The thrust of this thesis is to study oral solid dosage formulation using hot melt coating method and to use pharmacokinetic modeling and simulation (PK M&S) as a tool that can help to predict pharmacokinetics of a drug in human and the probability of passing various bioequivalence criteria of the formulation based on the PK of the drug. Hot-melt coating using a new method, direct blending, was performed to create immediate and sustained release formulations (IR and SR). This new method was introduced to offer another choice to produce IR and SR drug delivery formulations using single and double coating layer of waxes onto sugar beads and/or drug loaded pellets. Twelve waxes were applied to coat sugar cores. The harder the wax the slower the drug was released from single coated beads. The wax coating can be deposited up to 28% of the weight of the core bead with 58% drug loading efficiency in the coating The cores were coated with single or double wax layers containing acetaminophen. Carnauba wax coated beads dissolved in approximately 6 hrs releasing 80% of loaded drug. However, when covered with another layer, the drug loaded beads released drug for over 20 hrs. When drug loaded pellets were used as cores, 33-58% drug loading was achieved. Double coated pellets exhibited a near zero order drug release for up to 16 hrs. Hot melt coating by direct blending using waxes is a simple process compared to conventional hot melt coating using coating pan or fluid bed coating machines. It offers an alternative way of making immediate, sustained drug release (IR, SR) and modified release (IR+SR) oral dosage forms of drugs which are stable at high temperature (100°C). The pellet-containing-drug coated formulations provide options when higher drug loading is warranted. It is required by the US Food and Drug Administration (FDA) that a new modified –release (MR) product or identical generic product be regarded as bioequivalent (BE) to the originators reference drug product. However, there are concerns that current regulatory criteria are not sufficient when evaluating bioequivalence (BE) for many MR products, and additional metrics for BE assessment of the products should be applied to ensure therapeutic equivalence. This study used pharmacokinetic modeling and simulation (M&S) to investigate 1) the probability of BE occurring between the MR test and reference products 2) the rates of false positive and true negative of the BE test; and 3) the estimation of the sample size in pivotal BE studies; all of which when partial area under the curves (pAUCs) were applied as additional BE criteria. Reference data of two MR forms of methylphenydate HCl (MPH) were simulated and obtained from literature (formulation Q and Metadate CD, respectively). Monte Carlo simulations were performed to simulate the test drug concentration profiles and BE assessment was carried out utilizing the mean (method 1) and individual concentration time curves (method 2). For formulation Q, adding pAUC₀₋[subscript Tmax] to current BE criteria reduced the possibility of passing BE from approximately 98% to 85%, with a true negative rate of 5%. The earlier the time points used to determine for pAUC before Tmax, the lower the chance of passing BE for the test product. The possibility of passing BE varied and depended on the coefficient of variations (CV) of T[subscript lag], K[subscript a] and K[subscript e] and that considerable variability in the parameters affected the earlier segments of the drug concentration profile curves more. Similar drug concentration time profiles between the test and reference products is recommended to ensure bioequivalence occurs with a reasonable subject sample size. A similar scenario was seen when Metadate CD was used as the reference product. PK M&S can help provide appropriate additional metrics to assure the BE test is a better tool ensuring therapeutic equivalence for MR products with little negative impact to generic manufacturers. Predictions can also be made about the required sample size and the chances of passing BE with any addition to the conventional three criteria for the test product. PK M&S was also used to predict drug concentrations of levofloxacin in tissue. Levofloxacin has been widely used in clinical practice as an effective broad-spectrum antimicrobial, however tendonitis and tendon rupture have been reported with increasing use of this agent. Here, these incidents will be assessed by investigating pharmacokinetic behavior of the compound to see if they are related to drug's tissue disposition. The PK model for levofloxacin was established. Mean concentration time profiles of single or multiple dosing of 500 mg levofloxacin following oral and IV infusion administration were simulated. Monte Carlo simulation was used to simulate the drug concentration time profiles in plasma (compartment 1) and tissue (compartment 2) after seven dosing regimens while varying the drug's elimination and distribution rates to see the effect of changing those rates have on the drug accumulation in tissue. Monte Carlo Simulation shows that low elimination rates affect the drug concentration in plasma and tissue significantly with the level in plasma rising up to 35 μg/mL at day 7. A normal elimination rate together with escalation of distribution rates from plasma to tissue could increase the tissue concentration after 7 doses to 9.5 µg/mL, a value that is more than twice that of normal. PK M&S can be used as an effective tool to evaluate drug concentration in different compartments (plasma and tissues, for example). The unexpectedly high concentration values in some cases may explain, at least in part, the reason of tendinopathy occurs in the clinical setting. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from June 7, 2012 - June 7, 2014

