Chemical and Biomolecular Engineering

DNA-stabilized silver nanoclusters (DNA-AgN) are atomically precise and sequence-tuned nanomaterials with potential applications for deep tissue biomedical imaging. Here, a dual-emissive DNA-AgN is presented with fluorescence in the first near-infrared (NIR-I) spectral window and microsecond-lived photoluminescence in the second near-infrared (NIR-II) spectral window. High-resolution electrospray ionization mass spectrometry showed that the emitter has the molecular formula (DNA)2[Ag17]11+. The crystallization of (DNA)2[Ag17]11+ was unsuccessful, which prevented the use of X-ray diffraction to determine its structure. However, sequence variations of the templating DNA oligomer provided insights into nucleobases that are critical for stabilizing the Ag1711+. Moreover, addition of an adenosine or thymidine at the 5′-end of the stabilizing DNA strand maintained the composition and photophysical properties of the (DNA)2[Ag17]11+, suggesting a potential site for conjugation with biomolecules to enable targeted labeling in future bioimaging applications.

Cephalopods, marine animals like squid, octopus, cuttlefish, or nautilus, have attracted the interest of the scientific community for many years due to their sophisticated neurophysiology, complex behavioral patterns, and stunning camouflage displays. It is thus not surprising that these animals have inspired a plethora of scientific advances in the fields of neuroscience, cell biology, and materials engineering. A part of this exciting research is reflected in the Special Issue Cephalopods: Inspired science.

Near-infrared (NIR) emitters with high two-photon absorption (2PA) cross-sections are of interest to enable in vivo imaging in the tissue transparency windows. This study explores the potential of DNA-stabilized silver nanoclusters (Ag N -DNAs) as water-soluble two-photon absorbers. We investigate 2PA of four different atomically precise Ag N -DNA species with far-red to NIR emission and varying nanocluster and ligand compositions. 2PA cross-sections, σ 2, were determined by two-photon excited luminescence (2PEL) technique for a wide wavelength range from 810 to 1400 nm. The Ag N -DNAs exhibited reversed strength of corresponding transitions in the two-photon regime, as compared to one-photon, which further demonstrates the complex photophysics of these emitters. Maximal 2PA cross-section value (∼582 GM) was observed for (DNA)3[Ag21]15+, which is stabilized by 3 DNA oligomers. (DNA)2[Ag16Cl2]8+ presented distinct 2PA behavior from the Ag N -DNAs without chlorido ligands, with a high 2PA of 176 GM at 1050 nm. Our findings support the potential of Ag N -DNAs as NIR-to-NIR two-photon probes that are both excited and emit in the NIR. Their high σ 2 and fluorescence quantum yield values result in superior two-photon brightness on the order of ∼102 GM, significantly higher than water-soluble organic fluorophores.

Photocatalytic water splitting is a promising route to low-cost, green H2. However, this approach is currently limited in its solar-to-hydrogen conversion efficiency. One major source of efficiency loss is attributed to the high rates of undesired side and back reactions, which are exacerbated by the proximity of neighboring oxidation and reduction sites. Nanoscopic oxide coatings have previously been used to selectively block undesired reactants from reaching active sites; however, a coating encapsulating the entire photocatalyst particle limits activity as it cannot facilitate both half-reactions. In this work, area selective atomic layer deposition (AS-ALD) was used to selectively deposit semipermeable TiO2 films onto model metallic cocatalysts for enhancing reaction selectivity while maintaining a high overall activity. Pt and Au were used as exemplary reduction and oxidation cocatalyst sites, respectively, where Au was deactivated toward ALD growth through self-assembled thiol monolayers while TiO2 was coated onto Pt sites. Electroanalytical measurements of monometallic thin film electrodes showed that the TiO2-encapsulated Pt effectively suppressed undesired H2 oxidation and Fe(II)/Fe(III) redox reactions while still permitting the desired hydrogen evolution reaction (HER). A planar model photocatalyst platform containing patterned interdigitated arrays of Au and Pt microelectrodes was further assessed using scanning electrochemical microscopy (SECM), demonstrating the successful use of AS-ALD to enable local reaction selectivity in a dual-reaction-site (photo)electrocatalytic system. Finally, interdigitated microelectrodes having independent potential control were used to show that selectively deposited TiO2 coatings can suppress the rate of back reactions on neighboring active sites by an order of magnitude compared with uncoated control samples.

Advanced thermal management technologies represent an important research frontier because such materials and systems show promise for enhancing personal physiological comfort and reducing building energy consumption. These technologies typically offer the advantages of excellent portability, user-friendly tunability, energy efficiency, and straightforward manufacturability, but they frequently suffer from critical challenges associated with poor breathability, inadequate wash stability, and difficult fabric integration. Within this broader context, our laboratory has previously developed heat-managing composite materials by drawing inspiration from the color-changing skin of the common squid. Herein, we describe the design, fabrication, and testing of breathable, washable, and fabric-integrated variants of our composite materials, which demonstrate state-of-the-art adaptive infrared properties and dynamic thermoregulatory functionalities. The combined findings directly advance the performance and applications scope of our bioinspired thermoregulatory composites and ultimately may guide the incorporation of desirable multifunctionality into other wearable technologies.

