Multifunctional carbonized polymer dots: Synthesis and applications in retarding protein amyloid aggregation, capturing free radicals and cell imaging

In this study, a series of carbonized polymer dots were synthesized using Congo red and tryptophan as carbon source by changing their molar ratio through simple one-step method in microwave oven. The prepared carbonized polymer dots could emit red fluorescence. All prepared carbonized polymer dots could inhibit the amyloid aggregation of human lysozyme and the CPDs-3 showed the best inhibition capability. The inhibition ratio of the CPDs-3 reached 95.8% at concentration of 40 μg/mL and the IC 50 was 0.41 μg/mL, which may be attributed to the highest content of Congo red on the periphery of the CPDs-3. The CPDs-3 could easily interact with β-sheet structure of human lysozyme through π-π stacking and hydrophobic interaction, which helped to retard the amyloid aggregation. The CPDs-3 also displayed good anti-oxidative property and the highest elimination efficiency for hydroxyl free radical. In addition, the CPDs-3 showed nontoxicity on bEnd.3 cell by CCK-8 assay and could be used in cell imaging.