Mesoporous
silica nano-channel (MCM-41) based molecular switching of a biologically important anticancer
drug, namely,
ellipticine (EPT) has been utilized to probe its efficient loading onto
MCM-41, and its subsequent release to intra-cellular biomolecules, like
DNA. By exploiting various spectroscopic techniques (like, steady state fluorescence, time-resolved fluorescence and circular dichroism), it has been shown that EPT can be easily translocated from
MCM-41 to
DNA without using any external stimulant. Blue emission of EPT in a polar aprotic
solvent, i.e.,
dichloromethane (DCM), completely switches to green upon loading inside
MCM-41 due to the conversion from a neutral to a protonated form of the
drug inside nano-pores.
Powder X-ray diffraction (PXRD), N2 gas adsorption and confocal fluorescence microscopy results confirm the adsorption of EPT inside the nano-pores of
MCM-41. Here, the
lysozyme (Lyz)
protein has been utilized as a pore blocker of
MCM-41 in order to prevent premature drug release. Interestingly, EPT is released to
DNA even from the EPT-MCM-Lyz composite system, and results in intensification of green fluorescence. Electron microscopy results reveal the formation of a distinctive garland kind of morphology involving
MCM-41 and
DNA probably through non-covalent interactions, and this is believed to be responsible for the
DNA assisted release of
drug molecules from
silica nano-pores. Confocal
laser scanning microscopy (CLSM) imaging revealed that EPT-MCM is successfully internalized into the HeLa
cervical cancer cells and localized into the nucleus. Cell viability assay results infer that EPT-MCM and EPT-MCM-Lyz showed much improved efficacy in HeLa
cancer cells compared to free
ellipticine.