Lipid-Functionalized Single-Walled Carbon Nanotubes as Probes for Screening Cell Wall Disruptors.

Membrane-active molecules are of great importance to drug delivery and antimicrobials applications. While the ability to prototype new membrane-active molecules has improved greatly with the advent of automated chemistries and rapid biomolecule expression techniques, testing methods are still limited by throughput, cost, and modularity. Existing methods suffer from feasibility constraints of working with pathogenic living cells and by intrinsic limitations of model systems. Herein, we demonstrate an abiotic sensor that uses semiconducting single-walled carbon nanotubes (SWCNTs) as near-infrared fluorescent transducers to report membrane interactions. This sensor is composed of SWCNTs aqueously suspended in lipid, creating a cylindrical, bilayer corona; these SWCNT probes are very sensitive to solvent access (changes in permittivity) and thus report morphological changes to the lipid corona by modulation of fluorescent signals, where binding and disruption are reported as brightening and attenuation, respectively. This mechanism is first demonstrated with chemical and physical membrane-disruptive agents, including ethanol and sodium dodecyl sulfate, and application of electrical pulses. Known cell-penetrating and antimicrobial peptides are then used to demonstrate how the dynamic response of these sensors can be deconvoluted to evaluate different parallel mechanisms of interaction. Last, SWCNTs functionalized in several different bacterial lipopolysaccharides (Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli) are used to evaluate a panel of known membrane-disrupting antimicrobials to demonstrate that drug selectivity can be assessed by suspension of SWCNTs with different membrane materials.

Solution-Processed Bismuth Halide Perovskite Thin Films: Influence of Deposition Conditions and A-Site Alloying on Morphology and Optical Properties.

Bismuth-based halide perovskites have been proposed as a potential nontoxic alternative to lead halide perovskites; however, they have not realized suitable performance. Their poor performance has been attributed to substandard film morphologies and too wide of a band gap for many applications. Herein we used a two-step deposition procedure to convert BiI3 thin films into A3Bi2I9 (A = FA+, MA+, Cs+, or Rb+), which resulted in a substantial improvement in film morphology, a larger band gap, and greater compositional tunability compared toresults when using aconventional single-step deposition technique. Additionally, we attempted to reduce the undesirably wide band gap in Rb3Bi2I9 thin films by inducing chemical pressures through cation-size mismatch, with an underlying hypothesis that cation-size mismatch could induce compressive strain within the 2D Rb3Bi2I9 lattice. However, we found that all A xRb3- xBi2I9 compositions with x > 0 adopted the 0D structure, and no changes to the band gap were observed with alloy. These results imply that the band gap of A xRb3- xBi2I9 is insensitive to A-site alloying.