Amyotrophic lateral sclerosis (ALS) is a devastating disease. Currently, there is no cure for this disease, and effective treatment strategies are greatly needed. Calpain activation plays a major role in the motor neuron degeneration that causes ALS. Therefore, therapeutic strategies can inhibit calpain activity in the central nervous system (CNS) have great clinical potential. The calpain inhibitors AK295 and MDL-28170 have been demonstrated to be neuroprotective in animal models of neurological injury, and should have great potential to treat ALS; however delivery problems have hindered their clinical success. Therefore, development of a new strategy that can locally deliver the calpain inhibitors to the central nervous system could significantly improve the treatment of ALS. The objectives of my thesis research were (1) to develop high molecular weight polyketals that provide sustained release properties for hydrophobic molecules, (2) to formulate calpain inhibitor-encapsulated polyketal microparticles which have a release half life of one month in vitro, (3) and to evaluate the performance of polyketal microparticles for delivering calpain inhibitors to the spinal cord in vivo. In completing these specific aims, we have developed biodegradable polymeric microparticles for the delivery of calpain inhibitors, AK295 and MDL-28170 to treat ALS. The results of calpain assays showed that both AK-PKMs and MDL-PKMs maintained most of their inhibitory activities even after the robust emulsion process. The in vitro release profile of MDL-28170 in MDL-PKMs showed that 50 % of the drug was released in the first 30 days. Experiments using dye-encapsulated microparticles showed that polyketal microparticles (1-2 ìm) are not easily cleared in the neutral physiological environment and can have potential to continuously release drug from the injection sites in the spinal cord. The efficacy of calpain inhibitor-encapsulated PKMs were studied by evaluation the behavior and survival of SOD1G93A rats, a genetic rat model for ALS. We observed the trend toward improvements in grip strength and rotarod performance in the first two months from the AK-PKMs treated group, however, further improvements are needed to enhance their in vivo efficacy.

Colloidal assemblies of surfactants and polymers in aqueous solutions have been used by human mankind for hundreds of years and they are of great importance in many of our technological processes, such as fabrication of soap and papermaking. Less than two decades ago the idea of using colloidal assemblies as templates of inorganic materials was borne. A new population of materials, referred to as surfactant templated materials, took form. These materials showed extraordinary properties such as monodisperse pore size distribution, large surface areas and pore volumes.   The main focus of this thesis has been on synthesis and functionalisation of spherical mesostructured silica particulate materials. In the first part of the work, mesostructured materials with expanded pores have been produced using a well established aerosol-based method as well as the newly developed emulsion and solvent evaporation (ESE) method. Increase in pore size was realized through using Pluronic block copolymer F127 together with a swelling agent poly(propylene glycol) as template. The influence of the swelling agent on pore size expansion was shown to have a roughly linear relationship. Furthermore, the impact of synthesis parameters on internal and exterior morphology has been investigated. Accessibility of the internal pore space, as well as the external surface roughness were shown to be highly dependent on synthesis temperature. Additionally, a very interesting well ordered 3D closed packed (P63/mmc) material was produced using the ionic surfactant C16TAB as template in the ESE method.   In the second part of the thesis work, mesoporous spheres with large pore size, having either hydrophilic or hydrophobic surface properties, were used as carriers of an enzyme, lipase. The enzymatic activity of lipase was increased onto the hydrophobic surface, compared to lipase immobilized into the hydrophilic support as well as for lipase free in solution. This effect was probably due to a combination of enhanced hydrophobic interactions preventing denaturation of the enzyme and interfacial activation of the enzyme.  This study generated an inorganic carrier material that is a promising candidate for biocatalysis applications. Additionally, mesoporous spheres were used as carriers of a model drug, Ibuprofen, to study the effect of polyelectrolyte multilayers on release properties. However, these layers were shown impermeable independent on pH and the substance was only released from uncoated particles. / <p>QC 20100811</p>

