Characterization of the role of Kunitz-type protease inhibitor domain in dimerization of amyloid precursor protein.

A major difference between amyloid precursor protein (APP) isoforms (APP695 and APP751) is the existence of a Kunitz type protease inhibitor (KPI) domain which has a significant impact on the homo- and hetero-dimerization of APP isoforms. However, the exact molecular mechanisms of dimer formation remain elusive. To characterize the role of the KPI domain in APP dimerization, we performed a single molecule pull down (SiMPull) assay where homo-dimerization between tethered APP molecules and soluble APP molecules was highly preferred regardless of the type of APP isoforms, while hetero-dimerization between tethered APP751 molecules and soluble APP695 molecules was limited. We further investigated the domain level APP-APP interactions using coarse-grained models with the Martini force field. Though the model initial ternary complexes (KPI-E1, KPI-KPI, KPI-E2, E1-E1, E2-E2, and E1-E2) generated using HADDOCK (HD) and AlphaFold2 (AF2), the binding free energy profiles and the binding affinities of the domain combinations were investigated via the umbrella sampling with Martini force field. Additionally, membrane-bound microenvironments at the domain level were modeled. As a result, it was revealed that the KPI domain has a stronger attractive interaction with itself than the E1 and E2 domains, as reported elsewhere. Thus, the KPI domain of APP751 may form additional attractive interactions with E1, E2 and the KPI domain itself, whereas it is absent in APP695. In conclusion, we found that the APP751 homo-dimer formation is predominant than the homodimerization in APP695, which is facilitated by the presence of the KPI domain.

DNA Transformations for Diagnosis and Therapy.

Due to its unique physical and chemical characteristics, DNA, which is known only as genetic information, has been identified and utilized as a new material at an astonishing rate. The role of DNA has increased dramatically with the advent of various DNA derivatives such as DNA-RNA, DNA-metal hybrids, and PNA, which can be organized into 2D or 3D structures by exploiting their complementary recognition. Due to its intrinsic biocompatibility, self-assembly, tunable immunogenicity, structural programmability, long stability, and electron-rich nature, DNA has generated major interest in electronic and catalytic applications. Based on its advantages, DNA and its derivatives are utilized in several fields where the traditional methodologies are ineffective. Here, the present challenges and opportunities of DNA transformations are demonstrated, especially in biomedical applications that include diagnosis and therapy. Natural DNAs previously utilized and transformed into patterns are not found in nature due to lack of multiplexing, resulting in low sensitivity and high error frequency in multi-targeted therapeutics. More recently, new platforms have advanced the diagnostic ability and therapeutic efficacy of DNA in biomedicine. There is confidence that DNA will play a strong role in next-generation clinical technology and can be used in multifaceted applications.

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

We report the fabrication and physical characteristics of niobium ion (Nb5+)-doped double-crossover DNA (DX-DNA) and salmon DNA (SDNA) thin films. Different concentrations of Nb5+ ([Nb5+]) are coordinated into the DNA molecules, and the thin films are fabricated via substrate-assisted growth (DX-DNA) and drop-casting (SDNA) on oxygen plasma treated substrates. We conducted atomic force microscopy to estimate the optimum concentration of Nb5+ ([Nb5+]O = 0.08 mM) in Nb5+-doped DX-DNA thin films, up to which the DX-DNA lattices maintain their structures without deformation. X-ray photoelectron spectroscopy (XPS) was performed to probe the chemical nature of the intercalated Nb5+ in the SDNA thin films. The change in peak intensities and the shift in binding energy were witnessed in XPS spectra to explicate the binding and charge transfer mechanisms between Nb5+ and SDNA molecules. UV-visible, Raman, and photoluminescence (PL) spectra were measured to determine the optical properties and thus investigate the binding modes, Nb5+ coordination sites in Nb5+-doped SDNA thin films, and energy transfer mechanisms, respectively. As [Nb5+] increases, the absorbance peak intensities monotonically increase until ∼[Nb5+]O and then decrease. However, from the Raman measurements, the peak intensities gradually decrease with an increase in [Nb5+] to reveal the binding mechanism and binding sites of metal ions in the SDNA molecules. From the PL, we observe the emission intensities to reduce them at up to ∼[Nb5+]O and then increase after that, expecting the energy transfer between the Nb5+ and SDNA molecules. The current-voltage measurement shows a significant increase in the current observed as [Nb5+] increases in the SDNA thin films when compared to that of pristine SDNA thin films. Finally, we investigate the temperature dependent magnetization in which the Nb5+-doped SDNA thin films reveal weak ferromagnetism due to the existence of tiny magnetic dipoles in the Nb5+-doped SDNA complex.

Characterization of Integrin Molecular Tension of Human Breast Cancer Cells on Anisotropic Nanopatterns.

