A rational design of fluorescent probes for specific detection and imaging of endogenous formaldehyde in living cells

Investigation of the factors influencing the selectivity and response times of glyoxal-selective probes

In this work, four o-phenylenediamine-conjugated fluorescent probes 1-4 with different substituents on the amino group have been designed and prepared to investigate the factors influencing the selectivity and response times of the probes toward glyoxal (GO). The introduced substituted groups, including n-propyl, iso-propyl, tert-butyl, and phenyl, 1-4 displayed sufficient selectivity toward GO. Due to the fact that GO normally exists in a hydrated state in aqueous media, the reaction rates between 1-4 and GO exhibited significant deviation from the steric hindrance effects of most organic reactions. Compounds 3 and 4 with bulky substituted groups presented faster reaction rates with GO than those of compounds 1-2. To further elucidate the properties of these compounds, we selected compound 3 as the representative compound, because of its best selectivity and fast response time, for detailed investigation of the recognition behaviors both in aqueous solution and in living cells. Probe 3 exhibited high selectivity and high sensitivity toward GO with a large Stokes shift (>100 nm), making it highly suitable for in vivo imaging research.

Selectively lighting up glyoxal in living cells using an o-phenylenediamine fused hemicyanine

Glyoxal (GL) is a reactive α-dicarbonyl compound generated from glycated proteins in the Maillard reaction. It has attracted particular attention over the past few years because of its possible clinical significance in chronic and age-related diseases. In this work, a reaction-based red emission fluorescent probe GL1 has been synthesized successfully by grafting an alkyl group onto an amino group to regulate its selectivity for GL. Under physiological conditions, the fluorescence intensity of GL1 at 640 nm obviously increased with the increase of GL concentration, and it exhibited high selectivity for GL over other reactive carbonyl compounds, as well as a lower detection limit (0.021 μM) and a larger Stokes shift (112 nm). At the same time, GL1 can selectively accumulate in mitochondria and can be used to detect exogenous and endogenous GL in living cells with low cytotoxicity.

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.

Synthesis and Characterization of Sulfonamide-Containing Naphthalimides as Fluorescent Probes

A tumor-targeting fluorescent probe has attracted increasing interest in fluorescent imaging for the noninvasive detection of cancers in recent years. Sulfonamide-containing naphthalimide derivatives (SN-2NI, SD-NI) were synthesized by the incorporation of N-butyl-4-ethyldiamino-1,8-naphthalene imide (NI) into sulfonamide (SN) and sulfadiazine (SD) as the tumor-targeting groups, respectively. These derivatives were further characterized by mass spectrometry (MS), nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV), and a fluorescence assay. In vitro properties, including cell cytotoxicity and the cell uptake of tumor cells, were also evaluated. Sulfonamide-containing naphthalimide derivatives possessed low cell cytotoxicity to B16F10 melanoma cells. Moreover, SN-2NI and SD-NI can be taken up highly by B16F10 cells and then achieve good green fluorescent images in B16F10 cells. Therefore, sulfonamide-containing naphthalimide derivatives can be considered to be the potential probes used to target fluorescent imaging in tumors.

The how and why of naphthalimide/heterocycle-fused hybrid dyes: an overview of the latest developments in the quest for dyes with innovative optical properties

In this review, a variety of hybrid structures fusing aromatic heterocycles of different natures to a naphthalimide backbone are discussed. This strategy constitutes an efficient approach to generate original structures displaying singular photophysical properties and thus offering new perspectives in the fields of fluorogenic detection, optoelectronics, and photodynamic therapy. In this review, different synthetic approaches and structures reported in the literature are discussed. A critical look at the design and the applications of these new fused hybrids allows us to evaluate the benefits and drawbacks of a fused hybrid strategy applied to naphthalimides.

A ratiometric fluorescent probe for fast detection and bioimaging of formaldehyde

A novel ratiometric probe (SWJT-10) based on isophorone derivatives has been designed and synthesized for the detection of formaldehyde (FA). This probe displayed an obvious ratiometric fluorescence response to FA with a blue shift from the NIR (680 nm) to the yellow light region (600 nm) in aqueous solution. And it showed good selectivity, high sensitivity and a fast response to FA (less than 5 s) due to a new recognition mechanism. Moreover, SWJT-10 has been applied to monitor FA in living cells and zebrafish.

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.

Systematic investigation of the aza-Cope reaction for fluorescence imaging of formaldehyde in vitro and in vivo

Increasing evidence has highlighted the endogenous production of formaldehyde (FA) in a variety of fundamental biological processes and its involvement in many disease conditions ranging from cancer to neurodegeneration. To examine the physiological and pathological relevance and functions of FA, fluorescent probes for FA imaging in live biological samples are of great significance. Herein we report a systematic investigation of 2-aza-Cope reactions between homoallylamines and FA for identification of a highly efficient 2-aza-Cope reaction moiety and development of fluorescent probes for imaging FA in living systems. By screening a set of N-substituted homoallylamines and comparing them to previously reported homoallylamine structures for reaction with FA, we found that N-p-methoxybenzyl homoallylamine exhibited an optimal 2-aza-Cope reactivity to FA. Theoretical calculations were then performed to demonstrate that the N-substituent on homoallylamine greatly affects the condensation with FA, which is more likely the rate-determining step. Moreover, the newly identified optimal N-p-methoxybenzyl homoallylamine moiety with a self-immolative β-elimination linker was generally utilized to construct a series of fluorescent probes with varying excitation/emission wavelengths for sensitive and selective detection of FA in aqueous solutions and live cells. Among these probes, the near-infrared probe FFP706 has been well demonstrated to enable direct fluorescence visualization of steady-state endogenous FA in live mouse brain tissues and elevated FA levels in a mouse model of breast cancer. This study provides the optimal aza-Cope reaction moiety for FA probe development and new chemical tools for fluorescence imaging and biological investigation of FA in living systems.

One-step construction of a novel AIE probe based on diaminomaleonitrile and its application in double-detection of hypochlorites and formaldehyde gas

A novel and efficient probe with AIE property was designed and synthesized for application in double-detection of hypochlorites and formaldehyde gas.