Human serum transferrin (hTF) is a bilobal glycoprotein that plays a central role in iron metabolism. Each lobe of hTF (N- and C-lobe) can reversibly bind a single ferric iron. Iron binds to hTF at neutral pH in the plasma; diferric hTF binds to specific hTF receptors (TFR) on the cell surface and the complex undergoes receptor mediated endocytosis. The pH within the endosome is lowered to ~5.6 and iron is released from hTF. Apo hTF remains bound to the TFR and recycles back to the cell surface. Upon fusion with the plasma membrane, apo hTF dissociates from the TFR and is free to bind more iron and continue the cycle. The iron release process is complicated by various factors which include pH, anions, a chelator, lobe-lobe cooperativity and interaction with the TFR. All of these influence iron release in a complex manner. Because they are intricately linked, it is difficult to determine the effect of any single parameter. We have utilized stopped-flow and steady-state fluorescence and urea gel electrophoresis to dissect the iron release process as a function of lobe-lobe interactions, the presence of the TFR, and changes in pH and salt concentration. Application of recombinant protein production and site-directed mutagenesis has allowed us to generate a variety of hTF constructs in which the iron status of each lobe is completely controlled. Thus, we have created authentic monoferric hTFs unable to bind iron in one lobe, diferric hTFs with iron locked in one lobe and diferric hTF in which iron can be removed from both lobes. Importantly, we have produced the soluble portion of the TFR (sTFR) to analyze interactions between hTF and the sTFR and to monitor iron release from hTF/sTFR complexes. Together, we are able to provide a more precise picture of iron release from the two lobes of hTF in the presence and absence of the TFR. Steady-state fluorescence emission scans and urea gel electrophoresis provide a qualitative evaluation of the iron status of each construct after a predetermined incubation in iron removal buffer (i.e. an endpoint). However, these techniques do not provide information regarding the kinetic pathway to reach that endpoint. Combined with stopped-flow fluorescence time-based kinetics, a more precise assessment of the iron release process has been obtained. We have determined that changes in pH and salt affect endpoint iron release from the C-lobe, but not the N-lobe, however, the kinetics of iron release from both lobes are highly sensitive to pH and salt. Kinetic analysis in the absence and presence of the sTFR reveals the complexity of the iron release process. In the absence of the sTFR, the kinetics of iron release are insensitive to the iron status of the opposite lobe. However, in the presence of the sTFR, the kinetics of iron release from both lobes are affected by the iron status of the opposite lobe. Determination of conformational changes induced by anion binding, lobe-lobe communication and sTFR interactions have now been confidently assigned. We have created kinetic models of iron release from diferric hTF ± the sTFR and incorporated specific events pertaining to anion binding, lobe-lobe communication and conformational changes associated with sTFR interactions. We provide irrefutable evidence that a critical role of the sTFR is to accelerate the rate of iron release from the C-lobe, while decreasing the rate of iron release from the N-lobe such that the two lobes effectively release iron on a time scale relevant to one cycle of endocytosis.

Global sea levels are expected to rise as a result of climate change, which will lead to the inundation and erosion of low lying coastal areas and accelerate the intrusion of seawater into sub-surface sediments. Many of the UK’s legacy nuclear facilities are located in close proximity to the shore, raising questions regarding the potential mobilisation of radionuclides during sea level rise. Here batch and column experiments were used to simulate and investigate the effect of these processes on the mobilisation of key radionuclides Tc, 90Sr and U from oxic and reduced sediments under sea level rise scenarios. Strontium-90 was rapidly mobilised from exchangeable surface sites from oxic sediments during inundation and erosion scenarios with seawater (≈ 60%). Strontium release was driven by ion exchange between Sr90 and Mg2+ cations present in high concentrations in seawater. Uranium release from oxic and reduced sediments was kinetically controlled, characterised by slow release from a range of binding sites, promoted by the formation of U-carbonate complexes. Uranium mobilisation was slower from reduced sediments compared with oxic sediments under seawater flow conditions; therefore reduced sediments would act as a longer term source of U to marine environments. Release was more extensive from initially nitrate reducing sediments (53%) compared with extensively iron reducing sediments (38%), with the difference in release explained by the longer contact period of U(VI) with the iron reducing sediment relative to the nitrate reducing sediment which would lead to slower desorption. Additionally, U(IV) species would be released more slowly than U(VI) species sorbed to the sediments. The release of Tc was dependent on sediment re-oxidation coupled with the oxidation of Tc(IV) to Tc(VII). Batch experiments showed that only a small proportion of Tc was rapidly (within 5 days) released from the sediments into seawater and groundwater which suggests that the majority of any Tc(IV) contamination will be released slowly as the seawater plume migrates through the sediments. Technetium release was slowest, and ultimately limited to the greatest extent (17%), in initially Fe-reducing sediments, when they were re-oxidised in seawater. Thus the cycling of iron and the impact of the water chemistry on iron mineralogy were important for hindering Tc release. Column experiments showed that iron minerals were less effective at retarding Tc release under flow-through conditions. Kinetically controlled and solubility limited Fe dissolution led to on-going Tc release from the sediments, i.e. the retarding effect of iron phases was temporary and significantly more Tc was mobilised (79-93%) compared with the batch experiments (17-45%). This study has shown for the first time that radionuclides will be released from reduced and oxic sediments as a result of future sea level rise. Contaminated sediments have the potential to act as a secondary source of radionuclide contamination entering the marine environment from coastal nuclear sites. This information is essential when siting new nuclear facilities and when developing effective remediation, decommissioning and management strategies for legacy coastal sites.

