Fluorescent Probes for the Visualization of Cell Viability

Hydroxyl and phenyl co-modified carbon nitride-based ratiometric fluorescent nanoprobe for monitoring mitochondrial pH in live cells and differentiating cell death

Monitoring mitochondrial pH and differentiating live and dead cells are crucial for diagnosing cell status. However, most fluorescent probes suffer from limitations such as high cytotoxicity, photobleaching, unreliability, and an inability to differentiate cell death caused by different inducers. Herein, a ratiometric fluorescent nanoprobe was developed by assembling pH-sensitive hydroxyl- and phenyl-co-modified carbon nitride (HPCN) with pH-insensitive Rhodamine B (RB). HPCN was prepared via thermal condensation of phenylguanidine carbonate using NaOH as the melt. The hydroxyl group modification endowed HPCN with improved water solubility and pH-sensitive characteristics, while the phenyl group modification facilitated mitochondrial targeting and DNA staining via hydrophobic interactions. Based on the fluorescence resonance energy transfer (FRET) from HPCN to RB, the nanoprobe exhibited a linear response in the relative fluorescence intensities at 500 nm and 584 nm over a pH range of 4.5-8.5. Benefiting from its low cytotoxicity, excellent reversibility, and outstanding photostability, the nanoprobe was capable of monitoring mitochondrial pH changes in live cells and differentiating live and dead cells, apoptosis and necrosis, and necrosis induced by different agents, regardless of cell type. This work provides a reliable method for diagnosing cell status and cell death induced by various inducers.

In situ biosensing for cell viability and drug evaluation in 3D extracellular matrix cultures: Applications in cytoprotection of oxidative stress injury

The rise of extracellular matrix (ECM)-supported three-dimensional (3D) cell culture systems which bridge the gap between in vitro culture and in vivo living tissue for pharmacological models has increased the need for simple and robust cell viability assays. This study presents the development of an effective biosensing assay for in situ monitoring of the catecholamine neurotransmitter exocytosis levels for cell viability assessment within complicated cell-encapsulated hydrogel milieu. Firstly, the biosensing assay demonstrated the distinction among four pheochromocytoma (PC12) cell lines with varying degrees of differentiation and the discrepancy in cellular neurosecretory capacity between two-dimensional (2D) monolayer and 3D agarose hydrogel culture conditions, accompanied by morphological distinctions. Secondly, the electrochemical biosensing assay was performed for viability monitoring of PC12 cell lines following various treatments, including oxidative stress injury (OSI) induced by H2O2 and intervention protected by nimodipine, bone marrow mesenchymal stem cells (BMMSC) supernatant and BMMSC-derived exosomes under 2D and 3D milieus. Of note, BMMSC-derived exosomes exhibited high cytoprotection, anti-oxidation effect, endogenous esterase activity and membrane integrity against OSI. Collectively, the biosensing assay results showed principal but not entire consistency with that of conventional cell-counting kit-8 assay. Therefore, the developed biosensing assay allows for sensitive and in situ cell viability assays in spatial ECM environment, which has broad applications in monitoring physiological and pathological processes.

Microplate-based impedance and thermal sensing system for concurrent cell viability and counting analysis

Cell count and viability are critical parameters in biological research, drug discovery, and bioprocessing. Traditional methods for assessing these metrics often rely on destructive, end-point analyses. This research presents a novel multi-parameter sensing platform that enables concurrent analysis of cell viability and count in a microplate format. The platform combines thermal-based and impedance-based sensing to harness the distinct responses of these methods to variations in cell number and viability. Crucially, both techniques are influenced by cell viability and count, but to different degrees. This difference in sensitivity allows for the exploitation of both methods to independently assess these parameters. Thermal sensing primarily quantifies cell biomass, while impedance measurements are more sensitive to membrane integrity changes associated with cell viability. The integration of these sensing elements into a standard microwell format facilitates real-time and label-free measurements. Experiments with Saccharomyces cerevisiae cultures at various concentrations and viability states demonstrated the platform's capabilities. Multivariate regression models were developed to independently predict cell number and viability, achieving root mean square errors of 0.106 ×107 cells and 19.67% viability respectively. Notably, performance improved at higher cell concentrations, with viability prediction error reduced to 5.02%. This integrated approach shows promise for continuous, non-destructive monitoring of cell cultures, offering a cost-effective alternative to traditional end-point analysis methods. The platform's ability to provide real-time insights into cell population dynamics could significantly enhance various applications in biotechnology, including bioprocess optimization, drug screening, and toxicity testing. Furthermore, its compatibility with standard microplate formats facilitates easy integration into existing laboratory workflows.

Synthesis of naphthalene-fused imidazo[1,2-a]pyridinium salts showing green luminescence with high quantum yields and large Stokes shift

We have synthesized naphthalene-fused imidazo[1,2-a]pyridines by a novel electrophilic iodocyclization of 2-alkynyl-3-arylimidazo[1,2-a]pyridines. Notably, their quaternized salts exhibited green emission with unexpectedly high quantum yields and mega-large Stokes shift and were successfully used for mitochondrial imaging.

Bioactive Molecules of Microalgae Haematococcus pluvialis-Mediated Synthesized Silver Nanoparticles: Antioxidant, Antimicrobial, Antibiofilm, Hemolysis Assay, and Anticancer

Bioactive molecule-based synthesis of silver nanoparticles (AgNPs) offers an eco-friendly approach with high therapeutic potential; however, research in this area remains limited. This study introduces hot melt extrusion (HME) technology to enhance the extraction efficiency of bioactive compounds, including astaxanthin, from the microalgae Haematococcus pluvialis (Hp). AgNPs were synthesized using HME-processed Hp (H-Hp/AgNPs), confirmed by a color change and UV-vis absorption spectrum. The resulting H-Hp/AgNPs exhibited an average size of 129.7 ± 10.4 nm, a polydispersity index of 0.2 ± 0.3, and a zeta potential of -31.54 ± 0.2 mV, indicating high stability. The synthesized AgNPs demonstrated antibacterial activity by inhibiting the growth and biofilm formation of antibiotic-resistant bacteria. Cell viability assays revealed that normal cells maintained over 100% viability at most concentrations of H-Hp/AgNPs, while cancer cells exhibited significant cytotoxicity (34.1 ± 3.1%) at 250 μg/mL. Furthermore, H-Hp/AgNPs induced apoptosis in MDA-MB 231 cells, as evidenced by mitochondrial membrane potential loss, nuclear condensation, and apoptosis, confirmed through AO/EB, Rh123, and PI staining. Additionally, H-Hp/AgNPs showed no hemolytic activity at concentrations below 250 μg/mL, ensuring safety. In conclusion, this study highlights the potential of biosynthesized H-Hp/AgNPs as promising candidates with antioxidant, antibacterial, biocompatibility, and anticancer properties.

Review of advancement in aggregation-induced emission-based fluorescent biosensors for enzyme detection: Mechanisms and biomedical applications

BACKGROUND

Enzymes, primarily proteins produced by living organisms, exhibit high substrate selectivity and catalytic efficiency. Many are crucial for normal biological processes and are closely associated with the onset of various diseases. As such, developing methods for detecting disease-related enzymes is essential. Biosensors based on aggregation-induced emission (AIE) have gained significant attention due to their outstanding properties, including excellent photostability, high luminescence efficiency in the aggregated state, large Stokes shift, and favorable biocompatibility. This has led researchers to design a variety of fluorogens with AIE characteristics (AIEgens).

