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Book ChapterDOI: 10.1016/B978-0-323-42864-4.00003-8

Chapter 3 – Antimicrobial magnetosomes for topical antimicrobial therapy

01 Jan 2016-pp 67-101
Abstract: Biofilms are microbial communities which survive in the hostile environment and are highly resistant to various antimicrobial agents and so very difficult to control, which leads to severity infections. There is an urgent need to eradicate these biofilm-forming bacteria. Nanomedicine is an emerging trend in the medical field, as nanoparticles have been well documented for their antagonistic activity against bacteria, fungi, and viruses and has given rise to new insights in antibiofilm research. Nanomaterials such as silver, gold, aluminum, titanium, iron, and zinc are known to inhibit microbial biofilm. However, they are toxic to the host cells and also to the ecosystem. Magnetosomes produced by magnetotactic bacteria are the iron crystals covered by a lipid membrane called magnetosome membrane. This makes them highly unique compared to the synthetic magnetic nanoparticles. Magnetosomes have received much attention due to their low toxicity, ecofriendly, and cost-efficient properties. Magnetosomes are capable of penetrating the biofilm matrix. Magnetosomes in combination with antibiotics/essential oils will be highly proficient in enhancing the wound-healing property. The carrier property of magnetosomes and antimicrobial activity of drugs/natural compound combination is a successful approach for the prevention of microbial biofilm formation.

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Topics: Biofilm matrix (61%), Magnetosome (57%), Magnetotactic bacteria (55%) ...read more
Citations
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Open accessJournal ArticleDOI: 10.2147/IJN.S180040
Anne-Claire Groo1, Nada Matougui2, Anita Umerska2, Anita Umerska3  +1 moreInstitutions (3)
Abstract: Introduction Resistance to traditional antibiotics is an increasingly serious problem. Antimicrobial peptides (AMPs) have emerged as a new therapeutic class with great potential against infectious diseases, as they are less prone to induce resistance. Nanotechnology-based delivery strategies can improve the efficiency and stability of AMPs, particularly against proteolytic degradation. Lipid nanocapsules (LNCs) are a new generation of biomimetic nanocarriers and were used in this study to deliver peptides. Methods AMP-loaded reverse micelles (RM) were developed and incorpo rated into LNCs by the phase inversion process and the antimicrobial activity of the AMPs-loaded LNC was evaluated by the minimum inhibitory concentration method. We studied the activity of AMP solutions and AMP-loaded LNCs against Gram-positive and Gram-negative bacterial strains and then evaluated the encapsulation of a new cationic AMP called AP138. Finally, we analyzed the effect of enzymatic attack on AP138 and AP138-RM-LNCs after incubation with trypsin. Results AP138 was efficiently encapsulated in the LNCs (encapsulation efficiency = 97.8% at a drug loading of 0.151%), resulting in protection against degradation by proteases and the preservation of antimicrobial activity against Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus. Conclusion This study shows that RM-LNCs are an excellent candidate system to deliver AMPs.

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Topics: Plectasin (54%), Antimicrobial peptides (53%), Nanocarriers (52%) ...read more

20 Citations


Journal ArticleDOI: 10.2217/NNM-2018-0337
Abstract: Aim: Over the last decade, antimicrobial peptides (AMPs) have emerged as a promising alternative for the treatment of various infections The aim of this work is to explore the potential of lipid nanocapsules for the delivery of AMPs Three approaches were compared in terms of encapsulation efficiency, peptide activity and protection against proteases: peptide encapsulation, surface adsorption or covalent attachment of three selected AMPs Results: A potentiation of the antimicrobial activity and a partial protection of the peptides after adsorption were demonstrated compared with native peptides Conversely, encapsulation allowed better peptide stability, correlated with higher encapsulation efficiencies and a preservation of the activity Finally, the covalent attachment strategy turned out to be less conclusive due to peptide inactivation Conclusion: In brief, a lipid nanocapsule-based platform appears suitable to deliver AMPs

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Topics: Antimicrobial peptides (56%), Peptide (50%)

