ABSTRACT
It would be highly beneficial if microbicides are delivered by a system that can sense the signals or stimuli from the complex physiological environment, act on drug release profiles and then
circumvent mucosal barriers. Since the concept of stimuli responses was introduced for target-specific drug delivery [3], stimuliresponsive formulations have been designed based on both physiological factors and target ligand approaches toward host cells, namely chemical affinity targeting using molecules, such as sugar residue or antibodies, as homing devices, and physical affinity targeting using pH, thermally, or magnetically responsive carriers [4]. Various carrier systems that react to different stimuli, such as pH [5-8], temperature [9-11], enzymes or antigens [12,13], magnetic fields [14-16], near-infrared (NIR) [17-20] and ultra-violet (UV) radiation [21,22], ionic strength [23,24], electrochemical strength [25,26], and ultrasound [27-29], have been explored. These external stimuli may enable a drug carrier to distinguish between physiological and pathological environment and allow for the controlled release of loaded drugs at the target sites. Advanced technology further allows for enhancement of the sensitivity of carriers to the stimuli through modulation of structures or attachment of chemical moieties of a polymeric material [30,31].
