Intracellular Multicomponent Synchronous DNA-Walking Strategy for the Simultaneous Quantification of Tumor-Associated Proteins in a Single Cell

Single-cell protein analysis is very important for understanding cellular heterogeneity and single-cell biology. However, owing to the extremely low levels of some tumor-associated proteins in individual cells, the absolute quantification of such tumor-associated proteins in a single cell remains a challenge. Herein, an intracellular multicomponent synchronous DNA-walking strategy is proposed for the simultaneous quantification of multiple tumor-associated proteins in a single cell. In this strategy, a nanoprobe based on a DNA walker was designed for the simultaneous signal amplification of nucleolin (NCL) and thymidine kinase 1 (TK1) in a single cell. NCL and TK1 in single cells were simultaneously detected on a microchip platform with detection limits of 1.0 and 0.8 pM, respectively. The results obtained from 20 liver cancer cells (HepG2) and 20 normal hepatocytes (HL-7702) indicated that NCL and TK1 were overexpressed in liver cancer cells. However, the levels of NCL and TK1 in normal hepatocytes are only about one-tenth to one-sixth of those in hepatic carcinoma. Using different nucleic acid aptamers, the proposed strategy can be applied for the analysis of other single-cell proteins and in the early diagnosis of cancer.

Automated summary

Single-cell protein analysis is crucial for understanding cellular heterogeneity and biology. This study proposes an intracellular multicomponent synchronous DNA-walking strategy for quantifying multiple tumor-associated proteins simultaneously in a single cell. By amplifying the signals of nucleolin and thymidine kinase 1 using a nanoprobe based on a DNA walker, the absolute quantification of these proteins in single cells was achieved. The results demonstrate the overexpression of nucleolin and thymidine kinase 1 in liver cancer cells compared to normal hepatocytes.