Effects of ferulic acid combined with light irradiation on deoxynivalenol and its production in Fusarium graminearum.

This study aimed to investigate the effects of ferulic acid (FA), a natural phenolic phytochemical, in combination with light irradiation at three wavelengths (365, 385 and 405 nm) on the concentration and toxicity of deoxynivalenol (DON), a mycotoxin produced by Fusarium graminearum. Moreover, this study examined the influence of the combination treatment on DON production in the cultured fungus. FA activated by light at a peak wavelength of 365 nm exhibited the most effective decrease in DON concentration of the tested wavelengths; a residual DON ratio of 0.23 at 24 h exposure was observed, compared with the initial concentration. The reduction in DON using 365-nm light was dependent on the concentration of FA, with a good correlation (r2 = 0.979) between the rate constants of DON decrease and FA concentration, which was confirmed by a pseudo-first-order kinetics analysis of the photoreaction with different FA concentrations (50-400 mg/L) for 3 h. The viability of HepG2 cells increased by 56.7% following in vitro treatment with a mixture containing the photoproducts obtained after treatment with 20 mg/L DON and 200 mg/L FA under 365-nm irradiation for 6 h. These results suggested that the photoreaction of FA under 365-nm irradiation induces the detoxification of DON through degradation or modification of DON. The antifungal effects of the combination (FA and 365-nm light) on F. graminearum were investigated. Conidia treated with the combination did not show additive or synergistic inhibition of fungal biomass and DON production in 7-day cultivated fungal samples compared with samples after single treatment. However, successive treatment, composed of 90 min irradiation at 365 nm and then treatment with 200 mg/L FA for 90 min in the dark, suppressed fungal growth and DON yield to 70% and 25% of the untreated sample level, respectively. This photo-technology involving the two treatment methods of 365-nm irradiation and FA addition as a food-grade phenolic acid in combination or successively, can aid in developing alternative approaches to eliminate fungal contaminants in the fields of environmental water and agriculture. However, further research is required to explore the underlying mechanisms of DON decontamination and its biosynthesis in F. graminearum.

Phosphoramide-Based Metal-Organic Frameworks for Effective Gas Adsorption.

Cost-effective and facile synthetic routes to organic ligands, along with porous materials that exhibit exceptional gas-storage properties, promise significant industrial applications. Here, a two-step synthesis of novel organophosphorus ligands without metal catalysts is reported. These ligands serve as versatile linkers for the construction of metal-organic frameworks (MOFs) incorporating various metal ions, including zinc and copper. One of the zinc-based MOFs demonstrates remarkable gas-storage properties, with a hydrogen (H2) capacity exceeding 2.5 wt% at 77 K and 100 kPa as well as a carbon dioxide (CO2) capacity exceeding 20 wt% at 298 K and 100 kPa. Furthermore, this zinc-based MOF can be synthesized through a solvothermal process on the gram scale that yields high-quality single crystals.

Alkoxy-Functionalized Hydroxamate/Zinc Metal-Organic Frameworks and the Effects of Substituents and Acid Addition on Their Structures.

Single crystals of alkoxy-functionalized hydroxamate/zinc metal-organic frameworks (MOFs) were obtained by fixating the hydroxamate moiety via intramolecular hydrogen bonding. The resulting MOF structures depend on the steric demand of the alkoxy groups, whereby the incorporation of bulky isopropyl groups affords porous hydroxamate/zinc MOFs. The topological structures of the isopropyl-substituted MOFs could be controlled by adding acid.

Zn-Based Metal-Organic Frameworks Using Triptycene Hexacarboxylate Ligands: Synthesis, Structure, and Gas-Sorption Properties.

Invited for the cover of this issue is the group of Koh Sugamata, Mao Minoura, and co-workers at Rikkyo University. The image depicts triptycene-based metal-organic frameworks with honeycomb structures that collect carbon dioxide and hydrogen, in an analogy to bees collecting honey in their honeycombs. Read the full text of the article at 10.1002/chem.202302080.

Zn-Based Metal-Organic Frameworks Using Triptycene Hexacarboxylate Ligands: Synthesis, Structure, and Gas-Sorption Properties.