No description available.

Tesis por compendio / [ES] El uso masivo de plásticos sintéticos y su impacto medioambiental obliga a buscar alternativas biodegradables para el envasado de los alimentos,etapa necesaria para su adecuada conservación.Así mismo,la necesidad de incrementar la vida útil de los alimentos ha despertado gran interés en el desarrollo de materiales activos(antimicrobianos y antioxidantes)que mantengan su calidad y seguridad por más tiempo,mediante el uso de compuestos de origen natural,seguros para el consumidor.En este sentido,el desarrollo de materiales biodegradables activos para el envasado de alimentos constituye hoy en día un reto importante para la industria alimentaria.En la presente Tesis Doctoral,se ha estudiado la encapsulación de carvacrol mediante el electroestirado o extensión y secado de diferentes disoluciones poliméricas con carvacrol.Se han utilizado polímeros biodegradables portadores de diferente polaridad(almidón termoplástico:TPS,polivinil-alcohol:PVA, policaprolactona:PCL o ácido poliláctico:PLA)disueltos en el solvente adecuado,con el fin de obtener capas activas.Estas capas se han combinado con otras de polímeros con propiedades complementarias,para obtener laminados activos adecuados para el envasado de alimentos.Los laminados combinaron polímeros polares(TPS o PVA)y poliésteres no polares(PCL o PLA)incorporando el carvacrol en una de las capas.Se evaluó la cinética de liberación del activo,así como la acción antimicrobiana de los materiales obtenidos.Los laminados se caracterizaron en su funcionalidad como material de envase(prop. de barrera,mecánicas u ópticas)así como en su estructura y comportamiento térmico.Los estudios de encapsulación revelaron un mayor potencial encapsulante del carvacrol para los polímeros no polares(PCL;PLA),aunque el PVA mostró también una buena afinidad con el compuesto activo.La matriz de PVA mostró una mayor retención de carvacrol mediante electroestirado de sus disoluciones acuosas que por extensión y secado,sin necesidad de adición de tensoactivos como el Tween85.Para la encapsulación en PLA,se usaron mezclas binarias de solventes aptos para contacto con los alimentos(acetato de etilo y DMSO).En este caso,se obtuvo una mayor eficiencia encapsulante del PLA en los materiales obtenidos por extensión y secado que en los electroestirados.La cinética de liberación del carvacrol de las fibras de PCL explicó el mayor efecto antibacteriano contra E.coli,y el escaso efecto antilisteria.La velocidad de liberación del activo aumentó cuando disminuyó la polaridad de los simulantes alimentarios, mostrando una liberación completa en los sistemas apolares,pero solo hasta 75% en los sistemas acuosos,que requerirían una mayor proporción del activo en el envase para potenciar su efectividad.La combinación de láminas de TPS con fibras de PCL cargadas con carvacrol dio lugar a materiales con una permeabilidad al vapor de agua mejorada,en comparación con los films de almidón,sin efectos relevantes sobre las otras propiedades funcionales estudiadas.Cuando los laminados se probaron in vitro contra cepas G(+) y G(-) mostraron un efecto antibacteriano similar al de las fibras de PCL con carvacrol,pero retrasado en el tiempo.Los estudios de desintegración-biodegradación de los laminados almidón-PCL revelaron que las películas con carvacrol afectaron la actividad del inóculo del compost,disminuyendo ligeramente la biodegradabilidad de las películas,pero alcanzando valores de desintegración similares(75-80%)a las muestras libres de carvacrol.Se obtuvieron también laminados de PLA y PVA mediante la extensión y secado de disoluciones acuosas de PVA con carvacrol.La superficie del PLA fue sometida a aminolización a fin de mejorar la extensibilidad de las disoluciones acuosas.A pesar del incremento de la componente polar de la energía superficial del PLA y su mejorada humectabilidad con las soluciones de PVA,estas bicapas no mostraron una mejora significativa en las propied / [CA] L'ús massiu de plàstics sintètics i el seu impacte mediambiental obliga a buscar alternatives biodegradables per a l'envasament dels aliments necessari per a la seua conservació.Així mateix,la necessitat d'incrementar la vida útil dels aliments ha despertat gran interés en el desenvolupament de materials actius(antimicrobians i antioxidants)que mantinguen la seua qualitat i seguretat per més temps,per mitjà de l'ús de compostos d'origen natural,segurs per al consumidor.En este sentit,el desenvolupament de materials biodegradables actius per a l'envasament d'aliments constituïx un repte important per a la indústria alimentària.En la present Tesi Doctoral,s'ha estudiat l'encapsulació de carvacrol per mitjà de l'electroestirat o extensió i assecat de diferents dissolucions polimèriques amb carvacrol.S'han utilitzat polímers biodegradables portadors de diferent polaritat(midó termoplàstic:TPS, polivinil-alcohol:PVA, policaprolactona:PCL o àcid poliláctic:PLA)dissolts en el solvent adequat,a fi d'obtindre capes actives.Estes s'han combinat amb altres de polímers amb propietats complementàries,per a obtindre laminats actius adequats per a l'envasament d'aliments.Els laminats van combinar polímers polars(TPS o PVA)i poliésters no polars(PCL o PLA)incorporant el carvacrol en una de les capes.Es va avaluar la cinètica d'alliberament de l'actiu,així com l'acció antimicrobiana dels materials obtinguts.Els laminats es van caracteritzar en la seua funcionalitat com a material d'envàs(propietats de barrera, mecàniques o òptiques),així com en la seua estructura i comportament tèrmic.Els estudis d'encapsulació van revelar un major potencial encapsulant del carvacrol per als polímers no polars(PCL i PLA),encara que el PVA va mostrar també una bona afinitat amb el compost