RESUMEN

Rheological evidence is provided demonstrating that covalent grafting of monodisperse isotactic poly(L-leucine) branches onto linear hyaluronan (HA) polysaccharide chains yields comb-branched HA chains that self-assemble into long-lived physical networks in aqueous solutions driven by hydrophobic interactions between poly(L-leucine) chains. This is in stark contrast to native (unmodified) HA solutions which exhibit no tendency to form long-lived physical networks.

RESUMEN

Here we generate silk-elastin-like protein (SELP) polymeric nanoparticles and demonstrate precise control over their dimensions using an electrospray differential mobility analyzer (ES-DMA). Electrospray produces droplets encompassing several polymer strands. Evaporation ensues, leading polymer strands to accumulate at the droplet interface, forming a hollow nanoparticle. The resulting nanoparticle size distributions, which govern particle yield, depend on buffer concentration to the -1/3 power, polymer concentration to the 1/3 power, and ratio of silk-to-elastin blocks. Three recombinantly tuned ratios of 8:16, 4:8, and 4:16, respectively named SELP-815K, SELP-47K, and SELP-415K, are employed, with the latter ratio resulting in a thinner shell and larger diameter for the nanoparticles than the former. The DMA narrows the size distribution by electrostatically classifying the aerosolized nanoparticles. These highly uniform nanoparticles have variations of 1.2 and 1.4 nm for 24.0 and 36.0 nm particles, respectively. Transmission electron microscopy reveals the nanoparticles to be faceted, as a buckling instability releases compression energy arising from evaporation after the shell has formed by bending it. A thermodynamic equilibrium exists between compression and bending energies, where the facet length is half the particle diameter, in agreement with experiments. Rod-like particles also formed from polymer-stabilized filaments when the viscous length exceeds the jet radius at higher solution viscosities. The unusual uniformity in composition and dimension indicates the potential of these nanoparticles to deliver bioactive and imaging agents.

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RESUMEN

Quantitative techniques are essential to analyze the structure of soft multicomponent nanobioclusters. Here, we combine electrospray differential mobility analysis (ES-DMA), which rapidly measures the size of the entire cluster, with transmission electron microscopy (TEM), which detects the hard components, to determine the presence and composition of the softer components. Coupling analysis of TEM and ES-DMA derived data requires the creation and use of analytical models to determine the size and number of constituents in nanoparticle complexes from the difference between the two measurements. Previous ES-DMA analyses have been limited to clusters of identical spherical particles. Here, we dramatically extend the ES-DMA analysis framework to accommodate more challenging geometries, including protein corona-coated nanorods, clusters composed of heterogeneously sized nanospheres, and nanobioclusters composed of both nanospheres and nanorods. The latter is critical to determining the number of quantum dots attached to lambda (λ) phage, a key element of a rapid method to detect bacterial pathogens in environmental and clinical samples.

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