A Photon-Fueled Gate-Like Delivery System Using i-Motif DNA Functionalized Mesoporous Silica Nanoparticles

A novel photon-fueled gate-like mesoporous silica nanoparticles (MSN)-based delivery system is reported. In this system, the malachite green carbinol base (MGCB) is immobilized on the nanochannel wall of MSN as a light-induced hydroxide ion emitter and i-motif DNA is grafted on the surface of MSN as a cap. Photoirradiation with 365 nm wavelength UV light makes MGCB molecules dissociate into malachite green (MG) cations and OH- ions, which induce the i-motif DNA to unfold into the single-stranded form due to the increase of the pH in the solution. Therefore, the pores are uncapped and the entrapped guest molecules are released. After the light is turned off, the MG cations recombine with the OH- ions and return to the MGCB forms. The pH value thus decreases and the single-stranded DNA switches back to i-motif structure to cap the pore again. Because of the photon-fueled MGCB-dependent DNA conformation changes, the i-motif DNA-gated switch can be easily operated by turning the light on or off. Importantly, the opening/closing protocol is highly reversible and a partial cargo release can be easily achieved at will. This proof-of-concept may promote the application of DNA in the controlled release and can also provide a way to design various photon-fueled controlled-release systems using a combination of some photoirradiated pH-jump systems and other kinds of pH-sensitive linkers.