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The objective of this work was to optimize a thermosensitive in situ gelling formulation to improve intranasal and nose-to-brain delivery of the antiepileptic drug carbamazepine (CBZ). A preliminary procedure of vehicles obtained just mixing different fractions of poloxamer 407 (P407) and poloxamer 188 (P188) revealed preparations with phase transition temperatures, times to gelation and pH values suitable for nasal delivery. Subsequently, the mucoadhesive properties of the most promising formulations were tuned by adding hydroxypropylmethylcellulose types of different viscosity grades, and the effect of the adhesive polymers was evaluated by testing in vitro time and strength of mucoadhesion on specimens of sheep nasal mucosa. The formulation that showed the greatest mucoadhesive potential in vitro, with a time and force of mucoadhesion equal to 1746,75 s and 3.66×10-4 N, respectively, was that composed of 22% P407, 5% P188 and 0.8% HPMC low-viscous and it was further investigated for its ability to increase drug solubility and to control the release of the drug. Lastly, the capability of the candidate vehicle to ensure drug permeation across the biomimetic membrane Permeapad®, an artificial phospholipid-based barrier with a stratified architecture, and the same barrier enriched with a mucin layer was verified. The final formulation was characterized by a pH value of 6.0, underwent gelation at 32.33°C in 37.85 s, thus showing all the features required by in situ gelling thermosensitive preparations designed for nasal delivery and, more notably, it conserved the ability to favor drug permeation in the presence of mucin. These findings suggest that the optimized gelling system could be a promising and easy to realize strategy to improve CBZ delivery to the brain exploiting both a direct and indirect pathway.

The correlation between in vivo and in vitro data is yet not sufficiently optimized to allow a significant reduction and replacement of animal testing in pharmaceutical development. One of the main reasons for this lies in the poor mechanistic understanding and interpretation of the physical mechanisms enabling formulation rely on for deploying the drug. One mechanism that still lacks a proper interpretation is the kinetics of drug release from nanocarriers. In this work, we investigate two different types of classical enabling formulations - i) cyclodextrin solutions and ii) liposomal dispersions - by a combination of an experimental method (i.e. UV-Vis localized spectroscopy) and mathematical modelling/numerical data fitting. With this approach, we are able to discriminate precisely between the amount of drug bound to nanocarriers or freely dissolved at any time point; in addition, we can precisely estimate the binding and diffusivity constants of all chemical species (free drug/bound drug). The results obtained should serve as the first milestone for the further development of reliable in vitro/in silico models for the prediction of in vivo drug bioavailability when enabling formulations are used.

The brain as a drug target site remains a pharmaceutical challenge in spite of numerous efforts to enhance drug delivery to the brain. Nasal drug administration has gained interest among researchers, especially in the last decade, as it provides direct drug access into the brain. However, the nasal mucus and the surrounding environment often limit the use of nose as the administration site. Drug carriers such as liposomes have proven to be suitable to entrap a wide range of drugs protecting them from early clearance and degradation by nasal mucus, thus increasing the drug’s potency even in small volumes applicable to the nose. However, the physiological condition of the nose such as its tonicity is an important parameter to consider when developing liposomal drug formulations intended for nasal administration. In this PhD project, liposomes composed of soy-phosphatidylcholine comprised of six anti-inflammatory drugs, entrapped individually, were proven to be osmotically active within nasal tonicity environment. Liposomes shrank or swelled when exposed to a hypertonic or hypotonic environment, respectively. With precise tailoring of liposomal composition, the liposomes sensitivity to osmotic stress could be utilized to achieve controlled drug delivery within the nasal environment. The obtained data provide important information on the osmotic activity of liposomes and build the fundament for further development of innovative nose-to-brain drug delivery systems.