La formulation de médicaments regroupe des technologies innovantes où l'usage de matières premières naturelles émerge du fait de contraintes environnementales grandissantes. Les huiles végétales par exemple sont plébiscitées grâce à leurs propriétés remarquables en terme de solubilisation de principes actifs, de biocompatibilité et de biodégradabilité. Afin d'élargir leurs applications, notamment pour la libération prolongée de principes actifs, la solidification de ces huiles par réticulation a été envisagée à l'aide d'une chimie douce, c'est-à-dire respectueuse des principes de la chimie verte. La silice a été choisie pour réaliser la réticulation par réaction sol-gel d'huiles végétales et ainsi obtenir des matériaux hybrides inorganique/organique d'origine naturelle. L'étude a consisté à fonctionnaliser des huiles végétales à l'aide de précurseurs silylés en utilisant une chimie sans solvant ni catalyseur, pour obtenir des huiles réticulables par voie sol-gel. Deux voies chimiques de fonctionnalisation ont été employées. La première, difficilement contrôlable, été basée sur une réaction époxy-amine où des huiles de lin ou de soja époxydées ont été utilisées. La seconde reposait sur la valorisation d'huile de ricin porteuse d'un groupement hydroxyle via une réaction hydroxy-isocyanate. Les excellents résultats obtenus ont permis de poursuivre l'étude par la formulation de l'huile de ricin silylée grâce à un nouveau procédé d'émulsion huile/eau thermo-stabilisée. Simple et robuste, ce procédé a rendu possible de façon concomitante la mise en forme et la solidification de microparticules hybrides. Les microparticules présentent des distributions de taille homogènes (20 à 200 µm), sont sphériques et capables de piéger des molécules lipophiles. Ainsi une molécule modèle, a été encapsulé avec des rendements très satisfaisants et sa libération a été totale après 8h en milieu physiologiques simulé. En modifiant la composition des microparticules (ratio inorganique / organique), il a été possible de prolonger les cinétiques de libération et de réduire significativement « l’effet burst ». La biocompatibilité de ces microparticules a été démontrée in vitro. Enfin dans l’optique de correctement caractériser la réaction sol-gel, différentes techniques analytiques ont été explorées pour l’étude in situ de la réticulation et l’identification d’un catalyseur biocompatible. Ces travaux ont permis de détailler les mécanismes des réactions d’hydrolyse et de polycondensation et ont ouvert la voie à un meilleur contrôle des cinétiques de réticulation des microparticules. De plus, il est apparu que la maîtrise de cette réaction semble être indispensable afin d'obtenir des objets "stabilisés " aux propriétés identiques et aux cinétiques de libération reproductibles. En conclusion, il a été démontré que la chimie sol-gel appliquée aux huiles naturelles offre des possibilités d’innovation en formulation galénique tout en respectant les contraintes environnementales et de santé et a permis le développement de matériaux originaux aux propriétés modulables. / Drug formulation is gathering innovative technologies where the use of natural products for the preparation of drug delivery systems is getting more and more considerations because of environmental concerns. For instance, vegetable oils get increasingly used because of their outstanding properties in terms of drug solubilization, biocompatibility and biodegradability. For expanding their application, to drug sustained-release for instance, oils have to be hardened under mild conditions with respect to green chemistry principals. The silica condensation was therefore chosen as cross-linking reaction by the mean the sol-gel reaction which when applied to vegetable oils led to biosourced hybrid organic/inorganic materials. To do so, oils were functionalized with alkoxysilanes precursors without solvent nor catalyst in order to obtain cross-linkable systems. Two chemical paths were studied. The first one, based on an epoxy-amine reaction between epoxydized linseed or soybean oils and the alkoxysilane precursor ended up with an uncontrolled reaction and a triglyceride disruption. The second, used castor oil as an hydroxylated raw material and was based on the hydroxy-isocyanate reaction. Valuable results were obtained and this silylated oil was formulated thanks to a new oil/water thermo-stabilized emulsion process. Simple and robust, this process allowed to simultaneously shape and harden hybrid microparticles. Ranging between 20 and 200 µm in diameter, hybrid microparticles were spherical, homogeneously distributed and were capable of entrapping and releasing lipophilic molecules. As a model, ibuprofen was efficiently encapsulated and was fully released over 8 hours in a simulated buffer. Furthermore, by changing the composition of hybrid microparticles (inorganic/organic ratio), it was also possible to extend release kinetics and significantly reduce the burst effect. Then, biocompatibility of those hybrid microparticles was demonstrated in vitro and an innovative study of the cross-linking reaction was performed. This study aimed to properly understand hydrolysis and polycondensation mechanisms and took the form of an in situ the sol-gel reaction monitoring. It allowed to identify an alternative biocompatible catalysts and gave an insight on how those reactions can be controlled to reach “stabilized" hybrids with constant properties and exhibiting robust and reproducible drug sustained-releases. Finally, it has been demonstrated that the sol-gel chemistry applied to vegetable oils for the synthesis of original and tunable hybrid materials with concerns to environmental and health issues, opened the gate towards innovations in drug formulation.

