Made available in DSpace on 2014-06-12T15:49:33Z (GMT). No. of bitstreams: 1 license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O objetivo do presente estudo é avaliar a toxicidade subcrônica oral do ácido úsnico encapsulado em microesferas de copolímero de ácido láctico e glicólico em comparação com sua forma em suspensão. As microesferas contendo ácido úsnico foram preparadas utilizando a técnica de emulsão (A/O/A) seguida de evaporação do solvente e caracterizadas através do tamanho de partículas, carga superficial e taxa de encapsulação. No estudo de toxicidade, ratos machos Wistar receberam doses orais de 25 mg/Kg/dia de ácido úsnico encapsulado em microesferas (UA-MS) ou ácido úsnico (UA) em suspensão por 28 dias. O efeito tóxico causado pelos tratamentos foi avaliado através da eficiência de conversão alimentar, análise bioquímica e histopatológica e microscopia confocal de varredura a laser. As microesferas contendo UA apresentaram-se com tamanho de partículas de 4,92 ± 0,44 μm, carga de superfície de -25,7 ± 6,5 mV e eficiência de encapsulação de 99,0 ± 0,82 %. Uma diferença significativa foi observada na eficiência de conversão alimentar dos animais tratados com UA, mas nenhuma diferença foi observada no grupo tratado com UA-MS. Não houve diferença no peso dos órgãos em todos os grupos de animais. Um aumento significante de AST e ALT foi observado nos animais tratados com UA (44 ± 4.3 and 106.1 ± 10.4 U/L, respectivamente) quando comparado com o grupo não tratado (32.2 ± 3.9 and 82.5 ± 13.8 U/L, respectivemente). Contudo, alterações enzimáticas significantes não foram encontradas após o tratamento dos animais com UA-MS, desse modo confirma uma redução da hepatoxicidade do UA devido a sua microencapsulação. Mudanças não foram observadas nos níveis séricos de uréia e creatinina após o tratamento com UA ou UA-MS confirmando que o ácido úsnico não apresenta nefrotoxicidade. As análises histopatológicas do fígado demonstraram extensas áreas de degeneração vacuolar com áreas de necrose nos animais tratados com UA. Porém, os animais tratados com UA-MS não desenvolveram alterações hepáticas, sugerindo que a microencapsulação do ácido úsnico foi capaz de reduzir sua hepatotoxicidade. O UA foi detectado no fígado e rins dos animais tratados com ácido úsnico livre, através da fluorescência intrínseca do ácido úsnico, indicando a sua captura hepática e eliminação renal. Uma menor intensidade de fluorescência foi visualizada no fígado após tratamento com ácido úsnico microencapsulado, devido à liberação controlada pelas microesferas. Nenhuma fluorescência foi detectada no rim após tratamento dos animais com ácido úsnico encapsulado. Estes resultados sugerem que a microencapsulação do ácido úsnico pode reduzir sua hepatotoxicidade, desse modo permitindo o seu uso para aplicação terapêutica

The purpose of this study is to demonstrate the effectiveness of spheres-in-tube structured scaffolds to sequentially deliver two biomolecules during two phases of tissue regeneration following spinal cord injury (SCI). Scaffolds were synthesized of a poly (lactic-co-glycolic acid) (PLGA) base combined with Poly (L-lactic acid) / Poly (ε-caprolactone) (PLLA/PCL) microspheres. The scaffolds are constructed by leveraging the different solubilities of PLGA, PLLA and PCL in super critical carbon dioxide and ethyl acetate during fabrication processes. Microspheres can reduce the pore size and porosity of PLGA scaffolds; this enhances their mechanical strength and enables them to provide long-term treatment without collapse. The release of the epidermal growth factor (EGF) and basic fibroblast growth factor (FGF-b) are being used to study the release profiles of the designed scaffolds. The analysis shows that FGF-b is released from high porosity PLGA base as the first delivery vehicle and completes the release in the first week. PLLA or PCL microspheres, having the property of sustainably delivering encapsulated EGF in 36 days, are used as the second drug delivery vehicle. FGF-b released within the first week can mimic biomolecules used to protect the surviving neurons and promote the development of sprout axons. The sustained release of EGF from microspheres is used for long-term therapy to differentiate multipotent cells into determined types at the injury site. The results demonstrate that these enhanced parameters along with the ability of sequential co-delivery of growth factors, make these designed scaffolds a promising candidate in SCI studies.

