Synthesis, characterization and biocidal efficiency of quaternary ammonium polymers silver nanohybrids against sulfate reducing bacteria

Smart colorimetric indicator films prepared from chitosan and polyvinyl alcohol with high mechanical strength and hydrophobic properties for monitoring shrimp freshness

This work aimed to develop and characterize a colorimetric indicator films based on chitosan (CS), polyvinyl alcohol (PVA), and shikonin (SKN) from radix Lithospermi by casting method. The prepared films can serve as smart packaging for monitoring shrimp freshness which having excellent antimicrobial and antioxidant activity. The shikonin containing films have better hydrophobicity, barrier properties, and tensile strength. The release kinetics analysis shows that the loading amount causes a prolonged release of SKN from the prepared films. Increasing SKN in the CS/PVA film from 1 wt% to 2 wt% improved antibacterial effect for 24 h. Additionally, pH-sensitive color shifts from reddish (pH 2) to purple-bluish (pH 13) were visually seen in shikonin based solutions as well as films. The CS/PVA/SKN film detected shrimp deterioration at three temperatures (25, -20, and 4 °C) through color change. This study introduces a favorable approach for smart packaging in the food industry using multifunctional films.

One-pot synthesis of novel chitosan-salicylaldehyde polymer composites for ammonia sensing

Chitosan (Chs)-salicylaldehyde (Sal) polymer derivatives were formed via the reaction of Chs-Sal with zinc oxide nanoparticles (ZnO NPs) and beta-cyclodextrin (β-CD). These polymers were synthesized through inclusion with β-CD and doping with ZnO NPs to give pseudopolyrotaxane and Chs-Sal/ZnO NPs composite, respectively, for low-temperature detection and sensing of NH3 vapors as great significance in environmental control and human health. Additionally, the polymer (Chs-Sal/β-CD/ZnO NPs) was prepared via the insertion of generated composite (Chs-Sal/ZnO NPs) through β-cyclodextrin ring. The structural and morphological characterizations of the synthesized derivatives were confirmed by utilizing FTIR, XRD and, SEM, respectively. Also, the optical properties and thermal gravimetric analysis (TGA) of the synthesized polymers were explored. The obtained results confirmed that using β-CD or ZnO NPs for modification of polymer (Chs-Sal) dramatically enhanced thermal stability and optical features of the synthesized polymers. Investigations on the NH3-sensing properties of Chs-Sal/β-CD/ZnO NPs composite were carried out at concentrations down to 10 ppm and good response and recovery times (650 s and 350 s, respectively) at room temperature (RT) and indicated that modification by β-CD and doping with ZnO NPs effectively improves the NH3-sensing response of Chs-Sal from 712 to 6192 using Chs-Sal/β-CD/ZnO NPs, respectively, with low LOD and LOQ of 0.12 and 0.4 ppb, respectively.

Control and prevention of microbially influenced corrosion using cephalopod chitosan and its derivatives: A review

Microbially influenced corrosion (MIC) of metals is an important industrial problem, causing 300-500 billion dollars of economic loss worldwide each year. It is very challenging to prevent or control the MIC in the marine environment. Eco-friendly coatings embedded with corrosion inhibitors developed from natural products may be a successful approach for MIC prevention or control. As a natural renewable resource, cephalopod chitosan has a number of unique biological properties, such as antibacterial, antifungal and non-toxicity effects, which attract scientific and industrial interests for potential applications. Chitosan is a positively charged molecule, and the negatively charged bacterial cell wall is the target of its antimicrobial action. Chitosan binds to the bacterial cell wall and disrupts the normal functions of the membrane by, for example, facilitating the leakage of intracellular components and impeding the transport of nutrients into the cells. Interestingly, chitosan is an excellent film-forming polymer. Chitosan may be applied as an antimicrobial coating substance for the prevention or control of MIC. Furthermore, the antimicrobial chitosan coating can serve as a basal matrix, in which other antimicrobial or anticorrosive substances like chitosan nanoparticles, chitosan silver nanoparticles, quorum sensing inhibitors (QSI) or the combination of these compounds, can be embedded to achieve synergistic anticorrosive effects. A combination of field and laboratory experiments will be conducted to test this hypothesis for preventing or controlling MIC in the marine environment. Thus, the proposed review will identify new eco-friendly MIC inhibitors and will assay their potential in future applications in the anti-corrosion industry.

