A Light‐Up Fluorescent Probe for Detection of Formaldehyde in Serum and Gaseous Based on d ‐PeT Process

Progress in the Study of Optical Probes for the Detection of Formaldehyde

Formaldehyde, one of the simplest reactive carbonyl substances, is involved in many physiological and pathological processes in living organisms. There is a large amount of data showing that abnormal elevation of formaldehyde is associated with a variety of diseases in the body, such as neurodegenerative diseases, Alzheimer's disease, cardiovascular diseases and cancer, and is also a representative carcinogen, so monitoring formaldehyde is of great importance for disease diagnosis and treatment. In this review, In this paper, we summarize and classify the last ten years of probes for the detection of formaldehyde according to different reaction mechanisms and discuss the structures and applications of the probes. Finally, we briefly describe the challenges and possible solutions in this field. We believe that more new probes provide powerful tools to study the function of formaldehyde in living systems.

Evaluation of nitroreductase activity in nasopharyngeal carcinoma progression by an activatable two-photon fluorescent probe

Nasopharyngeal carcinoma (NPC) originating from the epithelium cells is the most common malignant tumor of the head and neck. Small-molecule fluorescent probes for early diagnosis of NPC can effectively improve the 5-year survival rate of patients, which makes it become a research hotspot in recent years. Previous studies have suggested the expression levels of NTR in hypoxic tissues or cells and tumors increased relative to the normal state and were positively correlated with the degree of hypoxia. Regarding the mentioned above, we designed a two-photon fluorescent probe NaT-NTR for the detection of NTR in nasopharyngeal cell lines and tissues at different hypoxia levels. NaT-NTR showed high selectivity and sensitivity toward NTR in a complex physiological environment. Furthermore, imaging NTR in different cell lines revealed that the level of intracellular NTR might be positively correlated with the malignancy of nasopharyngeal carcinoma. More importantly, NaT-NTR was successfully applied to detect and image NTR in human nasopharyngeal carcinoma with a penetration depth of 100 µm. On this basis, NaT-NTR might be a powerful chemical tool for the early diagnosis of nasopharyngeal carcinoma.

Activity-based fluorescent probes for sensing and imaging of Reactive Carbonyl species (RCSs)

This review explains various strategies for developing fluorescent probes to detect reactive carbonyl species (RCS). There are sevaral number of mono and diacarbonyls among 30 varieties of reactive carbonyl species (RCSs) so far discovered, which play pivotal roles in pathological processes such as cancer, neurodegenerative diseases, cardiovascular disease, renal failure, and diabetes mellitus. These RCSs play essential roles in maintaining ion channels regulation, cellular signaling pathways, and metabolisms. Among RCSs, Carbon moxide (CO) is also utilized for its cardioprotective, anti-inflammatory, and anti-apoptotic effects. Fluorescence-based non-invasive optical tools have come out as one of the promising methods for analyzing the concentrations and co-localizations of these small metabolites. There has been a tremendous eruption in developing fluorescent probes for selective detection of specific RCSs within cellular and aqueous environments due to its high sensitivity, high spatial and temporal resolution of fluorescence imaging. Fluorescence-based sensing mechanisms such as intramolecular charge transfer (ICT), photoinduced electron transfer (PeT), excited-state intramolecular proton transfer (ESIPT), and fluorescence resonance energy transfer (FRET) are described. In particular, probes for dicarbonyls such as methylglyoxal (MGO), malondialdehyde (MDA), along with monocarbonyls that include formaldehyde (FA), carbon monoxide (CO) and phosgene are discussed. One of the most exciting advances in this review is the summary of fluorescent probes of dicarbonyl compounds.

Reaction-based fluorescent and chemiluminescent probes for formaldehyde detection and imaging

Formaldehyde (FA), a reactive carbonyl species, is classified as Group 1 carcinogen by International Agency for Research on Cancer (IARC) in 2004. In addition, clinical studies have implicated that elevated levels of FA have been associated with different kinds of diseases, such as neurodegenerative diseases, diabetes, and chronic liver and heart disorders. However, in addition to the direct inhalation of FA in the environment, most organisms can also produce FA endogenously by demethylases and oxidases during the metabolism of amino acids and xenobiotics. Since FA plays an important role in physiological and pathological processes, developing reliable and efficient methods to monitor FA levels in biological samples is crucial. Reaction-based fluorescent/chemiluminescent probes have provided robust methods for FA detection and real-time visualization in living organisms. In this highlight, we will summarize the major developments in the structure design and applications of FA probes in recent years. Three main strategies for designing FA probes have been discussed and grouped by different reaction mechanisms. In addition, some miscellaneous reaction mechanisms have also been discussed. We also highlight novel applications of these probes in biological systems, which offer powerful tools to discover the diverse functions of FA in physiology and pathology processes.

Recent advances in selective formaldehyde detection in biological and environmental samples by fluorometric and colorimetric chemodosimeters

Formaldehyde, a highly reactive carbonyl species, has been widely used in day-to-day life owing to its numerous applications in essential commodities, etc.; the extrusion of formaldehyde from these sources basically leads to increased formaldehyde levels in the environment. Additionally, formaldehyde is endogenously produced in the human body via several biological processes. Considering the adverse effects of formaldehyde, it is highly important to develop an efficient and reliable method for monitoring formaldehyde in environmental and biological samples. Several chemodosimeters (reaction-based sensing probes) have been designed and synthesized to selectively detect the presence of formaldehyde utilizing the photophysical properties of molecules. In this review, we have comprehensively discussed the recent advances in the design principles and sensing mechanisms of developed probes and their biological/environmental applications in selective formaldehyde detection and imaging endogenous formaldehyde in cells. We have summarized the literature based on three different categories: (i) the Schiff base reaction, (ii) the 2-aza-Cope sigmatropic rearrangement reaction and (iii) miscellaneous approaches. In all cases, reactions are accompanied by changes in color and/or emission that can be detected by the naked eye.

TP-FRET-Based Fluorescent Sensor for Ratiometric Detection of Formaldehyde in Real Food Samples, Living Cells, Tissues, and Zebrafish

Formaldehyde (FA, HCHO) is a highly reactive carbonyl species, which is very harmful to humans and the environment as a tissue fixative and preservative. Therefore, developing some highly sensitive, selective, and rapid detection methods is significant for human health in food safety and environmental protection. Herein, a two-photon (TP) ratiometric sensor, CmNp-CHO, has been constructed by conjugating a TP donor (Π-push-pull-structure) with a FA off-on acceptor (functioned with hydrazide moiety) via a nonconjugated linker through the fluorescence resonance energy transfer mechanism. Such a scaffold affords CmNp-CHO a reliable and specific probe for detecting FA with two well-resolved emission peaks separated by 124 nm. Also, it responds to FA rapidly with high selectivity and sensitivity during 1.0 min and a large ratio enhancement at I₅₅₀/I₄₂₆ with addition of 0-20μM FA, exhibiting ∼4-fold ratio increase and a fairly low LOD of 8.3 ± 0.3 nM. Moreover, CmNp-CHO has been successfully employed for detecting FA in live cells, onion tissues, and zebrafish, exhibiting that CmNp-CHO can serve as a useful tool for investigating FA in real food application and offering strong theoretical support and technical means for investigation of physiological and pathological functions of FA.