A neoteric dual-signal colorimetric fluorescent probe for detecting endogenous/exogenous hydrogen peroxide in cells and monitoring drug-induced hepatotoxicity

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals. This review focuses specifically on small molecule probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide, and peroxynitrite that provide a luminescent or photoacoustic signal. Important background information on general photophysical phenomena, common probe designs, mechanisms, and imaging modalities will be provided, and then, probes for each analyte will be thoroughly evaluated. A discussion of the successes of the field will be presented, followed by recommendations for improvement and a future outlook of emerging trends. Our objectives are to provide an informative, useful, and thorough field guide to small molecule probes for reactive oxygen and nitrogen species as well as important context to compare the ecosystem of chemistries and molecular scaffolds that has manifested within the field.

A simple mitochondria-immobilized fluorescent probe for the detection of hydrogen peroxide

Hydrogen peroxide (H2O2), as one of reactive oxygen species (ROS) widely present in the human body, is involved in a variety of physiological activities. Many human diseases are associated with abnormal levels of H2O2 in the body. Mitochondria are the main organelles producing H2O2 in the human body, and monitoring the level of H2O2 in mitochondria can help to deepen the understanding of the detailed functions of H2O2 in physiological activities. However, due to the highly dynamic nature of the cells, real-time quantitative monitoring of H2O2 levels in mitochondria remains an ongoing challenge. Herein, a novel highly immobilized mitochondria-targeting fluorescent probe (QHCl) for detection of H2O2 was reasonably constructed based on quinolinium dye containing benzyl chloride moiety. Spectral experimental results demonstrated QHCl possessed outstanding selectivity toward H2O2 (λex/em = 380/513 nm). In addition, QHCl can quantitatively detect H2O2 in the concentration range of 0-20 μM with excellent sensitivity (LOD = 0.58 μM) under the PBS buffer solution (10 mM, pH = 7.4). Finally, bioimaging experiments demonstrated that the probe QHCl was able to be used for accurately detecting both endogenous and exogenous H2O2 in the mitochondria of living cells and zebrafish by its unique mitochondrial immobilization.

A bimodal time-gated luminescence-magnetic resonance imaging nanoprobe based on a europium(III) complex anchored on BSA-coated MnO2 nanosheets for highly selective detection of H2O2

A novel nanocomposite, [Eu(BTD)3(DPBT)]-BSA@MnO2, is reported to serve as an effective nanoprobe for bimodal time-gated luminescence (TGL) and magnetic resonance (MR) imaging of H2O2in vitro and in vivo. The nanoprobe was fabricated by immobilizing visible-light-excitable Eu3+ complexes in bovine serum albumin (BSA)-coated lamellar MnO2 nanosheets. The TGL of the Eu3+ complex was effectively quenched by the MnO2 nanosheets. Upon exposure to H2O2, the MnO2 nanosheets underwent reduction to Mn2+, which simultaneously triggered rapid, selective and sensitive "turn-on" responses toward H2O2 in both TGL and MR detection modes. The presence of a protective "corona" formed by BSA enables the nanoprobe to withstand high concentrations of glutathione (GSH), a strong reducing agent of MnO2 nanosheets. This capability allows the nanoprobe to be utilized for detecting H2O2 in living biosamples. The combined utilization of TGL and MR detection modes enables the nanoprobe to image H2O2 across a wide range of resolutions, from the subcellular level to the whole body, without any depth limitations. The results obtained from these modes can be cross-validated, enhancing the accuracy of the detection. The capability of the nanoprobe was validated by TGL imaging of endogenous and exogenous H2O2 in live HeLa cells, as well as bimodal TGL-MR imaging of H2O2 in tumor-bearing mice. The research achievements suggest that the integration of luminescent lanthanide complexes with protein-coated MnO2 nanosheets offers a promising bimodal TGL-MR sensing platform for H2O2in vitro and in vivo.

Customized fluorescent probe for peering into the expression of butyrylcholinesterase in thyroid cancer

BACKGROUND

Thyroid cancer has been increasingly prevalent in recent years. The main diagnostic methods for thyroid are B-ultrasound scan, serum detection and puncture detection. However, these methods are invasive and complex. It is a pressing need to develop non-invasive or minimally invasive methods for thyroid cancer diagnosis. Fluorescence method as a non-invasive detection method has attracted much attention. Butyrylcholinesterase (BChE) is a common enzyme in the human body, and many diseases affect its reduction. We found that BChE is also a marker for thyroid cancer. Therefore, it is of certain clinical value to explore the expression of BChE in thyroid cancer cells through a customized fluorescent probe to provide valuable experimental data and clues for studying the expression of thyroid cancer marker to reflect thyroid status.