RESULTS

This review provides an overview of the luminescence mechanism behind AIE and the key properties of AIEgens. It focuses on the physiological roles of disease-related enzymes and outlines various AIE-based fluorescent biosensors developed for enzyme recognition and detection. These biosensors are categorized according to their mechanisms, including hydrolysis, electrostatic adsorption, biological redox reactions, and pH-response. Additionally, this review explores the application of enzymes in disease progression, highlighting their value in inhibitor screening, traditional Chinese medicine research, sensing, bioimaging, and disease diagnosis and therapy. It also discusses the current limitations of AIEgens and explores emerging opportunities for their application.

SIGNIFICANCE AND NOVELTY

Enzyme activity and levels are closely linked to the development of specific diseases, underscoring the importance of advancing methods for enzyme detection in disease diagnosis and treatment. This review provides valuable insights for the development of innovative AIEgens for enzyme detection, expands the options for detection mechanisms, and offers a theoretical foundation for clinical diagnostics and therapeutic applications.

Imaging of Hydrated and Living Cells in Transmission Electron Microscope: Summary, Challenges, and Perspectives

Transmission electron microscopy (TEM) is well-known for performing in situ studies in the nanoscale. Hence, scientists took this opportunity to explore the subtle processes occurring in living organisms. Nevertheless, such observations are complex─they require delicate samples kept in the liquid phase, low electron dose, and proper cell viability verification methods. Despite being highly demanding, so-called "live-cell" experiments have seen some degree of success. The presented review consists of an exhaustive literature review on reported "live-cell" studies and associated subjects, including liquid phase imaging, electron radiation interactions with liquids, and methods for cell viability testing. The challenges of modern, reliable research on living organisms are widely explained and discussed, and future perspectives for developing these techniques are presented.

Molecular probe to visualize the effect of a glycolytic inhibitor on reducing NADH levels in a cellular system

The reduced form of nicotinamide adenine dinucleotide, commonly known as NADH, is an essential coenzyme existing in living organisms. Due to its involvement in various biological process, fluorescence imaging of intracellular NADH levels in different pathological conditions has emerged as an interesting area of research. We report here the exploration of a fluorescent probe, MQ-CN-BTZ, as a dual-channel NADH imaging agent (green and red channels) for cellular systems. Interestingly, depending on the ratio between the probe and NADH concentration in the solution phase, the probe showed emission at ∼529 nm and ∼656 nm when excited at 475 nm. It should be noted that the probe showed a very large Stokes shift of ∼180 nm with respect to the longer-wavelength emission with a good fluorescence response towards NADH. In general, such a large Stokes shift is highly beneficial for imaging applications, largely due to the better separation between the emission and excitation spectra and reduced spectral overlap. Finally, the probe was utilized to image a glycolysis pathway event by employing 3-bromopyruvic acid (3-BrPA) as a glycolytic inhibitor that significantly inhibits the activity of the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is involved in a crucial step of glycolysis. As the depletion of the NADH levels corresponds to the inactivity of GADPH upon treatment with the inhibitor, we attempted to image the modulation of the NADH concentration in the cellular system in the presence of the inhibitor 3-BrPA, indicating the importance of the glycolysis step in elevating NADH levels. Overall, the present study attempts to demonstrate the importance of a molecular probe for fluorescence imaging of intracellular NADH in the presence of a glycolytic inhibitor.

Pinitol Improves Lipopolysaccharide-Induced Cellular Damage in Human Dermal Microvascular Endothelial Cells

3-O-Methyl-D-chiro-inositol (pinitol) has been reported to possess insulin-like effects and is known as one of the anti-diabetic agents for improving muscle and liver function. However, the beneficial effects of pinitol on human dermal microvascular endothelial cells (HDMECs) are not well understood. In this study, we investigated whether pinitol could protect HDMECs from damage induced by lipopolysaccharides (LPSs), which cause various cell defects. We observed that pinitol enhanced wound healing for LPS-damaged HDMECs. We found that pinitol significantly downregulated the LPS-induced upregulation of reactive oxygen species (ROS). Pinitol also significantly restored the mitochondrial membrane potential in these cells. Immunofluorescence analysis revealed that pinitol notably reduced the nuclear localization of NF-κB in LPS-damaged HDMECs. Furthermore, we demonstrated that pinitol decreased the phosphorylation levels of the MAPK family in LPS-damaged HDMECs. Interestingly, we observed that pinitol improved tube formation in LPS-damaged HDMECs. Taken together, we suggest that pinitol exerts several beneficial effects on LPS-damaged HDMECs and may be a promising therapeutic agent for improving vascular-related skin diseases.

An Energy-Tunable Dual Emission Mechanism of the Hybridized Local and Charge Transfer (HLCT) and the Excited State Conjugation Enhancement (ESCE)

Molecular design of dual-fluorescent probes requires precise adjustment of the energy levels of two excited states and the energy barrier between them. While the hybridized local and charge-transfer (HLCT) state has been recently focused as an important excited state for high emission efficiency with a tunable energy level, a dual emission involving the HLCT state has been only achieved with the excited-state intramolecular proton transfer (ESIPT) system. Here, a series of dual-fluorescent molecules involving an HLCT excited state with the excited-state conjugation enhancement (ESCE) motif is presented as the first case. The energy level of the HLCT state has been adjusted by changing substituents and solvents, separately from the ESCE energy level. The HLCT-ESCE molecular design with tunable fluorescence properties proposes a new strategy for the development of advanced fluorescent probes.

Construction of a Cu2+-Responsive NIR Fluorescent Probe and the Preliminary Evaluation of its Multifunctional Application

Cu2+ was deemed as toxic and the most common heavy metal pollution in the water and food. Meanwhile, endogenous Cu2+ was deeply involved in plenty of physiological and pathological processes of human. Cu2+ imbalance was related to multiple diseases. Here we developed a Cu2+-responsive NIR probe HX, which not only demonstrated obvious color change when subjected to Cu2+, but also showed linear-dependent NIR fluorescence emission to Cu2+ concentration for Cu2+ detection and quantification both in vitro and in vivo. When HX was applied to imaging Cu2+ in the cell or living animals, intracellular Cu2+ fluctuation and Cu2+ accumulation in the liver could be visualized to indicate the copper level in the cell or organs with low background signals. Meanwhile, by applying HX to monitor Cu2+ uptake in the tumor, copper transporter function could be evaluated to screen the patient who are sensitivity to platinum drug.

