Hybrid mesoporous silica-based nanocarriers for responsive drug release in cancerous cell line

In this work, the synthesis of organic-inorganic hybrids based on pH-responsive, poly(acrylic acid) (PAA) and thermoresponsive, poly(N-isopropyl acrylamide) (PNIPAM), grafted from RAFT agent-primed mesoporous silica nanoparticles (MSNs), has been studied. The confirmation of polymer grafting was obtained through several techniques, for example, FTIR spectroscopy, NMR spectroscopy, etc. The presence of C-H stretching vibrations from FTIR confirmed the presence of organic network in the inorganic MSNs. Further support appeared as notable resonances in C-13 solid-state NMR. The resonance at 175 ppm from C=O group for PAA-grafted MSNs, and at 170-172 ppm from C=O group for PNIPAM-grafted MSNs confirmed the grafting of polymer from the RAFT agent-primed MSNs. Morphological analysis for PAA- and PNIPAM-grafted MSNs was performed using FESEM and TEM. The images manifested spherical shape for isobutyric acid group, and short rod shape for phenyl ethyl group-containing RAFT agent-primed MSNs. Subsequently, for assessing their effectiveness as drug delivery vehicle, the anti-cancerous drug doxorubicin hydrochloride (Dox) was loaded into the MSNs. An effective loading in the range of 50-55% in case of PAA-grafted and 49-61% in case of PNIPAM-grafted MSNs (at pH 7.4, 25 degrees C) was observed. Subsequently release efficiencies for these Dox-encapsulated MSNs were studied at varying pH, temperature and time. The treatment of cultured MCF-7 cell lines by the control MSNs and polymer-grafted MSNs revealed that they are non-toxic. However, when the MSNs were Dox-loaded, the PAA-grafted ones demonstrated higher cytotoxicity than the PNIPAM-grafted MSNs at equivalent dose at pH 7.4 and 37 degrees C. Together with other established features, we show that the polymer-grafted MSNs studied in this work can be utilized as an efficient drug delivery system for different therapeutic applications.