To combat the rise of antibiotic-resistance in bacteria and the resulting effects on healthcare worldwide, new technologies are needed that can perform rapid antibiotic susceptibility testing (AST). Conventional clinical methods for AST rely on growth-based assays, which typically require long incubation times to obtain quantitative results, representing a major bottleneck in the determination of the optimal antibiotic regimen to treat patients. Here, we demonstrate a rapid AST method based on the metabolic activity measured by fluorescence lifetime imaging microscopy (FLIM). Using lab strains and clinical isolates of Escherichia coli with tetracycline-susceptible and resistant phenotypes as models, we demonstrate that changes in metabolic state associated with antibiotic susceptibility can be quantitatively tracked by FLIM. Our results show that the magnitude of metabolic perturbation resulting from antibiotic activity correlates with susceptibility evaluated by conventional metrics. Moreover, susceptible and resistant phenotypes can be differentiated in as short as 10 min after antibiotic exposure. This FLIM-AST (FAST) method can be applied to other antibiotics and provides insights into the nature of metabolic perturbations inside bacterial cells resulting from antibiotic exposure with single cell resolution.

Characterization of the surface of iridium oxide (IrOx) materials is of crucial importance to understand catalysts for the oxygen evolution reaction (OER) in low-temperature water electrolysis. While much of our current knowledge is based on well-defined single-crystal surfaces, surface-sensitive techniques like X-ray photoelectronic spectroscopy (XPS) are relevant to characterize the nanostructures considered. In this work, we describe a simple approach to use oxygen 1s spectra as an identifier of the amorphous/crystalline characteristics of iridium oxide structures from purely amorphous to purely crystalline. This conceptual approach was validated on seven commercially available materials. The presence of oxygen-associated defects in the surface moieties/species is shown even for purely crystalline materials with defect concentration increasing with greater amorphous character. This methodology provides us with an accessible ex situ descriptor of the catalyst surface as a baseline for further studies of the impact on catalytic properties.

Macrophages in the vascular wall ingest and clear lipids, but abundant lipid accumulation leads to foam cell formation and atherosclerosis, a pathological condition often characterized by tissue stiffening. While the role of biochemical stimuli in the modulation of macrophage function is well studied, the role of biophysical cues and the molecules involved in mechanosensation are less well understood. Here, we use genetic and pharmacological tools to show extracellular oxidized low-density lipoproteins (oxLDLs) stimulate Ca²⁺ signaling through activation of the mechanically gated ion channel Piezo1. Moreover, macrophage Piezo1 expression is critical in the transduction of environmental stiffness and channel deletion suppresses, whereas a gain-of-function mutation exacerbates oxLDL uptake. Additionally, we find that depletion of myeloid Piezo1 protects from atherosclerotic plaque formation in vivo. Together, our study highlights an important role for Piezo1 and its respective mutations in macrophage mechanosensing, lipid uptake, and cardiovascular disease.

Shape-controlled alloy nanoparticle catalysts have been shown to exhibit improved performance in the oxygen reduction reaction (ORR) in liquid half-cells. However, translating the success to catalyst layers in fuel cells faces challenges due to the more demanding operation conditions in membrane electrode assembly (MEA). Balancing durability and activity is crucial. Here, we developed a strategy that limits the atomic diffusion within surface layers, fostering the phase transition and shape retention during thermal treatment. This enables selective transformation of platinum-iron nanowire surfaces into intermetallic structures via atomic ordering at a low temperature. The catalysts exhibit enhanced MEA stability with 50% less Fe loss while maintaining high catalytic activity comparable to that in half-cells. Density functional calculations suggest that the ordered intermetallic surface stabilizes morphology against rapid corrosion and improves the ORR activity. The surface engineering through atomic ordering presents potential for practical application in fuel cells with shape-controlled Pt-based alloy catalysts.

Since its inception nearly a half century ago, CHARMM has been playing a central role in computational biochemistry and biophysics. Commensurate with the developments in experimental research and advances in computer hardware, the range of methods and applicability of CHARMM have also grown. This review summarizes major developments that occurred after 2009 when the last review of CHARMM was published. They include the following: new faster simulation engines, accessible user interfaces for convenient workflows, and a vast array of simulation and analysis methods that encompass quantum mechanical, atomistic, and coarse-grained levels, as well as extensive coverage of force fields. In addition to providing the current snapshot of the CHARMM development, this review may serve as a starting point for exploring relevant theories and computational methods for tackling contemporary and emerging problems in biomolecular systems. CHARMM is freely available for academic and nonprofit research at https://academiccharmm.org/program.