| 1. |
- Chen, Yanyan, 1990, et al.
(författare)
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Graphene nanospikes exert bactericidal effect through mechanical damage and oxidative stress
- 2024
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Ingår i: Carbon. - 0008-6223. ; 218
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Tidskriftsartikel (refereegranskat)abstract
- Microbial contamination of biomedical surfaces is an important clinical challenge, driving the development of new antibacterial materials. Nanoprotrusions on the wing surface of some insects have intrinsic antibacterial and antifouling properties, which inspires fabrication of biomimetic nanopatterns on medical devices. Herein, we report a broad-spectrum bactericidal surface consisting of graphene nanospikes synthesized by plasma-enhanced chemical vapor deposition. Similar coatings have been reported before, but the killing mechanism and main parameters for efficiency of such coatings have not been clarified. We investigated the correlation of anti-biofilm efficiency of graphene nanospikes to their major physicochemical parameters. While height and thickness of nanospikes did not directly correlate with bactericidal effects, edge/defect density showed linear correlation with lethality for both Gram-negative and Gram-positive bacteria. We further demonstrated that the killing mechanism is synergistic, depending on physical rupture of bacterial membranes as well as considerable oxidative damage to the cells. Of note, for the first time, we quantify the level of oxidative stress induced by graphene nanospikes in two bacterial species using genetically encoded biosensors. Our work provides a fundamental understanding of the impact of various parameters of graphene nanostructures on the bactericidal efficiency, enabling rational design of graphene-based bactericidal surfaces.
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| 2. |
- Ghai, Viney, 1989, et al.
(författare)
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Achieving Long-Range Arbitrary Uniform Alignment of Nanostructures in Magnetic Fields
- 2024
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Ingår i: Advanced Functional Materials. - 1616-3028 .- 1616-301X. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- For magnetic field orientation of nonstructures to become a viable method to create high performance multifunctional nanocomposites, it is of paramount importance to develop a method that is easy to implement and that can induce long-range uniform nanostructural alignment. To overcome this challenge, inspired by low field nuclear magnetic resonance (NMR) technology, a highly uniform, high field strength, and compact magnetic-field nanostructure orientation methodology is presented for polymeric nanocomposites using a Halbach array, for the first time. Potential new advances are showcased for applications of graphene polymer composites by considering their electro-thermal and antibacterial properties in highly oriented orthogonal morphologies. The high level of anisotropy induced in the graphene nanocomposites studied stands out through: 1) up to four decades higher electrical conductivities recorded in comparison to their randomly oriented counterparts, at concentrations where the latter show minimal improvements compared to the unfilled polymer; 2) over 1200% improvement in thermal conductivity, 3) antibacterial surfaces at field benchmark levels with lower filler content and with the added versatility of arbitrary orientation of the nanofillers. Overall, the new method and variations thereof can open up new horizons for tailoring nanostructure and performance for virtually all major nanocomposite applications based on graphene and other types of fillers.
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| 3. |
- More, Pragati Rajendra, et al.
(författare)
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Antibacterial applications of biologically synthesized Pichia pastoris silver nanoparticles
- 2024
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Ingår i: Heliyon. - 2405-8440. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: This article highlights the biological synthesis of silver nanoparticles (AgNPs) with their characteristic analysis, and it focuses on the application of synthesized NPs against multidrug resistance (MDR) bacteria. A cytotoxicity study was performed to assess the biocompatibility. Methods: Silver nanoparticle (AgNPs) formation was confirmed by different characterization methods such as UV–Vis spectrophotometer, Dynamic light scattering (DLS)- Zeta, Fourier transform infrared (FTIR), and Transmission electron microscope (TEM). The antimicrobial activity of the AgNPs was checked against various bacterial strains of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Klebsiella pneumonia (K. pneumonia) by disc diffusion, minimum inhibition concentration test (MIC), and kinetic studies. The cytotoxicity of NPs against the Vero cell line was studied by cytotoxic assay. Results: The primary analysis of the formation of nanoparticles (NPs) was made by UV–Vis spectrophotometric analysis at 400 nm. At the same time, the efficient capping checked by FTIR shows the presence of a functional group at different wavelengths 3284, 1641,1573,1388,1288, and 1068 cm−1. At the same time, the transmission electron microscopic analysis (TEM) and DLS show that the shape and size of the synthesized NPs possess an average size of around ∼10–30 nm with spherical morphology. Further, the zeta potential confirmed the stability of the NPs. While the yield of NPs formation from silver salt was determined by an online yield calculator with the EDX analysis results. Synthesized NPs showed bactericidal effects against all the selected MDR pathogens with nontoxic effects against mammalian cells. Conclusion: Our findings indicate the remarkable antimicrobial activity of the biologically synthesized AgNPs, which can be an antimicrobial agent against multi-drug-resistant bacteria.
