Cobalt oxyhydroxide modified with poly-ß-cyclodextrin and a cyanine dye as a nanoplatform for two-photon imaging of ascorbic acid in living cells and tissue.

This article describes the development of several nanoconjugates composed of cobalt (III) oxyhydroxide and DEASPI/ßCDP, where DEASPI stands for the dye trans-4-[p-(N,N-diethylamino)styryl]-N-methylpyridinium, and ßCDP stands for ß-cyclodextrin. The material enables sensitive fluorometric detection and 3D imaging of ascorbic acid (AA) in biological samples. A nanomicelle composed of DEASPI and ßCDP was prepared to act as a two-photon absorbance (TPA) nanofluorophore with desirable two-photon-sensitized fluorescence, high penetration depth, and excellent cell-permeability). The CoOOH nanoflakes were placed on the surface of the nanomicelle to act as both a quencher of fluorescence and as the recognition unit for AA. In the presence of AA, the CoOOH nanoflakes are reduced to Co (II), and this triggers the recovery of fluorescence. This new nanoprobe exhibits amplified two-photon fluorescence (excitation at 840 nm; emission at 565 nm), high sensitivity, and good selectivity. In-vitro imaging of endogenous AA was demonstrated in living HeLa cells. It was also employed to 3D imaging of exogenous AA in tissue by two-photon excitation microscopy to a depth of up to 320 µm. In our perception, this nanoprobe represents a valuable tool for elucidating the roles of AA in biochemical and clinical studies. Graphical abstract Schematic presentation of the preparation of a novel Poly ß-Cyclodextrin/TPdye conjugated with cobalt oxyhydroxide nanoplatform and its application for high sensitive and two-photon 3D imaging of ascorbic acid (AA) in living cells and deep tissues.