Photoresponsive real time monitoring silicon quantum dots for regulated delivery of anticancer drugs.

Recently, photoresponsive nanoparticles have been widely used to develop drug delivery systems (DDSs) wherein light is used as an external stimulus to trigger drug release in a spatially and temporally controlled fashion. Real time monitoring DDSs are also gaining much interest due to their capability of monitoring drug release in situ. In this context we designed a new photoresponsive real time monitoring nanoparticle based on photoluminescent silicon quantum dots (SiQDs) using the o-nitrobenzyl (ONB) derivative as a phototrigger for the controlled release of anticancer drug chlorambucil (Cbl). The strong fluorescence of SiQDs was initially quenched by ONB. Upon irradiation ONB triggered the release of the drug switching on the fluorescence of SiQDs to monitor the drug release. We reported a new and simple strategy to synthesise amine functionalised silicon quantum dots and covalently conjugated phototrigger ONB with caged anticancer drug Cbl onto it. Newly designed photoresponsive theranostic ONBCbl-SiQDs performed three important functions: (i) nanocarriers for drug delivery, (ii) controlled drug release under both one photon and two-photon excitation, and (iii) photoswitchable fluorescent nanoparticles for real-time monitoring of drug release based on the photoinduced electron transfer (PET) process. In vitro biological studies revealed the efficient cellular internalisation and cancer cell destruction ability of ONBCbl-SiQDs upon photoirradiation. ONBCbl-SiQDs exhibit a successful example of combining multiple functions into a single system for drug delivery systems.