Effect of drug loading and plasticizer on drug release from poly lactic acid film

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Effect of drug loading and plasticizer on drug release from poly lactic acid film

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

EXAMINATION OF VALPROIC ACID-INDUCED PERTURBATIONS TO DNA REPAIR, NF-ΚB SIGNALING AND CBP/P300 TRANSCRIPTIONAL CO-ACTIVATORS

Exposure to the antiepileptic drug valproic acid (VPA) is associated with an increased risk of congenital malformations including heart, skeletal and most frequently neural tube defects. Although the mechanisms contributing to its teratogenesis are not well understood, VPA was previously shown to increase homologous recombination (HR)-mediated DNA repair and decrease protein expression of the transcription factor NF-κB/p65. The studies in this thesis utilized in vivo and in vitro models to evaluate the expression of HR mediators, investigate the implications of decreased p65 including DNA binding and transcriptional activation, and the expression and histone acetyltransferase activity of Cbp/p300 with an aim to provide mechanistic insight into VPA-mediated alterations. The first study demonstrated that following maternal administration of VPA, mouse embryonic mRNA expression of HR mediators Rad51, Brca1 and Brca2 exhibited temporal and tissue-specific alterations. Protein expression of Rad51 was similarly altered and preceded increased cleavage of caspase-3 and PARP; indicative of apoptosis. The second study confirms previous findings of decreased total cellular p65 protein using P19 cells, but is the first to demonstrate that nuclear p65 protein is unchanged. NF-κB DNA binding was decreased following VPA exposure and maybe mediated by decreased p50 protein, which dimerizes with p65 prior to DNA binding. Transcriptional activity of NF-κB was also increased with VPA exposure which was not due to increased p65 phosphorylation at Ser276. Furthermore, the transcriptional activation capacity was unaffected by VPA exposure as combined exposure to VPA and TNFα additively increased NF-κB activity. The third study demonstrated that VPA exposure in P19 cells decreased Cbp/p300 total cellular and nuclear protein attributed primarily to ubiquitin proteasome-mediated degradation. Histone acetyltransferase (HAT) activity of p300 was decreased proportionately to nuclear protein following VPA exposure. Inhibition of Cbp/p300 HAT activity decreased p65 total cellular protein, increased caspase-3 cleavage and ROS similar to VPA exposures. Furthermore, pre-treatment with the antioxidant enzyme catalase attenuated the increase in caspase-3 cleavage, but not p65 protein. Overall, this thesis demonstrates that VPA exposure impacts the expression and activity of the transcription factor NF-κB and transcriptional co-activators/HATs Cbp/p300, which has implications for downstream VPA targets including Rad51, Brca1 and Brca2.

Daunorubicin and gambogic acid co-loaded cysteamine-CdTe quantum dots minimizing the multidrug resistance of lymphoma in vitro and in vivo

To minimize the side effects and the multidrug resistance (MDR) arising from daunorubicin (DNR) treatment of malignant lymphoma, a chemotherapy formulation of cysteamine-modified cadmium tellurium (Cys-CdTe) quantum dots coloaded with DNR and gambogic acid (GA) nanoparticles (DNR-GA-Cys-CdTe NPs) was developed. The physical property, drug-loading efficiency and drug release behavior of these DNR-GA-Cys-CdTe NPs were evaluated, and their cytotoxicity was explored by 3-[4,5-dimethylthiazol-2-y1]-2,5-diphenyltetrazolium bromide assay. These DNR-GA-Cys-CdTe NPs possessed a pH-responsive behavior, and displayed a dose-dependent antiproliferative activity on multidrug-resistant lymphoma Raji/DNR cells. The accumulation of DNR inside the cells, revealed by flow cytometry assay, and the down-regulated expression of P-glycoprotein inside the Raji/DNR cells measured by Western blotting assay indicated that these DNR-GA-Cys-CdTe NPs could minimize the MDR of Raji/DNR cells. This multidrug delivery system would be a promising strategy for minimizing MDR against the lymphoma.