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| 4. |
- Shi, Lei, 1981, et al.
(författare)
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Connection between protein-tyrosine kinase inhibition and coping with oxidative stress in Bacillus subtilis
- 2024
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 121:25
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Tidskriftsartikel (refereegranskat)abstract
- In bacteria, attenuation of protein-tyrosine phosphorylation occurs during oxidative stress. The main described mechanism behind this effect is the H2O2-triggered conversion of bacterial phospho-tyrosines to protein-bound 3,4-dihydroxyphenylalanine. This disrupts the bacterial tyrosine phosphorylation-based signaling network, which alters the bacterial polysaccharide biosynthesis. Herein, we report an alternative mechanism, in which oxidative stress leads to a direct inhibition of bacterial protein-tyrosine kinases (BY-kinases). We show that DefA, a minor peptide deformylase, inhibits the activity of BY-kinase PtkA when Bacillus subtilis is exposed to oxidative stress. High levels of PtkA activity are known to destabilize B. subtilis pellicle formation, which leads to higher sensitivity to oxidative stress. Interaction with DefA inhibits both PtkA autophosphorylation and phosphorylation of its substrate Ugd, which is involved in exopolysaccharide formation. Inactivation of defA drastically reduces the capacity of B. subtilis to cope with oxidative stress, but it does not affect the major oxidative stress regulons PerR, OhrR, and Spx, indicating that PtkA inhibition is the main pathway for DefA involvement in this stress response. Structural analysis identified DefA residues Asn95, Tyr150, and Glu152 as essential for interaction with PtkA. Inhibition of PtkA depends also on the presence of a C-terminal α-helix of DefA, which resembles PtkA-interacting motifs from known PtkA activators, TkmA, SalA, and MinD. Loss of either the key interacting residues or the inhibitory helix of DefA abolishes inhibition of PtkA in vitro and impairs postoxidative stress recovery in vivo, confirming the involvement of these structural features in the proposed mechanism.
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| 5. |
- Zhang, Jian, 1989, et al.
(författare)
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Polydopamine Modified Carbon Nitride and PAMAM Assembled Electrochemical Immunosensor for Detection of Indole-3-Acetic Acid
- 2024
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Ingår i: ChemElectroChem. - 2196-0216. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Indole-3-acetic acid (IAA) assumes a pivotal role as a phytohormone of utmost importance, intricately orchestrating the nuanced processes associated with the growth and developmental trajectories of botanical organisms. In this study, we have designed and fabricated a label-free electrochemical impedance immunosensor for the precise detection of IAA. The detection strategy predominantly relied upon polydopamine modified carbon nitride (C3N4) nanosheets (PCN) and polyamidoamine (PAMAM) dendrimer. Through the modification with PCN and PAMAM, the electrode has increased the active area and enhanced the immobilization capacity of antibodies for IAA. The immunosensor‘s ability to capture IAA was significantly improved by enhancing the immunoreaction between the antibody and antigen. This enhancement led to an increased response in the electrochemical behavior of the Fe(CN)63−/4− redox probe. The impedance immunosensor developed exhibits remarkable sensitivity, exceptional selectivity, and consistent performance in the detection of IAA. This assay method, with the potential to replace antibodies, could offer an alternative approach for detecting various phytohormones.
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