Aldo Arrais

Selective Anchoring of GdIII Chelates on the External Surface of Organo-Modified Mesoporous Silica Nanoparticles: A New Chemical Strategy To Enhance Relaxivity

The optimization of the physico-chemical properties of both Gd(III) chelates and nanocarriers is of great importance for the development of effective nanosystems for magnetic resonance imaging (MRI) applications. With this aim, macrocyclic Gd(III) chelates were selectively attached to the pendant amino groups exposed to the external surface of spheroidal mesoporous silica nanoparticles (MSNs). This was achieved by treating the metal complexes with MSNs that contained the templating surfactant molecules confined within the silica channels (hexadecyltrimethylammonium (CTA)/MSN), followed by extraction of the surfactant. The nanoparticles showed greatly improved (1)H relaxometric efficiency relative to corresponding systems that also feature Gd(III) chelates conjugated inside the pores. A further significant relaxivity enhancement was observed after chemical transformation of the free amino groups into amides. The ionic relaxivity of the final nanoparticles (r(1p) =79.1 mM(-1) s(-1); 0.5 T, 310 K) is one of the highest reported so far.

Highly Water Soluble C60 Derivatives: A New Synthesis

Abstract Unprecedented protocol, consisting in reduction of Buckminsterfullerene with Na/K alloy and successive stirring in presence of O2, affords polyhydroxylated fullerenols which are highly water soluble, from strongly basic to medium acidic conditions. The products have been characterized by means of cross polarization magic angle spinning (CPMAS) NMR, 1H‐NMR, electron, FT‐IR, Raman and mass spectroscopies. Possible paths of reaction and the role of molecular oxygen in fullerene cage‐oxidation are discussed.

A diagnostic study on folium and orchil dyes with non-invasive and micro-destructive methods.

Folium and orchil are dyes of vegetal origin. Folium is obtained from Chrozophora tinctoria (L.) A. Juss., whereas orchil is obtained from Roccella and other genera of lichens. These dyes were used in the past to impart purple hue to paintings and textiles as substitutes for the more prised Tyrian purple dye, obtained from shellfish. Despite several citations in ancient technical treatises dating back at least to the Greek-Roman age, the identification of these dyes in artworks is rare. In the case of folium, an additional drawback is that its composition is presently unknown. In this work different non-invasive (FT-IR, FT-Raman, fibre optic reflectance spectrophotometry, spectrofluorimetry, X-ray fluorescence spectrometry) and micro-invasive (surface enhanced Raman spectroscopy, matrix assisted laser desorption ionisation-time of flight-mass spectrometry, inductively coupled plasma-mass spectrometry) techniques were used in order to increase the diagnostic information available on these dyes. Measurements were carried out on the dyes extracted from raw materials and on painted or dyed parchments. The possibility to distinguish between folium and orchil by chemical analysis is discussed.

Correlations among hydrogen bonding configuration, structural order and optical coefficients in hydrogenated amorphous germanium obtained by x-ray-activated chemical vapour deposition

Hydrogenated nonstoichiometric germanium materials have been produced by x-ray-activated chemical vapour deposition from germane, GeH4. The optical gap, Tauc slope and Urbach energy have been obtained from UV?Vis spectra and correlated with structural parameters, considered as a measure of short and intermediate order, calculated by Raman spectra.The results show that the structural disorder increases with the irradiation time. Investigation of the hydrogen local bonding configuration demonstrates a correlation between the variation of the relative abundances of GeH, GeH2 and GeH3 groups and both structural parameters and Eopt value. Moreover, evidence of the crucial role played by the increase in the GeH3 group abundance in the determination of the Eopt value was revealed.

Efficient Direct Water‐Solubilisation of Single‐Walled Carbon Nanotube Derivatives

Abstract Application under mild conditions of a one‐pot reductive–oxidative synthetic protocol to single‐walled carbon nanotubes (SWNT) affords water‐soluble oxygenated products that have been characterised by mean of XPS, solution 1H‐NMR, UV‐VIS‐NIR, vibrational FTIR and Raman, SEM–energy dispersive x‐ray (EDX), XRD, and ESI‐MS techniques. Different oxygenated functionalities are evicted to be covalently bonded to carbon nanotubes frameworks, due to electrophilic insertion of O2 upon reduced carbon structures. The pH‐dependent behaviour in water solution and the observed partial fragmentation of oxidised nanotubes, that can contribute in enhancing water solubility by shortening structures, are discussed. Prolonged heating of the material affords a higher graphitisation index of the functionalised carbonaceous water‐soluble frameworks, and possible chemical paths for the partial recovering of pristine carbon nanostructures are reported. The achieved hydrophily due to polar oxygen moieties insertions on nanostructures provides a remarkable unprecedented water solubility for these carbon substrates without the attachment of large polar appendages. #Dedicated to Professor Pier Luigi Stanghellini on the occasion of his 65th birthday.

