Abstract: Objective To develop a probe for early diagnosis of hepatocellular carcinoma(HCC)by connecting upconversion nanoparticles(UCNPs)with chondroitin sulfate(CS). Methods The UCNPs-CS nanoprobe was constructed using adipic acid hydrazide(ADH)as a bridging agent. First, CS, which exhibits tumor-targeting properties and serves as the targeting moiety of the probe, was functionalized to synthesize CS-ADH under the catalysis of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride(EDC)and N-hydroxysuccinimide(NHS). Subsequently, NaYF4:Yb,Tm@NaYF4 UCNPs with a core-shell structure were prepared via a solvothermal method. The synthesized UCNPs exhibited fluorescence emission bands around 800 nm, making them suitable as fluorescent reporters for in vivo imaging. The UCNPs were rendered water-dispersible through polyacrylic acid(PAA)surface modification and then conjugated with CS-ADH via carboxyl-amine coupling to form the UCNPs-CS nanoprobe. The morphology, optical properties, and chemical composition of the UCNPs were characterized using spectroscopy, nuclear magnetic resonance(NMR), transmission electron microscopy(TEM), and other analytical techniques. The cytotoxicity of the probe was evaluated via MTT assay. To assess the probes in vivo imaging performance and tumor-targeting efficacy, hepatoma-bearing mouse models were established. Furthermore, the activity of different antitumor drugs was evaluated using in vivo imaging. Results The prepared UCNPs with core-shell structures had uniform morphology and size, with a size of about 35 nm and a shell thickness of about 3-4 nm. They had good dispersibility in water. The constructed UCNPs-CS probe had good luminescence performance(excitation wavelength 980 nm, fluorescence emission wavelength 800 nm), cell compatibility(cell survival rate greater than 60% after 24 hours at a concentration of up to 500 μg/mL), strong tissue penetration ability, and could achieve in vivo imaging at the animal level. The imaging results of liver cancer mice showed that the constructed UCNPs-CS probe had good tumor targeting ability, and the imaging radiation intensity was positively correlated with tumor volume. Conclusion The UCNPs-CS probe provides a new tool for early visual diagnosis of HCC, and also provides a new idea for the activity screening of anti-tumor drugs.

Key words: Chondroitin sulfate, Upconversion nanoparticles, Hepatocellular carcinoma, In vivo imaging, Drug activity screening