actiu.La matriu de PVA va mostrar una major retenció de carvacrol per mitjà d'electroestirat de les seues dissolucions aquoses que per extensió i assecat,sense necessitat d'addició de tensioactius com el Tween 85.Per a l'encapsulació en PLA,es van usar mescles binàries de solvents aptes per a contacte amb els aliments(acetat d'etil i DMSO).Es va obtindre una major eficiència encapsulant del PLA en els materials obtinguts per extensió i assecat que en els electroestirats.La cinètica d'alliberament del carvacrol de les fibres de PCL va explicar el major efecte antibacterià contra Escherichia coli,i l'escàs efecte antilisteria.La velocitat d'alliberament de l'actiu va augmentar quan va disminuir la polaritat dels simulants alimentaris,mostrant un alliberament complet en els sistemes no polars, però només fins a un 75% en els sistemes aquosos,que requeririen una major proporció de l'actiu en l'envàs per a potenciar la seua efectivitat.La combinació de làmines de TPS amb fibres de PCL carregades amb carvacrol va donar lloc a materials amb una permeabilitat al vapor d'aigua millorada,en comparació amb els films de midó, sense efectes rellevants sobre les altres propietats funcionals.Quan els laminats es van provar in vitro contra ceps Gram(+) i Gram(-) van mostrar un efecte antibacterià semblant al de les fibres de PCL amb carvacrol,però retardat en el temps.Els estudis de desintegració-biodegradació dels laminats midó-PCL van revelar que les pel·lícules amb carvacrol van afectar l'activitat de l'inocule del compost,disminuint lleugerament la biodegradabilitat,però aconseguint valors de desintegració semblants(75-80%)a les mostres lliures de carvacrol.Es van obtindre també laminats de PLA i PVA per mitjà de l'extensió i assecat de dissolucions aquoses de PVA amb carvacrol.La superfície del PLA va ser sotmesa a aminolizatció a fi de millorar l'extensibilitat de les dissolucions aquoses.A pesar de l'increment de la component polar de l'energia superficial del PLA i la seua millorada mullabilitat amb les solucions de PVA,estes bicapes no van mostrar una millora significativa en les propietats mecàniques i de barrera / [EN] The massive use of synthetic plastics and their environmental impact makes necessary the search for biodegradable alternatives for food packaging. Likewise, the need to increase the shelf life of food has aroused great interest in the development of active materials (antimicrobial and antioxidant) that maintain food quality and safety for longer periods of time through the use of compounds of natural origin, safe for the consumer. In this sense, the development of active biodegradable materials for food packaging is both a major imperative and challenge for the food industry today. In the present Doctoral Thesis, the encapsulation of carvacrol has been studied by means of the electrospinning or casting of different polymeric solutions with carvacrol. Biodegradable polymers with different polarities (thermoplastic starch: TPS, poly(vinyl-alcohol): PVA, poly-(¿-caprolactone): PCL or poly(lactic acid): PLA) dissolved in the appropriate solvent have been used to obtain active layers. These have been combined with other polymers with complementary properties, to obtain active laminates suitable for food packaging. The laminates combined polar polymers (TPS or PVA) and non-polar polyesters (PCL or PLA) incorporating carvacrol in one of the layers. The release kinetics of the active ingredient was evaluated, as well as the antimicrobial action of the materials obtained. The laminates were characterized in their functionality as a packaging material (barrier, mechanical or optical properties), as well as in their structure and thermal behaviour. Encapsulation studies revealed a higher encapsulating potential of carvacrol for non-polar polymers (PCL and PLA), although PVA also showed a good affinity with the active compound. The PVA matrix showed a higher retention of carvacrol by electrospinning of its aqueous solutions than by casting, without the need for addition of surfactants such as Tween 85. For the encapsulation in PLA, binary mixtures of solvents suitable for food contact (ethyl acetate and DMSO) were used. A higher encapsulation efficiency of PLA was obtained in the materials produced by casting than by electrospinning. The carvacrol release kinetics of PCL fibres explained the higher antibacterial effect against Escherichia coli and the lower antilisterial effect. The release ratio of the active ingredient increased when the polarity of the food simulants decreased, showing a complete release in non-polar systems and only up to 75% in aqueous systems that would require a higher proportion of the active ingredient in the packaging material to enhance its effectiveness. The combination of TPS films with carvacrol loaded PCL fibres resulted in materials with improved water vapour permeabilities, compared to starch films, with no relevant effects on the other functional properties. When the laminates were tested in vitro against Gram (+) and Gram (-) strains, they showed a similar antibacterial effect to that of PCL fibres with carvacrol, but delayed in time. Disintegration-biodegradation studies of PCL-starch laminates revealed that carvacrol films affected the activity of the compost inoculum, slightly decreasing the biodegradability of the laminates, but reaching similar disintegration values (75-80%) to the carvacrol-free samples. PLA and PVA laminates were also obtained by casting aqueous PVA solutions with carvacrol. The surface of PLA was submitted to aminolization in order to improve the extensibility of the aqueous solutions. Despite the increase in the polar component of the PLA surface energy and its improved wettability with PVA solutions, these bilayers did not show significant improvement in mechanical and barrier properties over the PLA monolayers. / The authors would like to thank the Ministerio de Economia y Competitividad of Spain, for funding this study as part of projects AGL2013-42989-R and AGL2016-76699-R and predoctoral research grant # BES-2014-068100. / Tampau, A. (2020). Carvacrol encapsulation by electrospinning or solvent casting to obtain biodegradable multilayer active films for food packaging applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/140313 / TESIS / Compendio

