Injuries to the central nervous system (CNS) have traumatic consequences such as irreparable disability due to the inability of the CNS to regenerate injured nerve fibres. The aim of the work presented here was to develop a scaffold which potentially provides guidance to axons in the injured spinal cord thus facilitating signal transduction. A poly-(lactic-co-glycolic acid) (PLGA, PLA:PGA ratio of 75:25) flat sheet membrane scaffold was created using phase inversion with N-methyl pyrrolidinone (NMP) as the solvent and water as the non-solvent for immersion precipitation. PLGA flat sheet membranes were exposed to surface treatments including aminolysis, peptide immobilisation and ozonation in order to achieve higher cell attachment of PC12 cells, a cell line which was cloned from a solid pheochromocytoma tumour of white rats, and used as a tool for measurement of regeneration. Cell attachment studies revealed no significant difference in cell attachment between modified and not-modified PLGA flat sheet membranes. However, the absence of foetal calf serum (FCS) resulted in fivefold higher cell attachment compared to medium supplemented with 10% FCS. A second scaffold was produced by electrospinning 10% (w/w) PLGA in a chloroform:methanol (CHCl3:MeOH) mixture in ratio of 3:1 resulting in a nanofibrous scaffold. Optimum settings for electrospinning were found to be 3 ml/h feeding rate, 15kV applied voltage and 11cm collector-to-needle distance. Random and aligned PLGA nanofibres were produced, with a fibre diameter of 530±140nm. PC12 cells attached and differentiated to the nanofibrous scaffold. When exposed to NGF these cells stopped dividing and extended neurites. On random fibres, neurite orientation was random, whereas on aligned fibres 63% of neurites grew with the fibre orientation ±15��ᵒ. After 7 days of exposure to NGF, cells had 1-4 neurites on random fibres, reaching a maximum length of 188μm, whereas on aligned fibres, cells had 1-2 neurites, reaching a maximum length of 400μm. PLGA nanofibres were also investigated as a delivery vehicle for bioactive molecules. For this, poly-L-lysine (PLL) was incorporated into electrospun PLGA nanofibres via emulsion electrospinning. PLGA-PLL nanofibres were significantly larger than PLGA nanofibres having a diameter of 830±190nm. In order to visualise the incorporation of PLL, FITC-PLL was electrospun und the resulting nanofibres fluoresced greed. Attachment of PC12s to PLGA-PLL nanofibres was not significantly different compared to PLGA nanofibres. Aligned PLGA-PLL nanofibres were shown to promote neurite outgrowth of PC12s with resulting neurites of up to twice the length compared to aligned PLGA nanofibres. The results suggest that PLGA nanofibres strongly influences neurite organisation, which is potentially useful for future therapeutic approaches. The work in this thesis has shown that electrospun PLGA nanofibre mats have the potential to be used as scaffolds for spinal cord repair addressing topographical guidance and delivery of bioactive molecules to the site of injury.

A major challenge in drug development is ensuring that each new candidate drug is delivered to the appropriate location, in a timely manner and at an optimal concentration. Low drug solubility, drug instability, drug degradation, drug toxicity, or rapid clearance from the body can reduce the effectiveness of an otherwise promising drug candidate. Formulations such as nano/microparticles and melt extruded pellets made with synthetic and natural polymers are effective solutions for the advancement of drug delivery technology. These polymeric formulations can provide controlled release of therapeutic agents by delivering constant doses over long periods, cyclic dosages, and tunable release of both hydrophilic and hydrophobic drugs in order to improve the bioavailability and bioactivity of a drug. PLGA-based nanoparticles formed by emulsion or nanoprecipitation techniques can be designed to have a range of degradation times. Particle degradation and drug release kinetics can be controlled by the physiochemical properties of the polymer, such as molecular weight, hydrophobicity, and polydispersity. This study is focused on developing polymeric-based delivery systems for small and large molecules as treatment strategies for arthrofibrosis and bone tissue engineering. In developing arthrofibrotic treatments, several mechanosignaling and biochemical pathways were targeted using small molecule therapeutics such as blebbistatin (a myosin II ATPase inhibitor), paclitaxel (a microtubule stabilizer), sulfasalazine (a kappa B suppressor), beta-aminopropionitrile (a lysyl oxidase inhibitor) and cis-hydroxyproline (inhibits the formation of stable triple helix structure of collagen). The aforementioned drugs were delivered either via PLGA micro/nanoparticles or via pellets formed by melt extrusion. From the studies performed, it was found that blebbistatin delivered by PLGA nanoparticles could reversibly inhibit fibroblast contractile activity and could significantly inhibit collagen synthesis. These findings lay the foundations for further optimization of drug dosing and potentially enabling a new drug delivery technology