This study presents a series of light-harvesting materials, where multiple chromophores are organised into host-guest silica-micelle structures at specific locations by means of self-assembly strategies. Binary and ternary mesoscopic antennae were realized, using organometallic complexes and organic dyes as energy transfer units and varying their content and localization to manipulate transfer rate and efficiency inside the materials. Steady-state and time-resolved UV–vis spectroscopy revealed that the three-dye systems show excitation energy cascade from intramicellar dyes to a silica-grafted acceptor, with transfer efficiencies of 20–24 % per step and overall light emission spanning the whole visible range. The two-dye system reaches analogous panchromatic response, featuring almost-white light emission and 47 % efficient transfer, by exploiting the blue-green dual emission of a metallosurfactant as energy donor inside the micellar template and the red emission of a rhodamine acceptor on the silica framework. Both systems show that control over the donor-acceptor distances can be achieved to a certain extent in complex mesoscopic materials and that a vast potential is available for transfer and colour tuning, and specific use of the materials as solid-state sensitisers.

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It is known that phenylboronic acid (PBA) can target tumor tissues by binding to sialic acid, a substrate overexpressed by cancer cells. This capability has previously been explored in the design of targeting diagnostic probes such as Gd- and 68Ga-DOTA-EN-PBA, two contrast agents for magnetic resonance imaging (MRI) and positron emission tomography (PET), respectively, whose potential has already been demonstrated through in vivo experiments. In addition to its high resolution, the intrinsic low sensitivity of MRI stimulates the search for more effective contrast agents, which, in the case of small-molecular probes, basically narrows down to either increased tumbling time of the entire molecule or elevated local concentration of the paramagnetic ions, both strategies resulting in enhanced relaxivity, and consequently, a higher MRI contrast. The latter strategy can be achieved by the design of multimeric GdIII complexes. Based on the monomeric PBA-containing probes described recently, herein, we report the synthesis and characterization of the dimeric analogues (GdIII-DOTA-EN)2-PBA and (GdIII-DOTA-EN)2F2PBA. The presence of two Gd ions in one molecule clearly contributes to the improved biological performance, as demonstrated by the relaxometric study and cell-binding investigations.

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Paramagnetic macrocycles functionalized with phenylboronic moieties have proven to be interesting for MRI applications based on their ability to recognize cancer cells and generate local contrast. However, full use of the potential of this class of compounds is hampered by laborious and inefficient synthetic and, especially, purification procedures. The amphiphilic character of water-soluble phenylboronates renders them difficult compounds to be prepared through conventional solution synthesis due to the tendency to aggregate and form adducts with other nucleophiles. The new strategy described herein exploits the advantage of solid-phase synthesis with the application of DEAM-PS resin for anchorage and the subsequent simplified derivatization of boronates. GdDOTA-EN-PBA and its fluorinated analogue GdDOTA-EN-F2PBA were synthesized in a much easier, faster and economically convenient way to achieve good yields and purity. Furthermore, the effect of electron-withdrawing fluorine atoms on the aromatic ring of the latter compound was investigated by comparing the physico-chemical properties of both compounds as well as their binding affinity towards melanoma cancer cells.

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This study presents a new design of light-harvesting antenna materials using two dyes organised into mesoporous silica: an iridium(III) complex and a BODIPY-derived surfactant that undergo Förster resonance energy transfer (FRET), acting, respectively, as donor and acceptor. The chemical structure of each dye determines the position taken within the micellar templates used for the synthesis of the silica host, which maintains mesopore order as shown by TEM imaging. Steady-state and time-resolved UV-visible spectroscopy revealed that incorporation of the iridium complex into the silica shields it from oxygen-induced quenching and allows a degree of control over the donor-acceptor distance, yielding FRET efficiencies from 24 to 76% and tuneable emission ranges. Such silica-based antennae show promising properties for the realisation of polychromatic sensitisers for photovoltaics and photocatalysis.

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Surface PEGylation of nanoparticles designed for biomedical applications is a common and straightforward way to stabilize the materials for in vivo administration and to increase their circulation time. This strategy becomes less trivial when MRI active porous nanomaterials are concerned as their function relies on water/proton-exchange between the pores and bulk water. Here we present a comprehensive study on the effects of PEGylation on the relaxometric properties of nanozeolite LTL (dimensions of 20 × 40 nm) ion-exchanged with paramagnetic GdIII ions. We evidence that as long as the surface grafting density of the PEG chains does not exceed the “mushroom” regime (conjugation of up to 6.2 wt % of PEG), Gd-LTL retains a remarkable longitudinal relaxivity (38 s–1 mM–1 at 7 T and 25 °C) as well as the pH-dependence of the longitudinal and transverse relaxation times. At higher PEG content, the more compact PEG layer (brush regime) limits proton/water diffusion and exchange between the interior of LTL and the bulk, with detrimental consequences on relaxivity. Furthermore, PEGylation of Gd-LTL dramatically decreases the leakage of toxic GdIII ions in biological media and in the presence of competing anions, which together with minimal cytotoxicity renders these materials promising probes for MRI applications.@en

Neutron activation is widely applied for thepreparation of radioactive isotopes to be used in imaging and/or therapy. The type of diagnostic/therapeutic agents varies fromsmall chelates coordinating radioactive metal ions to complexnanoparticulate systems. Design of these agents often relies onconjugation of certain organic functionalities that determine theirpharmacokinetics, biodistribution, targeting, and cell-penetratingabilities, or simply on tagging them with an optical label. Theconjugation chemistry at the surface of nanoparticles and theirfinal purification often require laborious procedures that becomeeven more troublesome when radioactive materials are involved.This study represents a thorough investigation on the effects ofneutron activation on the organic moieties of functionalizednanoparticles, with special focus on166Ho2O3particles conjugated with PEG-fluorescein and PEG-polyarginine motives.Spectroscopic and thermogravimetric analyses demonstrate only a limited degradation of PEG-fluorescein upon irradiation of theparticles up to 10 h using a thermal neutronflux of 5×1016m−2s−1. Cell experiments show that the polyarginine-basedmechanisms of membrane penetration remain unaltered after exposure of the functionalized particles to the mixedfield ofneutrons and gammas present during activation. This confirms that radiation damage on the PEG-polyarginines is minimal.Intrinsic radiations from166Ho do not seem to affect the integrity of conjugated organic material. Thesefindings open up a newperspective to simplify the procedures for the preparation of functionalized metal-based nanosystems that need to be activated byneutron irradiation in order to be applied for diagnostic and/or therapeutic purposes.@en