This research focuses on the modeling of surfaces decorated by grafted polymers in order to understand their structure, energetics, and phase behavior. The systems studied include flat and curved surfaces, grafted homopolymers and random copolymers, and in the presence of solvent conditions, homopolymer melt conditions, and diblock copolymer melt conditions. We use self-consistent field theory to study these systems, thereby furthering the development of new tools especially applicable in describing curved particle systems and systems with chemical polydispersity. We study a polymer-grafted spherical particle interacting with a bare particle in a good solvent as a model system for a polymer-grafted drug interacting with a blood protein in vivo. We calculate the energy of interaction between the two particles as a function of grafting density, particle sizes, and particle curvature by solving the self-consistent field equations in bispherical coordinates. Also, we compare our results to those predicted by the Derjaguin approximation. We extend the previous study to describe the case of two grafted particles interacting in a polymer melt composed of chains that are chemically the same as the grafts, especially in the regime where the particle curvature is significant. This is expected to have ramifications for the dispersion of particles in a polymer nanocomposite. We quantify the interfacial width between the grafted and free polymers and explore its correlation to the interactions between the particles, and use simple scaling theories to justify our results. In collaboration with experimentalists, we study the behavior of the glass transition of polystyrene (PS) films on grafted PS substrates. Using the self consistent field theory methods described above as well as a percolation model, we rationalize the behavior of the glass transition as a function of film thickness, chain lengths, and grafting density. Grafting chemically heterogeneous polymers to surfaces in melt and thin film conditions is also relevant for both particle dispersion and semiconductor applications. To study such systems, we model a random copolymer brush in a melt of homopolymer that is chemically identical to one of the blocks. We modify the self-consistent field theory to take into account the chemical polydispersity of random copolymer systems and use it to calculate interfacial widths and energies as well as to make predictions about the window in which perpendicular morphologies of diblock copolymer are likely to form. We also explore the effect of the rearrangement of the chain ends on the surface energy and use this concept to create a simple modified strong stretching theory that qualitatively agrees with our numerical self-consistent field theory results. We explicitly study the system that is most relevant to semiconductor applications - that of a diblock copolymer melt on top of a substrate modified by a random copolymer brush. We explore the morphologies formed as a function of film thickness, grafting density, chain length, and chain blockiness, and make predictions about the effect of these on the neutral window, that is, the range of brush volume fractions over which perpendicular lamellae are expected to occur. / text