Reactive Oxygen Species (ROS)-Tyrosinase Cascade-Activated Near-Infrared Fluorescent Probe for the Precise Imaging of Melanoma

As a highly aggressive malignancy, the issue of curing melanoma at an advanced stage could suffer from severe metastasis and a lower 5-year survival rate. Therefore, the early diagnosis of melanoma with high accuracy is vital and contributes to a significantly improved 5-year survival rate. This work reports a dual-locked receptor, m-BA-Hcy, which releases the near-infrared (NIR) fluorophore Hcy-OH upon the dual activation of reactive oxygen species (ROS) and tyrosinase (TYR). The substitution of boric acid on the phenyl ring was studied, which influences the feasibility of the performance of the envisaged cascade reaction. The sensing behavior was discussed in terms of optical spectroscopy and reaction mechanism, and imaging was fully performed at the cellular and organism levels. Receptor m-BA-Hcy was hence clarified to possess supreme sensitivity and accuracy for melanoma detection.

Mitochondria-Activated Wash-Free Fluorescent Probe for Visualizing Single-Cell Photodamage

Cell viability assessment is essential in biological and medical research. There is a growing demand for fluorescent probes that can rapidly, reliably, and wash-free evaluate cell viability in complex scenarios. Electron transport chain (ETC) is one of the earliest indicators of cellular distress and holds great potential for assessing cell viability. In this study, we introduce Rhodalive, a mitochondria-targeted ETC-activated fluorescence turn-on probe for single-cell viability assessment. Rhodalive is specifically activated by free electrons leaked from the ETC and localized to the mitochondria, enabling wash-free, spatiotemporal, and super-resolution fluorescence imaging of active mitochondria. Moreover, Rhodalive can effectively distinguish live cells from fixed cells, quantify H2O2-induced cell damage, and visualize single-cell photodamage induced by localized blue light exposure and photodynamic therapy. Rhodalive provides a convenient and reliable tool for dynamically assessing single-cell viability with promising applications in evaluating early mitochondrial dysfunction and advancing drug discovery.

Surface-engineered bio-manufactured gas vesicles for multimodal imaging of glioma

Integrated imaging techniques offer enhanced medical insights into the central nervous system by combining different modalities. In glioma diagnosis, the challenge often lies in delivering contrast agents effectively across the blood-brain barrier. We present an integrated multimodal imaging biohybrid, GV@pCY5, which enables blood-brain barrier penetrating as well as fluorescence and ultrasound (FL/US) imaging capabilities. This biohybrid is created by decorating a far-red-fluorescent cyanine dye (CY5) onto polyethyleneimine (PEI)-coated gas vesicles (GV). The layer-by-layer assembly improves the stability and performance of GV@pCY5 under ultrasound, thanks to the hydration shell variation induced by PEI. Given to the blood-brain barrier penetrating ability, GV@pCY5 demonstrates increase both in fluorescence and ultrasound imaging performance compared to single-component systems, proving effective for glioma diagnosis in vivo. This study underscores the potential of the FL/US platform for dual ratiometric imaging of various cerebral conditions.

Mitochondria/lysosome dual-organelle labelling esterase probe for monitoring cell viability and evaluating lung cancer drug efficiency

Monitoring of cell viability plays a key role in cancer therapy and evaluation of drug efficiency. Mitochondria and lysosomes are involved in regulating cell viability in many biological processes such as apoptosis, necrosis, autophagy, and cell proliferation. Thus, there is an emerging interest in the real-time evaluation of cell viability in both mitochondria and lysosomes. Herein, for the first time, we rationally designed and developed a mitochondria/lysosome dual-organelle labelling esterase-responsive ratiometric fluorescent probe, named TMLE-2, for dual-channel monitoring of cell viability and evaluation of lung cancer drug efficiency. TMLE-2 showed dramatic ratio fluorescence changes (about 51-fold) upon reacting with esterase. Furthermore, TMLE-2 enabled visualization of mitochondria and lysosomes with red and green emission, respectively; moreover, H2O2-induced cell damage, sorafenib-induced ferroptosis and ascorbic-acid-mediated cell protective effects were successfully assessed by dual-organelle ratiometric fluorescent imaging and flow cytometry data. More importantly, TMLE-2 was successfully used for the first time to evaluate the efficiency of lung cancer drugs at the cellular and tissue levels based on dual-organelle esterase activity assay. In summary, the newly designed TMLE-2 is expected to have enormous potential for facilitating advancements in biomedical fields related to cell viability.

Anthracene carboxyimide-based selenide as a fluorescent probe for the ultrasensitive detection of hypochlorous acid

In situ detection of hypochlorous acid (HOCl) is critical for understanding its complex physiological and pathological roles. Fluorescent probes, known for their sensitivity and selectivity, are the preferred approach for such detections. Anthracene carboxyimide, an analog of naphthalimide, offers extended excitation and emission wavelengths, making it an excellent candidate for developing new fluorescent probes that address the limitations of naphthalimide. In this study, we designed a novel HOCl-specific fluorescent probe, AC-Se, by incorporating highly reactive selenium into anthracene carboxyimide. The probe exhibits a 104-fold fluorescence enhancement, a large Stokes shift of 72 nm, and a low detection limit of 36.2 nM. Moreover, AC-Se responds rapidly to HOCl within 4 seconds, enabling real-time intracellular monitoring of both exogenous and endogenous HOCl.

Design, Synthesis, and Cellular Imaging Application of a Fluorescent Probe Based on Fluoride Ion-Induced Cyclization of Phenothiazine Derivatives

Fluoride is both necessary and potentially harmful in excessive amounts, making its detection crucial. Fluorescent probes provide a sensitive and selective means for this purpose. In this study, we developed and synthesized a fluorescent probe for LDT using phenothiazine derivatives and aryl vinyl nitrile. Initially non-fluorescent, the probe undergoes a Si-O bond breakage in the presence of fluoride ions, resulting in the formation of a larger conjugated system and subsequent fluorescence emission. The probe exhibits superior selectivity and sensitivity towards fluoride ions, with a detection limit of 0.35 µM. Moreover, cellular imaging experiments demonstrated the probe's effectiveness in recognizing fluoride ions within HepG2 cells.

Triple C-H Activation/Annulation: In Situ Construction of Fluorescent Peptides

Herein, we report a Rh(III)-catalyzed triple C-H activation-annulation of Phe-based peptides with alkynes for the preparation of fluorescent peptides. The robustness of this protocol is reflected by a broad substrate scope, high atom- and step-economy, and excellent chemo- and site-selectivity. An in situ generated polycyclic aromatic hydrocarbon carbocation as a fluorophore exhibits good fluorescence properties (maximum emission wavelength up to 628 nm) and low cell cytotoxicity. The synthetic utility of this method is further demonstrated by versatile product applications in bioconjugation with the protein BSA and specifically targeting lysosomes and mitochondria of live mammalian cells.

Research Progress of Cyanine-Based Near-Infrared Fluorescent Probes for Biological Application

Cyanine-based near-infrared (NIR) fluorescent probes have played vital roles in biological application due to their low interference from background fluorescence, deep tissue penetration, high sensitivity, and minimal photodamage to biological samples. They are widely utilized in molecular recognition, medical diagnosis, biomolecular detection, and biological imaging. Herein, we provide a review of recent advancements in cyanine-based NIR fluorescent probes for the detection of pH, cells, tumor as well as their application in photothermal therapy (PTT) and photodynamic therapy (PDT).