RESULTS

In this study, we customized a fluorescent probe named Kang-BChE, which is easy to synthesize with a high yield. The experimental results show that the probe Kang-BChE can detect BChE in the linear range of 0-900 U L-1 (R2 = 0.9963), and the detection limit is as low as 3.93 U L-1 (λex/em = 550/689 nm). In addition, Kang-BChE probes have low cytotoxicity, good specificity, and can completely eliminate interference from acetylcholinesterase (AChE). Kang-BChE showed excellent stability in the detection of complex biological samples in serum recovery experiments (95.64-103.12 %). This study was the first time using Kang-BChE to study the low expression of BChE in thyroid cancer cells (Tpc-1 cells). In addition, we observed that H2O2 concentration in Tpc-1 cells was positively correlated with BChE activity.

SIGNIFICANCE

Kang-BChE is expected to be an important tool for monitoring the change of BChE content in complex biological environments due to its excellent performance. Kang-BChE can also be used to explore the influence of molecules in more organisms on the change of BChE content due to its excellent anti-interference ability. We expect that Kang-BChE can play a significant role in the clinical diagnosis and treatment of thyroid cancer.

Leucine Aminopeptidase-Mediated Multifunctional Molecular Imaging Tool for Diagnosis, Drug Evaluation, and Surgical Guidance of Liver-Related Diseases

Traditional molecular imaging tools used for detecting liver diseases own several drawbacks, such as poor optical performance and limited applicability. Monitoring the concentration of leucine aminopeptidase (LAP), which is closely related to liver diseases such as liver cancer and liver injury, and analyzing it in diagnosis, drug evaluation, and surgical treatment is still a challenging task. Herein, we construct an intramolecular charge-transfer mechanism-based, ultrasensitive, near-infrared fluorescent probe (LAN-lap) for dynamic monitoring of LAP fluctuations in living systems. LAN-lap, with high specificity, stability, sensitivity, and water solubility, can achieve in vitro monitoring of LAP through both fluorescence and colorimetric methods. Moreover, LAN-lap can successfully be used for the localization imaging of endogenous LAP, confirming the upregulation of LAP expression in liver cancer and liver injury cells. In addition, LAN-lap can realize the imaging of liver tumors in living organisms. Meanwhile, it can intuitively present the degree of drug-induced liver injury, achieving semi-quantitative imaging evaluation of the hepatotoxicity of two drugs. Furthermore, LAN-lap can track liver cancer tumors in mice with peritoneal metastasis and can assist in fluorescence-guided surgical resection of liver cancer tumors. This multifunctional LAN-lap probe could play an important role in facilitating simultaneous diagnoses, imaging, and synergistic surgical navigation to achieve better point-of-care therapeutic efficacy.

Colorimetric and fluorescent dual-signals probes for naked-eye detection of hydrogen peroxide and applications in milk samples and in vivo

Excessive residual hydrogen peroxide (H₂O₂) disinfectant in food is harmful to human health. Therefore, it is necessary to develop efficient detection methods for H₂O₂ detection. In this work, we designed and synthesized five D-A molecules 3a-3e by introducing electron-donor substituents (-OCH₃ and -CH₃) to the electron-acceptor dicyanoisophorone skeleton in order to find out the suitable probes for H₂O₂ detection. Among them, two promising probes, 3a and 3c, are screened out according to structure-property relationships. Based on the principle of intramolecular charge transfer (ICT), 3a and 3c express colorimetric and fluorescent dual-signals towards H₂O₂ with low detection limits (0.20 μM and 0.14 μM) and rapid response (within 20 mins). The reaction mechanism between probes and H₂O₂ is determined by ¹H NMR and HRMS. Density functional theory (DFT) calculations are measured to study the regulation mechanism of structure adjustment on probs performance. Furthermore, a smartphone RGB analysis is utilized as a portable platform for the quantitative detection of H₂O₂ without complicated instruments, indicating a high efficiency and on-site detection method for H₂O₂. In addition, probes are applied to detect H₂O₂ in milk samples, HepG-2 cells and zebrafish, suggesting the promising applications in food samples and physiological systems.

