The Promise of Emergent Nanobiotechnologies for In Vivo Applications and Implications for Safety and Security.

Nanotechnology, the multidisciplinary field based on the exploitation of the unique physicochemical properties of nanoparticles (NPs) and nanoscale materials, has opened a new realm of possibilities for biological research and biomedical applications. The development and deployment of mRNA-NP vaccines for COVID-19, for example, may revolutionize vaccines and therapeutics. However, regulatory and ethical frameworks that protect the health and safety of the global community and environment are lagging, particularly for nanotechnology geared toward biological applications (ie, bionanotechnology). In this article, while not comprehensive, we attempt to illustrate the breadth and promise of bionanotechnology developments, and how they may present future safety and security challenges. Specifically, we address current advancements to streamline the development of engineered NPs for in vivo applications and provide discussion on nano-bio interactions, NP in vivo delivery, nanoenhancement of human performance, nanomedicine, and the impacts of NPs on human health and the environment.

Pearlescent Mica-Doped Alginate as a Stable, Vibrant Medium for Two-Dimensional and Three-Dimensional Art.

Emergent technologies are driving forces in the development of innovative art media that progress the field of modern art. Recently, artists have capitalized on the versatility of a new technology to create, restore, and modify art: additive manufacturing or three-dimensional (3D) printing. Additively manufactured art relies heavily on plastic-based materials, which typically require high heat to induce melting for workability. The necessity for heat limits plastic media to dedicated 3D printers. In contrast, biologically derived polymers such as polysaccharides used to create "bioinks" often do not require heating the material for workability, broadening the types of techniques available for printing. Here, we detail the formulation of a bioink consisting of mica pigments suspended in alginate as a new, vibrant art medium for 2D and 3D compositions. The properties that make alginate an ideal colorant binder are detailed: low cost with wide availability, nontoxicity and biocompatibility, minimal color, and an array of attractive physicochemical properties that offer workability and processing into 2D and 3D structures. Further, the chemical composition, morphology, and dispersibility of an array of mica pigment additives are characterized in detail as they pertain to the quality of an art medium. Alginate-based media with eight mica colors were formulated, where mica addition resulted in vibrantly colored inks with moderate hiding power and coverage of substrates necessary for 2D printing with thin horizontal and vertical lines. The utility of the media is demonstrated via the generation of 2D and 3D vibrant structures.

Polysaccharide-based liquid storage and transport media for non-refrigerated preservation of bacterial pathogens.

The preservation of biological samples for an extended time period of days to weeks after initial collection is important for the identification, screening, and characterization of bacterial pathogens. Traditionally, preservation relies on cold-chain infrastructure; however, in many situations this is impractical or not possible. Thus, our goal was to develop alternative bacterial sample preservation and transport media that are effective without refrigeration or external instrumentation. The viability, nucleic acid stability, and protein stability of Bacillus anthracis Sterne 34F2, Francisella novicida U112, Staphylococcus aureus ATCC 43300, and Yersinia pestis KIM D27 (pgm-) was assessed for up to 28 days. Xanthan gum (XG) prepared in PBS with L-cysteine maintained more viable F. novicida U112 cells at elevated temperature (40°C) compared to commercial reagents and buffers. Viability was maintained for all four bacteria in XG with 0.9 mM L-cysteine across a temperature range of 22-40°C. Interestingly, increasing the concentration to 9 mM L-cysteine resulted in the rapid death of S. aureus. This could be advantageous when collecting samples in the built environment where there is the potential for Staphylococcus collection and stabilization rather than other organisms of interest. F. novicida and S. aureus DNA were stable for up to 45 days upon storage at 22°C or 40°C, and direct analysis by real-time qPCR, without DNA extraction, was possible in the XG formulations. XG was not compatible with proteomic analysis via LC-MS/MS due to the high amount of residual Xanthomonas campestris proteins present in XG. Our results demonstrate that polysaccharide-based formulations, specifically XG with L-cysteine, maintain bacterial viability and nucleic acid integrity for an array of both Gram-negative and Gram-positive bacteria across ambient and elevated temperatures.