Immobilization of α-galactosidase in polyvinyl alcohol-chitosan-glycidyl methacrylate hydrogels based on directional freezing-assisted salting-out strategy for hydrolysis of RFOs

Raffinose family oligosaccharides (RFOs) in food are the main factors causing flatulence in Irritable Bowel Syndrome (IBS) patients and the development of effective approaches for reducing food-derived RFOs is of paramount importance. In this study, polyvinyl alcohol (PVA)-chitosan (CS)-glycidyl methacrylate (GMA) immobilized α-galactosidase was prepared by the directional freezing-assisted salting-out technique, aimed to hydrolyze RFOs. SEM, FTIR, XPS, fluorescence and UV characterization results demonstrated that α-galactosidase was successfully cross-linked in the PVA-CS-GMA hydrogels, forming a distinct porous stable network through the covalent bond between the enzyme and the carrier. Mechanical performance and swelling capacity analysis illustrated that α-gal @ PVA-CS-GMA not only had suitable strength and toughness for longer durability, but also exhibited high water content and swelling capacity for better retention of catalytic activity. The enzymatic properties of α-gal @ PVA-CS-GMA showed an improved Km value, pH and temperature tolerance range, anti-enzymatic inhibitor (melibiose) activity compared to the free α-galactosidase and its reusability was at least 12 times with prolonged storage stability. Finally, it was successfully applied in the hydrolysis of RFOs in soybeans. These findings provide a new strategy for the development of α-galactosidase immobilization system to biological transform the RFOs components in the food for diet intervention of IBS.

Cationic Lignin-Based Hyperbranched Polymers to Circumvent Drug Resistance in Pseudomonas Keratitis

The rise of antimicrobial-resistant bacteria strains has been a global public health concern due to their ability to cause increased patient morbidity and a greater burden on the healthcare system. As one of the potential solutions to overcome such bacterial infections, hyperbranched copolymers with cationic charges were developed. These copolymers were assessed for their antimicrobial efficacy and their bactericidal mechanisms. They were found to be potent against mobile colistin-resistant 1 strains, which was significant as colistin is known to be the last-resort antibiotic against Gram-negative bacteria. Furthermore, there was no sign of mutational resistance developed by E. Coli ATCC 25922 and MCR 1+ E. Coli against the copolymer even up to 20 passages. The ability to evade inducing resistance would provide invaluable insights for future antibiotic development. Our studies suggest that the bactericidal efficacy comes from the ability to target the outer membrane efficaciously. In vivo study using a Pseudomonas keratitis model showed that the copolymer was compatible with the eye and further supported that the copolymer treatment was effective for complete bacteria elimination.

Chitosan/Lignosulfonate Nanospheres as "Green" Biocide for Controlling the Microbiologically Influenced Corrosion of Carbon Steel

In this work, uniform cross-linked chitosan/lignosulfonate (CS/LS) nanospheres with an average diameter of 150–200 nm have been successfully used as a novel, environmentally friendly biocide for the inhibition of mixed sulfate-reducing bacteria (SRB) culture, thereby controlling microbiologically influenced corrosion (MIC) on carbon steel. It was found that 500 µg·mL⁻¹ of the CS/LS nanospheres can be used efficiently for the inhibition of SRB-induced corrosion up to a maximum of 85% indicated by a two fold increase of charge transfer resistance (R_ct) on the carbon steel coupons. The hydrophilic surface of CS/LS can readily bind to the negatively charged bacterial surfaces and thereby leads to the inactivation or damage of bacterial cells. In addition, the film formation ability of chitosan on the coupon surface may have formed a protective layer to prevent the biofilm formation by hindering the initial bacterial attachment, thus leading to the reduction of corrosion.