A highly effective "naked eye" colorimetric and fluorimetric curcumin-based fluorescent sensor for specific and sensitive detection of H2O2in vivo and in vitro

Hydrogen peroxide (H₂O₂) is involved in many important tasks in normal cell metabolism and signaling. However, abnormal levels of H₂O₂ are associated with the occurrence of several diseases. Therefore, it is important to develop a new method for the detection of H₂O₂in vivo and in vitro. A turn-off sensor, 2,2-difluoro-4,6-bis(3-methoxy-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)styryl)-2H-1,3,2-dioxaborine (DFCB), based on curcumin was developed for the detection of H₂O₂. The DFCB, an orange-emitting sensor, was constructed by employing 2,2-difluoro-4,6-bis(4-hydroxy-3-methoxystyryl)-2H-1,3,2-dioxaborine (DFC) as the main carrier, and 2-(4-bromomethylphenyl)-4,4,5,5-tetramethyl-1,3,2-doxaborolane as the recognition site. The recognition group on the DFCB sensor could be completely cleaved by H₂O₂ to generate the intermediate DFC, which would lead to a colorimetric change from bright orange to light blue accompanying by a significantly quenched fluorescence, which could be seen by the naked eye. This sensor exhibited a highly specific fluorescence response to H₂O₂, in preference to other relevant species, with an excellent anti-interference performance. The sensor DFCB also possessed some advantages including a wide pH response range (6-11), a broad linear range (0-300 μM), and a low detection limit (1.31 μM). The sensing mechanism of the DFCB sensor for H₂O₂ was verified by HRMS analysis, ¹H-NMR titration and DFT calculations. In addition, the use of the DFCB sensor was compatible with the fluorescence imaging of H₂O₂ in living cells and zebrafish.

Chemosensor with Ultra-High Fluorescence Enhancement for Assisting in Diagnosis and Resection of Ovarian Cancer

Fluorescence imaging-guided diagnostics is one of the most promising approaches for facile detection of tumors in situ owing to its simple operation and non-invasiveness. As a crucial biomarker for primary ovarian cancers, β-galactosidase (β-gal) has been demonstrated to be the significant molecular target for visualization of ovarian tumors. Herein, a membrane-permeable fluorescent chemosensor (namely, LAN-βgal) was synthesized for β-gal-specific detection using the d-galactose residue as a specific recognition unit and LAN-OH (Φ_F = 0.47) as a fluorophore. After β-gal was digested, the fluorescence of the initially quenched LAN-βgal (Φ_F < 0.001) was enhanced by up to more than 2000-fold, which exceeded the fluorescence enhancement of other previously reported probes. We also demonstrated that the chemosensor LAN-βgal could visualize endogenous β-gal and distinguish ovarian cancer cells from normal ovarian cells. Further, the chemosensor LAN-βgal was successfully applied to visualize the back tumor-bearing mouse model and peritoneal metastatic ovarian cancer model in vivo. More importantly, through in situ spraying, the proposed chemosensor was successfully employed to assist in the surgical resection of ovarian cancer tumors due to its high tumor-to-normal (T/N) tissue fluorescence ratio of 218. To the best of our knowledge, this is the highest T/N tissue fluorescence ratio ever reported. We believe that the LAN-βgal chemosensor can be utilized as a new tool for the clinical diagnosis and treatment of ovarian cancer.

Regulating the activity of boronate moiety to construct fluorescent probes for the detection of ONOO-in vitro and in vivo

Abnormal intracellular peroxynitrite (ONOO^-) concentration is related to oxidative damage, which is correlated with many pathological consequences, such as local inflammation and other diseases. In this work, a series of resorufin benzyl ether-based fluorescent probes were designed using boronate as a recognizing moiety installed on a phenyl moiety for ONOO^- detection via a self-immolation mechanism. The location of the boronate as well as the substitution patterns on the phenyl moiety were investigated and the responding behaviors of the designed probes to ONOO^-, other reactive oxygen species, and biothiols were examined. It was found that all the immolative probes were inevitably dominated by ONOO^-. Compared with other probes, p-Borate possessed favorable selectivity and high sensitivity to ONOO^-. Moreover, p-Borate was successfully used to detect ONOO^- in cells and inflamed mice.

