Multilayer pH-responsive hollow mesoporous silica nanoparticles with charge reversal for drug delivery and real-time monitoring by fluorescence

Drug delivery systems (DDSs) with charge reversal could simultaneously achieve long circulation time and enhanced cellular internalization efficiency. Here, hollow mesoporous silica nanoparticles (HMSNs) were used as the basic stuff for encapsulating doxorubicin (DOX), positive-charged chitosan (CS) was grafted on the surface of HMSNs, and negatively charged carboxyl-rich carbon dots (CDs) were coated on the outer layer of CS through non-covalent bonds. The new drug delivery vehicles with 56.6% drug-loading content were prepared, named as CDs-CS/HMSNs@DOX. Tumor environment with a slightly acidic state could trigger the disruption of the non-covalent bonds, followed by the detachment of CDs, making the negatively charged CDs-CS/HMSNs@DOX change into positively charged CS/HMSNs@DOX. CS swelling reaction also happened in slightly acidic conditions. Both the CS swelling and the detachment of CDs resulted in the exposure of mesopore and drug release. Fluorescence recovery of detached CDs could be used to monitor the release of DOX in real-time. The multilayer pH-responsive nano carries with charge reversal and real-time monitoring demonstrated broad application prospects.