pH-Responsive Dual Cargo Delivery from Mesoporous Silica Nanoparticles with a Metal-Latched Nanogate

A nanogate composed of two iminodiacetic acid (IDA) molecules and a metal ion latch was designed, synthesized, and assembled on mesoporous silica nanoparticles. This gating mechanism is capable of storing and releasing metal ions and molecules trapped in the pores. Pore openings derivatized with IDA can be latched shut by forming a bis-IDA chelate complex with a metal ion. This system was tested by loading with Hoechst 33342 as the probe cargo molecule, and latching with cobalt, nickel, or calcium metal ions. No cargo release was observed in a neutral aqueous environment, but both cargoes were delivered after acid stimulation and/or the addition of a competitively binding ligand.