A series of metal-organic frameworks (MOFs) based on zinc ions and two triptycene ligands of different size have been synthesized under solvothermal conditions. Structural analyses revealed that they are isostructural 3D-network MOFs. The high porosity and thermal stability of these MOFs can be attributed to the highly rigid triptycene-based ligands. Their BET specific surface areas depend on the size of the triptycene ligands. In contrast to these surface-area data, the H2 and CO2 adsorption of these MOFs is larger for MOFs with small pores. Consequently, we introduced functional groups to the bridge-head position of the triptycene ligands and investigated their effect on the gas-sorption properties. The results unveiled the role of the functional groups in the specific CO2 binding via an induced interaction between adsorbates and the functional groups. Excellent H2 and CO2 properties in these MOFs were achieved in the absence of open metal sites.

Controlling the Flexibility of Carbazole-Based Metal-Organic Frameworks by Substituent Effects.

We have developed highly porous Cu-based metal-organic frameworks (MOFs) using carbazole-type linkers. The novel topological structure of these MOFs was revealed by single-crystal X-ray diffraction analysis. Molecular adsorption/desorption experiments indicated that these MOFs are flexible and change their structure upon adsorption/desorption of organic solvents and gas molecules. These MOFs exhibit unprecedented properties that allow controlling their flexibility by adding a functional group onto the central benzene ring of the organic ligand. For example, the introduction of electron-donating substituents increases the robustness of the resulting MOFs. These MOFs also exhibit flexibility-dependent differences in gas-adsorption and -separation performance. Thus, this study represents the first example of controlling the flexibility of MOFs with the same topological structure via the substituent effect of functional groups introduced into the organic ligand.

Porcine embryo development and inactivation of microorganisms after ultraviolet-C irradiation at 228 nm.

It is important to prevent contamination inside the incubator as a method of preventing microbial infections during the embryo culture. In the present study, we examined the effects of ultraviolet-C (UV-C) irradiation, used for microorganism inactivation, on embryo development and the growth of bacteria, including Escherichia coli and Staphylococcus aureus, and the fungus Cladosporium cladosporioides. In the embryo irradiation experiment, we examined the effects of the plastic lid of the culture dish, irradiation distances (10, 20, and 25 cm), and different irradiation wavelengths (228 and 260 nm) during embryo culture for 7 days on the development and quality of porcine in vitro-fertilized embryos. None of the embryos cultured in dishes without plastic lids developed into blastocysts after irradiation with 228 nm UV-C. When porcine embryos were cultured in a culture dish with lids, the 228 nm UV-C irradiation decreased blastocyst formation rates of the embryos but not their quality, irrespective of the UV-C irradiation distance. Moreover, irradiation with 260 nm UV-C, even with plastic lids, had more detrimental effects on embryo development than irradiation with 228 nm UV-C. Investigation of the inactivating effects of UV-C irradiation at 228 nm and 260 nm on the growth of the bacteria and fungus showed that 260 nm UV-C reduced the viability to a greater extent than 228 nm UV-C. Moreover, the disinfection efficacy for the bacteria increased when the irradiation duration increased and the distance decreased. In conclusion, porcine embryos can develop into blastocysts without loss of quality even after continuous long-duration irradiation (7 days) with 228 nm UV-C, which can inactivate the growth of bacteria and the tested fungus; however, the development rate of the embryo is reduced.

Remote Bactericidal Effect of Anatase TiO2 Photocatalytic Nanoparticles Annealed with Low-Temperature O2 Plasma.

The remote bactericidal effect of TiO2 photocatalyst, i.e., the bactericidal effect away from the photocatalyst, was successfully achieved using a humidified airflow. The TiO2 photocatalyst used was anatase-type TiO2 nanoparticles (NPs) annealed with a low-temperature O2 plasma. For comparison, anatase-type TiO2 NPs annealed in the air were used. The bacteria, Bacillus subtilis, were placed away from the TiO2 NPs. The plasma-assisted-annealed TiO2 NPs significantly inactivated 99% of the bacterial cells in 5 h, whereas the pristine and air-annealed TiO2 NPs inactivated 88-90% of the bacterial cells. The remote bactericidal effect of plasmaassisted-annealed TiO2 NPs would be attributed to a larger amount of H2O2 molecules traveled by the airflow from the TiO2 NPs. The molecules were generated by chemically reacting more photoexcited carriers on the TiO2 surface with H2O and O2 in the airflow. These photoexcited carriers originated from more oxygen-based species adsorbed and more oxygen vacancies introduced on the TiO2 surface by the plasma-assisted-annealing.

