الفهرس 
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Abstract
This thesis mainly sought to produce and characterize a new ascorbic acid (AA) - compound has a high stability profile. In addition, it investigated the cytotoxic effects and the proliferation rate of the synthesized composite on adult human dermal fibroblasts cells. It also sheds light on the immense therapeutic potential of AA as a free radical scavenger. For decades, it has been a common practice throughout the world to use AA in cosmetic preparations and skin care blends. Ascorbic acid has been extensively utilized for maintaining healthy resilient skin and treating hyperpigmentation. AA is essential for rebuilding skin collagen as it promotes collagen biosynthesis and generally functions as an antioxidant mitigates and neutralizes the effects of free radicals which are generating ubiquitous within our bodies by overexposure to UV radiation, environmental pollutants and stress. It also decreases hyperpigmentation because it is affecting the levels of glutathione which inhibits melanin production; it converts the inactive oxidized glutathione back to its active form. Despite all these benefits of AA, we claim that most of them have not been optimally exploited yet because AA associated with many problems such as its poor stability (in air, light, and at high temperatures) and its rapid decomposition into inactive compounds. Drug delivery system was a key to overcome many of these problems. As it is well known, the main goal of drug delivery is to reformulate the existing drugs for maintaining desirable pharmacological outcomes so the proposed nano-composite (CMC-nHAp-AA) was specifically tailored for minimizing AA degradation rate. The proposed composite for this study is based on hydroxyapatite (HAp) as a vehicle for delivering AA which is coated with biocompatible polymer. Nano-hydroxyapatite nHAp was an excellent candidate for the suggested model due to its exceptional biocompatibility and bioactivity. Its slowly disintegrating nature and being not exhibiting any cytotoxic effects evidenced again that it was as a sensible choice for the desired purpose. Carboxymethyl cellulose (CMC) has been suggested as a suitable polymer (protective coating matrix for AA) after running a set of careful comparisons among number of polymers. The reason behind selecting CMC is that, it is non-toxic, odorless and makes the product has a colorless nicely smooth texture without gelling even in the presence of Ca2+ ions. HAp nanoparticles were successfully synthesized. Various precursors such as (calcium hydroxide, calcium chloride and calcium nitrate as sources of calcium - orthophosphoric acid and diammonium phosphate as sources of phosphorus) have been tried in the pursuit of preparing nano-sized HAp. HAp nano-powder was obtained via the wet chemical precipitation reaction. We also obtained clear colorless solution of HAp. nHAp was synthesized at both lower and higher reactions temperature. Several attempts to determine the optimal pH for the reaction were conducted comparing between amonia and NaOH as pH adjusters. Hence, there was an urgent need for an in-depth study into the toxicity effects of these materials to be deemed as safe materials. Toxicity and safety screening reports included; evaluation of cell viability and IC50 (50٪ inhibitory concentration) values. At highest concentration the IC50 value was 0.199μg/mL. Comparative proliferation rate of cultured dermal fibroblasts cells was accurately evaluated and compared to untreated control. Detailed thermo- and photo-stability studies were performed in which produced nano-composite (CMC-nHAp-AA) showed great stability against sunlight and heat, whereas showed low stability against lasers. Physico-chemical properties of nHAp were characterized using X-Ray Diffractometery (XRD), Fourier Transform Infra-Red spectroscopy (FTIR) and Energy Dispersive X-Ray Spectroscopy (EDX). The size and morphology of the synthesized composite were characterized by Transmission Electron Microscopy (TEM). Scanning Electron Microscopy (SEM) was applied to image aggregated particles. The produced nano-composite (CMC-nHAp-AA) is expected to have great potential applications in anti-aging due to having a high proliferative capacity which lasts longer than AA.