for treating arthrofibrosis. Sulfasalazine delivered by melt extruded PLGA pellets significantly inhibited myofibroblast numbers as deduced from α-SMA expression and col1A1 gene expression results and thus can be considered a potential treatment for arthrofibrosis. For bone tissue engineering, plasmids encoding differentiation promoting factors or growth factors such as BMP-2 (pBMP-2), FGF-2 (pFGF-2), PDGF (pPDGF) and VEGF (pVEGF) were delivered via polyethylenimine (PEI), a cationic carrier that interacts electrostatically with negatively charged DNA. The formed nanoplexes were either tested directly or by coating them onto biocompatible titanium metal implants and cultured with human bone marrow derived mesenchymal stem cells (hBMSCs). We found that the combinatorial delivery of pBMP-2 and pFGF-2 significantly enhanced bone regeneration as deduced from Runx-2, alkaline phosphatase and osteocalcin gene expression results as well as from data yielded from alizarin red staining assays and atomic absorption spectroscopy where calcium ion levels were measured. It was also found that pBMP-2 nanoplex-coated titanium discs could significantly enhance bone regenerative gene expression for osteocalcin, Runx-2, and alkaline phosphatase as well as enhance calcium ion expression in human adipose derived mesenchymal stem cells (hADMSCs). Thus, it can be concluded that pFGF-2 and pBMP-2 nanoplexes have osteogenic potential and our studies demonstrate a new methodology with the potential to modify titanium disc implant surfaces for the purposes of enhancing osseointegration.

Immunotherapy has been widely investigated in cancer, infectious diseases and allergies for prevention or amelioration of disease progression. In the case of vaccines, the key cellular target in stimulating an effective and appropriate immune response is the professional antigen presenting cell or dendritic cell (DC). Cancer vaccines are primarily aimed at the activation of a tumor-specific cytotoxic T lymphocyte (CTL) response whilst vaccines to allergies are aimed at reducing IgE responses. Such vaccines normally involve the administration tumor-associated antigens (TAAs) for cancer, or antigens (Ags) derived from infectious microbes and allergens in the case of allergies. Ags, whether derived from tumor or allergen, can be combined with adjuvants, that include immunostimulatory molecules recognized by the pathogen associated receptors expressed by DCs and can trigger the activation/maturation of DCs. Co-delivery of an appropriate adjuvant with an Ag can stimulate DCs to subsequently promote a robust Ag-specific CTL response which may favor anti-tumor immunity. Cancer vaccines have been widely investigated in the clinics as a complementary therapy to surgery, radiation and chemotherapy. Activation of CTLs against tumor cells that express TAAs could lead to the complete eradication of a cancer and prevent its reoccurrence. In this study I developed microparticles using a polyanhydride polymer prepared from 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) and 1,6-bis(p-carboxyphenoxy) hexane (CPH) that has shown inherent adjuvant properties. I prepared 50:50 CPTEG:CPH microparticles encapsulating a model tumor Ag, ovalbumin (OVA), and synthetic oligonucleotide containing an unmethylated CpG motif, CpG, as an adjuvant. CpG has shown significant potential as an adjuvant for TAA-based vaccines leading to significant anti-tumor immune activity. I have shown that mice vaccinated with OVA-encapsulated 50:50 CPTEG:CPH microparticles developed OVA-specific CTL responses. These mice showed enhanced survival compared to the control treatment groups when challenged with OVA expressing tumor cells . In a more novel in-situ cancer vaccine, TAAs from dying tumor cells (caused by certain chemotherapeutic drugs) can be used as the source of Ags delivered to DCs. The presence of an adjuvant with dying cancer cells can assist in appropriate maturation of DCs so as to promote the generation of an effective tumor/TAA-specific CTL response against released TAAs. In this work I developed a therapeutic in situ tumor vaccine encapsulating a chemotherapeutic drug and CpG. Doxorubicin (Dox) is a widely used chemotherapeutic drug that induces tumor cells to undergo an immunogenic form of apoptosis. Sustained release of Dox in solid tumors of mice can cause the release of a variety of TAAs which can be presented by DCs and, in the presence of CpG, stimulate a strong anti-tumor CTL response. I prepared formulations of poly(lactic-co-glycolic acid) (PLGA) particles loaded with Dox and CpG which demonstrated sustained release of their cargo. I show that among various formulations of Dox and CpG, co-delivery of Dox and CpG in the same PLGA particles in-vivo showed the highest reduction in tumor growth and longest survival when compared to treatment groups of PLGA particles delivering Dox and CpG either alone or in combination. PLGA particles have also been investigated as a prophylactic vaccine delivery system that generates a robust Ag-specific CTL response. This system has been employed for the development of vaccines against various infectious diseases and allergies. However, there has been