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A New Detection Protocol for Identifying MicroRNA-122-related Hepatic Inflammation

Researchers at the Hefei Institutes of Physical Science have developed a novel biosensor that may aid in the early diagnosis of hepatic inflammation.

In the treatment of cancers, patients undergo radiotherapy to kill cancer cells and shrink tumours. However, the ionising radiation used may also damage surrounding normal tissues, which could lead to organ failure and internal bleeding. In recent years, microRNAs have been used as biomarkers for analysing tumour progression, drug-triggered inflammation, and radiation injury, among others. As microRNAs are released by cells of damaged organs in cellular vesicles called exosomes, detecting microRNAs is crucial to diagnose radiation injury. Hence, it is important to identify radiation damage at the earliest, but early diagnosis involves detecting low quantities of microRNAs, which remains a challenge.

A team supervised by Professor Huang Qing at the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences designed a novel biosensor based on aptamer-combined surface-enhanced Raman spectroscopy (SERS) to achieve the inflammatory microRNA-122 detection in cell-secreted exosomes.

Exosomes are a rich source of microRNAs and its lipid bilayers protect the microRNAs from degradation, which makes exosomal microRNA a direct biomarker for early diagnosis of disease. The feasibility of current microRNA-detecting methods, like quantitative reverse transcription-polymerase chain reaction (qRT-PCR), is limited due to complex experimental procedures and interference from exosomal surface proteins.

The surface-enhanced Raman spectroscopy (SERS) is a high-sensitivity and versatile technique that has been attracting considerable attention from the scientific community for trace sensing target analytes like nucleic acids, proteins, and some small molecules. However, the application of this approach is limited due to the instability and non-specific adsorption on the SERS tag surface caused by the complicated environment.

To go around this problem, scientists have turned to the use of aptamers, which are short single-stranded DNA sequences with great potential in biological sensing. By combining aptamer-modified SERS tags and a magnetic nanoparticle-based microRNA capturing element, Prof. Huang and colleagues designed a label-free SERS-sandwich assay to identify and evaluate exosomal microRNA-122, which is known to be actively involved in radiation-related rectal and hepatic damage or inflammation.

The SERS tags comprised of a thiolated aptamer, which was modified with additional G bases at the 3’end and functionalised on gold (Au) shell nanoparticles via Au-S bonds. The magnetic capturing element was made by anchoring a thiolated aptamer on magnetic nanoparticles.

To recognise the target microRNAs, the team first exposed the magnetic capturing element to the target, where they captured the microRNA sequence via the immunoreaction between recognition and target sequence. The nanoparticles were then separated using an external magnetic field, rinsed, and probed with SERS tags. This allowed the target sequence to be captured via a sandwich formation and the enhanced Raman signal of adenine base at 3’end of SERS tag was used to calibrate the output signal.

Prof. Huang and colleagues then employed aptamer-combined SERS methodology to detect microRNA as the biomarker for the evaluation of radiation-induced organ damage. These results were further verified by nanodrop UV absorption spectroscopy and qRT-PCR.

The success of their work demonstrates that this aptamer-SERS approach can be valuable in the early diagnosis of hepatic inflammation and may also facilitate the microRNA-related roles and functions in various diseases. [APBN]

Source: Muhammad et al. (2021). Highly Sensitive Detection of Elevated Exosomal miR-122 Levels in Radiation Injury and Hepatic Inflammation Using an Aptamer-Functionalized SERS-Sandwich Assay. ACS Applied Bio Materials.