| 1. |
- Rahimi, Shadi, 1982, et al.
(författare)
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Automated Prediction of Bacterial Exclusion Areas on SEM Images of Graphene–Polymer Composites
- 2023
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Ingår i: Nanomaterials. - 2079-4991. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- To counter the rising threat of bacterial infections in the post-antibiotic age, intensive efforts are invested in engineering new materials with antibacterial properties. The key bottleneck in this initiative is the speed of evaluation of the antibacterial potential of new materials. To overcome this, we developed an automated pipeline for the prediction of antibacterial potential based on scanning electron microscopy images of engineered surfaces. We developed polymer composites containing graphite-oriented nanoplatelets (GNPs). The key property that the algorithm needs to consider is the density of sharp exposed edges of GNPs that kill bacteria on contact. The surface area of these sharp exposed edges of GNPs, accessible to bacteria, needs to be inferior to the diameter of a typical bacterial cell. To test this assumption, we prepared several composites with variable distribution of exposed edges of GNP. For each of them, the percentage of bacterial exclusion area was predicted by our algorithm and validated experimentally by measuring the loss of viability of the opportunistic pathogen Staphylococcus epidermidis. We observed a remarkable linear correlation between predicted bacterial exclusion area and measured loss of viability (R2 = 0.95). The algorithm parameters we used are not generally applicable to any antibacterial surface. For each surface, key mechanistic parameters must be defined for successful prediction.
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| 2. |
- Mokkapati, Venkata Raghavendra Subrahmanya Sar, 1981, et al.
(författare)
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Bacterial response to graphene oxide and reduced graphene oxide integrated in agar plates
- 2018
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 5:11
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Tidskriftsartikel (refereegranskat)abstract
- There are contradictory reports in the literature regarding the anti-bacterial activity of graphene, graphene oxide (GO) and reduced graphene oxide (rGO). This controversy is mostly due to variations in key parameters of the reported experiments, like: type of substrate, form of graphene, number of layers, type of solvent and most importantly, type of bacteria. Here, we present experimental data related to bacterial response to GO and rGO integrated in solid agar-based nutrient plates-a standard set-up for bacterial growth that is widely used by microbiologists. Bacillus subtilis and Pseudomonas aeruginosa strains were used for testing bacterial growth. We observed that plate-integrated rGO showed strong anti-bacterial activity against both bacterial species. By contrast, plate-integrated GO was harmless to both bacteria. These results reinforce the notion that the response of bacteria depends critically on the type of graphene material used and can vary dramatically from one bacterial strain to another, depending on bacterial physiology.
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| 3. |
- Pandit, Santosh, 1987, et al.
(författare)
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Vertically Aligned Graphene Coating is Bactericidal and Prevents the Formation of Bacterial Biofilms
- 2018
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 5:7
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Tidskriftsartikel (refereegranskat)abstract
- The key first step in developing bacterial infections related to implants and medical devices is the attachment of planktonic bacterial cells, and subsequent formation of biofilms. Herein, it is reported that graphene, a 2D carbon-based material, can be effectively used to prevent bacterial attachment. The key parameter for this effect is the orientation of graphene with respect to the coated surface. Chemical vapor deposition (CVD) graphene, deposited horizontally on the surface, exhibits no antibacterial effect. By contrast, an array of graphene flakes grown perpendicularly to the surface by a plasma-enhanced CVD (PECVD) process prevent biofilm formation. Electron microscopy reveals that the exposed edges of vertically aligned graphene flakes penetrate the bacterial membrane and drain the cytosolic content. Bacteria are not able to develop resistance to this killing mechanism during multiple exposures. By keeping the height of the vertical graphene coating between 60 and 100 nm, the coating is able to effectively kill bacteria, while being completely harmless to mammalian cells.
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| 4. |
- Ruan, Hengzhi, 1995, et al.
(författare)
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Biomimetic Antibacterial Gelatin Hydrogels with Multifunctional Properties for Biomedical Applications
- 2023
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Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 15:47, s. 54249-54249–54265
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Tidskriftsartikel (refereegranskat)abstract
- A facile novel approach of introducing dopamine and [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide via dopamine-triggered in situ synthesis into gelatin hydrogels in the presence of ZnSO4 is presented in this study. Remarkably, the resulting hydrogels showed 99.99 and 100% antibacterial efficiency against Gram-positive and Gram-negative bacteria, respectively, making them the highest performing surfaces in their class. Furthermore, the hydrogels showed adhesive properties, self-healing ability, antifreeze properties, electrical conductivity, fatigue resistance, and mechanical stability from −100 to 80 °C. The added multifunctional performance overcomes several disadvantages of gelatin-based hydrogels such as poor mechanical properties and limited thermostability. Overall, the newly developed hydrogels show significant potential for numerous biomedical applications, such as wearable monitoring sensors and antibacterial coatings.
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| 5. |
- Ruan, Hengzhi, 1995, et al.