The objectives of this project encompass the design and development of a drug delivery system to continuously deliver therapeutic agents from the stomach to the proximal region of the intestine. The delivery system designed would have sufficient gastric residence time together with near zero-order release kinetics. The physicochemical properties pertaining to the formulation development of the model drug (alfuzosin HCl) were evaluated. Excipients were selected based on the studies of their physicochemical properties and compatibility with the active ingredient. Gastro-retentive dosage forms have been the topic of interest in recent years as a practical approach in drug deliveries to the upper GI tract or for release prolongation and absorption. These dosage forms are particularly suitable for drugs that have local effects on the gastric mucosa in the stomach. Other candidates include drugs that are likely to be absorbed in the upper small intestine, or drugs that are unstable in basic environment of distal intestine and colon or those with low solubility at elevated pH conditions (i.e. weak bases). To develop a gastro-retentive delivery system the following steps were taken. First, to investigate the possible incompatibility issues between the model drug and excipients to be used for the delivery system. Stability and physicochemical properties of the active agent and its mixture with excipients were studied using analytical techniques such as Raman spectroscopy and Differential scanning calorimetry (DSC). No incompatibility issues were detected. Second, Kollidon SR as a relatively new release-rate controlling polymer was incorporated in the final formulation. For solid dosage form the ability of the final powder mix to flow well during manufacturing and the intrinsic characteristics that make it compressible are critical. The in-depth compaction study of Kollidon SR was assessed with the help of a compaction simulator. The flowability, swelling and erosion behavior together with release-rate retarding properties of Kollidon SR were also assessed. The final oral delivery system was based on Kollidon SR and Polyethylene Oxide (PEO) 303 as a monolithic matrix system. The noneffervescent monolithic matrix was made by direct compression. In vitro evaluation of the designed system released the active content in a near zero manner. The dosage form was bouyant in pH 2.0 acidic buffer with no floatation lag time which minimizes the possibility of early gastric emptying. / Pharmaceutics

Liposomal delivery systems hold considerable promise for improvement of cancer therapy provided that critical formulation design criteria can be met. The main objective of the current project was to enable quality by design in the formulation of liposomal delivery systems by developing comprehensive, mechanism-based mathematical models of drug loading, binding and release kinetics that take into account not only the therapeutic requirement but the physicochemical properties of the drug, the bilayer membrane, and the intraliposomal microenvironment. Membrane binding of the drug affects both drug loading and release from liposomes. The influence of bilayer composition and phase structure on the partitioning behavior of a model non-polar drug, dexamethasone, and its water soluble prodrug, dexamethasone phosphate, was evaluated. Consequently, a quantitative dependence of the partition coefficient on the free surface area of the bilayer, a property related to acyl chain ordering, was noted. The efficacy of liposomal formulations is critically dependent on the drug release rates from liposomes. However, various formulation efforts to design optimal release rates are futile without a validated characterization method. The pitfalls of the commonly used dynamic dialysis method for determination of apparent release kinetics from nanoparticles were highlighted along with the experimental and mathematical approaches to overcome them. The value of using mechanism-based models to obtain the actual rate constant for nanoparticle release was demonstrated. A novel method to improve liposomal loading of poorly soluble ionizable drugs using supersaturated drug solutions was developed using the model drug AR-67 (7-t-butyldimethylsilyl-10-hydroxycamptothecin), a poorly soluble camptothecin analogue. Enhanced loading with a drug to lipid ratio of 0.17 was achieved and the rate and extent of loading was explained by a mathematical model that took into account the chemical equilibria inside and outside the vesicles and the transport kinetics of various permeable species across the lipid bilayer and the dialysis membrane. Tunable liposomal release kinetics would be highly desirable to meet the varying therapeutic requirements. A large range of liposome release half-lives from 1 hr to 892 hr were obtained by modulation of intraliposomal pH and lipid composition using dexamethasone phosphate as a model ionizable drug. The mathematical models developed were successful in accounting for the change in apparent permeability with change in intraliposomal pH and bilayer free surface area. This work demonstrates the critical role of mechanism-based models in design of liposomal formulations.

