress in recent years. STRDCs could be constructed based on CDs ascribing to their virtues of readily availability, low toxicity, self-assembly and functional flexibility. More and more materials of good biocompatibility are employed to fabricate STRDCs in combination with CDs to furnish unique characteristics of self-assembly, molecular recognition and dynamical reversibility. These STRDCs could administrate drug controlled release upon the regulation of their physico-chemical properties in response to external stimuli, which usually fall into two categories: endogenous (pH, redox agents, enzyme concentration, etc.) and exogenous (temperature, light, magnetic force, ultrasound, voltage stimulation, etc.) ones. In this review, the recent advances on the cyclodextrin-based STRDCs are summarized, which are classified referring to the variations of stimulating factor. The features, mechanism of action and potent applications of STRDCs are discussed. In addition, some personal perspectives on this field are also presented.

Contents
1 Introduction
2 Endogenous stimuli-responsive drug delivery
2.1 pH sensitive systems
2.2 Redox sensitive systems
2.3 Enzyme sensitive systems
3 Exogenous stimuli-responsive drug delivery
3.1 Thermo sensitive systems
3.2 Light sensitive systems
3.3 Magnetically responsive systems
3.4 Ultrasound responsive systems
3.5 Electro responsive systems
4 Conclusion