DEVELOPMENT OF PEPTIDE-MODIFIED GEMINI SURFACTANTS AS NON-VIRAL GENE DELIVERY SYSTEM.

Gene therapy is a promising therapeutic approach for the treatment of inherited and acquired genetic disorders. Gemini surfactants are an emerging class of cationic lipids that has shown promising results in delivering genetic materials, particularly to the skin. The unique structure of the gemini surfactants imparts a design flexibility that permit the modulation of their physicochemical properties toward the enhancement of transfection efficiency. The behavior of gemini surfactants in complex biological systems may ultimately determine their efficiency and cytotoxicity. Correlating the biodistribution and biological fate of the nanoparticles to their chemical structure and physicochemical properties will inform the rational design process, resulting in the production of compounds with higher efficiency and reduced toxicity. In this research, a series of 22 novel peptide-modified gemini surfactants was evaluated. The aim of my research is to elucidate their structure-activity relationship and to determine their skin penetration behaviour. Transfection efficiency and cytotoxicity of the compounds were evaluated in murine keratinocytes and African green monkey kidney fibroblast cell lines. Physicochemical and structural properties of the nanoparticles were examined. Results revealed that the highest transfection efficiency and lowest cytotoxicity were associated with 16-7N(G-K)-16 gemini surfactant, showing an 8-fold increase in gene expression and a 20% increase in cell viability compared to the first-generation unsubstituted gemini surfactants. Furthermore, assessment of the contribution of the alkyl tail, in terms of length and saturation, indicated that compounds with hexadecyl tails were 5-10 fold more efficient than compounds with dodecyl and oleyl tails. To track the level of localization of the gemini surfactants in the skin, mass spectrometric analytical strategies were developed. The tandem mass spectrometric (MS/MS) dissociation behavior of the compounds was evaluated. Diagnostic product ions were selected for accurate identification of the gemini surfactants in complex biological matrices. Such knowledge was utilized to develop rapid and simple flow injection analysis (FIA)‐MS/MS method for the quantification of three peptide-modified gemini surfactants ex vivo in skin and phosphate buffered saline. Results showed a more than 11% deposition in the skin with minimum penetration into the saline compartment, suggesting the suitability of the delivery system to be used for topical application