Effects of Violet-Blue Light-Emitting Diode on Controlling Bacterial Contamination in Boiled Young Sardine.

The aim of this study was to evaluate bacterial decontamination of boiled young sardine by treatment with violet-blue light followed by cooling storage of the irradiated boiled sardine. Viable cell count in the samples was evaluated after irradiation with four types of violet-blue light-emitting diodes (LEDs; peak wavelength at 405, 412, 421 or 455 nm) and subsequent cooling storage for two days. LED (405 nm) exhibited bactericidal and growth suppression effects. The irradiation gave a 47% bactericidal rate in comparison with no irradiation samples (control) and the two-day storage suppressed the increase in cell counts to 24%, while the rate of increase was 545% for the control. Integrated viability (IV) based on growth delay analysis was estimated after irradiation of four isolates from boiled sardine with 405 nm light. The irradiation caused growth delay against all isolates, resulting in smaller IV values for three isolates compared to those viabilities estimated from colony forming units. Exposure (405 nm) at 432 J/cm2 fluence resulted in a decrease in water content, resulting in an increase in salinity of the samples. This study demonstrated the advantages of light emitting a narrow violet region as a non-thermal disinfection technology in the processing and storage of boiled sardines.

Ultraviolet Light-Emitting Diode (UV-LED) Sterilization of Citrus Bacterial Canker Disease Targeted for Effective Decontamination of Citrus Sudachi Fruit.

A kind of citrus fruit with special flavor, Citrus sudachi harvested in Japan, are exported to various countries. However, the Citrus sudachi needs to be sterilized using aqueous solution of sodium hypochlorite because there is a possibility of the adhesion of citrus bacterial canker (CBC) which is not found in Europe. Due to the sterilization with time-consuming work, a more effective decontamination technique is required. A decontamination method using ultraviolet (UV) light irradiation is thus anticipated. Especially, the use of light emitting diodes (LEDs) wi UV light has many advantages in terms of energy consumption, lifetime, and compactness； although an appropriate method is yet to be established. In this study, we evaluate the fundamental effectiveness of UV-LED decontamination on the basis of the bactericidal ability on CBC in petri dishes, using six kinds of UV-LEDs (265, 280, 285, 300, 310, and 365 nm) . For each irradiation, the resultant bactericidal abilities (BAs) were evaluated precisely taking into account the differences in their optical absorptions. In addition, BAs per unit photon number were also estimated, as a fundamental wavelength-dependence of BA. As a result, the effectiveness of UV-LED irradiation with relatively short wavelengths was demonstrated clearly.

Antimicrobial action of phenolic acids combined with violet 405-nm light for disinfecting pathogenic and spoilage fungi.

The aim of this study is to investigate the fungicidal spectrum of six phenolic-cinnamic and -benzoic acid derivatives using four fungi, Aspergillus niger, Cladosporium cladosporioides, Trichophyton mentagrophytes and Candida albicans, in a photocombination system with violet 405-nm light. This is the first study to examine the fungicidal mechanism involving oxidative damage using the conidium of A. niger, as well as an assessment of cellular function and chemical characteristics. The results of the screening assay indicated that ferulic acid (FA) and vanillic acid (VA), which possess 4-hydroxyl and 3-methoxy groups in their phenolic acid structures, produced synergistic activity with 405-nm light irradiation. FA and VA (5.0 mM) significantly decreased the viability of A. niger by 2.4 to 2.6-logs under 90-min irradiation. The synergistic effects were attenuated by the addition of the radical scavenger dimethyl sulfoxide. Generation of reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals, were confirmed in the phenolic acid solutions tested after irradiation with colorimetric and electron spin resonance analyses. Adsorption of FA and VA to conidia was greater than other tested phenolic acids, and produced 1.55- and 1.85-fold elevation of intracellular ROS levels, as determined using an oxidant-sensitive probe with flow cytometry analysis. However, cell wall or membrane damage was not the main mechanism by which the combination-induced fungal death was mediated. Intracellular ATP was drastically diminished (5% of control levels) following combined treatment with FA and light exposure, even under a condition that produced negligible decreases in viability, thereby resulting in pronounced growth delay. These results suggest that the first stage in the photofungicidal mechanism is oxidative damage to mitochondria or the cellular catabolism system associated with ATP synthesis, which is a result of the photoreaction of phenolic acids adsorbed and internalized by conidia. This photo-technology in combination with food-grade phenolic acids can aid in developing alternative approaches for disinfection of pathogenic and spoilage fungi in the fields of agriculture, food processing and medical care.