Ce travail a été mené afin de développer des systèmes polymériques particulaires chargés en facteur de croissance (TGF-β1) en vue d’une application à l’ingénierie tissulaire du cartilage. Tout d’abord, des nanoparticules d’acide poly(lactique-co-glycolique) (PLGA) ont été générées par un procédé basé sur la séparation de phase. De plus, des microparticules de PLGA ont été formées à l’aide d’un procédé d’émulsification/extraction du solvant en milieu CO2 pressurisé. L’un des avantages de ces procédés de formulation est l’utilisation de solvants injectables, non toxiques et non volatils. Les systèmes polymériques préparés ont été caractérisés et des particules sphériques à libération contrôlée ont été obtenues avec un rendement d’encapsulation satisfaisant tout en préservant l’activité biologique du facteur de croissance. Les particules chargées en TGF-β1 ont ensuite été incorporées dans un hydrogel injectable à base d’un dérivé cellulosique silanisé (Si-HPMC) contenant des cellules souches. Le biomatériau obtenu a été caractérisé en termes de morphologie, de propriétés rhéologiques et pour sa capacité à libérer le facteur de croissance. La libération contrôlée et localisée du TGF-β1 pourrait induire la survie, la prolifération ainsi que la différenciation chondrocytaire des cellules souches associées ce qui contribuerait à la régénération du cartilage. En conclusion, le biomatériau hybride élaboré au cours de ce travail possède un potentiel prometteur pour l’ingénierie tissulaire du cartilage. / The aim of this work is to develop polymeric particulate systems loaded with transforming growth factor (TGF-β1) for cartilage tissue engineering application. First, nanoparticles of PLGA (poly(lactic-co-glycolic) acid) were generated using a phase separation method while PLGA microparticles were prepared by an emulsification/extraction process in CO2 medium. Interestingly, non-toxic, non-volatile injectable solvents were used in the formulation processes. The prepared polymeric systems were characterized; spherical particles with sustained release were obtained and satisfactory encapsulation efficiency was achieved with preservation of the growth factor bioactivity. TGF-β1-loaded particles were then incorporated within injectable silanized cellulose-based hydrogel (Si-HPMC) containing stem cells. The obtained biomaterial was characterized in terms of morphology, rheological properties and release study. The local and sustained release of TGF-β1 could induce survival, proliferation and differentiation of stem cells into chondrocytes which may promote cartilage regeneration. To conclude, the elaborated hybrid biomaterial has a promising potential for cartilage tissue engineering.

