Engineering nanoscale hierarchical morphologies and geometrical shapes for microbial inactivation in aqueous solution

Synthesis and molecular docking study of α-aminophosphonates as potential multi-targeting antibacterial agents

Antibacterial compounds that reduce extracellular polymeric substances (EPS) are needed to avoid bacterial biofilms in water pipelines. Herein, green one-pot synthesis of α-aminophosphonates (α-Amps) [A-G] was achieved by using ionic liquid (IL) as a Lewis acid catalyst. The synthesized α-Amp analogues were tested against different bacteria such as Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. The representative [B] analogue showed an efficient antibacterial effect with MIC values of 3.13 μg/mL for E. coli, P. aeruginosa, and 6.25 μg/mL for B. subtilis. Additionally, a strong ability to eliminate the mature bacterial biofilm, with super-MIC values of 12.5 μg/mL for E. coli, P. aeruginosa, and 25 μg/mL for B. subtilis. Moreover, bacterial cell disruption by ROS formation was also tested, and the compound [B] revealed the highest ROS level compared to other compounds and the control, and efficiently destroyed the extracellular polymeric substances (EPS). The docking study confirmed strong interactions between [B] analogue and protein structures with a binding affinity of -6.65 kCal/mol for the lyase protein of gram-positive bacteria and -6.46 kCal/mol for DNA gyrase of gram-negative bacteria. The results showed that α-Amps moiety is a promising candidate for developing novel antibacterial and anti-biofilm agents for clean water supply.

Comparative study between three carbonaceous nanoblades and nanodarts for antimicrobial applications

The design of nanostructured materials occupies a privileged position in the development and management of affordable and effective technology in the antibacterial sector. Here, we discuss the antimicrobial properties of three carbonaceous nanoblades and nanodarts materials of graphene oxide (GO), reduced graphene oxide (RGO), and single-wall carbon nanotubes (SWCNTs) that have a mechano-bactericidal effect, and the ability to piercing or slicing bacterial membranes. To demonstrate the significance of size, morphology and composition on the antibacterial activity mechanism, the designed nanomaterials have been characterized. The minimum inhibitory concentration (MIC), standard agar well diffusion, and transmission electron microscopy were utilized to evaluate the antibacterial activity of GO, RGO, and SWCNTs. Based on the evidence obtained, the three carbonaceous materials exhibit activity against all microbial strains tested by completely encapsulating bacterial cells and causing morphological disruption by degrading the microbial cell membrane in the order of RGO > GO > SWCNTs. Because of the external cell wall structure and outer membrane proteins, the synthesized carbonaceous nanomaterials exhibited higher antibacterial activity against Gram-positive bacterial strains than Gram-negative and fungal microorganisms. RGO had the lowest MIC values (0.062, 0.125, and 0.25 mg/mL against B. subtilis, S. aureus, and E. coli, respectively), as well as minimum fungal concentrations (0.5 mg/mL for both A. fumigatus and C. albicans). At 12 hr, the cell viability values against tested microbial strains were completely suppressed. Cell lysis and death occurred as a result of severe membrane damage caused by microorganisms perched on RGO nanoblades. Our work gives an insight into the design of effective graphene-based antimicrobial materials for water treatment and remediation.

Surface hydrolysis-anchored eugenol self-polishing marine antifouling coating

Traditional self-polishing antifouling coatings kill surface organisms by releasing toxic substances, which are damaging to the ecosystem. As a natural antimicrobial substance, eugenol is environmentally friendly and has been proven by different research teams to be effective in enhancing the anti-fouling effect of coatings in the real sea. While in these previous research works, the eugenol was released directly into the seawater thus cannot further serve as surface antifouling effect, leading to a limited antifouling effect of the coating. In this work, the quaternary ammonium component was introduced into the butyl ester-based resin - poly (eugenol methacrylate - acryloyloxyethyltrimethyl ammonium chloride - hexafluorobutyl methacrylate - methyl methacrylate - butyl methacrylate - ethylene glycol methyl ether acrylate) (EMQFP) coating for the first time by simple one-step free radical polymerization method. On the one hand, the eugenol produced by hydrolysis is anchored to the quaternary ammonium on the coating surface for a period of time due to the cationic-π interaction, instead of being released into seawater immediately after hydrolysis, thus increasing the utilization rate of eugenol; on the other hand, the negatively charged carboxylate groups generated after hydrolysis in the coating are mutually attracted to quaternary ammonium through electrostatic effect, so the resin chain segment conformation on the coating surface adjusted to produce zwitterionic-like structure, and the hydration of zwitterionic inhibits primary fouling adhesion.