Το παρόν πόνημα αναπτύχθηκε προκειμένου να υποδειχθεί η σύνθεση και η μελέτη πολυλειτουργικών μαγνητικών νανοσωματιδίων τα οποία φέρουν μόρια της δραστικής φαρμακευτικής ουσίας Πακλιταξέλη (Ταξόλη - ΤΑXOLTM), ως εναλλακτικός τρόπος χορήγησης με υψηλή ακρίβεια στο στόχο, στο χρόνο και στην ποσότητα που απαιτείται για την αντιμετώπιση του καρκίνου του μαζικού αδένα, εκμεταλλευόμενοι τις ιδιότητες που περιλαμβάνουν το μικρό τους μέγεθος, στην κλίμακα του νανομέτρου,το μεγάλο εμβαδόν της επιφανείας τους, η δυνατότητα διαχείρισής τους από απόσταση και οι σχεδόν μηδενικές παρενέργειες.Τα σωματίδια ενίονται στον οργανισμό και μέσω της συστηματικής κυκλοφορίας κατευθύνονται με την βοήθεια ενός εξωτερικού μαγνητικού πεδίου στο όργανο-στόχο (στοχευμένη θεραπεία). Η Πακλιταξέλη αποτελεί ευρέως διαδεδομένο αντικαρκινικό παράγοντα, με σημαντικές ωστόσο παρενέργειες λόγω χαμηλής εκλεκτικότητας. Στην παρούσα μελέτη παρασκευάστηκαν μαγνητικά νανοσωματίδια οξειδίου του σιδήρου βασισμένα σε πολυμερικά μικύλλια PLA-PEG, τα οποία ενθυλάκωσαν την δραστική ουσία, προκειμένου να επιτευχθεί ο σκοπός παρατεταμένης παραμονής και στοχευμένης χορήγησης. Η διαδικασία του πειράματος περιλαμβάνει την σύνθεση παραμαγνητικών αλλά και μη μαγνητικών νανοφορέων, την ανάλυση των φυσικοχημικών ιδιοτήτων τους με τεχνικές σκέδασης του φωτός και ηλεκτροφόρησης και τον έλεγχο της σταθερότητάς τους σε διαφορετικές συνθήκες. Επιπροσθέτως, εξετάστηκε η δομή τους με ηλεκτρονική μικροσκοπία διαπερατότητας (TEM). Η μελέτη περιλαμβάνει επίσης μελέτες αποδέσμευσης της δραστικής ουσίας από τα νανοσωμάτια, αποβλέποντας στην απόδειξη της παρατεταμένης απελευθέρωσης, ενώ εν συνεχεία εξετάστηκε και η επίδραση εξωτερικού εναλλασσόμενου μαγνητικού πεδίου στο ρυθμό αποδέσμευσης της πακλιταξέλης. Παράλληλα, μελετήθηκε η τοξικότητα όλων των μαγνητικών νανοσωματιδίων που έφεραν πακλιταξέλη, με στόχο τον προσδιορισμό της επίδρασης στα επιθηλιακά νεοπλασματικά κύτταρα του μαστού. Τα αποτελέσματα της μελέτης οδήγησαν στην εξαγωγή ασφαλών συμπερασμάτων για τα μαγνητικά νανοσυστήματα πακλιταξέλης όσον αφορά τις ικανοποιητικές ιδιότητες κολλοειδούς σταθερότητας, ενθυλάκωσης και αποδέσμευσης της δραστικής ουσίας, επιτρέποντας τον σχεδιασμό και την πραγματοποίηση διερευνητικών ενεργειών για την πιθανή χρήση αυτών σε περαιτέρω κλινικές περιπτώσεις. / The aim of the current study is the synthesis and characterisation of multifunctional magnetic nanoparticles of the drug agent Paclitaxel (Taxol)in order to determine their use for the targeted treatment of cancer.This will be an alternative method of administration, which results in high accuracy on the target, boh in time and in the amount of drug required for the treatment of mammary cancer. We exploit tsome of the interesting properties of the nanoparticles for this purpose, such as their small size on the nanometer scale, the large area of their surface, their management ability to remotely and their virtually zero side effects. The particles are injected in the body via the systemic circulation driven by means of an external magnetic field to the target organ (targeted therapy). Paclitaxel is a widely used anticancer agent, with significant side effects, however, due to low selectivity. In the present study were prepared magnetic iron oxide nanoparticles based on polymeric micelles of PLA-mPEG, which encapsulate the active substance, in order to achieve the purpose of sustained residence and targeted delivery. The procedure of the experiment includes the synthesis of paramagnetic and non-magnetic nanoparticles, analysis of their physicochemical properties by techniques of light scattering and electrophoresis and examination of their stability in different conditions. Furthermore, their structure was examined by transmission electron microscopy. The study also includes release studies of the active substance of the nanoparticles, aiming to demonstrate the sustained release, and subsequently theexaminationof the effect of an external alternating magnetic field in the release rate of paclitaxel. We also studied the toxicity of all magnetic nanoparticles carrying paclitaxel to identify the effect on epithelial neoplastic breast cells. The results of the study led to reliable conclusions about magnetic nanosystems of Paclitaxel regarding satisfactory colloidal stability properties, encapsulation and release of the active substance, allowing the design and implementation of further exploratory actions for possible use in further clinical cases.

No description available.

Particle-laden flow in a microchannel resulting in aggregation of microparticles was investigated to determine the dependence of the cluster growth rate on the following parameters: suspension void fraction, shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster was found to increase linearly with suspension void fraction, and to obey a power-law relationships with shear strain rate as S^0.9 and channel-height to particle-diameter ratio as (h/d)^-3.5. Ceramic liposomal nanoparticles and silica microparticles were functionalized with antibodies that act as targeting ligands. The bio-functionality and physical integrity of the cerasomes were characterized. Surface functionalization allows cerasomes to deliver drugs with selectivity and specificity that is not possible using standard liposomes. The functionalized particle-target cell binding process was characterized using BT-20 breast cancer cells. Two microfluidic systems were used; one with both species in suspension, the other with cells immobilized inside a microchannel and particle suspension as the mobile phase. Effects of incubation time, particle concentration, and shear strain rate on particle-cell binding were investigated. With both species in suspension, the particle-cell binding process was found to be reasonably well-described by a first-order model. Particle desorption and cellular loss of binding affinity in time were found to be negligible; cell-particle-cell interaction was identified as the limiting mechanism in particle-cell binding. Findings suggest that separation of a bound particle from a cell may be detrimental to cellular binding affinity. Cell-particle-cell interactions were prevented by immobilizing cells inside a microchannel. The initial stage of particle-cell binding was investigated and was again found to be reasonably well-described by a first-order model. For both systems, the time constant was found to be inversely proportional to particle concentration. The second system revealed the time constant to obey a power-law relationship with shear strain rate as τ∝S^.37±.06. Under appropriate scaling, the behavior displayed in both systems is well-described by the same exponential curve. Identification of the appropriate scaling parameters allows for extrapolation and requires only two empirical values. This could provide a major head-start in any dosage optimization studies.