Antifungal action of the combination of ferulic acid and ultraviolet-A irradiation against Saccharomyces cerevisiae.

AIMS: To examine the antifungal action of photocombination treatment with ferulic acid (FA) and ultraviolet-A (UV-A) light (wavelength, 365 nm) by investigating associated changes in cellular functions of Saccharomyces cerevisiae. METHODS AND RESULTS: When pre-incubation of yeast cells with FA was extended from 0.5 to 10 min, its photofungicidal activity increased. Flow cytometry analysis of stained live and dead cells revealed that 10-min UV-A exposure combined with FA (1 mg ml-1 ) induced a ~99.9% decrease in cell viability although maintaining cell membrane integrity when compared with pre-exposure samples. When morphological and biochemical analysis were performed, treated cells exhibited an intact cell surface and oxidative DNA damage similar to control cells. Photocombination treatment induced cellular proteins oxidation, as shown by 2.3-fold increasing in immunostaining levels of ~49-kDa carbonylated proteins compared with pre-irradiation samples. Pyruvate kinase 1 (PK1) was identified by proteomics analysis as a candidate protein whose levels was affected by photocombination treatment. Moreover, intracellular ATP levels decreased following FA treatment both in darkness and with UV-A irradiation, thus suggesting a possible FA-induced delay in cell growth. CONCLUSIONS: FA functions within the cytoplasmic membrane; addition of UV-A exposure induces increased oxidative modifications of cytosolic proteins such as PK1, which functions in ATP generation, without causing detectable genotoxicity, thus triggering inactivation of yeast cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Microbial contamination is a serious problem that diminishes the quality of fruits and vegetables. Combining light exposure with food-grade phenolic acids such as FA is a promising disinfection technology for applications in agriculture and food processing. However, the mode of photofungicidal action of FA with UV-A light remains unclear. This study is the first to elucidate the mechanism using S. cerevisiae. Moreover, proteomics analyses identified a specific cytosolic protein, PK1, which is oxidatively modified by photocombination treatment.

Therapeutic Effect and Mechanism of Action of Low-molecular-weight Whey Protein Capable of Activating Macrophages in Bovine Mastitis.

BACKGROUND/AIM: Bovine mastitis is caused by the invasion and propagation of pathogenic microorganisms into the udder and mammary gland tissues of cattle. In this study, the therapeutic effect of a low-molecular-weight whey protein (LMW-WP) on bovine mastitis was evaluated. MATERIALS AND METHODS: LMW-WP was orally, intraperitoneally, and vaginally administered to bovine with mastitis. The number of somatic cells in milk was measured 24 h before the administration of LMW-WP. The effect of LMW-WP on cytokine production was measured with a microarray that evaluates the expression of cytokines. RESULTS: In the group that received 1,000 mg intraperitoneally, the somatic cell count was reduced to less than 400,000 at the shipment standard value in three of the four udders, indicating 75% efficacy. The group that received 1,000 mg by vaginal administration showed 67% efficacy. It was confirmed that LMW-WP increased the production of cytokines such as IL-5, IL-6, IL-9, IL-12, MCP-1, and VEGF in mouse macrophage cells, but it did not show any antibacterial activity. CONCLUSION: LMW-WP may be an effective therapeutic agent for bovine mastitis.

Inkjet Printing-Based Immobilization Method for a Single-Step and Homogeneous Competitive Immunoassay in Microchannel Arrays.

In this study, we report an inkjet printing-based method for the immobilization of different reactive analytical reagents on a single microchannel for a single-step and homogeneous solution-based competitive immunoassay. The immunoassay microdevice is composed of a poly(dimethylsiloxane) microchannel that is patterned using inkjet printing by two types of reactive reagents as dissolvable spots, namely, antibody-immobilized graphene oxide and a fluorescently labeled antigen. Since nanoliter-sized droplets of the reagents could be accurately and position-selectively spotted on the microchannel, different reactive reagents were simultaneously immobilized onto the same microchannel, which was difficult to achieve in previously reported capillary-based single-step bioassay devices. In the present study, the positions of the reagent spots and amount of reagent matrix were investigated to demonstrate the stable and reproducible immobilization and a uniform dissolution. Finally, a preliminary application to a single-step immunoassay of C-reactive protein was demonstrated as a proof of concept.

