Protein Leakage Research Articles

Potential use of plasma‐activated water on Escherichia coli for sterilization: Efficacy and mechanism

AbstractThe plasma‐activated water (PAW) produced by low‐temperature plasma (LTP) was applied to this research because of its safety and no thermal damage. Therefore, the physicochemical properties of PAW, as well as the efficacy and sterilization mechanism of Escherichia coli, were discussed. The PAW (pH 1.27, conductivity 6400 μS/cm) could reduce E. coli by 1.31‐log reduction using LTP at 70 W for 9 min. The results demonstrated that PAW caused DNA and protein leakage with malondialdehyde production. This study may provide a basis for the theoretical research of PAW sterilization. As an effective sterilant, PAW would be a promising alternative strategy for cleaning of E. coli from pipes and filters in food factories.

DsbA-L interacting with catalase in peroxisome improves tubular oxidative damage in diabetic nephropathy

Peroxisomes are metabolically active organelles that are known for exerting oxidative metabolism, but the precise mechanism remains unclear in diabetic nephropathy (DN). Here, we used proteomics to uncover a correlation between the antioxidant protein disulfide-bond A oxidoreductase-like protein (DsbA-L) and peroxisomal function. In vivo, renal tubular injury, oxidative stress, and cell apoptosis in high-fat diet plus streptozotocin (STZ)-induced diabetic mice were significantly increased, and these changes were accompanied by a "ghost" peroxisomal phenotype, which was further aggravated in DsbA-L-deficient diabetic mice. In vitro, the overexpression of DsbA-L in peroxisomes could improve peroxisomal phenotype and function, reduce oxidative stress and cell apoptosis induced by high glucose (HG, 30 mM) and palmitic acid (PA, 250 μM), but this effect was reversed by 3-Amino-1,2,4-triazole (3-AT, a catalase inhibitor). Mechanistically, DsbA-L regulated the activity of catalase by binding to it, thereby reducing peroxisomal leakage and proteasomal degradation of peroxisomal matrix proteins induced by HG and PA. Additionally, the expression of DsbA-L in renal tubules of patients with DN significantly decreased and was positively correlated with peroxisomal function. Taken together, these results highlight an important role of DsbA-L in ameliorating tubular injury in DN by improving peroxisomal function.

Mechanisms of Antioxidant Dipeptides Enhancing Ethanol-Oxidation Cross-Stress Tolerance in Lager Yeast: Roles of the Cell Wall and Membrane.

High concentrations of ethanol could cause intracellular oxidative stress in yeast, which can lead to ethanol-oxidation cross-stress. Antioxidant dipeptides are effective in maintaining cell viability and stress tolerance under ethanol-oxidation cross-stress. In this study, we sought to elucidate how antioxidant dipeptides affect the yeast cell wall and membrane defense systems to enhance stress tolerance. Results showed that antioxidant dipeptide supplementation reduced cell leakage of nucleic acids and proteins by changing cell wall components under ethanol-oxidation cross-stress. Antioxidant dipeptides positively modulated the cell wall integrity pathway and up-regulated the expression of key genes. Antioxidant dipeptides also improved the cell membrane integrity by increasing the proportion of unsaturated fatty acids and regulating the expression of key fatty acid synthesis genes. Moreover, the addition of antioxidant dipeptides significantly (p < 0.05) increased the content of ergosterol. Ala-His (AH) supplementation caused the highest content of ergosterol, with an increase of 23.68 ± 0.01% compared to the control, followed by Phe-Cys (FC) and Thr-Tyr (TY). These results revealed that the improvement of the cell wall and membrane functions of antioxidant dipeptides was responsible for enhancing the ethanol-oxidation cross-stress tolerance of yeast.

