Recent progress of TP/NIR fluorescent probes for metal ions

Engineering a far-red fluorescent probe for rapid detection of Hg(II) ions in both cells and zebrafish

Abnormal accumulation of mercury ions (Hg2+) in organisms can lead to severe central nervous system and other diseases. Therefore, the monitoring and detection of Hg2+ are of great significance for human health and environmental safety. Herein, we designed and synthesized a novel far-red to NIR emission fluorescent probe (Rho-Hg) based on rhodamine derivative as the fluorophore and thiospirolactone as the recognition site for turn-on detecting of Hg2+ in living cells and zebrafish. The probe Rho-Hg displayed superior sensitivity (detection limit = 17.5 nM), rapid response (<1 min), colorimetric change, high selectivity, and moderate pH stability. Leveraging this probe, we realized the real-time monitoring of Hg2+ in real samples, living cells and zebrafish. By fostering zebrafish embryos and larvae in Hg2+-containing nutrient solution, we noticed that Hg2+ was ingested into the zebrafish liver when zebrafish were grown up to 3 days old, and thus we successfully monitored the accumulation and changes of Hg2+ during zebrafish growth and development. Thus, the probe Rho-Hg could be a powerful tool for sensitive and real-time monitoring of Hg2+ in living systems.

An excimer process induced a turn-on fluorescent probe for detection of ultra-low concentration of mercury ions

The accumulation of mercury pollution in plants can induce severe injury to human beings. It is a great challenge to monitor ultra-low concentrations of mercury in complicated matrixes. In this study, we successfully developed a strategy via Hg2+-triggered naphthalene-based fluorescent probe 1, which formed excimer that subsequently emitted fluorescence for the successful detection of ultra-low concentrations of Hg2+. The coordination of N and S atoms with Hg2+ facilitated the formation of excimer from the naphthalene-conjugated planes that were in sufficiently close proximity. Suppression of CN bond rotation also induced the chelation-enhanced fluorescence (CHEF) effect, and the cumulative result of these effects was obvious fluorescent enhancement. Compared with probe 2, the other key factor for detection of Hg2+ is that the electrons of the hydroxyl group can easily transfer to a naphthalene moiety, resulting in an augmented π-electron density that enhanced the π-π stacking of the naphthalene-conjugated excimer. After detailed spectral studies and mechanism discussions, it was realized that probe 1 was able to detect ultra-low concentrations of Hg2+ in PBS buffer solution. The detection limit was calculated to be 1.98 nM. On account of the excellent performances, the probe was successfully applied in monitoring Hg2+ in water and pea sprouts with the potential for application as an advanced warning of contamination.

A novel isophorone-based NIR fluorescent and colormetric probe for Al3+ sensing and its application for living cells and plants imaging

In this paper, an isophorone-based NIR fluorescent and colormetric probe BDDH for Al3+ was synthesized and characterized, it showed highly selectivity and sensitivity through significant fluorescence enhancement and visible color change towards Al3+. The job plot confirmed that the binding ratio of BDDH with Al3+ was 1:1. Furthermore, the limit of detection (LOD) of Al3+ was determined to be 4.01 × 10-8 M. Moreover, BDDH was successfully applicated in identification of Al3+ in the different water samples, cell imaging in alive MCF-7 cells and plant imaging in soybean roots.

Refining nanoprobes for monitoring of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a gastrointestinal immune disease that requires clear diagnosis, timely treatment, and lifelong monitoring. The diagnosis and monitoring methods of IBD mainly include endoscopy, imaging examination, and laboratory examination, which are constantly developed to achieve early definite diagnosis and accurate monitoring. In recent years, with the development of nanotechnology, the diagnosis and monitoring methods of IBD have been remarkably enriched. Nanomaterials, characterized by their minuscule dimensions that can be tailored, along with their distinctive optical, magnetic, and biodistribution properties, have emerged as valuable contrast agents for imaging and targeted agents for endoscopy. Through both active and passive targeting mechanisms, nanoparticles accumulate at the site of inflammation, thereby enhancing IBD detection. This review comprehensively outlines the existing IBD detection techniques, expounds upon the utilization of nanoparticles in IBD detection and diagnosis, and offers insights into the future potential of in vitro diagnostics. STATEMENT OF SIGNIFICANCE: Due to their small size and unique physical and chemical properties, nanomaterials are widely used in the biological and medical fields. In the area of oncology and inflammatory disease, an increasing number of nanomaterials are being developed for diagnostics and drug delivery. Here, we focus on inflammatory bowel disease, an autoimmune inflammatory disease that requires early diagnosis and lifelong monitoring. Nanomaterials can be used as contrast agents to visualize areas of inflammation by actively or passively targeting them through the intestinal mucosal epithelium where gaps exist due to inflammation stimulation. In this article, we summarize the utilization of nanoparticles in inflammatory bowel disease detection and diagnosis, and offers insights into the future potential of in vitro diagnostics.

Excellent ratiometric two-photon fluorescent probes for hydrogen sulfide detection based on the fluorescence resonance energy transfer mechanism

Fluorescence resonance energy transfer (FRET) is an important mechanism to design ratiometric fluorescent probes that are able to detect analytes quantitatively according to the ratio of two well-resolved emission signals. Two-photon (TP) fluorescent probes can realize the detection in living cells and tissues with deeper penetration depth, higher resolution, and lower photodamage in contrast to one-photon fluorescent probes. However, to date, fabricating TP-FRET ratiometric fluorescent probes possessing large two-photon absorption (TPA), high fluorescence quantum yield and perfect FRET efficiency is still challenging. Consequently, to develop excellent TP-FRET ratiometric probes and explore the relationship between their molecular structures and TP fluorescence properties, in this paper, we designed a series of H2S-detecting TP fluorescent probes employing the FRET mechanism based on an experimental probe BCD. Thereafter, we comprehensively evaluated the TP sensing performance of these probes by means of time-dependent density functional theory and quadratic response theory. Furthermore, we determined energy transfer efficiency and fluorescence quantum yield. Significantly, through regulating benzene-fused positions, we successfully improved fluorescence quantum yield and TPA cross-section simultaneously. Large spectral overlap between energy donor emission and acceptor absorption was achieved and near perfect energy transfer efficiency was acquired for all the studied probes. We revealed that these probes exhibit two well-resolved TPA bands, which are contributed by FRET donors and acceptors, respectively. Especially, both the wavelengths and the cross-sections of the two TPA bands agree well with those of energy donors and acceptors, which is the unique TPA spectral profile of FRET probes and has never been previously reported. Moreover, we proposed an excellent TP-FRET probe BCD3 and its product molecule BCD3-H2S, which exhibit large Stokes (141 nm and 88 nm) and emission shifts (5931 cm-1), as well as greatly increased TP action cross-sections (24-fold and 60-fold) in the near-infrared region with respect to BCD and BCD-H2S. Our detailed study can give an insight into the efficient design of novel TP-FRET fluorescent probes.