Ultrasmall Magneto-chiral Cobalt Hydroxide Nanoparticles Enable Dynamic Detection of Reactive Oxygen Species in Vivo .

Biological application of chiral nanoparticles (NPs) has aroused enormous levels of attention over recent years. Here, we synthesized magneto-chiral cobalt hydroxide (Co(OH) 2 ) NPs that exhibited strong chiroptical and unique magnetic properties and applied these NPs to detect and monitor reactive oxygen species (ROS) in living cells and in vivo . Circular dichroism (CD) and magnetic resonance imaging (MRI) signals of the magneto-chiral Co(OH) 2 NPs exhibited a wide intracellular ROS detection range from 0.673 to 612.971 pmol/10 6 cells with corresponding limits of detection (LOD) at 0.087 and 0.179 pmol/10 6 cells, far below that of currently available probes; the LOD for d-aspartic acid coated Co(OH) 2 NPs (d-Co(OH) 2 NPs) was 5.7 times lower than that for l-aspartic acid coated Co(OH) 2 NPs (l-Co(OH) 2 NPs) based on the CD signals. In addition, d-Co(OH) 2 NPs also exhibited dynamic ROS monitoring ability. The high levels of selectivity and sensitivity to ROS in complex biological environments can be attributed to the Co 2+ oxidation reaction on the surface of the NPs. Furthermore, magneto-chiral Co(OH) 2 NPs were able to quantify the levels of ROS in living mice by fluorescence and MRI signals. Collectively, these results reveal that magneto-chiral Co(OH) 2 NPs exhibit a remarkable ability to quantify ROS levels in living organisms, and could therefore provide new tools for exploring chiral nanomaterials as a potential biosensor to investigate biological events.