Fig. 5

Various advanced MSNs for pH-responsive delivery of drugs. A Methodological comparison between the traditional MSNs-based nano-drug delivery systems by the drug post-loading route and the proposed MSNs by the drug in situ co-loading route. B In-vitro pH-responsive drug release behaviors of DOX@CTAB@MSNs in the release media of different pH values, which were used to simulate the alkalescent conditions in normal tissues and blood (pH ~ 7.4) and the acidic conditions in the tumor (pH = 4–6.8). Reproduced with permission from Ref. [76] Copyright 2011, Elsevier. C TEM images of nanomicelles with (i) and without (ii) PEG segments at different pH values. D Confocal microscopic images of HeLa cells treated by rhodamine B-loaded and FITC-labeled micelles for 4 h at different conditions: (i) pH = 7.4, 37 °C; (ii) pH = 7.4, 39 °C; (iii) pH = 6.4, 37 °C; (iv) pH = 6.4, 39 °C (scale bar: 80 μm). Reproduced with permission from Ref. [253] Copyright 2010, American Chemical Society. E Schematic showing the fabrication of MSNs for tumor-triggered targeting drug delivery. Functionalization protocol of the MSN; drugs loaded under physiological condition; removal of PASP protection layer in response to MMP at a tumor site; cell uptake through RGD-mediated interaction; GSH-triggered drug release inside the cell; and apoptosis of tumor cells. Reproduced with permission from Ref. [254] Copyright 2013, American Chemical Society