Summary Elevated serum cholesterol blood levels is one of the central risk factors for cardiovascular diseases. Lowering blood cholesterol have significant impact on lowering cardiovascular disease events. Inhibiting cholesterol absorption in small intestine can significantly lower serum cholesterol levels and thereby - lower cardiovascular events. Β-cyclodextrin (βCD)-dextran polymer is expected to form complexes with cholesterol and avoid absorption together with complexed cholesterol. In this thesis, we investigated βCD-dextran polymers ability to complexate cholesterol in simulation of gastric fluids. βCD-dextran polymer tablets at βCD conc. of 2.5mM complexed 0.0513 mg/ml crystalline cholesterol after 240 minutes in simulation of gastric fluids, while MβCD at conc. of 10mM complexed 0.45 mg/ml crystalline cholesterol. Extrapolated results to 10mM of βCD cons. shows that βCD-dextran polymer is capable of complexing significant amount of cholesterol. βCD-dextran polymer was successfully compressed into tablets with no visible defects of friability during handling. βCD-dextran polymer tablets sequestrate comparable amounts of food cholesterol, compared to experiments with crystalline cholesterol. Extrapolated results to physiological volumes of gastric fluids shows that βCD-dextran tablets corresponding to a concentration of βCD units of 10 mM were able to solubilize approx. 215 mg of crystalline cholesterol, and approx. 135 mg of food cholesterol after 240 minutes. Conclusion In simulation of gastric fluids, βCD-dextran polymer tablet can complex approximately 48% of cholesterol in comparison to cholesterol solubilized by MβCD powder. βCD-dextran polymer tablets show ability to complex similar and significant amounts of both crystalline and food cholesterol in simulation of gastric fluids. βCD-dextran polymer shows good compaction properties and were successfully compressed into tablets with no visible defects and no visible friability during handling.

Introduction: Liposomes as drug delivery systems has been widely studied as a way to solubilize poorly soluble drugs, reduce side effects of chemotherapeutics and increase circulation time in vivo. Since the first descriptions of liposomes over 60 years ago, they have shown tendencies to shrink and swell when the external environment of the liposomes is altered. This phenomenon has been studied in recent years and it is now known that liposomes’ shape is affected by osmotic pressure. Aim: The aim of this thesis was to clarify if changing the tonicity (i.e. concentration of solutes) outside of large unilamellar vesicles (LUVs) would affect the release of lipophilic drugs from them. Methods: LUVs were made by evaporating the solvent from a solution consisting of lipid, drug and solvents in phosphate buffered saline (PBS), and subsequently extruded to the desired sizes. The LUVs were characterized in terms of average diameter, size distribution, surface charge and percentage of drug entrapped inside the LUVs. To understand how tonicity affects the size of vesicles, the external environment of the LUVs was changed, and the size distributions of the LUVs were measured over time. The permeation properties of hydrocortisone and methylprednisolone were studied using Franz cells setup at different osmotic pressures using cellulose hydrate membranes or Permeapad® biomimetic barrier for both drug suspensions and drug-liposomal dispersions. Results and conclusion: We demonstrated that the LUVs shrank and swelled when the tonicity of the external environment was altered. We also demonstrated that the permeability of drugs (incorporated into LUVs) through cellulose hydrate membranes were highly affected by changes in tonicity. A significantly lower permeability for both hydrocortisone and methylprednisolone from the liposomal formulation in hypertonic external environment was measured, whereas no significant changes were found for the hypotonic external environment. The permeability studies on hydrocortisone incorporated LUVs employing the, Permeapad® showed a significantly higher permeability when changing the tonicity to hypotonic environment.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.ejps.2017.05.008. The aim of this study was to prepare and optimize a novel type of in situ gel-forming solid dosage form (gfSDF) to be used in the treatment of mucosal/skin ulcerations. For this purpose, a simple but reliable syringe-based hot melt/moulding method was employed. Chloramphenicol (antibiotic) and ibuprofen (anti-inflammatory) were chosen as model active pharmaceutical ingredients (APIs) to be loaded into the gfSDFs. To optimize the formulations, the gfSDFs of different compositions were studied in terms of APIs release from the matrix, solid-state characteristics, gellification properties and gfSDFs resistance to mechanical stress. Release studies showed that both APIs were released at a constant rate at different pH (pH 5 and 7.4, respectively) and the changes in the formulation composition affected the release behaviour. Differential scanning calorimetry (DSC) results evidenced the complete solubilization of both API in the solid matrix. Texture analysis showed that the gfSDFs were capable of swelling once in a contact with aqueous environment and that the textural properties changed extemporaneously from the solid to gel form. The gel formed after hydration exhibited high cohesiveness and adhesiveness, an indication of good mucoadhesion properties. Friability testing confirmed satisfactory physical strength for a solid dosage form.