Permeability-Controlled Probe for Ratiometric Detection of Plasma Membrane Integrity and Late Apoptosis

The destruction of plasma membrane integrity is closely related to immune response, neuronal injury, cell apoptosis, and other pathological events. However, the construction of ratiometric fluorescent probes capable of detecting plasma membrane integrity remains a significant challenge, hindering in-depth studies on related biomedical areas. Herein, a polarity-responsive fluorescent probe was constructed for the ratiometric detection of cell membrane integrity for the first time. The probe targeted intact plasma membranes in healthy cells and relocated into the cytoplasm to give significantly red-shifted fluorescence after plasma membrane damage. Molecular simulations revealed that the high transmembrane barrier and amphipathic nature of the probe were responsible for its targeting ability. With the probe, the ratiometric detection of late apoptosis stage was realized for the first time, and the membrane damage of tumor cells induced by UV irradiation, toxins, and antitumor drugs was visualized. The effect of formaldehyde on membrane integrity was evaluated using a probe, and cysteine was proved to be a potential detoxifier to counteract the toxicity of formaldehyde.

A Novel Benzothiazole-Based Fluorescent AIE Probe for the Detection of Hydrogen Peroxide in Living Cells

A benzothiazole-based derivative aggregation-induced emission (AIE) fluorescent 'turn-on' probe named 2-(2-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)phenyl)benzo[d]thiazole (probe BT-BO) was developed and synthesized successfully for detecting hydrogen peroxide (H2O2) in living cells. The synthesis method of probe BT-BO is facile. Probe BT-BO demonstrates a well-resolved emission peak at 604 nm and the ability to prevent the interference of reactive oxygen species (ROS), various metal ions and anion ions, and good sensitivity. Additionally, the probe boasts impressive pH range versatility, a fast response time to H2O2 and low cytotoxicity. Finally, probe BT-BO was applied successfully to image A549 and Hep G2 cells to monitor both exogenous and endogenous H2O2.

A mitochondria-targeted fluorescent sensor for imaging endogenous peroxynitrite changes in acute lung injury

Acute lung injury (ALI) is a serious pulmonary inflammatory disease resulting from excessive reactive oxygen species (ROS) which could cause the damage of the alveolar epithelial cells and capillary endothelial cells. Peroxynitrite, as one of short-lived reactive oxygen species, is closely related to the process of ALI. Thus, it is important to monitor the fluctuation of peroxynitrite in living system for understanding the process of ALI. Herein, the novel mitochondria-targeted fluorescent probe BHMT was designed to respond to peroxynitrite and pH with distinct fluorescence properties respectively. The absorption spectrum of the probe BHMT exhibited a notable red shift as the pH value declined from 8.8 to 2.6. Upon reaction with peroxynitrite, BHMT had a significant increase of fluorescence intensity (63-fold) with maintaining a detection limit of only 43.7 nM. Furthermore, BHMT could detect the levels of endogenous peroxynitrite and image the intracellular pH in ratiometric channels utilizing cell imaging. In addition, BHMT was successfully applied to revealing the relationship between the peroxynitrite and the extent of ALI. Thus, these results indicated the probe BHMT could be a potential tool for diagnosing the early stage of ALI and revealed the peroxynitrite was likely to be a crucial therapeutic target in ALI treatment.

Deep Learning-Assisted Assessing of Single Circulating Tumor Cell Viability via Cellular Morphology

Circulating tumor cells (CTCs) are closely associated with cancer metastasis and recurrence, so the assessment of CTC viability is crucial for diagnosis, prognosis evaluation, and efficacy judgment of cancer. Due to the extreme scarcity of CTCs in human blood, it is difficult to accurately evaluate the viability of a single CTC. In this study, a deep learning model based on a convolutional neural network was constructed and trained to extract the morphological features of CTCs with different viabilities defined by cell counting kit-8, achieve accurate CTC identification, and assess the viability of a single CTC. Being efficient, accurate, and noninvasive, it has a broad application prospect in biomedical directions.

A novel red fluorescent and dynamic nanocomposite hydrogel based on chitosan and alginate doped with inclusion complex of carbon dots

Red fluorescent hydrogels possessing injectable and self-healing properties have widespread potential in biomedical field. It is still a challenge to achieve a biomacromolecules based dynamic hydrogels simultaneously combining with excellent red fluorescence, good mechanical properties, and biocompatibility. Here we first explore hydrophilic inclusion complex of (R-CDs@α-CD) derived from hydrophobic red fluorescent carbon dots (R-CDs) and α-cyclodextrin (α-CD), and then achieved a red fluorescent and dynamic polysaccharide R-CDs@α-CD/CEC-l-OSA hydrogel. The nanocomposite hydrogel can be fabricated through controlled doping of red fluorescent R-CDs@α-CD into dynamic polymer networks, taking reversibly crosslinked N-carboxyethyl chitosan (CEC) and oxidized sodium alginate (OSA) as an example. The versatile red fluorescent hydrogel simultaneously combines the features of injection, biocompatibility, and augmented mechanical properties and self-healing behavior, especially in rapid self-recovery even after integration. The R-CDs@α-CD uniformly dispersed into dynamic hydrogel played the role of killing two birds with one stone, that is, endowing red emission of a hydrophilic fluorescent substance, and improving mechanical and self-healing properties as a dynamic nano-crosslinker, via forming hydrogen bonds as reversible crosslinkings. The novel red fluorescent and dynamic hydrogel based on polysaccharides is promising for using as biomaterials in biomedical field.

The Influence of the Functional Group on the Physicochemical and Biological Properties of New Phenanthro[9,10-d]-Imidazole Derivatives

The search for safe, cheap, and repeatable diagnostic methods is a fundamental research goal. Currently, great hope is placed on fluorescence imaging. However, the development of this method mainly depends on efficient fluorescent probes. Designing and obtaining new probes with potential applications in fluorescence imaging is very difficult because compounds of this type must meet several requirements related to their properties. Therefore, this article attempted to obtain and study new phenanthro[9,10-d]-imidazole derivatives (PK1-PK3) with potential application as fluorescent probes for fluorescence imaging. The main goal of the work was to assess the effect of two functional groups (such as the formyl group (PK2) and rhodanine-3-acetic acid (PK3)) on selected physicochemical properties and possibilities of practical application of the considered compounds. The conducted studies proved that the influence of the functional group is significant, as it causes a bathochromic shift in both absorption and emission results (by the order PK1 < PK2 < PK3). Moreover, all compounds could stain live cells cultured in vitro. The staining efficiency was not affected by the cell line, thanks to which we obtained the correct staining of both mouse and human cell lines. PK3 was the most attractive of the tested compounds due to its staining potential of live cells and retention after fixation. Our results also showed some antibacterial and antifungal activity of the newly synthesized compounds (PK1-PK3). Among them, PK3 showed the highest antimicrobial effect, especially against Gram-positive bacteria.

