Ultrafast molecular rotor based DNA sensor: An insight into the mode of interaction

Natural DNA assisted white light generation and stimuli responsive colour tuning

The unique structure of a natural nucleic acid, calf thymus DNA, which can provide an appropriate scaffold for an efficient cascaded energy transfer among organic chromophores, has been used for the generation of bright and pure white light on UV light excitation. Two most commonly used DNA stains, 4',6-diamidino-2-phenylindole (DAPI) and ethidium bromide (EB) have been used as a part of the donor-acceptor pairs. We have judiciously selected 10-anthracene-10-yl-3-methylbenzothiazol-3-ium chloride (AnMBTZ), an ultrafast molecular rotor, to act as a bridge between DNA bound DAPI and EB for the cascaded flow of energy. The unique molecular rotor properties of AnMBTZ and its exceptional binding ability with natural DNA help to form a distinct tri-chromophoric system in DNA template which can produce bright and pure white light on UV excitation. Detailed flow of energy from photoexcited DAPI to EB via AnMBTZ has been explored using steady state and time-resolved emission spectroscopy. Further, unique binding nature of AnMBTZ with DNA molecules has been used to modulate the colour of the emission from the present tri-chromophoric system by external stimuli, like salt and temperature. Such unique stimuli responsive multi-chromophoric system in a bio-template has great potential for different lightening applications.

Effect of DNA Origami Nanostructures on hIAPP Aggregation

The aggregation of human islet amyloid polypeptide (hIAPP) plays a major role in the pathogenesis of type 2 diabetes mellitus (T2DM), and numerous strategies for controlling hIAPP aggregation have been investigated so far. In particular, several organic and inorganic nanoparticles (NPs) have shown the potential to influence the aggregation of hIAPP and other amyloidogenic proteins and peptides. In addition to conventional NPs, DNA nanostructures are receiving more and more attention from the biomedical field. Therefore, in this work, we investigated the effects of two different DNA origami nanostructures on hIAPP aggregation. To this end, we employed in situ turbidity measurements and ex situ atomic force microscopy (AFM). The turbidity measurements revealed a retarding effect of the DNA nanostructures on hIAPP aggregation, while the AFM results showed the co-aggregation of hIAPP with the DNA origami nanostructures into hybrid peptide–DNA aggregates. We assume that this was caused by strong electrostatic interactions between the negatively charged DNA origami nanostructures and the positively charged peptide. Most intriguingly, the influence of the DNA origami nanostructures on hIAPP aggregation differed from that of genomic double-stranded DNA (dsDNA) and appeared to depend on DNA origami superstructure. DNA origami nanostructures may thus represent a novel route for modulating amyloid aggregation in vivo.

Polymer-assisted drug sequestration from plasma protein by a surfactant with curtailed denaturing capacity

The capability of a surfactant to sequester a drug bound to plasma protein was investigated using steady-state and time-resolved spectroscopic techniques. Surfactants are known to denature protein, and hence are not suitable for the sequestration of a drug from protein. Herein, we show that the denaturing capacity of a surfactant is curtailed completely and its drug sequestration power is enhanced in the presence of biocompatible Pluronic micelles due to the formation of unique supramolecular assemblies. Further, our detailed studies indicate that the concentration of surfactant required for the sequestration of a drug is less than its critical micellar concentration (CMC). The extent of sequestration of drug by polymer-surfactant supramolecular assemblies can be tuned finely by controlling the concentration of surfactant. Detailed analysis showed that up to ∼85% sequestration of a drug from plasma protein could be achieved using a sub-CMC concentration of surfactant. Our results clearly show that controlled sequestration of a drug from plasma protein can be achieved with a reduction in the protein denaturing properties of surfactants.