Development of biotin-tagged near-infrared fluorescence probes for tumor-specific imaging

Near-infrared (NIR) probes are applicable for tumor imaging due to deep tissue penetration and low background signal. And cyanine dyes with long emission wavelength are excellent fluorophores to develop NIR probes. However, the aggregation of cyanine dyes in aqueous solution reduces the utilization of light. To solve this problem, polyethylene glycol (PEG) was introduced into the probes to reduce their aggregation. In our work, two new NIR probes G₁ and G₂ were designed and prepared by conjugating the cyanine dye G₀ with Biotin-PEG5-Azide. The conjugated biotin could enhance the target specificity of probes. And the photophysical and photochemical parameters demonstrated that G₁ and G₂ had a reduced aggregation tendency. In vitro fluorescence imaging proved that these two probes could be specifically taken up by HeLa cells, and in vivo imaging demonstrated that these two probes could specifically target tumors with large tumor-to-muscle (T/M) ratios. All these results indicated that G₁ and G₂ are promising NIR fluorescent contrast agents for tumor-specific imaging.