Hyperglycemia-induced oxidative stress exacerbates mitochondrial apoptosis damage to cochlear stria vascularis pericytes via the ROS-mediated Bcl-2/CytC/AIF pathway.

OBJECTIVES: Diabetes is closely linked to hearing loss, yet the exact mechanisms remain unclear. Cochlear stria vascularis and pericytes (PCs) are crucial for hearing. This study investigates whether high glucose induces apoptosis in the cochlear stria vascularis and pericytes via elevated ROS levels due to oxidative stress, impacting hearing loss. METHODS: We established a type II diabetes model in C57BL/6J mice and used auditory brainstem response (ABR), Evans blue staining, HE staining, immunohistochemistry, and immunofluorescence to observe changes in hearing, blood-labyrinth barrier (BLB) permeability, stria vascularis morphology, and apoptosis protein expression. Primary cultured stria vascularis pericytes were subjected to high glucose, and apoptosis levels were assessed using flow cytometry, Annexin V-FITC, Hoechst 33342 staining, Western blot, Mitosox, and JC-1 probes. RESULTS: Diabetic mice showed decreased hearing thresholds, reduced stria vascularis density, increased oxidative stress, cell apoptosis, and decreased antioxidant levels. High glucose exposure increased apoptosis and ROS content in pericytes, while mitochondrial membrane potential decreased, with AIF and cytochrome C (CytC) released from mitochondria to the cytoplasm. Adding oxidative scavengers reduced AIF and CytC release, decreasing pericyte apoptosis. DISCUSSION: Hyperglycemia may induce mitochondrial apoptosis of cochlear stria vascularis pericytes through oxidative stress.

The Increase in the Peroxidase Activity of the Cytochrome C with Substitutions in the Universal Binding Site Is Associated with Changes in the Ability to Interact with External Ligands.

Cytochrome c (CytC), a one-electron carrier, transfers electrons from complex bc1 to cytochrome c oxidase (CcO) in the electron-transport chain. Electrostatic interaction with the partners, complex bc1 and CcO, is ensured by a lysine cluster near the heme forming the Universal Binding Site (UBS). We constructed three mutant variants of mitochondrial CytC with one (2Mut), four (5Mut), and five (8Mut) Lys->Glu substitutions in the UBS and some compensating Glu->Lys substitutions at the periphery of the UBS for charge compensation. All mutants showed a 4-6 times increased peroxidase activity and accelerated binding of cyanide to the ferric heme of CytC. In contrast, decomposition of the cyanide complex with ferrous CytC, as monitored by magnetic circular dichroism spectroscopy, was slower in mutants compared to WT. Molecular dynamic simulations revealed the increase in the fluctuations of Cα atoms of individual residues of mutant CytC compared to WT, especially in the Ω-loop (70-85), which can cause destabilization of the Fe…S(Met80) coordination link, facilitation of the binding of exogenous ligands cyanide and peroxide, and an increase in peroxidase activity. It was found that only one substitution K72E is enough to induce all these changes, indicating the significance of K72 and the Ω-loop (70-85) for the structure and physiology of mitochondrial CytC. In this work, we also propose using a ferro-ferricyanide buffer as a substrate to monitor the peroxidase activity of CytC. This new approach allows us to determine the rate of peroxidase activity at moderate (200 µM) concentrations of H2O2 and avoid complications of radical formation during the reaction.

[Ergosterol peroxide inducing apoptosis of human hepatocellular carcinoma by regulating mitochondrial apoptosis pathway].