Physical interactions between cells and micro/nanometer-sized architecture presented in an extracellular matrix (ECM) environment significantly influence cell adhesion and morphology, often facilitating the incidence of diseases, such as cancer invasion and metastasis. Sensing and responding to the topographical cues are deeply associated with a physical interplay between integrins, ligands, and mechanical force transmission, ultimately determining diverse cell behavior. Thus, how the tension applied to the integrin-ligand bonds controls cells' response to the topographical cues needs to be elucidated through quantitative analysis. Here, in this brief research report, we reported a novel platform, termed "topo-tension gauge tether (TGT)," to visualize single-molecule force applied to the integrin-ligand on the aligned anisotropic nanopatterns. Using the topo-TGT assay, first, topography-induced adhesion and morphology of cancerous and normal cells were compared with the pre-defined peak integrin tension. Next, spatial integrin tensions underneath cells were identified using reconstructed integrin tension maps. As a result, we characterized each cell's capability to comply with nanotopographies and the magnitude of the spatial integrin tension. Altogether, the quantitative information on integrin tension will be a valuable basis for understanding the biophysical mechanisms underlying the force balance influencing adhesion to the topographical cues.

Protein-Encoding Free-Standing RNA Hydrogel for Sub-Compartmentalized Translation.

RNA can self-fold into complex structures that can serve as major biological regulators in protein synthesis and in catalysis. Due to the abundance of structural primitives and functional diversity, RNA has been utilized for designing nature-defined goals despite its intrinsic chemical instability and lack of technologies. Here, a robust, free-standing RNA hydrogel is developed through a sequential process involving both ligation and rolling circle transcription to form RNA G-quadruplexes, capable of both catalytic activity and enhancing expression of several proteins in sub-compartmentalized, phase-separated translation environments. The observations suggest that this hydrogel will expand RNA research and impact practical RNA principles and applications.

DNA Multilayers with Mono-, Hetero-, and Mixed-Type Plasmonic Nanoparticles for Broadband Absorption and Energy Storage.

DNA incorporated with functional materials has led to development of hybrids with different functionalities. Among the functional materials, metal nanoparticles such as Au, Ag, and Cu (also known as plasmonic nanoparticles [PNPs]), which can exhibit surface plasmon resonance, are good candidates to fabricate useful optoelectronic devices and sensors. Here, we constructed PNP-assorted DNA (PNP-DNA) layers with mono-, hetero-, and mixed-type PNPs formed by successive spin-coating to obtain the required number of layers. Further, structural analysis of PNP-DNA was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The optical evaluation was carried out by Raman, UV-visible, and photoluminescence (PL) spectroscopies followed by measurement of capacitance. Cross-sectional SEM images of DNA single, DNA triple, and PNP-DNA triple layers indicated their thicknesses (i.e., 90, 280, and 395 nm, respectively), while the base pair distance of double helixes (∼0.4 nm) for the PNP-DNA multilayers was measured by XRD. The presence of Ag, Au, and Cu PNPs was confirmed by existence of spin-orbit coupling in the corresponding XPS spectra. The addition of PNPs in DNA multilayers caused significant enhancement in the intensities of Raman bands (especially in the range of 1200-1850 cm-1) due to Raman resonance. UV-vis absorption and PL demonstrated stacking-order-dependent and layer-dependent light absorption and energy transfer (observed as quenching of fluorescence between PNPs and DNA), respectively. We observed n-type semiconducting behavior with a relatively higher dielectric constant for a PNP-assorted DNA single layer at a low frequency of 5 kHz. The dielectric constants of all samples decreased exponentially with increased frequency. Upon addition of PNPs, enhancement in the dielectric constant as well as capacitance was noted. Consequently, the simple fabrication method used in this study can be adopted to construct various nanomaterial-assorted DNA multilayers whose specific functionalities may be controlled with high efficiency.

High performance UV photodetectors using Nd3+ and Er3+ single- and co-doped DNA thin films.

Even though lanthanide ion (Ln3+)-doped DNA nanostructures have been utilized in various applications, they are rarely employed for photovoltage generating devices because of difficulties in designing DNA-based devices that generate voltages under light illumination. Here, we constructed DNA lattices made of synthetic strands and DNA thin films extracted from salmon (SDNA) with single-doping of Nd3+ or Er3+ and co-doping of Nd3+/Er3+ for high performance UV detection. The topological change of the DNA double-crossover (DX) lattices during the course of annealing was estimated from atomic force microscope (AFM) images to find the optimum concentration of Ln3+ ([Ln3+]O). No topological disturbance in DNA DX lattices were observed up to [Ln3+]O, and significant enhancement in the physical properties was obtained at [Ln3+]O. The interactions between Ln3+ and SDNA were examined using spectroscopic methods of UV-visible, Raman, and X-ray photoelectron spectroscopy (XPS). Current and photovoltage measurements for Ln3+-doped SDNA thin films under UV illumination with varying power intensities were conducted. Under UV illumination, the photocurrent and photovoltage of Ln3+-doped SDNA thin films increased with increasing applied external voltages and input power intensities, respectively. In addition, we observed considerable increases in photovoltage responses, i.e., 5-fold increase for Nd3+, 10-fold for Er3+, and 13-fold for Nd3+/ Er3+, compared to the pristine SDNA due to the additional charge carriers generated in Ln3+-doped SDNA thin films. Device performance was measured in terms of photovoltage responsivity and retention characteristics. These phenomena indicate the high stability and substantial endurance characteristics of Ln3+-doped SDNA thin films.

