High-amylose carboxymethyl starch matrices for oral sustained drug-release : in vitro and in vivo evaluation

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.

Microtubule disrupting N-phenyl-N’-(2-chloroethyl) ureas display anticancer activity on cell adhesion, P-glycoprotein and BCL-2-mediated drug resistance.

Objective: Our research program has focused on the development of promising, soft alkylating N-phenyl-N’-(2-chloroethyl)urea (CEU) compounds which acylate the glutamic acid-198 of β-tubulin, near the binding site of colchicum alkaloids. CEUs inhibit the motility of cancerous cells in vitro and, interestingly, exhibit antiangiogenic and anticancer activity in vivo. Mitotic arrest induced by microtubule-interfering agents such as CEUs remains the major mechanism of their anticancer activity, leading to apoptosis. However, we recently demonstrated that microtubule disruption by CEUs and other common antimicrotubule agents greatly alters the integrity and organization of microtubule-associated structures, the focal adhesion contact, thereby initiating anoikis, an apoptosis-like cell death mechanism caused by the loss of cell contact with the extracellular matrix. Methods: To ascertain the activated signaling pathway profile of CEUs, flow cytometry, Western blot, immunohistochemistry and transfection experiments were performed. Wound-healing and chick embryo assays were carried out to evaluate the antiangiogenic potency of CEUs. Results: CEU-induced apoptosis involved early cell cycle arrest in G2/M and increased level of CDK1/cycline B proteins. These signaling events were followed by the specific activation of the intrinsic apoptosis pathway, involving loss of mitochondrial membrane potential (Δψm) and ROS production, cytochrome c release from mitochondria, caspase activation, AIF nuclear translocation, PARP cleavage and nuclear fragmentation. CEUs maintained their efficacy on cells plated on pro-survival extracellular matrices or exhibiting overexpression of P-glycoprotein or the anti-apoptotic protein Bcl-2. Conclusion: Our results suggest that CEUs represent a promising new class of antimicrotubule, antiangiogenic and pro-anoikis agents.

How fast and how often: the pharmacokinetics of drug use are decisive in addiction

How much, how often and how fast a drug reaches the brain determine the behavioural and neuroplastic changes associated with the addiction process. Despite the critical nature of these variables, the drug addiction field often ignores pharmacokinetic issues, which we argue can lead to false conclusions. First, we review the clinical data demonstrating the importance of the speed of drug onset and of intermittent patterns of drug intake in psychostimulant drug addiction. This is followed by a review of the preclinical literature demonstrating that pharmacokinetic variables play a decisive role in determining behavioural and neurobiological outcomes in animal models of addiction. This literature includes recent data highlighting the importance of intermittent, ‘spiking’ brain levels of drug in producing an increase in the motivation to take drug over time. Rapid drug onset and intermittent drug exposure both appear to push the addiction process forward most effectively. This has significant implications for refining animal models of addiction and for better understanding the neuroadaptations that are critical for the disorder.

Assessment of PEG on Polymeric Particles Surface, a Key Step in Drug Carrier Translation

Injectable drug nanocarriers have greatly benefited in their clinical development from the addition of a superficial hydrophilic corona to improve their cargo pharmacokinetics. The most studied and used polymer for this purpose is poly(ethylene glycol), PEG. However, in spite of its wide use for over two decades now, there is no general consensus on the optimum PEG chain coverage-density and size required to escape from the mononuclear phagocyte system and to extend the circulation time. Moreover, cellular uptake and active targeting may have conflicting requirements in terms of surface properties of the nanocarriers which complicates even more the optimization process. These persistent issues can be largely attributed to the lack of straightforward characterization techniques to assess the coverage-density, the conformation or the thickness of a PEG layer grafted or adsorbed on a particulate drug carrier and is certainly one of the main reasons why so few clinical applications involving PEG coated particle-based drug delivery systems are under clinical trial so far. The objective of this review is to provide the reader with a brief description of the most relevant techniques used to assess qualitatively or quantitatively PEG chain coverage-density, conformation and layer thickness on polymeric nanoparticles. Emphasis has been made on polymeric particle (solid core) either made of copolymers containing PEG chains or modified after particle formation. Advantages and limitations of each technique are presented as well as methods to calculate PEG coverage-density and to investigate PEG chains conformation on the NP surface.