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.

The skin forms an attractive and accessible route for systemic delivery of drugs as alternative to other methods of administration, such as the oral and parental methods because of the problems associated with last mentioned methods. The lipophilic character of the stratum corneum, coupled with its intrinsic tortuosity, ensures that it almost always provides the principal barrier to the entry of drug molecules into the skin. Due to the fact that methotrexate (MTX) and acyclovir (ACV) have poor penetration properties through the skin, the aim of this study was to enhance the permeation of methotrexate and acyclovir with the use of two lamellar gel phase systems (LPGS) (Physiogel® NT and Physiogel® Dermaquadrille) and with Emzaloid® as transdermal drug delivery systems. Three different sets of experiments were done in this study: 1) the viscosity of the two Physiogel® creams was measured as an indication of stability and to determine whether the internal structure of the Physiogel® creams were affected by the investigated drugs; 2) the drug release rate from the three drug delivery vehicles was measured with a Vankel ® dissolution apparatus; 3) in vitro permeation studies were preformed using vertical Franz diffusion cells with human epidermal skin clamped between the donor and receptor compartments. The skin was hydrated with PBS buffer for one hour before 1% mixtures of the drugs in both the Physiogel® creams and Emzaloid® were applied to the donor chamber. Samples were taken at 2, 4, 6, 8, 10, 12 and 24 hours. It was then analysed by HPLC for methotrexate and acyclovir. The fluxes of drug permeation were determined. The viscosity measurements confirmed that the internal structure of the two Physiogel® creams was not influenced by the drugs. Acyclovir and methotrexate were both released from the delivery vehicles. There was an enhancement of acyclovir through the skin from one of the Physiogel® creams. The permeability of methotrexate in the presence of the two Physiogel® vehicles was not significantly enhanced. Emzaloid® as delivery vehicle increased the penetration of both drugs through the skin significantly. The lamellar gel phase system mimics the structure of the stratum corneum, but does not improve the drug permeation through the stratum corneum significantly. The utilisation of Emzaloid® as a drug delivery system could be advocated from these findings. As could be seen from the penetration profiles Emzaloid® was a superior delivery system for methotrexate and acyclovir compared to the lamellar gel phase systems. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.

There are no clinically approved drug delivery strategies designed for localized and sustained release to the injured spinal cord, two features which are heavily exploited in pre-clinical demonstrations of efficacy. We have previously shown that injection of drug loaded hydrogels into the intrathecal space is safe, minimally invasive, and drug release localized to the site of injection for up to one day. In the present work we developed a platform for sustained release from 1 to 28 days based on a physical gel of methylcellulose with hyaluronan and poly(lactic-co-glycolic acid) (PLGA) nanoparticles added as gelation agents. These composite hydrogels met the design criteria of injectability, fast gelation, minimal swelling, and 28 day stability. Sustained release of 6 therapeutic molecules from the composite was achieved by encapsulation in the particles or dissolution in the hydrogel. Release of PLGA encapsulated drugs from the composite was linear for 28 days. Drugs dissolved in the hydrogel were released by Fickian diffusion. The HAMC hydrogel/PLGA nanoparticle composite was delivered to uninjured and spinal cord injured rats and the animals monitored for 14 and 28 days respectively. The composite was well tolerated in the intrathecal space with no impact on motor function as determined by the BBB scale and minimal inflammation in both studies. No increase in reactive astrocytes or cavity volume was found in clip compression spinal cord injured rats, indicating that the composite did not affect these aspects of the secondary injury cascade. We then turned to sustained release of anti-NogoA, a promising neuroregenerative molecule typically delivered for 2 - 4 weeks. Formulations of anti-NogoA or a model IgG were prepared and release was demonstrated over 28 days in vitro. Bioactivity was assessed using a novel ELISA which utilized anti-NogoA / NogoA binding to detect only active antibody, advantageous because anti-NogoA release can now be easily optimized prior to in vivo studies of efficacy. The key features of current work are the development of an intrathecal drug delivery platform, demonstration of safety in a rat model, and formulation for use with anti-NogoA.