Parmi toutes les voies d’administration, la voie orale a toujours suscité un grand intérêt. Les formes prises par voie orale présentent une grande facilité d’administration pour le patient, tandis que pour les chercheurs, la physiologie du système gastro-intestinal peut être facilement modélisable. Malheureusement, son importante variabilité, liée principalement au temps de vidange gastrique, peut conduire à une mauvaise reproductibilité des effets thérapeutiques et à une diminution de la biodisponibilité. Ce problème est surtout rencontré dans le cas des principes actifs présentant une fenêtre d’absorption étroite au niveau de l’intestin supérieur [Deshpande et col. 1996]. Une solution a été de développer des formes galéniques à libération prolongée caractérisées par un temps de résidence gastrique accru. Ainsi, le principe actif est libéré progressivement en amont de sa fenêtre d’absorption. Dans cette optique, plusieurs systèmes ont été développés :des formes bioadhésives, expansibles, gonflantes ou à hautes densités [Singh et Kim, 2000]. Mais parmi toutes ces formes, ce sont les systèmes flottants qui semblent offrir la protection la plus efficace contre une vidange gastrique précoce [Moës, 1989]. Seth et Tossounian ont ainsi développé une gélule flottante à libération prolongée, basée sur le gonflement d’un dérivé cellulosique. Etant une forme monolithique, sa vidange gastrique était soumise au phénomène de tout ou rien. De plus, cette forme présentait un inconvénient majeur puisqu’elle était sujette à des fractionnements intra-gastriques, diminuant de ce fait la reproductibilité inter- et intra-individuelle [Seth et Tossounian, 1984]. <p>\ / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

Modified-release oral drug delivery dosage forms are widely used in the pharmaceutical field to overcome all the potential issues imposed by the physiological variabilities of the gastrointestinal tract as well as to maintain drug concentrations within the therapeutic window. In the market, they are available only as solid dosage forms such as capsules or tablets. The development of a liquid oral dosage form with modified-release properties has been keenly awaited. This form could increase the compliance of patients with a swallowing impairment (i.e. paediatric, older or critically ill patients) and, consequently, the efficacy of the therapeutic treatment. In this study, a new technology has been developed that consists of multi-layered particles suspended extemporaneously in a syrup. Omeprazole and budesonide have been employed as model drugs. The coating procedure was optimized to obtain a yield of minimum 90% w/w and a median diameter below 500 µm. Once the final suspension is prepared extemporaneously, it presents sufficient stability to guarantee the administration of multiple doses filled into a syrup bottle and kept for a limited storage time at room temperature (e.g. up to 10 doses to be administered within 10 days). / Doctorat en Sciences biomédicales et pharmaceutiques (Pharmacie) / info:eu-repo/semantics/nonPublished

Les amidons non modifiées et modifiés représentent un groupe d’excipients biodégradables et abondants particulièrement intéressant. Ils ont été largement utilisés en tant qu’excipients à des fins diverses dans des formulations de comprimés, tels que liants et/ou agents de délitement. Le carboxyméthylamidon sodique à haute teneur en amylose atomisé (SD HASCA) a été récemment proposé comme un excipient hydrophile à libération prolongée innovant dans les formes posologiques orales solides. Le carboxyméthylamidon sodique à haute teneur en amylose amorphe (HASCA) a d'abord été produit par l'éthérification de l'amidon de maïs à haute teneur en amylose avec le chloroacétate. HASCA a été par la suite séché par atomisation pour obtenir le SD HASCA. Ce nouvel excipient a montré des propriétés présentant certains avantages dans la production de formes galéniques à libération prolongée. Les comprimés matriciels produits à partir de SD HASCA sont peu coûteux, simples à formuler et faciles à produire par compression directe. Le principal objectif de cette recherche était de poursuivre le développement et l'optimisation des comprimés matriciels utilisant SD HASCA comme excipient pour des formulations orales à libération prolongée. A cet effet, des tests de dissolution simulant les conditions physiologiques du tractus gastro-intestinal les plus pertinentes, en tenant compte de la nature du polymère à l’étude, ont été utilisés pour évaluer les caractéristiques à libération prolongée et démontrer la performance des formulations SD HASCA. Une étude clinique exploratoire a également été réalisée pour évaluer les propriétés de libération prolongée de cette nouvelle forme galénique dans le tractus gastro-intestinal. Le premier article présenté dans cette thèse a évalué les propriétés de libération prolongée et l'intégrité physique de formulations contenant un mélange comprimé de principe actif, de chlorure de sodium et de SD HASCA, dans des milieux de dissolution biologiquement pertinentes. L'influence de différentes valeurs de pH acide et de temps de séjour dans le milieu acide a été étudiée. Le profil de