187,547 research outputs found
A fistful of chemico-physical parameters crucial for 1H-NMR relaxation : the effect of size, shape and coating in iron oxides core-shell nanoparticles
No full textAn increasing awareness about novel medical applications of smaller, inorganic-based nanoparticles, possessing unique properties at the nanoscale, has led to a burst of research activities in the development of “nanoprobes” for diagnostic medicine and agents for novel, externally activated, therapies. In this research field, magnetic nanoparticles (MNPs) are prominent due to fundamental peculiar properties which make them particularly appealing to materials and biomedical applications.
In particular, much attention was devoted to MNPs useful as agents for Magnetic Resonance Imaging (MRI), Optical Imaging (OI) and Magnetic Fluid Hyperthermia (MFH), carriers for drugs and vectors for molecular targeting. The possibility to collect images of the regions where the MNPs are delivered through MRI and eventually OI (if functionalized with a luminescent molecule), is joint to their use under radio-frequency fields, with frequency of the order of 100 KHz, which causes a local release of heat directed to tumour cells (the MFH effect), possibly inducing their death. By such materials, theranostic agents can be obtained. On the other hand, in the field of drug delivery and molecular targeting, few examples of reproducible experiments using superparamagnetic nanoparticles are actually present in literature. Thus, the applications of MNPs to nanomedicine is currently of growing interest in the world.
The main objectives of my research group in the last decade was to contribute to the knowledge of physical mechanisms at the basis of MNPs used in biomedicine (especially MRI) and to propose some novel systems in strict collaboration with different research groups of chemists and biologists. I will present a mini-review of different case studies [1-4] where I show how the chemico-physical characteristics of MNPs are strictly correlated to their properties and can be partially interpreted with the most famous heuristic model [5] used in literature for NMR relaxivity profiles.
Key Words: magnetic nanoparticles, NMR relaxivity, nanomagnetism
References
1. F. Brero, M. Basini, M. Avolio, F. Orsini F., P. Arosio, C. Sangregorio, C. Innocenti, A. Guerrini, J Boucard, E. Ishow, M. Lecouvey, J. Fresnais, L. Lartigue, A. Lascialfari, Nanomaterials, 10 (2020) 1660-1672.
2. M. Basini, A. Guerrini, M. Cobianchi, F. Orsini, D. Bettega, M. Avolio, C. Innocenti, C. Sangregorio, A. Lascialfari, P. Arosio, Journal of Alloys and Compounds, 770 (2019), 58-66.
3. M. Basini, T. Orlando., P. Arosio, M.F. Casula, D. Espa, S. Murgia, C. Sangregorio, C. Innocenti, A. Lascialfari, J. Chem. Phys., 146 (2017), 034703.
4. Bordonali L., Kalaivani T., Sabareesh K.P.V., Innocenti C., Fantechi E., Sangregorio C., Casula M.F., Lartigue L., Larionova J., Guari Y., Corti M., Arosio P., Lascialfari A., Journal of Physics: Condensed Matter, 25 (2013), 066008
5. A. Roch, R.N. Muller, P. Gillis, J. Chem. Phys. 110 (1999) 5403-5411
Direct P-Wave Seismic Noise Interferometry for Groundwater Monitoring: A Modelling Study
No full textIn this study, we monitor the depth variation of an unconfined aquifer by applying seismic noise interferometry to synthetic data modelled with a 2D finite-difference software. We consider two models with the same subsurface geological structure, but with different water table levels representing two monitoring periods. The receivers are placed at the topographic surface and collect the seismic signals generated by a source located at the bottom of the aquifer to simulate a pumping system. First, cross-correlation of seismic traces with a reference one is used to produce interferograms (i.e., virtual surveys) for both the tested models. Then, direct P-wave arrivals identified in the two interferograms are compared through the stretching technique in order to estimate the relative velocity changes (dv/v). Finally, the estimated dv/v values are related to theoretical ones obtained using a reference subsurface model to produce the water level depth in the considered monitoring period.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Geophysics and Petrophysic
Correlation between CBCT and torque-based measurements of bone density: a study on polyurethane foam blocks and bovine ribs
No full textPurpose:. To assess whether (and to what extent) average torque readings evaluating the bone density of polyurethane foam blocks and bovine ribs are correlated with that of gray values (GVs) measured via CBCT scans, both at the site of reading and at adjacent sites where bone is expected to engage the implant threads.
