Detection of miRNA-21 with nano-carbon-based biosensors

Carbon nanomaterials, such as graphene, carbon nanodots, carbon nanotubes, crystalline, and diamond, all exhibit exceptional electrochemical properties, which has led them to be considered for a wide range of different applications. Carbon nanodots (CNDs) in particular have come to the attention of a group of researchers at the Autonomous University of Madrid, Spain, who have used CNDs to test their effectiveness for the detection of miRNA-21, published in review Microchimica Acta.

To study: Carbon nanodot-based electrogenerated chemiluminescence biosensor for miRNA-21 detection. Image Credit: ustas7777777 /

NDT has been the subject of recent active research and used in various applications, including biodetection: “In this context, they have been combined with electrochemiluminescence, leading to a new range of possibilities in the field of biodetection” , explains Dr Tania García Meniola. , co-author and assistant professor at the Autonomous University of Madrid.

Abstract graphic. Image credit: Gutiérrez-Gálvez, L et al., Microchimica Acta

To produce the NDTs, the team applied an environmentally friendly chemical synthesis using tiger’s milk as a natural precursor which demonstrates excellent properties as a co-reactant for the development of a [Ru(bpy)3]DNA 2 + / ECL biosensor. The [Ru(bpy)3]The 2 + / CNDs system was used for the first time to identify the specific sequence of a biomarker associated with breast cancer, miRNA-21. The Madrid team translated this method to try to detect miRNA-21 in serum samples from patients with heart failure.


miRNA-21 belongs to a class of mammalian microRNAs (miRNAs) which are single-stranded molecules approximately 18 to 25 nucleotides in length that regulate gene expression. Deregulated miRNAs have been linked to Alzheimer’s disease, cardiovascular disease, and various cancers, meaning they could be used effectively as biomarkers for early diagnosis.

Notably, miRNA-21 is affiliated with cancer-promoting “oncomiRs”, identified as one of the most frequently upregulated miRNAs in solid tumors. The majority of miRNA-21 targets are tumor suppressors and, therefore, it is associated with a wide variety of cancers, including breast, lung, liver, brain, pancreas and prostate.

Therefore, the use of miRNA-21 as a biomarker and target for cancer treatments could potentially improve outcomes for cancer patients. However, the Madrid-based researchers wanted to develop a biosensor for detecting cardiovascular disease, as increased levels of miRNA-21 are typically found in the fibroblast of the failing heart.

MiRNAs are interesting biomarkers of the response to treatment of cardiovascular disease given their stability, tissue-specific expression patterns, and secretion into body fluids

Dr. Tania García Meniola, co-author and assistant professor, Autonomous University of Madrid

Cardiovascular illnesses

According to the WHO, cardiovascular disease is the leading cause of death worldwide. The majority of cardiovascular diseases can be prevented or managed by modifying behaviors related to smoking, alcohol and eating. It is therefore crucial to identify those at risk as early as possible in order to implement the appropriate therapies and medical treatments.

Therefore, the use of miRNA-21 as a biomarker for cardiovascular disease has gained the attention of the biomedical community, leading to the research and development of various miRNA detection methods such as optical and electrochemical detection methods.

Diagram 1

Environmental chemistry friendly procedure steps for CND synthesis and schematic representation of DNA biosensor development: probe immobilization, hybridization with analyte, and ECL detection using [Ru(bpy)3]2+/ CNDs system. Image credit: Gutiérrez-Gálvez, L et al., Microchimica Acta

However, the existing methods tend to be labor intensive and time consuming, demonstrating the need for a rapid biosensing process for the early diagnosis of cardiovascular disease.

Carbon nanodot sensors

Carbon nanodots belong to a class of carbon nanomaterials smaller than 10 nm in size. First discovered in 2004 during the purification of single-walled carbon nanotubes by preparative electrophoresis.

They have been the cause of much excitement and curiosity in various fields due to their exceptional water solubility, chemical inertness, low toxicity, ease of use and resistance to photobleaching.

The Madrid team were able to synthesize NDT with relative ease using non-toxic solvents and natural products, such as tigernuts milk. In addition, the proposed biosensor for the given application does not require a complex manufacturing procedure.

The resulting method is very sensitive, which facilitates the rapid, direct and simple detection of biomarker traces in the serum of patients with heart failure. The team applied TEM microscopy to characterize the efficiency of NDT-based biosensors and further corroborated the results using FTIR and X-ray photoelectron spectroscopy.

Based on their results, the team then developed an electrochemiluminescent DNA (ECL) biosensor for sensitive detection of miRNA-21. The team then subjected the ECL DNA biosensor to various test methods for the detection of miRNA-21 in spiked human serum samples and samples taken from patients with heart failure.

We can conclude that the developed biosensor can detect miRNA-21 sequence directly in clinical human serum samples from heart failure patients without any prior amplification process.“said García Meniola.

This study paved the way for the development of new environmentally friendly approaches both for the synthesis of CNDs but also for the development of new biosensors for the detection of miRNA-21. In addition, this method of rapid detection could increase the chances of survival of patients with cardiovascular disease.

The references:

Gutiérrez-Gálvez, L., García-Mendiola, T., Gutiérrez-Sánchez, C. et al. Electrogenerated carbon nanodot chemiluminescence biosensor for the detection of miRNA-21. Microchim Acta 188, 398 (2021).

World Health Organization, “Cardiovascular Disease (CVD)”. [, accessed November 2021]

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