Développement d’une stratégie de modification du bois afin de limiter les variations dimensionnelles du produit lambris dans un contexte éco-responsable

Ce travail de thèse présente deux grands axes. Le premier axe, touche les traitements du bois dans le but principal de réduire les variations dimensionnelles et d’améliorer la résistance à l’attaque des champignons lignivores. Le second axe quant à lui, touche l’aspect environnemental du traitement acide citrique-glycérol. Ce dernier a pour but principal de démontrer que le prolongement de la durée de vie en service du produit lambris traité, compense les impacts environnementaux causés par ce traitement. Dans le premier axe, deux traitements ont été réalisés sur deux essences de pin (Pinus strobus L. et Pinus contorta D.). Un traitement à l’anhydride maléique et un autre traitement avec une solution d’acide citrique – glycérol brute (AC-G). Dans le premier cas, les effets de deux paramètres (la durée de séchage et la température d’estérification) sur les résultats des essais de stabilité dimensionnelle, de résistance à la dégradation fongique et de vieillissement accéléré ont été évalués. Trois niveaux de durée de séchage après imprégnation (12 h, 18 h et 24 h) et trois niveaux de température d’estérification (140 °C, 160 °C et 180 °C) ont été considérés. Dans le second cas, après identification du meilleur catalyseur (HCl) et du meilleur ratio acide citrique – glycérol (3/1) pendant les essais préliminaires, les performances de ce traitement sur la stabilité dimensionnelle, la résistance à la pourriture fongique, la dureté de surface et l’adhérence des couches de revêtement de peinture sur la surface du substrat bois ont été analysées. Les résultats obtenus ont été appuyés par une suite d’analyses qualitatives et quantitatives pour mieux comprendre et expliquer. Les analyses qualitatives sont : (i) la spectroscopie infrarouge à transformée de Fourier (IRTF) et (ii) la microscopie électronique à balayage (MEB) tandis que la quantitative, l’analyse par perte de masse a été faite par pesée. Dans le second axe, une analyse des impacts environnementaux du traitement AC-G a été effectuée par le biais du logiciel SimaPro v8. La base de données Ecoinvent v3 et la méthode d’analyse d’impact Impact 2002+ ont été utilisées dans cette partie du travail de thèse. Sur la base des résultats du second traitement (AC-G) et des travaux disponibles dans la littérature, nous avons estimé, une durée de vie en service des lambris traités. Les différents scénarios de la durée de vie du lambris traité mis sur pied par rapport à celle offerte aujourd’hui par l’industrie, nous permettent de modéliser les impacts environnementaux du traitement. A cette fin, l’analyse de cycle de vie (ACV) a été utilisée comme outil de conception. En conclusion, les paramètres, durée de séchage et température d’estérification influencent les résultats obtenus dans le cas du traitement du bois à l’anhydride maléique. La combinaison 24 h de séchage et 180 °C, température d’estérification, représente les paramètres qui offrent les meilleurs résultats de stabilité dimensionnelle, de résistance à la dégradation fongique et de vieillissement accéléré. Le traitement AC-G améliore la stabilité dimensionnelle, la résistance à la dégradation fongique et la dureté de surface des échantillons. Cependant, le traitement réduit l’adhérence des couches de peinture. Les impacts environnementaux produits par le traitement AC-G sont majoritairement liés à la consommation de la ressource énergie (électricité). Le traitement prolonge la durée de vie en service du lambris traité et il a été mis en évidence que le scénario de durée de vie qui permettrait que le lambris traité puisse se présenter comme un produit à faible impact environnemental par rapport au lambris non traité est celui d’une durée de vie de 55 ans.

Development and characterization of Poly(L-lactic acid) (PLLA) platforms for bone tissue engineering