Effect of Humidity on the Inactivation of Bacillus Subtilis Spore by Non-thermal Atmospheric Air Plasma

Objective: If a medical device is not properly disinfected, it will pose a potential danger to patients. Spore is an experimental strain to verify the effect of disinfection on medical devices. It has a complex structure and is somewhat resistant to conventional disinfection techniques. Based on the advantages of simple structure and abundant reactive oxygen and nitrogen species (RONS), surface dielectric barrier discharge (SDBD) has been used to deal with inactivate spores, which provided experimental support for the application of sterilization spores in medical devices. Methods: The sterilization efficiency of the plasma was evaluated by calculating the number of viable colonies on Tryptose Soya Agar. RONS including ozone, nitrogen oxides and other reactive species produced in SDBD were measured by ozone analyzer, Fourier infrared spectrometer and chemical probes, respectively. Ultraviolet-visible spectrophotometer was used to determine the concentration of protein and nucleic acid. Results: After 20min of SDBD treatment, the number of inactivated spores could reach more than 4 log at high humidity (&gt;6g/m3), while the spores were hardly inactivated at low humidity (&lt;6g/m3). Ozone production was inhibited with increasing humidity while OH radicals and peroxynitrous acid increased with increasing humidity. The optical density values of protein and nucleic acid released from spores treated with SDBD was detected and a strong correlation was found with the spore inactivation trend. The protein shell and membrane structure of the spores were destroyed by SDBD, and more leakage and destruction of proteins and nucleic acids in the spores were obtained under the high humidity. Conclusion: With the increase of air humidity (from 0.15g/m3 to 70.16g/m3), stable SDBD is obtained showing a typical filamentous discharge pattern. Compared with low humidity, high humidity is more favorable to SDBD inactivation of spores.

Novel expression system based on enhanced permeability of Vibrio natriegens cells induced by D,D- carboxypeptidase overexpression

Vibrio natriegens is a fast-growing, non-pathogenic marine bacterium with promising features for biotechnological applications such as high-level recombinant protein production or fast DNA propagation. A remarkable short generation time (< 10 min), robust proteosynthetic activity and versatile metabolism with abilities to utilise wide range of substrates contribute to its establishment as a future industrial platform for fermentation processes operating with high productivity.D,D-carboxypeptidases are membrane-associated enzymes involved in peptidoglycan biosynthesis and cell wall formation. This study investigates the impact of overexpressed D,D-carboxypeptidases on membrane integrity and the increased leakage of intracellular proteins into the growth medium in V. natriegens. Our findings confirm that co-expression of these enzymes can enhance membrane permeability, thereby facilitating the transport of target proteins into the extracellular environment, without the need for secretion signals, tags, or additional permeabilization methods. Using only a single step IMAC chromatography, we were able to purify AfKatG, MDBP or Taq polymerase in total yields of 117.9 ± 56.0 mg/L, 36.5 ± 12.9 mg/L and 26.5 ± 6.0 mg/L directly from growth medium, respectively. These results demonstrate the feasibility of our V. natriegens based system as a broadly applicable extracellular tag-less recombinant protein producer.

Putrescine (1,4-Diaminobutane) enhances antifungal activity in postharvest mango fruit against Colletotrichum gloeosporioides through direct fungicidal and induced resistance mechanisms

Anthracnose decay caused by Colletotrichum gloeosporioides greatly shortens the shelf life and commercial quality of mango fruit. Putrescine (1,4-Diaminobutane) is involved in modulating plant defense to various environmental stresses. In this research, in vivo and in vitro tests were used to explore the antifungal activity and the underlying mechanism of putrescine against C. gloeosporioides in mango fruit after harvested. In vivo tests suggested that putrescine markedly delayed the occurrence of disease and limited the spots expansion on inoculated mango fruit. Further analysis exhibited that putrescine treatment enhanced disease resistance, along with enhanced activities of chitinase (CHI), β-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate coenzyme A ligase (4CL), polyphenol oxidase (PPO) and the accumulation of lignin, flavonoid, phenolics, and anthocyanin in infected mango fruit. In addition, in vitro tests showed that putrescine exerted strongly antifungal activity against C. gloeosporioides. Putrescine induced the production of reactive oxygen species (ROS) and severe lipid peroxidation damage in C. gloeosporioides mycelia, resulting in the leakage of soluble protein, soluble sugar, nucleic acids, K+ and Ca2+ of C. gloeosporioides mycelia. The mycelium treated with putrescine showed severe deformity and shrinkage, and even cracking. Taken together, putrescine could effectively reduce the incidence rate and severity of anthracnose disease possibly through direct fungicidal effect and indirect induced resistance mechanism, thus showing great potential to be applied to disease control.

