Synthesis of aspartic acid-derived chiral carbon dots and their effect on bovine serum albumin amyloid fibrillation by multispectral and molecular interaction studies

In this study, two chiral carbon dots (CDs) were synthesized using L/D-aspartic acid as a carbon and chirality source via a rapid microwave-assisted one-step method. The prepared chiral CDs were characterized using various analysis techniques. Transmission electron microscopy images showed that the sizes of L-Asp-CDs and D-Asp-CDs were mainly distributed in the range of 2–4 and 1–3 nm, respectively. In circular dichroism spectra, the peaks at 200–220 nm for L-Asp-CDs and D-Asp-CDs were inherited from L-Asp and D-Asp acid, respectively. In addition, amidation reactions generated new chiral centers. Thioflavin T was used to show that the formation of bovine serum albumin (BSA) amyloid fibril did not involve a nucleation phase, and D-Asp-CDs exhibited a more significant promotion effect on BSA amyloid fibrillation than L-Asp-CDs. Native BSA could form worm-like amyloid fibrils after incubation at 65 °C for 8 h. However, the addition of L-Asp-CDs and D-Asp-CDs led to fibril networks and larger aggregates, respectively. The promotion effect was attributed to the high local concentration due to the absorption on the surface of CDs. The interaction between BSA and L/D-Asp-CDs was further studied, and the quenching mechanism was static quenching. The complex formed between BSA and D-Asp-CDs was more stable than that formed between BSA and L-Asp-CDs, which explains why D-Asp-CDs promoted BSA amyloid fibrillation more significantly than L-Asp-CDs.