libération prolongée du principe actif à partir d'une formulation de SD HASCA optimisée n'a pas été significativement affecté ni par la valeur de pH acide ni par le temps de séjour dans le milieu acide. Ces résultats suggèrent une influence limitée de la variabilité intra et interindividuelle du pH gastrique sur la cinétique de libération à partir de matrices de SD HASCA. De plus, la formulation optimisée a gardé son intégrité pendant toute la durée des tests de dissolution. L’étude in vivo exploratoire a démontré une absorption prolongée du principe actif après administration orale des comprimés matriciels de SD HASCA et a montré que les comprimés ne se sont pas désintégrés en passant par l'estomac et qu’ils ont résisté à l’hydrolyse par les α-amylases dans l'intestin. Le deuxième article présente le développement de comprimés SD HASCA pour une administration orale une fois par jour et deux fois par jour contenant du chlorhydrate de tramadol (100 mg et 200 mg). Ces formulations à libération prolongée ont présenté des valeurs de dureté élevées sans nécessiter l'ajout de liants, ce qui facilite la production et la manipulation des comprimés au niveau industriel. La force de compression appliquée pour produire les comprimés n'a pas d'incidence significative sur les profils de libération du principe actif. Le temps de libération totale à partir de comprimés SD HASCA a augmenté de manière significative avec le poids du comprimé et peut, de ce fait, être utilisé pour moduler le temps de libération à partir de ces formulations. Lorsque les comprimés ont été exposés à un gradient de pH et à un milieu à 40% d'éthanol, un gel très rigide s’est formé progressivement sur leur surface amenant à la libération prolongée du principe actif. Ces propriétés ont indiqué que SD HASCA est un excipient robuste pour la production de formes galéniques orales à libération prolongée, pouvant réduire la probabilité d’une libération massive de principe actif et, en conséquence, des effets secondaires, même dans le cas de co-administration avec une forte dose d'alcool. Le troisième article a étudié l'effet de α-amylase sur la libération de principe actif à partir de comprimés SD HASCA contenant de l’acétaminophène et du chlorhydrate de tramadol qui ont été développés dans les premières étapes de cette recherche (Acetaminophen SR et Tramadol SR). La modélisation mathématique a montré qu'une augmentation de la concentration d’α-amylase a entraîné une augmentation de l'érosion de polymère par rapport à la diffusion de principe actif comme étant le principal mécanisme contrôlant la libération de principe actif, pour les deux formulations et les deux temps de résidence en milieu acide. Cependant, même si le mécanisme de libération peut être affecté, des concentrations d’α-amylase allant de 0 UI/L à 20000 UI/L n'ont pas eu d'incidence significative sur les profils de libération prolongée à partir de comprimés SD HASCA, indépendamment de la durée de séjour en milieu acide, le principe actif utilisé, la teneur en polymère et la différente composition de chaque formulation. Le travail présenté dans cette thèse démontre clairement l'utilité de SD HASCA en tant qu'un excipient à libération prolongée efficace. / Unmodified and modified starches represent a particularly interesting group of biodegradable and abundant excipients. They have been widely used as excipients for various purposes in tablet formulations, such as binders and/or disintegrants. Spray-dried high-amylose sodium carboxymethyl starch (SD HASCA) was recently proposed as an innovating hydrophilic excipient for sustained-release (SR) in solid oral dosage forms. Amorphous high-amylose sodium carboxymethyl starch (HASCA) was first produced by the etherification of high-amylose corn starch with chloroacetate. HASCA was then spray dried to obtain SD HASCA. This new excipient has shown advantageous and effective properties in the production of SR delivery systems. SR matrix tablets prepared from SD HASCA are inexpensive, simple to formulate and easy to produce by direct compression. The main objective of the present research was to continue the development and optimization of matrix tablets using SD HASCA as the retarding excipient in view of their ultimate application as sustained drug-release delivery systems for oral administration. For this purpose, dissolution tests simulating some of the most relevant physiological conditions of the gastrointestinal tract, taking into account the nature of the polymer under investigation, were employed to evaluate the drug-release characteristics and demonstrate the performance of SD HASCA SR formulations. An exploratory clinical study was also carried out to evaluate the SR properties of this new drug delivery system in the gastrointestinal tract. The first article presented in this thesis evaluated the drug-release characteristics and the physical integrity of formulations containing a compressed blend of drug, sodium chloride and SD HASCA in biorelevant media. The influence of different acidic pH values and residence times was investigated. The SR profile from an optimized SD HASCA formulation was not significantly affected by both the acidic