ACS Nanoscience Au最新文献

Matrix stones are a rare form of kidney stones. They feature a high percentage of hydrogel-like organic matter, and their formation is closely associated with urinary tract infections. Herein, comprehensive materials and biochemical approaches were taken to map the organic–inorganic interface and gather insights into the host–microbe interplay in pathological renal biomineralization. Surgically extracted soft and slimy matrix stones were examined using micro-X-ray computed tomography and various microspectroscopy techniques. Higher-mineral-density laminae were positive for calcium-bound Alizarin red. Lower-mineral-density laminae revealed periodic acid-Schiff-positive organic filamentous networks of varied thickness. These organic filamentous networks, which featured a high polysaccharide content, were enriched with zinc, carbon, and sulfur elements. Neutrophil extracellular traps (NETs) along with immune response-related proteins, including calprotectin, myeloperoxidase, CD63, and CD86, also were identified in the filamentous networks. Expressions of NETs and upregulation of polysaccharide-rich mucin secretion are proposed as a part of the host immune defense to “trap” pathogens. These host−microbe derived organic matrices can facilitate heterogeneous nucleation and precipitation of inorganic particulates, resulting in macroscale aggregates known as “matrix stones”. These insights into the plausible aggregation of constituents through host–microbe interplay underscore the unique “double-edged sword” effect of the host immune response to pathogens and the resulting renal biominerals.

Vanadium dioxide (VO₂) can adopt many different crystal structures at ambient temperature and pressure, each with different, and often desirable, electronic, optical, and chemical properties. Understanding how to control which crystal phase forms under various reaction conditions is therefore crucial to developing VO₂ for various applications. This paper describes the impact of ligand acidity on the formation of VO₂ nanocrystals from the solvothermal reaction of vanadyl acetylacetonate (VO(acac)₂) with stoichiometric amounts of water. Carboxylic acids examined herein favor the formation of the monoclinic VO₂(B) phase over the tetragonal VO₂(A) phase as the concentration of water in the reaction increases. However, the threshold concentration of water required to obtain phase-pure VO₂(B) nanocrystals increases as the pK_a of the carboxylic acid decreases. We also observe that increasing the concentration of VO(acac)₂ or the concentration of acid while keeping the concentration of water constant favors the formation of VO₂(A). Single-crystal electron diffraction measurements enable the identification of vanadyl carboxylate species formed in reactions that do not contain enough water to promote the formation of VO₂. Increasing the length of the carbon chain on aliphatic carboxylic acids did not impact the phase of VO₂ nanocrystals obtained but did result in a change from nanorod to nanoplatelet morphology. These results suggest that inhibiting the rate of hydrolysis of the VO(acac)₂ precursor either by decreasing the ratio of water to VO(acac)₂ or by increasing the fraction of water molecules that are protonated favors the formation of VO₂(A) over VO₂(B).

In recent years, fluorescence microscopy has been revolutionized. Reversible switching of fluorophores has enabled circumventing the limits imposed by diffraction. Thus, resolution down to the molecular scale became possible. However, to the best of our knowledge, the application of the principles underlying super-resolution fluorescence microscopy to reflection microscopy has not been experimentally demonstrated. Here, we present the first evidence that this is indeed possible. A layer of photochromic molecules referred to as the absorbance modulation layer (AML) is applied to a sample under investigation. The AML-coated sample is then sequentially illuminated with a one-dimensional (1D) focal intensity distribution (similar to the transverse laser mode TEM01) at wavelength λ₁ = 325 nm to create a subwavelength aperture within the AML, followed by illumination with a Gaussian focal spot at λ₂ = 633 nm for high-resolution imaging. Using this method, called absorbance modulation imaging (AMI) in reflection, we demonstrate a 2.4-fold resolution enhancement over the diffraction limit for a numerical aperture (NA) of 0.65 and wavelength (λ) of 633 nm.

Developing new techniques to prepare free-standing tubular scaffolds has always been a challenge in the field of regenerative medicine. Here, we report a new and simple way to prepare free-standing collagen constructs with rolled-up architecture by self-assembling nanofibers on porous alumina (Al₂O₃) textiles modified with different silanes, carbon or gold. Following self-assembly and cross-linking with glutaraldehyde, collagen nanofibers spontaneously rolled up on the modified Al₂O₃ textiles and detached. The resulting collagen constructs had an inner diameter of approximately 2 to 4 mm in a rolled-up state and could be easily detached from the underlying textiles. Mechanical testing of wet collagen scaffolds following detachment yielded mean values of 3.5 ± 1.9 MPa for the tensile strength, 41.0 ± 20.8 MPa for the Young’s modulus and 8.1 ± 3.7% for the elongation at break. No roll-up was observed on Al₂O₃ textiles without any modification, where collagen did not assemble into fibers, either. Blends of collagen and chitosan were also found to roll into fibrous constructs on silanized Al₂O₃ textiles, while fibrinogen nanofibers or blends of collagen and elastin did not yield such structures. Based on these differences, we hypothesize that textile surface charge and protein charge, in combination with the porous architecture of protein nanofibers and differences in mechanical strain, are key factors in inducing a scaffold roll-up. Further studies are required to develop the observed roll-up effect into a reproducible biofabrication process that can enable the controlled production of free-standing collagen-based tubes for soft tissue engineering.

Plasmonic catalysis provides a possible means for driving chemical reactions under relatively mild conditions. Rational design of these systems is impeded by the difficulty in understanding the electron dynamics and their interplay with reactions. Real-time, time-dependent density functional theory (RT-TDDFT) can provide dynamic information on excited states in plasmonic systems, including those relevant to plasmonic catalysis, at time scales and length scales that are otherwise out of reach of many experimental techniques. Here, we discuss previous RT-TDDFT studies of plasmonic systems, focusing on recent work that gains insight into plasmonic catalysis. These studies provide insight into plasmon dynamics, including size effects and the role of specific electronic states. Further, these studies provide significant insight into mechanisms underlying plasmonic catalysis, showing the importance of charge transfer between metal and adsorbate states, as well as local field enhancement, in different systems.