A Pyridinium fluorophore for the detection of zinc ions under autophagy conditions

Molecular probes for sensing and imaging of various analytes and biological specimens are of great importance in clinical diagnostics, therapy, and disease management. Since the cellular concentration of free Zn2+ varies from nanomolar to micromolar range during cellular processes and the high affinity Zn2+ imaging probes tend to saturate at lower concentrations of free Zn2+, fluorescence based probes with moderate binding affinity are desirable in distinguishing the occurrence of higher zinc concentrations in the cells. Herein, we report a new, pentacyclic pyridinium based probe, PYD-PA, having a pendant N,N-di(pyridin-2-ylmethyl)amine (DPA) for Zn2+ detection in the cellular environment. The designed probe is soluble in water and serves as a mitochondria targeting unit, whereas the pendent DPA acts as the coordination site for Zn2+. PYD-PA displayed a threefold enhancement in fluorescence intensity upon Zn2+ binding with a 1:1 binding stoichiometry. Further, the probe showed a selective response to Zn2+ over other biologically relevant metal ions with a moderate binding affinity (Ka = 6.29 × 104 M-1), good photostability, pH insensitivity, and low cytotoxicity. The demonstration of bioimaging in SK-BR-3 breast cancer cell lines confirmed the intracellular Zn ion sensing ability of the probe. The probe was successfully applied for real time monitoring of the fluctuation of intracellular free zinc ions during autophagy conditions, demonstrating its potential for cellular imaging of Zn2+ at higher intracellular concentrations.

Advances in small-molecule fluorescent probes for the study of apoptosis

Apoptosis, as type I cell death, is an active death process strictly controlled by multiple genes, and plays a significant role in regulating various activities. Mounting research indicates that the unique modality of cell apoptosis is directly or indirectly related to different diseases including cancer, autoimmune diseases, viral diseases, neurodegenerative diseases, etc. However, the underlying mechanisms of cell apoptosis are complicated and not fully clarified yet, possibly due to the lack of effective chemical tools for the nondestructive and real-time visualization of apoptosis in complex biological systems. In the past 15 years, various small-molecule fluorescent probes (SMFPs) for imaging apoptosis in vitro and in vivo have attracted broad interest in related disease diagnostics and therapeutics. In this review, we aim to highlight the recent developments of SMFPs based on enzyme activity, plasma membranes, reactive oxygen species, reactive sulfur species, microenvironments and others during cell apoptosis. In particular, we generalize the mechanisms commonly used to design SMFPs for studying apoptosis. In addition, we discuss the limitations of reported probes, and emphasize the potential challenges and prospects in the future. We believe that this review will provide a comprehensive summary and challenging direction for the development of SMFPs in apoptosis related fields.

Bioelectroremediation of a Real Industrial Wastewater: The Role of Electroactive Biofilm and Planktonic Cells through Enzymatic Activities

Bioelectrochemical processes are emerging as one of the most efficient and sustainable technologies for wastewater treatment. Their application for industrial wastewater treatment is still low due to the high toxicity and difficulty of biological treatment for industrial effluents. This is especially relevant in pharmaceutical industries, where different solvents, active pharma ingredients (APIs), extreme pH, and salinity usually form a lethal cocktail for the bacterial community in bioreactors. This work evaluates the impact of the anode architecture on the detoxification performance and analyzes, for the first time, the profile of some key bioremediation enzymes (catalase and esterase) and reactive oxygen species (ROS) during the operation of microbial electrochemical cells treating real pharmaceutical wastewater. Our results show the existence of oxidative stress and loss of cell viability in planktonic cells, while the electrogenic bacteria that form the biofilm maintain their biochemical machinery intact, as observed in the bioelectrochemical response. Monitorization of electrical current flowing in the bioelectrochemical system showed how electroactive biofilm, after a short adaptation period, started to degrade the pharma effluent. The electroactive biofilms are responsible for the detoxification of this type of industrial wastewater.

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

Luminescence imaging is a powerful and versatile technique for investigating cell physiology and pathology in living systems, making significant contributions to life science research and clinical diagnosis. In recent years, luminescent transition metal complexes have gained significant attention for diagnostic and therapeutic applications due to their unique photophysical and photochemical properties. In this Review, we provide a comprehensive overview of the recent development of luminescent transition metal complexes for bioimaging and biosensing applications, with a focus on transition metal centers with a d6, d8, and d10 electronic configuration. We elucidate the structure-property relationships of luminescent transition metal complexes, exploring how their structural characteristics can be manipulated to control their biological behavior such as cellular uptake, localization, biocompatibility, pharmacokinetics, and biodistribution. Furthermore, we introduce the various design strategies that leverage the interesting photophysical properties of luminescent transition metal complexes for a wide variety of biological applications, including autofluorescence-free imaging, multimodal imaging, organelle imaging, biological sensing, microenvironment monitoring, bioorthogonal labeling, bacterial imaging, and cell viability assessment. Finally, we provide insights into the challenges and perspectives of luminescent transition metal complexes for bioimaging and biosensing applications, as well as their use in disease diagnosis and treatment evaluation.

A novel NIR fluorescent probe for copper(ii) imaging in Parkinson's disease mouse brain

Abnormal copper ion (Cu2+) levels are considered to be one of the pathological factors of Parkinson's disease (PD), but the internal relationship between Cu2+ and PD progression remains elusive. Visualizing Cu2+ in the brain will be pivotal for comprehending the underlying pathophysiological processes of PD. In this work, a near-infrared (NIR) fluorescent probe, DDAO-Cu, capable of detecting Cu2+ with exceptional sensitivity (about 1.8 nM of detection limit) and selectivity, rapid response (<3 min), and deep tissue penetration, was designed for quantification and visualization of the Cu2+ level. It could detect not only Cu2+ in cells but also the changes in the Cu2+ level in the rotenone-induced cell and zebrafish PD models. Moreover, DDAO-Cu can cross the blood-brain barrier to image Cu2+ in the brain of PD model mice. The imaging result showed a significant increase in Cu2+ levels in brain regions of PD model mice, including the cerebral cortex, hippocampus, and striatum. Meanwhile, Cu2+ levels in the substantia nigra region were significantly reduced in PD model mice. It revealed the nuanced relationship of Cu2+ levels in different brain regions in the disease and indicated the pathological complexity of PD. Overall, DDAO-Cu represents a novel and practical tool for investigating Cu2+-related physiological and pathological processes underlying Parkinson's disease.

A polarity-responsive lysosomes-nucleus translocation probe for the dual-emissive visualization of cell apoptosis

Visualization of cell apoptosis is a critical task playing central roles in the fundamental studies in biology, pathology, and biomedicine. Dual-emissive fluorescent probes are desired molecular tools for study on apoptosis, which however were rarely reported. Herein, utilizing the polarity differences between lysosomes and nucleus, a translocation type of fluorescent probe (NA-S) was developed for the dual-color visualization of cell apoptosis. NA-S was designed to be polarity sensitive, bearing alkalescence group, and with DNA affinity. In living cells, NA-S targeted the lysosomes to give blue fluorescence, which translocated into the nucleus during cell apoptosis to give green emission. Thereby, the cell apoptosis could be visualized with NA-S in dual-emissive manner. With the unique probe, the cell apoptosis induced by oxidative stress, UV irradiation, rotenone, colchicine, and paclitaxel have been successfully visualized.

