Studies On The Radioprotection Effect Of Melanin From Spores Of Aspergillus Niger

Objective: In order to study the protective mechanism of melanin with the irradiation of ¹²C⁶⁺ heavy ion beam and X-ray,the effects of melanin on the survival rate of different spores were discussed by ionizing radiation and free radicals.In addition,the difference of the activity of reactive oxygen species,spore membrane permeability and lipid peroxidation among different color spores and the free radical scavenging effect of melanin in free radical environment were also studied.Thus we can prove the protective mechanism of melanin from spores of Aspergillus niger.Materials and Methods: Using the black spores CON,the brown spore MUT and the non-pigmented DM spores,the samples were first irradiated with a gradient dose of ¹²C⁶⁺ heavy ion beam and X-ray,followed by 3% H₂O₂ and 0.5 M DPPH free radicals were used to treat the spores,and the spores were stained with DCFH-DA and PI.The changes of reactive oxygen species in the spores and membrane permeability were measured by fluorescence microscopy.The effect of H₂O₂ on the spore wall was observed by UV spectrophotometer and scanning electron microscopy.Finally,using TBA method to detect the damage degree of lipid peroxidation of spores.The spore pigment was used to detect the scavenging rate of different free radicals in vitro.Results: The dose exposure of ¹²C⁶⁺ heavy ion beam and X-ray to the spore showed that the degree of damage to the spores was positively correlated with the irradiation dose.Under the same irradiation conditions,the black spores?CON?get the slighter damage degree than that of the MUT and the DM spores.The results of three spores were directly treated with 3% H₂O₂ and 0.5M DPPH free radicals showed that the damage degree of spores was positively correlated with the treatment time of free radicals.Under the same free radical treatment conditions,the damage degree of the black CON spores was lower than that of the MUT and the DM spores.Finally,the results showed that melanin could effectively scavenge hydroxyl radical,DPPH and superoxide radical,and the scavenging ability was DPPH>hydroxyl radical>superoxide radical.Conclusion: 1 Melanin in Aspergillus niger can ensure that black spores become a dominant population in the radiation environment,reducing the damage degree of different radiation,and have the ability on radioprotection.2 Aspergillus niger melanin can protect the spores and reduce the damage from different free radicals inthe environment;3 Melanin can effectively scavenge hydroxyl radicals,DPPH and superoxide radicals;4 Aspergillus niger melanin can scavenge free radicals to achieve its radiation protection ability.