Immuno-nanoparticles of poly(ᴅ,ʟ-lactide-co-2-methyl-2-carboxytrimethylene carbonate)-g-poly(ethylene glycol) (poly(LA-co-TMCC)-g-PEG) have been used to target breast cancer cells through the specific binding of trastuzumab antibodies to over-expressed human epidermal growth factor receptor 2 (HER2). Small interfering RNA (siRNA) and antisense oligonucleotides (AONs) disrupt the synthesis of select proteins. It is hypothesized that oligonucleotides coupled to polymeric immuno-nanoparticles can be used for gene silencing and specifically to target luciferase. The first objective is to demonstrate the capacity to create dual functional micelles with antibodies and oligonucleotides. The second objective is in vitro testing of the nanoparticle for gene silencing activity. Oligonucleotides are conjugated to the nanoparticle by sequential click reactions of Diels Alder chemistry and copper catalyzed azide-alkyne cycloadditions, respectively. A luciferase assay is used to quantify knockdown of luciferase levels in SKOV-3luc cells (HER2+, luc+). When used in conjunction with a targeted drug delivery vehicle, the nanoparticles provide selective interactions with SKOV-3luc cells.

There are no clinically approved drug delivery strategies designed for localized and sustained release to the injured spinal cord, two features which are heavily exploited in pre-clinical demonstrations of efficacy. We have previously shown that injection of drug loaded hydrogels into the intrathecal space is safe, minimally invasive, and drug release localized to the site of injection for up to one day. In the present work we developed a platform for sustained release from 1 to 28 days based on a physical gel of methylcellulose with hyaluronan and poly(lactic-co-glycolic acid) (PLGA) nanoparticles added as gelation agents. These composite hydrogels met the design criteria of injectability, fast gelation, minimal swelling, and 28 day stability. Sustained release of 6 therapeutic molecules from the composite was achieved by encapsulation in the particles or dissolution in the hydrogel. Release of PLGA encapsulated drugs from the composite was linear for 28 days. Drugs dissolved in the hydrogel were released by Fickian diffusion. The HAMC hydrogel/PLGA nanoparticle composite was delivered to uninjured and spinal cord injured rats and the animals monitored for 14 and 28 days respectively. The composite was well tolerated in the intrathecal space with no impact on motor function as determined by the BBB scale and minimal inflammation in both studies. No increase in reactive astrocytes or cavity volume was found in clip compression spinal cord injured rats, indicating that the composite did not affect these aspects of the secondary injury cascade. We then turned to sustained release of anti-NogoA, a promising neuroregenerative molecule typically delivered for 2 - 4 weeks. Formulations of anti-NogoA or a model IgG were prepared and release was demonstrated over 28 days in vitro. Bioactivity was assessed using a novel ELISA which utilized anti-NogoA / NogoA binding to detect only active antibody, advantageous because anti-NogoA release can now be easily optimized prior to in vivo studies of efficacy. The key features of current work are the development of an intrathecal drug delivery platform, demonstration of safety in a rat model, and formulation for use with anti-NogoA.

Immuno-nanoparticles of poly(ᴅ,ʟ-lactide-co-2-methyl-2-carboxytrimethylene carbonate)-g-poly(ethylene glycol) (poly(LA-co-TMCC)-g-PEG) have been used to target breast cancer cells through the specific binding of trastuzumab antibodies to over-expressed human epidermal growth factor receptor 2 (HER2). Small interfering RNA (siRNA) and antisense oligonucleotides (AONs) disrupt the synthesis of select proteins. It is hypothesized that oligonucleotides coupled to polymeric immuno-nanoparticles can be used for gene silencing and specifically to target luciferase. The first objective is to demonstrate the capacity to create dual functional micelles with antibodies and oligonucleotides. The second objective is in vitro testing of the nanoparticle for gene silencing activity. Oligonucleotides are conjugated to the nanoparticle by sequential click reactions of Diels Alder chemistry and copper catalyzed azide-alkyne cycloadditions, respectively. A luciferase assay is used to quantify knockdown of luciferase levels in SKOV-3luc cells (HER2+, luc+). When used in conjunction with a targeted drug delivery vehicle, the nanoparticles provide selective interactions with SKOV-3luc cells.