A study of the genotoxicity of polyhydroxybutyrate

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dc.contributor.authorAli Mohammed, Abdulaziz Qaid
dc.date.accessioned2014-11-03T02:20:19Z
dc.date.available2014-11-03T02:20:19Z
dc.date.issued2009
dc.descriptionPhDen_US
dc.description.abstractThe purpose of this study is to determine the genotoxicity of polyhydroxybutyrate (PHB), produced in short solid fibre form and manufactured by School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia, using three different tests: The Salmonella mutagenicity test (Ames test), in vitro mammalian chromosomal aberration test and gene expression analysis. PHB was tested at various concentrations (0.3125, 0.625, 1.25, 2.5 and 5 mg/ml) in all the three tests. For the Ames test, PHB was incubated with special genotype variants of the bacterium Salmonella typhimurium, which carry mutations in several genes. Five tester strains (TA1535, TA1537, TA1538, TA98 and TA100) were used, both with and without metabolic activation system S9 mix and the test was assessed based on the number of revertant colonies. Simultaneously, negative control tests using sterile distilled water and positive control tests using sodium azide, 9-aminoacridine hydrochloride monohydrate (98%) and 4-Nitro-O-phenylenediamine (98%) without metabolic activation system (S9) and 2-aminoanthracene with metabolic activation system (S9) were carried out. To assess the chromosomal aberrations, human osteoblast cell lines (HOS, CRL-1543) from American type cell culture were exposed to PHB, sterile distilled water (Negative control) and Mitomycin C (Positive control), both with and without metabolic activation system S9 mix. For the gene expression analysis, the fibroblast cell lines MRC-5 were treated with PHB and incubated for 1, 12, 24 and 48 hours separately for each concentration. Total RNA was isolated and analysed for the expression of p53, c-myc, bcl-xl and bcl-xs genes. The results of Ames test showed that the average number of revertant colonies per plate treated with PHB (28 to 344 colonies/plate without S9 and 150 to 499 colonies/plate with S9) was less than double as compared to that of negative control (147 to 346 colonies/plate without S9 and 340 to 443 colonies/plate with S9). The absences of increase in the number of revertant colonies by at least double with the test material indicate that PHB was non-mutagenic. In the case of chromosome aberration test, there was no indication of any mutagenicity due to PHB on the HOS cell line as revealed by the mitotic index values [3.55(0.06) to 4.95(0.77) per cent without S9 and 3.10(0.14) to 5.20(0.98) per cent with S9]. Also, no chromosome aberrations were observed in the HOS cell lines treated with PHB. The results of gene expression analysis carried out on fibroblast cell line (MRC-5) treated with PHB at different timings did not show over or under expression of the genes, p53 (Mean IDV range from 36100 to 36295), c-myc (Mean IDV range from 33110 to 33270), bcl-xl (Mean IDV range from 31230 to 31443) and bcl-xs (Mean IDV range from 33103 to 33290) as compared to that of negative controls (Mean IDV range from 31230 to 36240). Hence, the present study indicates that PHB produced by School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia is non-genotoxic under the present test conditions.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/273
dc.language.isoenen_US
dc.subjectBiological Scienceen_US
dc.subjectGenotoxicityen_US
dc.subjectBiomaterialen_US
dc.titleA study of the genotoxicity of polyhydroxybutyrateen_US
dc.title.alternativeA synthetic biomaterialen_US
dc.typeThesisen_US
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