The subject of this thesis was to develop and optimize delivery systems for plasmid DNA (pDNA) based on biocompatible polymers, in particular chitosan, suitable for non-viral gene therapy. At the onset of this thesis, studies had reported conflicting results on the efficiency of chitosan-based gene delivery systems. Therefore, structure-property relationships of chitosans as non-viral gene delivery systems in vitro and after lung administration in vivo were established for the first time. Polymer-pDNA complexes (polyplexes) based on conventional high molecular weight chitosans transfected cells in vitro and after lung administration in vivo. The chitosan polyplexes were, in contrast to polyplexes formed with the "golden standard" polymer polyethylenimine (PEI), essentially non-toxic at escalating doses. However, a very high physical stability of the chitosan-pDNA complexes together with a low buffering capacity of chitosan at the slightly acidic endo/lysosomal pH resulted in a slow onset of the gene expression and also in a lower efficiency of gene expression compared to PEI polyplexes. A slow and biodegradation-dependent release of pDNA from the chitosan polyplexes was concluded to be a rate limiting step for the efficiency of high molecular weight chitosan. The optimized polyplexes of high molecular weight chitosan (around 1,000 monomer units) showed aggregated shapes and gave increased viscosity at concentrations used for in vivo gene delivery. To improve the pharmaceutical properties and the delivery properties of chitosan polyplexes, low molecular weight chitosans were studied. Chitosans of around 18 monomer units retained the ability to protect pDNA against DNase degradation, but were more easily dissociated than those of higher molecular weight and had an efficiency comparable to that of PEI in vitro and in vivo. The pharmaceutical advantages of low molecular weight chitosan polyplexes compared to higher molecular weights are that there is less aggregation and no increased viscosity at the concentrations used for in vivo gene delivery. Coupling of an oligosaccharide targeting ligand to chitosan further increased the efficiency of some oligomer polyplexes. In conclusion, biocompatible chitosan is an interesting alternative to other non-viral gene delivery systems such as PEI.

Most pathogens enter the body via mucosal surfaces. In contrast to parenterally administered vaccination, mucosal vaccination has the advantage of eliciting both a systemic and a local mucosal immune response. An oral biodegradable adjuvant with these features would have great potential. This thesis has focused on the development of a new oral vaccine against diphtheria. Biodegradable polyacryl starch microparticles were used as a mucosal adjuvant. Diphtheria toxin or cross-reacting material of diphtheria toxin (CRM197) was covalently conjugated to the microparticles and fed to mice by oral gavage. Formaldehyde treatment was also studied as a means of either detoxifying (diphtheria toxin) or stabilising (CRM197) these formulations. All formulations given to mice orally or parenterally, but not intranasally, induced a strong systemic immune response and diphtheria toxin neutralising antibodies. Only formulations administered orally induced a mucosal IgA response as well. The non-toxic recombinant protein CRM197 proved to be a promising antigen candidate in an oral diphtheria vaccine when conjugated to the microparticles. Mild treatment of CRM197 with formaldehyde before conjugation to the starch microparticles potentiated the immunogenicity of the formulation. However, no immune response was detected in healthy volunteers after administration of this vaccine in a phase I trial. The possible reasons for the difference in response between mouse and man are discussed. The use of cDNA expression macro array technology was also evaluated as a tool in vaccine-related research. Tetanus toxoid and aluminium phosphate were used as model parenteral antigen and adjuvant. It was concluded that the antigen modulates the molecular mechanisms of the aluminium phosphate adjuvant to a greater extent than previously recognised.