Des particules constituées d’un cœur polymère polylactide (PLA), recouvertes d’une couche de polysaccharide adsorbé physiquement (dextrane hydrophobisé par des chaînes alkyle en C6, DexC6) et contenant des substances actives (SA) de type polyphénolique ont été élaborées par différents procédés physico-chimiques discontinus (nanoprécipitation et émulsion-évaporation de solvant) ou continus (procédé microfluidique d’émulsion-diffusion de solvant). L’extrapolation du procédé de nanoprécipitation de l’échelle laboratoire (25 mL) à l’échelle pilote (1 L) a été examinée. Ces particules étaient destinées au traitement des milieux aquatiques, pour la lutte contre le développement des cyanobactéries et des algues. Dans le but de maîtriser les caractéristiques des particules élaborées (distribution de taille, stabilité colloïdale, rendement d’encapsulation en SA ...), l’influence de paramètres physico-chimiques a été étudiée (concentration du PLA dans la phase organique, concentration du DexC6 dans la phase aqueuse, rapport volumique des deux phases, fraction massique SA/PLA …). Les procédés mis au point ont permis d’obtenir des particules dont les diamètres moyens allaient de 0,1 µm à 1 mm, avec des distributions granulométrique bien maîtrisées. Ces objets ont été caractérisés en termes de taux de recouvrement en dextrane, de quantité de SA encapsulée et de morphologie. La stabilité colloïdale des suspensions de nanoparticules a été examinée dans des milieux de force ionique variable. Par ailleurs, nous avons vérifié la possibilité de redisperser les suspensions de particules après lyophilisation. Pour les nanoparticules, l’addition d’un cryoprotecteur s’est avérée indispensable. Les cinétiques de libération des substances actives à partir des particules nano- et micrométriques ont également été suivies et les phénomènes limitant leur libération ont été identifiés.Enfin, des essais sur des milieux de culture contenant des cyanobactéries ont été réalisés. Ils ont montrés que la libération des SA conduisait à des effets algistatiques ou algicides selon les quantités utilisées. / Polysaccharide-covered polyester particles were prepared. The core of particles was made of polylactic acid (PLA) while their surface was covered by dextran chains via the use of water-soluble randomly hydrophobized dextran (DexC6) as a polymeric stabilizer. Polyphenolic active substances were encapsulated inside those particles. Polyphenol loaded PLA particles were designed for preventing cyanobacterias and algae proliferation in aquatic media. Conventional batch processes (nanoprecipitation or emulsion-solvent evaporation) and continuous processes (emulsion-solvent diffusion in microfluidics) were used to elaborate particles with average diameters ranging between 0.1 µm and 1 mm. The scale up of nanoprecipitation from lab scale (25 mL) to pilot scale (1 L) was also studied. The formulation parameters (PLA concentration in the organic phase, DexC6 concentration in the aqueous phase, aqueous phase to organic phase volume ratio, active substance weight fraction…) were optimized in order to obtain particles with well controlled characteristics (average diameter and size distribution, colloidal stability, encapsulation efficiency …). Loaded particles elaborated by different processes were characterized with regards to DexC6 surface coverage, colloidal stability at various ionic strengths, morphology and encapsulation efficiency. We also investigated the re-dispersion ability of particle suspensions after freeze drying and we showed that the use of a cryoprotectant was required in case of nanoparticles. The release of polyphenolic molecules from the elaborated polymeric nano- and microparticles was studied and limiting steps were identified. Finally, the cytotoxicity of nanoparticles toward cyanobacterias was evaluated. It was demonstrated that anti-algal effects were observed depending on the added quantities.

Η καλσείνη (calcein) γνωστή και με την αγγλική ορολογία Fluorexon/Fluorescein είναι μια μικρού μοριακού βάρους υδατοδιαλυτή ουσία και χρησιμοποιείται ως μόριο- πρότυπο μικρού υδατοδιαλυτού φαρμάκου, σε πλήθος εφαρμογών τόσο στο τομέα της φαρμακευτικής όσο και στο τομέα της χημείας. Η χρησιμότητα της έγκειται στο γεγονός ότι παρουσιάζει φθορισμό που αποσβένειται σε υψηλές συγκεντρώσεις(100mM) και της εύκολης παρακολούθησης της αποδέσμευσης της από σωματιδιακά συστήματα χορήγησης φαρμάκων. Τα λιποσώματα είναι καθορισμένα λιπιδικά κυστίδια με μέγεθος που κυμαίνεται μεταξύ 0,05-5μm και βρίσκονται εδώ και πολλά χρόνια στο επίκεντρο του ερευνητικού ενδιαφέροντος, ως φορείς φαρμάκων και βιοδραστικών ενώσεων