Fluorescent Probes for Disease Diagnosis

The identification and detection of disease-related biomarkers is essential for early clinical diagnosis, evaluating disease progression, and for the development of therapeutics. Possessing the advantages of high sensitivity and selectivity, fluorescent probes have become effective tools for monitoring disease-related active molecules at the cellular level and in vivo. In this review, we describe current fluorescent probes designed for the detection and quantification of key bioactive molecules associated with common diseases, such as organ damage, inflammation, cancers, cardiovascular diseases, and brain disorders. We emphasize the strategies behind the design of fluorescent probes capable of disease biomarker detection and diagnosis and cover some aspects of combined diagnostic/therapeutic strategies based on regulating disease-related molecules. This review concludes with a discussion of the challenges and outlook for fluorescent probes, highlighting future avenues of research that should enable these probes to achieve accurate detection and identification of disease-related biomarkers for biomedical research and clinical applications.

Hexadecanoic acid produced in the co-culture of S. cerevisiae and E.coli promotes oxidative stress tolerance of the S.cerevisiae cells

Co-fermentation performed by Saccharomyces cerevisiae and Escherichia coli or other microbes has been widely used in industrial fermentation. Meanwhile, the co-cultured microbes might regulate each other's metabolisms or cell behaviors including oxidative stress tolerance through secreting molecules. Here, results based on the co-culture system of S. cerevisiae and E. coli suggested the promoting effect of E. coli on the oxidative stress tolerance of S. cerevisiae cells. The co-cultured E. coli could enhance S. cerevisiae cell viability through improving its membrane stability and reducing the oxidized lipid level. Meanwhile, promoting effect of the co-cultured supernatant on the oxidative stress tolerance of S. cerevisiae illustrated by the supernatant substitution strategy suggested that secreted compounds contained in the co-cultured supernatant contributed to the higher oxidative stress tolerance of S. cerevisiae. The potential key regulatory metabolite (i.e., hexadecanoic acid) with high content difference between co-cultured supernatant and the pure-cultured S. cerevisiae supernatant was discovered by GC-MS-based metabolomics strategy. And exogenous addition of hexadecanoic acid did suggest its contribution to higher oxidative stress tolerance of S. cerevisiae. Results presented here would contribute to the understanding of the microbial interactions and provide the foundation for improving the efficiency of co-fermentation performed by S. cerevisiae and E. coli.

Unique fluorescent probe for the recognition of late apoptosis via translocation from plasma membrane to nucleus

Cell apoptosis is a crucial physiological process playing central roles in key biological and pathological activities. However, the current fluorescent probes for the detection of late apoptosis were "off-on" probes, which were facilely interfered by false positive signals caused by inhomogeneous staining and other factors. Herein, a unique fluorescent probe (NPn) discriminating late apoptosis from early apoptosis and heathy status with two different sets of fluorescent signals have been prepared, to overcome the possible false positive signals. NPn was designed impermeable to biomembranes and simultaneously with high affinity to DNA/RNA, which localized on the plasma membranes of living and early apoptotic cells, while relocated to the nucleus in late apoptotic cells. The hydrophilic amine unit and small ion radius were responsive for its membrane impermeability, which was confirmed with two control molecules without amine group. Using the probe, we have successfully evaluated the cell apoptosis induced by ultraviolet irradiation, rotenone, colchicine, and paclitaxel, demonstrating its potential application in biological researches.

The hepatotoxicity of hexafluoropropylene oxide trimer acid caused by apoptosis via endoplasmic reticulum-mitochondrial crosstalk

As a ubiquitous pollutant in the environment, hexafluoropropylene oxide trimer acid (HFPO-TA) has been proven to have strong hepatotoxicity. However, the underlying mechanism is still unclear. Consequently, in vivo and in vitro models of HFPO-TA exposure were established to investigate the detrimental effects of HFPO-TA on the liver. In vivo, we discovered that HFPO-TA enhanced endoplasmic reticulum (ER)-mitochondrial association, caused mitochondrial oxidative damage, activated ER stress, and induced apoptosis in mouse livers. In vitro experiments confirmed that IP3R overexpression on ER structure increased mitochondrial calcium levels, which led to mitochondrial damage and mitochondria-dependent apoptosis in HepG2 cells exposed to HFPO-TA. Subsequently, damaged mitochondria released a large amount of mitochondrial ROS, which activated ER stress and ER stress-dependent apoptosis. In conclusion, this study demonstrates that HFPO-TA can induce apoptosis by regulating the crosstalk between ER and mitochondria, ultimately leading to liver damage. These findings reveal the significant hepatotoxicity of HFPO-TA and its potential mechanisms.

The Antitumoral Effect In Ovo of a New Inclusion Complex from Dimethoxycurcumin with Magnesium and Beta-Cyclodextrin

Breast cancer is one of the leading causes of death in the female population because of the resistance of cancer cells to many anticancer drugs used. Curcumin has cytotoxic activities against breast cancer cells, although it has limited use due to its poor bioavailability and rapid metabolic elimination. The synthesis of metal complexes of curcumin and curcuminoids is a relevant topic in the search for more active and selective derivatives of these molecular scaffolds. However, solubility and bioavailability are concomitant disadvantages of these types of molecules. To overcome such drawbacks, the preparation of inclusion complexes offers a chemical and pharmacologically safe option for improving the aqueous solubility of organic molecules. Herein, we describe the preparation of the inclusion complex of dimethoxycurcumin magnesium complex (DiMeOC-Mg, (4)) with beta-cyclodextrin (DiMeOC-Mg-BCD, (5)) in the stoichiometric relationship 1:1. This new inclusion complex's solubility in aqueous media phosphate buffer saline (PBS) was improved by a factor of 6x over the free metal complex (4). Furthermore, 5 affects cell metabolic rate, cell morphology, cell migration, induced apoptosis, and downregulation of the matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9), interleukin-6 (IL-6), and signal transducer and activator of transcription-3 (STAT3) expression levels on MD Anderson metastasis breast-231 cancer (MDA-MB-231) cell lines. Results of an antitumor assay in an in ovo model showed up to 30% inhibition of tumor growth for breast cancer (MDA-MB-231) when using (5) (0.650 mg/kg dose) and 17.29% inhibition with the free homoleptic metal complex (1.5 mg/kg dose, (4)). While the formulation of inclusion complexes from metal complexes of curcuminoids demonstrates its usefulness in improving the solubility and bioavailability of these metallodrugs, the new compound (5) exhibits excellent potential for use as a therapeutic agent in the battle against breast cancer.

Treatment evaluation of Rheumatoid arthritis by in situ fluorescence imaging of the Golgi cysteine

Rheumatoid arthritis (RA) is a long-term systemic inflammatory disease that causes severe joint pain. Golgi stress caused by redox imbalance significantly involves in acute and chronic inflammatory diseases, in which cysteine (Cys), as a representative reducing agent, may be an effective biomarker for RA. Hence, in order to achieve RA early detection and drugs evaluation, based on our previous work about innovative Golgi-targeting group, we established a phenylsulfonamide-modified fluorescence probe, Golgi-Cys, for the selective fluorescence imaging of Cys in Golgi apparatus in vivo. By application of Golgi-Cys, the Cys changes under Golgi stress in cells were elucidated. More importantly, we found that the probe can be effectively utilized for the RA detection and treatment evaluation in situ.

