Small gold nanoparticles presenting linear and looped Cilengitide analogues as radiosensitizers of cells expressing α<Subscript>ν</Subscript>β<Subscript>3</Subscript> integrin

This work uses linear and looped RGDfV sequences attached to the surface of small (1.8 nm in diameter) gold nanoparticles (AuNPs) to enhance the radiosensitizating effects of Cilengitide, a cyclic RGDf (NMe)V pentapeptide that targets α_vβ₃ integrin which is overexpressed in certain cancers. Following synthesis and purification, the AuNPs were evaluated in vitro against HUVEC, H460, and MCF7 cells in clonogenic assays using a ¹³⁷Cs irradiator. Untargeted AuNPs induced no significant dose enhancement factors (DEFs) in any of the cell types when compared to radiation treatment alone, whereas all evaluated AuNPs functionalized with targeting peptides performed at least as well as controls (irradiation after Cilengitide treatment). The observed DEFs also suggest that cyclizing the linear peptides into more spatially constrained, looped structures may facilitate target binding. These greater dose enhancements merit future in vivo studies of drug-AuNP conjugates to assess the ability of the nanostructures to provide an improved therapeutic benefit over treatment with drug candidates and radiation alone.

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Structures and energetics of electrosprayed uracil(n)Ca2+ clusters (n = 14-4) in the gas phase

Clusters of uracil (U) about a calcium dication, U(n)Ca(2+) (n = 14-4), have been studied in the gas phase by both experimental and theoretical methods. Temperature dependent blackbody infrared radiative dissociation (BIRD) experiments were performed on U(n)Ca(2+) clusters with n = 14-5 and the observed Arrhenius parameters are reported here. Master equation modeling of the BIRD kinetics data was carried out to determine threshold dissociation energies. Initial geometry calculations were performed using the B3LYP density functional and 3-21G(d) basis set. A sample of ten conformations per cluster was obtained through a simulated annealing study. These structures were optimized using B3LYP/6-31G(d) level of theory. Fragment-based hybrid many body interaction (HMBI) MP2/6-311++G(2df,2p)/Amoeba calculations were performed on representative conformations to determine theoretical binding energies. Results were examined in relation to cluster size (n). A significant increase in the energy required to remove uracil from U(6)Ca(2+) when compared to larger clusters supports previous reports that the calcium ion is coordinated by six uracil molecules in the formation of an inner shell. For clusters larger than n = 6, an odd-even alternation in threshold dissociation energies was observed, suggesting that the outer shell uracil molecules bind as dimers to the inner core. Proposed binding schemes are presented. Multiple structures of U(5)Ca(2+) are suggested as being present in the gas phase where the fifth uracil may be either part of the first or second solvation shell.     

Gas sorption and luminescence properties of a terbium(III)-phosphine oxide coordination material with two-dimensional pore topology

The structure, stability, gas sorption properties and luminescence behaviour of a new lanthanide-phosphine oxide coordination material are reported. The polymer PCM-15 is based on Tb(III) and tris(p-carboxylated) triphenylphosphine oxide and has a 5,5-connected net topology. It exhibits an infinite three-dimensional structure that incorporates an open, two-dimensional pore structure. The material is thermally robust and remains crystalline under high vacuum at 150 °C. When desolvated, the solid has a CO(2) BET surface area of 1187 m(2) g(-1) and shows the highest reported uptake of both O(2) and H(2) at 77 K and 1 bar for a lanthanide-based coordination polymer. Isolated Tb(III) centres in the as-synthesized polymer exhibit moderate photoluminescence. However, upon removal of coordinated OH(2) ligands, the luminescence intensity was found to approximately double; this process was reversible. Thus, the Tb(III) centre was used as a probe to detect directly the desolvation and resolvation of the polymer.     

Hierarchical freezing in a lattice model

A certain two-dimensional lattice model with nearest and next-nearest neighbor interactions is known to have a limit-periodic ground state. We show that during a slow quench from the high temperature, disordered phase, the ground state emerges through an infinite sequence of phase transitions. We define appropriate order parameters and show that the transitions are related by renormalizations of the temperature scale. As the temperature is decreased, sublattices with increasingly large lattice constants become ordered. A rapid quench results in a glasslike state due to kinetic barriers created by simultaneous freezing on sublattices with different lattice constants.     

