The preparation of polyhedral oligomeric silsesquioxane nano conjugates containing antibiotic & antioxidant structures and analysis of biochemical activity

Studies carried out on nano-sized materials have been showing a great improvement in recent years. In order to contribute this development, this thesis was aimed to put forward biocompatible nano formulations for more effective antibiotics and antioxidants. For this purpose, easily functionalized, biocompatible nano POSS (polyhedral oligomeric silsesquioxane) structure that could be formulated was preferred. For this reason, the new formulations including POSS-based cefotaxime, metronidazole, melatonin and N-acetyl-L-cysteine (NAC) were synthesized. The structural characterization of materials were determined with NMR, FTIR, SEM-EDX and the thermal properties of structures were determined by thermal analysis systems like DTA, TGA and DSC. According to our antibacterial test results with E.coli bacteria, the values of IC50 was measured as 11,51±3,02 and 62,71±14,30µg/mL for POSS-Cefotaxime nano conjugate and cefotaxime, respectively. In addition, from the antibacterial test results with S.aureus bacteria, the values of IC50 was found to be 26,20±11,14 and 144,17±20,90µg/mL for POSS-Cefotaxime and cefotaxime. For POSS-Metronidazole nano conjugate, the values of IC50 was measured as 304,17±7,22 and 260,00±17,32µg/mL from the E.coli and S.aureus bacteria, respectively. Also, for metronidazole, the values of IC50 was measured as 1933,33±115,47 and 1416,67±144,33µg/mL from the E.coli and S.aureus bacteria, respectively. When compared to pure cefotaxime and metronidazole antibiotics, higher antibacterial activity has been achieved from POSS-Cefotaxime and POSS-Metronidazole nano conjugates with reduced IC50 values, which are statistically meaninful (p<0.05). POSS-Melatonin and pure melatonin ABTS radical scavenging activity was found to be %41,91±0,80 and %14,05±0,43 inhibition (p<0.05). In POSS-NAC conjugate, radical scavenging property was determined to be similar to the NAC pure compounds. In this thesis; nano-conjugated formulations were obtained by taking multiple active groups to one molecule in low dose applications offering relatively high antibacterial and antioxidant activities.