Electrochemical approach for the development of a simple method for detecting cell apoptosis based on caspase-3 activity

Signal-On Detection of Caspase-3 with Methylene Blue-Loaded Metal-Organic Frameworks as Signal Reporters

In this work, we report on an electrochemical method for the signal-on detection of caspase-3 and the evaluation of apoptosis based on the biotinylation reaction and the signal amplification of methylene blue (MB)-loaded metal-organic frameworks (MOFs). Zr-based UiO-66-NH2 MOFs were used as the nanocarriers to load electroactive MB molecules. Recombinant hexahistidine (His6)-tagged streptavidin (rSA) was attached to the MOFs through the coordination interaction between the His6 tag in rSA and the metal ions on the surface of the MOFs. The acetylated peptide substrate Ac-GDEVDGGGPPPPC was immobilized on the gold electrode. In the presence of caspase-3, the peptide was specifically cleaved, leading to the release of the Ac-GDEVD sequence. A N-terminal amine group was generated and then biotinylated in the presence of biotin-NHS. Based on the strong interaction between rSA and biotin, rSA@MOF@MB was captured by the biotinylated peptide-modified electrode, producing a significantly amplified electrochemical signal. Caspase-3 was sensitively determined with a linear range from 0.1 to 25 pg/mL and a limit of detection down to 0.04 pg/mL. Further, the active caspase-3 in apoptosis inducer-treated HeLa cells was further quantified by this method. The proposed signal-on biosensor is compatible with the complex biological samples and shows great potential for apoptosis-related diagnosis and the screening of caspase-targeting drugs.

Translational selenium nanoparticles boost GPx1 activation to reverse HAdV-14 virus-induced oxidative damage

Human adenovirus (HAdV) can cause severe respiratory infections in immunocompromised patients, but its clinical treatment is seriously limited by side effects of drugs such as poor efficacy, low bioavailability and severe nephrotoxicity. Trace element selenium (Se) has been found will affect the disease progression of pneumonia, but its antivirus efficacy could be improved by speciation optimization. Therefore, herein we performed anti-HAdV effects of different Se speciation and found that lentinan (LNT)-decorated selenium nanoparticles (SeNPs) exhibited low cytotoxicity and excellent anti-HAdV antiviral activity. Furthermore, SeNPs@LNT reduced the HAdV infection-induced mitochondrial damage and excessive production of reactive oxygen species (ROS). It was also involved in the repair of host cell DNA damage and inhibition of viral DNA replication. SeNPs@LNT inhibited HAdV-induced apoptosis mainly by modulating the p53/Bcl-2 apoptosis signaling pathway. In vivo, SeNPs@LNT replenished Se by targeting the infected site through the circulatory system and was involved in the synthesis of Glutathione peroxidase 1 (GPx1). More importantly, GPx1 played an antioxidant and immunomodulatory role in alleviating HAdV-induced inflammatory cytokine storm and alleviating adenovirus pneumonia in Se-deficient mice. Collectively, this study provides a Se speciation of SeNPs@LNT with anti-HAdV activity, and demonstrate that SeNPs@LNT is a promising pharmaceutical candidate for the treatment of HAdV.

Magnetically-assisted electrochemical immunoplatform for simultaneous detection of active and total prostate-specific antigen based on proteolytic reaction and sandwich affinity analysis

Simultaneous detection of active and inactive proteases is clinically meaningful for improving diagnostic specificity. In this work, we reported an electrochemical method for simultaneous immunoassays of active and total proteases. Magnetic beads (MBs) were used as the solid supports for immobilization of capture antibodies and enrichment of targets. For the detection of active protease, the proteolytic-reaction-based analysis was carried out by the generation of Cu2+-binding peptide, in which a label-free peptide was used as the proteolytic substrate. The redox potential of the resulting peptide-Cu2+ complex was intrinsically distinguished from that of free Cu2+, thus allowing the "signal-on" detection of active protease. For the immunoassay of total protease in a sandwich-like format, electroactive metal-organic frameworks (Cu-MOFs) were used as the signal tags. The captured Cu-MOFs could directly produce a well-defined electrochemical signal from the reduction of Cu2+ ions. The analytical performances of the immunoplatform were evaluated by determining the model analytes of free and total prostate-specific antigen (fPSA and tPSA) in buffer and serum. The detection limits were found to be 0.3 pM for fPSA and 2 pM for tPSA. This work proposed a new strategy for simultaneous detection of active and total proteases, which should be evaluable for clinical diagnosis and treatment of protease-relative diseases.

