PEGylation of metal oxide nanoparticles is the common approach to improve their biocompatibility and in vivo circulation time. In this work, we present a combined experimental and theoretical study to determine the operating condition that guarantee very high grafting densities, which are desirable in any biomedical application. Moreover, we present an insightful conformational analysis spanning different coverage regimes and increasing polymer chain lengths. Based on 13C NMR measurements and molecular dynamics simulations, we show that classical and popular models of polymer conformation on surfaces fail in determining the mushroom-to-brush transition point and prove that it actually takes place only at rather high grafting density values.

No abstract

As a model radio-photodynamic therapy (RPDT) agent, we developed a multicomponent nanomaterial by anchoring conjugated chromophores on the surface of scintillating chrysotile nanotubes. Its ultimate composition makes the system a scintillation-activated photosensitizer for the singlet oxygen production. This nanomaterial shows a remarkable ability to enhance the production of singlet oxygen in an aqueous environment, under X-ray irradiation, boosting its production by almost 1 order of magnitude. Its efficiency as a coadjutant for radiotherapy has been tested in vitro , showing a striking efficacy in enhancing both the prompt cytotoxicity of the ionizing radiation and the long-term cytotoxicity given by radiation-activated apoptosis. Notably, the beneficial activity of the RPDT agent is prominent at low levels of delivered doses comparable to the one employed in clinical treatments. This opens the possibility of effectively reducing the therapy exposure and consequently undesired collateral effects due to prolonged exposure of patients to high-energy radiation.

Nanocrystals (NCs) surface characterization is a fundamental step for understanding the physical and chemical phenomena involved at the nanoscale. Surface energy and chemistry depend on particle size and composition, and, in turn, determine the interaction of NCs with the surrounding environment, their properties and stability, and the feasibility of nanocomposites. This work aims at extracting more information on the surface of different titanium dioxide polymorphs using H-TD-NMR of water. Taking advantage of the interaction between water molecules and titanium dioxide NCs, it is possible to correlate the proton transverse relaxation times ( T) as the function of the concentration and the specific surface area (δ· C) and use it as an indicator of the crystal phase. Examples of three different crystals phase, rutile, anatase, and brookite, have been finely characterized and their behavior in water solution have been studied with TD-NMR. The results show a linear correlation between relaxivity ( R) and their concentration C. The resulting slopes, after normalization for the specific surface, represent the surface/water interaction and range from 1.28 g m s of 50 nm rutile nanocrystals to 0.52 for similar sized brookite. Even higher slopes (1.85) characterize smaller rutile NCs, in qualitative accordance with the trends of surface energy. Thanks to proton relaxation phenomena that occur at the NCs surface, it is possible to differentiate the crystal phase and the specific surface area of titanium dioxide polymorphs in water solution.

Reversible addition-fragmentation chain transfer (RAFT) polymerization of 2,3-dimethyl-1,3-butadiene (DMB) in solution and on the surface of silica nanoparticles was investigated and PDMB-grafted silica nanoparticles (PDMB-g-SiO 2 NPs) with different chain densities and molecular weights were prepared. The kinetic studies of DMB polymerization mediated by silica anchored RAFT agents at different graft densities were investigated and compared to the polymerization mediated by the corresponding free RAFT agent. The PDMB-g-SiO 2 NPs were cured to prepare rubbery films and obtain matrix-free nanocomposites, which exhibited a good dispersion of silica nanoparticles and improved mechanical properties compared to the unfilled crosslinked rubber.Additional supporting information may be found in the online version of this article.