Screening and application of aptamers as fluorescent biosensors for selective and sensitive detection of hepatocellular carcinoma and in vivo targeted delivery studies

The incidence of primary hepatocellular carcinoma (HCC) has recently ranked fifth in the world, and the incidence rate is increasing year by year worldwide. Therefore, early diagnosis is the highest priority in the treatment of HCC. In this paper, four anti-HCC aptamers were obtained using magnetic bead SELEX technology. Among them, Apt-1 had the smallest K_d value(5.9 nM) and the highest affinity. Flow cytometry results showed that the FITC-aptamers only specifically recognized HCC serum. Circular dichronism (CD) spectral characterization showed a positive peak near 275 nm and a negative peak near 250 nm for all aptamers, elucidating that the secondary structure formed by the candidate aptamers was a stem-loop B-DNA structure. In addition, molecular docking simulations showed that the binding of the HCC target to the candidate aptamer sequences was mainly dominated by hydrogen bonding. The results of the aptamer sensing performance analysis showed that under the optimized assay conditions, a linear relationship (ranging from 1 nM to 1 µM) was achieved, with a limit of detection (LOD) down to 0.75 nM and a LOQ of 2.32 nM. This was further validated in clinical samples, with a positive detection rate of more than 90%. Furthermore, aptamer-mediated in vivo delivery of luciferase mRNA showed that Apt-1-luciferase mRNA could be targeted to the liver and hepatic luciferase expression was significantly increased. These results demonstrate that the aptamer paves the way for clinical application, evidencing  significant potential to offer reference information for early diagnosis.