Techn. Universiẗat, Diss., 2003--Berlin.

Yes / Hot melt extrusion has been used to produce a solid dispersion of the thermolabile drug artemisinin. Formulation and process conditions were optimised prior to evaluation of dissolution and biopharmaceutical performance. Soluplus®, a low Tg amphiphilic polymer especially designed for solid dispersions enabled melt extrusion at 110ºC although some drug-polymer incompatibility was observed. Addition of 5% citric acid as a pH modifier was found to suppress the degradation. The area under plasma concentration time curve (AUC0-24hr) and peak plasma concentration (Cmax) were four times higher for the modified solid dispersion compared to that of pure artemisinin. / EPSRC grant no (EP/J003360/1) and UKIERI: UK-India Education and Research Initiative (TPR 26).

Hot melt extrusion has attracted recent interest from the pharmaceutical industry and academia as an innovative drug delivery technology. This novel technique has been shown to be a viable and robust method for preparing different drug delivery systems including pellets, implants, tablets, capsules and granules. The aim of this research was to understand hot melt extrusion processing and explore its pharmaceutical applications. Two applications of hot melt extrusion (HME) have been investigated to improve the properties of poorly soluble thermolabile drugs; polymeric solid dispersions and solid state polymorphic transformation. HME is a solvent free, continuous and readily scalable technique which is increasingly being considered as a viable alternative to conventionally used batch techniques. However, the high temperature and shear forces imparted by the extrusion process can limit its applications with heat sensitive active pharmaceutical ingredients (APIs). Artemisinin was selected as a model drug which being thermolabile in nature and possesses processing challenges to processing HME. A low Tg amphiphillic copolymer, Soluplus® was selected as a matrix material. Drug-polymer compatibility was studied using rotational rheometry and thermal characterisation. The drug was found to be completely dissolved within the polymer, although some discolouration of the mixture was observed, indicating degradation of the API. The addition of a small percentage of citric acid to the formulation was found to prevent this degradation by increasing the pH. The dissolution profile of the formulation was approximately five times higher compared to that of the pure drug. The pharmacokinetic study was carried out using Albino rats to calculate bioavailability. The area under plasma concentration time curve (AUC0-24hr) and peak plasma concentration (Cmax) were four times higher for the prepared solid dispersion compared to that of pure artemisinin. Extruded solid dispersions were found to be amorphous in nature and maintained stability for 2 years. A second route to improving the solubility of poorly soluble APIs was also investigated. It was found that under carefully controlled conditions, high temperature extrusion (HTE) could be used to achieve polymorphic transformation with a number of APIs. This solvent-free continuous process was demonstrated with artemisinin, piracetam, carbamazepine and chlorpropamide. Artemisinin was used as a detailed case study of stability, solvent mediated transformation and mechanism of polymrophic transformation during extrusion, using computational modelling and model shear flows. At high temperature, phase transformation from orthorhombic to triclinic crystals was found to occur via the vapour phase. Under mechanical stress the crystalline structure was disrupted, leading to new surfaces being continuously formed and exposed to high temperatures; thus accelerating the transformation process. Polymorphic transformation during HTE was found to comprise three stages; i) preheating and conveying; ii) vapour phase transformation and size reduction and iii) continuous transformation and agglomeration. The triclinic form showed four times greater dissolution rate as compared to the orthorhombic form. The triclinic form showed two fold increase in bioavailability in Albino rats.

Hot melt extrusion has attracted recent interest from the pharmaceutical industry and academia as an innovative drug delivery technology. This novel technique has been shown to be a viable and robust method for preparing different drug delivery systems including pellets, implants, tablets, capsules and granules. The aim of this research was to understand hot melt extrusion processing and explore its pharmaceutical applications. Two applications of hot melt extrusion (HME) have been investigated to improve the properties of poorly soluble thermolabile drugs; polymeric solid dispersions and solid state polymorphic transformation. HME is a solvent free, continuous and readily scalable technique which is increasingly being considered as a viable alternative to conventionally used batch techniques. However, the high temperature and shear forces imparted by the extrusion process can limit its applications with heat sensitive active pharmaceutical ingredients (APIs). Artemisinin was selected as a model drug which being thermolabile in nature and possesses processing challenges to processing HME. A low Tg amphiphillic copolymer, Soluplus® was selected as a matrix material. Drug-polymer compatibility was studied using rotational rheometry and thermal characterisation. The drug was found to be completely dissolved within the polymer, although some discolouration of the mixture was observed, indicating degradation of the API. The addition of a small percentage of citric acid to the formulation was found to prevent this degradation by increasing the pH. The dissolution profile of the formulation was approximately five times higher compared to that of the pure drug. The pharmacokinetic study was carried out using Albino rats to calculate bioavailability. The area under plasma concentration time curve (AUC0-24hr) and peak plasma concentration (Cmax) were four times higher for the prepared solid dispersion compared to that of pure artemisinin. Extruded solid dispersions were found to be amorphous in nature and maintained stability for 2 years. A second route to improving the solubility of poorly soluble APIs was also investigated. It was found that under carefully controlled conditions, high temperature extrusion (HTE) could be used to achieve polymorphic transformation with a number of APIs. This solvent-free continuous process was demonstrated with artemisinin, piracetam, carbamazepine and chlorpropamide. Artemisinin was used as a detailed case study of stability, solvent mediated transformation and mechanism of polymrophic transformation during extrusion, using computational modelling and model shear flows. At high temperature, phase transformation from orthorhombic to triclinic crystals was found to occur via the vapour phase. Under mechanical stress the crystalline structure was disrupted, leading to new surfaces being continuously formed and exposed to high temperatures; thus accelerating the transformation process. Polymorphic transformation during HTE was found to comprise three stages; i) preheating and conveying; ii) vapour phase transformation and size reduction and iii) continuous transformation and agglomeration. The triclinic form showed four times greater dissolution rate as compared to the orthorhombic form. The triclinic form showed two fold increase in bioavailability in Albino rats.