Impaired intestinal permeability in patients with multiple sclerosis.

A number of recent studies have shown that the intestinal microbiome, part of the brain-gut axis, is implicated in the pathophysiology of multiple sclerosis. An essential part of this axis, is the intestinal barrier and gastrointestinal disorders with intestinal barrier dysregulation appear to be linked to CNS demyelination, and hence involved in the etiopathogenesis of multiple sclerosis (MS). The aim of this study was to evaluate the integrity of the intestinal barrier in patients with clinically definite multiple sclerosis (CDMS) and clinically isolated syndrome (CIS) using two serum biomarkers, claudin-3 (CLDN3), a component of tight epithelial junctions, and intestinal fatty acid binding protein (I-FABP), a cytosolic protein in enterocytes. Serum levels of CLDN3 in 37 MS patients and 22 controls, and serum levels of I-FABP in 46 MS patients and 51 controls were measured using commercial ELISA kits. Complete laboratory tests excluded the presence of gluten-related disorders in all subjects. Thirty MS patients received either disease-modifying drugs (DMD), immunosuppression (IS) or corticosteroid treatment. CLDN3 levels were only significantly higher in the MS patients treated with DMD or IS compared to the control group (P=0.006). There were no differences in I-FABP serum levels between the groups. Serum CLDN3 levels did not correlate with serum I-FABP levels in CDMS, in CIS patients or controls. In multiple sclerosis patients, the intestinal epithelium may be impaired with increased permeability, but without significant enterocyte damage characterized by intracellular protein leakage. Based on our data, CLDN3 serum levels appear to assess intestinal dysfunction in MS patients but mainly in treated ones.

Antifungal Activity of Cell-Free Supernatants from Lactobacillus pentosus 86 against Alternaria gaisen

Alternaria gaisen is one of the main fungi that cause fruit postharvest diseases due to its wide contamination and toxin production. The application of lactic acid bacteria shows great industrial application as a natural food preserver due to the advantages of being safe and non-toxic. In order to obtain a natural preservative against this fungus, this study aimed to evaluate the effectiveness of cell- free supernatants (CFS) produced by Lactobacillus pentosus 86 as antimicrobials in vitro against A. gaisen. Results indicated that CFS displayed excellent thermostability and enzymatic stabilities with an antifungal activity over 85%. Under thermal (40–100 °C) treatments, different protease solution and acidic conditions (pH 2–4), the antifungal activity of CFS maintained up 80%. However, when the pH reached 6, its antifungal ability completely disappeared. CFS inhibited mycelial growth of A. gaisen by destroying the hyphae membrane, leading to the leakage of nucleic acids and proteins, and hyphae collapsed and shriveled. CFS also changed the spore’s morphology, resulting in cell membrane damage, intracellular leakage, and organelles aggregation. The increase of cell membrane permeability of spores caused a 30% mortality rate. Therefore, the CFS of L. pentosus 86 has the potential for controlling fruit diseases caused by A. gaisen.

Resolvin E1 heals injured cardiomyocytes: Therapeutic implications and H-FABP as a readout for cardiovascular disease & systemic inflammation

The purpose of this study is to investigate heart-fatty acid binding protein (H-FABP) leakage from cardiomyocytes as a quantitative measure of cell membrane damage and to test healing by Resolvin E1 (RVE1) as a potential therapeutic for patients with inflammatory diseases (cardiovascular disease and comorbidities) with high morbidity and mortality. Our quantitative ELISA assays demonstrated H-FABP as a sensitive and reliable biomarker for measuring cardiomyocyte damage induced by lipopolysaccharide (LPS) and healing by RvE1, a specialized pro-resolving mediator (SPM) derived from the Omega-3 fatty acid, eicosapentaenoic acid (EPA), a dietary nutrient that balances inflammation to restore homeostasis. RvE1 reduced leakage of H-FABP by up to 86%, which supports our hypothesis that inflammation as a mechanism of injury can be targeted for therapy. H-FABP as a blood biomarker was tested in 40 patients admitted to Boston Medical Center for respiratory distress, (20 patients with and 20 patients without COVID infection). High levels of H-FABP correlated with clinically diagnosed CVD, diabetes, and end-stage renal disease (ESRD) in both patient groups. The level of H-FABP indicates not only CVD damage but is a valuable measure for patients with increased inflammation disease comorbidities.

