Boronate carbon nanoparticles featuring efficient FRET for activatable two-photon fluorescence imaging of sialic acid surface-abundant tumor cells.

Two-photon carbon-based nanoprobes hold great potential for biomedical applications as a result of their advantages of low fluorescence background, deep tissue imaging penetration and enhanced spatial resolution. However, the development of an activatable two-photon fluorescence carbon-based nanoprobe that simultaneously has the ability to target desired organs or cells is highly desired but remained a largely unsolved challenge. Herein, we developed boronate affinity BCNP@MnO2 nanocomposites, constructed by one step in situ growth of MnO2 nanosheets on the surface of aminophenylboronic acid-functionalized CNPs (BCNPs) via a redox reaction, which can feature efficient fluorescence energy transfer quenching to the BCNPs, allowing for tumor-specific affinity recognition and two-photon fluorescence activation imaging. By utilizing the inherent two-photon optical properties and sialic acid (SA) specific targeting ability of the BCNPs, good biocompatibility of the nanocomposites as well as highly sensitive and selective responses of MnO2 nanosheets towards GSH, the developed nanocomposites have demonstrated specific two-photon fluorescence activation imaging in target cancer cells and nude mouse tissues. Therefore, our proposed novel strategy could be used for monitoring GSH-triggered two-photon fluorescence activation events in SA-overexpressed cancer cells and has promising applications in both biological exploration and clinical diagnosis.