Fluorescence Active Carbon Nano Spindles Used as a Probe for the Selective Detection of Escherichia coli DNA

The interaction of hydrophilic blue emitting carbon spindles (synthesized from commercially available glucose powder) with various deoxyribonucleic acids (DNA) having different base pair compositions, such as Herring testes... [ view full abstract ]

The interaction of hydrophilic blue emitting carbon spindles (synthesized from commercially available glucose powder) with various deoxyribonucleic acids (DNA) having different base pair compositions, such as Herring testes (HT), calf thymus (CT), Escherichia coli (EC) and Micrococcus lysodeikticus (ML) DNA and also different synthetic DNA, was studied to develop nano materials based sensor devices and to understand the mode of interaction. Interestingly, the fluorescent carbon spindles selectively interacted with E. coli DNA, resulting in remarkable enhanced fluorescence of the former. Interaction of the same carbon with other DNAs exhibited insignificant changes in fluorescence. In addition, in the presence of EC DNA, the D band in the Raman spectrum attributed to the defect state completely disappeared, resulting in enhanced crystallinity. Electron microscopy images confirmed the wrapping of DNA on the carbon spindles leading to the assembly of spindles in the form of flowers. Both carbon and E.coli DNA exhibited negative charge with zeta values of -31.1 mV and -29.0 mV, respectively. The FT-IR spectra indicate the presence of hydrophilic functional groups such as -OH and COO- on the surface of the nanomaterials. Since both the systems have negative surface charge, electrostatic interaction with the phosphate backbone and carbon material cannot be the dominant factor of interaction. Circular dichroism spectra confirm that the carbon spindles are changing the E.coli DNA conformation. Dissociation of double-stranded DNA to single-stranded occurred upon interaction with carbon spindles, resulting in selective E. coli DNA interaction confirm by UV-thermal melting experiment. But in presence of same concentration (even higher) of carbon, the other DNA remains in double stranded conformation. The carbon spindles also exhibited a similar fluorescence enhancement upon treating with live E. coli bacteria and the fluorescence intensity was changes with time and getting saturated after 4 hr. These results confirm the possibility of low cost E. coli detection sensor in water and other liquid foods using such fluorescent carbon materials.