Modulation of ultrathin nanosheet structure and nitrogen defects in graphitic carbon nitride for efficient photocatalytic bacterial inactivation

The efficient generation and utilization of ROSs is a key step in determining the achievement of safe drinking water by photocatalytic bacterial inactivation technology. Although graphitic carbon nitride (g-C3N4) serves as a green and promising photocatalyst for water disinfection, insufficient bacterial capturing capacity and serious charge recombination of pristine g-C3N4 extremely restrict its bactericidal activity. Herein, we develop a facile thermal exfoliation and thermal polymerization method to prepare the nitrogen-defective ultrathin g-C3N4 nanosheets (DUCN-500). Our results showed that ultrathin nanosheet structure greatly enhanced bacterial capturing capacity of g-C3N4 to increase the utilization efficiency of ROS, which contributed to the performance of DUCN-500 greatly outperforming bulk g-C3N4. The nitrogen defects increased ROS generation (·O2− and H2O2) by approximately 4.6 times, which was attributed to negative shift of the conduction band potential and rapid separation of charge carriers. The DUCN-500 could rapidly and completely inactivate Escherichia coli and Bacillus subtilis in real sewage under simulated solar irradiation, accompanied by good anti-interference capability and stability. Additionally, bacterial morphology destruction, the loss of antioxidant enzyme activity and the leakage of protein were proven to be the main mechanisms of photocatalytic sterilization. This study offers new insight into the rational design of efficient g-C3N4-based photocatalysts for water disinfection.

Abstract P3207: Mitoregulin Microprotein Influences Mitochondrial Membrane Integrity And Myocardial Ischemia-Reperfusion Injury

Microproteins have emerged as a class of proteins often found to be encoded by misannotated long noncoding RNAs (lncRNAs). We and others discovered that a ubiquitously-expressed “lncRNA” ( LINC00116 ) encodes for a highly-conserved mitochondrial transmembrane microprotein that regulates beta-oxidation; we named this protein Mitoregulin (Mtln). In cells and mice, we found that Mtln increases mitochondrial respiratory efficiencies and Ca 2+ retention capacities, while reducing ROS. To date, the molecular function of Mtln remains unclear, with instances of conflicting data across papers. Recently, we found that mitochondria from Mtln-knockout (KO) mice are susceptible to membrane freeze-damage, leading to matrix protein leak during mitochondrial isolation. This appears not to be a distal downstream consequence of chronic Mtln loss, as we have confirmed these findings in cells after acute Mtln knockdown and in a mouse model of inducible cardiac-specific KO of Mtln (AAV-based CRISPR in aMHC-Cas9 mice; ~90% reduction in Mtln). Furthermore, acute re-expression of Mtln using AAV in Mtln-KO mice rescues the membrane deficit. Transmission electron microscopy revealed that acute Mtln knockdown in cells disrupts mitochondrial cristae integrity / density. Given that we previously found that Mtln strongly binds cardiolipin, we assessed the effects of synthetic Mtln peptide on membrane dynamics in mitochondrial-simulated lipid monolayers and found that Mtln modulates lipid packing and mixing and increases monolayer elasticity. Whether these potential direct effects mediate Mltn’s broad positive impact on mitochondria remain unknown. To further explore a role for Mtln in cardiac disease, we subjected Mtln-KO and AAV-Mtln overexpression mice to myocardial ischemia-reperfusion (IR), given Mtln’s influence on mitochondrial Ca 2+ buffering and ROS. Mtln-KO mice showed significantly worse outcomes (increased infarct size, cardiac dilation, and decreased ejection fraction) at 72 h post-IR, whereas AAV-Mtln mice were protected (decreased infarct size and increased ejection fraction), each compared to control littermates. Overall, this work points to new molecular functions for Mtln and highlights its protective (therapeutic) role in IR injury.

Synergistic effect of electrolyzed water generated by sodium chloride combined with dimethyl dicarbonate for inactivation of Listeria monocytogenes on lettuce.

