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Journal ArticleDOI

Rapid preparation and antimicrobial activity of polyurea coatings with RE-Doped nano-ZnO.

22 Oct 2021-Microbial Biotechnology (John Wiley & Sons, Ltd)-pp 1
TL;DR: In this paper, an extremely rapid method to introduce rare-earth doping nano-ZnO in polyamines for the preparation of the anti-microbial polyurea coatings was proposed.
Abstract: The recent COVID-19 virus has led to a rising interest in antimicrobial and antiviral coatings for frequently touched surfaces in public and healthcare settings. Such coatings may have the ability to kill a variety of microorganisms and bio-structures and reduce the risk of virus transmission. This paper proposes an extremely rapid method to introduce rare-earth doping nano-ZnO in polyamines for the preparation of the anti-microbial polyurea coatings. The nano-ZnO is prepared by wet chemical method, and the RE-doped nano-ZnO was obtained by mixing nano ZnO and RE-dopants with an appropriate amount of nitric acid. This rapidly fabricated polyurea coating can effectively reduce bacteria from enriching on the surface. Comparing with pure nano-ZnO group, all the polyurea coatings with four different rare-earth elements (La, Ce, Pr and Gd) doped nano-ZnO. The La-doped nano-ZnO formula group indicates the highest bactericidal rate over 85% to Escherichia coli (E. coli) and Pseudomonas aeruginosa (Pseudomonas). Followed by Ce/ZnO, the bactericidal rate may still remain as high as 83% at room temperature after 25-min UV-exposure. It is believed that the RE-doping process may greatly improve the photocatalytic response to UV light as well as environmental temperature due to its thermal catalytic enhancement. Through the surface characterizations and bioassays, the coatings have a durably high bactericidal rate even after repeated usage. As polyurea coating itself has high mechanical strength and adhesive force with most substrate materials without peel-off found, this rapid preparation method will also provide good prospects in practical applications.
Citations
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Journal ArticleDOI
01 Jul 2022-Polymers
TL;DR: In this article , extrinsic and intrinsic mechanisms are reviewed to address the efficiency of the self-healing process and formulation optimization and strategic improvement to ensure selfhealing within a shorter period of time with acceptable recovery of mechanical strength are also discussed.
Abstract: Self-healing polymers are categorized as smart materials that are capable of surface protection and prevention of structural failure. Polyurethane/polyurea, as one of the representative coatings, has also attracted attention for industrial applications. Compared with polyurethane, polyurea coating, with a similar formation process, provides higher tensile strength and requires shorter curing time. In this paper, extrinsic and intrinsic mechanisms are reviewed to address the efficiency of the self-healing process. Moreover, formulation optimization and strategic improvement to ensure self-healing within a shorter period of time with acceptable recovery of mechanical strength are also discussed. The choice and ratio of diisocyanates, as well as the choice of chain extender, are believed to have a crucial effect on the acceleration of the self-healing process and enhance self-healing efficiency during the preparation of polyurea coatings.

6 citations

Journal ArticleDOI
TL;DR: In this article , a Ce/La-doped nano-TiO 2 polyurea coatings are fabricated for emergency leak sealing, which are able to form high mechanical strength coating surfaces within seconds.
Abstract: Abstract Industrial piping structures often suffer from corrosion caused by biofouling or chemical etching, which can cause immediate structural failure. Polyurea coatings, which are fabricated for emergency leak sealing, are able to form high mechanical strength coating surfaces within seconds. After its further modification via Ce/La-doped TiO 2 , the polyurea coating will indicate an increment in mechanical strength, chemical durability, and reduction of microbial attachment. Due to the adsorption by the Ce/La-doped TiO 2 and generation of reactive oxygen species (ROS), E. coli and Pseudomonas may lose their living conditions during the progress, and planktonic bacteria cells are prevented from enriching on the surface. The Ce/La‐dopants can also improve the original photocatalytic response of nano-TiO 2 to UV light and environmental temperature. These Ce/La-doped TiO 2 polyurea coatings illustrate an immediate application for emergency leak sealing purposes without any production interruption and it may prolong the time intervals for the maintenance service as well.

