Francesca Podda

The Kidney from Prenatal to Adult Life: Perinatal Programming and Reduction of Number of Nephrons during Development

Modified embryonic-fetal development resulting in low birth weight may lead to a reduced nephron endowment, hypertension and renal diseases in adulthood. Regarding the involvement of genetic factors, several environmental conditions may also contribute towards reducing the number of nephrons in the fetus and infant, subsequently constituting a health burden in later life. To date no methods of investigation for the early detection of a reduced nephron reserve are available. However, more structured studies should be implemented to investigate the role of angiotensin-converting enzyme inhibitors in managing proteinurias and glomerulosclerosis in children with renal conditions characterized by reduce nephron number and glomerular hypertrophic changes. In view of the current lack of specific methods of investigation and management, close monitoring of children and young adults at risk of reduced renal reserve should be carried out to enhance the early detection of potential changes in renal function.

Heavy Metal Coprecipitation with Hydrozincite [Zn5(CO3)2(OH)6] from Mine Waters Caused by Photosynthetic Microorganisms

ABSTRACT An iron-poor stream of nearly neutral pH polluted by mine tailings has been investigated for a natural phenomenon responsible for the polishing of heavy metals in mine wastewaters. A white mineralized mat, which was determined to be hydrozincite [Zn5(CO3)2(OH)6] by X-ray diffraction analysis, was observed in the stream sediments mainly in spring. The precipitate shows a total organic matter residue of 10% dry weight and contains high concentrations of Pb, Cd, Ni, Cu, and other metals. Scanning electron microscopy analysis suggests that hydrozincite is mainly of biological origin. Dormant photosynthetic microorganisms have been retrieved from 1-year-old dry hydrozincite. The autofluorescent microorganisms were imaged by a scanning confocal laser microscope. A photosynthetic filamentous bacterium, classified asScytonema sp. strain ING-1, was found associated with microalga Chlorella sp. strain SA1. This microbial community is responsible for the natural polishing of heavy metals in the water stream by coprecipitation with hydrozincite.

Structural properties of biologically controlled hydrozincite: An HRTEM and NMR spectroscopic study

Abstract The microscopic properties of biomineral hydrozincite [Zn5(CO3)2(OH)6] from Naracauli Creek (SW Sardinia) were investigated by using X-ray diffraction (XRD), nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Because the biomineral hydrozincite turned out to significantly deviate from the ideal structure of hydrozincite, synthetic and geologic hydrozincite samples were also investigated for comparison. SEM imaging shows that biomineral hydrozincite is made of small platelet-shaped crystallites having a 20-50 nm long side at the shortest and other sides measuring hundreds of nanometers long. These are interlaced to form sheaths several micrometers long. HRTEM analysis of the biomineral samples shows an imperfectly oriented aggregation of the nanocrystals that is discussed in terms of mesocrystals. Transmission electron microscopy (TEM) and XRD analysis indicate a progressive decrease in the size of the particles in the biomineral compared to the synthetic and geologic hydrozincite samples, with coherent diffraction domains in the biomineral hydrozincite that are smaller by 30-50% than in the other samples investigated in this study. 13C magic angle spinning (MAS) and cross polarization magic angle spinning (CPMAS) NMR spectra show more than one peak for all the investigated samples, despite the fact that carbon atoms have a unique crystallographic position in the hydrozincite structure. The additional peaks can reflect the presence of lattice defects typical of nanocrystals as indicated by the HRTEM images, where high concentration of lattice defects, such as grain boundaries and stacking modes, can be observed both in the biomineral and in the synthetic samples. Further additional peaks in the NMR spectra of biomineral samples are attributed to organic molecules, relicts of the biomineralization process, in agreement with the filaments observed in SEM images of biomineral samples

Natural Biomineralization in the Contaminated Sediment-Water System at the Ingurtosu Abandoned Mine

The Ingurtosu Pb–Zn mine (S-W Sardinia) was exploited for about a century until 1968. Huge amounts of tailings were abandoned, resulting in long-term heavy metal dispersion processes in both soils and waters. Zn and Pb concentration in tailings and soils attains values up to thousands of mg per kilogram. The maximum Zn concentration in water attains several hundreds of mg per liter, whereas Cd and Pb concentrations are in the order of thousands of μg per liter. Heavy metal concentration in waters of Rio Naracauli, the main stream of the area, is abated by seasonal biomineralization processes. Precipitation of hydrozincite [Zn5(CO3)2(OH)6] and of a Zn-rich amorphous phase results in a decrease of Zn concentration down to a few mg per liter. Other metals such as Pb, Cd, Cu, and Ni are coprecipitated with the Zn phases. This chapter reports the state of our knowledge on the Naracauli biomineralization process.

Zn biomineralization processes and microbial biofilm in a metal-rich stream (Naracauli, Sardinia).