(författare)
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Polysaccharide-based antibacterial coating technologies
- 2023
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Ingår i: Acta Biomaterialia. - 1878-7568 .- 1742-7061. ; 168, s. 42-77
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Forskningsöversikt (refereegranskat)abstract
- To tackle antimicrobial resistance, a global threat identified by the United Nations, is a common cause of healthcare-associated infections (HAI) and is responsible for significant costs on healthcare systems, a substantial amount of research has been devoted to developing polysaccharide-based strategies that prevent bacterial attachment and biofilm formation on surfaces. Polysaccharides are essential building blocks for life and an abundant renewable resource that have attracted much attention due to their intrinsic remarkable biological potential antibacterial activities. If converted into efficient antibacterial coatings that could be applied to a broad range of surfaces and applications, polysaccharide-based coatings could have a significant potential global impact. However, the ultimate success of polysaccharide-based antibacterial materials will be determined by their potential for use in manufacturing processes that are scalable, versatile, and affordable. Therefore, in this review we focus on recent advances in polysaccharide-based antibacterial coatings from the perspective of fabrication methods. We first provide an overview of strategies for designing polysaccharide-based antimicrobial formulations and methods to assess the antibacterial properties of coatings. Recent advances on manufacturing polysaccharide-based coatings using some of the most common polysaccharides and fabrication methods are then detailed, followed by a critical comparative overview of associated challenges and opportunities for future developments. Statement of significance: Our review presents a timely perspective by being the first review in the field to focus on advances on polysaccharide-based antibacterial coatings from the perspective of fabrication methods along with an overview of strategies for designing polysaccharide-based antimicrobial formulations, methods to assess the antibacterial properties of coatings as well as a critical comparative overview of associated challenges and opportunities for future developments. Meanwhile this work is specifically targeted at an audience focused on featuring critical information and guidelines for developing polysaccharide-based coatings. Including such a complementary work in the journal could lead to further developments on polysaccharide antibacterial applications.
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| 6. |
- Gummesson, Bertil, 1977, et al.
(författare)
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Increased RNA polymerase availability directs resources towards growth at the expense of maintenance. : RNAP overproduction
- 2009
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Ingår i: The EMBO journal. - : Wiley. - 1460-2075 .- 0261-4189. ; 28:15, s. 2209-2219
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Tidskriftsartikel (refereegranskat)abstract
- Nutritionally induced changes in RNA polymerase availability have been hypothesized to be an evolutionary primeval mechanism for regulation of gene expression and several contrasting models have been proposed to explain how such 'passive' regulation might occur. We demonstrate here that ectopically elevating Escherichia coli RNA polymerase (Esigma(70)) levels causes an increased expression and promoter occupancy of ribosomal genes at the expense of stress-defense genes and amino acid biosynthetic operons. Phenotypically, cells overproducing Esigma(70) favours growth and reproduction at the expense of motility and damage protection; a response reminiscent of cells with no or diminished levels of the alarmone guanosine tetraphosphate (ppGpp). Consistently, we show that cells lacking ppGpp displayed markedly elevated levels of free Esigma(70) compared with wild-type cells and that the repression of ribosomal RNA expression and reduced growth rate of mutants with constitutively elevated levels of ppGpp can be suppressed by overproducing Esigma(70). We conclude that ppGpp modulates the levels of free Esigma(70) and that this is an integral part of the alarmone's means of regulating a trade-off between growth and maintenance.
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| 7. |
- Lovmar, Martin, 1975-
(författare)
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Macrolide Antibiotics in Bacterial Protein Synthesis
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Macrolides are a large group of clinically relevant antibiotics that inhibit protein synthesis by binding to the large ribosomal subunit in the peptide exit tunnel, close to the peptidyl transferase center (PTC). We have shown that the peptide length of the resulting peptidyl-tRNA drop-off products is proportional to the distance between the PTC and the respective macrolide in the tunnel. This indicates that macrolides act by sterically blocking the nascent peptide exit path.A substantial amount of read-through into full-length product was observed for some macrolides and depends on the relation between the dissociation rate constants for peptidyl-tRNA and the macrolide, respectively. The dissociation rate constant for josamycin is 60 times lower than the dissociation rate constant for erythromycin, which explains why no read-through is seen for josamycin in contrast to erythromycin.Macrolides do not compete with binding of ternary complexes, hence they are non-competitive inhibitors. However, the text-book description is not valid for macrolide antibiotics, and we show that this is due to the equilibrium assumption generally used to describe non-competitive inhibitors. Our results suggest that a more thorough mechanistic investigation is required to classify inhibitors than what has been proposed previously.Further, we have examined the phenomenon of peptide mediated resistance to macrolides. Our results show that expression of a resistance peptide increases the dissociation rate constant for erythromycin.In addition, we have examined the accuracy of protein synthesis on three different levels: (i) How do the three initiation factors accomplish fast and accurate initiation of protein synthesis, (ii) how does proof-reading work on the isoleucyl-tRNA synthetase, and (iii) what is the accuracy in the tRNA selection and how is it accomplished? Our data propose a change of the view on all these mechanisms.In conclusion this thesis presents new results on protein synthesis, macrolide antibiotics and macrolide resistance.
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