Cleaved caspase-3 is present in the majority of glial cells in the intact rat spinal cord during postnatal life

Cell death is an essential process that occurs during the development of the central nervous system. Despite the availability of a wide range of commercially produced antibodies against various apoptotic markers, data regarding apoptosis in intact spinal cord during postnatal development and adulthood are mostly missing. We investigated apoptosis in rat spinal cord at different stages of ontogenesis (postnatal days 8, 29, and 90). For this purpose, we applied immunofluorescent detection of two widely used apoptotic markers, cleaved caspase-3 (cC3) and cleaved poly(ADP-ribose) polymerase (cPARP). Surprisingly, we found significant discrepancy between the number of cC3+ cells and PARP+ cells, with a ratio between 500:1 and 5000:1 in rat spinal cord at all postnatal time points. The majority of cC3+ cells were glial cells and did not exhibit an apoptotic phenotype. In contrast with in vivo results, in vitro analysis of primary cell cultures derived from neonatal rat spinal cord and treated with the apoptotic inductor staurosporine revealed a similar onset of occurrence of both cC3 and cPARP in cells subjected to apoptosis. Gene expression analysis of spinal cord revealed elevated expression of the Birc4 (XIAP), Birc2, and Birc5 (Survivin) genes, which are known potent inhibitors of apoptosis. Our data indicate that cC3 is not an exclusive marker of apoptosis, especially in glial cells, owing its possible presence in inhibited forms and/or its participation in other non-apoptotic roles. Therefore, cPARP appears to be a more appropriate marker to detect apoptosis.

Cytotoxicity, Differentiation, and Biocompatibility of Root-End Filling: A Comprehensive Study

Assessing the biocompatibility of endodontic root-end filling materials through cell line responses is both essential and of utmost importance. This study aimed to the cytotoxicity of the type of cell death through apoptosis and autophagy, and odontoblast cell-like differentiation effects of MTA, zinc oxide-eugenol, and two experimental Portland cements modified with bismuth (Portland Bi) and barium (Portland Ba) on primary cell cultures. Material and methods: The cells corresponded to human periodontal ligament and gingival fibroblasts (HPLF, HGF), human pulp cells (HPC), and human squamous carcinoma cells from three different patients (HSC-2, -3, -4). The cements were inoculcated in different concentrations for cytotoxicity evaluation, DNA fragmentation in electrophoresis, apoptosis caspase activation, and autophagy antigen reaction, odontoblast-like cells were differentiated and tested for mineral deposition. The data were subject to a non-parametric test. Results: All cements caused a dose-dependent reduction in cell viability. Contact with zinc oxide-eugenol induced neither DNA fragmentation nor apoptotic caspase-3 activation and autophagy inhibitors (3-methyladenine, bafilomycin). Portland Bi accelerated significantly (p < 0.05) the differentiation of odontoblast-like cells. Within the limitation of this study, it was concluded that Portland cement with bismuth exhibits cytocompatibility and promotes odontoblast-like cell differentiation. This research contributes valuable insights into biocompatibility, suggesting its potential use in endodontic repair and biomimetic remineralization.

Exploration of in vitro cytotoxic and in ovo antiangiogenic activity of ethyl acetate extract of Penicillium oxalicum

Fungal endophytes have established new paradigms in the area of biomedicine due to their ability to produce metabolites of pharmacological importance. The present study reports the in vitro cytotoxic and in ovo antiangiogenic activity of the ethyl acetate (EA) extract of Penicillium oxalicum and their chemical profiling through Gas Chromatography-Mass Spectrometry analysis. Treatment of the EA extract of P. oxalicum to the selected human breast cancer cell lines (MDA-MB-231 and MCF-7) leads to the reduced glucose uptake and increased nitric oxide production suggesting the cytotoxic activity of EA extract of P. oxalicum. Our results further show that treatment of EA extract of P. oxalicum attenuates the colony number, cell migration ability and alters nuclear morphology in both the human breast cancer cell lines. Furthermore, the treatment of EA extract of P. oxalicum mediates apoptosis by increasing the expression of BAX, P21, FADD, and CASPASE-8 genes, with increased Caspase-3 activity. Additionally, in ovo chorioallantoic membrane (CAM) assay showed that the treatment of EA extract of P. oxalicum leads to antiangiogenic activity with perturbed formation of blood vessels. Overall, our findings suggest that the EA extract of P. oxalicum show in vitro cytotoxic and antiproliferative activity against human breast cancer cell lines, and in ovo antiangiogenic activity in CAM model.

A General, Label-Free and Homogeneous Electrochemical Strategy for Probing of Protease Activity and Screening of Inhibitor

Proteases play a critical role in regulating various physiological processes from protein digestion to wound healing. Monitoring the activity of proteases and screening their inhibitors as potential drug molecules are of great importance for the early diagnosis and treatment of many diseases. In this work, we reported a general, label-free and homogeneous electrochemical method for monitoring protease activity based on the peptide–copper interaction. Cleavage of peptide substrate results in the generation of a copper-binding chelator peptide with a histidine residue in the first or third position (His¹ or His³) at the N-terminal. The redox potential and current of copper coordinated with the product are different from the free copper or the copper complex with the substrate, thus allowing for the detection of protease activity. Angiotensin-converting enzyme (ACE) and thrombin were determined as the model analytes. The label-free and homogeneous electrochemical method can be used for screening protease inhibitors with high simplicity and sensitivity.