Cation exchange is becoming extensively used for nanocrystal (NC) doping in order to produce NCs with unique optical and electronic properties. However, despite its ever-increasing use, the relationships between the cation exchange process, its doped NC products, and the resulting NC photophysics are not well characterized. For example, similar doping procedures on NCs with the same chemical compositions have resulted in quite different photophysics. Through a detailed single molecule investigation of a postsynthesis Ag⁺ doping of CdSe NCs, a number of species were identified within a single doped NC sample, suggesting the differences in the optical properties of the various synthesis methods are due to the varied contributions of each species. Electrostatic force microscopy (EFM), electron energy loss spectroscopy (EELS) mapping, and single molecule photoluminescence (PL) studies were used to identify four possible species resulting from the Ag⁺-CdSe cation exchange doping process. The heterogeneity of these samples shows the difficulty in controlling a postsynthesis cation exchange method to produce homogeneous samples needed for use in any potential application. Additionally, the heterogeneity in the doped samples demonstrates that significant care must be taken in describing the ensemble or average characteristics of the sample.

Understanding how nanoparticles (NPs) interact with biological systems is important in many biomedical research areas. However, the heterogeneous nature of biological systems, including the existence of numerous cell types and multitudes of key environmental factors, makes these interactions extremely challenging to investigate precisely. Here, using a single-cell-based, high-dimensional mass cytometry approach, we demonstrated that the presence of protein corona has significant influences on the cellular associations and cytotoxicity of gold NPs for human immune cells, and those effects vary significantly with the types of immune cells and their subsets. The altered surface functionality of protein corona reduced the cytotoxicity and cellular association of gold NPs in most cell types (e.g., monocytes, dendritic cells, B cells, natural killer (NK) cells, and T cells) and those immune cells selected different endocytosis pathways such as receptor-mediated endocytosis, phagocytosis, and micropinocytosis. However, even slight alterations in the major cell type (phagocytic cells and non-phagocytic cells) and T cell subsets (e.g., memory and naive T cells) resulted in significant protein corona-dependent variations in their cellular dose of gold NPs. Especially, naive T killer cells exhibited additional heterogeneity than memory T killer cells, with clusters exhibiting distinct cellular association patterns in single-cell contour plots. This multi-parametric analysis of mass cytometry data established a conceptual framework for a more holistic understanding of how the human immune system responds to external stimuli, paving the way for the application of precisely engineered NPs as promising tools of nanomedicine under various clinical settings, including targeted drug delivery and vaccine development.

In our continuing pursuit to generate, understand, and control the morphology of organic nanofilaments formed by molecules with a bent molecular shape, we here report on two bent-core molecules specifically designed to permit a phase or morphology change upon exposure to an applied electric field or irradiation with UV light. To trigger a response to an applied electric field, conformationally rigid chiral (S,S)-2,3-difluorooctyloxy side chains were introduced, and to cause a response to UV light, an azobenzene core was incorporated into one of the arms of the rigid bent core. The phase behavior as well as structure and morphology of the formed phases and nanofilaments were analyzed using differential scanning calorimetry, cross-polarized optical microscopy, circular dichroism spectropolarimetry, scanning and transmission electron microscopy, UV–vis spectrophotometry, as well as X-ray diffraction experiments. Both bent-core molecules were characterized by the coexistence of two nanoscale morphologies, specifically helical nanofilaments (HNFs) and layered nanocylinders, prior to exposure to an external stimulus and independent of the cooling rate from the isotropic liquid. The application of an electric field triggers the disappearance of crystalline nanofilaments and instead leads to the formation of a tilted smectic liquid crystal phase for the material featuring chiral difluorinated side chains, whereas irradiation with UV light results in the disappearance of the nanocylinders and the sole formation of HNFs for the azobenzene-containing material. Combined results of this experimental study reveal that in addition to controlling the rate of cooling, applied electric fields and UV irradiation can be used to expand the toolkit for structural and morphological control of suitably designed bent-core molecule-based structures at the nanoscale.

Understanding the dose-dependent effect of over-the-counter drugs on red blood cells (RBCs) is crucial for hematology and digital pathology. Yet, it is challenging to continuously record the real-time, drug-induced shape changes of RBCs in a label-free manner. Here, we demonstrate digital holotomography (DHTM)-enabled real-time, label-free concentration-dependent and time-dependent monitoring of ibuprofen on RBCs from a healthy donor. The RBCs are segmented based on three-dimensional (3D) and four-dimensional (4D) refractive index tomograms, and their morphological and chemical parameters are retrieved with their shapes classified using machine learning. We directly observed the formation and motion of spicules on the RBC membrane when aqueous solutions of ibuprofen were drop-cast on wet blood, creating rough-membraned echinocyte forms. At low concentrations of 0.25–0.50 mM, the ibuprofen-induced morphological change was transient, but at high concentrations (1–3 mM) the spiculated RBC remained over a period of up to 1.5 h. Molecular simulations confirmed that aggregates of ibuprofen molecules at high concentrations significantly disrupted the RBC membrane structural integrity and lipid order but produced negligible effect at low ibuprofen concentrations. Control experiments on the effect of urea, hydrogen peroxide, and aqueous solutions on RBCs showed zero spicule formation. Our work clarifies the dose-dependent chemical effects on RBCs using label-free microscopes that can be deployed for the rapid detection of overdosage of over-the-counter and prescribed drugs.