Label-Free and Nondestructive Separation Technique for Isolation of Targeted DNA from DNA-Protein Mixture Using Magnetic Au-Fe3O4 Nanoprobes.

The interest in DNA-protein-based diagnostics has recently been growing enormously, which makes the separation process of DNA or protein from a cell extract extremely important. Unlike the traditional separation process, a novel approach is in demand which can nondestructively isolate the target biomolecules without sacrificing the other components in the mixture. In this study, we have demonstrated a new and simple separation technique by using well-established bifunctional Au-Fe3O4 nanocomposites as the separation nanoprobes to efficiently isolate the specifically targeted nanomolar concentrated DNA over 70% from its associate DNA-protein mixture in the presence of a magnetic field. The sensing accuracy of both as-separated DNA and protein are quantitatively examined by UV-vis spectroscopy, and then qualitatively validated by gel analysis. Results obtained in this study clearly demonstrated that this newly developed separation procedure not only provides the efficient separation for the targeted DNA but can also maintain the bioactivity of as-separated protein and DNA solutions. The superiority of this technique can open an avenue to establish a label-free and nondestructive platform for a wide variety of biomolecule separation applications.

Single-Molecule FRET Studies of the Hybridization Mechanism during Noncovalent Adsorption and Desorption of DNA on Graphene Oxide.

Remarkable observations on the adsorption and desorption mechanisms of single-stranded oligonucleotides and the hybridization of double-stranded DNA (ds-DNA) on a graphene oxide (GO) surface have been made using ensemble and single-molecule fluorescence methods. Probe and target DNAs labeled individually with fluorescence resonance energy transfer (FRET) pairs and having similar adsorption affinities toward the GO surface are used to provide detailed insights into the hybridization mechanism. Single-molecule FRET results reveal an "in situ" DNA hybridization mechanism, i.e., hybridization between the probe and target DNAs to form a ds-DNA, and simultaneous desorption from the GO surface thereafter. These results also demonstrate that the electrostatic interaction between DNA and GO is of little importance to the overall theory of interaction and the largest effects are from solvation forces, specifically the hydrophobic effect. This investigation improves the fundamental understanding of the DNA hybridization dynamics on the GO surface, opening new windows in the field of biophysics as well as in sensing and therapeutic applications.

Non-enzymatic electrochemical detection of cholesterol using ß-cyclodextrin functionalized graphene.

A non-enzymatic approach towards cholesterol detection is presented here, exploiting the electrochemical non-enzymatic route of sensing which has a distinct advantage over other conventional enzymatic processes. Chemically converted Graphene modified with ß-CD, being hydrophilic, electroactive and high surface area material, provides a platform for the electrochemical detection of cholesterol using Methylene Blue as redox indicator. Methylene Blue (MB) forms an inclusion complex with Grp-ß-CD and emerges as a cholesterol sensing matrix. MB molecule is replaced by cholesterol molecule and moves out in the buffer solution, hence, detected electrochemically using Differential Pulse Voltammetric (DPV) technique. The sensing matrix is characterised using FT-IR and Raman spectroscopy. Transmission Electron Microscopy is carried out to study the morphology of functionalized graphene sheets.