Synthesis, properties and applications of bioinspired nitrogen and/or group 16 aromatic heterocycles

A prominent position among naturally occurring N,S heterocyclic systems is occupied by 1,4-benzothiazines that form the key structural unit of pheomelanin pigments responsible for the red hair phenotype, typically found in red hair individuals with pale skin and enhanced susceptibility to skin cancer and melanoma. The chromophore exhibited by these pigments has been associated to the presence of the Δ2,2'-bi-(2H-1,4-benzothiazine) system. This is an indigo type chromophore which has not so far been fully exploited in the field of functional dyes. This Δ2,2'-bi-(2H-1,4-benzothiazine) exhibits a significant pH dependence, with a bathochromic shift from red to blue in acids and a marked photochromism under sunlight with reversible conversion in organic solvents of a yellow-orange species with abs max at 450 nm to a red one with abs max at 480 nm. Another related chromophore based on a push pull system occurs in the natural pigments cyanines, having organic nitrogen centers, one of the imine and the other of the enamine type. Some of these cyanines are currently used as biological reporters and in other technological applications . In this PhD project the research activity has been focused on 1,4-benzothiazine systems. Inspired by the peculiar properties of the chromophore exhibited by pheomelanin and natural cyanines the access to new classes of dyes with potential technological applications has been explored. The role of the benzothiazine structural units in the biological function of pheomelanin pigment was also addressed. Structural re-examination of the stable yellow isomer of 2,2’-bibenzothiazine by an integrated 2D NMR and theoretical approach revealed that the stable yellow species is in fact the cis isomer. A novel picture of 2,2’-bibenzothiazine as a four-state system with photochromic and pH-dependent behavior was proposed. Stable 3-substituted 1,4-benzothiazines, namely the 3-phenyl- and the 3-methyl-2H-1,4-benzothiazine were obtained by improvement of previously reported procedures in 50-60% average yields. When exposed to peroxides or biologically relevant metals at micromolar concentration and in the presence of strong acids, 3-phenyl-2H-1,4-benzothiazine is efficiently converted to a green-blue 2,2’-bi(2H-1,4-benzothiazine) via colorless intermediates identified as single-bonded dimers. A resonance-stabilized benzothiazinyl radical intermediate was evidenced and characterized by EPR spectroscopy. Interestingly, 3-phenyl-2H-1,4-benzothiazine proved useful for the visual detection of peroxides in aged ethereal solvents and an efficient inhibitor against corrosion of the rusty iron objects induced by concentrated HCl. Two different approaches were pursued for the synthetic access to benzothiazine cyanines, one involving reaction with dialdehydes that may allow for the build-up of a conjugated bridge between the two benzothiazine units and the other based on the condensation of the benzothiazine with aromatic para N-alkyl substituted aldehydes. All these products showed a marked pH dependence of the chromophores, associated in some cases to high molar extinction coefficients (up to 18,000), and emission of fluorescence tunable with the pH conditions. The chemistry of benzothiazine units accounting for the biological function of pheomelanin pigments was also addressed. Though commonly regarded as photosensitizer agents capable of amplifying generation of reactive oxygen species following UV radiation, recently, pheomelanin has also been implicated in UV-independent pathways of oxidative stress. To get an insight into these processes the reactivity of natural and synthetic pheomelanins toward critical cellular antioxidants was investigated. A marked ability of pheomelanin from red human hair, but not of eumelanin from black human hair to reduce the levels of GSH and NADH was evidenced. In the absence of oxygen GSH and NADH depletion was not observed while the presence of enzymes as superoxide dismutase and catalase did not modify the effect of pheomelanin suggesting a ROS independent mechanism. The mechanism of GSH oxidation by red hair pheomelanin was investigated by EPR spectroscopy. During a visit at the Department of Chemical Physics of Lund University (Sweden) in the research unit headed by professor Sundstrom, the photochemistry of putative structural subunits of pheomelanin including benzothiazoles, benzothiazine dimers and dihydroisoquinolines as well as of the natural pigments and synthetic models was investigated. Steady state absorption and emission spectra at different pHs showed marked differences that can be accounted for in terms of the ionization state of the functional groups. Time resolved measurements under different pH conditions allowed for identification of short lived species and characterization of fast processes like intramolecular and solvent proton transfer that are primary processes of excited state deactivation. Analysis of the results indicated the major role of the benzothiazine units compared to benzothiazole and 3-substituted units in determining the behaviour of natural pheomelanins

Optimizing the relaxivity of MRI probes at high magnetic field strengths with binuclear GdIIIComplexes

The key criteria to optimize the relaxivity of a Gd(III) contrast agent at high fields (defined as the region 65 1.5 T) can be summarized as follows: (i) the occurrence of a rotational correlation time \u3c4R in the range of ca. 0.2\u20130.5 ns; (ii) the rate of water exchange is not critical, but a \u3c4M < 100 ns is preferred; (iii) a relevant contribution from water molecules in the second sphere of hydration. In addition, the use of macrocycle-based systems ensures the formation of thermodynamically and kinetically stable Gd(III) complexes. Binuclear Gd(III) complexes could potentially meet these requirements. Their efficiency depends primarily on the degree of flexibility of the linker connecting the two monomeric units, the absence of local motions and the presence of contribution from the second sphere water molecules. With the aim to maximize relaxivity (per Gd) over a wide range of magnetic field strengths, two binuclear Gd(III) chelates derived from the well-known macrocyclic systems DOTA-monopropionamide and HPDO3A (Gd2L1 and Gd2L2, respectively) were synthesized through a multistep synthesis. Chemical Exchange Saturation Transfer (CEST) experiments carried out on Eu2L2 at different pH showed the occurrence of a CEST effect at acidic pH that disappears at neutral pH, associated with the deprotonation of the hydroxyl groups. Then, a complete 1H and 17O NMR relaxometric study was carried out in order to evaluate the parameters that govern the relaxivity associated with these complexes. The relaxivities of Gd2L1 and Gd2L2 (20 MHz, 298 K) are 8.7 and 9.5 mM 121 s 121, respectively, +77% and +106% higher than the relaxivity values of the corresponding mononuclear GdDOTAMAP-En and GdHPDO3A complexes. A significant contribution of second sphere water molecules was accounted for the strong relaxivity enhancement of Gd2L2. MR phantom images of the dinuclear complexes compared to GdHPDO3A, recorded at 7 T, confirmed the superiority of Gd2L2. Finally, ab initio (DFT) calculations were performed to obtain information about the solution structure of the dinuclear complexes