Several decades after the closure of the Ingurtosu mine (SW Sardinia), a variety of seasonal Zn biomineralizations occurs. In this work, waters, microbial consortia, and seasonal precipitates from the Naracauli stream were sampled to investigate chemical composition of stream waters and biominerals, and microbial strain identity. Molecular and morphological analysis revealed that activity of dominant cyanobacterium Leptolyngbya frigida results in precipitation of Zn silicate. The activity of the cyanobacterium was associated to other bacteria and many kind of diatoms, such as Halamphora subsalina and Encyonopsis microcephala, which are trapped in the process of biomineral growth. In this work, the precipitation process is shown to be the result of many different parameters such as hydrologic regime, microbial community adaptation, and biological mediation. It results in a decrease of dissolved Zn in the stream water, and is a potential tool for Zn pollution abatement.

Uptake of Cd in hydrozincite, Zn5(CO3)2(OH)6: evidence from X-ray absorption spectroscopy and anomalous X-ray diffraction

The activity of a biological photosynthetic community promotes the seasonal precipitation of hydrozincite, Zn 5 (CO 3 ) 2 (OH) 6 , from heavy-metal contaminated waters of the Rio Naracauli stream, Sardinia. The precipitation removes from waters not only zinc, but also other heavy metals, such as Cd, Cu, Pb. The phenomenon has remarkable environmental implications, and may have remediation applications. In this study, we investigate the nature of Cd binding to hydrozincite by release tests in deionized water, backed by X-ray absorption spectroscopy (XAS) spectra collected at the Cd K -edge, and by synchrotron-based anomalous X-ray diffraction (AXRD) spectra. Release tests indicate that Cd is weakly bound to hydrozincite, being released to a significantly higher rate than Zn. The absence of a residual corresponding to a crystalline phase in the anomalous diffraction pattern indicates that, up to bulk concentration of 2 wt%, Cd occurs in hydrozincite in an essentially disordered environment. The analysis of the weak signal of the second shell in the extended X-ray absorption fine structure (EXAFS) spectra suggests a local environment similar to cadmium carbonate, but distinct from otavite. We conclude that Cd is bound to hydrozincite as a disordered amorphous surface precipitate. The loose nature of the binding suggests a limited potential of hydrozincite both as a control on the mobility of cadmium in natural waters, and as a remediation tool for contaminated effluents.

Laser-Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS): setting operating conditions and instrumental performance

— The concentration of thirty nine geochemically relevant trace elements, from 7Li to 238U, was determined in standard silicate glasses (NIST610, NIST612, BCR-2) using the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LAICP-MS) instrumentation at the Department of Earth Sciences of the University of Cagliari (Italy). The device is a Quadrupole ICP-MS (Perkin Elmer Elan DRC-e) coupled with a 213 nm Nd:YAG laser probe (New Wave Research). This configuration allows rapid, high quality, in-situ trace elements analysis in glasses and minerals. The calibration strategy, achieved using synthetic multi-element glasses (NIST612), with 44Ca as internal standard, gives an analytical accuracy within 5% error level, providing a precision between 1% and 9%, at 40 μm of crater size for all elements. At a laser spot size of 40 μm, the lower limit of detection (LLD) ranges between 0.001 and 1 ppm for all the elements; it increases by about one order of magnitude, without any significant fractionation among the different elements, for a laser spot size of 15 μm. Quality control of LA-ICP-MS analyses is routinely performed analysing a natural standard glass, the BCR-2, certified by the USGS, considered as unknown sample. Results indicate that the instrumentation capabilities are suitable for the geochemical characterisation of various materials of mineralogical, petrological, geological and environmental interest. riAssunto. — Le concentrazioni di 39 elementi in tracce, dal 7Li al 238U, sono state determinate in vetri silicatici standard (NIST610, NIST612, BCR-2) usando la strumentazione Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) installata presso il Dipartimento di Scienze della Terra dell’Universita di Cagliari (Sardegna, Italia). Lo strumento e composto da un ICP-MS del tipo Perkin Elmer Elan DRC-e accoppiato con un sistema laser Nd:YAG, sviluppato dalla New Wave Research, che lavora ad una lunghezza d’onda di 213 nm. Questo insieme consente di determinare rapidamente, e con un’alta qualita, le concentrazioni di tutti gli elementi in tracca in vetri e minerali. La calibrazione e stata ottenuta usando vetri sintetici certificati dall’USGS come materiale di riferimento (NIST612) e il Ca come standard interno, analizzato mediante SEM-EDS. La strategia di calibrazione utilizzata ha permesso di ottenere risultati con una accuratezza intorno al 5%, e con una precisione analitica che varia tra 1% e 9 %, utilizzando un diametro del fascio laser di 40 μm. Per dimensioni del diametro del fascio laser di 40 μm, il minimo limite di rilevabilita varia per tutti gli elementi tra 0,001 and 1 ppm, ed aumenta di circa un ordine di grandezza, senza che si verifichino processi di frazionamento tra i diversi elementi, per diametri di 15 μm. In ogni sessione analitica si effettuano Laser-Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS): setting operating conditions and instrumental performance clAudiA d’oriAno 1, 2, *, stefAniA dA Pelo 1, frAncescA PoddA 1 and rAffAello cioni 1, 2 1 Dip.to di Scienze della Terra, Universita degli Studi di Cagliari, Via Trentino, 51, 09127, Cagliari, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Via della Faggiola, 32, 56126, Pisa, Italy Submitted, September 2008 Accepted, November 2008 * Corresponding author, E-mail: doriano@pi.ingv.it 66 c. d’oriAno, s. dA Pelo, f. PoddA and r. cioni almeno due analisi del BCR-2, un vetro silicatico naturale certificato USGS, considerato in questo caso come campione sconosciuto, per monitorare la qualita delle analisi realizzate durante tutta la sessione. I risultati del presente lavoro indicano che la strumentazione LA-ICP-MS installata a Cagliari ha buone potenzialita per quanto riguarda lo studio geochimico di materiali di diversa composizione, e quindi puo essere utilizzata a supporto di varie tipologie di ricerche a sfondo sia minero-petrografico che geologico o geologico-ambientali.