9 Citations


Journal ArticleDOI: 10.1080/17425247.2021.1865306
Abstract: Introduction: Current brain cancer treatments, based on radiotherapy and chemotherapy, are sometimes successful, but they are not free of drawbacks.Areas covered: Traditional methods for the treatment of brain tumors are discussed here with new solutions presented, among which the application of nanotechnology has demonstrated promising results over the past decade. The traditional synthesis of nanostructures, which relies on the use of physicochemical methodologies are discussed, and their associated concerns in terms of environmental and health impact due to the production of toxic by-products, need for toxic catalysts, and their lack of biocompatibility are presented. An overview of the current situation for treating brain tumors using nanotechnological-based approaches is introduced, and some of the latest advances in the application of green nanomaterials (NMs) for the effective targeting of brain tumors are presented.Expert opinion: Green nanotechnology is introduced as a potential solution to toxic NMs through the application of environmentally friendly and cost-effective protocols using living organisms and biomolecules. The current status of this field, such as those involving clinical trials, is included, and the possible limitations of green-NMs and potential ways to avoid those limitations are discussed so that the field can potentially evolve.

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4 Citations


Journal ArticleDOI: 10.1097/00006534-198606000-00087
Abstract: The direct electron microscopic examination of 15 sutures and 15 staples removed from 10 healed surgical wounds showed, on the intradermal portions, consistent colonization by bacteria growing in adherent biofilms. This clearly demonstrable bacterial colonization of biomaterials within the wound tract had not resulted in infection or perceptible inflammation in any of the wounds. These bacterial cells were of several morphotypes, including gram-positive cocci, and all specimens yielded cultures of the autochthonous (native) skin bacterium, Staphylococcus epidermidis. The bacteria within the wound tracts were enveloped by extracellular material that appeared on scanning electron microscopy to be a condensed amorphous residue and on transmission electron microscopy to be a fibrous extracellular matrix. We suggest that this mode of growth, in which the colonizing bacteria are enveloped in a copious exopolysaccharide glycocalix, protects the bacteria from host defense factors and accounts for their persistence on the suture surfaces until they are removed with the sutures.

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1 Citations


Open accessJournal ArticleDOI: 10.1016/J.JDDST.2021.102924
Abstract: Poly(thioether-ester) (PTEe), a polymer synthesized from renewable monomers, is a promising alternative for the encapsulation of antitumor drugs due to its biocompatibility and biodegradability. Therefore, the aim of this study was to synthesize, characterize and evaluate the cytotoxicity of free 4-nitrochalcone (4NC) and 4NC encapsulated in PTEe nanoparticles prepared by thiol-ene miniemulsion polymerization in chronic myeloid leukemia in blast crisis (K562) and acute lymphoblastic leukemia (Jurkat) and peripheral blood mononuclear cells. 4NC was successfully encapsulated in PTEe nanoparticles with an encapsulation efficiency >90%, a mean size of 110 nm, negative surface charge and extended-release profile. Free 4NC and encapsulated in PTEe nanoparticles presented a significant cytotoxicity on K562 and Jurkat cells. Also, 4NC encapsulated in PTEe nanoparticles presented lower damage to peripheral blood mononuclear cells, providing a higher selectivity index than free 4NC for chronic myeloid leukemia in blast crisis (K562) and acute lymphoblastic leukemia (Jurkat). Considering the difficulties involved in leukemia treatment and good results obtained with free 4NC and encapsulated in PTEe nanoparticles, these results can be a new tool for the treatment of neoplastic cells.

