DNA methylation is a key factor in the pathogenesis of gene expression diseases or malignancies. Thus, it has become a significant biomarker for the diagnosis and prognosis of these diseases. In this paper, we designed an ultrasensitive and specific electrochemical biosensor for DNA methylation detection. The platform consisted of stem−loop−tetrahedron composite DNA probes anchoring at a Au nanoparticle-coated gold electrode, a restriction enzyme digestion of HpaII, and signal amplification procedures including electrodeposition of Au nanoparticles, hybridization chain reaction, and horseradish peroxidase enzymatic catalysis. Under optimal conditions, the design showed a broad dynamic range from 1 aM to 1 pM and a detection limit of about 0.93 aM. The approach also showed ideal specificity, repeatability, and stability. The recovery test demonstrated that the design is a promising platform for DNA methylation detection under clinical circumstances and could meet the need for cancer diagnosis.

Biofilms are defined as aggregation of single cell microorganisms and associated with over 80% of all the microbial infections. Pseudomonas aeruginosa is a Gram‐negative opportunistic pathogen capable of leading to various infections in immunocompromised people. Recent studies showed that norspermidine, a kind of polyamine, prevented and disrupted biofilm formation by some Gram‐negative bacterium. In this study, the effects of norspermidine on P. aeruginosa biofilm formation and eradication were tested. Microtiter plate combined with crystal violet staining was used to study the effects of norspermidine on P. aeruginosa initial attachment, then we employed SEM (scanning electron microscope), qRT‐PCR, and QS‐related virulence factor assays to investigate how norspermidine prevent biofilm formation by P. aeruginosa. We reported that high‐dose norspermidine had bactericide effect on P. aeruginosa, and norspermidine began to inhibit biofilm formation and eradicate 24‐h mature biofilm at concentration of 0.1 and 1 mmol/L, respectively, probably by preventing cell‐surface attachment, inhibiting swimming motility, and downregulating QS‐related genes expression. To investigate the potential utility of norspermidine in preventing device‐related infections, we found that catheters immersed with norspermidine were effective in eradicating mature biofilm. These results suggest that norspermidine could be a potent antibiofilm agent for formulating strategies against P. aeruginosa biofilm.

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