Magnetic and pH dual-responsive mesoporous silica nanocomposites for effective and low-toxic photodynamic therapy

Nonspecific targeting, large doses and phototoxicity severely hamper the clinical effect of photodynamic therapy (PDT). In this work, superparamagnetic Fe₃O₄ mesoporous silica nanoparticles grafted by pH-responsive block polymer polyethylene glycol-b-poly(aspartic acid) (PEG-b-PAsp) were fabricated to load the model photosensitizer rose bengal (RB) in the aim of enhancing the efficiency of PDT. Compared to free RB, the nanocomposites (polyethylene glycol-b-polyaspartate-modified rose bengal-loaded magnetic mesoporous silica [RB-MMSNs]) could greatly enhance the cellular uptake due to their effective endocytosis by mouse melanoma B16 cell and exhibited higher induced apoptosis although with little dark toxicity. RB-MMSNs had little dark toxicity and even much could be facilitated by magnetic field in vitro. RB-MMSNs demonstrated 10 times induced apoptosis efficiency than that of free RB at the same RB concentration, both by cell counting kit-8 (CCK-8) result and apoptosis detection. Furthermore, RB-MMSNs-mediated PDT in vivo on tumor-bearing mice showed steady physical targeting of RB-MMSNs to the tumor site; tumor volumes were significantly reduced in the magnetic field with green light irradiation. More importantly, the survival time of tumor-bearing mice treated with RB-MMSNs was much prolonged. Henceforth, polyethylene glycol-b-polyaspartate-modified magnetic mesoporous silica (MMSNs) probably have great potential in clinical cancer photodynamic treatment because of their effective and low-toxic performance as photosensitizers' vesicles.