The development of scaffolds based on biomaterials is a promising strategy for Tissue Engineering and cellular regeneration. This work focuses on Bone Tissue Engineering, the aim is to develop electrically tailored biomaterials with different crystalline and electric features, and study their impacts onto cell biological behavior, so as to predict the materials output in the enhancement of bone tissue regeneration. It is accepted that bone exhibits piezoelectricity, a property that has been proved to be involved in bone growth/repair mechanism regulation. In addition electrical stimulations have been proved to influence bone growth and repair. Piezoelectric materials are therefore widely investigated for a potential use in bone tissue engineering. The main goal is the development of novel strategies to produce and employ piezoelectric biomaterials, with detailed knowledge of mechanisms involved in cell-material interaction. In the current work, poly (L-lactic) acid (PLLA), a synthetic semi-crystalline polymer, exhibiting biodegradibility, biocompatibility and piezoelectricity is studied and proposed as a promoter of enhanced tissue regeneration. PLLA has already been approved for implantation in human body by the Food and Drug Administration (FDA), and at the moment it is being used in several clinical strategies. The present study consists of first preparing films with different degrees of crystallinity and characterizing these PLLA films, in terms of surface and structural properties, and subsequently assessing the behavior of cells in terms of viability, proliferation, morphology and mineralization for each PLLA configuration. PLLA films were prepared using the solvent cast technique and submitted to different thermal treatments in order to obtain different degrees of crystallinity. Those platforms were then electrically poled, positively and negatively, by corona discharge in order to tailor their electrical properties. The cellular assays were conducted by using two different osteoblast cell lines grown directly onto the PLLA films:Human osteoblast Hob, a primary cell culture and Human osteosarcoma MG-63 cell line. This thesis gives also a comprehensive introduction to the area of Bone Tissue Engineering and provides a review of the work done in this field in the past until today, in that same field, including the one related with bone’s piezoelectricity. Then the experimental part deals with the effects of the crystallinity degrees and of the polarization in terms of surface properties and cellular bio assays. Three different degrees of crystallinity, and three different polarization conditions were prepared; which results in 9 different configurations under investigation.

Encapsulation of Local Anesthetic Bupivacaine in Biodegradable Poly(DL-lactide-co-glycolide) Nanospheres: Factorial Design, Characterization and Cytotoxicity Studies

Local anesthetic agents cause temporary blockade of nerve impulses productiong insensitivity to painful stimuli in the area supplied by that nerve. Bupivacaine (BVC) is an amide-type local anesthetic widely used in surgery and obstetrics for sustained peripheral and central nerve blockade. in this study, we prepared and characterized nanosphere formulations containing BVC. To achieve these goals, BVC loaded poly(DL-lactide-co-glycolide) (PLGA) nanospheres (NS) were prepared by nanopreciptation and characterized with regard to size distribution, drug loading and cytotoxicity assays. The 2(3-1) factorial experimental design was used to study the influence of three different independent variables on nanoparticle drug loading. BVC was assayed by HPLC, the particle size and zeta potential were determined by dynamic light scattering. BVC was determined using a combined ultrafiltration-centrifugation technique. The results of optimized formulations showed a narrow size distribution with a polydispersivity of 0.05%, an average diameter of 236.7 +/- 2.6 nm and the zeta potential -2.93 +/- 1,10 mV. In toxicity studies with fibroblast 3T3 cells, BVC loaded-PLGA-NS increased cell viability, in comparison with the effect produced by free BVC. In this way, BVC-loaded PLGA-NS decreased BVC toxicity. The development of BVC formulations in carriers such as nanospheres could offer the possibility of controlling drug delivery in biological systems, prolonging the anesthetic effect and reducing toxicity.

Effects of 15d-PGJ(2)-loaded poly(D,L-lactide-co-glycolide) nanocapsules on inflammation

BACKGROUND and PURPOSEThe PPAR-gamma agonist 15d-PGJ(2) is a potent anti-inflammatory agent but only at high doses. To improve the efficiency of 15d-PGJ(2), we used poly(D,L-lactide-co-glycolide) nanocapsules to encapsulate it, and function as a drug carrier system. The effects of these loaded nanocapsules (15d-PGJ(2)-NC) on inflammation induced by different stimuli were compared with those of free 15d-PGJ(2).EXPERIMENTAL APPROACHMice were pretreated (s.c.) with either 15d-PGJ(2)-NC or unloaded 15d-PGJ(2) (3, 10 or 30 mu g center dot kg-1), before induction of an inflammatory response by i.p. injection of either endotoxin (LPS), carrageenan (Cg) or mBSA (immune response).KEY RESULTSThe 15d-PGJ(2)-NC complex did not display changes in physico-chemical parameters or drug association efficiency over time, and was stable for up to 60 days of storage. Neutrophil migration induced by i.p. administration of LPS, Cg or mBSA was inhibited by 15d-PGJ(2)-NC, but not by unloaded 15d-PGJ(2). In the Cg model, 15d-PGJ(2)-NC markedly inhibited serum levels of the pro-inflammatory cytokines TNF-alpha, IL-1 beta and IL-12p70. Importantly, 15d-PGJ(2)-NC released high amounts of 15d-PGJ(2), reaching a peak between 2 and 8 h after administration. 15d-PGJ(2) was detected in mouse serum after 24 h, indicating sustained release from the carrier. When the same concentration of unloaded 15d-PGJ(2) was administered, only small amounts of 15d-PGJ(2) were found in the serum after a few hours.CONCLUSIONS and IMPLICATIONSThe present findings clearly indicate the potential of the novel anti-inflammatory 15d-PGJ(2) carrier formulation, administered systemically. The formulation enables the use of a much smaller drug dose, and is significantly more effective compared with unloaded 15d-PGJ(2).

