Electromagnetic and optical characteristics of Nb5+-doped double-crossover and salmon DNA thin films

Bacterial Resistance and Prostate Cancer Susceptibility Toward Metal-Ion-doped DNA Complexes

DNA nanotechnology has laid a platform to construct a variety of custom-shaped nanoscale objects for functionalization of specific target materials to achieve programmability and molecular recognition. Herein, we prepared DNA nanostructures [namely, synthetic DNA rings (RDNA) and DNA duplexes extracted from salmon (SDNA)] containing metal ions (M²⁺) such as Cu²⁺, Ni²⁺, and Zn²⁺ as payloads for delivery to exterminate highly pathologic hospital bacterial strains (e.g., Escherichia coli and Bacillus subtilis) and prostate cancer cells (i.e., PC3, LNCaP, TRAMP-C1, 22Rv1, and DU145). Morphologies of these M²⁺-doped RDNA were visualized using atomic force microscopy. Interactions between M²⁺ and DNA were studied using UV-vis and Fourier transform infrared spectroscopy. Quantitative composition and chemical changes in DNA without or with M²⁺ were obtained using X-ray photoelectron spectroscopy. In addition, M²⁺-doped DNA complexes were subjected to antibacterial activity studies. They showed no bacteriostatic or bactericidal effects on bacterial strains used. Finally, in vitro cellular toxicity study was conducted to evaluate the effect of pristine DNA and M²⁺-doped DNA complexes on prostate cancer cells. Cytotoxicities conferred by M²⁺-doped DNA complexes for most cell lines were significantly higher than those of M²⁺ without DNA. Cellular uptake of these complexes was confirmed by fluorescence microscopy using PhenGreen FL indicator. On the basis of our observations, DNA nanostructures can be used as safe and efficient nanocarriers for delivery of therapeutics. They have enhanced therapeutic window than bare metals.

DNA nanostructures doped with lanthanide ions for highly sensitive UV photodetectors

Deoxyribonucleic acid (DNA) and lanthanide ions (Ln³⁺) exhibit exceptional optical properties that are applicable to the development of nanoscale devices and sensors. Although DNA nanostructures and Ln³⁺ ions have been investigated for use in the current state of technology for more than a few decades, researchers have yet to develop DNA and Ln³⁺ based ultra-violet (UV) photodetectors. Here, we fabricate Ln³⁺ (such as holmium (Ho³⁺), praseodymium (Pr³⁺), and ytterbium (Yb³⁺))‒doped double crossover (DX)‒DNA lattices through substrate-assisted growth and salmon DNA (SDNA) thin films via a simple drop-casting method on oxygen (O₂) plasma-treated substrates for high performance UV photodetectors. Topological (AFM), optical (UV-vis absorption and FTIR), spectroscopic (XPS), and electrical (I‒V and photovoltage) measurements of the DX‒DNA and SDNA thin films doped with various concentrations of Ln³⁺ ([Ln³⁺]) are explored. From the AFM analysis, the optimum concentrations of various Ln³⁺ ([Ln³⁺]_O) are estimated (where the phase transition of Ln³⁺‒doped DX‒DNA lattices takes place from crystalline to amorphous) as 1.2 mM for Ho³⁺, 1.5 mM for Pr³⁺, and 1.5 mM for Yb³⁺. The binding modes and chemical states are evaluated through optical and spectroscopic analysis. From UV-vis absorption studies, we found that as the [Ln³⁺] was increased, the absorption intensity decreased up to [Ln³⁺]_O, and increased above [Ln³⁺]_O. The variation in FTIR peak intensities in the nucleobase and phosphate regions, and the changes in XPS peak intensities and peak positions detected in the N 1 s and P 2p core spectra of Ln³⁺‒doped SDNA thin films clearly indicate that the Ln³⁺ ions are properly bound between the bases (through chemical intercalation) and to the phosphate backbone (through electrostatic interactions) of the DNA molecules. Finally, the I‒V characteristics and time-dependent photovoltage of Ln³⁺‒doped SDNA thin films are measured both in the dark and under UV LED illuminations (λ_LED = 382 nm) at various illumination powers. The photocurrent and photovoltage of Ln³⁺‒doped SDNA thin films are enhanced up to the [Ln³⁺]_O compared to pristine SDNA due to the charge carriers generated from both SDNA and Ln³⁺ ions upon the absorption of light. From our observations, the photovoltages as function of illumination power suggest higher responsivities, and the photovoltages as function of time are almost constant which indicates the stability and retention characteristics of the Ln³⁺‒doped SDNA thin films. Hence, our method which provides an efficient doping of Ln³⁺ into the SDNA with a simple fabrication process might be useful in the development of high-performance optoelectronic devices and sensors.

Topological, chemical and electro-optical characteristics of riboflavin-doped artificial and natural DNA thin films

DNA is considered as a useful building bio-material, and it serves as an efficient template to align functionalized nanomaterials. Riboflavin (RF)-doped synthetic double-crossover DNA (DX-DNA) lattices and natural salmon DNA (SDNA) thin films were constructed using substrate-assisted growth and drop-casting methods, respectively, and their topological, chemical and electro-optical characteristics were evaluated. The critical doping concentrations of RF ([RF]C, approx. 5 mM) at given concentrations of DX-DNA and SDNA were obtained by observing the phase transition (from crystalline to amorphous structures) of DX-DNA and precipitation of SDNA in solution above [RF]C. [RF]C are verified by analysing the atomic force microscopy images for DX-DNA and current, absorbance and photoluminescence (PL) for SDNA. We study the physical characteristics of RF-embedded SDNA thin films, using the Fourier transform infrared spectrum to understand the interaction between the RF and DNA molecules, current to evaluate the conductance, absorption to understand the RF binding to the DNA and PL to analyse the energy transfer between the RF and DNA. The current and UV absorption band of SDNA thin films decrease up to [RF]C followed by an increase above [RF]C. By contrast, the PL intensity illustrates the reverse trend, as compared to the current and UV absorption behaviour as a function of the varying [RF]. Owing to the intense PL characteristic of RF, the DNA lattices and thin films with RF might offer immense potential to develop efficient bio-sensors and useful bio-photonic devices.