Taehyun Hwang

Chemical and Physical Characteristics of Doxorubicin Hydrochloride Drug-Doped Salmon DNA Thin Films

Double-stranded salmon DNA (SDNA) was doped with doxorubicin hydrochloride drug molecules (DOX) to determine the binding between DOX and SDNA, and DOX optimum doping concentration in SDNA. SDNA thin films were prepared with various concentrations of DOX by drop-casting on oxygen plasma treated glass and quartz substrates. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the binding sites for DOX in SDNA, and electrical and photoluminescence (PL) analyses were used to determine the optimum doping concentration of DOX. The FTIR spectra showed that up to a concentration of 30 μM of DOX, there was a tendency for binding with a periodic orientation via intercalation between nucleosides. The current and PL intensity increased as the DOX concentration increased up to 30 μM, and then as the concentration of DOX further increased, we observed a decrease in current as well as PL quenching. Finally, the optical band gap and second band onset of the transmittance spectra were analyzed to further verify the DOX binding and optimum doping concentration into SDNA thin films as a function of the DOX concentration.

Metal electrode dependent field effect transistors made of lanthanide ion-doped DNA crystals

We fabricated lanthanide ion (Ln3+, e.g. Dy3+, Er3+, Eu3+, and Gd3+)-doped self-assembled double-crossover (DX) DNA crystals grown on the surface of field effect transistors (FETs) containing either a Cr, Au, or Ni electrode. Here we demonstrate the metal electrode dependent FET characteristics as a function of various Ln3+. The drain–source current (I ds), controlled by the drain–source voltage (V ds) of Ln3+-doped DX DNA crystals with a Cr electrode on an FET, changed significantly under various gate voltages (V g) due to the relative closeness of the work function of Cr to the energy band gap of Ln3+-DNA crystals compared to those of Au and Ni. For Ln3+-DNA crystals on an FET with either a Cr or Ni electrode at a fixed V ds, I ds decreased with increasing V g ranging from −2 to 0 V and from 0 to +3 V in the positive and negative regions, respectively. By contrast, I ds for Ln3+-DNA crystals on an FET with Au decreased with increasing V g in only the positive region due to the greater electronegativity of Au. Furthermore, Ln3+-DNA crystals on an FET exhibited behaviour sensitive to V g due to the appreciable charge carriers generated from Ln3+. Finally, we address the resistivity and the mobility of Ln3+-DNA crystals on an FET with different metal electrodes obtained from I ds–V ds and I ds–V g curves. The resistivities of Ln3+-DNA crystals on FETs with Cr and Au electrodes were smaller than those of pristine DNA crystals on an FET, and the mobility of Ln3+-DNA crystals on an FET with Cr was relatively higher than that associated with other electrodes.

Glucose waveguide sensor based on graphene

We described the fabrication of a graphene based bio-chemical sensor integrated with waveguide device. The working principle of the sensor is based on the variation of the local evanescent wave intensity according to the variation of the analytes refractive index. Graphene film was transferred onto the field-effect transistor device, and an overlay of polydimethylsiloxane (PDMS) was used as the waveguide. A few microliter drop of analyte was placed on the PDMS waveguide, and the change in the photocurrent through the graphene was monitored. Depending on the concentration of the analyte change, the local evanescent field changed and hence the photo current of the graphene changed. Furthermore, we have evaluated the sensor with the modified graphene-photo detector as well as the surface treated waveguide to enhance the selectivity. We believe that this sensing platform can be used for detection of various bio-analytes and for bio reactions.

Functional Graphene Composite Films for Surface Plasmon Resonance Sensor Technology

In this study, a surface plasmon resonance (SPR) based fiber optic sensors coated with pristine graphene and functionalized graphene composite film were evaluated. Graphene synthesized by chemical vapor deposition (CVD) is transferred on the sensing area of the optical fiber. The sensor operates based on the principle that SPR changes according to the refractive indices of analytes. This sensor was evaluated with structural DNA lattice functionalized with biotin (DXB) and streptavidin (SA). To the best of our knowledge, this is the first ever attempt to use graphene as a replacement for conventional metal films. The exact SPR phenomena and the red-shift of 7.276 nm signals for the DXB and SA combination were observed. We believe that the use of graphene as the metallic film in the SPR sensor will lead to a new area of study in biochemical sensing technology.

2.2.4 Graphene based Fiber Optic Surface Plasmon Resonance for Bio-chemical sensor Applications

In this study, a surface plasmon resonance (SPR) based fiber optic sensor coated with graphene is described. Graphene synthesized by chemical vapor deposition (CVD) is transferred on sensing area of an optical fiber. The sensor principle is based on change in SPR according to the different dielectric constants of analytes. This sensor is evaluated with biotinylated DNA lattice and protein Streptavidin. To the best of our knowledge, this is the first ever attempt to incorporate graphene as the replacement of conventional metal films. The preliminary result is encouraging results towards the analytes with excellent sensitivity. We believe that the use of graphene as a metallic film in SPR sensor will lead new path in the field of biochemical sensing technology.