الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 261 |  |  |
| | | from | 261 | | |
Abstract
Carbon nanotubes (CNTs), an artificial allotrope of carbon that were discovered in 1991, are made of graphite and constructed in cylindrical tubes having nanometer diameter and several millimeters in length. The structures of CNTs are classified in four types: single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), triple-walled carbon nanotubes (TWCNTs) and multiwalled carbon nanotubes (MWCNTs). Due to their small size and mass, strong mechanical potency, and high electrical and thermal conductivity, CNTs have been successfully applied in different areas of pharmacy and medicine for drug preparation and therapy. They have been first proven to be an excellent nano-vehicle for the delivery of different therapeutic agents (drugs, biomolecules, etc.) directly into cells without metabolism by the body.
Thanks to their tiny structure, CNTs can effectively cross the cell membrane and directly deliver the transported drug into the cell. CNTs are able to maintain the drug intact during this transport and protect the drug against the metabolism by the body. The important characteristics of this nanotechnology in pharmaceutics are to revolutionize the methods of drug delivery since traditional drug administration cannot resolve the problems of toxicity and/or bioavailability of numerous effective drugs, thereby limiting their use in therapeutics. As CNTs are not water soluble, surface functionalization is required before their linkage with drugs or biomolecules. CNTs have also been proposed in biomolecule delivery such as DNA, proteins, antibodies, etc., for gene therapy, tissue regeneration, artificial implants and diagnosis of human diseases.
In light of this knowledge, the experimental work in the current study was divided into four chapters as the following:
Chapter I: Preparation and characterization of the microcapsulated sorafenib-loaded carbon nanotubes
The work in this chapter aimed to prepare and characterize novel microcapsulated sorafenib-loaded carbon nanotubes (microcapsulated SFN-loaded CNTs) formula that is able to improve the therapeutic efficacy of carried cargo against hepatocellular carcinoma (HCC) and subsequently investigate the antitumour activity of this formula. Sorafenib (SFN) was loaded on the functionalized CNTs through physical adsorption, and an alginate-based method was subsequently applied to the microcapsulated SFN-loaded CNTs. Two standard calibration curves of SFN in phosphate buffer (pH 7.4) and in 0.1 N HCl (pH 1.2) were constructed. The maximum absorbance of SFN in phosphate buffer (pH 7.4) and in 0.1 N HCl (pH 1.2) were found to be 265 nm and 259 nm respectively. Minimum variations were observed in the SFN adsorption capacity into the functionalized CNTs. The prepared microcapsulated SFN-loaded CNTs were characterized by using different techniques as Fourier Transform Infrared (FT-IR) spectroscopy, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermo-gravimetric analysis (TGA) and zeta potential (ZP).
Microcapsulated SFN-loaded CNTs was prepared by emulsification/internal gelation technique. The production yield of the prepared microcapsulated SFN-loaded CNTs was found to be 97.41% and the drug content was found to be 191.2/200g (95.6%). The in vitro release profile of SFN from the microencapsulated formula was assessed according to a dissolution medium pH shift method. Under acidic conditions mimicking those in the stomach (pH 1.2), only small amount of the drug was released during the first 2 hours. This could correspond to the drug molecules deposited on the surface of the microcapsules (MCs). Once these drug molecules were consumed, the insoluble nature of the pH-dependent polymer, sodium alginate (NaA) prevented the drug release from the microcapsulated SFN-loaded CNTs. On the contrary, the pH shift towards the alkaline medium (pH 7.4) that resemble the intestine, apparently enhanced the drug release to be efficiently completed within 5 hours.
Chapter II: In vivo pharmacokinetic behavior of the microcapsulated sorafenib-loaded carbon nanotubes
According to the obtained results, the used High performance liquid chromatography (HPLC) method was found to be satisfactory regarding its sensitivity and specificity with no interference with SFN determination from the endogenous substances of the plasma under the selected chromatographic conditions. The pharmacokinetic parameters showed that the area under curve (AUC) of SFN was seven-times higher in case of its administration in the form of the microcapsulated SFN-loaded CNTs compared to that of the conventional SFN (680.60 μg.hr/ml versus 96.87 μg.hr/ml, respectively). Additionally, the half-life (t1/2) of SFN was four-times prolonged after its administration in this new formula in comparison to its conventional form (18.43 hours versus 4.54 hours, respectively).
Chapter III: Stability studies of the microcapsulated sorafenib-loaded carbon nanotubes
Evaluations of the stability of the prepared MCs were carried out after storage at room temperature (25 °C), 30 °C, and 40 °C for three months in a relative humidity (RH) of 75±5% using a thermostatically-controlled cabinet. The microcapsulated SFN-loaded CNTs were tested for changes
in the morphological shape, the drug content, and the amount of drug released within 5 hours in comparison to the corresponding properties of a freshly prepared (pre-stored) MCs.
After a three months storage period at 25°C, 30°C and 40°C in a RH of 75±5%, no significant changes were observed in the morphological shape of the microcapsulated SFN-loaded CNTs as detected by SEM analysis. As well, these storage conditions were unable to significantly affect the drug content of the microcapsulated SFN-loaded CNTs.
Regarding the drug release profile, the obtained results indicated that storage of the microcapsulated SFN-loaded CNTs for three months under stress conditions induced a negligible decrease in the rate of the drug release from the stored MCs.
Chapter VI: Anticancer activities of the microcapsulated sorafenib-loaded carbon nanotubes
The in vitro thiazolyl blue tetrazolium bromide (MTT) anti-proliferative assay revealed that the drug-loaded CNTs formula was at least two-fold more cytotoxic towards Human hepatoma cell line-2 (HepG2) than was SFN itself. Moreover, the in vivo animal experiments proved that the innovative formula was superior to the conventional SFN at all assessed end points. Circulating AFP-L3% was significantly decreased in the microcapsulated SFN-loaded CNTs treated group (14.0%) in comparison to that of the DENA (40.3%) and SFN (38.8%) groups. This superiority was further confirmed by western blot analysis and immunofluorescence assessment of some HCC-relevant biomarkers, as well as, the histopathological examination.