Engineering microbes for enhancing the degradation of environmental pollutants: A detailed review on synthetic biology

Anthropogenic activities resulted in the deposition of huge quantities of contaminants such as heavy metals, dyes, hydrocarbons, etc into an ecosystem. The serious ill effects caused by these pollutants to all living organisms forced in advancement of technology for degrading or removing these pollutants. This degrading activity is mostly depending on microorganisms owing to their ability to survive in harsh adverse conditions. Though native strains possess the capability to degrade these pollutants the development of genetic engineering and molecular biology resulted in engineering approaches that enhanced the efficiency of microbes in degrading pollutants at faster rate. Many bioinformatics tools have been developed for altering/modifying genetic content in microbes to increase their degrading potency. This review provides a detailed note on engineered microbes - their significant importance in degrading environmental contaminants and the approaches utilized for modifying microbes. The genes responsible for degrading the pollutants have been identified and modified fir increasing the potential for quick degradation. The methods for increasing the tolerance in engineered microbes have also been discussed. Thus engineered microbes prove to be effective alternate compared to native strains for degrading pollutants.

Immobilized arginine/tryptophan-rich cyclic dodecapeptide on reduced graphene oxide anchored with manganese dioxide for microbial biofilm eradication

To avoid the accumulation of bacterial biofilms in water pipelines, it is critical to develop potent antimicrobial agents with good ability to reduce extracellular polymeric substances (EPS). In this study, cyclic dodecapeptides were synthesized, and different mutations for increasing the ratio of arginine (Arg) and tryptophan (Trp) were introduced. Separately, the synthesized dodecapeptides were immobilized on a reduced graphene oxide nanocomposite anchored with a hierarchical β-MnO₂ (RGO/β-MnO₂) hybrid. With a minimum inhibitory concentration of 0.97 g/mL, the immobilized Arg-Trp rich antimicrobial peptides (AMP) on RGO/MnO₂ nanocomposite, Cdp-4/RGO/MnO₂, showed superior efficacy against multidrug-resistant Pseudomonas aeruginosa ATCC 15692 (P. aeruginosa) planktonic cells. The immobilized Cdp-4/RGO/β-MnO₂ also eradicated the mature biofilm by 99% with a minimum inhibitory concentration value of 62.5 µg/mL with significant reduction of EPS. These characteristics allow the use of the immobilized Arg-Trp rich AMP as a promising antimicrobial agent against microbial biofilms, present in water distribution systems.

Synergistic effect of copolymeric resin grafted 1,2-benzisothiazol-3(2H)-one and heterocyclic groups as a marine antifouling coating

In order to find a new type of antifouling coating with higher biological activity and more environmental protection, heterocyclic compounds and benzisothiazolinone were introduced into acrylic resin to prepare a new type of antifouling resin. In this study, a series of grafted acrylic resins simultaneously containing benzoisothiazolinone and heterocyclic monomers were prepared by the copolymerization of an allyl monomer with methyl methacrylate (MMA) and butyl acrylate (BA). Inhibitory activities of the copolymers against marine fouling organisms were also investigated. Results revealed that the copolymers exhibit a clear synergistic inhibitory effect on the growth of three seaweeds: Chlorella, Isochrysis galbana and Chaetoceros curvisetus, respectively, and three bacteria, Staphylococcus aureus, Vibrio coralliilyticus and Vibrio parahaemolyticus, respectively. In addition, the copolymers exhibited excellent inhibition against barnacle larvae. Marine field tests indicated that the resins exhibit outstanding antifouling potency against marine fouling organisms. Moreover, the introduction of the heterocyclic group led to the significantly enhanced antifouling activities of the resins; the addition of the heterocyclic unit in copolymers led to better inhibition than that observed in the case of the resin copolymerized with only the benzoisothiazolinone active monomer.