Aptamer-nanoparticle strip biosensor for sensitive detection of cancer cells

Abstract

We report an aptamer-nanoparticle strip biosensor (ANSB) for the rapid, specific, sensitive, and low-cost detection of circulating cancer cells. Known for their high specificity and affinity, aptamers were first selected from live cells by the cell-SELEX (systematic evolution of ligands by exponential enrichment) process. When next combined with the unique optical properties of gold nanoparticles (Au-NPs), ANSBs were prepared on a lateral flow device. Ramos cells were used as a model target cell to demonstrate proof of principle. Under optimal conditions, the ANSB was capable of detecting a minimum of 4000 Ramos cells without instrumentation (visual judgment) and 800 Ramos cells with a portable strip reader within 15 min. Importantly, ANSB has successfully detected Ramos cells in human blood, thus providing a rapid, sensitive, and low-cost quantitative tool for the detection of circulating cancer cells. ANSB therefore shows great promise for in-field and point-of-care cancer diagnosis and therapy.

Fig. 1

Schematic diagram of the detection of Ramos cells on aptamer-nanoparticle strip biosensor (ANSB). (A) Capturing Au-NP-aptamer-Ramos cells on the test zone of ANSB through specific aptamer-cell interactions and (B) Capturing the excess of Au-NP-aptamer on the control zone of ANSB through aptamer-DNA hybridization reaction.

Fig. 2

Typical photo images (top) and corresponding responses (bottom) of ANSB with sample solutions containing 0 Ramos cells (a), 8×10⁴ CCL cells (b), 8×10⁴ Ramos cells (c) and 8×10⁴ CCL cells and 8×10⁴ Ramos cells. The sample solutions were prepared with 0.01 M PBS containing 1% BSA. Volume of the sample solution: 80 μL; Assay time: 15 min.

Fig. 3

(A) The responses of different aptamer pair-based ANSBs; (B) Effect of dispensing cycles of Au-NP-aptamer conjugates on the response of ANSB; (C) Effect of nitrocellulose membranes on the response of ANSB (c); Effect of the buffers used to prepare sample solutions on the response of ANSB. Amount of Ramos cells: 8×10⁴. Volume of the sample solution: 80 μL; Assay time: 15 min.

Fig. 4

(A) The typical responses of ANSB with increasing amounts of Ramos cells. From a to g, the amounts of target cells are 0, 4×10³, 8×10³, 2×10⁴, 4×10⁴, 8×10⁴, 2×10⁵ and (B) the resulting calibration curve. Other conditions are the same as those shown in Figure 2.