Ottimizzazione di un protocollo di anticoagulazione regionale con citrato in CRRT

Ottimizzazione di un protocollo di anticoagulazione regionale con citrato in CRRT Introduzione: La necessità di un'anticoagulazione continua e l'ipofosforemia in corso di trattamento sono problemi costranti in corso di CRRT. Il nostro studio ha cercato di dimostrare l'efficacia e la sicurezza dell'anticoagulazione regionale con citrato in CVVH basato sull'utilizzo di una soluzione di citrato (18 mmol/L) associata ad una soluzione di reinfusione contenente fosfato, recentemente disponibile in commercio, al fine di ridurre l'ipofosfatemia in corso di CRRT. Metodi: Abbiamo utilizzato il nostro protocollo basato sull'utilizzo di una concentrazione di citrato contenente 18 mmol/l associata ad una soluzione di reinfusione contenente fosfato in un piccolo gruppo di pazienti ricoverati in terapia intensiva post-cardiochirurgica, sottoposti a CRRT per insufficienza renale acuta. Risultati: Il nostro protocollo ha garantito un'adeguata durata del circuito ed un ottimo controllo dell'equilibrio acido-base in ogni paziente. E' stata necessaria solo una minima supplementazione di fosforo in alcuni dei pazienti trattati. Conclusioni: Il nostro protocollo basato sull' utilizzo di una soluzione a concentrazione di citrato maggiore (18 mmol/l), permette un miglior controllo dell'equilibrio acido-base rispetto all'utilizzo della soluzione a più bassa concentrazione di citrato. L'uso di una minore dose di citrato ed il mantenimento di un target maggiore di calcio ionizzato all'interno del circuito sono comunque associati ad un'adeguata durata del circuito. I livelli di fosforemia sono rimasti sostanzialmente stabili nella maggior parte dei pazienti trattati, grazie alla presenza di fosfato nella soluzione utilizzata come reinfusione in post-diluizione.

Photoactive (supra)molecular devices in double layer membranes

Biological systems are complex and highly organized architectures governed by non-covalent interactions responsible for the regulation of essential tasks in all living organisms. These systems are a constant source of inspiration for supramolecular chemists aiming to design multicomponent molecular assemblies able to perform elaborated tasks, thanks to the role and action of the components that constitute them. Artificial supramolecular systems exploit non-covalent interactions to mimic naturally occurring events. In this context, stimuli-responsive supramolecular systems have attracted attention due to the possibility to control macroscopic effects through modifications at the nanoscale. This thesis is divided in three experimental chapters, characterized by a progressive increase in molecular complexity. Initially, the preparation and studies of liposomes functionalized with a photoactive guest such as azobenzene in the bilayer were tackled, in order to evaluate the effect of such photochrome on the vesicle properties. Subsequently, the synthesis and studies of thread-like molecules comprising an azobenzene functionality was reported. Such molecules were conceived to be intercalated in the bilayer membrane of liposomes with the aim to be used as components for photoresponsive transmembrane molecular pumps. Finally, a [3]rotaxane was developed and studied in solution. This system is composed of two crown ether rings interlocked with an axle containing three recognition sites for the macrocycles, i.e. two pH-switchable ammonium stations and a permanent triazolium station. Such molecule was designed to achieve a change in the ratio between the recognition sites and the crown ethers as a consequence of acid-base inputs. This leads to the formation of rotaxanes containing a number of recognition sites respectively larger, equal or lower than the number of interlocked rings and connected by a network of acid-base reactions.

Valorization of bio-alcohols into added value chemicals

The present research work focused on the valorisation and upgrading of bio-ethanol over heterogeneous catalysts in a lab-scale continuous gas-flow system. In the Unibo laboratories, catalytic tests have been carried out in the temperature range 300-600°C by feeding an ethanol/He mixture in the reactor. After choosing the reaction conditions, ion-exchanged hydroxyapatite with transition metals (i.e., Fe, Cu) and alkaline earth metal (i.e., Sr) have been synthesized and tested. The Sr-HAP catalyst led to the formation of a complex reaction mixture the composition of which need further optimization in order to fill the requisite to be used as fuel-blend. Then, some zirconium-oxide based catalysts have been prepared through two different methods, precipitation and hydrothermal, by varying some synthetic parameters (i.e., pH, the nature of the base) and by adding a transition metal as dopant agent (i.e., Ti and Y). The presence of a dopant into the zirconia structure favoured the stabilization of the tetragonal or cubic phase against the monoclinic one. Interestingly, 5%mol Ti-doped zirconia exhibited a different catalytic behaviour yielding diethyl ether as major product at 300°C, while all the others samples produced mainly ethylene. Then, the effect of acid-base properties of sepiolite, using alkali metals (i.e., Na, K, Cs) with different metal loading (i.e., 2, 4, 5, 7, 14 wt%) as promoters, and of the redox properties of sepiolite-supported CuO or NiO, on the catalytic conversion of ethanol into n-butanol has been investigated. Thermal treated sepiolite samples mainly acted as acid catalyst, yielding preferentially the dehydration products of ethanol (ethylene and diethyl ether). Best results in terms of activity (ethanol conversion, 59%) and n-butanol selectivity (30%) where obtained at 400ºC and a contact time, W/F, of 2 g/mL·s over the catalyst consisting of sepiolite calcined at 500ºC modified with 7 wt% of cesium.

