An amplification-free electrochemical detection of exosomal miRNA-21 in serum samples

Abstract

Recent evidence suggests that small non-coding RNAs such as microRNA (miRNA) encapsulated in exosomes represent an important mechanism of communication between the cells. Exosomal miRNAs play an important role in carcinogenesis via enhancing the cell to cell communication and targeting the cell growth molecular pathways which in turn facilitate metastasis in cancers. Despite progressive advances, the current methods for the exosomal miRNA detection mostly rely on labor-intensive sequencing approaches which are often prone to amplification bias and require costly and bulky equipment. Herein, we report an electrochemical approach for the detection of cancer-derived exosomal miRNAs in human serum samples by selectively isolating the target miRNA using magnetic beads pre-functionalized with capture probes and then directly adsorbing the targets onto a gold electrode surface. The level of adsorbed miRNA is detected electrochemically in the presence of an [Fe(CN)6]4-/3- redox system. This method enabled an excellent detection sensitivity of 1.0 pM with a relative standard deviation (%RSD) of <5.5% in cancer cells and serum samples (n = 8) collected from patients with colorectal adenocarcinoma (CRC). We believe that our approach could be useful in clinical settings for the quantification of exosomal miRNA in cancer patients.

Graphene‐Oxide‐Loaded Superparamagnetic Iron Oxide Nanoparticles for Ultrasensitive Electrocatalytic Detection of MicroRNA

“…The heat‐released target miRNA was isolated by another magnetic separation step (See experimental for details) and directly adsorbed onto the GO/IO‐ modified SPCE using RNA‐ graphene oxide (GO) affinity interaction. We and others previously demonstrated a number of bioassays which rely on nucleic acid‐gold affinity interaction . Similar to the nucleic acid‐gold affinity interaction, direct physisorption of nucleotides (DNA/RNA) on graphene surface has been reported to be influenced by the polarizabilities of the individual nucleobases, where van der Wall (vdW) is considered to be the driving force for the adsorption process ,.…”

CRISPR/Cas13a‐Powered Electrochemical Microfluidic Biosensor for Nucleic Acid Amplification‐Free miRNA Diagnostics

“…Although we are rivaling other Cas13a‐powered optical detection methods for longer RNAs (i.e., SHERLOCK) by a factor of 5 prior to their nucleic acid amplification step, as reported by Li and colleagues, other electrochemical methods for the detection of miRNAs exist, having lower LODs as our presented approach . The basic working principle of most of these electrochemical sensors is the immobilization of a (labeled) nucleic acid sequence, complementary to the target sequence, onto a screen‐printed (gold) electrode, which enables an amplification of the signal, resulting in low LODs.…”

CRISPR/Cas13a powered electrochemical microfluidic biosensor for nucleic acid amplification-free miRNA diagnostics

“…Although we are rivaling other Cas13a powered optical detection methods for longer RNAs (i.e. SHERLOCK) by a factor of five 27 prior to their nucleic acid amplification step, as reported by Li and colleagues 24 , other electrochemical methods for the detection of miRNAs exist, having lower LODs as our presented approach [44][45][46][47][48][49][50][51][52][53][54] . The basic working principle of most of these electrochemical sensors is the immobilization of a (labelled) nucleic acid sequence, complementary to the target sequence, onto a screen-printed (gold) electrode, which enables an amplification of the signal, resulting in low LODs.…”