This study aims to investigate the effect of ergosterol peroxide(EP) on the apoptosis of human hepatocellular carcinoma and its mechanism of action. The cell viability of HepG2 and SK-Hep-1 cells with 0(blank control), 2.5, 5, 10, 20, 40, and 80 µmol·L~(-1) of EP after 24, 48, and 72 h of action was detected by using CCK-8 assay, and the half inhibitory concentrations(IC_(50)) at 24, 48, and 72 h were calculated. Formal experiments were performed to detect the effect of EP on intracellular reactive oxygen species(ROS) using DCFH-DA staining, the effect of EP on intracellular mitochondrial membrane potential using JC-1 staining, the number of apoptotic cells using Annexin V-FITC/PI double-staining after HepG2 cells were co-cultured with 0(blank control), 10, 20, 40 µmol·L~(-1) EP for 48 h. The effects of EP at different concentrations on apoptotic morphology were detected using AO/EB staining. The effects of different concentrations of EP on the protein expression of mitochondrial apoptosis pathway-related proteins B cell lymphoma 2(Bcl-2), cytochrome C(Cyt-C), Bcl-2-related X protein(Bax), caspase-3, cleaved caspase-3, caspase-9, and cleaved caspase-9 were examined by using Western blot. The results showed that different concentrations of EP could inhibit the proliferation of hepatocellular carcinoma with concentration-and time-dependent trends. Compared with the blank control group, the ROS level in the EP-treated group increased significantly(P<0.05). The mitochondrial membrane potential decreased significantly(P<0.05). The total apoptosis rate increased significantly(P<0.05). The expression of Bcl-2 protein was significantly down-regulated, and the expression of Cyt-C, Bax, cleaved caspase-9, and cleaved caspase-3 were significantly up-regulated(P<0.05). In summary, EP may inhibit the proliferation of hepatocellular carcinoma by modulating the mitochondria-mediated apoptosis pathway and induce apoptosis.

[Mechanism of ergosterol peroxide on MCF-7 breast cancer cells based on network pharmacology and in vitro experiments].

This study investigated the effects of ergosterol peroxide(EP) on the proliferation and apoptosis of MCF-7 breast cancer cells, explored its possible mechanisms of action, and verified the effects and mechanisms by in vitro experiments. Network pharmaco-logy was used to screen the target proteins of EP and construct target networks and protein-protein interaction(PPI) networks to predict the potential target proteins and related pathways involved in EP anti-breast cancer effects. The MTT assay was performed to measure the inhibitory effect of EP on MCF-7 cell proliferation, and the colony formation assay was used to assess the cell cloning ability. Flow cytometry and laser confocal microscopy were employed to evaluate cell apoptosis, mitochondrial membrane potential and reactive oxygen species(ROS) levels. Western blot analysis was conducted to examine the expression levels of B-cell lymphoma 2(Bcl-2), Bcl-2-associated X protein(Bax), cytochrome C(Cyt C), caspase-7, cleaved caspase-7, phosphatidylinositol 3-kinase(PI3K), and se-rine/threonine kinase B(AKT) in MCF-7 cells treated with EP. The results of network pharmacology prediction yielded 173 common targets between EP and breast cancer; the results of Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment analysis showed that EP treatment for breast cancer mainly affected the signaling pathways such as cancer pathway, PI3K-AKT signaling pathway, cellular senescence signaling pathway, and viral carcinogenesis pathway; and the MTT assay results showed that the viability of MCF-7 cells in the EP group was significantly lower than that in the control group, exhibiting a time-and concentration-dependent trend, and EP can inhibit colony formation of MCF-7 breast cancer cells. Treatment with 10, 20, and 40 µmol·L~(-1) EP for 24 h resulted in a significant increase in the total apoptosis rate of MCF-7 cells, a significant decrease in mitochondrial membrane potential, and a significant increase in ROS levels. In addition, treatment with EP led to an upregulation of Cyt C, Bax, and cleaved caspase-7 protein expression, and a downregulation of p-PI3K, p-AKT, and Bcl-2 protein expression in MCF-7 cells. Studies have shown that EP inhibits MCF-7 breast cancer cell proliferation and reduces colony formation by a mechanism that may be related to the PI3K-AKT pathway mediating the mitochondrial apoptotic pathway.

Intermolecular Electrostatic Interactions in Cytochrome c Protein Monolayer on Montmorillonite Alumosilicate Surface: A Positive Cooperative Effect.