Polyacryl starch microparticles have been developed as an oral vaccine adjuvant capable of inducing strong local and systemic immune responses in mice. In this thesis, the starch microparticles were studied in order to increase basic understanding of their function. In particular, the thesis addressed aspects of the uptake of the particles and their presentation to the immune system after different routes of administration, in correlation with the differentiation of the induced immune response. When using human serum albumin as a model antigen conjugated to the microparticles, it was found that the route of administration and the use of different combinations of routes, parenteral or oral, affect the profile (Th1/Th2 balance) of the induced immune response. It was also found that oral boosters are needed for the development of a local s-IgA response. Ligated mouse intestinal loops in combination with confocal laser-scanning microscopy demonstrated that the uptake of the particles by the intestinal mucosa takes place over the follicle-associated epithelium (FAE) that covers the Peyer’s patches. The particles are also taken up in the villus epithelium when conjugated with rCTB, a ligand to the GM1 receptor. This qualitative difference in uptake did not affect the induced immune response. Thus, the addition of rCTB to the microparticles did not improve or influence the profile of the immune response. Chronic stress, known to alter the barrier function of the FAE, increased the cellular response but did not affect the humoral immune response. Despite positive results in rodents, the particles were not able to boost a humoral immune response in man when tested with diphtheria toxin-cross reacting material (CRM197). Possible methods of improving the adjuvant effect in man are discussed.

Cellulose powders from various sources were manufactured and characterized to investigate the influence of their crystallinity index, surface area, and pore volume on sorption phenomena and the relevant pharmaceutical functionality. The influence of the cellulose crystallinity index on moisture sorption was important at low and intermediate relative humidities. At high relative humidities, properties such as surface area and pore volume took precedence in governing the moisture sorption process. The theory of physical adsorption of gases onto fractal surfaces was useful for understanding the distribution of water in cellulose and the inner nanoscale structure of cellulose particles. It was found that, as a consequence of swelling, moisture induces a fractal nanopore network in cellulose powders that have a low or intermediate degree of crystallinity. On the other hand, no swelling occurs in highly crystalline cellulose powders and moisture sorption is restricted to the walls of the open pores. No correlation was found between the cellulose crystallinity index and the incorporation and release of nicotine in cellulose mixtures. By loading nicotine in highly porous matrices of the Cladophora sp. algae cellulose, higher stability against oxidative degradation, higher loading capacity, and more steady release into an air-stream was achieved than when commercially available microcrystalline cellulose was loaded. It was also shown that, by manipulating the structure of cellulose, the undesired hydrolysis of acetylsalicylic acid in mixtures with cellulose can be avoided. It was suggested that a broad hysteresis loop between the moisture adsorption and desorption curves of isotherms at low relative humidities could be indicative of an improved compatibility between acetylsalicylic acid and cellulose. In all, this thesis demonstrates how the pharmaceutical functionality of microcrystalline cellulose can be improved via engineering of the structure of native cellulose powders.

<p>The preparation of multiple unit tablets was investigated in this thesis with the intention of gaining a deeper understanding of some of the factors that influence the properties of such tablets.</p><p>Initially, three different types of pellets (drug, soft and disintegrant pellets) were combined as a model to investigate the ability of the mixture to form disintegrating tablets. The proportions of the different pellets and the type of disintegrant used were factors that independently influenced the tablet properties. Furthermore, the properties of tablets containing drug pellets barrier-coated with an aqueous polymer dispersion were also found to depend on the coating thickness and the compaction pressure.</p><p>When compacting pellets barrier-coated with a solvent-based polymer solution without incorporating excipient particles in the tablet formulation, a high pellet porosity was advantageous to preserve the original drug release profile, even though highly porous pellets became more densified and deformed than pellets of lower porosity.</p><p>The influence of the properties of excipient particles on the deformation<b> </b>of the reservoir pellets was also studied and, although the amount of flattening of the pellets was only slightly affected, changes in the pellet shape (irregularity) with alterations in the porosity and size of the excipient particles were more substantial. In contrast, the properties of the excipient particles did not affect the pellet densification.</p><p>The solvent-based coating used was able to adapt to the changes in volume and shape that the pellets underwent during compaction. The coating structure appears to be changed by compaction and it is proposed that the final structure of the coating is the net effect of two parallel processes, one reducing and one prolonging the transport time of the drug across the coating. Thus, the drug release could be maintained or even prolonged after compaction, despite extensive structural changes of the reservoir pellets.</p>