Disposable biosensor based on novel ternary Ru-PEI@PCN-333(Al) self-enhanced electrochemiluminescence system for on-site determination of caspase-3 activity

The number of death due to cancer-related diseases each year is at the alarming level and is constantly growing. Tools that can effectively and conveniently detect cancer cell apoptosis can play a significant role in cancer research, cancer therapy, and other related industries. Herein, we fabricated, for the first time, an ultrasensitive, disposable, self-enhanced off-on electrochemiluminescence (ECL) biosensor based on ternary Ru-PEI@PCN-333(Al) system to determine caspase-3 activity, the biomarker of apoptosis. The biosensor had a low detection limit of 0.017 pg/mL and was able to enhance the ECL emission and stability. A solid-state (SS) ECL strategy was adopted to overcome the relatively weak ECL emission due to the long distance between electrochemiluminophore and electrode surface. The analysis requires only one incubation step, which can significantly reduce the operational complexity and time. The biosensor had higher sensitivity, and the off-on ECL mode was achieved using caspase-3 as a switch. The on-site and rapid detection capability of the biosensor was achieved by the introduction of disposable screen-printed electrodes (SPEs). This study lays a foundation for the development of more advanced, ingenious, portable and reliable ECL devices for biosensing not only caspase-3, but also other bioanalytes.

Optical/electrochemical methods for detecting mitochondrial energy metabolism

This review highlights the biological importance of mitochondrial energy metabolism and the applications of multiple optical/electrochemical approaches to determine energy metabolites. Mitochondria, the main sites of oxidative phosphorylation and adenosine triphosphate (ATP) biosynthesis, provide the majority of energy required by aerobic cells for maintaining their physiological activity. They also participate in cell growth, differentiation, information transmission, and apoptosis. Multiple mitochondrial diseases, caused by internal or external factors, including oxidative stress, intense fluctuations of the ionic concentration, abnormal oxidative phosphorylation, changes in electron transport chain complex enzymes and mutations in mitochondrial DNA, can occur during mitochondrial energy metabolism. Therefore, developing accurate, sensitive, and specific methods for the in vivo and in vitro detection of mitochondrial energy metabolites is of great importance. In this review, we summarise the mitochondrial structure, functions, and crucial energy metabolic signalling pathways. The mechanism and applications of different optical/electrochemical methods are thoroughly reviewed. Finally, future research directions and challenges are proposed.

Surface Plasmon Resonance for Protease Detection by Integration of Homogeneous Reaction

The heterogeneous assays of proteases usually require the immobilization of peptide substrates on the solid surface for enzymatic hydrolysis reactions. However, immobilization of peptides on the solid surface may cause a steric hindrance to prevent the interaction between the substrate and the active center of protease, thus limiting the enzymatic cleavage of the peptide. In this work, we reported a heterogeneous surface plasmon resonance (SPR) method for protease detection by integration of homogeneous reaction. The sensitivity was enhanced by the signal amplification of streptavidin (SA)-conjugated immunoglobulin G (SA-IgG). Caspase-3 (Cas-3) was determined as the model. A peptide labeled with two biotin tags at the N- and C-terminals (bio-GDEVDGK-bio) was used as the substrate. In the absence of Cas-3, the substrate peptide was captured by neutravidin (NA)-covered SPR chip to facilitate the attachment of SA-IgG by the avidin-biotin interaction. However, once the peptide substrate was digested by Cas-3 in the aqueous phase, the products of bio-GDEVD and GK-bio would compete with the substrate to bond NA on the chip surface, thus limiting the attachment of SA-IgG. The method integrated the advantages of both heterogeneous and homogeneous assays and has been used to determine Cas-3 inhibitor and evaluate cell apoptosis with satisfactory results.

Cypermethrin induces Sertoli cell apoptosis through mitochondrial pathway associated with calcium

Cypermethrin, one kind of pyrethroid pesticides, has been shown to act as endocrine-disrupting chemicals (EDCs). The purpose of this study was to explore the roles of Sertoli cell apoptosis through mitochondrial pathway associated with calcium (Ca²⁺) in cypermethrin-induced male reproductive toxicology. The mouse Sertoli cells TM4 were cultured with 0 μM, 10 μM, 20 μM, 40 μM and 80 μM of cypermethrin. We used flow cytometry, Fluo-4 AM, western blot and JC-1 Assay Kit to examine apoptosis, intracellular Ca²⁺, expressions of mitochondrial apoptotic pathway-related proteins and mitochondrial membrane potential. We found cypermethrin increased apoptosis rate of TM4 cells significantly and with a significant increase in intracellular Ca²⁺ concentration. Cypermethrin significantly decreased the protein expressions of cytosolic B-cell lymphoma-2 (Bcl-2) and mitochondrial cytochrome c (Cyt-c). The protein expressions of cytosolic Bcl-2-associated x (Bax), Cyt-c, cleaved caspase-3, calmodulin (CaM), Ca²⁺/CaM-dependent protein kinases II (CaMKII) and phosphorylated CaMKII were increased significantly in cypermethrin-exposed TM4 cells. Cypermethrin decreased mitochondrial membrane potential significantly. Then, Bcl-2 family and Ca²⁺/CaM/CaMKII pathway participate in cypermethrin-induced homeostasis. Ca²⁺ overload activates mitochondrial pathway by increasing permeability of mitochondrial membrane and decreasing mitochondrial membrane potential. We suggest cypermethrin induces Sertoli cell apoptosis involving mitochondrial pathway associated with Ca²⁺ regulated by Bcl-2 family and Ca²⁺/CaM/CaMKII pathway. The study provides a new insight into mechanisms involved in cypermethrin-induced male reproductive toxicology.

