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Nanoagent-mediated photothermal therapy (PTT) has been considered as an useful strategy for curing cancer. Nonetheless, identifying high-quality photothermal nanoagents with excellent biocompatibility testing, superior photothermal conversion efficiency (PTCE), and high treatment efficacy, is still a key dilemma for performing practical application in biomedicine field. In our work, a novel photothermal nanoagent named two-dimensional (2D) colloidal rhenium diselenide (ReSe 2) nanosheets was exfoliated via a facile liqiud-assisted exfoliation approach. Owing to surface functionalization with poly-ethylene glycol (PEG), the obtained PEG-ReSe 2 nanosheets demonstrated good solubility and excellent biocompatibility. Notably, the PEG-ReSe 2 nanosheets showed excellent near infrared (NIR) photothermal activity. For the radiation of an NIR laser at 808 nm, an ultrahigh PTCE of 81.3 % was demonstrated. Owing to its high Re element and good photoacoustic effect, the PEG-ReSe 2 nanosheets can serve as good contrast nanoagents for in vivo photoacoustic (PA) imaging. Furthermore, the PEG-ReSe 2 nanosheets acted as excellent photothermal agents (PTAs) for performing PTT. Thanks to high photothermal effects of PEG-ReSe 2 nanosheets, in vitro photothermal effects showed that, the mortality rate of 4T1 cells was almost 100 %. Meanwhile, in vivo experiments showed that mouse tumors were 100 % ablated. More importantly, the PEG-ReSe 2 nanosheets exhibited negligible levels of toxicity, as demonstrated by in vivo cytotoxicity assays and histological analysis. Finally, changes in micro-RNA expression level was proposed to assess PTT treatment efficacy of PEG-ReSe 2 nanoagent. Interestingly, the miRNAs such as miR-125b-5p, miR-20a-5p, miR-214–3p, miR-221–3p, miR-212–3p and miR-27b-3p, were down-regulated. In addiiton, the miRNAs including miR-451a, miR200c-3p, and miR-let-7d-3p, were up-regulated. More importantly, these obtained miRNAs can work as typical indicators for screening PTT outcomes of PEG-ReSe 2 nanosheets-involved PTT. Our research suggested that, the PEG-ReSe 2 nanoagent may represent potential therapeutic nanoagents for in vivo photoacoustic imaging and cancer therapy. [Display omitted] • A novel photothermal nanoagent named PEG-ReSe 2 nanosheets with ultra-high photothermal conversion efficiency was prepared. • PEG-ReSe 2 nanosheets can work as good nanoagents for in vivo photoacoustic imaging and photothermal therapy. • Both down-regulation and up-regulation miRNAs were important biomarkers for screening the therapeutic outcomes of PEG-ReSe 2 nanosheets. [ABSTRACT FROM AUTHOR]

• An excellent bi-color probe named PEG@ReSe 2 nanosheets was prepared. • The nanoprobe exhibited strong two-photon features under a low power excitation. • The nanoprobe showed strong photostability, low cytotoxicity, enabling to perform in vivo bioimaging in cancer cells. Recently two-dimensional (2D) nanomaterials-mediated photothermal therapy (PTT) has become an important tool for treating cancer. However, visually monitoring the localization of nanoagents in cancer cells remains a key challenge. Herein, exploring high photostability, and high biocompatibility probes for monitoring PTT are still highly desirable. In this study, a novel optical probe named PEG@ReSe 2 nanosheets (polyethylene glycol, PEG; rhenium diselenide, ReSe 2) was prepared and employed to perform in vivo two-photon imaging for monitoring PTT in esophageal cancer cells. Under the illumination of a near-infrared (NIR) femtosecond laser at 820 nm with the output power as low as 5 mW, the PEG@ReSe 2 nanosheets showed significant two-photon features, producing a significant photoluminescence emission band at 637 nm. In addition, the prepared PEG@ReSe 2 nanosheets exhibited high resistance to photobleaching. Also, the PEG@ReSe 2 nanosheets showed low cytotoxicity for cancer cells, providing a high viability of more than 90%. More importantly, the PEG@ReSe 2 nanosheets could enter cancer cells and work as a two-photon probe for visually displaying the PTT process. After 12 h incubation, the PEG@ReSe 2 nanosheets produced strong two-photon signals in KYSE150 cancer cells, enabling them to perform in vivo bi-channel bioimaging. In light of its photothermal effects, the PEG@ReSe 2 nanosheets also could serve as a sensor for monitoring PTT under low-power infrared laser irradiation. This study suggests that, the PEG@ReSe 2 nanosheets could serve as a superior two-photon biosensor for monitoring the PTT process in cancer nanomedicine. [ABSTRACT FROM AUTHOR]

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 (ReS 2) nanosheets was firstly reported for performing intracellular bioimaging. Under the illumination of low power NIR femtosecond laser, the prepared ReS 2 nanosheets exhibited strong NIR photon absorption, generating a strong TPL band at 640 nm. In addition, in vitro TPL imaging showed that, ReS 2 nanosheets possessed excellent photostability, enabling to resist photobleaching. More importantly, ReS 2 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-ReS 2 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-ReS 2 nanosheets could work as an excellent TPL probe for monitoring photothermal therapy and evaluating therapeutic outcomes. This study highlights great potential of PEG-ReS 2 nanosheets as a TPL biosensor for intracellular optical imaging and cancer therapy. • A novel TPL nanoprobe named 2D rhenium disulfide (ReS 2) nanosheets was prepared. • The proposed probe showed excellent photostability, enabling to resist photobleaching. • The proposed probe exhibited negligible cytotoxicity, enabling to perform in vivo bioimaging. [ABSTRACT FROM AUTHOR]