Preparation of responsive "dual-lock" nanoparticles and their application in collaborative therapy based on CuS...

It is difficult for drug delivery systems to release drugs as expected, often leading to undesired side effects. To solve this problem, a CuS@MSN/DOX@MnO₂@membrane (CMDMm) was reasonably designed. It was introduced to release the drug by a double response, similar to using two keys to open two locks at the same time for one door. CuS@MSN was used as a photothermal therapy (PTT) material and carrier, and then the surface of CuS@MSN/DOX was sealed by MnO₂ to prevent drug release in advance. MnO₂ could be reduced and degraded in a tumor microenvironment. It was applied in MR imaging due to the T₁ magnetism of Mn²⁺ following the reduction of MnO₂. Finally, the 4T1 cell membrane was extracted and coated onto the surface of CuS@MSN/DOX@MnO₂, which served as a target for 4T1 tumor cells. A noteworthy phenomenon was that the fluorescence of DOX was quenched by the coordination between DOX and CuS, and this greatly improved the interaction between DOX and CuS@MSN. However, the coordination was weakened when DOX was protonated in a tumor microenvironment (∼pH 5.0), leading to the release of DOX and fluorescence recovery. The drug release experiments showed that the release efficiency was higher at pH 5.0 with 10 mmol L^-1 GSH. Through in vitro laser confocal imaging, it was successfully observed that DOX was reliably released in specific tumor cells according to the fluorescence recovery, and that there was no leakage in other cells. In short, effective double response drug release was successfully confirmed.