In this project we aim to produce a thermally triggered PLGA particulate gel, which is injectable and biocompatible. This will act as a scaffold for soft tissue repair. Three coating polymers were tested: Pluronics (PEG-PPG-PEG), poly(PPGMA-co-PEGMA) and poly(PNIPAm-DMA+). These were first tested as a dilute solution for clouding behaviour and then added to PLGA nanoparticles dispersions and tested rheologically for gel behaviour. These three polymers were chosen for their amphiphilic nature which may allow for surface attachment and decreasing miscibility with temperature. The PLGA copolymer in this work contained 75% lactic acid and 25% glycolic acid, and was made into a nanoparticle dispersion by interfacial deposition. The Pluronic L62 showed a promising cloud point temperature (Tclpt) of 37 °C, but did not show gel behaviour with the PLGA dispersions. It conferred thermally triggered aggregation, which may be useful as a drug delivery system. The poly(PPGMA-PEGMA) was synthesised using a free radical polymerisation feed method. These copolymers showed promising Tclpt values (20-37 °C) but only showed increased viscosity when heated at high concentration and when mixed with a PLGA dispersion. The structure-property relationships for these copolymers were analysed. Poly(NIPAM-DMA+) showed gelation at low concentrations without the particles, when the particle dispersion was added the gel maintained its strength up to 300% strain. This is unlike most particulate gels which tend to be brittle. Using cell culture the biocompatibility of these gels was tested. After 72 hours the cells appeared healthy and to be proliferating.

Ces travaux visaient à développer de nouveaux implants biodégradables se formant in situ pour le traitement des parodontites, les infections les plus fréquentes au monde. Ces implants permettront de délivrer localement le principe actif et de contrôler sa libération. L’un des pré-requis pour ces nouveaux systèmes est de présenter une bonne bioadhésion et des propriétés mécaniques permettant d’éviter une expulsion prématurée hors de la poche parodontale.Tout d’abord, de nouveaux implants se formant in situ avec un potentiel prometteur pour surmonter l'un des inconvénients majeurs liés au traitement local de la parodontite: l’adhérence limitée aux tissus environnants ont été développés. L'addition de diverses concentrations de différents types de plastifiants (l’acetyltributyl citrate, ATBC et le dibutyl sebacate, DBS) et de polymères adhésifs (l'hydroxypropyl méthylcellulose, HPMC) ont permis d’obtenir une augmentation significative de l’adhésion des implants à base de l’acide poly(lactique-co-glycolique) (PLGA). Ces systèmes sont formés in situ à partir des formulations liquides de N-méthyl-2-pyrrolidone (NMP). Dans le même temps, une bonne aptitude à la déformation plastique des implants a été obtenue et les cinétiques de libération du principe actif souhaitées ont pu être affinées à l'aide de plusieurs outils de formulation. L'activité antimicrobienne de ce nouveau type d'implants se formant in situ, chargés à l’hyclate de doxycycline, a été démontrée en utilisant la méthode de diffusion en gélose sur plusieurs souches de Streptococcus isolées à partir de la microflore buccale des patients souffrant de parodontite.Ensuite, une meilleure compréhension des mécanismes de formation in situ des implants a été suivi en utilisant de différentes techniques tels que: la résonance paramagnétique électronique (EPR), la résonance magnétique nucléaire (1H NMR), le suivi de l’évolution de la masse et la cinétique de libération du principe actif dans différentes conditions, la microscopie optique, la chromatographie d'exclusion stérique (SEC). Des implants se formant in situ à base de PLGA, d’ATBC, de chlorhydrate de minocycline, de NMP et d’HPMC, ont été préparés et caractérisés en détail in vitro. Ces résultats ont révélé une vision approfondie sur les phénomènes physico-chimiques impliqués dans la formation de l'implant et sur le contrôle de la libération du principe actif. Par exemple, les effets de l'ajout d’HPMC dans la formulation, qui améliore l'adhérence de l'implant et réduit le gonflement, ont pu être expliqués. De manière importante, les implants se formant in situ ont efficacement empêché la croissance bactérienne dans les poches parodontales des patients. Enfin, l’impact de la composition des implants sur la performance des systèmes a été étudié. Afin d’élucider ces relations, des techniques de caractérisation de pointe, telles que l'analyse EPR ont été utilisées. Il est intéressant de noter que l’ajout d’HPMC et de PLGA de plus faible poids moléculaire a légèrement diminué la libération du principe actif, alors que dans le cas de PLGA de poids moléculaire plus élevé, la vitesse de libération a substantiellement augmenté. Ces tendances peuvent être expliquées en se basant sur la cinétique du transport de masse au cours de la formation de l'implant et des structures internes des systèmes. En outre, l'activité antimicrobienne des implants contre les micro-organismes présents dans les poches parodontales de patients atteints de parodontite a été évaluée. Ces systèmes gênent plus efficacement la croissance des bactéries pathogènes que celle des micro-organismes physiologiques. Ainsi, une recolonisation de la flore saine dans les poches des patients peut être envisagée in vivo. / This work aimed to develop new biodegradable in situ forming implants for the treatment of periodontitis, the most common infections in the world. These implants would locally deliver the active ingredient and control its release. One of the prerequisites for these new systems is to provide a good bioadhesion and mechanical properties to prevent premature expulsion from the periodontal pocket. Firstly, new in situ forming implants with promising potential to overcome one of the major drawbacks for the local treatment of periodontitis: limited adhesion to the surrounding tissue were developed. The addition of various concentrations of different types of plasticizers (acetyltributyl citrate, ATBC and dibutyl sebacate, DBS) and adhesive polymers (hydroxypropyl methylcellulose, HPMC) resulted in a significant increase in the adhesion of poly(lactic-co-glycolic acid) (PLGA)-based implants. The systems are formed in situ from N-methyl pyrrolidone (NMP)-based liquid formulations. Importantly, at the same time, good plastic deformability of the implants could be provided and desired drug release patterns could be fine-tuned using several formulation tools. The antimicrobial activity of this new type of in situ forming implants, loaded with doxycycline hyclate, was demonstrated using the agar well diffusion method and multiple Streptococcus strains isolated from the oral microflora of patients suffering from periodontitis.Secondly, a better understanding of the mechanisms of the in situ implant formation was followed using different techniques such as electron paramagnetic resonance (EPR), nuclear magnetic resonance (1H NMR), mass change and drug release measurements under different conditions, optical microscopy, size exclusion chromatography (SEC). The in situ forming implants containing PLGA, ATBC, minocycline hydrochloride, HPMC and NMP were prepared and characterized in detail in vitro. Based on these results, deeper insight into the physico-chemical phenomena involved in implant formation and the control of drug release could be gained. For instance, the effects of adding HPMC to the formulations, resulting in improved implant adherence and reduced swelling, could be explained. Importantly, the in situ formed implants effectively hindered the growth of bacteria present in the patients’ periodontal pockets.Finally, the impact of the composition of the implants on system performance was investigated using advanced characterization techniques, such as EPR analysis. Interestingly, HPMC addition to shorter chain PLGA slightly decreased drug release, whereas in the case of longer chain PLGA the release rate substantially increased. These tendencies could be explained based on the mass transport kinetics during implant formation and the systems’ inner structures. Furthermore, the implants’ antimicrobial activity against microorganisms present in the periodontal pockets of patients suffering from periodontitis was evaluated. Interestingly, these systems more effectively hinder the growth of pathogenic bacteria than of physiological microorganisms. Thus, a re-colonization of the patients’ pockets with healthy flora can be expected to be favored in vivo.

