mtDNA-Specific Ultrasensitive Near-Infrared Fluorescent Probe Enables the Differentiation of Healthy and Apoptotic Cells

Nanophotonic waveguide-based sensing of circulating cell-free mitochondrial DNA: implications for personalized medicine

Circulating cell-free mitochondrial DNA (ccf-mtDNA) has emerged as a promising biomarker, with potential implications for disease diagnosis. Changes in mtDNA, such as deletions, mutations or variations in the number of copies, have been associated with mitochondrial disorders, heart diseases, cancer and age-related non-communicable diseases. Previous methods, such as polymerase chain reaction-based approaches, next-generation sequencing and imaging-based techniques, have shown improved accuracy in identifying rare mtDNA variants or mutations, but they have limitations. This article explains the basic principles and benefits of using planar optical waveguide-based detection devices, which represent an advanced approach in the field of sensing.

Recent Advances in Organic Small-Molecule Fluorescent Probes Based on Dicyanoisophorone Derivatives

Fluorescent probe technology holds great promise in the fields of environmental monitoring and clinical diagnosis due to its inherent advantages, including easy operation, reliable detection signals, fast analysis speed, and in situ imaging capabilities. In recent years, a wide range of fluorescent probes based on diverse fluorophores have been developed for the analysis and detection of various analytes, yielding significant achievement. Among these fluorophores, the dicyanoisophorone-based fluorophores have garnered significant attention. Dicyanoisoporone exhibits minimal fluorescence, yet possesses a robust electron-withdrawing capability, rendering it suitable for constructing of D-π-A structured fluorophores. Leveraging the intramolecular charge transfer (ICT) effect, such fluorophores exhibit near-infrared (NIR) fluorescence emission with a large Stokes shift, thereby offering remarkable advantages in the design and development of NIR fluorescence probes. This review article primarily focus on small-molecule dicyanoisoporone-based probes from the past two years, elucidating their design strategies, detection performances, and applications. Additionally, we summarize current challenges while predicting future directions to provide valuable references for developing novel and advanced fluorescence probes based on dicyanoisoporone derivatives.

Taming Janus-Faced Quinoline-Derived Fluorescent Probes for Dual-Channel Distinguishable Visualization of HSO3- and HClO in Dried Foods and Living Cells

With the booming development of food manufacturing, developing ideal analytical tools to precisely quantify food additives is highly sought after in the food science field. Herein, a new series of quinoline-derived multifunctional fluorescent probes has been synthesized. Bearing double reactive sites, these compounds display fluorescence response toward both bisulfite (HSO3-) and hypochlorous acid (HClO). Among these compact structures, compound ethyl-2-cyano-3-(6-(methylthio)quinolin-2-yl)acrylate (QTE) was screened out. Probe QTE not only shows ratiometric variation toward HSO3- with little cross talk but also performs turn-off signal toward HClO. In addition, probe QTE has been utilized for bioimaging of HClO in living cells. Furthermore, the HSO3- content in dried food samples has been appraised by QTE with satisfactory results. Meanwhile, relying on the apparent chromaticity change, a flexible dark-box device has been elaborated for chromatic analysis, promoting visualization of HSO3- in the field.

An efficient lipid droplet-targeted fluorescent probe for detection of intracellular viscosity

Lipid droplet, an intracellular lipid reservoir, is vital for energy metabolism and signal transmission in cells. The viscosity directly affects the metabolism of lipid droplets, and the abnormal viscosity is associated with the occurrence and development of various diseases. Therefore, it is indispensable to develop techniques that can detect viscosity changes in intracellular lipid droplets. Based on twisted intramolecular charge transfer (TICT) mechanism, a novel small-molecule lipid droplet-targeted viscosity fluorescence probe PPF-1 was designed. The probe was easy to synthesize, it had a large Stokes shift, stable optical properties, and low bio-toxicity. Compared to being in methanol solution, the fluorescence intensity of PPF-1 in glycerol solution was increased 26.7-fold, and PPF-1 showed excellent ability to target lipid droplets. Thus, the probe PPF-1 could provide an effective means of detecting viscosity changes of lipid droplets and was of great value for physiological diagnosis of related diseases, pathological analysis, and medical research.