καθώς και για την βελτίωση της απόδοσής τους στους οργανισμούς. Τα λιποσώματα μελετώνται για την απόδοση βιολογικά δραστικών ουσιών κυρίως για τους εξής λόγους: 1. την αδυναμία αυτών των ουσιών να επιτύχουν την επιθυμητή συγκέντρωση στην επιθυμητή περιοχή, 2. την κυτταροτοξικότητά τους και 3. προβλήματα που σχετίζονται με τη χορήγησή τους (για παράδειγμα χαμηλή διαλυτότητά τους σε κατάλληλο φορέα). Σκοπός της παρούσας εργασίας είναι, η μαθηματική μοντελοποίηση και η μελέτη της κινητικής αποδέσμευσης των μορίων της καλσείνης, που λειτουργούν ως μόρια- πρότυπου υδατοδιαλυτού φαρμάκου, σε συστήματα λιποσωμάτων τα οποία παρασκευάστηκαν σε διαφορετικές λιπιδικές συστάσεις με την επίδραση της χοληστερόλης και της πολυαιθυλενογλυκόλης να καθορίζουν τις φυσικοχημικές τους ιδιότητες και τις αλληλεπιδράσεις μεταξύ των μορίων της καλσείνης. Ειδικότερα, παρασκευάστηκαν λιποσώματα SUV με την μέθοδο του λεπτού υμενίου, στα οποία εγκλωβίστηκε καλσείνη σε υψηλή συγκέντρωση (100mM) με χρήση ακίδας υπερήχων για περίπου 15 λεπτά, σε συστάσεις (PC, PC/Chol 4:1, 2:1 και 1:1 mole/mole) καθώς και (PC/Chol/PEG 2:1:0.04, 2:1:0.08, 2:1:0.16 και 2:1:0.32 mole/mole/mole). Η μελέτη των φυσικοχημικών χαρακτηριστικών των συστημάτων αυτών όπως είναι η μέση υδροδυναμική διάμετρος, η πολυδιασπορά και το ζ-δυναμικό τους, πραγματοποιήθηκε με τη χρήση DLS (Dynamic Light Scattering Nano-ZS Malvern UK) στους 25°C. Ο προσδιορισμός της ποσοστιαίας απελευθέρωσης της καλσείνης (% Cumulative calcein release) έγινε μετά από επώαση των δειγμάτων στους 37°C μέσα σε διάστημα 32h, υπολογίζοντας το ποσοστό συγκράτησης της καλσείνης (Latency %) σε καθορισμένα χρονικά διαστήματα με μέτρηση του φθορισμού (FL) της ουσίας. Στη συνέχεια τα αποτελέσματα αποδόθηκαν αναλυτικά σε διαγράμματα LATENCY% και RETENTION% σε συνάρτηση με το χρόνο με σκοπό να δημιουργηθεί ένα ολοκληρωμένο προφίλ για κάθε λιποσωμική δομή. Τέλος κατασκευάστηκαν διαγράμματα RELEASE% σε συνάρτηση με το χρόνο. Όπως αναμενόταν η διπλοστοιβάδα των PEG-λιποσωμάτων είναι πιο σταθερή σε σχέση με την διπλοστοιβάδα των λιποσωμάτων χωρίς PEG με αποτέλεσμα την ελάττωση της διαπερατότητας της λιπιδικής μεμβράνης. Η ίδια υπόθεση έγινε και στην περίπτωση που στα λιποσώματα προστέθηκε χοληστερόλη, όπου η αύξηση της συγκέντρωσης της χοληστερόλης οδήγησε σε αύξηση της ακεραιότητας της διπλοστοιβάδας τους. Τέλος μια εξίσωση-πρότυπο τριών παραμέτρων κατασκευάστηκε και τροποποιήθηκε κατάλληλα έτσι ώστε να περιγράψει με ακρίβεια τα πειραματικά αποτελέσματα. Οι παράμετροι Kon, Koff περιγράφουν την σύνδεση και την αποσύνδεση των μορίων της καλσείνης από τη λιποσωμική δομή και σε συνδυασμό με την παράμετρο Ks καθορίζουν την απελευθέρωση των μορίων της. Στη συνέχεια χρησιμοποιήθηκε η συνάρτηση Weibull, μια σαφώς απλούστερη συνάρτηση σε σχέση με την συνάρτηση τριών παραμέτρων που χρησιμοποιήσαμε αρχικά, έτσι ώστε να καθοριστεί ενδελεχώς ο ρόλος της διάχυσης στα συστήματα λιποσωμάτων που παρασκευάσαμε. Επόμενο βήμα ήταν η επεξεργασία των δύο αυτών συναρτήσεων με την τεχνική Monte Carlo, ώστε να εξαχθεί μια εκτίμηση για την τυπική απόκλιση των παραμέτρων των συναρτήσεων. Τα αποτελέσματα υπέδειξαν την ιδανικότερη τεχνική/μέθοδο προσαρμογής που θα μπορούσε να χρησιμοποιηθεί για κάθε λιποσωμική δομή που παρασκευάσαμε. / Calcein also known as Fluorexon/Fluorescein is a water-soluble substance with low molecular weight. Calcein used as a model-molecule of highly water-soluble drugs in a wide range of applications in pharmaceutics and chemistry. It’s usefulness is due to the fact that fluorescence self-quenches in high concentrations and so it’s release from liposome systems could monitor with ease. Liposomes are vesicles with particle size from 0.05 to 5μm. Liposome structures are at the heart of scientific interest for many years, as they are used as widely in drug delivery systems and have enhanced their performance in biota. Studies in liposomes, focused on the performance of bio-active substances for the following reasons: 1. Weakness of them to achieve the appropriate concentration in the appropriate area. 2. High cytotoxicity and 3. Problems that appears during their administration (f.i. low solubility). The objective of the current study, is to mathematically model and study the release kinetics of calcein molecules (that work as a hydrophilic drug model) from liposome structures with different compositions when cholesterol and polyethylene-glycol determines physicochemical properties and retentions of calcein molecules. Specifically, SUV-liposomes prepared with the thin-film hydration method which encapsulate calcein molecules of high concentration (100mM), were used. Their size was