Retaining antigenicity and DNA in the melanin bleaching of melanin-containing tissues

Preserving the antigen effectiveness and DNA when bleaching melanin from melanin-containing tissues is an important part of medical diagnosis. Some prior studies focused excessively on the speed of bleaching neglecting the preservation of antigen and DNA, especially the nucleic acids in the long-archived tissues. The approach of this study was to determine the optimal bleaching conditions by increasing the H₂O₂ concentration and to compare that with the high temperature and potassium-permanganate bleaching methods. The comparisons involve immunohistochemical staining, HE staining, and gel electrophoresis, and setting the blank control (tissues without bleaching). The results demonstrated that bleaching using strong oxidizers or at high temperatures destroyed the antigen and DNA. Incubation with 30% H₂O₂ for 12 h at 24°C leaves only a small amount of melanin, preserving both the antigen effectiveness and the quality of the nucleic acids, and the target bands are clearly visible after PCR amplification. In conclusion, bleaching by increasing the concentration is a simple method, and it satisfies the requirements of clinical pathology and molecular pathology for the diagnosis and differential diagnosis of melanin-containing tissues.