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 (λLED = 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.

Metallo-Curcumin-Conjugated DNA Complexes Induces Preferential Prostate Cancer Cells Cytotoxicity and Pause Growth of Bacterial Cells.

DNA nanotechnology can be used to create intricate DNA structures due to the ability to direct the molecular assembly of nanostructures through a bottom-up approach. Here, we propose nanocarriers composed of both synthetic and natural DNA for drug delivery. The topological, optical characteristics, and interaction studies of Cu2+/Ni2+/Zn2+-curcumin-conjugated DNA complexes were studied using atomic force microscopy (AFM), UV-vis spectroscopy, Fourier transform infrared and mass spectroscopy. The maximum release of metallo-curcumin conjugates from the DNA complexes, triggered by switching the pH, was found in an acidic medium. The bacterial growth curves of E. coli and B. subtilis displayed a prolonged lag phase when tested with the metallo-curcumin-conjugated DNA complexes. We also tested the in vitro cytotoxicity of the metallo-curcumin-conjugated DNA complexes to prostate cancer cells using an MTS assay, which indicated potent growth inhibition of the cells. Finally, we studied the cellular uptake of the complexes, revealing that DNA complexes with Cu2+/Ni2+-curcumin exhibited brighter fluorescence than those with Zn2+-curcumin.

Streptavidin-Decorated Algorithmic DNA Lattices Constructed by Substrate-Assisted Growth Method.

The ultimate goal of DNA computing is to store information at higher density and solve complex problems with less computational time and minimal error. Most algorithmic DNA lattices have been constructed using the free-solution growth (FSG) annealing method, and hairpin-embedded DNA rule tiles have been introduced in most algorithmic implementations to differentiate 0- and 1-bit information. Here, we developed streptavidin (SA)-decorated algorithmic COPY (produced line-like patterns with biotinylated 1-bit rule tiles) and XOR (triangle-like patterns) lattices constructed by a substrate-assisted growth (SAG) method and FSG. SA decoration in algorithmic lattices provides an efficient platform for visualizing bit information, and the SAG method in algorithmic assembly offers full coverage of algorithmic lattices on a substrate with a relatively lower DNA concentration than previous methods. The algorithmic COPY and XOR lattices assembled with various ratios of 0- and 1-bit rule tiles were verified by atomic force microscopy. We found that even asymmetric DNA patterns produced by certain algorithmic logic gates could be easily constructed by SAG. Finally, we evaluated sorting factors and error rates of algorithmic COPY and XOR lattices to determine the bit population and quality of the algorithmic assembly. Because of the catalytic effect of the substrate, the sorting factor of algorithmic DX-DNA lattices did not greatly influence the specific rules (i.e., COPY and XOR logic gates) annealed by SAG. Additionally, we found that the overall error rates of algorithmic DX-DNA lattices prepared by the FSG and SAG methods were low, within the range of 1-3%. Hence, the self-assembled algorithmic patterns generated with DNA molecules may serve as a scaffold for molecular demultiplexing circuits and computing.

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.

Coverage percentage and raman measurement of cross-tile and scaffold cross-tile based DNA nanostructures.

We present two free-solution annealed DNA nanostructures consisting of either cross-tile CT1 or CT2. The proposed nanostructures exhibit two distinct structural morphologies, with one-dimensional (1D) nanotubes for CT1 and 2D nanolattices for CT2. When we perform mica-assisted growth annealing with CT1, a dramatic dimensional change occurs where the 1D nanotubes transform into 2D nanolattices due to the presence of the substrate. We assessed the coverage percentage of the 2D nanolattices grown on the mica substrate with CT1 and CT2 as a function of the concentration of the DNA monomer. Furthermore, we fabricated a scaffold cross-tile (SCT), which is a new design of a modified cross-tile that consists of four four-arm junctions with a square aspect ratio. For SCT, eight oligonucleotides are designed in such a way that adjacent strands with sticky ends can produce continuous arms in both the horizontal and vertical directions. The SCT was fabricated via free-solution annealing, and self-assembled SCT produces 2D nanolattices with periodic square cavities. All structures were observed via atomic force microscopy. Finally, we fabricated divalent nickel ion (Ni(2+))- and trivalent dysprosium ion (Dy(3+))-modified 2D nanolattices constructed with CT2 on a quartz substrate, and the ion coordinations were examined via Raman spectroscopy.