Quantitative real-time PCR (QPCR) technology has been very useful for diagnosis of viral diseases. QPCR has recently reached a level of sensitivity, simplicity, and reproducibility which allows a large number of samples to be screened rapidly, make it a suitable tool for the clinical virology diagnostics. In this thesis, broadly targeted and degenerated quantitative QPCR assays were used. A somewhat novel single-tube real-time reverse transcription-polymerase chain reaction (QRT-PCR), with takes advantage of ability of rTth DNA polymerase to reverse transcribe RNA in the presence of Mn2+ at elevated temperatures and includes protection against amplimer contamination by using thermolabile UNG, was developed. A new technique for diagnostic of recent viral infection by detection of viral immunoglobulin M (IgM) was also developed. In the first paper, a sensitive single-tube QRT-PCR for detection of enteroviral RNA in patients with aseptic meningitis was presented. In the second paper, a single-serum-dilution real-time PCR-based PIA (PCR-enhanced immunoassay), called quantitative PIA (QPIA), to detect enterovirus IgM for diagnosis of EV infection in patients with aseptic meningitis, was also developed. In the third paper, a broadly targeted, simple, single tube degenerated quantitative QPCR technique for detection of JCV, BKV and SV40 DNA was developed. A conserved region of the VP2 gene of JCV, BKV and SV40 was targeted. A false positive result due to contamination with commonly used SV40 T-antigen plasmids was therefore avoided. In manuscript four, the QPIA assay provide a rational strategy for detection of EV IgM, allows the use of viral antigens isolate from newly diagnosed Type 1 diabetes patients (T1D-EV-QPIA) to measured IgM against diabetogenic viruses in serum from newly diagnosed T1D children, siblings, and healthy children. To conclude, novel broadly targeted real-time PCR methods for diagnosis of entero- and polyoma viral infections were developed.