Jasmonates and abscisic acid influence fruit ripening and plant water use: practical, physiological and morphological aspects

The aim of the present thesis was to better understand the physiological role of the phytohormones jasmonates (JAs) and abscisic acid (ABA) during fruit ripening in prospect of a possible field application of JAs and ABA to improve fruit yield and quality. In particular, the effects of exogenous application of these substances at different fruit developmental stages and under different experimental conditions were evaluated. Some aspects of the water relations upon ABA treatment were also analysed. Three fruit species, peach (Prunus persica L. Batsch), golden (Actinidia chinensis) and green kiwifruit (Actinidia deliciosa), and several of their cvs, were used for the trials. Different experimental models were adopted: fruits in planta, detached fruit, detached branches with fruit, girdled branches and micropropagated plants. The work was structured into four sets of experiments as follows: (i) Pre-harvest methyl jasmonate (MJ) application was performed at S3/S4 transition under field conditions in Redhaven peach; ethylene production, ripening index, fruit quality and shelf-life were assessed showing that MJ-treated fruit were firmer and thus less ripe than controls as confirmed by the Index of Absorbance Difference (IAD), but exhibited a shorter shelf-life due to an increase in ethylene production. Moreover, the time course of the expression of ethylene-, auxin- and other ripening-related genes was determined. Ripening-related ACO1 and ACS1 transcript accumulation was inhibited though transiently by MJ, and gene expression of the ethylene receptor ETR2 and of the ethylene-related transcription factor ERF2 was also altered. The time course of the expression of several auxin-related genes was strongly affected by MJ suggesting an increase in auxin biosynthesis, altered auxin conjugation and release as well as perception and transport; the need for a correct ethylene/auxin balance during ripening was confirmed. (ii) Pre- and post-harvest ABA applications were carried out under field conditions in Flaminia and O’Henry peach and Stark Red Gold nectarine fruit; ethylene production, ripening index, fruit quality and shelf-life were assessed. Results show that pre-harvest ABA applications increase fruit size and skin color intensity. Also post-harvest ABA treatments alter ripening-related parameters; in particular, while ethylene production is impaired in ABA-treated fruit soluble solids concentration (SSC) is enhanced. Following field ABA applications stem water potential was modified since ABA-treated peach trees retain more water. (iii) Pre- and post-harvest ABA and PDJ treatments were carried out in both kiwifruit species under field conditions at different fruit developmental stages and in post-harvest. Ripening index, fruit quality, plant transpiration, photosynthesis and stomatal conductance were assessed. Pre-harvest treatments enhance SSC in the two cvs and flesh color development in golden kiwifruit. Post-harvest applications of either ABA or ABA plus PDJ lead to increased SSC. In addition, ABA reduces gas exchanges in A. deliciosa. (iv) Spray, drench and dipping ABA treatments were performed in micropropagated peach plants and in peach and nectarine detached branches; plant water use and transpiration, biomass production and fruit dehydration were determined. In both plants and branches ABA significantly reduces water use and fruit dehydration. No negative effects on biomass production were detected. The present information, mainly arising from plant growth regulator application in a field environment, where plants have to cope with multiple biotic and abiotic stresses, may implement the perspectives for the use of these substances in the control of fruit ripening.

Upgrading Bio-Platform Molecules in the Gas-Phase: From Levulinic Acid to Bio-Chemicals

Levulinic acid (LA) is a polyfunctional molecule obtained from biomass. Because of its structure, the United States Department of energy classified LA as one of the top 12 building block chemicals. Typically, it is valorized through chemical reduction to γ-valerolactone (GVL). It is usually done with H2 in batch systems with high H2 pressures and noble metal catalysts, making it expensive and less applicable. Therefore, alternative approaches such as catalytic transfer hydrogenation (CTH) through the Meerwein–Ponndorf–Verley (MPV) reaction over heterogeneous catalysts have been studied. This uses organic molecules (alcohols) which act as a hydride transfer agent (H-donor), to reduce molecules containing carbonyl groups. Given the stability of the intermediate, reports have shown the batch liquid-phase CTH of levulinate esters with secondary alcohols, and remarkable results (GVL yield) have been obtained over ZrO2, given the need of a Lewis acid (LASites) and base pair for CTH. However, there were no reports of the continuous gas-phase CTH of levulinate esters. Therefore, high surface area ZrO2 was tested for gas-phase CTH of methyl levulinate (ML) using ethanol, methanol and isopropanol as H-donors. Under optimized conditions with ethanol (250 ℃), the reaction is selective towards GVL (yield 70%). However, heavy carbonaceous materials over the catalyst surface progressively blocked LASites changing the chemoselectivity. The in situ regeneration of the catalyst permitted a partial recovery of the LASites and an almost total recovery of the initial catalytic behavior, proving the deactivation reversible. Tests with methanol were not promising (ML conversion 35%, GVL yield 4%). As expected, using isopropanol provided complete conversion and a GVL yield of 80%. The reaction was also tested using bioethanol derived from agricultural waste. In addition, a preliminary study was performed for the hydrogenolysis of polyols to produce bioethanol, were Pd-Fe catalyst promoted the ethanol selective (37%) hydrogenolysis of glycerol.