Conjugated Oligoelectrolyte with DNA Affinity for Enhanced Nuclear Imaging and Precise DNA Quantification

Precise DNA quantification and nuclear imaging are pivotal for clinical testing, pathological diagnosis, and drug development. The detection and localization of mitochondrial DNA serve as crucial indicators of cellular health. We introduce a novel conjugated oligoelectrolyte (COE) molecule, COE-S3, featuring a planar backbone composed of three benzene rings and terminal side chains. This unique amphiphilic structure endows COE-S3 with exceptional water solubility, a high quantum yield of 0.79, and a significant fluorescence Stokes shift (λex = 366 nm, λem = 476 nm), alongside a specific fluorescence response to DNA. The fluorescence intensity correlates proportionally with DNA concentration. COE-S3 interacts with double-stranded DNA (dsDNA) through an intercalation binding mode, exhibiting a binding constant (K) of 1.32 × 106 M-1. Its amphiphilic nature and strong DNA affinity facilitate its localization within mitochondria in living cells and nuclei in apoptotic cells. Remarkably, within 30 min of COE-S3 staining, cell vitality can be discerned through real-time nuclear fluorescence imaging of apoptotic cells. COE-S3's high DNA selectivity enables quantitative intracellular DNA analysis, providing insights into cell proliferation, differentiation, and growth. Our findings underscore COE-S3, with its strategically designed, shortened planar backbone, as a promising intercalative probe for DNA quantification and nuclear imaging.

Exploring the Role of Mitochondrial Hydrogen Sulfide in Maintaining Polarity and mtDNA Integrity with a Multichannel Fluorescent Probe

Abnormal mitochondrial state has been implicated in the pathogenesis of various diseases including neurodegenerative disorders, myopathies, cardiovascular diseases, and cancers. Assessing mitochondrial functionality can be achieved by monitoring alterations in mitochondrial polarity and mitochondrial DNA (mtDNA) integrity, which serve as valuable biomarkers. Hydrogen sulfide (H2S), a gaseous signaling molecule, plays a regulatory role in mitochondrial respiratory chain activity, ATP synthesis, and calcium ion balance, thereby influencing cellular metabolism and signal transduction. Investigating the interplay between mitochondrial H2S, polarity, and mtDNA can enhance our understanding of the underlying regulatory mechanisms involved in H2S-mediated mitochondrial functions. To address this, we designed a mitochondria-targeted multichannel fluorescent probe, HNA, capable of cascaded detection of H2S and polarity, as well as parallel detection of mtDNA. The probe exhibited a significant turn-on response to H2S, emitting at approximately 604 nm, while the product HNAP demonstrated high sensitivity to polarity within the wavelength range of 526-591 nm. Additionally, the probe was able to bind to DNA, resulting in an enhanced long-wave emission at 668 nm. Facilitated by HNA, our study provides novel insights into the role of mitochondrial H2S in maintaining mitochondrial polarity and validates its protective effect on mtDNA through antioxidative mechanisms. Overall, this work proposes a potential therapeutic strategy for modulating the inflammatory process in mitochondrial-related diseases.

Lighting up RNA-specific multi-photon and super-resolution imaging using a novel zinc complex

Ribonucleic acid (RNA) probes are critical for understanding the role of RNA dynamics in cellular function but are in short supply due to the lack of optimized imaging systems and excellent fluorescence emission performance. Here, the terpyridine Zn(II) complex (Zn-T) with D-π-A configuration and bright aggregation-induced fluorescence emission (AIE) has been fabricated for the selective detection and real-time monitoring of RNA. Impressively, Zn-T exhibits a large Stokes shift and three-photon absorption (3PA) activity and responds specifically through hydrophobic interactions with an RNA pocket. The combination of AIE-assisted two-photon fluorescence and stimulated emission depletion (STED) microscopy of Zn-T for imaging nuclear RNA has higher spatial resolution and brightness, thus providing an imaging platform for studying RNA-related physiological or pathological processes.

