Rhenium disulfide nanosheets as a promising probe for intracellular two-photon luminescence imaging

Near-infrared (NIR) light-mediated two-photon microscopy has become a promising tool for early cancer therapy. However, exploring novel two-photon probe with high biocompatibility and high photostability to resist photobleaching, remains a key challenge for performing in vivo bioimaging. Herein, a novel two-photon luminescence (TPL) probe named two-dimensional rhenium disulfide (ReS2) nanosheets was firstly reported for performing intracellular bioimaging. Under the illumination of low power NIR femtosecond laser, the prepared ReS2 nanosheets exhibited strong NIR photon absorption, generating a strong TPL band at 640 nm. In addition, in vitro TPL imaging showed that, ReS2 nanosheets possessed excellent photostability, enabling to resist photobleaching. More importantly, ReS2 nanosheets functionalized by polyethylene glycol (PEG) showed negligible cytotoxicity, suitable to perform intracellular TPL imaging. With prolonged 6-hour incubation time, the TPL intensity of PEG-ReS2 nanosheets in three kinds of living cells such as esophageal cancer cells (KYSE150), pancreatic cancer cells (4T1) and HeLa cells, were significantly enhanced by almost 4, 11, and 17 times, respectively. In view of their photothermal effects, the PEG-ReS2 nanosheets could work as an excellent TPL probe for monitoring photothermal therapy and evaluating therapeutic outcomes. This study highlights great potential of PEG-ReS2 nanosheets as a TPL biosensor for intracellular optical imaging and cancer therapy.