decreased by applying probe sonication for 15min. Phosphatidylcholine (PC), Cholesterol (Chol) and polyethelene-glycol 2000 (PEG) were used in different concentrations (PC, PC/Chol 4:1, 2:1 and 1:1 mole/mole) and (PC/Chol/PEG 2:1:0.04, 2:1:0.08, 2:1:0.16 and 2:1:0.32 mole/mole/mole). Study of vesicle physicochemical characteristics such as z-size, pdi and z-potential, was carried out by DLS (Nano-ZS Malvern UK) at 25°C. Determination of the percentage of Cumulative calcein release taking place during incubation of vesicles at 37°C for up to 32h. Fluorescence Intensity (FL) measurements were performed to estimate the restraint percentage of calcein molecules. Subsequently, final results were attributed to analytical plots (LATENCY % AND RETENTION % with time), in order to create a completed profile for every liposome structure. Finally, results summarized into release curves dependent on time. As expected, the lipid bilayer of PEGylated liposomes was more stable than bilayer of liposomes without PEG coating and as a result the permeability of the later formulation decreased. This was also the case when Chol was included in the liposome membrane; vesicle integrity increased with increasing Chol concentration. A model three-parameter equation was used and modified in appropriately in order to describe the experimental results with accuracy. Parameters Kon, Koff (rate constants of association and disassociation, respectively) and Ks were used to describe the cumulative release of calcein over time, for each formulation study. Subsequently, we use Weibull function, clearly a simpler function in relation to the three-parameters function used initially, in order to determine thoroughly the role of diffusion systems liposome preparations. Next step was the processing of these two functions with Monte Carlo technique in order to extract an estimation of the Standard Deviation (SD) of the parameters of the functions. Results indicated the ideal technique/method of fitting, that could be used for each liposomal structure prepared.

Advancements in nanoparticle drug delivery of anticancer agents require mathematical models capable of predicting in vivo formulation performance from in vitro characterization studies. Such models must identify and incorporate the physicochemical properties of the therapeutic agent and nanoparticle driving in vivo drug release. This work identifies these factors for two nanoparticle formulations of anticancer agents using an approach which develops mechanistic mathematical models in conjunction with experimental studies. A non-sink ultrafiltration method was developed to monitor liposomal release kinetics of the anticancer agent topotecan. Mathematical modeling allowed simultaneous determination of drug permeability and interfacial binding to the bilayer from release data. This method also quantified the effects of topotecan dimerization and surface potential on total amount of drug released from these liposomal formulations. The pH-sensitive release of topotecan from unilamellar vesicles was subsequently evaluated with this method. A mechanistic model identified three permeable species in which the zwitterionic lactone form of topotecan was the most permeable. Ring-closing kinetics of topotecan from its carboxylate to lactone form were found to be rate-limiting for topotecan drug release in the neutral pH region. Models were also developed to non-invasively analyze release kinetics of actively-loaded liposomal formulations of topotecan in vivo. The fluorescence excitation spectra of released topotecan were used to observe release kinetics in aqueous solution and human plasma. Simulations of the intravesicular pH in the various release media indicated accelerated release in plasma was a consequence of increased intravesicular pH due to ammonia levels in the plasma instead of alterations in bilayer integrity. Further studies were performed to understand the roles of dimerization, ion-pairing, and precipitation on loading and release kinetics obtained from actively-loaded topotecan. Extension of this type of modeling for other types of nanoparticles was illustrated with doxorubicin-conjugated polymeric micelles. Mathematical modeling of experimental studies monitoring doxorubicin release identified conjugation stability during storage, hydrazone hydrolysis kinetics, and unconjugated doxorubicin partitioning affected micellar doxorubicin release. This work identifies several of the key parameters governing drug release from these liposomal and micellar nanoparticles and lays the framework for future development of in vivo release models for these formulations.