Montmorillonite (MM) crystal nanoplates acquire anticancer properties when coated with the mitochondrial protein cytochrome c (cytC) due to the cancer cells' capability to phagocytize cytC-MM colloid particles. The introduced exogenous cytC initiates apoptosis: an irreversible cascade of biochemical reactions leading to cell death. In the present research, we investigate the organization of the cytC layer on the MM surface by employing physicochemical and computer methods-microelectrophoresis, static, and electric light scattering-to study cytC adsorption on the MM surface, and protein electrostatics and docking to calculate the local electric potential and Gibbs free energy of interacting protein globules. The found protein concentration dependence of the adsorbed cytC quantity is nonlinear, manifesting a positive cooperative effect that emerges when the adsorbed cytC globules occupy more than one-third of the MM surface. Computer analysis reveals that the cooperative effect is caused by the formation of protein associates in which the cytC globules are oriented with oppositely charged surfaces. The formation of dimers and trimers is accompanied by a strong reduction in the electrostatic component of the Gibbs free energy of protein association, while the van der Waals component plays a secondary role.

Recombinant Biogenesis and Analysis of Cytochrome c Species.

Recombinant expression and biogenesis of cytochrome c species is a simple and efficient method for the production of holocytochrome c species, thus presenting an avenue for the study of cytochrome c or the cytochrome c biogenesis pathways responsible for heme attachment. Here, we describe a method for recombinant E. coli production of holocytochrome c utilizing the System I (CcmABCDEFGH) bacterial cytochrome c biogenesis pathway, followed by analysis of cytochrome c species by cell lysis and heme stain.

Cytosolic delivery of cytochrome c conjugates induces apoptosis at nanomolar levels through a caspase-3-dependent pathway.

Cytochrome c (CytC) is conjugated with a small molecule TG6 to give TG6-CytC, which is directly delivered into cytosol, triggering the release of endogenous CytC from mitochondria, and inducing a caspase-3-dependent apoptosis with an IC50 down to 2.4 nM. This work shows an efficient strategy for intracellular protein delivery.

MicroRNA miR-20a-5p targets CYCS to inhibit apoptosis in hepatocellular carcinoma.

Hepatocellular carcinoma is a primary liver cancer, characterised by diverse etiology, late diagnoses, and poor prognosis. Hepatocellular carcinoma is mostly resistant to current treatment options, therefore, identification of more effective druggable therapeutic targets is needed. We found microRNA miR-20a-5p is upregulated during mouse liver tumor progression and in human hepatocellular carcinoma patients. In this study, we elucidated the therapeutic potential of targeting oncogenic miR-20a-5p, in vivo, in a xenograft model and in two transgenic hepatocellular carcinoma mouse models via adeno-associated virus-mediated miR-20a-Tough-Decoy treatment. In vivo knockdown of miR-20a-5p attenuates tumor burden and prolongs survival in the two independent hepatocellular carcinoma mouse models. We identified and validated cytochrome c as a novel target of miR-20a-5p. Cytochrome c plays a key role in initiation of the apoptotic cascade and in the electron transport chain. We show for the first time, that miR-20a modulation affects both these key functions of cytochrome c during HCC development. Our study thus demonstrates the promising 'two birds with one stone' approach of therapeutic in vivo targeting of an oncogenic miRNA, whereby more than one key deregulated cellular process is affected, and unequivocally leads to more effective attenuation of HCC progression and significantly longer overall survival.

Mechanism of the apoptosis of bone marrow erythroblasts in rats under hypobaric hypoxia.

This study aimed to investigate the mechanism of the apoptosis of erythroblasts in rat bone marrow after the exposure to hypobaric hypoxia. Male SD rats were randomly divided into three groups. The hypoxic group was kept in a hypobaric hypoxia chamber at a simulated altitude of 5000 m for 7 and 28 days, respectively. The control group was kept at an altitude of 2260 m. We found that myeloid: erythroid (M:E) ratio was significantly lower after hypoxia exposure and the proportions of polychromatic erythroblasts and orthochromatic erythroblasts significantly increased compared to control group, along with significant increase in the proportion of CD71+ cells and apoptosis rate. The expression levels of caspase-3, Bax, and Cyt-C in CD71+ cells were higher after hypoxia exposure than those in control group, while there was no significant difference in the expression levels of TNFR and Fas. In conclusion, after exposure to hypobaric hypoxia the proliferation of peripheral blood and bone marrow erythroblasts in rats increased, and apoptosis also increased, indicating that bone marrow erythroblasts in rats is regulated by both proliferation and apoptosis, and the mitochondrial pathway is one of the important pathways for apoptosis.