Conjugated Aggregation-Induced Fluorescent Materials for Biofluorescent Probes: A Review

The common fluorescent conjugated materials present weak or quenching luminescent phenomena in the solid or aggregate state (ACQ), which limits their applications in medicine and biology. In the last two decades, certain materials, named aggregation-induced emission (AIE) fluorescent materials, have exhibited strong luminescent properties in the aggregate state, which can overcome the ACQ phenomenon. Due to their intrinsic properties, the AIE materials have been successfully used in biolabeling, where they can not only detect the species of ions and their concentrations in organisms, but can also monitor the organisms' physiological activity. In addition, these kinds of materials often present non-biological toxicity. Thus, AIE materials have become some of the most popular biofluorescent probe materials and are attracting more and more attention. This field is still in its early infancy, and several open challenges urgently need to be addressed, such as the materials' biocompatibility, metabolism, and so on. Designing a high-performance AIE material for biofluorescent probes is still challenging. In this review, based on the molecular design concept, various AIE materials with functional groups in the biofluorescent probes are introduced, including tetrastyrene materials, distilbene anthracene materials, triphenylamine materials, and hexaphenylsilole materials. In addition, according to the molecular system design strategy, the donor-acceptor (D-A) system and hydrogen-bonding AIE materials used as biofluorescent probes are reviewed. Finally, the biofluorescent probe design concept and potential evolution trends are discussed. The final goal is to outline a theoretical scaffold for the design of high-performance AIE biofluorescent probes that can at the same time further the development of the applications of AIE-based biofluorescent probes.

A NIR Fluorescent Probe Benzopyrylium Perchlorate-based for Visual Sensing and Imaging of SO2 Derivatives in Living Cells

Endogenous sulfur dioxide (SO₂), as a gas signal molecule, has a certain physiological functions. Understanding the role of endogenous SO₂ in human physiology and pathology is of great significance to the biological characteristics of SO₂,which bring challenges to develop fluorescent probes with excellent performance. Herein, we rationally designed and constructed a novel near-infrared bioprobe benzaldehyde-benzopyrylium (BBp) by employing the nucleophilic addition benzopyrylium perchlorate fluorophore and benzaldehyde moiety by means of C = C/C = O group that serves as both fluorescence reporting unit. Probe BBp exhibit excellent sensing performance with fluorescent "On - Off"rapid response (100 s) and long-wavelength emission (670 nm). With the treatment of HSO₃^-, the color of BBp solution obviously varies from purple to colorless, and the fluorescent color varies from red to colorless. By the fluorescence and colorimetric changes, probe BBp was capable of sensitive determination HSO₃^- with low limits of detection (LOD) of 0.43 μM, realizing visual quantitative monitoring SO₂ derivative levels. Due to the low phototoxicity and good biocompatibility, it was successfully applied to monitor SO₂ derivatives and fluorescence imaging in HepG2 and HeLa living cells. Hopefully, this work supplies a new strategy for designing NIR fluorescent probes for quantitative determination SO₂ derivatives in biological samples.

Synergistically activated dual-locked fluorescent probes to monitor H2S-induced DNA damage

Naphthalimide-based fluorescent probes (NAN0-N3 and NAN6-N3) were developed with dual locked fluorescence. Here, ≥1.9 × 10^-2 mM of H₂S and ≥2.2 × 10^-2 μg mL^-1 of DNA could unlock a highly sensitive off-on fluorescence response through synergistic changes of the molecular structure and conformation. As such, the probes could monitor DNA damage induced by the overexpression of H₂S, and were able to evaluate the degree of apoptosis of living cells mediated by H₂S-induced mtDNA or nDNA damage.

Recent Progress in Fluorescent Probes for Diabetes Visualization and Drug Therapy

Diabetes has become one of the most prevalent endocrine and metabolic diseases that threaten human health, and it is accompanied by serious complications. Therefore, it is vital and pressing to develop novel strategies or tools for prewarning and therapy of diabetes and its complications. Fluorescent probes have been widely applied in the detection of diabetes due to the fact of their attractive advantages. In this report, we comprehensively summarize the recent progress and development of fluorescent probes in detecting the changes in the various biomolecules in diabetes and its complications. We also discuss the design of fluorescent probes for monitoring diabetes in detail. We expect this review will provide new ideas for the development of fluorescent probes suitable for the prewarning and therapy of diabetes in future clinical transformation and application.