Cell viability and cytotoxicity assays: Biochemical elements and cellular compartments

Cell viability and cytotoxicity assays play a crucial role in drug screening and evaluating the cytotoxic effects of various chemicals. The quantification of cell viability and proliferation serves as the cornerstone for numerous in vitro assays that assess cellular responses to external factors. In the last decade, several studies have developed guidelines for defining and interpreting cell viability and cytotoxicity based on morphological, biochemical, and functional perspectives. As this domain continues to experience ongoing growth, revealing new mechanisms orchestrating diverse cell cytotoxicity pathways, we suggest a revised classification for multiple assays employed in evaluating cell viability and cell death. This classification is rooted in the cellular compartment and/or biochemical element involved, with a specific focus on mechanistic and essential aspects of the process. The assays are founded on diverse cell functions, encompassing metabolic activity, enzyme activity, cell membrane permeability and integrity, adenosine 5'-triphosphate content, cell adherence, reduction equivalents, dye inclusion or exclusion, constitutive protease activity, colony formation, DNA fragmentation and nuclear splitting. These assays present straightforward, reliable, sensitive, reproducible, cost-effective, and high-throughput approaches for appraising the effects of newly formulated chemotherapeutic biomolecules on the cell survival during the drug development process.

A novel donor-acceptor fluorescent probe for the fluorogenic/ chromogenic detection and bioimaging of nitric oxide

Nitric oxide (NO) plays an essential role in regulating various physiological and pathological processes. This has spurred various efforts to develop feasible methods for the detection of NO. Herein we designed and synthesized a novel donor-acceptor fluorescent probe Car-NO for the selective and specific detection of NO. Reaction of Car-NO with NO generated a new donor-acceptor structure with strong intramolecular charge transfer (ICT) effect, and led to remarkable chromogenic change from yellow to blue and dramatic fluorescence quenching. Car-NO exhibited high selectivity, excellent sensitivity, and rapid response for the detection of NO. In addition, the nanoparticles prepared from Car-NO (i.e., Car-NO NPs) showed strong NIR emission and high selectivity/sensitivity. Car-NO NPs was successfully employed to image both endogenous and exogenous NO in HeLa and RAW 264.7 cells. The present findings reveal that Car-NO is a promising probe for the detection and bioimaging of NO.

2,4,5-Triaminopyrimidines as blue fluorescent probes for cell viability monitoring: synthesis, photophysical properties, and microscopy applications

Monitoring cell viability is critical in cell biology, pathology, and drug discovery. Most cell viability assays are cell-destructive, time-consuming, expensive, and/or hazardous. Herein, we present a series of newly synthesized 2,4,5-triaminopyrimidine derivatives able to discriminate between live and dead cells. To our knowledge, these compounds are the first fluorescent nucleobase analogues (FNAs) with cell viability monitoring potential. These new fluorescent molecules are synthesized using highly efficient and cost-effective methods and feature unprecedented photophysical properties (longer absorption and emission wavelengths, environment-sensitive emission, and unprecedented brightness within FNAs). Using a live-dead Saccharomyces cerevisiae cell and theoretical assays, the fluorescent 2,4,5-triaminopyrimidine derivatives were found to specifically accumulate inside dead cells by interacting with dsDNA grooves, thus paving the way for the emergence of novel and safe fluorescent cell viability markers emitting in the blue region. As the majority of commercially available viability dyes emit in the green to red region of the visible spectrum, these novel markers might be useful to meet the needs of blue markers for co-staining combinations.

Single Fluorescent Probe for Multiple Tasks: Illuminating Lipid Droplets and Lysosomes in Dual Channels and Distinguishing Autophagy and Apoptosis

Lipid droplets (LDs) and lysosomes play key roles in autophagy and cell apoptosis, and the discriminative visualization of the two organelles and simultaneously of autophagy and apoptosis is very helpful to understand their internal relationships. However, fluorescent probes that can concurrently achieve these tasks are not available currently. Herein, we delicately fabricate a robust probe CAQ2 for multiple tasks: illumination of LDs and lysosomes in dual emission colors as well as discriminative visualization of cell apoptosis and autophagy. The probe exhibited both lipophilic and basic properties and displayed different emission colors in neutral and protonated forms; thus, LDs and lysosomes emitted blue and red fluorescence colors, respectively. Because of the lysosomal acidification during autophagy, CAQ2 detected autophagy with evidently enhanced red emission. Because of the lysosomal alkalization during apoptosis, CAQ2 imaged apoptosis with a drastically decreased red fluorescence intensity. With the robust probe, the autophagy under starvation and lipidless conditions was visualized, and the apoptosis induced by H2O2, ultraviolet (UV) irradiation, and rotenone treatment was successfully observed. The efficient detoxification of Na2S against rotenone treatment was successfully revealed.

Nondestructive, quantitative viability analysis of 3D tissue cultures using machine learning image segmentation

Ascertaining the collective viability of cells in different cell culture conditions has typically relied on averaging colorimetric indicators and is often reported out in simple binary readouts. Recent research has combined viability assessment techniques with image-based deep-learning models to automate the characterization of cellular properties. However, further development of viability measurements to assess the continuity of possible cellular states and responses to perturbation across cell culture conditions is needed. In this work, we demonstrate an image processing algorithm for quantifying features associated with cellular viability in 3D cultures without the need for assay-based indicators. We show that our algorithm performs similarly to a pair of human experts in whole-well images over a range of days and culture matrix compositions. To demonstrate potential utility, we perform a longitudinal study investigating the impact of a known therapeutic on pancreatic cancer spheroids. Using images taken with a high content imaging system, the algorithm successfully tracks viability at the individual spheroid and whole-well level. The method we propose reduces analysis time by 97% in comparison with the experts. Because the method is independent of the microscope or imaging system used, this approach lays the foundation for accelerating progress in and for improving the robustness and reproducibility of 3D culture analysis across biological and clinical research.

A lysosome-targeted fluorescent probe based on a BODIPY structure for Cys/Hcy detection

Cysteine (Cys) and homocysteine (Hcy) are important biothiols in living organisms. They play important roles in a variety of physiological and pathological processes. Therefore, it is very important to design an optical probe for the selective detection of Cys/Hcy. Herein, we report the design and synthesis of a fluorescent probe NBD-B-T based on a boron-dipyrromethene (BODIPY) structure, which showed an excellent lysosome targeting ability and an outstanding Cys/Hcy detection capacity. For NBD-B-T, the sensing group 7-nitro-2,1,3-benzoxadiazole (NBD) and the lysosomal targeting group morpholine were introduced. The results show that the NBD-B-T probe can detect Cys/Hcy with fluorescence emission turn-on performance. The low detection limits of this probe are about 76.0 nM for Hcy and 97.6 nM for Cys, respectively. The NBD-B-T probe has a low detection limit, high stability, and excellent selectivity and sensitivity. More importantly, the NBD-B-T can target lysosome, and simultaneously detect the Cys/Hcy in living cells.