Probing the versatility of cytochrome c by spectroscopic means: A Laudatio on resonance Raman spectroscopy.

Over the last 50 years resonance Raman spectroscopy has become an invaluable tool for the exploration of chromophores in biological macromolecules. Among them, heme proteins and metal complexes have attracted considerable attention. This interest results from the fact that resonance Raman spectroscopy probes the vibrational dynamics of these chromophores without direct interference from the surrounding. However, the indirect influence via through-bond and through-space chromophore-protein interactions can be conveniently probed and analyzed. This review article illustrates this point by focusing on class 1 cytochrome c, a comparatively simple heme protein generally known as electron carrier in mitochondria. The article demonstrates how through selective excitation of resonance Raman active modes information about the ligation, the redox state and the spin state of the heme iron can be obtained from band positions in the Raman spectra. The investigation of intensities and depolarization ratios emerged as tools for the analysis of in-plane and out-of-plane deformations of the heme macrocycle. The article further shows how resonance Raman spectroscopy was used to characterize partially unfolded states of oxidized cytochrome c. Finally, it describes its use for exploring structural changes due to the protein's binding to anionic surfaces like cardiolipin containing membranes.

Human cytochrome C natural variants: Studying the membrane binding properties of G41S and Y48H by fluorescence energy transfer and molecular dynamics.

Cytochrome C (cyt C), the protein involved in oxidative phosphorylation, plays several other crucial roles necessary for both cell life and death. Studying natural variants of cyt C offers the possibility to better characterize the structure-to-function relationship that modulates the different activities of this protein. Naturally mutations in human cyt C (G41S and Y48H) occur in the protein central Ω-loop and cause thrombocytopenia 4. In this study, we have investigated the binding of such variants and of wild type (wt) cyt C to synthetic cardiolipin-containing vesicles. The mutants have a lower propensity in membrane binding, displaying higher dissociation constants with respect to the wt protein. Compressibility measurements reveal that both variants are more flexible than the wt, suggesting that the native central Ω-loop is important for the interaction with membranes. Such hypothesis is supported by molecular dynamics simulations. A minimal distance analysis indicates that in the presence of cardiolipin the central Ω-loop of the mutants is no more in contact with the membrane, as it happens instead in the case of wt cyt C. Such finding might provide a hint for the reduced membrane binding capacity of the variants and their enhanced peroxidase activity in vivo.

Prostate Cancer-Specific Lysine 53 Acetylation of Cytochrome c Drives Metabolic Reprogramming and Protects from Apoptosis in Intact Cells.

Cytochrome c (Cytc) is important for both mitochondrial respiration and apoptosis, both of which are altered in cancer cells that switch to Warburg metabolism and manage to evade apoptosis. We earlier reported that lysine 53 (K53) of Cytc is acetylated in prostate cancer. K53 is conserved in mammals that is known to be essential for binding to cytochrome c oxidase and apoptosis protease activating factor-1 (Apaf-1). Here we report the effects of this acetylation on the main functions of cytochrome c by expressing acetylmimetic K53Q in cytochrome c double knockout cells. Other cytochrome c variants analyzed were wild-type, K53R as a control that maintains the positive charge, and K53I, which is present in some non-mammalian species. Intact cells expressing K53Q cytochrome c showed 49% decreased mitochondrial respiration and a concomitant increase in glycolytic activity (Warburg effect). Furthermore, mitochondrial membrane potential was decreased, correlating with notably reduced basal mitochondrial superoxide levels and decreased cell death upon challenge with H2O2 or staurosporine. To test for markers of cancer aggressiveness and invasiveness, cells were grown in 3D spheroid culture. K53Q cytochrome c-expressing cells showed profoundly increased protrusions compared to WT, suggesting increased invasiveness. We propose that K53 acetylation of cytochrome c is an adaptive response that mediates prostate cancer metabolic reprogramming and evasion of apoptosis, which are two hallmarks of cancer, to better promote tumor survival and metastasis.