Development of semicrystalline morphology of poly(L-lactic acid) during processing of a vascular scaffold

New and promising treatments for coronary heart disease are enabled by vascular scaffolds made of poly(L-lactic acid) (PLLA), as demonstrated by Abbott Vascular’s bioresorbable vascular scaffold. PLLA is a semicrystalline polymer whose degree of crystallinity and crystalline microstructure depend on the thermal and deformation history during processing. In turn, the semicrystalline morphology determines scaffold strength and biodegradation time. However, spatially-resolved information about the resulting material structure (crystallinity and crystal orientation) is needed to interpret in vivo observations.

The first manufacturing step of the scaffold is tube expansion in a process similar to injection blow molding. Spatial uniformity of the tube microstructure is essential for the consistent production and performance of the final scaffold. For implantation into the artery, solid-state deformation below the glass transition temperature is imposed on a laser-cut subassembly to crimp it into a small diameter. Regions of localized strain during crimping are implicated in deployment behavior.

To examine the semicrystalline microstructure development of the scaffold, we employed complementary techniques of scanning electron and polarized light microscopy, wide-angle X-ray scattering, and X-ray microdiffraction. These techniques enabled us to assess the microstructure at the micro and nano length scale. The results show that the expanded tube is very uniform in the azimuthal and axial directions and that radial variations are more pronounced. The crimping step dramatically changes the microstructure of the subassembly by imposing extreme elongation and compression. Spatial information on the degree and direction of chain orientation from X-ray microdiffraction data gives insight into the mechanism by which the PLLA dissipates the stresses during crimping, without fracture. Finally, analysis of the microstructure after deployment shows that it is inherited from the crimping step and contributes to the scaffold’s successful implantation in vivo.

Octyl co-grafted PrSO3H/SBA-15:tunable hydrophobic solid acid catalysts for acetic acid esterification

Propylsulfonic acid (PrSO3H) derivatised solid acid catalysts have been prepared by post modification of mesoporous SBA-15 silica with mercaptopropyltrimethoxysilane (MPTMS), with the impact of co-derivatisation with octyltrimethoxysilane (OTMS) groups to impart hydrophobicity to the catalyst investigated. Turn over frequencies (TOF) for acetic acid esterification with methanol increase with PrSO3H surface coverage across both families suggesting a cooperative effect of adjacent acid sites at high acid site densities. Esterification activity is further promoted upon co-functionalisation with hydrophobic octyl chains, with inverse gas chromatography (iGC) measurements indicating increased activity correlates with decreased surface polarity or increased hydrophobicity.

Using Different Co-Adjuvant Activating Agents to Improve Activated Carbon Adsorption Capacities

Activated carbon (AC) has proved to be an effective adsorbent for the removal of an assortment of organic and inorganic pollutants from aqueous or gaseous media. However, the pursuit for more effective and cheaper AC is still very active and a diversity of textural and chemical treatments are described as a way to expand their applications. It is well known that the surface area and surface chemistry of AC strongly affect their adsorption capacity [1-3]. In particular, an increase in the nitrogen content has been related to an increase of the basic character and also to the development of the porous structure. In most published work this was achieved through an AC post treatment, including either a reaction with nitrogen containing reagents, such as ammonia, nitric acid, or a diversity of amines. However, the AC prepared directly from a nitrogen rich precursor through a physical or chemical activation is referred to as presenting the best characteristics, namely high nitrogen content, high basic character, low nitrogen leaching and also a good thermal stability [4]. To improve the AC adsorption capacities for acidic pesticide removal from the aqueous phase, we intend to improve the porous structure and introduce nitrogenated groups directly into the AC matrix, using different co-adjuvant activating agents as a nitrogen source, by chemical activation, with potassium hydroxide, of cork or poly(ethyleneterephthalate) (PET) precursors.