pH value and the residence time in the acidic medium. These results suggest a limited influence of intra- and inter-subject variability of gastric pH on the release kinetics from SD HASCA matrices. In addition, the optimized formulation maintained its integrity throughout the duration of the dissolution tests. The exploratory in vivo study demonstrated extended drug absorption after oral administration of SD HASCA matrix tablets and that the matrix tablets did not disintegrate while passing through the stomach and resisted hydrolysis by α-amylase in the intestine. The second article reports the development of once-daily and twice-daily SD HASCA tablets containing tramadol hydrochloride (100 mg and 200 mg). These SR formulations presented high crushing strengths without requiring the addition of binders, which facilitates tablet processing and handling. The compression force (CF) applied to produce the tablets did not significantly affect the drug-release profiles. The total release time from SD HASCA tablets increased significantly in function of the tablet weight and can be used to modulate the total release time from theses formulations. When exposed to a pH gradient and to a 40% ethanol medium, a very rigid gel formed progressively on the surface of the tablets providing controlled drug-release properties. These properties indicated that SD HASCA is a robust excipient for oral, sustained drug-release, likely to minimize the possibility of dose dumping and consequent adverse effects, even when co-administered with high doses of alcohol. The third article investigated the effect of α-amylase on drug-release from previously developed SD HASCA tablets containing acetaminophen and tramadol hydrochloride (Acetaminophen SR and Tramadol SR). Mathematical modeling showed that an increase in α-amylase concentration resulted in an increase of polymer erosion over drug diffusion as the main mechanism controlling drug-release, for both formulations and both residence times in acidic medium. However, even if the mechanism of release was affected, α-amylase concentrations ranging from 0 IU/L to 20000 IU/L did not significantly affect the drug-release profiles from SD HASCA SR tablets, regardless of the residence time in acidic medium, the drug used, the polymer content and the different composition of each formulation. The work presented in this thesis clearly demonstrates the value of SD HASCA as an efficient SR excipient.

Abstract ACCURATE METHODOLOGY FOR MONITORING BIOMEMBRANE EVENTS By Christine A. Winschel, Ph.D. A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in Chemistry at Virginia Commonwealth University. Virginia Commonwealth University, 2012 Major Director: Dr. Vladimir A. Sidorov ASSOCIATE PROFESSOR, DEPARTMENT OF CHEMISTRY This study describes the synthesis and characterization of a new receptor (cyclen 1) capable of strong selective binding of pyrene-based anionic dyes under near-physiological conditions. This receptor comprises four naphthylthiourea groups tethered to a cyclen core via an ester linkage. The most important finding was the ability of cyclen 1 to bind efficiently to a pH-sensitive pyranine dye, a dye that is commonly used in various biomembrane assays. The high affinity of cyclen 1 to pyranine, its impermeability to the lipid bilayer membrane, fast kinetics of binding, and ability to quench pyranine’s fluorescence were used as a basis for a new membrane leakage assay. This membrane leakage assay is fully compatible with the commonly applied pH-stat transport assay, and therefore it allows for differentiation of ion transport and nonselective leakage mechanisms within a single set of experiments. In the second part of this study a new methodology for the detection of lipid flip was developed. This methodology relies on the quenching of the fluorescence of a newly synthesized cascade-blue-labeled lipid through complex formation with cyclen 1. This receptor-dye complexation also has high affinity for binding at micromolar concentrations and can be reversed by either competitive displacement of the lipid probe or by enzymatic degradation of the receptor leading to the label release and fluorescence dequenching. This new methodology is suitable for the study of lipid flip in both model spherical bilayer membranes and in-vitro experiments, and is less invasive to the model and cell membranes than the commonly utilized 7-nitro-1,2,3-benzoxadiazol-4-yl (NBD)-dithionite methodology. Lastly, new pH-sensitive lipids were synthesized and utilized in the formulation of liposomes suitable for controlled drug release. These liposomes contain various amounts of internal NaCl and undergo internal acidification upon the exogenous addition of an HCl co-transporter in a physiologically relevant NaCl solution. Therefore, acidification ultimately leads to the hydrolysis of the pH-sensitive lipids and subsequent contents release. These liposomes were found to be insensitive to physiological concentrations of human serum albumin and to be non-toxic to cells at concentrations exceeding pharmacological relevance. These results render this new drug release model potentially suitable for in vivo applications.