6 citations

Journal ArticleDOI
TL;DR: In this paper , a fire-retardant polyurea coating for industrial applications is proposed, where the aromatic diamine and aliphatic diisocyanate are believed to have a synergistic effect in improving flame properties.
Abstract: Abstract Polymeric materials and composites are well suited to support structures in marine conditions due to their corrosion resistance. However, their low glass transition temperature makes them vulnerable to softening at high temperatures. Hence, fire retardancy is a key aspect if these materials are selected to ensure stiffness under flammable conditions. In this paper, a fire-retardant polyurea coating for industrial applications is proposed. The aromatic diamine and aliphatic diisocyanate are believed to have a synergistic effect in improving flame properties. Moreover, various combinations of flame-retardant additives with aromatic and aliphatic-based polyurea are mixed to further improve fire-retardancy. Through the characterizations of their glass transition temperature and delay in the ignition, it indicates that the combination of Talc and melamine polyphosphate may provide an outstanding enhancement for the Titania-polyurea coating, and such enhancement may improve its original tensile and compression strength, and surface hardness as well.

5 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the phytochemical contents of plant extracts obtained from Epilobium parviflorum Schreb and their potential antibacterial activity and found that polyphenols and flavonoids were present in all plant extracts.
Abstract: The present study was carried out to develop an experimental endodontic irrigant solution based on plant extracts obtained from Epilobium parviflorum Schreb. that largely replenish the properties of the usual antiseptics used in dentistry. Background: This study investigated the phytochemical contents of plant extracts obtained from Epilobium parviflorum Schreb. and their potential antibacterial activity. Methods: Identification and quantification of biologically active compounds were made by UV field photo spectrometry, adapting the Folin-Ciocalteu test method. Antibacterial activity was tested on pathological bacterial cultures collected from tooth with endodontic infections using a modified Kirby-Bauer diffuse metric method. Results: Polyphenols and flavonoids were present in all plant extracts; the hydroalcoholic extract had the highest amount of polyphenols—17.44 pyrogallol equivalent (Eq Pir)/mL and flavonoids—3.13 quercetin equivalent (Eq Qr)/mL. Plant extracts had antibacterial activity among the tested bacterial species with the following inhibition diameter: White Staphylococcus (16.5 mm), Streptococcus mitis (25 mm), Streptococcus sanguis (27 mm), Enterococcus faecalis (10 mm). Conclusions: All plant extracts contain polyphenols and flavonoids; the antibacterial activity was in direct ratio with the amount of the bioactive compounds.

3 citations

Journal ArticleDOI
27 Aug 2022-Polymers
TL;DR: In this article , an optimal formulation for fabrication of polyurea with a high self-healing efficiency was found by changing the composition of the components chosen for formulation of Polyurea.
Abstract: Self-healing materials, especially self-healing polyurea/polyurethane, to replace traditional coating has been of increasing interest in the past decade. The frequency of regular maintenance work can also be reduced as the coating is capable of forming bonds at ruptured sites. This reduces the cost of maintenance and the risk involved in workers engaging in maintenance work. The extremely short curing time of polyurea coating could potentially outweigh the cost due to its short down time. With a high self-healing efficiency, self-healing polyurea could be the ultimate choice of protective coating. This report aims to find the optimum formulation for fabrication of polyurea with a high self-healing efficiency. This is conducted by changing the composition of the components chosen for formulation of polyurea. The choice of isocyanate and amine is varied to explore its impact on chain mobility and microphase separation, which are important factors affecting self-healing efficiency. A series of characterizations, including ATR-FTIR, DSC, optical microscope and mechanical tester, is used to analyze the factors affecting the self-healing efficiency of fabricated polyurea and to eventually determine the best formulation. The ideal formulation of toluene 2,4 diisocyanate-amine (TDI-P1000) polyurea managed to achieve a self-healing of 42%. Further studies could be done to include multiple healing mechanisms after different area of polyurea to boost its self-healing efficiency after repeated healing.

