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Photophysics and proton transfer dynamics of an eminent anticancer drug, ellipticine (EPT), have been investigated inside a biocompatible octyl-β-D-glucoside (OBG) micellar medium using steady state and time-resolved fluorescence spectroscopic techniques. EPT exists as protonated form in aqueous solution of pH 7. When EPT molecules are encapsulated in OBG micelles, protonated form is converted to neutral form in the ground state due to the hydrophobic effect of the micellar environment. Interestingly, steady state fluorescence results indicate the existence of both neutral and protonated forms of EPT in the excited state, even though neutral molecules are selectively excited, and it is attributed to the conversion of neutral to protonated form of EPT by the excited state proton transfer (ESPT) process. A clear isoemissive point in the time-resolved area normalized emission spectra (TRANES) further supports the excited state conversion of neutral to protonated form of EPT. Notably, this kind of proton transfer dynamics is not observed in other conventional micelles, such as, SDS, Triton-X and CTAB. Therefore, the observed ESPT dynamics is believed to be an outcome of combined effects of the local dielectric constant felt by EPT and the local proton concentration at the OBG micellar surface.

Graphene oxide based molecular switching of ellipticine (E) has been utilized to probe its efficient loading onto graphene oxide (GO) and subsequent release to intra-cellular biomolecules like DNA/RNA. The green fluorescence of E switches to blue in GO and switches back to green with polynucleotides. The intensified blue emission of the ellipticine-GO (E-GO) complex with human serum albumin (HSA), switches to a bluish green upon addition of dsDNA. Electron microscopy reveals the formation of distinctive 3D assemblies involving GO and biomolecule(s) probably through non-covalent interactions and this is primarily responsible for the biomolcule(s) assisted fluorescence-switching of E. To our knowledge, such morphological patterning of a GO-DNA complex is very unusual, reported here the first time and could find applications in the fabrication of biomedical devices. Moreover, our approach of direct optical detection of drug loading and releasing is very cheap, appealing and will be useful for clinical trial experiments once the cytotoxicity of GO is duly taken care.

A visible fluorescence switch of an eminent anti-carcinogen, ellipticine has been used to probe non-specific protein-DNA interaction. The unique pattern of protein-DNA complexation is depicted for the first time through field emission scanning electron microscopy (FE-SEM) images and spectroscopic techniques.

Host-guest interactions between an anticancer drug, ellipticine (EPT), and molecular containers (cucurbitruils (CBn) and cyclodextrins (CD)) are investigated with the help of steady state and time-resolved fluorescence measurements. Our experimental results confirm the formation of 1:1 inclusion complexes with CB7 and CB8. The protonated form of EPT predominantly prevails in the inclusion complexes due to the stabilization achieved through ion-dipole interaction between host and positively charged drug. Drug does not form an inclusion complex with CB6, which is smaller in cavity size compared to either CB7 or CB8. In the case of cyclodextrins, α-CD does not form an inclusion complex, whereas β-CD forms a 1:1 inclusion complex with the protonated form of the drug, and the binding affinity of EPT with β-CD is less compared to CB7/CB8. Interestingly, in the case of γ-CD, drug exists in different forms depending on the concentration of the host. At lower concentration of γ-CD, 1:1 inclusion complex formation takes place and EPT exists in protonated form due to accessibility of water by the drug in the inclusion complex, whereas, at higher concentration, a 2:1 inclusion complex (γ-CD:EPT) is observed, in which EPT is completely buried inside the hydrophobic cavity of the capsule formed by two γ-CD molecules, and we believe the hydrophobic environment inside the capsule stabilizes the neutral form of the drug in the 2:1 inclusion complex. Deep insight into the molecular picture of these host-guest interactions has been provided by the docking studies followed by quantum chemical calculations.