الفهرس 
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Abstract
In this work, different series of amine oxide-based conventional and Gemini surfactants were synthesized. Preparation of these surfactants was carried out by esterification of diethanolamine with different fatty acids (octanoic, dodecanoic and hexadecanoic). The esterified products were then alkylated with dibromo alkane with different chain lengths (2, 6 and 10). Then oxidized with hydrogen peroxide producing both conventional and Gemini amine oxide-based surfactants.
Spectroscopic data including FTIR, 1H-NMR and Elemental analysis confirmed the chemical structures of the prepared conventional and Gemini amine oxide surfactants.
The surface activity of the prepared compounds was evaluated using surface tension technique. The surface parameters including surface and interfacial tension, emulsification power, critical micelle concentration, effectiveness, efficiency, maximum surface excess and minimum surface area were determined at 25°C. The thermodynamic parameters including standard free energy change (ΔG°) of both adsorption and micellization were calculated at 25°C. Our results showed that all the prepared conventional and Gemini amine oxide surfactants have good surface active properties. By close inspection, it was found that the Gemini amine oxide surfactants were more surface active than the conventional ones.
In addition, all the prepared amine oxide surfactants were tested as antimicrobial agents against different strains of bacteria and fungi. For all the synthesized conventional and Gemini amine oxide surfactants, their antimicrobial activity values indicate that most of these compounds have significant antimicrobial activity towards all the tested species, and there was a non-linear relationship between the alkyl chain length of the prepared surfactants and their antimicrobial activities.
The antimicrobial activity of these amine oxide surfactants lies in their interaction with biological membranes. As a result of this interaction, which might be limited by the cell wall of microbial spores and some vegetative cells, the structure and permeability of cellular membranes are altered and inhibition of membrane-dependent processes occurs, followed by the death of the cell.
It was obvious that the chemical structure of amine oxides with their biological activities revealed that the presence of appropriate hydrophobic alkyl chain length on the polarized hydrophilic (N-O) group is essential for the antimicrobial and cytolytic activities of these compounds. Amine oxides bearing these two chemical groups are surface-active, exhibiting cationic activity in acidic solutions. These properties facilitate the adsorption and penetration of amphiphilic molecules of amine oxides into the membranes, inducing changes in their molecular organization. This leads to an alteration in permeability and in the osmotic equilibrium, causing the death of cells.
Finally, these compounds were applied in drug delivery by solubilization of a hydrophobic drug Coenzyme (Q10), where the synthesized surfactants showed high solubility for (Q10) drug as a hydrophobic drug when compared with water. It was noticed that the dependence of the solubilization power on the chemical structure of the surfactant molecules is obvious.
The solubilization is the process of incorporating the solubilizate into the micelles while the surfactant concentration in solution is above the CMC. Also, it must be remembered that the core of micelles is considered to be the major site of solubilization of most hydrophobic drugs. in our study as mentioned above, Gemini surfactants have surface activity higher than the conventional ones, suggesting that theses Gemini surfactants aggregated easily possibly due to the spacer group in their structure, leading to micelle formation at low CMC values and also leads to micellar growth resulting in increased volume in the inner core of the micelle, where the drug would be located.
It was noticed that the solubility of the drug (Q10) increased linearly with increasing the shaking time as a consequence of the association between the drug and micelles.
At last, Due to their extremely low toxicity, low skin irritation and ease of degradation, amine oxide surfactants, are safe and recommended to use in a variety of medical fields.