Carbon Dots-AS1411 Aptamer Nanoconjugate for Ultrasensitive Spectrofluorometric Detection of Cancer Cells

Philippe Bouvet,Masoud Ayatollahi Mehrgardi,Hasan Motaghi

doi:10.1038/s41598-017-11087-2

Abstract

In the present study, a sensitive and selective signal-on method for aptamer based spectrofluorometric detection of cancer cells is introduced. AS1411, a nucleolin aptamer, is wrapped around water-soluble carbon dots and used as a probe for the detection of several types of cancer cells. Nucleolin, is overexpressed on the surface of cancer cells. Mouse breast 4T1, human breast MCF7, and human cervical HeLa cancer cells were selected as target cells, while human foreskin fibroblast cells HFFF-PI6 served as control cells. For the sensitive and selective spectrofluorimetric detection of target cancer cells in the presence of control cells, the cells were incubated in carbon dots-aptamer solutions, the cell suspensions were subsequently centrifuged and the fluorescence intensities were measured as an analytical signal. The specific targeting of cancer cells by AS1411 aptamers causes the release of carbon dots and enhances the fluorescence intensity. A calibration curve with a dynamic range between 10–4500 4T1 cells and detectability of roughly 7 cells was obtained. In addition, no significant change in the signal was detected by modifying the amount of human foreskin fibroblast control cells. Our results demonstrate similar responses to human MCF7 breast and cervical HeLa cancer cells.

Highlights

AS1411 is a 26-mer oligonucleotide that targets nucleolin[13, 14]
AS1411 binds to nucleolin with high affinity, though this mechanism of interaction is poorly understood. This protein is overexpressed in many types of tumor cells compared to normal cells, and cancer cells display a higher amount of nucleolin on their surface
Mouse breast tumor cells (4T1), human breast tumor cells (MCF7), and human cervical cancer cells (HeLa), all of which overexpress nucleolin on their surface, were incubated in the presence of control human foreskin fibroblast cells (HFFF-PI6) and carbon dots (CDs)-AS1411 aptamer probes to investigated the sensitivity and selectivity of our signal-on spectrofluorometric assay for the targeted detection of cancer cells

Summary

Introduction

AS1411 is a 26-mer oligonucleotide that targets nucleolin[13, 14]. Nucleolin is a multifunctional protein located primarily in the nucleolus, but is found in the cytoplasm and on the membrane of cells[14, 15]. Carbon nanoparticles under 10 nm in size, known as carbon dots (CDs), were used as highly efficient fluorophores[24] They were shown to offer several advantages compared to traditional fluorescent labels such as suitable photostability, favorable biocompatibility, low toxicity, high water solubility, broad excitation spectrum, appropriate quantum yield (QY) and resistance to photobleaching, which makes them interesting candidates for biological experiments[25, 26]. Mouse breast tumor cells (4T1), human breast tumor cells (MCF7), and human cervical cancer cells (HeLa), all of which overexpress nucleolin on their surface, were incubated in the presence of control human foreskin fibroblast cells (HFFF-PI6) and CDs-AS1411 aptamer probes to investigated the sensitivity and selectivity of our signal-on spectrofluorometric assay for the targeted detection of cancer cells

Methods

Results

Conclusion