OICC Press Journal of Nanostructure in Chemistry 2193-8865 14 3 2022 09 20 Protective effect of melanin nanoparticles created from squid ink against irradiation on human keratinocytes 10.1007/s40097-022-00513-1 EN Le Na Nguyen Thi Department of Biochemistry and Molecular Biology, Faculty of Biology, VNU University of Science, Vietnam National University, Hanoi, VN Son Le Duc Department of Biochemistry and Molecular Biology, Faculty of Biology, VNU University of Science, Vietnam National University, Hanoi, VN Van Khanh Bui Thi Department of Biochemistry and Molecular Biology, Faculty of Biology, VNU University of Science, Vietnam National University, Hanoi, VN Thanh Tam Dinh Thi Center of Applied Sciences, Regenerative Medicine and Advance Technologies (CARA)–Vinmec Healthcare System, Hanoi, VN Hai Do Xuan Department of Practical and Experimental Surgery, Vietnam Military Medical University, Hanoi, VN My Nhung Hoang Thi Department of Biochemistry and Molecular Biology, Faculty of Biology, VNU University of Science, Vietnam National University, Hanoi, VN National Key Laboratory of Enzyme and Protein Technology, VNU University of Science, Vietnam National University, Hanoi, VN Thang Nguyen Dinh Department of Biochemistry and Molecular Biology, Faculty of Biology, VNU University of Science, Vietnam National University, Hanoi, VN Journal Article 2022 09 20 Abstract Because the skin is the first organ to be impacted by radiation, keratinocytes (HaCaT cells) are frequently used as an  in vitro model for testing potential radioprotective agents. Melanin extracted from squid ink was considered an antioxidant compound and a possible radioprotector. In this study, nanomelanin was prepared at a size of 100–200 nm from isolated squid melanin. The zeta potential of melanin nanoparticles and the functional groups on their surface were investigated. The antioxidant activity of nanomelanin was examined by the DPPH method. Keratinocyte cells were incubated with or without melanin particles for 24 h before being irradiated in various doses. The radioprotective properties of nanomelanin after 3 days post-radiation were examined by cell survival rates. Treatment with nanomelanin enhances the percentage of cell viability by 10%, depending on the dose of radiation. At 2 days post-radiation, cell groups treated with nanomelanin were reduced to the transcription levels of gene coding BAX, TNF-α, and Caspase 3 for the cellular apoptosis process at various doses (3–5 Gy) of radiotherapy in comparison with control and eliminated the apoptotic cell rate as analyzed by flow cytometry methods. Furthermore, at 3 Gy, melanin nanoparticles promoted the transcription level gene coding SOD1 enzyme by 3.4 folds compared to control. Graphical abstract