Controlling the growth of "ionic" nanoparticle supracrystals

Dimensions and quality of supracrystals self-assembling from oppositely charged nanoparticles (NPs) can be controlled by changing the relative nanoparticle concentrations, NP polydispersity, and pH. In particular, excess nanoparticles of either polarity terminate the self-assembly process at desired stages by forming charged, stabilizing shells around the growing aggregates. In this way, average supracrystal sizes can be varied from several micrometers down to tens of nanometers. While larger crystals precipitate from the growing solution, those smaller than ca. 400 nm are soluble. The experimentally observed threshold size for solubility agrees with arguments based on the DLVO theory

Studying the thermodynamics of surface reactions on nanoparticles by electrostatic titrations

For nanoparticles coated with binary SAMs (m-SAM NPs) containing charged or ionizable molecules, the relative equilibrium constants and the difference in the free energies of absorption of the m-SAM's components can be obtained in a straightforward way by titrating such NPs with oppositely charged nanoparticle "standards" until precipitation at the point of overall electroneutrality

Electrostatically "Patchy" coatings via cooperative adsorption of charged nanoparticles

Solutions containing oppositely charged nanoparticles (NIPS) deposit "patchy" coatings of alternating charge distribution on various types of materials, including polymers, elastomers, and semiconductors. Surface adsorption of the NPs is driven by cooperative electrostatic interactions and does not require chemical ligation or layer-by-layer schemes. The composition and the quality of the coatings can be regulated by the types, the charges, and the relative concentrations of the NPs used and by the pH. Dense coatings form on flat, curvilinear, or micropatterned surfaces, are stable against common chemicals for prolonged periods of time, and can be used in applications ranging from bacterial protection to plasmonics

Ionic-like behavior of oppositely charged nanoparticles

Mixtures of oppositely charged nanoparticles of various sizes and charge ratios precipitate only at the point of electroneutrality. This phenomenonspecific to the nanoscale and reminiscent of threshold precipitation of ionsis a consequence of the formation of core-and-shell nanoparticle aggregates, in which the shells are composed of like-charged particles and are stabilized by efficient electrostatic screening

Modeling of electrodynamic interactions between metal nanoparticles aggregated by electrostatic interactions into closely-packed clusters

This paper is a theoretical and experimental study of the optical properties of binary aqueous suspensions containing metal nanoparticles (NPs) coated with charged organics. If all nanoparticles bear charges of the same polarity, the NPs do not aggregate, and the solutions are stable. Under these circumstances, optical response of the mixture is a linear combination of the optical responses of the individual components. In contrast, when the NPs are oppositely charged, they aggregate into clusters, whose optical properties cannot be understood without taking into account electrodynamic coupling between the constituent NPs. To model such aggregates, we present two theoretical approaches: (i) an exact analytical model accounting for the granularity of the NPs and (ii) an approximation, in which the aggregates are represented as spherosymmetric core-and-shells. Both models reproduce optical spectra recorded experimentally and give physically reasonable estimates of the aggregates' internal structure and composition

Ruthenium p-cymene iminophosphonamide complexes: Activation under basic conditions and transfer hydrogenation catalysis

International audienceComplex [(η6-Cym)RuCl(NPN)] Cym = p-cymene; NPN = (pTolN)2PPh2 (1) yields a thermally sensitive hydride derivative [(η6-Cym)RuH(NPN)] (2) by reaction with iPrOH in the presence of a strong base, via an observable isopropoxide intermediate [(η6-Cym)Ru(OiPr)(NPN)] (3), or with NaBHEt3 in toluene. Partial conversion also occurs in iPrOH in the absence of base. 2 is stabilized by dihydrogen bonding with isopropyl alcohol, but attempts to isolate it induce isomerization by hydride migration to a ring CH position to yield a 16-electron cyclohexadienyl derivative [η5-p-C6H5(Me)(iPr)Ru(NPN)], which has been crystallographically characterized as a disordered mixture of two regioisomers (4/4′). Complex 2 is able to release H2 upon treatment with medium strength proton donors (fluorinated alcohols), but also slowly with iPrOH. 2 is an active catalyst for the transfer hydrogenation of acetophenone to phenylethanol in isopropyl alcohol. The catalytic transformation is first order in acetophenone and first order in catalyst, with k = 117 ± 10 m–1 h–1 at 40 °C. The temperature dependence of the rate constant (25–80 °C) gave the activation parameters ΔH‡ = 9.6 ± 1.3 kcal mol–1 and ΔS‡ = –31 ± 4 cal mol–1 K–1. DFT calculations have validated the slow isomerization of 2 to 4/4′ (high energy TS), the preference of the cyclohexadienyl system for 4/4′ relative to the other isomers 4Me and 4iPr, where the hydride has migrated to the CMe or CiPr position, and suggest that the hydrogen transfer mechanism involves outer sphere hydride transfer to the ketone substrate with H-bonding assistance of isopropyl alcohol to yield a σ complex intermediate [(η6-Cym)Ru+(NPN)H-C(Me)(Ph)O–]

Oncolytic therapy with recombinant vaccinia viruses targeting the interleukin-15 pathway elicits a synergistic response

We developed recombinant variants of oncolytic vaccinia virus LIVP strain expressing interleukin-15 (IL-15) or its receptor subunit alpha (IL-15Rα) to stimulate IL-15-dependent immune cells. We evaluated their oncolytic activity either alone or in combination with each other in vitro and in vivo using the murine CT26 colon carcinoma and 4T1 breast carcinoma models. We demonstrated that the admixture of these recombinant variants could promote the generation of the IL-15/IL-15Rα complex. In vitro studies indicated that 4T1 breast cancer cells were more susceptible to the developed recombinant viruses. In vivo studies showed significant survival benefits and tumor regression in 4T1 breast cancer syngeneic mice that received a combination of LIVP-IL15-RFP with LIVP-IL15Ra-RFP. Histological analysis showed recruited lymphocytes at the tumor region, while no harmful effects to the liver or spleen of the animals were detected. Evaluating tumor-infiltrated lymphocytes represented profound activation of cytotoxic T cells and macrophages in mice receiving combination therapy. Thus, our experiments showed superior oncolytic effectiveness of simultaneous injection of LIVP-IL15-RFP and LIVP-IL15Ra-RFP in breast cancer-bearing mice. The combined therapy by these recombinant variants represents a potent and versatile approach for developing new immunotherapies for breast cancer