Widening the applications of the Just-Dip-It approach: a solid contact screen-printed ion-selective electrode for the real-time assessment of pharmaceutical dissolution testing in comparison to off-line HPLC analysis

Over past years, the field of pharmaceutical dissolution testing has significantly expanded to cover not only the quality control of dosage forms, but also to play an important role in the bioavailability testing paradigm and screening of most formulations. These tests usually need a very long time sampling and monitoring, so that the automation of sampling is laborsaving. Problems often occur with these automatic devices due to sampling lines that may disconnect, crimp, carry over, become mixed up, or are inadequately cleaned. Potentiometric sensors, such as liquid contact (LC-ISE) or solid contact ion-selective electrodes (SC-SP-ISE), can provide timely data to be used for the real-time tracking of the amount of active pharmaceutical ingredients (APIs) released in the dissolution medium without these problems. In this work, we adopted the Just-Dip-It approach as a process analytical technology solution with the ultimate goal of advancing the ion selective sensors to their most effective use in pharmaceutical analysis. Two sensors were fabricated, the traditional LC-ISE and SC-SP-ISE. The sensing poly-vinyl chloride membranes of two electrodes were prepared using 2-nitrophenyl octyl ether as a plasticizer to soften the membrane, and the reduction in resistance to pioglitazone ions (PIO) permeability was achieved through the incorporation of sodium tetraphenylborate and calix[8]arene as a cationic exchanger salt and inclusion complexing ligand, respectively. Finally, prepared membranes were turned into the flexible perm-selective slices of hydrophobic plastic, which work as a barrier to other compounds, except for the PIO cation in the concentration range of 1 × 10-6 to 1 × 10-2 M and 1 × 10-5 to 1 × 10-2 M for SC-SP-ISE and LC-ISE, respectively. The challenges and opportunities of both sensors in comparison to a developed HPLC method were discussed for the dissolution testing of the combination dosage forms of pioglitazone. Potentiometric methods were validated according to IUPAC guidelines, while HPLC was validated according to ICH guidelines to ensure accuracy and precision.

Protease Biosensor by Conversion of a Homogeneous Assay into a Surface-Tethered Electrochemical Analysis Based on Streptavidin-Biotin Interactions

This work proposed a new sensing strategy for protease detection by converting a homogeneous assay into a surface-tethered electrochemical analysis. Streptavidin (SA), a tetramer protein, was used as the sensing unit based on the SA-biotin coupling chemistry. Caspase-3 was used as the model analyte, and a biotinylated peptide with a sequence of biotin-GDEVDGK-biotin was designed as the substrate. Specifically, the peptide substrate could induce an assembly of SA to form (SA-biotin-GDEVDGK-biotin)_n aggregates through SA-biotin interactions, which was confirmed by atomic force microscopy (AFM). The peptide substrate-induced assembly of SA was facilely initiated on an electrode-liquid surface by modification of the electrode with SA. The in situ formation of (SA-biotin-GDEVDGK-biotin)_n aggregates created an insulating layer, thus limiting the electron transfer of ferricyanide. Once the peptide substrate was cleaved into two shorter fragments (biotin-GDEVD and GK-biotin) by caspase-3, the resulting products would compete with biotin-GDEVDGK-biotin to bind SA proteins immobilized on the electrode surface and distributed in a solution, thus preventing the in situ formation of (SA-biotin-GDEVDGK-biotin)_n assemblies. With the simple principle of the substrate-induced assembly of SA, a dual-signal amplification was achieved with improved sensitivity. Taking advantage of high sensitivity, simple principle, and easy operation, this method can be augmented to design various surface-tethered biosensors for practical applications.

Electrochemical determination of caspase-3 using signal amplification by HeLa cells modified with silver nanoparticles

An electrochemical sensor capable of quantitative determination of caspase-3 activities was developed. A thiolated peptide whose sequence contained a caspase-3 cleaved site and a cell penetration sequence was preimmobilized onto an electrode. The quantification of caspase-3 was accomplished after cell penetration and the subsequent adsorption of silver nanoparticles (AgNPs). The oxidation current of AgNPs was found to be inversely proportional to the concentration of caspase-3 between 0.02 and 0.2 U/mL. A detection limit of 0.02 U/mL for caspase-3 was achieved due to the large number of positively charged AgNPs adsorbed onto the negatively charged cells. The proof of concept was demonstrated by monitoring the cleavage of surface-confined peptide substrates by caspase-3 in cell lysates. The current sensor could be extended to detect cells by replacing the surface-confined peptide with aptamers that recognize cells. Thus, the use of a cell as a matrix for AgNPs shows excellent potential for constructing electrochemical sensors and provides a useful alternative for sensor development in the future. Cells modified with silver nanoparticles were utilized as the electrochemical readout of an electrochemical assay.

Highly sensitive detection of caspase-3 activity based on peptide-modified organic electrochemical transistor biosensors

Caspase-3 is an important proteolytic enzyme that cleaves several key substrates in apoptotic processes, resulting in DNA fragmentation, the degradation of nuclear proteins, and the formation of apoptotic bodies. However, it is challenging to detect caspase-3 due to its low expression levels in cells. In this work, organic electrochemical transistors (OECTs) are used in the detection of caspase-3 for the first time. A self-assembled monolayer of the peptide is bonded to the Au gate electrode (GE) of an OECT via gold-sulphur bonds. It is found that the transfer curve of the transistor shifts to a lower gate voltage due to the modulation of the surface potential of the GE by the peptides. Then, the device is used in the detection of caspase-3 in aqueous solutions and shows a detection limit of 0.1 pM. Due to its high sensitivity, the device can detect caspase-3 in induced apoptotic HeLa cells. The system is low-cost, conveniently used and applicable for biological and medical monitoring where caspase-3 detection and quantification are required.

