الفهرس 
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Abstract
Selenium (Se) as one of the essential trace elements for human plays an essential role in preventing various diseases. But the high toxicity of Se limits its application. In this case, the element Se with zero oxidation state (Se0) has attracted our attention due to their favorable properties and unique bioactivities. However, Se0 is very unstable and easily changes into the inactive form. This work was conducted to synthesize stable selenium nanoparticles (SeNPs) using electrochemical method stabilized using biomaterials, namely, chitosan (CS) and Deoxyribonucleic acid (DNA), to optimize its synthesis by studying the influence of physicochemical parameters, and to explore the bioactivity of the stable Se0 nanoparticles (SeNPs). At the beginning, electrochemical method was used to prepare SeNPs stabilized by chitosan. The effect of different preparation parameters such as applied potential, electrolysis time and concentrations of chitosan on the CS-SeNPs properties were examined. The obtained CS-SeNPs were intensively characterized using different spectroscopic and microscopic techniques. The results manifested the formation of a controlable well-dispersed quasi-spherical chitosan stabilized SeNPs. The antioxidant capacity and antimicrobial potentials of pristine chitosan and electrochemically prepared CS-SeNPs were investigated. It was observed that pristine chitosan has no antioxidant ability. However, the in situ electrochemically formed CS-SeNPs displayed significant radical scavenging potential. In addition, antimicrobial activity tests revealed that introducing SeNPs to chitosan via the in situ electrochemical synthesis has significantly improved the antimicrobial potential of the realized CS-SeNPs against both gram-positive and gram-negative bacteria. On the other hand, DNA was inspected as a stabilizer biomolecule for selenium nanoparticles preparation using electrochemical method. But first, DNA behavior under the effect of the electrochemical method was examined. It was proposed to electrochemically transform the alkaline polyelectrolyte solution of DNA into DNA nanospheres (EsDNA). The result showed that stable DNA nanospheres for at least two months at 4 OC were successfully electro synthesized. Also, results revealed that DNA concentration and electrospherization time play a crucial rule on controlling the average size of the formed DNA nanospheres. To advance corresponding applications, we successfully electro self-assembled atenolol@DNA drug delivery system. Our finding demonstrated that the electrospherization as a cost benefit technique could be effectively employed to sustain the release of drugs. This delivery system achieved high Entrapment Efficiency %EE of 68.03±2.7% and moderate drug loading efficiency of 3.73%. Furthermore, electrosynthesis of selenium nanoparticles has been tested. Preliminary results revealed that SeNPs may be electrochemically prepared using DNA as stabilizer. Hence in the future, a complete and adequate study of electrochemical preparation of SeNPs stabilized by DNA will be our main concern.