Polyhydroxyalkanoates (PHA) are naturally occurring biopolyesters that have great potential in the medical field. However, the leachables resulting from sterilization process of the biomaterials may exert toxic effect including genetic damage. Here, we demonstrate that although gamma-irradiation of poly(3-hydroxybutyrate-co-50 mol % 4-hydroxybutyrate) [P(3HB-co-4HB)] did not cause any change in the morphology by scanning electron microscopy, there was a significant degradation of this copolymer where the molecular weight was reduced by 37% after sterilization indicating the generation of leachables. Therefore, further investigation on the ability of the extract of this poststerilized copolymer to induce mutagenic effect was performed using Ames test (S. typhimurium strains TA1535 and TA1537) and umu test (S. typhimurium strain TA1535/pSK1002). Additionally, the capability of the extract to induce clastogenic effect was determined using Chinese hamster lung V79 fibroblast cells. Our results showed that with and without the presence of S9 metabolic activation, no mutagenic effects were observed in both Ames and umu tests when treated with P(3HB-co-4HB) extract. Similarly, treatment of P(3HB-co-4HB) extract in V79 fibroblast cells showed no significant production of micronuclei when compared with the positive control (Mitomycin C). Together, these results indicate that leachables of poststerilized P(3HB-co-4HB) cause no mutagenic and clastogenic effects.
Among the various biomaterials available for tissue engineering and therapeutic applications, microbial polyhydroxyalkanoates offer the most diverse range of thermal and mechanical properties. In this study, the biocompatibility of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB); containing 50 mol % of 4-hydroxybutyrate] copolymer produced by Delftia acidovorans was evaluated. The cytotoxicity, mode of cell death, and genotoxicity of P(3HB-co-4HB) extract against V79 and L929 fibroblast cells were assessed using MTT assay, acridine orange/propidium iodide staining, and alkaline comet assay, respectively. Our results demonstrate that P(3HB-co-4HB) treated on both cell lines were comparable with clinically-used Polyglactin 910, where more than 60% of viable cells were observed following 72-h treatment at 200 mg/mL. Further morphological investigation on the mode of cell death showed an increase in apoptotic cells in a time-dependent manner in both cell lines. On the other hand, P(3HB-co-4HB) at 200 mg/mL showed no genotoxic effects as determined by alkaline comet assay following 72-h treatment. In conclusion, our study indicated that P(3HB-co-4HB) compounds showed good biocompatibility in fibroblast cells suggesting that it has potential to be used for future medical applications.
Plant styryl-lactone derivatives isolated from Goniothalamus sp. are potential compounds for cancer chemotherapy. In this study, we have examined the mechanisms of apoptosis induced by altholactone, a stryl-lactone isolated from the Malaysian plant G. malayanus on human HL-60 promyelocytic leukemia cells. Flow cytometric analysis of the externalization of phosphatidylserine (PS) using the annexin V/PI method on altholactone treated HL-60 cells showed a concentration-dependent increase of apoptosis from concentrations ranging from 10.8 (2.5 microg/ml) to 172.4 microM (40 microg/ml). Pre-treatment with the antioxidant N-acetylcysteine (1 mM) completely abrogated apoptosis induced by altholactone, suggesting for the involvement of oxidative stress. Further flow cytometric assessment of the level of intracellular peroxides using the fluorescent probe 2',7'-dichlorofluorescein diacetate (DCFH-DA) confirmed that altholactone induced an increase in cellular oxidative stress in HL-60 cells which was suppressed by N-acetylcysteine. In summary, our results demonstrate for the first time that altholactone induced apoptosis in HL-60 cells occurs via oxidative stress.
Goniothalamin, a plant styrylpyrone derivative isolated from Goniothalamus andersonii, induced apoptosis in Jurkat T-cells as assessed by the externalisation of phosphatidylserine. Immunoblotting showed processing of caspases-3 and -7 with the appearance of their catalytically active large subunits of 17 and 19 kDa, respectively. Activation of these caspases was further evidenced by detection of poly(ADP-ribose) polymerase cleavage (PARP). Pre-treatment with the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethyl ketone (Z-VAD.FMK) blocked apoptosis and the resultant cleavage of these caspases and PARP. Our results demonstrate that activation of at least two effector caspases is a key feature of goniothalamin-induced apoptosis in Jurkat T-cells.