<p>This thesis presents two new concepts in oral drug administration and the results of evaluation of some relevant formulation factors.</p><p>Investigation into improving the homogeneity of mixtures for tableting indicated that it may be possible to obtain interactive dry mixtures of micronised drugs containing drug proportions as low as 0.015% w/w. By studying the relationship between disintegration time and tensile strength, it was found that the microstructure surrounding the disintegrant particles may influence the disintegration process. Therefore, avoidance of excipients which are highly deformable or very soluble in water will result in more rapid disintegration. Further, it is possible to increase the bioadhesive properties of a non-bioadhesive carrier material by forming interactive mixtures containing a fine particulate bioadhesive material.</p><p>The new sublingual tablet concept presented is based on interactive mixtures consisting of a water-soluble carrier covered with fine drug particles and a bioadhesive component. With this approach, it is possible to obtain rapid dissolution in combination with bioadhesive retention of the drug in the oral cavity. Clinical data indicate that this allows rapid sublingual absorption while simultaneously avoiding intestinal absorption. </p><p>An individualised dose administration system is also presented. This system is based on the use of standardised units (microtablets), each containing a sub-therapeutic amount of the active ingredient. The required dose is fine-tuned by electronically counting out a specific number of these units using an automatic dose dispenser. A patient handling study supported the suggestion that the dosage of some medications can be more easily and safely individualised for each patient with this method than by using traditional methods of mixing different standard tablet strengths or dividing tablets.</p>

<p>Drug delivery to the nasal and ocular mucosa faces several obstacles. One of these is from the effective clearance mechanisms present in the nose and eye. Polymer gels with suitable rheological properties can facilitate the absorption of poorly absorbed drugs by increasing the contact time of the drug with the mucosa. This has been attributed to the rheological and mucoadhesive properties of the gel. The main objective of this thesis was to investigate the importance of these features for the anticipated in vivo contact time, here exemplified by the ocular and nasal routes of administration.</p><p>The in situ gelling polymer gellan gum was found to have a favourable rheological and in vivo performance. When administered in the nasal cavity of rats, a gel was formed that could remain at the site of administration for up to 4 hours. In addition, the epithelial uptake and transfer of a 3 kDa fluorescein dextran was higher than for a mannitol solution. Therefore, it was concluded that a gellan gum formulation should be a promising strategy for nasal drug delivery.</p><p>The potential mucoadhesive properties of a variety of polymer gels were investigated using a rheological method and by measuring the tensile force required to detach the gel from a mucosa. With both methods the rheological properties of the gel were a determining factor for the results obtained. The rheological method was found to have several limitations. One of these was that a positive response, interpreted as mucoadhesion, was only seen with weak gels. The tensile method could, in contrast, detect strengthening of the mucus only for strong gels. However, this method reflects the in vivo performance of the gel better than the rheological method.</p><p>Finally, dielectric spectroscopy was explored as a tool for investigating the likelihood of intimate surface contact between the gel and the mucus layer. This novel approach involved determining the ease with which a charged particle can pass the gel-mucus interface layer, and may enable the study of the events at the interface closer to the molecular level, than is possible with the rheological and tensile strength methods.</p>

<p>Drug transport across the intestinal epithelium is roughly predicted from permeability values obtained from Caco-2 cell monolayers. This thesis examines the important role of <i>pH</i> and extracellular additives for increasing the reliability and predictivity of the <i>in vitro</i> screening system, Caco-2.</p><p>It was shown that the passive transport of ionizable compounds may be biased by a false efflux or uptake component, when applying a physiological <i>pH</i>-gradient across the membrane. <i>pH</i> also affected the amount of compound available at the transporter-binding site. Therefore, <i>pH</i> dependence should be considered in studies of such compounds and of drug-drug interactions involving efflux transporters. It was also shown that proton-dependent apical uptake or basolateral efflux should be studied both with and without a <i>pH</i> gradient over the whole monolayers. </p><p>The two extracellular additives, bovine serum albumin (BSA) and the solubilizing agent, Cremophor^® EL, also influenced Caco-2 permeabilities. BSA applied to the receiver side increases, and to the donor side decreases drug permeation according to the drug’s protein binding capacity. Thus, the absorptive transport for both passive and active compounds is favoured, giving a physiologically sound improvement of the Caco-2 cell model. Inclusion of BSA increased both the predictivity and quality of permeability studies, particularly of highly lipophilic, BCS class II compounds. Passive and active transport processes could also be distinguished after accounting for unbound concentrations. The overall effect of Cremophor^® EL on the permeability to a drug was compound-specific and probably dependent on micellar incorporation. Cremophor^® EL can therefore not be recommended. </p><p>Neither <i>pH</i> nor BSA affect the functionality of transporters such as P-glycoprotein. However, efflux ratios of ionizable or protein bound drugs are altered in the presence of a <i>pH</i>-gradient or BSA, indicating that an experimental system without protein or <i>pH</i> gradient can over- or underestimate active and passive efflux in drug transport.</p>

