An innovative study on the "on-off-on" detection of sulfur ions based on a TSPP-riboflavin fluorescent probe

A novel "mix-response" biosensor for colorimetric and photothermal dual-mode detection of sulfide ions in food based on silver-doping Prussian blue nanoparticle

Effective identification of sulfur ions (S2-) in foodstuff is crucial for food safety and human health, but it remains challenging. Traditional single-mode colorimetric sensing methods are simple and sensitive, but are prone to interference from colored substances which can lead to false positives or negatives results. Herein, we develop a novel "mix-response" biosensor for colorimetric and photothermal dual-mode detection of S2- with good simplicity, sensitivity and portability. In this biosensor, silver-doping Prussian blue nanoparticle (SPB NPs) was used as signal output component, which not only exhibits blue color characteristics, but also has photothermal conversion properties activated by near-infrared (NIR) laser. Upon increasing the S2- concentration, the prepared SPB NPs undergo etching, leading to the formation of new silver sulfide precipitation (Ag2S), along with different colorimetric and photothermal response signals. For the portable visualization of S2-, the color information was recorded by a smartphone in combination with RGB (red channel) analysis and the evolution of the photothermal signal was documented by a thermal imager. The introduction of smartphone and handheld thermal imager in this "mix-response" biosensor makes it suitable for on-site quantitative detection of S2- without sophisticated instrument. Moreover, the development of this "mix-response" biosensor does not need the use of recognition probes (e.g. aptamers and reaction intermediates), thereby simplifying the construct procedures of sensing strategies and improving the economic efficiency of detection. More importantly, the photothermal response signals can overcome the interference of colored substances in foods, thereby reducing the false positives or negatives of the detection results.

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

Simultaneous fluorescence sensing of vitamin B2 and sulfur ions based on fluorescent copper nanoparticles

In this study, the F-CuNPs were synthesized by a modified liquid-phase chemical reduction method. Throughout the preparation process, anhydrous copper sulfate was used as the copper source, and ascorbic acid in the NaOH solution served as the reducing and protective agent. Förster resonance energy transfer (FRET) may exist between F-CuNPs and vitamin B2 due to the large spectral overlap between the fluorescence emission spectra of F-CuNPs and the UV-vis absorption spectra of vitamin B2. Therefore, the detection of vitamin B2 was designed based on a FRET system between F-CuNPs and vitamin B2. With S^2- into the F-CuNPs&VB2 system, the fluorescence intensity of vitamin B2 was quenched, while the fluorescence intensity of F-CuNPs was almost unchanged. There may be a specific reaction between S^2- and vitamin B2. Therefore, the research system can be further used to detect S^2- based on ratiometric fluorescent probe. The research findings show that the linear range of vitamin B2 was 0.51 nM-34.64 nM with a detection limit of 0.25 nM (S/N = 3), the linear range of S^2- was 0.64 μM-60.00 μM with a detection limit of 0.32 μM (S/N = 3). Furthermore, the simultaneous fluorescent sensing system has high sensitivity and selectivity. Therefore, this system was designed and successfully used to detect the content of vitamin B2 and S^2- in actual samples to find a new effective method to detect analytes.