Systematic determination of the relationship between nanoparticle core diameter and toxicity for a series of structurally analogous gold nanoparticles in zebrafish.

Predictive models for the impact of nanomaterials on biological systems remain elusive. Although there is agreement that physicochemical properties (particle diameter, shape, surface chemistry, and core material) influence toxicity, there are limited and often contradictory, data relating structure to toxicity, even for core diameter. Given the importance of size in determining nanoscale properties, we aimed to address this data gap by examining the biological effects of a defined series of gold nanoparticles (AuNPs) on zebrafish embryos. Five AuNPs samples with narrowly spaced core diameters (0.8-5.8 nm) were synthesized and functionalized with positively charged N,N,N-trimethylammonium ethanethiol (TMAT) ligands. We assessed the bioactivity of these NPs in a high-throughput developmental zebrafish assay at eight concentrations (0.5-50 µg/mL) and observed core diameter-dependent bioactivity. The smaller diameter AuNPs were the most toxic when expressing exposures based on an equal mass. However, when expressing exposures based on total surface area, toxicity was independent of the core diameter. When holding the number of nanoparticles per volume constant (at 6.71 × 1013/mL) in the exposure medium across AuNPs diameters, only the 5.8 nm AuNPs exhibited toxic effects. Under these exposure conditions, the uptake of AuNPs in zebrafish was only weakly associated with core diameter, suggesting that differential uptake of TMAT-AuNPs was not responsible for toxicity associated with the 5.8 nm core diameter. Our results indicate that larger NPs may be the most toxic on a per particle basis and highlight the importance of using particle number and surface area, in addition to mass, when evaluating the size-dependent bioactivity of NPs.

Chemically Active, Porous 3D-Printed Thermoplastic Composites.

Metal-organic frameworks (MOFs) exhibit exceptional properties and are widely investigated because of their structural and functional versatility relevant to catalysis, separations, and sensing applications. However, their commercial or large-scale application is often limited by their powder forms which make integration into devices challenging. Here, we report the production of MOF-thermoplastic polymer composites in well-defined and customizable forms and with complex internal structural features accessed via a standard three-dimensional (3D) printer. MOFs (zeolitic imidazolate framework; ZIF-8) were incorporated homogeneously into both poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) matrices at high loadings (up to 50% by mass), extruded into filaments, and utilized for on-demand access to 3D structures by fused deposition modeling. Printed, rigid PLA/MOF composites display a large surface area (SAavg = 531 m2 g-1) and hierarchical pore features, whereas flexible TPU/MOF composites achieve a high surface area (SAavg = 706 m2 g-1) by employing a simple method developed to expose obstructed micropores postprinting. Critically, embedded particles in the plastic matrices retain their ability to participate in chemical interactions characteristic of the parent framework. The fabrication strategies were extended to other MOFs and illustrate the potential of 3D printing to create unique porous and high surface area chemically active structures.

Single-Step Synthesis of Small, Azide-Functionalized Gold Nanoparticles: Versatile, Water-Dispersible Reagents for Click Chemistry.

Nanoparticles possessing functional groups that can be readily conjugated (e.g., through click chemistry) are important precursors for the preparation of customized nanohybrid products. Such nanoparticles, if they are stable against agglomeration, are easily dispersible and have well-defined surface chemistry and size. As click-ready reagents, they can be stored until their time of use and then simply dispersed and reacted with an appropriate substrate. Gold nanoparticles (AuNPs) are excellent candidates for this purpose, and some clickable gold nanoparticles have been developed; however, AuNPs for use in aqueous systems are often prepared through difficult multistep processes and/or can be poorly dispersible in water. Here we report a single-step synthesis of clickable, water-dispersible AuNPs. The synthesis yields uniform, 3.5 nm diameter cores coated with a well-defined molecular ligand shell that makes the AuNPs stable and dispersible in water. The AuNP mixed ligand shell consists of hydroxyl-terminated ethylene glycol-based ligands to promote dispersion in water and a small number of azide-terminated ligands that readily undergo click reactions with alkynes. The use of a mesofluidic reactor affords fine control over the core size and ligand shell composition and ensures reproducible results (e.g., less than 0.1 nm variation in core diameter between batches). The purified reagents were successfully coupled to a variety of alkyne-containing substrates using both Cu-catalyzed and strain-promoted click reactions. Particle size, morphology, stability, and surface composition were thoroughly characterized using small-angle X-ray scattering, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis, and 1H NMR before and after the click reactions. Both the parent nanoparticles and their click chemistry products are stable during storage and remained dispersible for over a year in water, suggesting their potential for environmental, biological, and biomedical applications.