Bactericidal action of ferulic acid with ultraviolet-A light irradiation.

The bactericidal activity of ferulic acid (FA) against various microorganisms was remarkably enhanced by ultraviolet-A (UV-A) irradiation (wavelength, 365 nm). However, the bactericidal mechanism in the photo-combination system has not been evaluated. In the present study, this combined treatment was characterized by investigating associated changes in cellular functions of Escherichia coli, including assessments of respiratory activity, lipid peroxidation, membrane permeability, and damage to DNA and the cell surface. FA adsorbed onto and was incorporated into bacterial membranes, and the affinity resulted in decreased respiratory activity and enhanced lipid peroxidation in the cytoplasmic membrane with low-fluence (1.0 J/cm2) UV-A irradiation. Flow cytometry analysis revealed that additional exposure (8 J/cm2) combined with FA (1 mg/mL) induced increased cell permeability, yielding a 4.8-log decrease in the viable cell count. Morphologically, the treated cells exhibited a bacterial membrane dysfunction, producing many vesicles on the cell surface. However, despite this effect on the cell surface, plasmid DNA transformed into FA-treated E. coli maintained supercoiled integrity with negligible DNA oxidation. Our data strongly suggested that FA functions inside and outside the bacterial membrane; UV-A exposure in the presence of FA then causes increased oxidative modification and subsequent disruption of the bacterial membrane, without causing detectable genotoxicity.

Fast and Single-step Fluorescence-based Competitive Bioassay Microdevice Combined PDMS Microchannel Arrays Separately Immobilizing Graphene Oxide-Analyte Conjugates and Fluorescently-labelled Receptor Proteins.

In this study, a fast and easy-to-use capillary-type microdevice for competitive bioassay is proposed. The device is composed of polydimethylsiloxane (PDMS) microchannel arrays that separately immobilize polyethylene glycol (PEG) coating, which contained graphene oxide (GO)-analyte conjugates and fluorescently-labelled receptor proteins. The working principle of the device involved the spontaneous dissolution of the PEG coating, subsequent mixing and reaction with analyte to give fluorescence response, triggered by the capillary action-mediated introduction of a sample solution. For principle verification, a competitive biotin assay was successfully demonstrated within 20 s in a single-step operation by detecting the change in fluorescence via microscopy.

Identification and Characterization of a 25 kDa Protein That Is Indispensable for the Efficient Saccharification of Eisenia bicyclis in the Digestive Fluid of Aplysia kurodai.

The digestive fluid of the sea hare Aplysia kurodai can liberate approximately 2.5 mg of glucose from 10 mg of dried Eisenia bicyclis powder. Although laminaran, a major storage polysaccharide in E. bicyclis, is easily digested to glucose by the synergistic action of the 110 and 210 kDa A. kurodai ß-glucosidases (BGLs), glucose is not liberated from E. bicyclis by direct incubation with these BGLs. To clarify this discrepancy, we searched for an Eisenia hydrolysis enhancing protein (EHEP) in the digestive fluid of A. kurodai. A novel 25 kDa protein that enhances E. bicyclis saccharification by ß-glucosidases was purified to a homogeneous state from the digestive fluid of A. kurodai, and its cDNA was cloned from total cDNAs reverse-transcribed from hepatopancreas total RNA. The E. bicyclis extract strongly inhibited BGLs, suggesting some compound within this brown alga functioned as a feeding deterrent. However, when E. bicyclis was incubated with BGLs in the presence of EHEP, glucose production was markedly increased. As E. bicyclis is rich in phlorotannin, which are only found in brown algae, our study suggested that these compounds are the main BGL inhibitors in E. bicyclis extract. EHEP protects BGLs from phlorotannin inhibition by binding to phlorotannins and forming an insoluble complex with phloroglucinol and phlorotannins. These findings indicated that EHEP plays a key role in the saccharification of brown seaweeds containing phlorotannins in the digestive fluid of A. kurodai. This is the first report of EHEP as a phlorotannin-binding protein that protects BGLs from inhibition.

