Doxorubicin entrapped carbon dots (DOX-CDs) were prepared for bioimaging and enhanced intracellular drug delivery. The CDs were synthesized via the hydrothermal method using citrate and urea under 200 °C for 1 h. Then, DOX was successfully conjugated on the CDs via physicochemical interactions. The DOX-CDs exhibited good crystal structure, remarkable aqueous stability, excellent photoluminescence property, and a high quantum yield of 93%. The fluorescent images revealed that the DOX-CDs could be readily taken up by the cancer cells for cell labeling. Furthermore, endo-lysosomal pH-assisted DOX release behavior was observed from DOX-CDs, and the cytotoxicity of DOX-CDs was confirmed by the MTS assay against H0-8910 ovarian cancer cells. In addition, the CDs indicated bright fluorescent signal in the animal imaging test and demonstrated low toxicity after administration for 7 and 21 days. Therefore, the prepared CDs could be a promising imaging probe for biomedical imaging and intracellular drug delivery.

Background: Early diagnosis of renal cell carcinoma is extremely significant for the effective treatment of kidney cancer. The development of AS1411 aptamer modified Mn-MoS2 QDs provides a promising fluorescence/magnetic resonance (MR) dual-modal imaging probe for the precise diagnosis of renal clear cell carcinoma. Methods: In this work, Mn-MoS₂ QDs were synthesized through a simple “bottom-up” one-step hydrothermal method. AS1411 aptamer was modified on the Mn-MoS₂ QDs to improve the specificity to renal cell carcinoma. The characteristics of Mn-MoS₂ QDs were confirmed by transmission electronic microscopy (TEM), atomic force microscope (AFM), X-ray photoelectron spectrometer (XPS), photoluminescence (PL) emission spectra, etc. Cellular fluorescence labelling was investigated using the Mn-MoS₂ QDs and AS1411-Mn-MoS₂ QDs. The T₁-weighted MR imaging was assessed by the in vitro MR cell imaging and in vivo MR imaging. Finally, the long-term toxicity of Mn-MoS₂ QDs was investigated by the hematology and histological analysis. Results: The prepared Mn-MoS₂ QDs exhibited excellent aqueous property, intense fluorescence, low toxicity, high quantum yield of 41.45% and high T₁ relaxivity of 16.95 mM⁻¹s⁻¹. After conjugated with AS1411 aptamer, the AS1411-Mn-MoS₂ QDs could specifically fluorescently label the renal carcinoma cells and present a specific MRI signal enhancement in the tumor region of mice bearing renal carcinoma tumors. Furthermore, Mn-MoS₂ QDs revealed low toxicity to the mice via hematology and histological analysis. Conclusion: These results demonstrated the potential of AS1411-Mn-MoS₂ QD as a novel nanoprobe for targeted MR imaging and fluorescence labelling of renal cell carcinoma.