Submitted by MARCIA ROVADOSCHI (marciar@unifra.br) on 2018-08-15T13:27:18Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_JerusaGoiBarrios.pdf: 2507299 bytes, checksum: b0357f55d1ddf8dd63d987592cf16a6e (MD5) / Made available in DSpace on 2018-08-15T13:27:18Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_JerusaGoiBarrios.pdf: 2507299 bytes, checksum: b0357f55d1ddf8dd63d987592cf16a6e (MD5) Previous issue date: 2010-06-30 / Acne is one of the most common inflammatory conditions affecting the skin. There are several drugs to treat it, but despite the benefits of these treatments in their free form, there are common side effects to them, especially when applied topically. Among these drugs is the adapalene with comedolitic action and effects on the abnormal process of keratinization and epidermal differentiation, phenomena present in acne vulgaris. This study aimed to prepare polymer nanocapsules of adapalene through the method of interfacial deposition of preformed polymer using different oil cores (tea tree oil and Miglyol®). The suspensions were characterized by determining the pH, particle diameter, polidispersion rate, zeta potential, association rate and dosage of the drug. The stability was determined at different temperatures and under light UVA. In vitro release studies and analysis of mathematical modeling of kinetic release profiles were carried out by comparing suspensions containing adapalene polymer nanocapsules and nanodispersions and without the presence of the polymer. The formulations were stored at room temperature (25 ° C), refrigerator (-4 ° C) and oven (40 ° C) for 3 months and analyzed at 0, 7, 15, 30, 60 and 90 days after preparation. Both suspensions containing Miglyol® polymer nanocapsules (NC-AD-Miglyol®) as the tea tree oil polymer nanocapsules (NC-AD-tea tree oil) showed acidic pH, particle diameter below 300 nm and zeta potential negative. The rate of association of adapalene in the NC-AD-tea tree oil was 95.4% while the NC-AD-Miglyol® was 84.1%. The dosage of the drug showed that the NCAD- tea tree oil exerts a greater stabilizing effect than the other formulations. The shelf life estimated for the NC-AD-tea tree oil was higher when compared to nanodispersion (ND) and NC-AD-Miglyol®. Mathematical modeling showed that the ND and NC-AD-Miglyol® followed a kinetic profile, according to the mono-exponential model with half-lives of 3.53 and 8.43 hours. On the other hand, NC-AD-tea tree oil suspension followed a bi-exponential, model with half-lives of 4.07 hours for the fast phase and 230.6 hours for the sustained phase. Therefore, we can say that the adapalene formulation NC-AD-Miglyol® locates largely more externally in the polymer nanocapsule, while in the NC-AD-tea tree oil, it is dissolved in the oil core of the polymer nanocapsule, suggesting a sustained release. We evaluated the photostability of adapalene nanocoated with Miglyol® oil and tea tree oil under UVA irradiation, and concluded that the nanoencapsulation with tea tree oil increases the stability of the active, offering increased protection it from degradation. In analysis by multiple scattering of light, the suspensions showed a tendency of sedimentation, but the NC-ADMiglyol ® proved to be more likely to destabilization. The validation of the method was satisfactory for all parameters analyzed. Though the results obtained, it can be concluded that the suspension containing NC-AD-tea tree oil showed better physical and chemical characteristics and stability, representing best technological feasibility fot the pharmaceutical area. / A acne é uma das condições inflamatórias mais comuns que afetam a pele. Existem diversos fármacos para o tratamento da acne, porém apesar dos benefícios desses tratamentos na sua forma livre, existem efeitos adversos comuns a eles, principalmente quando aplicados topicamente. Dentre estes fármacos, destaca-se o adapaleno com ação comedolítica e efeitos sobre o processo anormal de queratinização e diferenciação epidérmica, fenômenos presentes na acne vulgar. O presente trabalho teve como objetivo, preparar nanocápsulas poliméricas (NC) de adapaleno através do método de deposição interfacial do polímero pré-formado utilizando diferentes núcleos oleosos (Miglyol® e óleo de melaleuca). As suspensões foram caracterizadas através da determinação do pH, diâmetro de partícula, índice de polidispersão, potencial zeta, taxa de associação e doseamento do fármaco. A estabilidade foi determinada em diferentes temperaturas e frente à luz UVA; estudos de liberação in vitro e análises de modelagem matemática dos perfis cinéticos de liberação foram realizados comparando-se suspensões contendo NC de adapaleno e nanodispersões, sem a presença do polímero. As formulações foram armazenadas em temperatura ambiente (25 °C), geladeira (-4 °C) e estufa (40 °C) durante 3 meses e analisadas nos tempos 0, 7, 15, 30, 60 e 90 dias após preparação. Tanto as suspensões contendo NC com Miglyol® (NC-AD-Miglyol®) como as NC com óleo de melaleuca (NC-AD-Melaleuca) apresentaram pH ácido, diâmetro de partícula inferior a 300 nm e potencial zeta negativo. A taxa de associação do adapaleno na NC-AD-Melaleuca foi de 95,4% enquanto na NC-AD-Miglyol® foi 84,1%. Através do doseamento do ativo, concluiu-se que as NC-AD-Melaleuca exercem efeito estabilizante maior que as demais formulações. O prazo de validade estimado para a NC-AD-Melaleuca foi superior quando comparado à nanodispersão (ND) e a NC-AD-Miglyol®. A modelagem matemática demonstrou que a ND e a NC-AD-Miglyol® seguiram um perfil cinético segundo o modelo monoexponencial com tempo de meia-vida de 3,53 e 8,43 horas, respectivamente. Já a suspensão NC-AD-Melaleuca seguiu modelo biexponencial com tempo de meia-vida para a fase rápida de 4,07 horas e 230,6 horas para a fase sustentada. Pode-se concluir que o adapaleno na formulação NC-AD-Miglyol® encontra-se em grande parte mais externamente nas NC enquanto na NC-AD-Melaleuca, o fármaco encontra-se dissolvido no núcleo oleoso das NC, sugerindo dessa forma, uma liberação sustentada. Avaliou-se a fotoestabilidade do adapaleno nanoencapsulado com Miglyol® e óleo de melaleuca frente à irradiação por UVA e concluiu-se que a nanoencapsulação com óleo de melaleuca aumenta a estabilidade do ativo, protegendo-o da degradação. Em análises por espalhamento múltiplo de luz, as suspensões apresentaram tendência à sedimentação, porém a NC-AD-Miglyol® demonstrou mais probabilidade à desestabilização. A validação da metodologia apresentou resultados satisfatórios para todos os parâmetros analisados. Através dos resultados obtidos, pode-se concluir que a suspensão contendo NC-AD-Melaleuca apresentou melhores características físico-químicas e de estabilidade, representando melhor viabilidade tecnológica para a área farmacêutica.