Cancer-cell-specific Self-Reporting Photosensitizer for Precise Identification and Ablation of Cancer Cells

Cancer-cell-specific fluorescent photosensitizers (PSs) are highly desired molecular tools for cancer ablation with minimal damage to normal cells. However, such PSs that can achieve cancer specification and ablation and a self-reporting manner concurrently are rarely reported and still an extremely challenging task. Herein, we have proposed a feasible strategy and conceived a series of fluorescent PSs based on simple chemical structures for identifying and killing cancer cells as well as monitoring the photodynamic therapy (PDT) process by visualizing the change of subcellular localization. All of the constructed cationic molecules could stain mitochondria in cancer cells, identify cancer cells specifically, and monitor cancer cell viability. Among these, IVP-Br has the strongest ability to produce ROS, which serves as a potent PS for specific recognition and killing of cancer cells. IVP-Br could translocate from mitochondria to the nucleolus during PDT, self-reporting the entire therapeutic process. Mechanism study confirms that IVP-Br with light irradiation causes cancer cell ablation via inducing cell cycle arrest, cell apoptosis, and autophagy. The efficient ablation of tumor through PDT induced by IVP-Br has been confirmed in the 3D tumor spheroid chip. Particularly, IVP-Br could discriminate cancer cells from white blood cells (WBCs), exhibiting great potential to identify circulating tumor cells (CTCs).

Rational design of a ratiometric fluorescent probe for imaging lysosomal nitroreductase activity

Overexpressed nitroreductase (NTR) is often utilized to evaluate the hypoxic degree in tumor tissues, thus it is of great importance to develop high selective and efficient optical method to detect NTR. The dynamic fusion and function of lysosome promoted us to explore the possible appearance of NTR inside this organelle and to probe its behavior in a cellular context. In this work, a ratiometric fluorescent probe based on an extended π-π conjugation of a triphenylamine unit was designed for NTR detection and lysosomes imaging. The dual-emission mechanism of the probe in the presence of catalytic NTR was confirmed by theoretical study. The structure-function relationship between probe and NTR was revealed by docking calculations, suggesting a suitable structural and spatial match of them. The photophysical studies showed the probe had high selectivity, rapid response and a wide pH range towards NTR. MTT assay indicated the probe had low cytotoxicity in both normal (HUVEC) and tumor (MCF-7) cells. Furthermore, the inverse fluorescent imaging results confirmed the probe was NTR-active and exhibited time- and concentration-dependent fluorescence signals. In addition, the relatively high Pearson's correlation coefficient (0.99 in HepG2 and 0.97 in MCF-7 cells, compared to Lyso-Tracker Red) demonstrated the probe had excellent lysosomes colocalization. This study illustrates a ratiometric detection of NTR agent for lysosomes fluorescent imaging, which may provide a novel insight in molecular design.

Recent design strategies and applications of organic fluorescent probes for food freshness detection

Food spoilage poses a significant risk to human health, making the assessment of food freshness essential for ensuring food safety and quality. In recent years, there has been rapid progress in the development of fast detection technologies for food freshness. Among them, organic fluorescent probes have garnered significant attention in the field of food safety and sensing due to their easy functionalization, high sensitivity, and user-friendly nature. To comprehensively examine the latest advancements in organic fluorescent probes for food freshness detection, this review summarized their applications within the past five years. Initially, the fundamental detection principles of organic fluorescent probes are outlined. Subsequently, the recent research progress in utilizing organic fluorescent probes to detect various chemical indicators of freshness are discussed. Finally, the challenges and future directions for organic fluorescent probes in food freshness detection are elaborated upon. While, organic fluorescent probes have demonstrated their effectiveness in evaluating food freshness and possess great potential for practical applications, further research is still needed to enable their widespread commercial utilization. With continued advancements in synthesis and functionalization techniques, organic fluorescent probes will contribute to enhancing the efficiency of food safety detection.

Particle sorting method based on swirl induction

Fluid-based methods for particle sorting demonstrate increasing appeal in many areas of biosciences due to their biocompatibility and cost-effectiveness. Herein, we construct a microfluidic sorting system based on a swirl microchip. The impact of microchannel velocity on the swirl stagnation point as well as particle movement is analyzed through simulation and experiment. Moreover, the quantitative mapping relationship between flow velocity and particle position distribution is established. With this foundation established, a particle sorting method based on swirl induction is proposed. Initially, the particle is captured by a swirl. Then, the Sorting Region into which the particle aims to enter is determined according to the sorting condition and particle characteristic. Subsequently, the velocities of the microchannels are adjusted to control the swirl, which will induce the particle to enter its corresponding Induction Region. Thereafter, the velocities are adjusted again to change the fluid field and drive the particle into a predetermined Sorting Region, hence the sorting is accomplished. We have extensively conducted experiments taking particle size or color as a sorting condition. An outstanding sorting success rate of 98.75% is achieved when dealing with particles within the size range of tens to hundreds of micrometers in radius, which certifies the effectiveness of the proposed sorting method. Compared to the existing sorting techniques, the proposed method offers greater flexibility. The adjustment of sorting conditions or particle parameters no longer requires complex chip redesign, because such sorting tasks can be successfully realized through simple microchannel velocities control.

Probing local structure of glass with orientation-dependent luminescence

The local ordering of particles is considered an important process in glass transition. Ordering is usually observed in simulation and micrometer-sized colloid. However, clear information on local ordering at the molecular level is difficult to obtain experimentally. In this study, we prepared an easily glass-forming fluorophore with a color change owing to the intermolecular arrangement in the liquid, glass, and crystal states. The bathochromic shifts of the photoluminescence spectra indicated a change in the intermolecular orientation upon immediate cooling of the melt. The recovery of the spectra by successive heating indicated that rotation contributed to the change in the intermolecular orientation. The orientation in the glass was distinct from that during crystal growth, which was observed as a slow bathochromic shift by maintaining the temperature between the melting points of the blue- and green-luminescent crystals obtained from dichloromethane/ethanol and dichloromethane/hexane, respectively. Our results demonstrate that the anisotropic interaction between glass-forming luminophores is useful for uncovering molecular-level events in the glassy state.

Construction of a Dual-Emissive Probe for Discriminative Visualization of Lysosomal and Mitochondrial Dysfunction

Discriminatively visualizing mitochondrial and lysosomal dysfunction is crucial for an in-depth understanding of cell apoptosis regulation and relative biology. However, fluorescent probes for the separate visualization of lysosomal and mitochondria damages have not been reported yet. Herein, we have constructed a fluorescent probe [2-(4-hydroxystyryl)-1,3,3-trimethyl-3H-indol-1-ium iodide (HBSI)] for labeling mitochondria and lysosomes in dual emission colors and discriminatively imaging mitochondrial and lysosomal damage in two different sets of fluorescent signals. In living cells, HBSI targeted both lysosomes and mitochondria to give green and red emission, respectively. During mitochondrial damages, HBSI immigrated into lysosomes, and the red emission decreased. During lysosomal damage, HBSI immigrated into mitochondria, and the green emission decreased. With the robust probe, the different damaging sequences of mitochondria and lysosomes under different amounts of H2O2 and chloral hydrate have been revealed. The sequential damage of lysosomes and mitochondria during cell apoptosis induced by rotenone, paclitaxel, and colchicine has been discovered. Furthermore, the regulation of mitochondria, lysosome, and their interplay during autophagy was also observed with the probe.