Bioinspired core-shell silica nanoparticles monitoring extra- and intra-cellular drug release.

Förster resonance energy transfer (FRET) has been widely used for monitoring drug release from nanoparticles (NPs). To understand the drug release from bioinspired drug-core silica-shell NPs, we synthesised two types of NPs using the dual-functional peptide SurSi via biosilicification for the first time, i.e., silica NP conjugated with FRET (Cy3 and Cy5) molecules, and FRET-core (DiO and DiI) silica-shell NP with different shell thicknesses (18 and 41 nm). The release kinetics of these two types of NPs were investigated under different conditions, including fetal bovine serum (FBS) and in cells, to mimic the drug release during blood circulation and intracellularly. Two different drug release mechanisms were identified. Cargo diffusion dominated the release during circulation, while the degradation of silica shell played a key role in drug release intracellularly.