conflicting opinions regarding the optimum size of PLGA particles required to stimulate an active CTL response. Thus, I developed different sizes of PLGA particles encapsulating OVA and CpG to study the relationship of particle size with the magnitude of OVA-specific CTL responses. I showed that the degree of particle uptake and activation of DCs increased with decreasing size of PLGA particles. I also showed that immunization of mice with 300 nm sized particles demonstrated a higher proportion of OVA-specific CTLs and increased the secretion of IgG2a antibody responses. I also evaluated the efficacy of these particles with a clinically relevant Ag, Dermatophagoides pteronyssinus-2 (Der p2). Mice vaccinated with different sizes of PLGA particles loaded with CpG and coated with Der p2 displayed different magnitudes and types of immune activation against Der p2. The small sized particles decreased the airway hyperresponsiveness associated with allergy-induced asthma. The presence of CpG in the PLGA particle vaccines also reduced the airway hyperresponsiveness. This thesis research has contributed to the identification and development of a delivery system for Dox in combination with CpG which gives sustained release of these molecules within tumors and show the longest survival in tumor bearing mice. This study also optimized the size of PLGA particles for the delivery of vaccine to produce a robust Ag specific immune response for development of vaccination against intracellular diseases, cancer and allergy.

Cancer is a collection of diseases that is characterized by an uncontrolled proliferation of aberrant cells. The conventional treatment strategies including chemotherapy and radiotherapy prove detrimental to healthy cells and are unable to combat primary and secondary metastases. Hence immunotherapy is gaining momentum in cancer clinics and translational research labs as an alternative safer and more efficacious approach to tumor therapy. Vaccines based on antigen alone lack the ability to optimally activate the antigen presenting cells (APCs) including dendritic cells (DCs) to generate significantly greater antigen-specific T cell responses. A typical strategy to overcome this limitation has been the use of adjuvants in order to improve the immunogenicity of the vaccines. A newer class of adjuvants called toll like receptor (TLR) ligands recognize pathogen associated molecular patterns (PAMP) and thus elicit a Th-1 polarized response. The hypothesis of the current research is that co-delivery of antigen and adjuvant in a microparticulate carrier will elicit a strong cell-mediated immune response conferring anti-tumor immunity. Furthermore, we proposed that a combination of TLR ligands when co-delivered with an antigen will be able to mount a synergistic anti-tumor response in comparison to the delivery of antigen alone. There were three primary objectives of the study; 1) Fabrication, process design optimization and characterization of antigen and adjuvant co-loaded microparticles (MP), 2) Study the ability of the MP fabricated in step 1 in eliciting a potent immune response in a murine model by various routes of administration and 3) Study the effect of the various treatment as prophylactic and therapeutic cancer vaccines in a murine tumor model. Objective 1 was achieved by optimizing various process parameters including PLGA type and concentration, surfactant concentration and modification of a previously reported double emulsification solvent evaporation technique. Process optimization lead to the development of the following 5 treatment groups, a) Empty PLGA MP, b) OVA PLGA MP, c) OVA + CpG PLGA MP, d) OVA + poly I: C PLGA MP and e) OVA + CpG + poly I:C tri-component PLGA MP. The optimized microparticles exhibited a mean particle size of 1.5 πm with a smooth spherical surface and a desirable biphasic release pattern of the entrapped components. Results from step 2 indicated the ability of the co-delivery and the tri-component systems to generate several fold higher immunostimulatory response in comparison to the group treated with antigen alone. Of the two routes of administration tested, the intraperitonial (i.p) route gave the strongest response followed by intramuscular (i.m) route. A synergistic antibody response response was observed upon vaccination with the tri-component model. Prophylactic vaccination studies showed that the co-delivery and tri-component system affording the strongest protection against aggressive tumor growth. The therapeutic studies also indicated enhanced tumor protection and 2-fold improvement in survival times when the mice vaccinated with the co-delivery and tri-component MP carriers in comparison to vaccination with microparticles loaded with antigen alone. The carriers also showed strong evidence for the generation of anti-tumor immunogenic memory. In summary, the current study has laid an interesting premise for the use of immunotherapy using a combination of antigen and TLR adjuvants alone or in conjunction with chemotherapy as a treatment strategy for tumor therapy. This research is expected to lead to the utilization of PLGA delivery systems as novel carriers for cancer immunotherapy.