Electrolyzed water (EW) is recognized as an effective way to control and reduce pathogens in vegetables. However, the disinfection efficacy of EW alone is limited. In this work, the bactericidal activity and biofilm removal capability of EW, generated by adding NaCl to a portable EW generator, were investigated with special reference to Listeria monocytogenes. Furthermore, the impact of EW in combination with dimethyl dicarbonate (DMDC) in reducing the microbial load and improving the overall quality of lettuce during refrigerated storage was evaluated. EW with 0.3% NaCl (SEW) had the highest bactericidal activity against L. monocytogenes. The pathogen treated with SEW exhibited lower superoxide dismutase activity and more leakage of proteins and nucleic acids than in the case of EW. Furthermore, the use of SEW resulted in changes in the cell permeability and morphology of L. monocytogenes. A decrease in adhesion and collapse of the biofilm architecture were also observed, indicating that SEW was more effective for inactivating L. monocytogenes cells compared to EW. For untreated lettuce, the populations of the total plate count and inoculated L. monocytogenes decreased by 2.47 and 2.35 log CFU g-1 , respectively, after the combined SEW/DMDC treatment for 3 min. The use of SEW alone or combined with DMDC did not negatively impact the lettuce color values, titratable acid, ascorbic acid and soluble solids compared to the control group. SEW in combination with DMDC can be used as a novel and potentially effective disinfection strategy for ensuring the safety of vegetable consumption. © 2023 Society of Chemical Industry.

Antibacterial performance of a porous Cu-bearing titanium alloy by laser additive manufacturing.

Porphyromonas gingivalis (P. gingivalis) is the most common species that causes peri-implantitis. It forms an irreversible dense biofilm and causes inflammation. A novel 3D-printed porous TC4-6Cu alloy was fabricated using selective laser melting (SLM) technology for the dental implant, which is anticipated to inhibit biofilm formation. We attempted to investigate the antibacterial ability and antibacterial mechanism of the 3D-printed porous TC4-6Cu alloy against P. gingivalis. This work used scanning electron microscopy (SEM) and laser confocal microscopy (CLSM) to detect the antimicrobial ability of the alloy against sessile P. gingivalis. The results indicated that the 3D-printed porous TC4-6Cu alloy could cause bacterial fragmentation and deformation. Plate antimicrobial counting experiments showed that the antibacterial rates of the alloy against adherent bacteria and planktonic bacteria after 24h were 98.05% and 73.92%, respectively. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Cu2+ were tested to appraise the antibacterial property of the alloy against planktonic P. gingivalis. The relationship between the antibacterial mechanism of the alloy with oxidative stress was evaluated through ROS fluorescence intensity and protein leakage concentration. The results revealed that the alloy significantly eliminated adherent bacteria and inhibited biofilm formation. Moreover, 3D-printed porous TC4-6Cu alloy demonstrated significant bactericidal ability by inducing the production of reactive oxygen species (ROS), which could result in protein leakage from the bacterial cell membrane. This research may open a new perspective on the development and biomedical applications for dental implantation.

Selective antibacterial activity of Citrus Medica limonum essential oil against Escherichia coli K99 and Lactobacillus acidophilus and its antibacterial mechanism

Escherichia coli K99 (E. coli K99) is one of the important pathogenic bacteria in calf production causing massive loss every year, and Lactobacillus acidophilus (L. acidophilus) is an important probiotic in the gut. Essential oils in Citrus have selective antibacterial activity and the capacity to be an alternative to antibiotics. In this study, we analyzed the chemical component of Citrus Medica Limonum essential oil (LEO) and d-limonene, β-pinene, and γ-terpinene by GC-MS, then compared their selective antibacterial activities against E. coli K99 and L. acidophilus and investigated the antibacterial mechanism of LEO. The principal component of LEO, d-limonene, β-pinene, and γ-terpinene were d-limonene (47.19%), d-limonene (77.94%), β-pinene (93.52%) and γ-terpinene (89.27%) respectively. The MIC and MBC of LEO against E. coli K99 were 5 mg/mL and 10 mg/mL, while against L. acidophilus were 80 mg/mL and 160 mg/mL, which showed its best selective antibacterial activity among four EOs. LEO damaged the cell membrane structure, leading to the leakage of intracellular proteins and nucleic acids of both bacteria. Moreover, LEO improved the cell-surface hydrophobicity of both bacteria and decreased the soluble protein content of E. coli K99. In conclusion, LEO has selective antibacterial activity and the potential to be applied in calf feed.