Drug-loaded nanocarriers : passive targeting and crossing of biological barriers

Poor bioavailability and poor pharmacokinetic characteristics are some of the leading causes of drug development failure. Therefore, poorly-soluble drugs, fragile proteins or nucleic acid products may benefit from their encapsulation in nanosized vehicles, providing enhanced solubilisation, protection against degradation, and increased access to pathological compartments. A key element for the success of drug-loaded nanocarriers (NC) is their ability to either cross biological barriers themselves or allow loaded drugs to traverse them to achieve optimal pharmacological action at pathological sites. Depending on the mode of administration, NC may have to cross different physiological barriers in their journey towards their target. In this review, the crossing of biological barriers by passive targeting strategies will be presented for intravenous delivery (vascular endothelial lining, particularly for tumour vasculature and blood-brain barrier targeting), oral administration (gastrointestinal lining) and upper airway administration (pulmonary epithelium). For each specific barrier, background information will be provided on the structure and biology of the tissues involved as well as available pathways for nano-objects or loaded drugs (diffusion and convection through fenestration, transcytosis, tight junction crossing, etc.). The determinants of passive targeting − size, shape, surface chemistry, surface patterning of nanovectors − will be discussed in light of current results. Perspectives on each mode of administration will be presented. The focus will be on polymeric nanoparticles and dendrimers although advances in liposome technology will be also reported as they represent the largest body in the drug delivery literature.

Effect of polymer architecture on Curcumin 1 encapsulation and release from PEGylated polymer nanoparticles: toward a drug delivery nano-platform to the CNS

We developed a nanoparticles (NPs) library from poly(ethylene glycol)–poly lactic acid comb-like polymers with variable amount of PEG. Curcumin was encapsulated in the NPs with a view to develop a delivery platform to treat diseases involving oxidative stress affecting the CNS. We observed a sharp decrease in size between 15 and 20% w/w of PEG which corresponds to a transition from a large solid particle structure to a “micelle-like” or “polymer nano-aggregate” structure. Drug loading, loading efficacy and release kinetics were determined. The diffusion coefficients of curcumin in NPs were determined using a mathematical modeling. The higher diffusion was observed for solid particles compared to “polymer nano-aggregate” particles. NPs did not present any significant toxicity when tested in vitro on a neuronal cell line. Moreover, the ability of NPs carrying curcumin to prevent oxidative stress was evidenced and linked to polymer architecture and NPs organization. Our study showed the intimate relationship between the polymer architecture and the biophysical properties of the resulting NPs and sheds light on new approaches to design efficient NP-based drug carriers.

Research Ethics and Commercial Drug Development: When Integrity Threatens Profitability

Étude de cas / Case study

Cinematographic Licensing

In India, film censorship originated with Cinematograph Act 1918 empowering the Provincial Governments to establish censorial authorities. In 1949, an amendment provided for a Central Board of Film Censors. In 1952, a new legislation gave the Central Government enormous powers, making the Board to function as a department of the Central Government. The Government had control over the Board with the mechanism of issuing 'directions' to the censors and laying down censorship rules. The legislation did not provide any objective criteria for censoring films. The 1959 amendment, aimed at curing this defect, only incorporated the grounds contained in Article 19(2) of the Constitution. Even after expert studies and a significant decision by the Supreme Court, pointing out the inadequacy of the existing system, and governmental attempts to bring reforms by way of fresh directions, appointment of appellate authority and framing of new rules, the system still warrants radical change. The thesis explores them.

Survival of multi-drug resistant enteropathogenic Escherichia coli and Salmonella paratyphi in Vembanadu lake as a function of saltwater barrier along southwest coast of India

The objective of the study was to evaluate the survival response of multi-drug resistant enteropathogenic Escherichia coli and Salmonella paratyphi to the salinity fluctuations induced by a saltwater barrier constructed in Vembanadu lake, which separates the lake into a freshwater dominated southern and brackish water dominated northern part. Therefore, microcosms containing freshwater, brackish water and microcosms with different saline concentrations (5, 10, 15, 20, 25 ppt) inoculated with E. coli/S. paratyphi were monitored up to 34 days at 20 and 30 WC. E. coli and S. paratyphi exhibited significantly higher (p <0.05) survival at 20 WC compared to 30 WC in all microcosms. Despite fresh/brackish water, E. coli and S. paratyphi showed prolonged survival up to 34 days at both temperatures. They also demonstrated better survival potential at all tested saline concentrations except 25 ppt where a significantly higher (p<0.0001) decay was observed. Therefore, enhanced survival exhibited by the multi-drug resistant enteropathogenic E. coli and S. paratyphi over a wide range of salinity levels suggest that they are able to remain viable for a very long time at higher densities in all seasons of the year in Vembanadu lake irrespective of saline concentrations, and may pose potential public health risks during recreational activities

Prevalence of multi drug resistant Escherichia coli serotypes in a tropical estuary,India

A toatal of 81 Escherichia coliisolates belonging to 43 different serotypes including several pathogenic strains such as enterotoxigenic E.coli isolated from a tropical estuary were tested against 12 antibiotics to determine the prevelance of multiple antibiotic resistance, antimicrobial resistance profiles and also to find out high risk source of contamination by MAR indexing.