Thermodynamic Study Of The Micellization Of Zwitterionic Surfactants And Their Interaction With Polymers In Water By Isothermal Titration Calorimetry.

The micellization of a homologous series of zwitterionic surfactants, a group of sulfobetaines, was studied using isothermal titration calorimetry (ITC) in the temperature range from 15 to 65 °C. The increase in both temperature and the alkyl chain length leads to more negative values of ΔGmic(0) , favoring the micellization. The entropic term (ΔSmic(0)) is predominant at lower temperatures, and above ca. 55-65 °C, the enthalpic term (ΔHmic(0)) becomes prevalent, figuring a jointly driven process as the temperature increases. The interaction of these sulfobetaines with different polymers was also studied by ITC. Among the polymers studied, only two induced the formation of micellar aggregates at lower surfactant concentration: poly(acrylic acid), PAA, probably due to the formation of hydrogen bonds between the carboxylic group of the polymer and the sulfonate group of the surfactant, and poly(sodium 4-styrenesulfonate), PSS, probably due to the incorporation of the hydrophobic styrene group into the micelles. The prevalence of the hydrophobic and not the electrostatic contributions to the interaction between sulfobetaine and PSS was confirmed by an increased interaction enthalpy in the presence of electrolytes (NaCl) and by the observation of a significant temperature dependence, the latter consistent with the proposed removal of hydrophobic groups from water.

Nitric Oxide-releasing Poly(vinyl Alcohol) Film For Increasing Dermal Vasodilation.

Pathological conditions associated with the impairment of nitric oxide (NO) production in the vasculature, such as Raynaud's syndrome and diabetic angiopathy, have stimulated the development of new biomaterials capable of delivering NO topically. With this purpose, we modified poly(vinyl-alcohol) (PVA) by chemically crosslinking it via esterification with mercaptosuccinic acid. This reaction allowed the casting of sulfhydrylated PVA (PVA-SH) films. Differential scanning calorimetry and X-ray diffractometry showed that the crosslinking reaction completely suppressed the crystallization of PVA, leading to a non-porous film with a homogeneous distribution of -SH groups. The remaining free hydroxyl groups in the PVA-SH network conferred partial hydrophylicity to the material, which was responsible for a swelling degree of ca. 110%. The PVA-SH films were subjected to an S-nitrosation reaction of the -SH groups, yielding a PVA containing S-nitrosothiol groups (PVA-SNO). Amperometric and chemiluminescence measurements showed that the PVA-SNO films were capable of releasing NO spontaneously after immersion in physiological medium. Laser Doppler-flowmetry, used to assess the blood flow in the dermal microcirculation, showed that the topical application of hydrated PVA-SNO films on the health skin led to a dose- and time-dependent increase of more than 5-fold in the dermal baseline blood flow in less than 10min, with a prolonged action of more than 4h during continuous application. These results show that PVA-SNO films might emerge as a new material with potential for the topical treatment of microvascular skin disorders.

Co-eletrodeposição oscilatória de cobre e estanho

It is investigated in the present contribution the oscillatory co-electrodeposition of CuSn on a polycrystalline gold surface in the presence of Triton X-100 surfactant and citric acid as additive, in acidic media. The experiments were conducted under potentiostatic control and the system dynamics characterized in terms of the morphology and stability of the current oscillations. Besides modulations in the frequency and amplitude of the current oscillations, several patterned states were observed, including relaxation-like and mixed mode oscillations. The oscillations were found to be very robust and some time series presented regular motions up to about two hours.

Photo-fenton degradation of poly(Ethyleneglycol)

Polyethyleneglycol (PEG) was photooxidized in a photo-Fenton system and results compared with the dark reaction. The products were analysed using GPC and HPLC. In the absence of light, PEG samples needed 490 min to reduce their w by 50%, whereas under UV irradiation, only 10 min were necessary. The exponential decay of w with a concomitant increase in polydispersity and number of average chain scission, characterized a random chain scission mechanism. The degradation products of PEG in both systems showed the presence of lower molecular weight products, including smaller ethyleneglycols and formic acid. The mechanism involves consecutive processes, were the larger ethyleneglycols give rise, successively, to smaller ones. This suggests that the mechanism involves successive scissions of the polymer chain. Irradiated samples decomposed faster than those kept in the dark This study proves that the foto-Fenton method associated with UV-light is a good reactant for PEG photodegradation.