Knockdown of long non‑coding RNA ANRIL inhibits the proliferation and promotes the apoptosis of Burkitt lymphoma cells through the TGF‑β1 signaling pathway

Burkitt lymphoma (BL) has a high mortality rate and its treatment is currently limited to chemotherapy combined with immunotherapy. The long non-coding RNA antisense non-coding RNA in the INK4 locus (ANRIL) has been identified as an oncogene that can regulate cell proliferation and apoptosis in multiple types of cancer. However, the function of ANRIL in BL remains unknown. The present study aimed to determine the effect of ANRIL on cell proliferation and apoptosis in BL. Reverse transcription-quantitative PCR was used to analyze the expression levels of ANRIL in BL cells. The effect of ANRIL knockdown on BL cells was determined using Cell Counting Kit-8, flow cytometric, western blotting, immunofluorescence staining and Hoechst staining assays. The results revealed that ANRIL silencing inhibited the proliferation and promoted the apoptosis of BL cells. In addition, the expression levels of cyclin D1, E2F transcription factor 1 and Bcl-2 were downregulated, while the expression levels of cyclin-dependent kinase inhibitor 1A, Bcl-2-associated X protein, cleaved-caspase-9/pro-caspase-9 and cleaved-caspase-3/pro-caspase-3 were upregulated. Furthermore, the knockdown of ANRIL activated the TGF-β1 signaling pathway, as evidenced by the upregulated expression levels of TGF-β1, phosphorylated (p)-SMAD2/3/SMAD2/3, p-SMAD1/SMAD1 and sphingosine-1-phosphate receptor 2. Moreover, the protective effect of ANRIL silencing in BL could be inhibited by the TGF-β receptor type I/II dual inhibitor, LY2109761. In conclusion, the findings of the present study suggested that the knockdown of ANRIL may inhibit cell proliferation and promote cell apoptosis in BL by regulating the TGF-β1 signaling pathway, which may provide a novel target for the treatment of BL.

Protease-responsive mass barcoded nanotranslators for simultaneously quantifying the intracellular activity of cascaded caspases in apoptosis pathways

Quantitatively delineating the activation network of multiple proteases that participate in cellular processes is highly essential for understanding the physiological and pathological states of cells. In this study, protease-responsive mass barcoded nanotranslators (PRMNTs) were engineered for revealing the activity of cascaded caspases in apoptosis in a multiplex and quantitative manner. In the PRMNTs, a series of mass tag-decorated gold nanoparticles (AuNPs) were tethered onto magnetic Fe₃O₄ nanospheres via a linker containing the substrate peptide of the target protease to form a "one-to-many" core-satellite structure. This nanostructure was internalized into the cells, underwent an enzymatic reaction within the cells, and allowed post-reaction mass spectrometry (MS) interrogation after magnetic separation from the cells. In the presence of intracellular caspases, enzymatic cleavage of the linker could be translated to the decreased ion signals of the mass tags on the remaining AuNPs in the PRMNTs by MS decoding. Benefiting from the multiplexing capability of MS, the intracellular activity of caspase-3, -8 and -9 that orchestrate the apoptotic process was simultaneously quantified at any given time. Kinetic analysis of caspase activity under stimulation of diverse anticancer drugs revealed that programmed cell death followed individual apoptosis pathways, differing in the activation degree and sequence of the caspase cascade. This work represents a modality that interfaces nanotechnology with MS for quantitatively probing the intracellular activity of multiple proteases, which opens up new avenues for revealing the apoptosis mechanism and developing innovative drugs.

Taurine prevents cardiomyocyte apoptosis by inhibiting the calpain-1/cytochrome c pathway during RVH in broilers

The calpain-1-activated apoptotic pathway plays a key role in right ventricular hypertrophy (RVH). Taurine has been shown to attenuate apoptosis by inhibiting calpain activity. This experiment aimed to determine whether taurine could prevent RVH by inhibiting the calpain-1/cytochrome c apoptotic pathway. The broilers were given 1% taurine dissolved in drinking water and were raised at 10 °C ~ 12 °C from day 21 to day 42. At 21 d, 28 d, 35 d and 42 d, the right ventricular (RV) tissues were collected. Increased RVH index, angiotensin II, norepinephrine and atrial natriuretic peptide mRNA expression were reduced by taurine in the broiler RVs. Taurine obviously inhibited cardiomyocyte apoptosis via maintaining the mitochondrial membrane potential and decreased the activation of caspase-9 and caspase-3 in the broiler RVs. The antioxidant assay demonstrated that taurine enhanced the activities of superoxide dismutase, total antioxidant capacity and glutathione peroxidase and the glutathione/glutathione disulfide ratio. Western blot results revealed that taurine also downregulated the expression of calpain-1 and cytosolic cytochrome c while upregulating the expression of Bcl-2/Bax and mitochondrial cytochrome c in broiler cardiomyocytes during RVH. In summary, we found that taurine could enhance cardiomyocyte antioxidant ability and further prevented cardiomyocyte apoptosis by inhibiting the calpain-1/cytochrome c pathway during RVH in broilers.

