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1. Quantifying and controlling bond multivalency for advanced nanoparticle targeting to cells

   https://doi.org/10.1186/s40580-021-00288-1  

   Makhani, Elliot Y. ; Zhang, Ailin ; Haun, Jered B. ( November 2021 , Nano Convergence)

   Nanoparticles have drawn intense interest as delivery agents for diagnosing and treating various cancers. Much of the early success was driven by passive targeting mechanisms such as the enhanced permeability and retention (EPR) effect, but this has failed to lead to the expected clinical successes. Active targeting involves binding interactions between the nanoparticle and cancer cells, which promotes tumor cell-specific accumulation and internalization. Furthermore, nanoparticles are large enough to facilitate multiple bond formation, which can improve adhesive properties substantially in comparison to the single bond case. While multivalent binding is universally believed to be an attribute of nanoparticles, it is a complex process that is still poorly understood and difficult to control. In this review, we will first discuss experimental studies that have elucidated roles for parameters such as nanoparticle size and shape, targeting ligand and target receptor densities, and monovalent binding kinetics on multivalent nanoparticle adhesion efficiency and cellular internalization. Although such experimental studies are very insightful, information is limited and confounded by numerous differences across experimental systems. Thus, we focus the second part of the review on theoretical aspects of binding, including kinetics, biomechanics, and transport physics. Finally, we discuss various computational and simulation studies of nanoparticlemore »adhesion, including advanced treatments that compare directly to experimental results. Future work will ideally continue to combine experimental data and advanced computational studies to extend our knowledge of multivalent adhesion, as well as design the most powerful nanoparticle-based agents to treat cancer.

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2. Wall teichoic acids govern cationic gold nanoparticle interaction with Gram-positive bacterial cell walls

   https://doi.org/10.1039/C9SC05436G  

   Caudill, Emily R. ; Hernandez, Rodrigo Tapia ; Johnson, Kyle P. ; O'Rourke, James T. ; Zhu, Lingchao ; Haynes, Christy L. ; Feng, Z. Vivian ; Pedersen, Joel A. ( January 2020 , Chemical Science)

   Molecular-level understanding of nanomaterial interactions with bacterial cell surfaces can facilitate design of antimicrobial and antifouling surfaces and inform assessment of potential consequences of nanomaterial release into the environment. Here, we investigate the interaction of cationic nanoparticles with the main surface components of Gram-positive bacteria: peptidoglycan and teichoic acids. We employed intact cells and isolated cell walls from wild type Bacillus subtilis and two mutant strains differing in wall teichoic acid composition to investigate interaction with gold nanoparticles functionalized with cationic, branched polyethylenimine. We quantified nanoparticle association with intact cells by flow cytometry and determined sites of interaction by solid-state 31 P- and 13 C-NMR spectroscopy. We find that wall teichoic acid structure and composition were important determinants for the extent of interaction with cationic gold nanoparticles. The nanoparticles interacted more with wall teichoic acids from the wild type and mutant lacking glucose in its wall teichoic acids than those from the mutant having wall teichoic acids lacking alanine and exhibiting more restricted molecular motion. Our experimental evidence supports the interpretation that electrostatic forces contributed to nanoparticle–cell interactions and that the accessibility of negatively charged moieties in teichoic acid chains influences the degree of interaction. The approaches employed in thismore »study can be applied to engineered nanomaterials differing in core composition, shape, or surface functional groups as well as to other types of bacteria to elucidate the influence of nanoparticle and cell surface properties on interactions with Gram-positive bacteria.« less
3. The impact of habitat fragmentation on domatia-dwelling mites and a mite-plant-fungus tritrophic interaction

   https://doi.org/10.1007/s10980-022-01529-2  

   Graham, Carolyn D. K. ; Warneke, Christopher R. ; Weber, Marjorie ; Brudvig, Lars A. ( October 2022 , Landscape Ecology)

   Habitat fragmentation is a leading threat to biodiversity, yet the impacts of fragmentation on most taxa, let alone interactions among those taxa, remain largely unknown.