Synthesis, structural and spectroscopic study of the donor–acceptor complexes between fluorene and D2h cyano molecular building blocks

Three solid molecular complexes of fluorene with electron-withdrawing tetracyanoethylene, 1,2,4,5-tetracyanobenzene and 7,7,8,8-tetracyanoquinodimethane were synthesized. Single-crystal X-ray diffraction data elucidated the order–disorder aspects of the crystal structures ascribed to the different molecular symmetries of the employed building blocks. This hypothesis was confirmed by the structural and energetic results of ab initio periodic calculations. Donor–acceptor solid state interactions between molecular counterparts have been highlighted by electron and vibrational IR and Raman solid state spectroscopy, indicating a significant extent of electron density transfer from the fluorene unit towards the cyano-molecules. The experimental evidences of donor–acceptor interactions between molecular counterparts were compared to the lattice energies and solid state band-gaps, obtained by periodic calculations, and to the cluster HOMO–LUMO differences, obtained by isolated cluster calculations. A good agreement between spectral and theoretical data was found.

Characterization of hydrogenated amorphous germanium compounds obtained by x-ray chemical vapor deposition of germane: Effect of the irradiation dose on optical parameters and structural order

Hydrogenated nonstoichiometric germanium materials have been produced by x-ray activated-chemical vapor deposition from germane. The reactions pattern leading to the solid products has been investigated. The dose effect on the composition, the local bonding configuration, and structural characteristics of the deposited solids has been studied using infrared absorption and Raman spectroscopy and has been discussed. Optical parameters have been also determined from ultraviolet-visible spectrophotometry data. The results show that the solids are formed by a random bound network of germanium and hydrogen atoms with a-Ge zones dispersed in the matrix. The Raman results and optical parameters indicate that the structural order, both short-range and intermediate-range, decreases with increasing irradiation time. This behavior suggests that the solid is involved in the reactions leading to the final product and indicates that the formation of amorphous germanium zones is stimulated by postdeposition irradiation, ...

Functionalized nonporous silica nanoparticles as carriers for Pt(iv) anticancer prodrugs.

Nonporous silica nanoparticles (SNPs) with an external shell containing primary amino groups were proposed as potential delivery systems for Pt(iv) antitumor prodrugs. Spherical SNPs containing two different external arms, i.e. 3-aminopropyl and N-(6-aminohexyl)aminomethylene, of around 125 nm hydrodynamic diameter were loaded with two different cisplatin-based Pt(iv) complexes, namely (OC-6-44)-diamminedichloridoethoxidosuccinatoplatinum(iv) and (OC-6-44)-diamminedichloridoacetylamidosuccinatoplatinum(iv), through the formation of amide bonds between the pendant amino groups on SNPs and the free carboxylic group of the complexes. In the presence of the N-(6-aminohexyl)aminomethylene arm, the Pt(iv)-SNP conjugates showed a negligible (unwanted) Pt release by hydrolysis, whereas in the presence of ascorbic acid the reduction of Pt(iv) → Pt(ii) caused the substantial release of the active metabolite cisplatin. Conjugate Pt(iv)-SNP exhibited better antiproliferative activity on the Pt-sensitive A2780 human ovarian cancer cell line than the parent cisplatin and their free Pt(iv) precursors, due to their more efficient cellular uptake, likely by endocytosis.

Polyanionic Biopolymers for the Delivery of Pt(II) Cationic Antiproliferative Complexes

Phenanthriplatin, that is, (SP-4-3)-diamminechlorido(phenanthridine)platinum(II) nitrate, an effective antitumor cationic Pt(II) complex, was loaded on negatively charged dextran sulfate (DS) as a model vector for drug delivery via electrostatic interactions. The free complex and the corresponding conjugate with DS were tested on two standard human tumor cell lines, namely, ovarian A2780 and colon HCT 116, and on several malignant pleural mesothelioma cell lines (namely, epithelioid BR95, mixed/biphasic MG06, sarcomatoid MM98, and sarcomatoid cisplatin-resistant MM98R). The in vitro results suggest that the conjugate releases the active metabolite phenanthriplatin with a biphasic fashion. In these experimental conditions, the conjugate is slightly less active than free phenanthriplatin; but both exhibited antiproliferative potency higher than the reference metallodrug cisplatin and were able to overcome the acquired cisplatin chemoresistance in MM98R cells.

Hybrid inorganic (nonporous silica)/organic (alginate) core-shell platform for targeting a cisplatin-based Pt(IV) anticancer prodrug

Nonporous silica nanoparticles with an external shell containing the 3‑aminopropyl arm (SiNP) were further decorated with alginic acid (SiNP-ALG) as a potential biocompatible delivery system for Pt antitumor agents. Such particles were coupled with the prodrug (OC‑6‑44)‑acetato(β‑alaninato)diamminedichloridoplatinum(IV), 1, through the formation of amide bonds between the pendant carboxylate groups on SiNP-ALG and the free amino group of the complex. Cytosol extracted from tumor cells was able to quickly and efficiently reduce the Pt(IV) prodrug, and produces the active metabolite cisplatin. SiNP-ALG-Pt conjugate was more active than both cisplatin and 1, due to its more efficient cell uptake, whereas the SiNP-ALG unplatinated nanoparticles were deprived of any nonspecific toxicity.