O objetivo do presente trabalho foi desenvolver e avaliar péletes para compor sistema multiparticulado contendo ácido ascórbico, bem como validar metodologia analítica por cromatografia líquida de alta eficiência (CLAE) para aplicação em ensaio de dissolução destas formas farmacêuticas. A técnica de extrusão-esferonização foi utilizada por ser de fácil aplicação a nível laboratorial e industrial obtendo-se péletes matriciais, compostos de Methocel® K4M, Methocel® K100M e Eudragit® L 100, e péletes de liberação convencionais, para revestimento em leito fluidizado com Kollicoat® SR 30 D como agente regulador da liberação do fármaco. O sistema multiparticulado foi preparado na forma de comprimido pela compressão dos péletes com menor nível de revestimento, avaliando-se o nível de força aplicada e a presença da Microcel® 101 como protetor da camada de revestimento. Os péletes obtidos foram caracterizados quanto à esfericidade por análise imagem, friabilidade, dureza e perfil de dissolução comparativo com apresentações comerciais. Os péletes matriciais foram obtidos com grau de dificuldade variável em função do polímero utilizado, porém apresentaram esfericidade e resistência mecânica adequadas. O perfil de dissolução destas formulações demonstrou que não houve controle na liberação do fármaco, mesmo naquelas onde havia maior concentração de polímero. Os péletes revestidos com três níveis de polímero (5,07; 8,26 e 10,35% em relação à massa do pélete) apresentaram boas características granulométricas e o perfil de dissolução daqueles revestidos com 5,07% de polímero demonstrou semelhança com o da apresentação comercial. O perfil de dissolução comparativo entre os péletes isolados e os comprimidos obtidos sem a presença de excipiente mostrou que ocorre dano na camada de revestimento nos maiores níveis de força de compressão aplicada. Para os comprimidos obtidos a partir da mistura de péletes e Microcel® 101 este fato não foi observado, indicando que a presença do excipiente é fundamental para a manutenção da integridade da camada de revestimento além de promover a desintegração parcial dos comprimidos. / The present work aimed to develop and evaluate pellets to compound a multiparticulate system containing ascorbic acid, as well as, validate analytic methodology through high performance liquid chromatography and evaluate the essay of dissolution from these dosage forms. The extrusion-spheronization technique was used for its laboratorial and industrial application to obtain matrix pellets compounds of Methocel® K4M, Methocel® K100M, Eudragit® L 100, and conventional release pellets, for fluid bed coating with Kollicoat® SR 30 O as a regular occurrence release agent for the drug. The multiple system was prepared in tablets through the compression of the pellets with a lower coating levei, evaluating its applied compression force and the presence of Microcel® 101 as a protector of the coating layer. The obtained pellets were characterized according to its roundness through image analysis, friability, hardness and dissolution profile compared with those marketed products. The matrix pellets were obtained on varied difficulty degree due to the polymer utilized, even through they presented adequate spheroid and mechanical properties. The dissolution profile of these formulations didn\'t show any control in the release of the drug even in those, which had a high concentration of the polymer. The pellets coated with three polymers leveis (5,07%, 8,26% and 10,35% related to the pellets mass) presented good sphericity, and the dissolution profile of those pellets coated with 5,07% polymer demonstrated similarity with those ones marketed products. The comparative dissolution profile among isolated pellets and the tablets obtained without excipients presence, showed that damage right occur on the higher compression force levei is applied. This fact is not observed on the tablets obtained from the pellets blend and Microcel®101, which indicates that the presence of the excipients is fundamental for the maintenance and integrity of the coating layer, moreover, it causes the partial disintegration of the tablets.