<p>Spray drying is a method with a high potential in the preparation of protein particles suitable for pulmonary delivery. However, surface induced denaturation of bio-molecules during atomization and subsequent drying can be substantial and it is therefore important to develop new formulation concept for concurrent encapsulation and stabilization of proteins during spray drying. Hence, with an overall objective to increase the knowledge of the formation of particulate systems for systemic administration of proteins by spray drying, the first part of this thesis, systematically investigated the particle formation by droplet size and particle size measurements. It was described how specific properties, such as the solubility and the crystallization propensity of the solute, can affect the product, e.g. the particle size, internal structures, and possibly particle density. A new method using atomic force microscopy (AFM) for the assessment of the effective particle density of individual spray-dried particles was demonstrated. In the second part, two different formulation concepts for encapsulation of protein during spray drying were developed. Both systems used non-ionic polymers for competitive adsorption and displacement of protein from the air/water interface during spray drying. The aqueous two-phase system (ATPS) of polyvinyl alcohol (PVA) and dextran, and the surface-active polymers, hydroxypropyl methylcellulose (HPMC) and triblock co-polymer (poloxamer 188) used for in situ coating, proved efficient in encapsulation of a model protein, bovine serum albumin (BSA). Inclusion of polymeric materials in a carbohydrate matrix also influenced several particle properties, such as the particle shape and the surface morphology, and was caused by changes in the chemical composition of the particle surface and possibly the surface rheology. In addition, powder performance of pharmaceutical relevance, such as dissolution and flowability, were affected.</p>

<p>The appearance of adverse drug reactions is a common reason for hospitalization in Western countries. Research on underlying biological mechanisms for interindividual variability in drug response aims to better identify patients with exceptional genetic traits, disease conditions or risk of drug-drug interactions and thereby help to prevent adverse drug reactions. </p><p>Active transport mechanisms are involved in the absorption and disposition of several therapeutic agents. The main objective of this thesis was to investigate factors potentially affecting transport proteins and thus contributing to variability in drug absorption and disposition. Studies of physiological, genetic, environmental, and pathological factors were included. The main focus was the two ATP-binding cassette (ABC) transporters: P-glycoprotein 170 (Pgp) and Breast Cancer Resistance Protein (BCRP). </p><p>Quantification of transport protein mRNAs along the human intestine indicated that eight of the nine investigated drug transporters were expressed in a region-dependent manner. Effects of drug-drug interactions may therefore vary depending on the site of absorption. The genetic aspect was illustrated by identification of sequence variation in the gene encoding BCRP, the most highly expressed ABC transporter along the human intestine. Drug-drug interactions are important environmental causes of interindividual variability. An evaluation of the effects of Pgp-mediated drug-drug interactions showed that patients receiving Pgp inhibitors had elevated serum concentrations of the Pgp substrate digoxin and that digoxin concentrations were positively correlated with the number of co-administered Pgp inhibitors. The final topic in this thesis was that of drug-disease interactions. BCRP and Pgp were down-regulated during active inflammation in patients with ulcerative colitis. This may contribute to altered concentrations of drug in the intestinal mucosa during periods of inflammation and possibly to changes in drug absorption.</p><p>To summarize, results of this thesis emphasize the complex background to the interindividual variability of drug transport proteins, where physiological, genetic, environmental and pathological factors all can contribute.</p>