Materials and Methods: Average torque readings were collected on blocks and ribs via CBCT scans that were then analyzed to measure the GVs of purposedly designed regions of interest (ROls). The ROls were shaped as concentric hollow cylinders centered on the sites of average torque measurements. The relation between average torque and GVs was investigated through correlation analyses.
Results: The correlation between average torque and GVs from blocks was strong (r = 0.94, r2 = 0.89, P< .001), which was independent of the ROI size. On the bovine ribs, the correlation was weak but significant (r = 0.23, P = .029); however, it become stronger when denser bone (average torque = 7 Ncm) was tested (r = 0.41, P = .008). This result was independent from the distance of the site where the average torque had been read. Loss of average torque—-GV interchangeability observed on bovine ribs was likely caused by intrinsic bone characteristics, such as an abundance of bone marrow and nonmineralized tissue, possibly having a confounding effect on GV measurements, especially at lower bone densities.
Conclusions: Within the limitations of the study, average torque values were found to estimate physical bone density just as well as GVs from CBCT scans. In low-density bone, the assessment of mineral bone density was also found to possibly be more informative than GVs. Results of this study suggest that the micromotor may be presently regarded as a complementary tool to CBCT assessment of bone density and quality in the clinical setting
Valiron and Abel equations for holomorphic self-maps of the polydisc
No full textWe introduce a notion of hyperbolicity and parabolicity for a holomorphic self-map f: δN → δN of the polydisc which does not admit fixed points in δN. We generalize to the polydisc two classical one-variable results: we solve the Valiron equation for a hyperbolic f and the Abel equation for a parabolic nonzero-step f. This is done by studying the canonical Kobayashi hyperbolic semi-model of f and by obtaining a normal form for the automorphisms of the polydisc. In the case of the Valiron equation, we also describe the space of all solutions
Recent Developments in the Use of Magnetic Fluid Hyperthermia on Glioblastoma Multiforme Disease
No full textThe first evidence of the efficacy in the cancer treatment of hyperthermia, therapy focused on the heating of tumor masses to kill cells and tissues, went back almost a century and a half. One of the most promising techniques for increasing the cells and tissues temperature is based on the use of magnetic nanoparticles dispersed in concentrated colloidal suspensions and stimulated by an external alternating electromagnetic field, known as Magnetic Fluid Hyperthermia. Recently this technique has been used as coadjutant treatment of the most applied chemo and radio therapies in a series of different tumors, but in particular for Glioblastoma Multiforme till to clinical trials level. In this work, we report some of most significant progresses regarding the use of Magnetic Fluid Hyperthermia on Glioblastoma Multiforme disease published in literature during the last year, describing the more interesting outcomes for potential future clinical applications
Synthesis of dual action Smac/Zinc-Chelator conjugates as putative proapoptotic agents
No full textApoptosis, or programmed cell death, is a critical cell process in normal development and homeostasis of multicellular organisms. It is now recognized that dysfunction of the apoptosis machinery is a hallmark of cancer. Accordingly, targeting critical apoptosis regulators is an attractive approach for the development of new classes of therapies for the treatment of cancer and other human diseases.
