Isolation ssDNA aptamers specific for both live and viable but nonculturable state Vibrio vulnificus using whole bacteria-SEILEX technology.

Vibrio vulnificus is a ubiquitous marine bacterium that may cause rapid and deadly infection, threatening lives of people living around natural bodies of water, especially in coastal regions. However, traditional culture-based methods are time-consuming and unable to detect Viable But Non-Culturable (VBNC) V. vulnificus cells. In this work, we isolated a batch of detection aptamers specifically binding to V. vulnificus in all culture status. With traditional whole bacteria-SELEX (Systematic Evolution of Ligands by EXponential enrichment), flow cytometer analysis and imaging, we identify 18 candidates and validated two of them (V8 and V13) as applicable aptamers. Their truncated sequences also showed comparable performance. The dissociation constant (KD) value of V8 is shown to be as low as 11.22 ± 1.32 nM. Optimal aptamers V8 and V13 are also validated to be effective to detect different Vibrio vulnificus strains under different binding environments using flow cytometry. As for detection parameters, the LOD of the V8 from cytometry is 29.96 CFU mL-1, and the linear range is 102-5 × 105 CFU mL-1. This is the first case demonstrating that aptamers can detect the existence of VBNC bacteria as well as live bacteria.

Rapid and sensitive detection of nodularin-R in water by a label-free BLI aptasensor.

Contamination of freshwater with nodularin-R (NOD-R) represents a significant global environmental and public health concern. However, ethical problems and technical difficulties surrounding the current detection methods for NOD-R necessitate further studies to devise appropriate alternatives within a regulatory monitoring regime. In this work, we employed an aptamer as a specific recognition element and developed a biolayer interferometry (BLI) biosensor platform for NOD-R detection. The aptasensor we propose displayed a broad detection range from 40 to 600 nM NOD-R (and a linear response range from 40 to 200 nM), and achieved a detection limit as low as 167 pM. In addition, the aptamer-based biosensor was shown to possess high selectivity, as well as good reproducibility and stability. We believe that this novel aptamer-based biosensor provides a potential alternative for the sensitive and rapid detection of NOD-R.