Improving the In Vitro Removal of Indoxyl Sulfate and p-Cresyl Sulfate by Coating Diatomaceous Earth (DE) and Poly-vinyl-pyrrolidone-co-styrene (PVP-co-S) with Polydopamine.

Polydopamine (PDA) is a synthetic eumelanin polymer mimicking the biopolymer secreted by mussels to attach to surfaces with a high binding strength. It exhibits unique adhesive properties and has recently attracted considerable interest as a multifunctional thin film coating. In this study, we demonstrate that a PDA coating on silica- and polymer-based materials improves the entrapment and retention of uremic toxins produced in specific diseases. The low-cost natural nanotextured fossil diatomaceous earth (DE), an abundant source of mesoporous silica, and polyvinylpyrrolidone-co-Styrene (PVP-co-S), a commercial absorbent comprising polymeric particles, were easily coated with a PDA layer by oxidative polymerization of dopamine at mild basic aqueous conditions. An in-depth chemical-physical investigation of both the resulting PDA-coated materials was performed by SEM, AFM, UV-visible, Raman spectroscopy and spectroscopic ellipsometry. Finally, the obtained hybrid systems were successfully tested for the removal of two uremic toxins (indoxyl sulfate and p-cresyl sulfate) directly from patients' sera.

Incorporating a molecular antenna in diatom microalgae cells enhances photosynthesis.

Diatom microalgae have great industrial potential as next-generation sources of biomaterials and biofuels. Effective scale-up of their production can be pursued by enhancing the efficiency of their photosynthetic process in a way that increases the solar-to-biomass conversion yield. A proof-of-concept demonstration is given of the possibility of enhancing the light absorption of algae and of increasing their efficiency in photosynthesis by in vivo incorporation of an organic dye which acts as an antenna and enhances cells' growth and biomass production without resorting to genetic modification. A molecular dye (Cy5) is incorporated in Thalassiosira weissflogii diatom cells by simply adding it to the culture medium and thus filling the orange gap that limits their absorption of sunlight. Cy5 enhances diatoms' photosynthetic oxygen production and cell density by 49% and 40%, respectively. Cy5 incorporation also increases by 12% the algal lipid free fatty acid (FFA) production versus the pristine cell culture, thus representing a suitable way to enhance biofuel generation from algal species. Time-resolved spectroscopy reveals Förster Resonance Energy Transfer (FRET) from Cy5 to algal chlorophyll. The present approach lays the basis for non-genetic tailoring of diatoms' spectral response to light harvesting, opening up new ways for their industrial valorization.

Biosilica from Living Diatoms: Investigations on Biocompatibility of Bare and Chemically Modified Thalassiosira weissflogii Silica Shells.

In the past decade, mesoporous silica nanoparticles (MSNs) with a large surface area and pore volume have attracted considerable attention for their application in drug delivery and biomedicine. Here we propose biosilica from diatoms as an alternative source of mesoporous materials in the field of multifunctional supports for cell growth: the biosilica surfaces were chemically modified by traditional silanization methods resulting in diatom silica microparticles functionalized with 3-mercaptopropyl-trimethoxysilane (MPTMS) and 3-aminopropyl-triethoxysilane (APTES). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the -SH or -NH2 were successfully grafted onto the biosilica surface. The relationship among the type of functional groups and the cell viability was established as well as the interaction of the cells with the nanoporosity of frustules. These results show that diatom microparticles are promising natural biomaterials suitable for cell growth, and that the surfaces, owing to the mercapto groups, exhibit good biocompatibility.

Discrimination of mercuric ions in piezoelectric sensors with a conjugated polymeric active layer.

The synthetic conjugated poly(1,4-arylene-2,5-thienylene) containing benzo[c][2,1,3]thiadiazole monomeric units (Bz-PAT) is proposed as active layer for the selective detection of mercuric ions. The Bz-PAT polymer chemical structure induces the formation of a disordered film with numerous vacancies and the size of these defects could be exploited for a reversible trapping of mercuric ions. For these reasons the Langmuir-Schaefer (LS) deposition method has been employed for transferring Bz-PAT layers with the desired accurate bi-dimensional organization control of the layer and with a high control of the deposition parameters. In this contribution, the frequency variation of quartz crystal microbalances functionalized with 10, 20, 30 and 40 LS runs of Bz-PAT have been investigated in response to the injection of aqueous solutions of HgCl2, Pb(NO3)2, NiCl2, CdCl2 and ZnSO4 at different concentrations (0.5 mM, 1 mM, 5 mM). An almost linear dependence on the number of the LS layers and hence on the film thickness, measured by means of ellipsometric spectroscopy, has been found in terms of sensor response to concentration of Hg2+ ions fluxed. By means of UV-Vis spectroscopy, the variations in the π-π* absorption band of the polymer, attributed to the thiophene segment, induced by HgCl2 injection has been analyzed and explained as a consequence of the electron transfer from the mercuric ion to the polymer solid film. These results, together with the linear relation found between the number of deposited layers and LS film thickness, suggest that the sensing mechanism can be explained both by an electron interaction between active layer and analyte and a diffusion mechanism of Hg2+ into the solid film that reaches an asymptotic value at 30 runs (about 80 nm), then a higher number of layers does not influence the sensor sensibility.

The correct assignment of stereochemistry in di-µ-dichlorido-bis{bis[2-(5-benzylsulfonyl)-3-fluoro-2-(pyridin-2-yl)phenyl-κ2N,C1]iridium(III)} toluene monosolvate.

The title complex, [Ir2(C18H13FNO2S)4Cl2]·C7H8, was crystallized from dichloromethane solution under a toluene atmosphere. It is a dimeric complex in which each of the two Ir(III) centres is octahedrally coordinated by two bridging chloride ligands and by two chelating cyclometalated 2-(4-benzylsulfonyl-2-fluorophenyl)pyridine ligands. The crystal structure analysis unequivocally establishes the trans disposition of the two cyclometalated ligands bound to each Ir(III) centre, contrary to our previous hypothesis of a cis disposition. The latter was based on the (1)H NMR spectra of a series of dimeric benzylsulfonyl-functionalized dichloride-bridged iridium complexes, including the compound described in the present work [Ragni et al. (2009). Chem. Eur. J. 15, 136-148]. The toluene solvent molecules, embedded in cavities in the crystal structure, are highly disordered and could not be modelled successfully; their contribution was removed from the refinement using the SQUEEZE routine in the program PLATON [Spek (2009). Acta Cryst. D65, 148-155].