Applications of the Newly Developed Force-Field Parameters Uncover a Dynamic Nature of Ω-Loop C in the Lys-Ligated Alkaline Form of Cytochrome c.

Lys-ligated cytochromes make up an emerging family of heme proteins. Density functional theory calculations on the amine/imidazole-ligated c-type ferric heme were employed to develop force-field parameters for molecular dynamics (MD) simulations of structural and dynamic features of these proteins. The new force-field parameters were applied to the alkaline form of yeast iso-1 cytochrome c to rationalize discrepancies resulting from distinct experimental conditions in prior structural studies and to provide insights into the mechanisms of the alkaline transition. Our simulations have revealed the dynamic nature of Ω-loop C in the Lys-ligated protein and its unfolding in the Lys-ligated conformer having this loop in the same position as in the native Met-ligated protein. The proximity of Tyr67 or Tyr74 to the Lys ligand of ferric heme iron suggests a possible mechanism of the backward alkaline transition where a proton donor Tyr assists in Lys dissociation. The developed force-field parameters will be useful in structural and dynamic characterization of other native or engineered Lys-ligated heme proteins.

Pirh2 modulates the mitochondrial function and cytochrome c-mediated neuronal death during Alzheimer's disease.

Pirh2 is an E3 ubiquitin ligase known to regulate the DNA damage responses through ubiquitylation of various participating signaling factors. DNA damage is a key pathological contributor to Alzheimer's disease (AD), therefore, the role of Pirh2 was investigated in streptozotocin and oligomer Aß1-42 induced rodent experimental model of AD. Pirh2 protein abundance increased during AD conditions, and transient silencing of Pirh2 inhibited the disease-specific pathological markers like level of p-Tau, ßamyloid, acetylcholinesterase activity, and neuronal death. Biochemically, Pirh2 silencing significantly attenuated the oxidative stress, depleted mitochondrial membrane potential, cytochrome c translocation from mitochondria to cytosol, and depleted mitochondrial complex-I activity, and ATP level. Pirh2 silencing also inhibited the altered level of VDAC1, hsp75, hexokinase1, t-Bid, caspase-9, and altered level of apoptotic proteins (Bcl-2, Bax). MALDI-TOF/TOF, co-immunoprecipitation, and UbcH13-linked ubiquitylation assay confirmed the interaction of Pirh2 with cytochrome c and the role of Pirh2 in ubiquitylation of cytochrome c, along with Pirh2-dependent altered proteasome activity. Additionally, Pirh2 silencing further inhibited the translocation of mitochondrion-specific endonuclease G and apoptosis-inducing factors to the nucleus and DNA damage. In conclusion, findings suggested the significant implication of Pirh2 in disease pathogenesis, particularly through impaired mitochondrial function, including biochemical alterations, translocation of cytochrome c, endonuclease G and apoptosis-inducing factor, DNA damage, and neuronal apoptosis.

Vallaris solanacea induces mitochondrial mediated apoptosis in HL-60 human promyelocytic leukemia cells.

In the present study, the apoptosis-inducing potential of a chloroform fraction from an alcoholic extract of Vallaris solanacea aerial parts (VS) was examined using human promyelocytic leukemia HL-60 cells. We discovered a concentration and time-dependent decrease in cell growth using MTT assay. Scanning electron micrographs and fluorescence microscopy were used to observe several well-documented morphological and nuclear alterations, such as reduction in cell size, chromatin condensation, fragmentation, and the creation of cell surface blebs. A considerable rise in the Sub-G0 population was revealed by cell cycle analysis. Additionally, a dose-dependent rise in cells positive for Annexin V was observed. DCFH-DA test on VS-treated HL-60 cells showed an increase in endogenous ROS generation of up to 4.3 fold. Additionally, suppression in Bcl-2 levels and increased mitochondrial membrane depolarization in treated cells were also associated with a rise in cytosolic cytochrome-c levels that was consequently followed by the activation of the caspase cascade. Further, the DNA fragmentation assay exhibited a typical ladder formation at 25 µg/ml, which became prominent in a concentration-dependent manner. Our study revealed that VS has apoptosis-inducing potential towards HL-60 cells in vitro and is an effective candidate for further anti-cancer studies.

