Recent development in near infrared light-responsive polymeric materials for smart drug-delivery systems

Stimuli-responsive drug delivery systems (DDS) may overcome the drawbacks of conventional chemotherapy for cancer treatment. In particular, light-responsive polymer-based DDS may ensure spatio and temporal control in drug delivery. In this regard, near infrared (NIR) light triggered drug nanocarriers present several advantages when compared to UV–visible light triggered nanocarriers. This review surveys the recent development on the design, synthesis, functions, and applications of NIR photo-sensitive compounds in the development of long-wavelength light-responsive nanocarriers. Diverse NIR light responsive groups such as coumarin (CM), ortho-nitrobenzyl (ONB), 2-diazo-1,2-naphthoquinone (DNQ) and spiropyran (SP) derivatives and their photo-cleavage reaction mechanisms are discussed, as well as the use of indocyanine green (ICG) and its photo-thermal application. The loading into polymeric nanocarriers of up converting nanoparticles (UCNPs) which can convert NIR light into UV or visible light is also discussed. The described DDS are classified on the basis on the photo responsive groups. In details, the behavior of different polymeric materials such as micelles, hydrogels bearing photo responsive groups linked to bioactive molecules which are released under NIR light irradiation is reviewed and discussed. A section relative to commonly used instrument setup for drug release studies by NIR light irradiation is also presented for better understanding how the light has been used to irradiate in various experimental situations.