   We studied how three consequences of fragmentation—reduced patch connectivity, altered patch shape, and edge proximity—impact plant-dwelling mite communities and mite-plant-fungus interactions within a large-scale habitat fragmentation experiment.

   We sampled mite communities from the leaves ofQuercus nigra(a plant species that has foliar domatia which harbor fungivorous and predacious mites) near and far from edge within fragments of varying edge-to-area ratio (shape) and connectivity via corridors. We also performed a mite-exclusion experiment across these fragmentation treatments to test the effects of mite presence and fungal hyphal abundance on leaf surfaces.

   Habitat edges influenced the abundance and richness of leaf-dwelling mites; plants closer to the edge had higher mite abundance and species richness. Likewise, hyphal counts were higher on leaves near patch edges. Despite both mite and fungal abundance being higher at patch edges, leaf hyphal counts were not impacted by mite abundance on those leaves. Neither patch shape nor connectivity influenced mite abundance, mite species richness, or the influence of mites on leaf surface fungal abundance.

   Our results suggest that mites and foliar fungi may bemore »independently affected by edge-structured environmental gradients, like temperature, rather than trophic effects. We demonstrate that large-scale habitat fragmentation and particularly edge effects can have impacts on multiple levels of microscopic communities, even in the absence of cascading trophic effects.

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4. Directed propulsion of spherical particles along three dimensional helical trajectories

   https://doi.org/10.1038/s41467-019-10579-1  

   Lee, Jin Gyun ; Brooks, Allan M. ; Shelton, William A. ; Bishop, Kyle J. M. ; Bharti, Bhuvnesh ( June 2019 , Nature Communications)

   Active colloids are a class of microparticles that ‘swim’ through fluids by breaking the symmetry of the force distribution on their surfaces. Our ability to direct these particles along complex trajectories in three-dimensional (3D) space requires strategies to encode the desired forces and torques at the single particle level. Here, we show that spherical colloids with metal patches of low symmetry self-propel along non-linear 3D trajectories when powered remotely by an alternating current (AC) electric field. In particular, particles with triangular patches of approximate mirror symmetry trace helical paths along the axis of the field. We demonstrate that the speed and shape of the particle’s trajectory can be tuned by the applied field strength and the patch geometry. We show that helical motion can enhance particle transport through porous materials with implications for the design of microrobots that can navigate complex environments.
5. Nanoparticles are linked to polar lipids in xylem sap of temperate angiosperm species

   https://doi.org/10.1093/treephys/tpac054  

   Guan, Xinyi ; Schenk, H. Jochen ; Roth, Mary R. ; Welti, Ruth ; Werner, Julia ; Kaack, Lucian ; Trabi, Christophe L. ; Jansen, Steven ; Holtta, ed., Teemu ( May 2022 , Tree Physiology)

   In previous research, xylem sap of angiosperms has been found to include low concentrations of nanoparticles and polar lipids. A major goal of this study was to test predictions arising from the hypothesis that the nanoparticles consist largely of polar lipids from the original cell content of vessel elements. These predictions included that polar lipid and nanoparticle concentrations would be correlated, that they both do not pass through pit membranes and that they do not vary seasonally because they originate from living vessel element cells. We collected xylem sap of six temperate angiosperm species over the whole year to consider seasonal variation. Concentrations of nanoparticles and lipids in xylem sap and contamination control samples were measured with a NanoSight device and mass spectrometry. We found that the concentration of nanoparticles and polar lipids was (i) diluted when an increasing amount of sap was extracted, (ii) significantly correlated to each other for three species, (iii) affected by vessel anatomy, (iv) very low and largely different in chemical composition from contamination controls and (v) hardly variable among seasons. Moreover, there was a minor freezing–thawing effect with respect to nanoparticle amount and size. Xylem sap lipids included polar galactolipids and phospholipids inmore »all species and neutral triacylglycerols in two species. These findings support the predictions and, by implication, the underlying hypothesis that nanoparticles in xylem sap consist of polar lipids from the original cell content of living vessel element cells. Further research is needed to examine the formation and stability of nanoparticles concerning lipid composition and multiphase interactions among gas, liquid and solid phases in xylem conduits of living plants.

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