Nu 4750 incubator

HeLa cells (ATCC, USA) and MCF-7 cells (ATCC, USA) were grown in DMEM (Gibco, Life Technologies, MA, USA) with culture media containing 10% fetal bovine serum (Gibco, USA) and penicillin–streptomycin (Gibco, USA). Cells were cultured in a Nu-4750 incubator (NuAire, USA) at 37 °C with a CO₂ level of 5%. The concentrations of silica nanoparticles or exosome-encapsulated silica nanoparticles for HeLa cell intake experiments were 10 µg/mL in a culture medium for 6 h. After changing the culture medium to discard free nanoparticles, a fluorescent cell imager (Bio-Rad, USA) was used, capturing the silica distribution within the cell. For drug delivery experiments, exosome-encapsulated silica nanoparticles loaded with doxorubicin and free doxorubicin were added to the culture medium to a final doxorubicin concentration of 2.5 µg/mL. MTT cell viability assays (Thermo Fisher, USA) and fluorescence microscopy were used to analyze the viability of HeLa and MCF-7 cells and intracellular doxorubicin fluorescence 3, 6, 12, and 24 h after culturing. A confocal microscope (Zeiss, Germany) was used to record the doxorubicin and silica nanoparticle fluorescence distribution 6 h after culture, including lysosome staining by LysoTracker Green (Thermo Fisher, USA) during this period.