ZnO-Doped Metal-Organic Frameworks Nanoparticles: Antibacterial Activity and Mechanisms.

Metal-Organic Frameworks (MOFs) offer new ideas for the design of antibacterial materials because of their antibacterial properties, high porosity and specific surface area, low toxicity and good biocompatibility compared with other nanomaterials. Herein, a novel antimicrobial nanomaterial, MIL-101(Fe)@ZnO, has been synthesized by hydrothermal synthesis and characterized by FTIR, UV-vis, ICP-OES, XRD, SEM, EDS and BET to show that the zinc ions are doped into the crystal lattice of MIL-101(Fe) to form a Fe-Zn bimetallic structure. MIL-101(Fe)@ZnO was found to be effective against a wide range of antibacterial materials including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Acinetobacter junii and Staphylococcus epidermidis. It has a significant antibacterial effect, weak cytotoxicity, high safety performance and good biocompatibility. Meanwhile, MIL-101(Fe)@ZnO was able to achieve antibacterial effects by causing cells to produce ROS, disrupting the cell membrane structure, and causing protein leakage and lipid preoxidation mechanisms. In conclusion, MIL-101(Fe)@ZnO is an easy-to-prepare antimicrobial nanomaterial with broad-spectrum bactericidal activity and low toxicity.

Sertoli Hücresi ve Kan-Testis Bariyeri

The Sertoli cell is a critical somatic cell that initiates the development of testicular morphology and determines important parameters for spermatogenic function. The blood-testis barrier, also known as the Sertoli cell barrier and one of the tightest tissue barriers in the mammalian body, is an immunological barrier to separate post meiotic germ cell antigens from the systemic circulation. Additionally, creating a unique microenvironment for the development of spermatocytes that exceed into the adluminal compartment from the leptotene stage. It restricts the passage of substances such as paracrine factors, electrolytes, hormones, water, and biological molecules to the apical part of the seminiferous tubule. It separates spermatogenic cells from toxic and drug-containing environmentally harmful substances, hormones, and biomolecules in the systemic circulation. This nearly impenetrable barrier prevents proteins, including antibodies, from reaching the spermatogenic cells. It also prevents protein leakage from developing spermatogenic cells and forming an immune response. This review explains Sertoli's functional properties, the testis barrier's molecular structure, the substances involved in the barrier dynamics, and their importance in realizing spermatogenesis.

Stringent Response Factor DksA Contributes to Fatty Acid Degradation Function to Influence Cell Membrane Stability and Polymyxin B Resistance of Yersinia enterocolitica.

DksA is a proteobacterial regulator that binds directly to the secondary channel of RNA polymerase with (p)ppGpp and is responsible for various bacterial physiological activities. While (p)ppGpp is known to be involved in the regulation and response of fatty acid metabolism pathways in many foodborne pathogens, the role of DksA in this process has yet to be clarified. This study aimed to characterize the function of DksA on fatty acid metabolism and cell membrane structure in Yersinia enterocolitica. Therefore, comparison analysis of gene expression, growth conditions, and membrane permeabilization among the wide-type (WT), DksA-deficient mutant (YEND), and the complemented strain was carried out. It confirmed that deletion of DksA led to a more than four-fold decrease in the expression of fatty acid degradation genes, including fadADEIJ. Additionally, YEND exhibited a smaller growth gap compared to the WT strain at low temperatures, indicating that DksA is not required for the growth of Y. enterocolitica in cold environments. Given that polymyxin B is a cationic antimicrobial peptide that targets the cell membrane, the roles of DksA under polymyxin B exposure were also characterized. It was found that DksA positively regulates the integrity of the inner and outer membranes of Y. enterocolitica under polymyxin B, preventing the leakage of intracellular nucleic acids and proteins and ultimately reducing the sensitivity of Y. enterocolitica to polymyxin B. Taken together, this study provides insights into the functions of DksA and paves the way for novel fungicide development.