Metastatic breast cancer is a leading cause of cancer-related mortality worldwide. While existing interventions are effective at treating localized tumors, disseminated malignancies remain incurable. Vaccine-induced anti-tumor immunity is a promising approach for treating disseminated tumors, as immune responses are systemic, have antigen-restricted cytotoxicity, and generate protective immune “memory” populations. Our group has developed a novel heterologous prime/boost vaccine protocol that treats established 4T1 murine mammary tumors. Briefly, this approach entails a vaccine prime consisting of tumor lysate antigens encapsulated within poly(lactic-co-glycolic) acid (PLGA) microparticles (MPs). The vaccine prime was followed by a vaccine boost consisting of tumor lysates plus adjuvants. Spontaneous 4T1 lung metastasis was evaluated at a pre-determined endpoint in vaccinated versus untreated mice. Vaccinated mice demonstrated significant, but incomplete, reductions in metastatic tumor burdens relative to untreated control mice. Encouraged by these results, we evaluated additional vaccine variations with the goal of improving therapeutic responses. The addition of immunomodulatory chemotherapy or checkpoint blockade immunotherapy failed to significantly improve the initial vaccine’s efficacy. Conjugation of streptavidin/biotin complexes to the PLGA MP significantly improved vaccine efficacy, with vaccinated mice demonstrating 88% less metastatic tumor burdens than their untreated counterparts. These findings illustrate that vaccines based upon PLGA MP-mediated delivery of tumor lysates can form the basis of an effective treatment for metastatic breast cancer and suggest that similar approaches may be both efficacious and well-tolerated in the clinic.

In this research a variety of drug delivery systems were synthesized and characterized. For the most part, these consisted of a matrix of poly(lactic-co-glycolic acid) (PLGA), polyethylene glycol (PEG), and polyvinyl alcohol (PVA) containing encapsulated anticancer drugs as chemotherapy agents. The drug release from biodegradable nanoparticles was analyzed mathematically using new approaches that simultaneously incorporates the three major mechanisms of release: initial burst, nanoparticle degradation-relaxation, and diffusion. The theoretical release studies were corroborated experimentally by evaluating the cytotoxicity effectiveness of PHT-427-loaded nanoparticles over pancreatic cancer cells in vitro. These studies showed that the encapsulated PHT-427 drug in the nanoparticles is more accessible and thus more effective when compared with the drug alone. Also, the PHT-427-loaded nanoparticles cytotoxicity was evaluated in vivo studies with pancreatic tumors. The results show that the drug is more effective when is loaded into polymeric nanoparticles compared to drug alone, by reducing orthotopic pancreatic tumor growth. In addition, a selection of hydrophobic to hydrophilic drugs were encapsulated into polymeric nanoparticles to find optimal drug loadings by using single or double emulsification techniques. The release of these drugs from PLGA nanoparticles was evaluated to determine the overall release profile characteristics. The encapsulation of the drug pemetrexed was improved by using polyethileneimine. The high positive charge density of polyethileneimine causes a strong electrostatic interaction with the carboxylic acids of pemetrexed; this complex decreases the solubility of pemetrexed and boosts the encapsulation efficiency. Additionally, a drug release mathematical analysis that considers the effects of the temperature of release was effectively established. The analysis was performed by using two different models: the first one simultaneously incorporates the mechanisms of initial burst and nanoparticle degradation - relaxation, and the second model, besides of the mechanisms of the first model, includes the diffusion of the drug. Both models were successfully employed to describe the experimental release of rhodamine 6G from PEGylated nanoparticles at different temperatures. From the parameters obtained by the fit using each model, it was possible to define a set of new relations of the form of Arrhenius to estimate the parameters of release at other temperatures.

