Solution-Based Photo-Patterned Gold Film Formation on Silicon Nitride

Characterization of Flagellar Filaments and Flagellin through Optical Microscopy and Label-Free Nanopore Responsiveness

In this study, we investigated the translocation characteristics of flagellar filaments (Salmonella typhimurium) and flagellin subunits through silicon nitride nanopores in tandem with optical microscopy analysis. Even though untagged flagella are dark to the optical method, the label-free nature of the nanopore sensor allows it to characterize both tagged (Cy3) and pristine forms of flagella (including real-time developments). Flagella were depolymerized to flagellin subunits at ∼65 °C (most commonly reported temperature), ∼70 °C, ∼75 °C, and ∼80 °C to investigate the effect of temperature (T_depol) on depolymerization. The change in conductance (ΔG) profiles corresponding to T_depol ∼65 °C and ∼70 °C were bracketed within the flagellin monomer profile whereas those of ∼75 °C and ∼80 °C extended beyond this profile, suggesting a change to the native protein state. The molecular radius calculated from the excluded electrolyte volume of flagellin through nanopore-based ΔG characteristics for each T_depol of ∼65 °C, ∼70 °C, ∼75 °C, and ∼80 °C yielded ∼4.2 ± 0.2 nm, ∼4.3 ± 0.3 nm, ∼4.1 ± 0.2 nm, and ∼4.7 ± 0.5 nm, respectively. This, along with ΔG (plateaued values) and translocation time profiles, points to the possibility of flagellin misfolding at ∼80 °C.

Through a Window, Brightly: A Review of Selected Nanofabricated Thin-Film Platforms for Spectroscopy, Imaging, and Detection

We present a review of the use of selected nanofabricated thin films to deliver a host of capabilities and insights spanning bioanalytical and biophysical chemistry, materials science, and fundamental molecular-level research. We discuss approaches where thin films have been vital, enabling experimental studies using a variety of optical spectroscopies across the visible and infrared spectral range, electron microscopies, and related techniques such as electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and single molecule sensing. We anchor this broad discussion by highlighting two particularly exciting exemplars: a thin-walled nanofluidic sample cell concept that has advanced the discovery horizons of ultrafast spectroscopy and of electron microscopy investigations of in-liquid samples; and a unique class of thin-film-based nanofluidic devices, designed around a nanopore, with expansive prospects for single molecule sensing. Free-standing, low-stress silicon nitride membranes are a canonical structural element for these applications, and we elucidate the fabrication and resulting features-including mechanical stability, optical properties, X-ray and electron scattering properties, and chemical nature-of this material in this format. We also outline design and performance principles and include a discussion of underlying material preparations and properties suitable for understanding the use of alternative thin-film materials such as graphene.