Suppression of parasitic lasing in high energy, high repetition rate Ti:sapphire laser amplifiers

Transverse parasitic lasing is well known for limiting the signal gain and the pulse energy that can be extracted from Ti:sapphire petawatt amplifiers. We have developed a technique for suppressing these parasitic lasing modes based on perfect refractive index-matching liquid doped with a broad-bandwidth absorber to suppress the transverse lasing while ensuring proper heat removal from the Ti:sapphire crystal. The 800 nm laser output with a bandwidth of 41 nm (FWHM) and peak energy of 22.7 J at a repetition rate of 1 Hz is demonstrated.     

Characterization of highly unusual NH+-O hydrogen bonding to ester ether oxygen atoms through spectroscopic and computational studies

We characterize a highly unusual, charged NH-O hydrogen bond formed within esters of 8-(dimethylamino)naphthalen-1-ol in which an ammonium ion serves as an intramolecular hydrogen bond donor to spatially proximate ester ether oxygen atoms. Infrared spectroscopic analysis of the ester carbonyl frequencies demonstrates significant blue-shifting when ether hydrogen bonding is possible, in stark contrast to the more commonly observed red shift that occurs upon hydrogen bonding to the ester carbonyl oxygen. The intrinsic behavior of the linkage (i.e., in which counterions and solvent effects are eliminated) is provided by vibrational predissociation spectroscopy of the isolated gas-phase cations complexed with weakly bound D(2) molecules.     

Nonclassical oxygen atom transfer reactions of oxomolybdenum(VI) bis(catecholate)

Mechanistic studies indicate that the oxomolybdenum(vi) bis(3,5-di-tert-butylcatecholate) fragment deoxygenates pyridine-N-oxides in a reaction where the oxygen is delivered to molybdenum but the electrons for substrate reduction are drawn from the bound catecholate ligands, forming 3,5-di-tert-butyl-1,2-benzoquinone.     

Micellization and Adsorption to Carbon Black of Polyisobutylene-Based Ionic Liquids

Ionic liquid-terminated polyisobutylene (PIB-IL) dispersants suitable for stabilization of carbonaceous deposits found in automotive lubricating oils were derived by the quaternization of tertiary amines (1-methyl-imidazole, pyridine, and isoquinoline) with primary bromide-terminated PIB. Characterization of PIB intermediate and PIB-IL dispersants was carried out by nuclear magnetic resonance, gel-permeation chromatography, thermogravimetric analysis (TGA), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and differential scanning calorimetry. PIB-IL micellization in dodecane and characteristics thereof (hydrodynamic radius, aggregation number, and critical micelle concentration) were investigated by static (SLS) and dynamic light scattering; whereupon, the self-association of PIB-IL was found to be highly sensitive to anion hydrophobicity. Qualitative adsorption of PIB-IL onto carbon black was confirmed by Fourier transform infrared and TGA measurements. Using Langmuir adsorption studies, the affinity for and adsorption to carbon black of PIB-IL were characterized. PIB-IL adsorption onto carbon black occurred via cation–π interactions and was identified to be highly dependent on the molar volume of the cation and independent of the anion. From the parameters obtained by the Langmuir adsorption isotherms, the spatial arrangement of PIB-IL on the carbon black surface was elucidated, in which all adsorbed PIB-IL were determined to exist in the elongated brush regime. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 280–299     

Quantum Dots Luminescence Collection Enhancement and Nanoscopy by Dielectric Microspheres

In recent years, dielectric microspheres have been used in conjunction with optical microscopes to beat the diffraction limit and to obtain superresolution imaging. The use of microspheres on quantum dots (QDs) is investigated, for the first time, to enhance the light coupling efficiency. The enhancement of the QD luminescence collection in terms of extraction and directionality is demonstrated, as well as the enhancement of spatial resolution. In particular, it is found that a dielectric microsphere, placed on top of an epitaxial QD, increases the collected radiant energy by about a factor of 42, when a low numerical aperture objective is used. Moreover, if two or more QDs are present below the microsphere, the modification of the far field emission pattern allows selective collection of the luminescence from a single QD by simply changing the collection angle. Dielectric microspheres present a simple and efficient tool to improve the QD spectroscopy, and potentially QD-based devices.