Neutral Red-carbon nanodots for selective fluorescent DNA sensing.

Carbon nanodots modified with Neutral Red covalently inserted in the nanostructure (NR-CDs) have been prepared by a simple synthesis method based on microwave irradiation under controlled temperature and pressure. The synthetized NR-CDs have been characterized by different techniques, demonstrating the covalent bonding of Neutral Red molecules to the carbon dots nanostructure. Fluorescence activity of the prepare NR-CDs has been explored showing different interaction pathways with singled and doubled stranded DNA. These studies have been successfully applied to develop a new fluorescence DNA hybridization assay to the detection of a specific DNA sequence of Escherichia coli bacteria.

Methylene Blue functionalized carbon nanodots combined with different shape gold nanostructures for sensitive and selective SARS-CoV-2 sensing.

The development of DNA-sensing platforms based on new synthetized Methylene Blue functionalized carbon nanodots combined with different shape gold nanostructures (AuNs), as a new pathway to develop a selective and sensitive methodology for SARS-CoV-2 detection is presented. A mixture of gold nanoparticles and gold nanotriangles have been synthetized to modify disposable electrodes that act as an enhanced nanostructured electrochemical surface for DNA probe immobilization. On the other hand, modified carbon nanodots prepared a la carte to contain Methylene Blue (MB-CDs) are used as electrochemical indicators of the hybridization event. These MB-CDs, due to their structure, are able to interact differently with double and single-stranded DNA molecules. Based on this strategy, target sequences of the SARS-CoV-2 virus have been detected in a straightforward way and rapidly with a detection limit of 2.00 aM. Moreover, this platform allows the detection of the SARS-CoV-2 sequence in the presence of other viruses, and also a single nucleotide polymorphism (SNPs). The developed approach has been tested directly on RNA obtained from nasopharyngeal samples from COVID-19 patients, avoiding any amplification process. The results agree well with those obtained by RT-qPCR or reverse transcription quantitative polymerase chain reaction technique.