Methionine Restriction Improves Cognitive Ability by Alleviating Hippocampal Neuronal Apoptosis through H19 in Middle-Aged Insulin-Resistant Mice

LncRNA H19 has been reported to regulate apoptosis and neurological diseases. Hippocampal neuron apoptosis damages cognitive ability. Methionine restriction (MR) can improve cognitive impairment. However, the effect of MR on hippocampal neuronal apoptosis induced by a high-fat diet (HFD) in middle-aged mice remains unclear. For 25 weeks, middle-aged mice (C57BL/6J) were given a control diet (CON, 0.86% methionine + 4.2% fat), a high-fat diet (HFD, 0.86% methionine + 24% fat), or an HFD + MR diet (HFMR, 0.17% methionine + 24% fat). The HT22 cells were used to establish the early apoptosis model induced by high glucose (HG). In vitro, the results showed that MR significantly improved cell viability, suppressed the generation of ROS, and rescued HT22 cell apoptosis in a gradient-dependent manner. In Vivo, MR inhibited the damage and apoptosis of hippocampal neurons caused by a high-fat diet, reduced hippocampal oxidative stress, improved hippocampal glucose metabolism, relieved insulin resistance, and enhanced cognitive ability. Furthermore, MR could inhibit the overexpression of H19 and caspase-3 induced by HFD, HG, or H2O2 in vivo and in vitro, and promoted let-7a, b, e expression. These results indicate that MR can protect neurons from HFD-, HG-, or H2O2-induced injury and apoptosis by inhibiting H19.

A novel near-infrared fluorescent probe for visualization of intracellular hydrogen peroxide

Hydrogen peroxide (H₂O₂) as a crucial reactive oxygen species (ROS) plays a crucial role in redox signaling in physiological and pathological processes of living cells. Its normal production is closely related to signal transduction of living cells. Overproduction of H₂O₂in vivo has been proved to be related to many diseases. Some were developed to reveal the roles of H₂O₂. However, current fluorescent probes for the detection of H₂O₂ are restricted in their short emission wavelengths and small Stokes shifts that significantly decrease the sensitivity of detection and cellular visualization. In this work, a novel fluorescent probe BC-B was designed and synthesized with pinacol phenylboronic acid ester as a recognition group and near-infrared fluorophore BC-OH as a reporter group. BC-B probe exhibits a large Stokes shift (122 nm) and near-infrared emission (672 nm), showing an excellent selectivity and sensitivity in detection of H₂O₂ with the limit of 0.003 μmol/L. Confocal fluorescence imaging further demonstrates that BC-B can be used for detecting endogenous H₂O₂ in living cells.

Persimmon Tannin-Reduction Graphene Oxide-Platinum-Palladium Nanocomposite Decorated on Screen-Printed Carbon Electrode for Enhanced Electrocatalytic Reduction of Hydrogen Peroxide

According to studies, Hydrogen peroxide (H2O2) is a significant biomarker of physiological processes. Unnormal H2O2 levels in human body may result in diseases. Hence, there is an increasing demand for monitoring the H2O2 concentrations in biological specimen. Here, we construct a non-enzymatic H2O2 electrochemical biosensor based on persimmon tannin-reduced graphene oxide-platinum-palladium nanocomposite (PrG-Pt@Pd NPs) modified with screen-printed carbon electrode (SPE). Combined with suitable electrocatalytic mode for Pt@Pd NPs, high specific large specific volume and good electrical conductivity of RGO, well as the superior sorption capacity of PT for metal-based nano-ion, the PrGPt@Pd striped pleasing heterogeneous catalytic activity toward H2O2 reduction via the synergistic effect. In experimental conditions of optimal, this non-enzymatic electrochemical sensor exhibited excellent electrocatalytic performance for H2O2 with less negative potential (−0.5 V), fast response time (<3 s), it shows good linearity in the range of 5.0–100.0 μM, in addition to this LOD of this sensor was 0.059 μM as well as the excellent sensitivity of the sensor (13.696 μA·μM−1·cm−2). Due to excellent specificity, lower detection limit, and good recovery (98.70–99.96%) in the spiked measurements of human serum samples, this non-enzymatic electrochemical biosensor paves the way for H2O2 detection at ultra-low concentrations in physiology and diagnosis.

Mechanochemical synthesis of an AIE-TICT-ESIPT active orange-emissive chemodosimeter for selective detection of hydrogen peroxide in aqueous media and living cells, and solid-phase quantitation using a smartphone

We report herein the design and mechanochemical synthesis of a chemodosimeter, benzothiazole-derived unsymmetrical azine protected by 4-bromomethylphenylboronic acid (BTPAB), an orange aggregation-induced emission (AIE), for the selective detection of H2O2 in a turn-on manner.