Binding of bis-(2-ethylhexyl) phthalate at the surface of hydrozincite nanocrystals: An example of organic molecules absorption onto nanocrystalline minerals.

As a contribution to understand the interactions between mineral surfaces and organic molecules, this study reports an accurate characterization of the bis-(2-ethylhexyl) phthalate (DEHP)-Hydrozincite (DEHP-HY), that has been conduced combining the following techniques: FTIR, NMR, XAS spectroscopies and XRD. XRD patterns indicate that the HY is made of nanocrystals whose size is not influenced by the presence of DEHP. The (1)H NMR analysis of DEHP-HY samples points out the presence of interactions of DEHP with HY. CPMAS NMR analysis suggests that the interaction is operated by ester carbonyl groups while the aliphatic chain, as expected, is not involved. MAS and CPMAS NMR measurements, performed on (13)C ester carbonyl enriched DEHP, allow to demonstrate that there are two ester carbonyl linkage sites interacting at the HY surface: an acid site with a strong link and a second one with weak chemical interactions. Zn K-edge XAS spectroscopy demonstrates that the local atomic structure around Zn in DEHP-HY sample remains essentially unchanged with respect to that of HY. Such a weak structural effect suggests that HY interaction with DEHP is limited to the nanoparticle surface.

Self-preservation strategies during bacterial biomineralization with reference to hydrozincite and implications for fossilization of bacteria

The induction of mineralization by microbes has been widely demonstrated but whether induced biomineralization leads to distinct morphologies indicative of microbial involvement remains an open question. For calcium carbonate, evidence suggests that microbial induction enhances sphere formation, but the mechanisms involved and the role of microbial surfaces are unknown. Here, we describe hydrozincite biominerals from Sardinia, Italy, which apparently start life as smooth globules on cyanobacterial filaments, and evolve to spheroidal aggregates consisting of nanoplates. Complementary laboratory experiments suggest that organic compounds are critical to produce this morphology, possibly by inducing aggregation of nanoscopic crystals or nucleation within organic globules produced by metabolizing cells. These observations suggest that production of extracellular polymeric substances by microbes may constitute an effective mechanism to enhance formation of porous spheroids that minimize cell entombment while also maintaining metabolite exchange. However, the high porosity arising from aggregation-based crystal growth probably facilitates rapid oxidation of entombed cells, reducing their potential to be fossilized.

Structure of low-order hemimorphite produced in a Zn-rich environment by cyanobacterium Leptolingbya frigida

Abstract Microbes play a fundamental role in the precipitation of silicate biominerals, thereby affecting the Si geochemical cycle. The fine mechanisms ruling biomineralization are not yet fully understood, and their microscopic structures can offer deep insight into their processes of formation, reactivity and stability. In this study, a Zn silicate biomineral, extracellularly produced by cyanobacterium Leptolingbya frigida, was investigated combining nuclear magnetic resonance (NMR), Zn K-edge X-ray absorption spectroscopy (XAS) and other complementary techniques. 29Si magic angle spinning and 29Si/1H cross polarization magic angle spinning analysis, Fourier transform infrared spectroscopy (FTIR) and XAS analysis revealed a poorly crystalline phase closely resembling hemimorphite [Zn4Si2O7(OH)2·H2O]. Zn K-edge extended X-ray absorption fine structure (EXAFS) provided further structural details, revealing that the Zn-O-Si interatomic distances were 7–8% shorter than the abiotic mineral. 13C NMR spectra analysis was conducted to investigate the composition of the Zn silicate biomineral organic matrix, and results revealed that C atoms occurred in several functional groups such as carbonyl carbons, C rings, O-aliphatic chains, N-aliphatic chains, and aliphatic chains. Under slightly alkaline conditions, bacterial cell walls exhibited fundamental control on the biomineralization process by binding Zn ions and forming Zn–O–Si bonds. In this way, L. frigida cell walls served as a reactive surface for the precipitation of this Zn sorosilicate, hindering the condensation of silicon dimers. Moreover, we found a 29Si NMR band at 85 ppm that could be attributed to a (C3H6O3)2Si complex. This complex could play a role in the control of silicon polymerization, with implications for Si biomineralization processes.