To explore the competence of near-infrared luminescent quantum dots for visual in vivo imaging on oral squamous carcinoma BcaCD885 cells. Peptide-conjugated near-infrared quantum dots, with an emission wavelength of 800 nm (QD800), were used to label BcaCD885 cells by endocytosis. The QD800-labeled BcaCD885 cells were inoculated in the dorsum subcutaneous, back muscle and under the cheek oral mucosa of nude mice at cell counts of 1×10³, 1×10⁴, 1×10⁵, and 1×10⁶ respectively. At different time points, these mice were examined by an in vivo imaging system to investigate the sensitivity of QD800 to visual detection in BcaCD885 cells and the conditions of dynamic imaging. The minimum detectable counts of BcaCD885 cells for QD800-based in vivo imaging were 1×10⁴ in the dorsum subcutaneous, back muscle and under the cheek oral mucosa. As tissue depth increased, the detectable fluorescence intensity dropped; as cell counts increased, the fluorescence intensity and the visual image duration also increased, especially for the QD800-labeled BcaCD885 cells in which counts of 1×10⁶ were visual imaged in the dorsum subcutaneous, back muscle and under the cheek oral mucosa for 16 d. Our study successfully used cell-penetrating peptides to conjugate near-infrared quantum dots for the first time and labeled oral squamous carcinoma cells with quantum dot conjugates by endocytosis for visual in vivo imaging. Because of the strong penetration power to tissues, near-infrared quantum dot technology exhibits great promise for the early diagnosis, visual observation and individualized treatment of oral cancer.

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