Prevalence, distribution and drug resistance of motile aeromonads in freshwater ornamental fishes

The objective of the present study was to assess the prevalence of various motile aeromonads in freshwater ornamental fishes and to elucidate the antibiogram and beta hemolytic activity among the isolates. A total of 120 ornamental fish samples were screened and analyzed for Aeromonas spp. Motile aeromonads were isolated from 37.5% of the ornamental fish samples. Various species of motile aeromonads such as Aeromonas caviae, Aeromonas hydrophila, Aeromonas jandaei, Aeromonas schubertii, Aeromonas sobria, Aeromonas trota and Aeromonas veronii were detected. All the isolates were sensitive to ceftazidime, chloramphenicol, ciprofloxacin and gentamicin. Multiple antibiotic resistance was observed in 58% of the isolates.

Distribution, Extracellular Virulence Factors and Drug Resistance of Motile Aeromonads in Fresh Water Ornamental Fishes and Associated Carriage Water

During last decades there has been a continuous growth of aquaculture industries all over the world and taking into consideration the spurt in freshwater ornamental fish aquaculture and trade in Kerala, the present study was aimed to assess the prevalence of various motile Aeromonas spp. in fresh water ornamental fishes and associated carriage water. The extracellular virulence factors and the antibiogram of the isolates were also elucidated. Various species of motile aeromonads such as Aeromonas caviae, A. hydrophila, A. jandaei, A. schubertii, A. sobria, A. trota and A. veronii were detected. Aeromonas sobria predominated both fish and water samples. Extracellular enzymes and toxins produced by motile aeromonds are important elements of bacterial virulence. The production of extracellular virulence factors - proteases, lipase, DNase and haemolysin by the isolates were studied. All the isolates from both fish and water samples produced gelatinase and nuclease but the ability to produce lipase, caseinase and haemolysins was found to vary among isolates from different sources. Among the 15 antibiotics to which the isolates were tested, all the isolates were found to be sensitive to chloramphenicol, ciprofloxacin and gentamicin and resistant to amoxycillin. Local aquarists maintain the fish in crowded stressful conditions, which could trigger infections by the obligate/ opportunistic pathogenic members among motile aeromonads

Preparation, magnetic and EPR spectral studies of copper(II) complexes of an anticancer drug analogue

Ten new copper(II) complexes of five potential bisthiocarbohydrazone and biscarbohydrazone ligands were synthesized and physico-chemically characterized. The spectral and magnetic studies of compounds are consistent with the formation of asymmetric di-, tri- or tetranuclear copper(II) complexes of deprotonated forms of respective ligands. The variable temperature magnetic susceptibility measurements of all complexes showantiferromagnetic interactions between the Cu(II) centers, in agreement with very broad powder EPR spectra. However, frozen solution EPR spectral studies are found in contradiction with the solid-state magnetic studies and indicate that the complexes are not very stable in solutions; the possible fragmentations of complexes are found in agreement with MALDI MS results. The EPR spectral simulation of most of the compounds is in agreement with the presence of two uncoupled Cu(II) species in solution.

A Data Mining Approach for the Identification of Adverse Drug Events (ADE) resulting from Drug-Drug Interactions (DDI) to improve pharmacovigilance

In the current study, epidemiology study is done by means of literature survey in groups identified to be at higher potential for DDIs as well as in other cases to explore patterns of DDIs and the factors affecting them. The structure of the FDA Adverse Event Reporting System (FAERS) database is studied and analyzed in detail to identify issues and challenges in data mining the drug-drug interactions. The necessary pre-processing algorithms are developed based on the analysis and the Apriori algorithm is modified to suit the process. Finally, the modules are integrated into a tool to identify DDIs. The results are compared using standard drug interaction database for validation. 31% of the associations obtained were identified to be new and the match with existing interactions was 69%. This match clearly indicates the validity of the methodology and its applicability to similar databases. Formulation of the results using the generic names expanded the relevance of the results to a global scale. The global applicability helps the health care professionals worldwide to observe caution during various stages of drug administration thus considerably enhancing pharmacovigilance