Dual-channel surface plasmon resonance monitoring of intracellular levels of the p53-MDM2 complex and caspase-3 induced by MDM2 antagonist Nutlin-3

MDM2 can mediate the degradation of tumor suppressor p53 through an autoregulatory feedback loop, in which MDM2 abolishes wild-type p53 function and accelerates malignant transformation. However, the incorporation of MDM2 antagonist Nutlin-3 could reactivate the transcriptional activity of p53, up-regulate caspase-3, and induce apoptosis. In this work, the simultaneous and label-free monitoring of p53-MDM2 complex and caspase-3 levels in cancer cells before and after Nutlin-3 treatment was conducted using dual-channel surface plasmon resonance (SPR). The p53-MDM2 complex was captured in one fluidic channel covered with consensus double-stranded (ds)-DNA, while the other channel was pre-immobilized with caspase-3-specific biotinylated DEVD-containing peptides. To amplify the SPR signals, the attachment of streptavidin (SA)-conjugated anti-MDM2 antibody in both channels was achieved. The signal diversity before and after Nutlin-3 treatment is indicative of the difference in the levels of the intracellular p53-MDM2 complex and caspase-3. The limit of detection for p53-MDM2 and caspase-3 down to 4.54 pM and 0.03 ng mL^-1, respectively, was attained. Upon treatment with Nutlin-3, MCF-7 cancer cells with wild-type p53 showed decreased expression of the p53-MDM2 complex and an increased caspase-3 level, while MDA-MB-231 cancer cells with mutant p53 exhibited an elevated caspase-3 level and unchanged p53-MDM2 complex expression. The apoptosis of MCF-7 and MDA-MB-231 cancer cells upon Nutlin-3 treatment follows a p53-dependent and a p53-independent pathway, respectively. The proposed method is sensitive, selective and label-free, holding great promise for assaying intracellular p53-MDM2 complex and caspase-3 levels and differentiating Nutlin-3-mediated p53-dependent or p53-independent apoptotic pathways.

Image-Based Quantification of Cell Debris as a Measure of Apoptosis

Apoptosis is a controlled form of cell death that can be induced by various diseases and exogenous toxicants. Common apoptosis-detection methods rely on fluorescent markers, which necessitate the use of costly reagents and time-consuming labeling procedures. Label-free methods avoid these problems, but often require specialized instruments instead. Here, we utilize apoptotic-cell disintegration to develop a novel label-free detection method based on the quantification of subcellular debris particles in bright-field-microscopy images. Debris counts show strong correlations with fluorescence-based annexin V staining and can be used to study concentration-dependent and temporal apoptosis activation. The method is rapid, low-cost, and easy to apply, as the only experimental step comprises bright-field imaging of culture-media samples followed by automated image processing. The late-stage nature of the debris measurement means that the method can complement other, established apoptosis assays, and its accessibility will allow a wider community of researchers to study apoptotic cell death.

Sensitive detection of caspase-3 enzymatic activities and inhibitor screening by mass spectrometry with dual maleimide labelling quantitation

There is a great need to develop sensitive and specific methods for quantitative analysis of caspase-3 activities in cell apoptosis.

Micro/nanoelectrochemical probe and chip devices for evaluation of three-dimensional cultured cells

Herein, we present an overview of recent research progress in the development of micro/nanoelectrochemical probe and chip devices for the evaluation of three-dimensional (3D) cultured cells. First, we discuss probe devices: a general outline, evaluation of O₂ consumption, enzyme-modified electrodes, evaluation of endogenous enzyme activity, and the collection of cell components from cell aggregates are discussed. The next section is focused on integrated chip devices: a general outline, electrode array devices, smart electrode array devices, droplet detection of 3D cultured cells, cell manipulation using dielectrophoresis (DEP), and electrodeposited hydrogels used for fabrication of 3D cultured cells on chip devices are discussed. Finally, we provide a summary and discussion of future directions of research in this field.

Plasmonic Au nanostar Raman probes coupling with highly ordered TiO2/Au nanotube arrays as the reliable SERS sensing platform for chronic myeloid leukemia drug evaluation