Development of a single-step immunoassay microdevice based on a graphene oxide-containing hydrogel possessing fluorescence quenching and size separation functions.

An immunoassay, which is an indispensable analytical method both in biological research and in medical fields was successfully integrated into a "single-step" by developing a microdevice composed of a graphene oxide (GO)-containing hydrogel and a poly (dimethylsiloxane) (PDMS) microchannel array with a polyethylene glycol (PEG) coating containing a fluorescently-labelled antibody. Here we used 2-hydroxyethylmethacrylate (HEMA) as a monomer that is easily, and homogeneously, mixed with GO to synthesize the hydrogel. The fluorescence quenching and size separation functions were then optimized by controlling the ratios of HEMA and GO. Free fluorescently-labelled antibody was successfully separated from the immunoreaction mixture by the hydrogel network structure, and the fluorescence was subsequently quenched by GO. In comparison to the previously reported immunoassay system using GO, the present system achieved a very high fluorescence resonance energy transfer (FRET) efficiency (∼90%), due to the use of direct adsorption of the fluorescently-labelled antibody to the GO surface; in contrast, the former reported method relied on indirect adsorption of the fluorescently-labelled antibody via immunocomplex formation at the GO surface. Finally, the single-step immunoassay microdevice was made by combining the developed hydrogel and the PDMS microchannel with a coating containing the fluorescently-labelled antibody, and successfully applied for the single-step analysis of IgM levels in diluted human serum by simple introduction of the sample via capillary action.

Fast and single-step immunoassay based on fluorescence quenching within a square glass capillary immobilizing graphene oxide-antibody conjugate and fluorescently labelled antibody.

A single-step, easy-to-use, and fast capillary-type immunoassay device composed of a polyethylene glycol (PEG) coating containing two kinds of antibody-reagents, including an antibody-graphene oxide conjugate and fluorescently labelled antibody, was developed in this study. The working principle involved the spontaneous dissolution of the PEG coating, diffusion of reagents, and subsequent immunoreaction, triggered by the capillary action-mediated introduction of a sample solution. In a sample solution containing the target antigen, two types of antibody reagents form a sandwich-type antigen-antibody complex and fluorescence quenching takes place via fluorescence resonance energy transfer between the labelled fluorescent molecules and graphene oxide. Antigen concentration can be measured based on the decrease in fluorescence intensity. An antigen concentration-dependent response was obtained for the model target protein sample (human IgG, 0.2-10 µg mL(-1)). The present method can shorten the reaction time to within 1 min (approximately 40 s), while conventional methods using the same reagents require reaction times of approximately 20 min because of the large reaction scale. The proposed method is one of the fastest immunoassays ever reported. Finally, the present device was used to measure human IgG in diluted serum samples to demonstrate that this method can be used for fast medical diagnosis.

Synergistic Photobactericidal Activity Based on Ultraviolet-A Irradiation and Ferulic Acid Derivatives.

Ultraviolet-A (UV-A)-mediated bactericidal activity was enhanced by combined treatment with trans-ferulic acid (trans-FA, compound 1) or its derivatives. Derivative compounds 4 and 10 contain a phenyl group or an l-tyrosine HCl tert-butyl ester, respectively, linked to the carboxyl group of trans-FA. Of the three compounds, 10 exhibited the highest synergistic activity in a photobactericidal assay based on treating Escherichia coli with a derivative compound and UV-A irradiation (wavelength 350-385 nm). Inactivation of viable cells at a 4.9 J cm(-2) UV-A fluence increased from 1.90 to 5.19 logs in the presence of 10 (100 µm); a 4.95-log inactivation was achieved with 10 (5 µm) and a 7.4 J cm(-2) UV-A fluence. Addition of antioxidants significantly suppressed photosynergistic bactericidal activity, suggesting that reactive oxygen species (ROS) are involved in the combined bactericidal mechanism. Flow cytometry revealed that combined treatment with UV-A and compound 10, which showed the highest photobactericidal activity, generates an excess of oxidative radicals in bacterial cells. The bactericidal activity of compound 10 may be due to electrostatic interaction between the molecule's cationic moiety and the cell surface, followed by amplification of ROS generation in the cells.