Label-Free Imaging of DNA Interactions with 2D Materials.

Two-dimensional (2D) materials offer potential as substrates for biosensing devices, as their properties can be engineered to tune interactions between the surface and biomolecules. Yet, not many methods can measure these interactions in a liquid environment without introducing labeling agents such as fluorophores. In this work, we harness interferometric scattering (iSCAT) microscopy, a label-free imaging technique, to investigate the interactions of single molecules of long dsDNA with 2D materials. The millisecond temporal resolution of iSCAT allows us to capture the transient interactions and to observe the dynamics of unlabeled DNA binding to a hexagonal boron nitride (hBN) surface in solution for extended periods (including a fraction of 10%, of trajectories lasting longer than 110 ms). Using a focused ion beam technique to engineer defects, we find that DNA binding affinity is enhanced at defects; when exposed to long lanes, DNA binds preferentially at the lane edges. Overall, we demonstrate that iSCAT imaging is a useful tool to study how biomolecules interact with 2D materials, a key component in engineering future biosensors.

Fabrication of Infrared-Compatible Nanofluidic Devices for Plasmon-Enhanced Infrared Absorption Spectroscopy.

Nanofluidic devices have offered us fascinating analytical platforms for chemical and bioanalysis by exploiting unique properties of liquids and molecules confined in nanospaces. The increasing interests in nanofluidic analytical devices have triggered the development of new robust and sensitive detection techniques, especially label-free ones. IR absorption spectroscopy is one of the most powerful biochemical analysis methods for identification and quantitative measurement of chemical species in the label-free and non-invasive fashion. However, the low sensitivity and the difficulties in fabrication of IR-compatible nanofluidic devices are major obstacles that restrict the applications of IR spectroscopy in nanofluidics. Here, we realized the bonding of CaF2 and SiO2 at room temperature and demonstrated an IR-compatible nanofluidic device that allowed the IR spectroscopy in a wide range of mid-IR regime. We also performed the integration of metal-insulator-metal perfect absorber metamaterials into nanofluidic devices for plasmon-enhanced infrared absorption spectroscopy with ultrahigh sensitivity. This study also shows a proof-of-concept of the multi-band absorber by combining different types of nanostructures. The results indicate the potential of implementing metamaterials in tracking several characteristic molecular vibrational modes simultaneously, making it possible to identify molecular species in mixture or complex biological entities.

The evolutionarily conserved deubiquitinase UBH1/UCH-L1 augments DAF7/TGF-ß signaling, inhibits dauer larva formation, and enhances lung tumorigenesis.

Modification of the transforming growth factor ß (TGF-ß) signaling components by (de)ubiquitination is emerging as a key regulatory mechanism that controls cell signaling responses in health and disease. Here, we show that the deubiquitinating enzyme UBH-1 in Caenorhabditis elegans and its human homolog, ubiquitin C-terminal hydrolase-L1 (UCH-L1), stimulate DAF-7/TGF-ß signaling, suggesting that this mode of regulation of TGF-ß signaling is conserved across animal species. The dauer larva-constitutive C. elegans phenotype caused by defective DAF-7/TGF-ß signaling was enhanced and suppressed, respectively, by ubh-1 deletion and overexpression in the loss-of-function genetic backgrounds of daf7, daf-1/TGF-ßRI, and daf4/R-SMAD, but not of daf-8/R-SMAD. This suggested that UBH-1 may stimulate DAF-7/TGF-ß signaling via DAF-8/R-SMAD. Therefore, we investigated the effect of UCH-L1 on TGF-ß signaling via its intracellular effectors, i.e. SMAD2 and SMAD3, in mammalian cells. Overexpression of UCH-L1, but not of UCH-L3 (the other human homolog of UBH1) or of the catalytic mutant UCH-L1C90A, enhanced TGF-ß/SMAD-induced transcriptional activity, indicating that the deubiquitination activity of UCH-L1 is indispensable for enhancing TGF-ß/SMAD signaling. We also found that UCH-L1 interacts, deubiquitinates, and stabilizes SMAD2 and SMAD3. Under hypoxia, UCH-L1 expression increased and TGF-ß/SMAD signaling was potentiated in the A549 human lung adenocarcinoma cell line. Notably, UCH-L1-deficient A549 cells were impaired in tumorigenesis, and, unlike WT UCH-L1, a UCH-L1 variant lacking deubiquitinating activity was unable to restore tumorigenesis in these cells. These results indicate that UCH-L1 activity supports DAF-7/TGF-ß signaling and suggest that UCH-L1's deubiquitination activity is a potential therapeutic target for managing lung cancer.

Enhancing Detection Sensitivity of ZnO-Based Infrared Plasmonic Sensors Using Capped Dielectric Ga2O3 Layers for Real-Time Monitoring of Biological Interactions.

Surface plasmon resonances on Ga-doped ZnO (ZnO/Ga) layer surfaces (ZnO-SPRs) have attracted substantial attention as alternative plasmonic materials in the infrared range. We present further enhancement of the detection limits of ZnO-SPRs to monitor biological interactions by introducing thin dielectric layers into ZnO-SPRs, which remarkably modify the electric fields and the corresponding decay lengths on the sensing surfaces. The presence of a high-permittivity dielectric layer of Ga2O3 provides high wavelength sensitivities of the ZnO-SPRs due to the strongly confined electric fields. The superior sensing capabilities of the proposed samples were verified by real-time monitoring of the biological interactions between biotin and streptavidin molecules. Introduction of the high-permittivity dielectric layer into ZnO-SPRs effectively enhances the detection sensitivity and therefore allowed for the observation of biological interactions. This paper provides useful information for the development of optical detection techniques for use in biological fields based on ZnO from the viewpoints of plasmonic applications.