The accurate therapeutic evaluation for chronic myeloid leukemia (CML) drug is of great importance to minimize side effects and enhance efficacy. Herein, a facile and precise surface-enhanced scattering (SERS) approach based on coupled plasmonic field has been introduced to evaluate the therapeutic outcomes of antileukemia drug through ultrasensitive assay of caspase-3 activity in apoptotic cells. Caspase-3 as an apoptosis indicator could specifically cleave the N-terminus of biotinylated DEVD-peptide (biotin-Gly-Asp-Gly-Asp-Glu-Val-Asp-Gly-Cys) immobilized on the Au nanoparticle-decorated TiO₂ nanotube arrays (TiO₂/Au NTAs) substrate. After the enzyme cleavage with caspase-3, Raman-labelled Au nanostar (AuNS) probes captured the residual DEVD-peptides via the recognition between streptavidin and biotin, thus resulting in an enhanced Raman response on the SERS platform. The variation of Raman intensity revealed caspase-3 activity that reflected the chemotherapeutic effect. On this platform, AuNS nanoprobes offered a large number of binding sites and intrinsic "hot spots" for Raman reporters, while TiO₂/Au NTAs rendered a homogenously coupled electromagnetic field between the adjacent repeated units over the large area. In particular, a spatially expanding plasmonic field formed by coupling AuNSs with TiO₂/Au NTAs would further heighten Raman enhancement. Taking these advantages, the strong and uniform Raman signals were achieved. Furthermore, the practicability investigation witnessed that the proposed SERS strategy was available to evaluate the therapeutic effect of dasatinib on CML K562 cells. The developed method possesses fascinating advantages of cost-effectiveness, excellent reproducibility and high sensitivity, which endows it with promising potential in apoptosis monitoring and anticancer drug development.

Quantum dots-based fluorescence resonance energy transfer biosensor for monitoring cell apoptosis

The development of advanced methods for accurately monitoring cell apoptosis has extensive significance in the diagnostic and pharmaceutical fields. In this study, we developed a rapid, sensitive and selective approach for the detection of cell apoptosis by combining the site-specific recognition and cleavage of the DEVD-peptide with quantum dots (QDs)-based fluorescence resonance energy transfer (FRET). Firstly, biotin-peptide was conjugated on the surface of AuNPs to form AuNPs-pep through the formation of an Au-S bond. Then, AuNPs-pep-QDs nanoprobe was obtained through the connection between AuNPs-pep and QDs. FRET is on and the fluorescence of QDs is quenched at this point. The evidence of UV-vis spectra, transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy revealed that the connection was successful. Upon the addition of apoptosis cell lysis solution, peptide was cleaved by caspase-3, and AuNPs was dissociated from the QDs. At this time, FRET is off, and thus the QDs fluorescence was recovered. The experimental conditions were optimized in terms of ratio of peptide to AuNPs, buffer solution, and the temperature of conjugation and enzyme reaction. The biosensor was successfully applied to distinguishing apoptosis cells and normal cells within 2 h. This study demonstrated that the biosensor could be utilized to evaluate anticancer drugs.

Novel organotin(iv) complexes derived from 4-fluorophenyl-selenoacetic acid: synthesis, characterization and in vitro cytostatic activity evaluation

A cluster of novel organotin(iv) complexes were designed, synthesized, and characterized by elemental analysis, FT-IR, and NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy as well as single-crystal X-ray diffraction.

Reduced graphene oxide decorated with gold nanoparticle as signal amplification element on ultra-sensitive electrochemiluminescence determination of caspase-3 activity and apoptosis using peptide based biosensor

Introduction: Growing demands for ultrasensitive biosensing have led to the development of numerous signal amplification strategies. In this report, a novel electrochemiluminescence (ECL) method was developed for the detection and determination of caspase-3 activity based on reduced graphene oxide sheets decorated by gold nanoparticles as signal amplification element and horseradish peroxidase enzyme (HRP) as ECL intensity enhancing agent. Methods: The ECL intensity of the luminol was improved by using the streptavidin coated magnetic beads and HRP in the presence of hydrogen peroxide. The cleavage behavior of caspase-3 was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques using biotinylated peptide (DEVD containing peptide) which was coated on reduced graphene oxide decorated with gold nanoparticle. The surface modification of graphene oxide was successfully confirmed by FTIR, UV-vis and x-ray spectroscopy. Results: ECL based biosensor showed that the linear dynamic range (LDR) and the lower limit of quantification (LLOQ) were 0.5-100 and 0.5 femtomolar (fM), respectively. Finally, the performance of the engineered peptide based biosensor was validated in the A549 cell line as real samples. Conclusion: The prepared peptide based biosensor could be considered as an excellent candidate for early detection of apoptosis, cell turnover, and cancer related diseases.

Electrochemiluminescent Sensing for Caspase-3 Activity Based on Ru(bpy)3(2+)-Doped Silica Nanoprobe

Caspase-3 is one of the most frequently activated cysteine proteases during the apoptosis process and has been identified as a well-established cellular marker of apoptosis. In this study, a novel approach for the sensitive determination of caspase-3 activity was proposed using electrochemiluminescence (ECL) of Ru(bpy)3(2+)-doped silica (Ru@SiO2) with tripropylamine (TPA) as coreactant. A nanocomposite containing gold nanoparticles (AuNPs), poly(dimethyldiallyl ammonium chloride) (PDDA), and multiwalled carbon nanotubes (CNTs) was fabricated as an ECL platform. The biotinylated DEVD-peptide (biotin-Gly-Asp-Gly-Asp-Glu-Val-Asp-Gly-Cys) was immobilized on the nanocomposite surface via the strong bonding interaction between AuNPs and the thiol group. Then the streptavidin-modified Ru(bpy)3(2+)-doped silica (Ru@SiO2-SA) was immobilized on the ECL platform via the specific interaction between biotin and streptavidin to generate ECL signal. Caspase-3 can specifically recognize and cleave the N-terminus of DEVD, leading to the loss of the biotin label and the decrease of ECL intensity to determine the activity of caspase-3. The results revealed a new ECL avenue for the sensitive and specific monitor of caspase-3, and the platform could be utilized to evaluate anticancer drugs.