Blood vessels mimics (BVMs) are tissue-engineered blood vessels used to test vascular devices in an environment that mimics some simple anatomical factors of native blood vessels. It is important to accurately and consistently assess tissue-engineered blood vessels, although there is currently a lack of standardization in Cal Poly’s Tissue Engineering Lab and in the entirety of the field. The goal of this thesis was to develop and optimize imaging and image quantification techniques for tissue-engineered blood vessels. The first aim of this thesis optimized and compared imaging and assessment techniques for electrospun scaffolds. Images from different SEMs were compared to determine the benefits and drawbacks of each microscope. Several materials were also imaged using these microscopes to characterize polymers at the microscopic scale and to compare the quality of images from different SEMs. The second aim of this thesis validated and implemented a MATLAB-based automatic fiber diameter measurement tool. Fiber measurements were obtained from a manual ImageJ method, a semi-automatic DiameterJ method, and a new automatic MATLAB method and compared to evaluate accuracy and user variability of the MATLAB tool. The results of this aim validated the accuracy of the MATLAB tool and showed that it resulted in lower user variability as compared to other fiber diameter measurement methods. The third aim of this thesis developed imaging techniques for novel silicone BVMs at each stage of development. Evaluation techniques to quantify cell adhesion and coverage on silicone BVMs using SEM, widefield fluorescent imaging, and immunochemistry were developed. After refining those methods, they were applied and adapted to silicone BVMs with deployed devices. BBI, H&E, and PECAM-1 staining were all found to be effective assessment methods for silicone BVMs. Overall, the work described in this thesis increased the consistency, standardization, and accuracy of scaffold and BVM assessment in Cal Poly’s Tissue Engineering Lab.

Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of: Pharmaceutical Technology Consultants: PharmDr. Ondřej Holas, Ph.D. Student: Simona Žemličková Title of thesis: Hybrid polymeric-lipid nanoparticles as drug carriers The work is focused on hybrid polymer-lipid nanoparticles, their advantages obtained from polymer and lipid part, purpose of surface modification, basic properties of nanoparticles, methods of preparation, modification of preparation conditions and use of nanoparticles in medicine. The aim of the experimental part was to prepare nanoparticles composed of polyester and lipid by emulsion evaporation method and nanoprecipitation. Two types of linear polymer poly (lactic-co-glycolic acid) and phosphatidylcholine were used in various ratios. The surfactant used for stabilization was poloxamer Pluronic® F127 and the organic solvents were ethyl acetate and acetone. Curcumin served as a model active substance. The effect of lipid and surfactant on the size and zeta potential of nanoparticles was evaluated. Modification of preparation conditions, which included many process parameters, also influenced the monitored parameters. Encapsulation effectivity and drug loading were also tested. Dissolution tests were performed. It was found that size of nanoparticles...

Efforts to enhance the utility of photodynamic therapy as a non-invasive method for treating certain cancers have often involved the design of dye sensitizers with increased singlet oxygen efficiency. More recently, however, sensitizers with greater selectivity for tumor cells than surrounding tissue have been targeted. The present study provides an approach to the modification of the known photosensitizer zinc phthalocyanine (ZnPc), to enhance its solubility and delivery to cancer cells. Targeting a photosensitizer to the site of action improves the efficacy of the sensitizer in photodynamic therapy. In this work we used PLGA-b-PEG to encapsulate a new zinc phthalocyanine derivative, 2(3), 9(10), 16(17), 23(24)-tetrakis-(4'-methyl-benzyloxy) phthalocyanine zinc(II) (ZnPcBCH3), to enhance uptake into A549 cells, a human lung cancer cell line. ZnPcBCH3 exhibited the same photochemical properties as the parent compound ZnPc but gave increased solubility in organic solvents, which allowed for efficient encapsulation. In addition, the encapsulated dye showed a near 500-fold increase in phototoxicity for A549 cancer cells compared to free dye.

OBJECTIVE: Niacin, activating G-protein coupled receptor (GPR) 109A, stimulates release of vasodilatory prostaglandins (PGs) such as PGE2 which can elicit niacin-associated flushing side effects. Poly-lactic-coglycolic acid (PLGA) and poly-lactic acid (PLA) are used in nanoparticle (NP) drug delivery to reduce adverse effects and modulate drug release. Our study evaluated the in vitro effects of niacin-loaded PLGA or PLA-NPs on PGE2 expression in whole human blood as a model for niacin-induced flushing. MATERIALS AND METHODS: NPs were formulated using a solvent evaporation process and characterized by size, polydispersity, zeta potential, drug entrapment, morphology, and drug release. NP in vitro effects on PGE2 release were measured via ELISA analysis. RESULTS: PLGA-NPs demonstrated the lowest NP size (66.7 ± 0.21 nm) with the highest zeta potential and percent drug entrapment (42.00 ± 1.62 mV and 69.09 ± 0.29%, respectively) when compared to PLA-NPs (130.4 ± 0.66 nm, 27.96 ± 0.18 mV, 69.63 ± 0.03 %, respectively). In vitro release studies showed that PLGA-NPs underwent significant reductions in cumulative drug release when compared to PLA-NPs (p < 0.05). Furthermore, when compared to plain niacin, PLGA-NPs significantly reduced in vitro PGE2 release (p < 0.05). CONCLUSIONS: These results support the use of PLGA-NPs as a novel method of delivery for reducing niacin-associated flushing.

Since the approval of recombinant human insulin in 1982, there has been a growing interest in the use of biotherapeutics, and more particularly of monoclonal antibodies (mAb)-based products due to their multiple advantages compared to small chemical entities. Nonetheless, mAbs also show some drawbacks, one of them being their sensitivity to diverse instability pathways due to their complex structure. Therefore, attention needs to be paid during formulation and storage of such entities. While administration of mAbs using non-invasive routes has been extensively investigated, it still faces several challenges, especially regarding systemic therapy. Thus, parenteral route currently remains the main route of administration for antibodies (Abs). However, frequent injections are required in order to maintain Ab plasma levels into the therapeutic range, which may induce peak-to-trough fluctuations in blood levels due to multiple dosing as well as poor patient compliance. Consequently, methods to increase the half-life of Abs have gained interest over the last decades, and more particularly the use of sustained-delivery systems based on poly(lactide-co-glycolide) acid (PLGA) derivatives. In this work, the spray-drying of a water-in-oil emulsion (w/o) was selected as the formulation technique to produce Ab-loaded PLGA microparticles. Based on the requirement of sustained-release delivery systems, different objectives were set regarding the characteristics of the microparticles, i.e. a drug loading (DL) of at least 20%, a continuous in vitro and in vivo Ab release over a minimum of one month with a limited burst release and the possibility to maintain Ab stability during manufacturing, storage and release. / Doctorat en Sciences biomédicales et pharmaceutiques (Pharmacie) / info:eu-repo/semantics/nonPublished

No description available.