A Semi Rigid Novel Hydroxamate AMPED-Based Ligand for 89Zr PET Imaging

In this work, we designed, developed, characterized, and investigated a new chelator and its bifunctional derivative for 89Zr labeling and PET-imaging. In a preliminary study, we synthesized two hexadentate chelators named AAZTHAS and AAZTHAG, based on the seven-membered heterocycle AMPED (6-amino-6-methylperhydro-1,4-diazepine) with the aim to increase the rigidity of the 89Zr complex by using N-methyl-N-(hydroxy)succinamide or N-methyl-N-(hydroxy)glutaramide pendant arms attached to the cyclic structure. N-methylhydroxamate groups are the donor groups chosen to efficiently coordinate 89Zr. After in vitro stability tests, we selected the chelator with longer arms, AAZTHAG, as the best complexing agent for 89Zr presenting a stability of 86.4 5.5% in human serum (HS) for at least 72 h. Small animal PET/CT static scans acquired at different time points (up to 24 h) and ex vivo organ distribution studies were then carried out in healthy nude mice (n = 3) to investigate the stability and biodistribution in vivo of this new 89Zr-based complex. High stability in vivo, with low accumulation of free 89Zr in bones and kidneys, was measured. Furthermore, an activated ester functionalized version of AAZTHAG was synthesized to allow the conjugation with biomolecules such as antibodies. The bifunctional chelator was then conjugated to the human anti-HER2 monoclonal antibody Trastuzumab (Tz) as a proof of principle test of conjugation to biologically active molecules. The final 89Zr labeled compound was characterized via radio-HPLC and SDS-PAGE followed by autoradiography, and its stability in different solutions was assessed for at least 4 days

Synthesis and preliminary in vitro evaluation of DOTA-Tenatumomab conjugates for theranostic applications in tenascin expressing tumors

Tenatumomab is an anti-tenascin murine monoclonal antibody previously used in clinical trials for delivering radionuclides to tumors by both pre-targeting (biotinylated Tenatumomab within PAGRIT) and direct 131Iodine labeling approaches. Here we present the synthesis and in vitro characterization of three Tenatumomab conjugates to bifunctional chelating agents (NHS-DOTA, NCS-DOTA and NCS-DTPA). Results indicate ST8198AA1 (Tenatumomab-DOTAMA, derived by conjugation of NHS-DOTA), as the most promising candidate in terms of conjugation rate and yield, stability, antigen immunoreactivity and affinity. Labeling efficiency of the different chelators was investigated with a panel of cold metals indicating DOTAMA as the best chelator. Labeling of Tenatumomab-DOTAMA was then optimized with several metals and stability performed confirms suitability of this conjugate for further development. ST8198AA1 represents an improvement of the previous antibody forms because the labeling with radionuclides like 177Lu or 64Cu would allow theranostic applications in patients bearing tenascin expressing tumors

Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

A nonlinear predictor for the supervision of photovoltaic strings performances

In this paper, a nonlinear predictor of the electrical power produced by a PV string is proposed. The first phase of the approach is the training of the predictor, during which four characteristic parameters are determined. Such coefficients are representative of the string under study and define its electrical signature (identikit). Once trained the model, when new monitoring data are available, the mismatch between the forecasted and measured electrical power can be assumed as a reliable marker of the performances of the string, since the greater the mismatch, the worse the string efficiency. The analysis of the forecasting error, therefore, enables the detection of losses of energy production. In particular, a strength of the proposed approach is the possibility to distinguish the losses due to aging phenomena from the losses due to the dust or dirt accumulation. The method has been tested and validated for a real case study and the obtained results are presented in the paper

A data-driven prognostic approach based on statistical similarity: An application to industrial circuit breakers

In this paper, a data-driven prognostic algorithm for the estimation of the Remaining Useful Life (RUL) of a product is proposed. It is based on the acquisition and exploitation of run-to-failure data of homogeneous products, in the followings referred as fleet of products. The algorithm is able to detect the set of products (sub-fleet of products) showing highest degradation pattern similarity with the one under study and exploits the related monitoring data for a reliable prediction of the RUL. In particular, a novel methodology for the sub-fleet identification is presented and compared with other solution found in literature. The results obtained for a real application case as Medium and High Voltage Circuit Breaker, have shown a high prognostic power for the algorithm, which therefore represents a potential tool for an effective Predictive Maintenance (PdM) strategy

A hybrid approach for solar radiation and photovoltaic power short-term forecast

In this paper a model devoted to the forecast of solar radiation and Photovoltaic (PV) power has been addressed. In particular, for what concerns the solar radiation prediction, the novelty of the approach stays in the use of the clear sky model proposed by Hottel fed by the output of a data driven algorithm. In this hybrid approach, key parameters are computed through the exploitation of a database of solar radiation values. The PV power is then forecasted through an Auto Associative Kernel Regression (AAKR) technique. The proposed model has been tested for a real application case, a PV plant located in South Africa, and the results have highlighted high effectiveness of the proposal