EFFECT OF ESSENTIAL OIL FROM Feroniella lucida (SCHEFF.) SWINGLE FRUIT ON Staphylococcus aureus

Staphylococcus aureus is a bacterium commonly found on human skin and mucus membrane linked to the severity of the chronic inflammatory skin disease, and a contaminant in food. This study presented the effect of essential oil extracted from Feroniella lucida (Scheff.) Swingle fruit for its antibacterial activity against two strains of Staphylococcus aureus, ATCC 29213 and TISTR 517; and its chemical composition. The hydro-distillated essential oil yield from the peel was approximately 0.72% (v/w, fresh weight), compared to the average yield of 0.10% (v/w) from the plant leaves. The major components of the peel oil were decyl acetate (56.20% of the total GC-MC peak area), decanal (22.49%), and dodecyl acetate (6.81%). The oil could inhibit both strains, but the ATCC 29213 was more sensitive than TISTR 517 with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 0.125 and 2.0, and 0.5 and 16.0 mg/mL, respectively. For the mode of action performed for the strain ATCC 29213, the essential oil had a significant effect to inhibit the bacterium growth within 2 h, and caused protein, potassium ion, and adenosine triphosphates (ATP) leakages, but it had no effect on the leakage of nucleic acids. Under scanning electron microscope (SEM) observation of the essential oil effect on the bacterial cell morphology, the crease and furrow of ATCC 29213 cells were detected. These results encourage further application of the oil from the edible fruit as anti-Staphylococcus aureus to develop skin care products as well as to be used in food industry.

An oxygen self-supplied CuO2@g-C3N4 heterojunction endows photodynamic antibacterial performance of scaffold

Graphite carbon nitride (g-C3N4) was regarded as a promising photodynamic antibacterial material due to its desirable bandgap and favorable visible light absorption. However, its photodynamic antibacterial effect was weakened by too rapid recombination of electron-hole and hypoxic environment of infection site. Herein, an oxygen self-supplied heterojunction was constructed via in-situ growing CuO2 on g-C3N4 (CuO2@g-C3N4). For the heterojunction, on the one hand, it could response to the weak alkaline of infected site to decompose to CuO@g-C3N4, where CuO could form a built-in electric field with g-C3N4 to promote the electron-hole separation. On the other hand, it could produce oxygen in the decomposition process, which achieved oxygen self-supply for photodynamic reaction. Subsequently, the heterojunction was introduced into poly-para-dioxane (PPDO) scaffold fabricated by laser additive manufacturing. The photoluminescence results confirmed that the electron-hole separation efficiency was significantly improved. The release kinetics results indicated that the scaffold could continuously release oxygen. As a consequence, the reactive oxygen species (ROS) generation ability of the scaffold was increased by approximately tenfold. The generated ROS effectively killed bacteria by disrupting membrane structure, triggering protein leakage and depleting glutathione. Eventually, the scaffold exhibited an antibacterial rate of 89.8% and 90.5% against S. aureus and E. coli, respectively.

An ultrasound-activated heterojunction as ROS generator given scaffolds sonodynamic antibacterial effect

Potassium niobate (KNbO3) with favorable biocompatibility presented a great potential in the sonodynamic therapy of implant-related infection due to its superior piezoelectric performance. However, the rapid electron-hole pair recombination weakened its sonodynamic therapy effect. In this work, Au@KNbO3 heterojunctions were synthesized by depositing Au nanoparticles on KNbO3, and then mixed with poly-l-lactic acid (PLLA) powder to prepare scaffold by laser additive manufacturing. Herein, Au with lower Fermi level acted as electron trap to capture the ultrasonic-excited electrons from KNbO3. Subsequently, Au formed Schottky barrier with KNbO3 to prevent electrons backflow. As a result, the electron-hole was expected to be separated. EIS curves indicated that Au@KNbO3 presented a smaller arc radius than that of KNbO3, confirming the electron-hole separation efficiency of Au@KNbO3 was enhanced. Following that, ROS generation ability of the scaffold was significantly strengthened. Antibacterial tests revealed that the generated ROS could not only trigger protein leakage by disrupting bacterial cell membranes, but also deplete glutathione to weaken the antioxidant defense of bacteria. As a consequence, the scaffold exhibited excellent antibacterial abilities of 92% and 90% against S. aureus and E. coli, respectively. Collectively, this work provided a promising countermeasure to fight the implant-related infection.