Title: DNA-templated silver nanoclusters light up tryptophan for combined detection of plasma tryptophan and albumin in sepsis
Abstract:
Tryptophan (Trp) as an essential amino acid plays critical roles in regulating multiple cell activities, and the changes of its circulating level usually indicate disease status such as the severity of acute inflammation sepsis. However, the current technology for Trp detection mostly relies on chromatography that cannot meet the rapid and simple detection requirement in monitoring sepsis. Herein, a label-free fluorescent nanosensor was constructed to detect Trp and its carrier protein - human serum albumin (HSA) in plasma. The nanosensor consisted of a cytosine (C) - rich signal probe of DNA-templated silver nanoclusters (AgNCs/DNA) and a Trp (Trp) aptamer - based capture probe with a guanine (G) - rich overhang. Trp was found to trigger G-rich sequence-mediated fluorescence enhancement effect for AgNCs/DNA under UV irradiation which offers energy to induce the redox process between limited Trp and silver ions bound on the DNA probes. Based on this photochemical property, the nanosensor exhibited a linear response in the range of 0.05 ~ 60 μM with the limit of detection of 0.43 μM for Trp, superior to the current fluorescence-based detection method, and it gave specific response to indole group. When applied in plasma detection, the nanosensor resisted physiological level of NaCl in plasma, but was quenched by trace volume of HSA, which facilitates the combined HSA detection using only 1 μL plasma sample. The simple procedure of “mix, exposure and detection” together with its ultralow sampling volume, time-saving, cost-effective, sensitive and selective properties endow the nanosensor great potentials for future Trp detection-based clinical use.
Audience Take Away Notes:
- An interesting phenomenon was found that tryptophan (Trp) triggered fluorescence enhancement of DNA-templated silver nanoclusters (AgNCs/DNA) upon UV irradiation.
- Based on the above phenomenon, improved limit of detection for Trp was achieved for fluorescence - based detection.
- The combined detection of Trp and HSA was easily conducted merely by mixing and UV exposure.
- The nanosensor resists physiological level of NaCl in plasma, challenges the previous notion that AgNCs/DNA is easily quenched by NaCl.
- The simple method developed based on AgNCs/DNA enables the rapid combined detection of Trp and HSA, and thus could lay a foundation for sepsis diagnosis in the future, which is characterized by rapid changes in levels of Trp and HSA in plasma.
