DNA micelle-templated copper nanoclusters for fluorescent imaging of MUC1-positive cancer cells.

DNA micelles formed by hydrophobic, self-assembly of amphiphilic DNA monomers have enormous potential in biological imaging owing to its unique and programmable, three-dimensional nanostructure. Herein, we rationally design double-stranded DNA oligonucleotides with two cholesterols that can spontaneously form the lipid-mediated DNA micelles and generate the high fluorescence signal after the formation of DNA-templated copper nanoclusters (CuNCs). Furthermore, the DNA aptamer specific to MUC1 protein, aberrantly overexpressed on the surface of cancer cells, is attached to lipid-mediated DNA micelles to confer the selectivity towards the target cancer cells. With the well-defined DNA nanostructures, the cell membrane of MUC1-positive cancer cells are stained by CuNCs exhibiting an intense, red fluorescence signal, which are clearly distinguished from MUC1-negative cancer cells. This approach may not only expand the application scope of both DNA micells and CuNCs, especially in the area of cellular imaging, but also provides a basis for developing other types of DNA nanostructures to detect target biomarkers.

T7 Endonuclease I-mediated voltammetric detection of KRAS mutation coupled with horseradish peroxidase for signal amplification.

Rapid and selective sensing of KRAS gene mutation which plays a crucial role in the development of colorectal, pancreatic, and lung cancers is of great significance in the early diagnosis of cancers. In the current study, we developed a simple electrochemical biosensor by differential pulse voltammetry technique for the specific detection of KRAS mutation that uses the mismatch-specific cleavage activity of T7-Endonuclease I (T7EI) coupled with horseradish peroxidase (HRP) to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) substrate in the presence of hydrogen peroxide (H2O2). In addition, we synthesized the nanocomposite composed of multi-walled carbon nanotube/chitosan-ionic liquid/gold nanoparticles (MWCNT/Chit-IL/AuNPs) on screen-printed carbon electrode surface to increase the electrode surface area and electrochemical signal. In principle, T7E1 enzyme recognized and cleaved the mismatched site formed by the presence of KRAS gene mutation, removing 5'-biotin of capture probes and subsequently reducing the differential pulse voltammetry signal compared to wild-type KRAS gene. With this proposed strategy, a limit of detection of 11.89 fM was achieved with a broad linear relationship from 100 fM to 1 µM and discriminated 0.1% of mutant genes from the wild-type target genes. This confirms that the developed biosensor is a potential platform for the detection of mutations in early disease diagnosis.