Direct Functionalization of an Acid-Terminated Nanodiamond with Azide: Enabling Access to 4-Substituted-1,2,3-Triazole-Functionalized Particles.

Azides on the periphery of nanodiamond materials (ND) are of great utility because they have been shown to undergo Cu-catalyzed and Cu-free cycloaddition reactions with structurally diverse alkynes, affording particles tailored for applications in biology and materials science. However, current methods employed to access ND featuring azide groups typically require either harsh pretreatment procedures or multiple synthesis steps and use surface linking groups that may be susceptible to undesirable cleavage. Here we demonstrate an alternative single-step approach to producing linker-free, azide-functionalized ND. Our method was applied to low-cost, detonation-derived ND powders where surface carbonyl groups undergo silver-mediated decarboxylation and radical substitution with azide. ND with directly grafted azide groups were then treated with a variety of aliphatic, aromatic, and fluorescent alkynes to afford 1-(ND)-4-substituted-1,2,3-triazole materials under standard copper-catalyzed cycloaddition conditions. Surface modification steps were verified by characteristic infrared absorptions and elemental analyses. High loadings of triazole surface groups (up to 0.85 mmol g-1) were obtained as determined from thermogravimetric analysis. The azidation procedure disclosed is envisioned to become a valuable initial transformation in numerous future applications of ND.

2,6-Diiminopiperidin-1-ol: an overlooked motif relevant to uranyl and transition metal binding on poly(amidoxime) adsorbents.

Glutardiamidoxime, a structural motif on sorbents used in uranium extraction from seawater, was discovered to cyclize in situ at room temperature to 2,6-diimino-piperidin-1-ol in the presence of uranyl nitrate. The new diimino motif was also generated when exposed to competing transition metals Cu(ii) and Ni(ii). Multinuclear µ-O bridged U(vi), Cu(ii), and Ni(ii) complexes featuring bound diimino ligands were isolated.

Influence of Ligand Shell Composition upon Interparticle Interactions in Multifunctional Nanoparticles.

The interactions of nanoparticles with biomolecules, surfaces, or other nanostructures are dictated by the nanoparticle's surface chemistry. Thus, far, shortcomings of syntheses of nanoparticles with defined ligand shell architectures have limited our ability to understand how changes in their surface composition influence reactivity and assembly. We report new synthetic approaches to systematically control the number (polyvalency), length, and steric interactions of omega-functionalized (targeting) ligands within an otherwise passivating (diluent) ligand shell. A mesofluidic reactor was used to prepare nanoparticles with the same core diameter for each of the designed ligand architectures. When the targeting ligands are malonamide groups, the nanoparticles assemble via cross-linking in the presence of trivalent lanthanides. We examined the influence of ligand composition on assembly by monitoring the differences in optical properties of the cross-linked and free nanoparticles. Infrared spectroscopy, electron microscopy, and solution small-angle X-ray scattering provided additional insight into the assembly behavior. Lower (less than 33%) malonamide ligand densities (where the binding group extends beyond the periphery of diluent ethylene glycol ligands) produce the strongest optical responses and largest assemblies. Surprisingly, nanoparticles containing a higher surface number of targeting ligand did not produce an optical response or assemble, underscoring the importance of an informed mixed ligand strategy for highest nanoparticle performance.