La vaccination muqueuse est un moyen efficace de lutter contre les pathogènes qui utilisent les muqueuses comme porte d’entrée. Cependant, la vaccination muqueuse avec des antigènes non réplicatifs nécessite l’utilisation d’adjuvants. Les molécules de la famille de la toxine du choléra, l’entérotoxine thermolabile d’E.coli (LT), la toxine du choléra (CT) ainsi que le mutant LT-R192G et les sous-unités B non toxiques de ces toxines (LTB et CTB) ont été montrées augmenter les réponses immunitaires contre des antigènes coadministrés par voie muqueuse. Cependant leur mécanisme d’action est complexe et reste encore mal connu et des différences entre molécules entières et sous-unités B ont été rapportées ainsi que, pour une même molécule, des différences selon le modèle utilisé. Dans ce travail, nous avons étudié les effets de ces cinq molécules sur les réponses anticorps ainsi que sur les lymphocytes T CD4 dans un modèle murin d’immunisation intrarectale avec des pseudoparticules virales de rotavirus (VLP-2/6). Chez les souris non immunisées, nous avons montré que ces molécules, à l’exception de la CTB, diminuent in vitro les lymphocytes T régulateurs naturels CD4+CD25+Foxp3+, probablement par un mécanisme d’apoptose. Chez les souris immunisées, toutes les molécules étudiées induisent une même réponse anticorps sérique et fécale spécifique des VLP-2/6, qu’il s’agisse des molécules entières connues pour leur fort pouvoir adjuvant ou des sous-unités B qui, elles, ont été rapportées avoir un plus faible effet adjuvant voire un effet tolérogène dans certaines études. Concernant la réponse T CD4, les réponses spécifiques de l’antigène et de l’adjuvant ont été analysées. Des différences importantes ont été mises en évidence entre ces molécules. Notamment, seules les molécules entières (LT, LT-R192G et CT) induisent la production d’IL-2 et l’activation de lymphocytes T CD4+CD25+Foxp3- mémoires spécifiques de l’antigène tout en permettant la mise en place d’une régulation médiée par des lymphocytes T régulateurs CD4+CD25+Foxp3+ (boucle d’autorégulation), qui pourraient jouer un rôle majeur lors d’une réponse secondaire, afin d’éviter les réactions inflammatoires délétères. Malgré ces différences, toutes les molécules étudiées induisent la production d’IL-17, suggérant le rôle majeur de cette cytokine dans l’effet adjuvant.L’influence de la voie d’administration sur ces effets est en cours d’étude grâce à la comparaison avec la voie intranasale / Mucosal immunization is an important goal of vaccine development to protect against pathogens that use mucosa as portals of entry. However, the use of non-replicating antigens requires the addition of adjuvants.Cholera-like enterotoxins, cholera toxin (CT) from Vibrio cholerae and the heat-labile enterotoxin (LT) from toxinogenic strains of E. coli, as well as the mutant LR-192G and their B subunits (CTB and LTB) have been shown to increase immune responses against unrelated co-administered antigens by mucosal routes. However, their mechanism of action is very complex and not completely understood and differences exist between holotoxins and B subunits and within molecules, differences exist between the models used.In this work, we have studied the effects of these five molecules on antibody responses and on CD4+ T cell responses in a murine model of intrarectal immunization using rotavirus-like particles (2/6-VLP). In non-immunized mice, we have shown that all molecules, except CTB, decreased CD4+CD25+Foxp3+ natural regulatory T cells, probably by induction of apoptosis.In immunized mice, all molecules induced similar VLP-2/6 specific systemic and fecal antibody responses, teither he holotoxins, which are well known for their strong adjuvanticity or their B subunits with a less strong adjuvanticity but with also a tolerogenic effect in some studies.Regarding the CD4+ T cell response, antigen- and adjuvant- specific responses have been analysed. Important differences have been highlighted between the molecules. Among others things, only whole toxins (LT, LT-R192G and CT) trigger IL-2 production and activation of antigen specific memory CD4+CD25+Foxp3- T cells and at the same time antigen specific CD4+CD25+Foxp3+ regulatory T cells are activated which may control the effector response (Feedback loop regulation) and avoid deleterious inflammation. In spite of these differences, all studied molecules triggered IL-17 production, suggesting the major role of this cytokine in adjuvanticity. We are currently comparing the intrarectal and intranasl routes in order to evaluate the role played by the route of immunisation in different effects of these molecules

La vaccination muqueuse est un moyen efficace de lutter contre les pathogènes qui utilisent les muqueuses comme porte d'entrée. Cependant, la vaccination muqueuse avec des antigènes non réplicatifs nécessite l'utilisation d'adjuvants. Les molécules de la famille de la toxine du choléra, l'entérotoxine thermolabile d'E.coli (LT), la toxine du choléra (CT) ainsi que le mutant LT-R192G et les sous-unités B non toxiques de ces toxines (LTB et CTB) ont été montrées augmenter les réponses immunitaires contre des antigènes coadministrés par voie muqueuse. Cependant leur mécanisme d'action est complexe et reste encore mal connu et des différences entre molécules entières et sous-unités B ont été rapportées ainsi que, pour une même molécule, des différences selon le modèle utilisé. Dans ce travail, nous avons étudié les effets de ces cinq molécules sur les réponses anticorps ainsi que sur les lymphocytes T CD4 dans un modèle murin d'immunisation intrarectale avec des pseudoparticules virales de rotavirus (VLP-2/6). Chez les souris non immunisées, nous avons montré que ces molécules, à l'exception de la CTB, diminuent in vitro les lymphocytes T régulateurs naturels CD4+CD25+Foxp3+, probablement par un mécanisme d'apoptose. Chez les souris immunisées, toutes les molécules étudiées induisent une même réponse anticorps sérique et fécale spécifique des VLP-2/6, qu'il s'agisse des molécules entières connues pour leur fort pouvoir adjuvant ou des sous-unités B qui, elles, ont été rapportées avoir un plus faible effet adjuvant voire un effet tolérogène dans certaines études. Concernant la réponse T CD4, les réponses spécifiques de l'antigène et de l'adjuvant ont été analysées. Des différences importantes ont été mises en évidence entre ces molécules. Notamment, seules les molécules entières (LT, LT-R192G et CT) induisent la production d'IL-2 et l'activation de lymphocytes T CD4+CD25+Foxp3- mémoires spécifiques de l'antigène tout en permettant la mise en place d'une régulation médiée par des lymphocytes T régulateurs CD4+CD25+Foxp3+ (boucle d'autorégulation), qui pourraient jouer un rôle majeur lors d'une réponse secondaire, afin d'éviter les réactions inflammatoires délétères. Malgré ces différences, toutes les molécules étudiées induisent la production d'IL-17, suggérant le rôle majeur de cette cytokine dans l'effet adjuvant.L'influence de la voie d'administration sur ces effets est en cours d'étude grâce à la comparaison avec la voie intranasale