Biodegradable polymer materials, specifically poly(lactic-co-glycolide) (PLGA) can be used as bone replacements for bone regeneration. Scaffolds can be prepared to be porous to induce bone growth into a scaffold so that it is replaced with natural tissue as the polymer degrades. However, simply using PLGA will result in formation of scar tissue rather than regeneration of natural bone. Therefore focus has turned to attaching growth factors to the PLGA molecules to elicit a specific cellular response when the implant is placed in the body. Site-directed immobilization utilizes specific groups on both the biomaterial and biomolecule so that growth factors can be oriented in a specific manner for increased cellular response. In this research, exposed carboxyl groups on a non end-capped PLGA were modified with bishydrazide spacer molecules of varying length for the eventual attachment of a biomolecule via carbodiimide chemistry. The number of hydrazide groups attached to the surface could be controlled to investigate the effects of the spacer length on protein immobilization. Both vascular endothelial growth factor (VEGF) and parathyroid hormone (PTH) were used in these studies. These two molecules have different target cells and actions, although both can play a role in bone formation. Both molecules have carbohydrate residues that were oxidized with periodate to form aldehyde moieties that were able to react with the hydrazide spacers to form a stable bond between the spacer and protein. The use of a spacer enhanced the binding accessibility of the protein as compared to randomly adsorbed protein. The shortest and longest of the spacers resulted in the highest amount of protein, with corresponding results for antibody binding. The modification of PLGA functional groups with a spacer molecule indicates that this material could be used for site-directed immobilization for any application, simply by tailoring the reaction between the biomaterial and biomolecule.

Insulin, a relatively low molecular weight protein has been used for decades in the treatment of diabetes; it has well-defined properties and delivery requirements. Due to the current increase of diabetes in the world improved insulin delivery systems could significantly influence the treatment of diabetes and the quality of life of the affected people. The main objective of this work was to encapsulate insulin in polymer nanoparticles of Poly (DL-Lactic-Co-Glycolic Acid) (PLGA) and poly vinyl alcohol (PVA). Preliminary results of these functional therapeutic nanoparticles prepared with PVA and PLGA by using a double emulsion method (water/oil/water) were obtained in terms of encapsulation efficiency and effective insulin release from the nanoparticles. Assessing the bioactivity of insulin once encapsulated and released is not trivial, thus an indirect protein assay was developed to effectively and easily assess the activity of proteins going through these processes. Trypsin, a proteolitic enzyme was used as model protein to investigate the biological activity of encapsulated and released biomolecules. The activity of trypsin towards a synthetic substrate, DL-BAPNA was used to measure the enzyme kinetics and activity before encapsulation, while encapsulated and after the enzyme was released from the nanoparticles. Results show that the enzyme maintained substantial activity while encapsulated and after its release. It is anticipated that the biological activity after being released from the nanoparticles will remain biologically active, however, biological assays remain to be performed to corroborate this argument. In addition to release experiments with trypsin and insulin, other proteins were also studied. In all cases the release form the nanoparticles at 37 °C exhibited a three stage release process, The release process will be modeled according to developed mathematical models that consider initial burst of molecules, degradation of polymer and diffusion of molecules from the nanoparticles.

