Label-free fluorosensors detect intestinal RNAs that are highly selective and sensitive

In a key advance, researchers at the Nanoscience Centre (NSC) at Zivaskira University, Finland, have published an innovative, unlabeled ratiometric fluorosensor designed for selective and sensitive detection of intestinal RNA. This study promises to provide even more sophisticated and effective detection methods and strengthen the importance of interdisciplinary collaboration in addressing global health challenges.

As evidenced by the recent pandemic, the virus poses a serious threat to global health. Early detection and identification is important to prevent new outbreaks. Traditional detection methods are effective, but in many cases they do not provide spatio-temporal information for viral genome release.

“This interdisciplinary effort, combining biology, chemistry and physics expertise, demonstrates significant advances in virus detection technology. We have enhanced ratiometric fluorosensors using carbon dots (CDS) using probe-functionalized carbon dots (CDS) and ethidium blemides (EB), detection of EB (EB) at Jyväskylä University.

This paper is published in Journal Carbon.

An innovative ratiometric fluorosensor for virus detection

Fluorescent nanoparticles have emerged as a powerful tool for bioanalytical sensing as CDS leads the way due to their simple synthesis, exceptional photostability, tunable photoluminescence, excellent water solubility, biocompatibility, and diverse surface functions of ligand conjugation. These unique properties place the CD as a game changer in the field of biosensing.

“This so-called functionalized sensor (FUNC sensor) is functionalized so that covalent bonding with a probe clearly outweighs the more traditional approach of non-functionalized sensors (non-funk sensors), which are simple mixtures of CDs, probes, and EBs.”

In both sensors, the presence of target DNA hybridized with the probe and enhanced EB fluorescence, but CD fluorescence was slightly altered by electron transfer, allowing ratiometric detection, and was extremely sensitive.

“While non-funk sensors were less sensitive in target DNA and were not effective in actual intestinal RNA samples, the FUNC sensors showed higher sensitivity in DNA and actual viral RNA, clearly improving selectivity.” He previously worked as a postdoctoral researcher at Jibasquila University.

The excellent performance of FUNC sensors is attributed to enhanced charge transfer through shared functioning.

“Our empirical studies of principles highlight the importance of covalent immobilization of probes to improve electron transfer between CDS and EB, demonstrating the compatibility of FUNC sensors for practical applications in rapid, realistic and accurate field detection of viral RNAs, improving performance.

In particular, this study shows that FUNC sensors can detect in vitro in real time in intestinal RNA release from capsids. “This means that FUNC sensors can be used as a new viral RNA sensing platform that offers much needed possibilities to detect the appearance of viral RNA in real time during infection,” says Marjomäki.

Towards safer research

This pioneering work by the research team not only demonstrates new methods for detecting viral RNA, but also sheds light on the charge transfer mechanisms between fluorophores. Based on this success, the researchers are currently working to make the system more robust by replacing the potentially dangerous dye ethidium bromide with a much safer, cytotoxic, biocompatible dye.

“This enhancement further improves the safety and efficacy of in vivo viral RNA detection,” Pathak said.