The X-linked inhibitor of apoptosis protein (XIAP) is a member of IAP proteins that potently inhibit apoptosis[1]. XIAP contains three baculovirus IAP repeat (BIR) domains. The mechanism of action of XIAP entails its binding with initiator and effector caspases through its BIR domains. In cells, the anti-apoptotic function of XIAP is antagonized by Smac/DIABLO (second mitochondria-derived activator of caspases or direct IAP binding protein with low pI). Despite the rather complex structure of Smac, its short N-terminal AVPI sequence is sufficient to trigger the inactivation of anti-apoptotic XIAP[2]. Our research group has shown how small monomeric, AVPI-inspired Smac mimics can bind XIAP on its BIR3 domain with sub-micromolar potency[3,4]. Executioner caspase-3, -6 and -7 exist within the cytosol as inactive zymogens (procaspases) activated by limited proteolysis within their inter-domain linker, carried out by an initiator caspaseThe essential executioner caspase-3 is proteolytically activated by either caspase-8 or -9. Zinc ions co-localize with procaspase-3/caspase-3 and inhibit its enzymatic activity in the cell by direct interaction with an Asp-Asp-Asp (DDD) “safety catch” region[5]. Thus, in this work we coupled a zinc chelator moiety based on di(picolylamide)amine (DPA) and its N,N-bis(pyridin-2-ylmethyl)ethane-1,2-diamine (BPEN) derivative to pro-apoptotic Smac mimetics, synthesized starting from known intermediates 1 and 2.
Dual action Smac mimetic-zinc chelators 3 and 4 were prepared from compounds 1 and 2 as shown in Scheme 1 and characterized in vitro, using cell-free and cellular assays[6,7]. Their ability to bind XIAP BIR3 domain, to process pro-caspase-3 to caspase-3 and their cytotoxicity have been experimentally determined, and favorably compared with those of a potent Smac mimic compound, especially for the most potent, tribasic dual action compound 4. Furthermore, the Zinc affinity for both compounds was confirmed by fluorescence measurements.
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Stuckey, S. Wang, Anal. Biochem. 2008, 374, 87-98
Green Fluorescent Protein-Based Chloride Ion Sensors for In Vivo Imaging
No full textcapitolo di libro: in: G. Jung (Ed.), Fluorescent Proteins II, Springer Berlin Heidelber
Electrophoretic analysis of horse tissue ferritins at different pH values
No full textElectrophoretic mobilities of ferritins from horse heart, liver and spleen were compared in the pH range 3.5-10. Electrophoretic titrations and continuous buffer electrophoreses were used. The order of anionic mobilities was heart>liver>spleen at alkaline pH and this order was reversed in the neutral to acidic range. This order of mobilities, and the intermediate behavior of liver in respect to the other two ferritins correlate with the known subunit composition of the three ferritins, and strongly support the idea of different amino acid residues being exposed on the protein shell surfaces. From the analyses of differential mobility around the pK values of the various ionizable groups it was concluded that heart and spleen ferritins have a very similar number of acidic amino acid residues on their surfaces, whereas they differ in basic residues. Heart seems to have about 15% more Lys and Arg, and twice as many His as spleen
Sulle orme di Vincenzo de' Paoli. Jeanne-Antide Thouret e le Suore della Carità dalla Francia rivoluzionaria alla Napoli della Restaurazione
No full textNew functions for an iron storage protein: The role of ferritin in immunity and autoimmunity.
No full textFerritin is a ubiquitous and specialised protein involved in the intracellular storage of iron; it is also present in serum and other biological fluids, although its secretion processes are still unclear. We here review evidence supporting the hypothesis that macrophages play a role in the production and secretion of extracellular ferritin, as well as evidence supporting a novel function as a signalling molecule and immune regulator. In particular, H-ferritin, which inhibits the proliferation of lymphoid and myeloid cells, may be regarded as a negative regulator of human and murine hematopoiesis. The idea that it also acts as a signalling protein has been supported by the cloning and characterisation of the specific H-ferritin receptor TIM-2, a member of the TIM gene family. A number of studies of the mouse TIM gene family indicate that this protein plays an important role in immune-mediated diseases. This last finding, together with the fact that ferritin acts as an immuno-suppressor, has allowed us to formulate hypotheses regarding the possible role of alterations of H-ferritin/TIM-2 binding/signalling in the pathogenesis of autoimmune diseases
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