Embryonic stem (ES) cells have the capacity to form any cell type. However, their propagation and differentiation is limited by current two dimensional (2D) culture techniques which offer little flexibility in terms of surface structure and functionalisation with bioactive molecules. The aim of the current work was to produce a novel scaffold that could manipulate ES cell behaviour using both architectural and biological cues. Electrospinning is a flexible technique that creates nonwoven meshes that mimic the fibrous architecture of the ECM. Initial work focused on investigating the suitability of electrospun poly(lactic-co-glycolic acid) (PLGA) meshes for 2D and three dimensional (3D) culture of mouse ES cells, with the hypothesis that the fibrous architecture would assist in maintaining pluripotency. The study also sought to functionalise the scaffolds with biologically active molecules. Heparan sulphate proteoglycans (HSPGs) reside at the cell surface and within the ECM where they mediate growth factor binding, assist cell attachment and stabilise the ECM. Furthermore, ES cells modulate their own microenvironment by controlling the composition of heparan sulphate (HS), regulating the binding of growth factors such as fibroblast growth factor (FGF) family members. Therefore, we aimed to immobilise HS and heparin (a highly sulphated structural analogue of HS) on the fibre surface in a form that was freely accessible for protein/cell interactions and that retained its biological activity. Electrospinning parameters were optimised to produce microfibre electrospun meshes with an average fibre diameter of 570nm. Cell morphology, proliferation and pluripotency were monitored using an Oct4-GFP reporter cell line and results compared with flat spin coated films. To investigate the potential for 3D culture, spinning parameters were altered to increase fibre diameter to >3micro metre with infiltration assessed using pro-migratory E-cadherin-/- ES cells. Scaffolds were coated with plasma polymerised allylamine (ppAm) to enable non-covalent immobilisation of HS/heparin. Ligand binding assays with the link module of TSG-6 and anti-heparin/HS antibodies were used to probe HS/heparin presentation on the fibre surface. The biological activity of the immobilised HS/heparin was analysed by testing the ability of coated scaffolds to rescue the neural differentiation capacity HS deficient EXT1-/- ES cells. Finally, human ES cells were cultured on the surface of ppAm scaffolds +/- HS in both unconditioned and mouse embryonic fibroblast (MEF) conditioned media for 5 days. Both microfibre meshes and flat spin coated films supported the attachment, growth and pluripotency of mouse ES cells. Cells adopted distinct morphologies, with mouse ES cells aggregating in rounded colonies on microfibre scaffolds and demonstrating increased spreading on spin coated films. Fibres >3micro metre created a thicker mesh with potential for 3D culture supporting the infiltration of E-cadherin-/- ES cells. ppAm enabled non-covalent immobilisation of HS/heparin in a form that was free to participate in protein interactions and which presented essential sulphation motifs within the HS/heparin chains. Bound HS was biologically active and functioned in synchrony with FGF4 to enhance neural differentiation of EXT1-/- ES cells. The constructs also supported the attachment and growth of human ES cells, with HS functionalised scaffolds demonstrating a slight increase in compatibility during culture in unconditioned media. The successful functionalisation of electrospun meshes with HS/heparin creates a highly versatile scaffold for ES cell culture and differentiation. The architecture of the meshes can be manipulated to either serve as a fibrous substrate for maintenance of pluripotency or support the formation of complex cell interactions present in vivo. The immobilisation of HS provides an extra dimension of versatility, as the scaffold can be tailored with specific HS species, potentially enabling the differential regulation of growth factor binding.

Charles University Faculty of Pharmacy in Hradci Králové Department of Pharmaceutical Technology Consultant: PharmDr. Ondřej Holas, PhD. Student: Petra Staňková Title of Thesis: Pharmaceutical applications of polyesters as drug nanocarriers Nanoparticles are nowadays intensively studied and perspective type of a drug carrier. Its potential is based on a possibility of targeted drug delivery and controlled drug release. The theoretical part is about nanoparticles types, polymers derived from α-hydroxyacids (PLA, PGA, PLGA). Focus is given on methods of nanoparticles preparation: dispersion of preformed polymers or the polymerization of monomers. The modification of particles surface and practical use of nanomedicine in healthcare are described in other chapters. The research in experimental part is focused on the influence of different types of PLGA and their weighing on the size, polydispersity, nanoparticles zeta potential and encapsulation efficiency of rhodamine B. Nanoparticles were prepared by nanoprecipitation method or by solvent evaporation method. The Zetasiser ZS 90 device was used to measure the size of the nanoparticles and to measure zeta potential. The result of the research shows the most suitable weighing for creation of nanoparticles is 25 mg. The samples of this weighing show a...