Application of inductively coupled plasma mass spectrometry in the study of apoptosis: determination of caspase-3 using a gold nanoparticle tag

Apoptosis is a main type of cell death in which caspase-3 plays a key role. In this work, a simple, fast and sensitive immunoassay for caspase-3 is established by using inductively coupled plasma mass spectrometry (ICP-MS) detection and signal enhancement gold nanoparticle (Au-NP) labelling of the secondary antibody (IgG). After the immunoreaction of caspase-3, primary antibody and Au-NP labeled IgG, the concentration of caspase-3 was determined by ICP-MS analysis of the Au-NPs released from the immunocomplex. Under the optimized conditions, a limit of detection (LOD, 3σ) of 0.42 ng mL(-1) (0.31 nM) was obtained for caspase-3, with a dynamic range of 1-200 ng mL(-1) and a relative standard deviation of 4.1% (c = 5 ng mL(-1), n = 11). The proposed method has good specificity towards caspase-3. To demonstrate the application potential of the proposed method, the cell lysates of Hg(2+)-induced HepG2 cells were analyzed, and it was found that the concentration of caspase-3 increased when increasing the incubation concentration of Hg(2+). This method is easy, sensitive and selective, and has excellent capability of tolerating a complex biological matrix, indicating the potential of the ICP-MS-based assay in the study of apoptosis.

Reduction-responsive polypeptide nanogel delivers antitumor drug for improved efficacy and safety

Chemotherapy plays an irreplaceable role in the treatment of various malignant tumors today. The traditional drug formulations lack of selectivity, cause serious damage to normal tissues, and can't achieve a desired therapeutic efficacy. For this situation, a facilely prepared reduction-responsive polypeptide nanogel was employed for targeting intracellular delivery of antitumor drug in this study. Doxorubicin (DOX) as a model drug was loaded into nanogel through a sequential dispersion and dialysis approach with a drug loading efficiency (DLE) of 56.8wt.%. The loading nanogel, i.e., NG/DOX, exhibited a medium hydrodynamic radius of 56.1±3.5nm, glutathione-accelerated DOX release, and efficient cellular uptake and proliferation inhibition. Moreover, NG/DOX exhibited upregulated intratumoral accumulation and improved antitumor efficacy toward HepG2 hepatoma-xenografted BALB/c nude mouse model compared with free drug. The enhanced tumor suppression of NG/DOX was further confirmed by the histopathological and immunohistochemical analyses. Furthermore, the excellent in vivo security of NG/DOX was systematically demonstrated by the variation detection of body weight, histopathological assay, levels of bone marrow cell micronucleus rate (BMMR) and white blood cells (WBCs), and detection of clinical parameters in corresponding organs and serum. With controllable large-scale preparation and fascinating properties in vitro and in vivo, the reduction-responsive polypeptide nanogel is revealed to exhibit great potential for on-demand intracellular delivery of antitumor drugs, and shows a good prospect for clinical chemotherapy.

STATEMENT OF SIGNIFICANCE

The traditional drug formulations lack of selectivity, cause serious damage to normal tissues, and can't achieve a desired therapeutic effect. For this situation, a facilely prepared reduction-responsive polypeptide nanogel is employed for targeting intracellular delivery of antitumor drug in this study. The laden nanogel keeps structural integrity and less drug release in the circulatory system after intravenous injection, releases the payload triggered by the intracellular high concentration of GSH, and exhibits the excellent tumor inhibition and security in vivo. Furthermore, the other hydrophobic antitumor drugs can also be on-demand delivered by the smart nanogel. All of the above advantages confirm the bright prospect of reduction-responsive nanogel on the road of malignancy chemotherapy.

One-Pot Fabrication of Dendritic NiO@carbon-nitrogen Dot Electrodes for Screening Blood Glucose Level in Diabetes

Selective and sensitive glucose sensors with fast response for screening diabetic blood level are demanded. In this paper, the one-pot nanoarchitecture of dendritic NiO@carbon-nitrogen (C-N) dots (designated as NCD) sphere-wrapping Ni foam electrodes are reported as an effective and sensitive glucose sensor in blood samples. In this construction design, the NCD sphere electrode with excessive surface defects, large fractions of catalytic active sites, high surface area, and mobility of electron transfer through the actively surface NCD sphere can massively enhance the electrocatalytic activity for nonenzymatic glucose detection in diabetic blood. This portable sensor enables highly sensitive recognition of glucose detection (≈0.01 × 10^-6 m) over a wider linear range (≈0.005-12 × 10^-3 m) with rapid response time of a few seconds. The key result is that the engineered NCD sphere electrodes function as simple, easy-to-use electrochemical sensing assays of glucose levels in diabetic blood patients with a wide range of precision or linearity, recyclability, and excellent selectivity, even in the presence of potentially interfering organic (ascorbic acid, uric acid, dopamine, lactose, maltose, and sucrose) and inorganic (NaCl, Na₂ SO₄ , KCl, and K₂ SO₄ ) species. The results demonstrate the potential for the electrochemical sensors to be used in preventing serious health problems associated with diabetes mismanagement.