3 citations

References
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Journal ArticleDOI
TL;DR: The functions, properties and constituents of the EPS matrix that make biofilms the most successful forms of life on earth are described.
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.

7,041 citations

Journal ArticleDOI
TL;DR: This review will discuss the mechanisms identified as playing a role in biofilm resistance to disinfectants, as well as novel anti-biofilm strategies that have recently been explored.
Abstract: A biofilm can be defined as a community of microorganisms adhering to a surface and surrounded by a complex matrix of extrapolymeric substances. It is now generally accepted that the biofilm growth mode induces microbial resistance to disinfection that can lead to substantial economic and health concerns. Although the precise origin of such resistance remains unclear, different studies have shown that it is a multifactorial process involving the spatial organization of the biofilm. This review will discuss the mechanisms identified as playing a role in biofilm resistance to disinfectants, as well as novel anti-biofilm strategies that have recently been explored.

695 citations

Journal ArticleDOI
TL;DR: Evidence suggests that these mechanisms of resistance have been developed as a general stress response of biofilms that enables the cells in the biofilm to respond to all of the changes in the environment that they may encounter.
Abstract: Bacterial biofilms are the basis of many persistent diseases. The persistence of these infections is primarily attributed to the increased antibiotic resistance exhibited by the cells within the biofilms. This resistance is multifactorial; there are multiple mechanisms of resistance that act together in order to provide an increased overall level of resistance to the biofilm. These mechanisms are based on the function of wild-type genes and are not the result of mutations. This article reviews the known mechanisms of resistance, including the ability of the biofilm matrix to prevent antibiotics from reaching the cells and the function of individual genes that are preferentially expressed in biofilms. Evidence suggests that these mechanisms have been developed as a general stress response of biofilms that enables the cells in the biofilm to respond to all of the changes in the environment that they may encounter.

342 citations

Journal ArticleDOI
TL;DR: Findings regarding mechanisms underlying bacterial tolerance and persistence in biofilms and how these phenotypes are linked to antibiotic resistance are discussed are discussed.

300 citations

Journal ArticleDOI
TL;DR: Down-regulation of antioxidant enzymes in P. aeruginosa biofilms may enhance the rate of mutagenic events due to the accumulation of DNA damage and provide a further source of antibiotic-resistant mutants in the CF lung.
Abstract: Objectives: Isolates of Pseudomonas aeruginosa from cystic fibrosis (CF) patients are frequently hypermutable due to selection of mutants with defects in DNA repair genes such as mutS. Since P. aeruginosa grows as a biofilm within the infected CF lung, it is possible that this mode of growth enhances the mutability of the organism thereby increasing the opportunity to derive permanent hypermutators through mutation in DNA repair genes. We have now conducted experiments to examine this possibility. Methods: Using established procedures, we examined the mutability of P. aeruginosa PA01 in planktonic cultures and in biofilm cultures generated by growth in a Sorbarod system. Transcriptional profiling by DNA microarray was used to compare gene expression in planktonic and biofilm cells. Results: Mutation frequency determinations for resistance to rifampicin and ciprofloxacin demonstrated that biofilm cultures of P. aeruginosa displayed up to a 105-fold increase in mutability compared with planktonic cultures. Several genes (ahpC, katA, sodB and PA3529, a probable peroxidase) that encode enzymes conferring protection against oxidative DNA damage were down-regulated in biofilm cells. In particular, katA, which encodes the major pseudomonal antioxidant catalase, was down-regulated 7.7-fold. Conclusions: Down-regulation of antioxidant enzymes in P. aeruginosa biofilms may enhance the rate of mutagenic events due to the accumulation of DNA damage. Since P. aeruginosa forms biofilms in the CF lung, this mode of growth may enhance the direct selection of antibiotic-resistant organisms in CF patients and also increase the opportunity to derive permanent hypermutators thereby providing a further source of antibiotic-resistant mutants in the CF lung.

216 citations