Engineered polymer nanoparticles as artificial chaperones facilitating the selective refolding of denatured enzymes.

Molecular chaperones assist in protein refolding by selectively binding to proteins in their nonnative states. Despite progress in creating artificial chaperones, these designs often have a limited range of substrates they can work with. In this paper, we present molecularly imprinted flexible polymer nanoparticles (nanoMIPs) designed as customizable biomimetic chaperones. We used model proteins such as cytochrome c, laccase, and lipase to screen polymeric monomers and identify the most effective formulations, offering tunable charge and hydrophobic properties. Utilizing a dispersed phase imprinting approach, we employed magnetic beads modified with destabilized whole-protein as solid-phase templates. This process involves medium exchange facilitated by magnetic pulldowns, resulting in the synthesis of nanoMIPs featuring imprinted sites that effectively mimic chaperone cavities. These nanoMIPs were able to selectively refold denatured enzymes, achieving up to 86.7% recovery of their activity, significantly outperforming control samples. Mechanistic studies confirmed that nanoMIPs preferentially bind denatured rather than native enzymes, mimicking natural chaperone interactions. Multifaceted analyses support the functionality of nanoMIPs, which emulate the protective roles of chaperones by selectively engaging with denatured proteins to inhibit aggregation and facilitate refolding. This approach shows promise for widespread use in protein recovery within biocatalysis and biomedicine.

Cell-penetrating protein-recognizing polymeric nanoparticles through dynamic covalent chemistry and double imprinting.

Molecular recognition of proteins is key to their biological functions and processes such as protein-protein interactions (PPIs). The large binding interface involved and an often relatively flat binding surface make the development of selective protein-binding materials extremely challenging. A general method is reported in this work to construct protein-binding polymeric nanoparticles from cross-linked surfactant micelles. Preparation involves first dynamic covalent chemistry that encodes signature surface lysines on a protein template. A double molecular imprinting procedure fixes the binding groups on the nanoparticle for these lysine groups, meanwhile creating a binding interface complementary to the protein in size, shape, and distribution of acidic groups on the surface. These water-soluble nanoparticles possess excellent specificities for target proteins and sufficient affinities to inhibit natural PPIs such as those between cytochrome c (Cytc) and cytochrome c oxidase (CcO). With the ability to enter cells through a combination of energy-dependent and -independent pathways, they intervene apoptosis by inhibiting the PPI between Cytc and the apoptotic protease activating factor-1 (APAF1). Generality of the preparation and the excellent molecular recognition of the materials have the potential to make them powerful tools to probe protein functions in vitro and in cellulo.

Antifungal activity of human antimicrobial peptides targeting apoptosis in Candida auris.

Introduction. Innovative antifungal therapies are of crucial importance to combat the potentially life-threatening infections linked to the multidrug-resistant fungal pathogen Candida auris. Induction of regulated cell death, apoptosis, could provide an outline for future therapeutics. Human antimicrobial peptides (AMPs), well-known antifungal compounds, have shown the ability to induce apoptosis in pathogenic fungi.Hypothesis/Gap Statement . Although it is known that AMPs possess antifungal activity against C. auris, their ability to induce apoptosis requires further investigations.Aim. This study evaluated the effects of AMPs on the induction of apoptosis in C. auris.Methods. Human neutrophil peptide-1 (HNP-1), human ß-Defensins-3 (hBD-3) and human salivary histatin 5 (His 5) were assessed against two clinical C. auris isolates. Apoptosis hallmarks were examined using FITC-Annexin V/PI double labelling assay and terminal deoxynucleotidyl transferase deoxynucleotidyl transferase nick-end labelling (TUNEL) to detect phosphatidylserine externalization and DNA fragmentation, respectively. Then, several intracellular triggers were studied using JC-10 staining, spectrophotometric assay and 2',7'-dichlorofluorescin diacetate staining to measure the mitochondrial membrane potential, cytochrome-c release and reactive oxygen species (ROS) production, respectively.Results and conclusion. FITC-Annexin V/PI staining and TUNEL analysis revealed that exposure of C. auris cells to HNP-1 and hBD-3 triggered both early and late apoptosis, while His 5 caused significant necrosis. Furthermore, HNP-1 and hBD-3 induced significant mitochondrial membrane depolarization, which resulted in substantial cytochrome c release. In contrast to His 5, which showed minimal mitochondrial depolarization and no cytochrome c release. At last, all peptides significantly increased ROS production, which is related to both types of cell death. Therefore, these peptides represent promising and effective antifungal agents for treating invasive infections caused by multidrug-resistant C. auris.