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Topics: Jurkat cells (53%), Myeloid leukemia (53%)
References
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Journal ArticleDOI: 10.1016/J.IJFOODMICRO.2004.03.022
Sara A. Burt1Institutions (1)
Abstract: In vitro studies have demonstrated antibacterial activity of essential oils (EOs) against Listeria monocytogenes, Salmonella typhimurium, Escherichia coli O157:H7, Shigella dysenteria, Bacillus cereus and Staphylococcus aureus at levels between 0.2 and 10 microl ml(-1). Gram-negative organisms are slightly less susceptible than gram-positive bacteria. A number of EO components has been identified as effective antibacterials, e.g. carvacrol, thymol, eugenol, perillaldehyde, cinnamaldehyde and cinnamic acid, having minimum inhibitory concentrations (MICs) of 0.05-5 microl ml(-1) in vitro. A higher concentration is needed to achieve the same effect in foods. Studies with fresh meat, meat products, fish, milk, dairy products, vegetables, fruit and cooked rice have shown that the concentration needed to achieve a significant antibacterial effect is around 0.5-20 microl g(-1) in foods and about 0.1-10 microl ml(-1) in solutions for washing fruit and vegetables. EOs comprise a large number of components and it is likely that their mode of action involves several targets in the bacterial cell. The hydrophobicity of EOs enables them to partition in the lipids of the cell membrane and mitochondria, rendering them permeable and leading to leakage of cell contents. Physical conditions that improve the action of EOs are low pH, low temperature and low oxygen levels. Synergism has been observed between carvacrol and its precursor p-cymene and between cinnamaldehyde and eugenol. Synergy between EO components and mild preservation methods has also been observed. Some EO components are legally registered flavourings in the EU and the USA. Undesirable organoleptic effects can be limited by careful selection of EOs according to the type of food.

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Topics: Antibacterial agent (56%), Carvacrol (52%), Thymol (51%) ...read more

8,103 Citations


Journal ArticleDOI: 10.1038/NRMICRO2415
Hans-Curt Flemming1, Jost Wingender1Institutions (1)
Abstract: The microorganisms in biofilms live in a self-produced matrix of hydrated extracellular polymeric substances (EPS) that form their immediate environment. EPS are mainly polysaccharides, proteins, nucleic acids and lipids; they provide the mechanical stability of biofilms, mediate their adhesion to surfaces and form a cohesive, three-dimensional polymer network that interconnects and transiently immobilizes biofilm cells. In addition, the biofilm matrix acts as an external digestive system by keeping extracellular enzymes close to the cells, enabling them to metabolize dissolved, colloidal and solid biopolymers. Here we describe the functions, properties and constituents of the EPS matrix that make biofilms the most successful forms of life on earth.

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5,618 Citations


Journal ArticleDOI: 10.1016/J.JCIS.2004.02.012
Abstract: The antimicrobial activity of silver nanoparticles against E. coli was investigated as a model for Gram-negative bacteria. Bacteriological tests were performed in Luria-Bertani (LB) medium on solid agar plates and in liquid systems supplemented with different concentrations of nanosized silver particles. These particles were shown to be an effective bactericide. Scanning and transmission electron microscopy (SEM and TEM) were used to study the biocidal action of this nanoscale material. The results confirmed that the treated E. coli cells were damaged, showing formation of "pits" in the cell wall of the bacteria, while the silver nanoparticles were found to accumulate in the bacterial membrane. A membrane with such a morphology exhibits a significant increase in permeability, resulting in death of the cell. These nontoxic nanomaterials, which can be prepared in a simple and cost-effective manner, may be suitable for the formulation of new types of bactericidal materials.

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4,790 Citations


Qing Ling Feng1, J. Wu1, Guo-Qiang Chen1, Fuzhai Cui1  +2 moreInstitutions (1)
Abstract: To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), were treated with AgNO(3) and studied using combined electron microscopy and X-ray microanalysis. Similar morphological changes occurred in both E. coli and S. aureus cells after Ag(+) treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed deoxyribonucleic acid (DNA) molecules. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanalysis suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag(+) treatment. The slighter morphological changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag(+) ions.

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3,415 Citations


Open accessJournal ArticleDOI: 10.1128/AEM.02218-06
Sukdeb Pal1, Yu Kyung Tak1, Joon Myong Song1Institutions (1)
Abstract: In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium Escherichia coli, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag+ (in the form of AgNO3). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli.

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Topics: Silver nanoparticle (66%), Antibacterial agent (55%), Nanoparticle (50%)

3,275 Citations


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