In-situ and label-free measurement of cytochrome C concentration with a Ti2C-MXene sensitized fiber-optic MZI sensor.

BACKGROUND: The concentration of cytochrome C is demonstrated to be an effective indicator of the microbial corrosion strength of metals. Traditional cytochrome C sensor can detect cytochrome C with a low detection limit, but their use is limited by their high cost, cumbersome operation, and susceptibility to malignant environments. In addition, studies on the monitoring of cytochrome C in the field of microbial corrosion has still not been carried out. Therefore, there is a need for a highly sensitive, selective, low-cost, anti-interference, and stable cytochrome C sensor with online monitoring and remote sensing capabilities for in-situ measurement of microbial corrosion strength. RESULTS: This paper proposed a highly sensitive label-free fiber-optic sensor based on Mach-Zehnder interferometer (MZI) for in-situ measurement of the microbial corrosion marker cytochrome C. Two-dimensional Ti2C-MXene material is uniformly immobilized onto the surface of the sensing area to improve the sensitivity, hydrophilicity, and specific surface area of the sensing area, as well as to facilitate the immobilization of specific sensitive materials. The cytochrome C antibody is modified on the surface of Ti2C-MXene to specifically recognize cytochrome C, whose concentration variation can be measured by monitoring the spectral shift of MZI sensor. Results demonstrate a measurement sensitivity of 1.428 nm/µM for cytochrome C concentrations ranging from 0 to 7.04 µM. The detection limit of the sensor is calculated to be 0.392 µM with remarkable performance, including selectivity, stability, and reliability. Besides, the measurement result of the proposed sensor in real microbial corrosive environment is consistent with that of the ideal environment. SIGNIFICANCE AND NOVELTY: This is the first instance of achieving in-situ and label-free measurement of cytochrome C by using a fiber-optic MZI sensor, which undoubtedly provides a feasible solution for the effective monitoring of microbial metal corrosion in the environment.

Metallophthalocyanine as ideal antibiotics without light: Mechanisms and applications.

The urgent global health problem of antimicrobial resistance (AMR) calls for the discovery of new antibiotics with innovative modes of action while considering the low toxicity to mammalian cells. This paper proposes a novel strategy for designing antibiotics with selective bacterial toxicity by exploiting the positional differences of electron transport chains (ETC) in bacterial and mammalian cells. The focus is on cytochrome c (cyt C) and its maturation system in E. coli. The catalytic oxidative activity of metallophthalocyanine (MPc), which have a distinctive M-N4 structure, is being investigated. Unlike previous applications based on light-activated reactive oxygen species (ROS) generation, this study exploits the ability of MPcs to oxidize Fe2+ to Fe3+ in cyt C and catalyze the formation of disulfide bonds between cysteine residues to interfere with cyt C maturation, disrupt the bacterial respiratory chain and selectively kills bacteria. In contrast, in mammalian cells, these MPcs are located in the lysosomes and cannot access the ETC in the mitochondria, thus achieving selective bacterial toxicity. Two MPcs that showed effective antibacterial activity in a wound infection model were identified. This study provides a valuable reference for the design of novel antibiotics based on M-N4-based metal complex molecules.