Atomic-scale interactions of the interface between chitosan and Fe3O4

Efficient removal of per/polyfluoroalkyl substances from water using recyclable chitosan-coated covalent organic frameworks: Experimental and theoretical methods

Covalent organic frameworks (COFs) demonstrate remarkable potential for adsorbing per/polyfluoroalkyl substances (PFAS). Nevertheless, the challenge of recycling powdered COFs hampers their practical application in water treatment. In this research, a quaternary amine COF with inherent positive surface charge was synthesised to adsorb perfluorooctanoic acid (PFOA) via electrostatic interactions. The COF was then combined with chitosan (CS) through a simple dissolution-evaporation process, resulting in a composite gel material termed COF@CS. The findings indicated that the adsorption capacity of COF@CS significantly surpassed that of the original COF and CS. According to the Langmuir model, COF@CS achieved a maximum PFOA capacity of 2.8 mmol g-1 at pH 5. Furthermore, the adsorption rate increased significantly to 6.2 mmol g-1 h-1, compared to 5.9 mmol g-1 h-1 for COF and 3.4 mmol g-1 h-1 for CS. Notably, COF@CS exhibited excellent removal efficacy for ten other types of PFAS. Moreover, COF@CS could be successfully regenerated using a mixture of 70% ethanol and 1 wt% NaCl, and it exhibited stable reusability for up to five cycles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) characterisation, and theoretical calculations revealed that the quaternary amine functional group in COF served as the primary adsorption site in the composite gel material, while the protonated amino group on CS enhanced PFOA adsorption through electrostatic interaction. This study highlights the significant practical potential of COF@CS in the removal of PFAS from aqueous solution and environmental remediation.

Molecular dynamics simulations of the solubility and conformation change of chitosan grafted polyacrylamide: Impact of grafting rate

Graft modification is an effective approach to improve the water solubility and molecular weight of chitosan. This work investigated the effect of grafting rate on water solubility of chitosan-grafted polyacrylamide (Chi-g-PAM) using molecular dynamics simulations. The intramolecular and intermolecular interaction between Chi-g-PAM with the grafting rate of 100%-250% and water together with the conformation change were analyzed by radial distribution function (RDF), radius of gyration, solvation free energy (ΔGSFE), mean square displacement, diffusion coefficient and shear viscosity. The results showed that the intramolecular hydrogen bonding of Chi-g-PAM was the dominant factor affecting its water solubility. While the grafting rate of Chi-g-PAM increased from 100% to 250%, the RDF of Chi-g-PAM decreased from 5.39 to 3.57 between O-H at 2.0 Å and 2.60 to 1.30 between N-H at 2.1 Å. The interaction between Chi-g-PAM and water increased with grafting rate as the absolute value of ΔGSFE for Chi-g-PAM increased from 432.917 kcal/mol to 858.749 kcal/mol. The solubility of Chi-g-PAM in acidic solution was much better than that of Chi-g-PAM in aqueous solution. Our work on the fundamental insights into the effect of grafted molecular structure of chitosan-based copolymer on its solubility will benefit the development of environmentally friendly chitosan-based flocculants.

Iron oxide magnetic aggregates: Aspects of synthesis, computational approaches and applications

Superparamagnetic magnetite nanoparticles have been central to numerous investigations in the past few decades for their use in many applications, such as drug delivery, medical diagnostics, magnetic separation, and material science. However, the properties of single magnetic nanoparticles are sometimes not sufficient to accomplish tasks where a strong magnetic response is required. In light of this, aggregated magnetite nanoparticles have been proposed as an alternative advanced material, which may expand and combine some of the advantages of single magnetic nanoparticles, including superparamagnetism, with an enhanced magnetic moment and increased colloidal stability. This review comprehensively discusses the current literature on aggregates made of magnetic iron oxide nanoparticles. This review is divided into three sections. First, the current synthetic strategies for magnetite nanoparticle aggregates are discussed, together with the influence of different stabilizers on the primary crystals and the final aggregate size and morphology. The second section is dedicated to computational approaches, such as density functional methods (which permit accurate predictions of electronic and magnetic properties and shed light on the behavior of surfactant molecules on iron oxide surfaces) and molecular dynamics simulations (which provide additional insight into the influence of ligands on the surface chemistry of iron oxide nanocrystals). The last section discusses current and possible future applications of iron oxide magnetic aggregates, including wastewater treatment, water purification, medical applications, and magnetic aggregates for materials displaying structural colors.

Coprecipitation-based synchronous chlorantraniliprole encapsulation with chitosan: carrier-pesticide interactions and release behavior

BACKGROUND

Controlled-release pesticide formulations have emerged as a promising approach towards sustainable pest control. Herein, an environment-friendly formulation of insecticide chlorantraniliprole (CAP) was fabricated through a simple approach of coprecipitation-based synchronous encapsulation by chitosan (CTS), with carrier-pesticide interaction mechanism and release behavior investigated.

RESULTS

The resulting CAP/CTS controlled-release formulation (CCF) showed a good loading content of 28.1% and a high encapsulation efficiency of 75.6%. Instrument determination in combination with molecular dynamics (MD) simulations displayed that the primary interactions between CAP and CTS were physical adsorption and complicated hydrogen (H)-bonds, which formed dominantly between NH in amides [or nitrogen (N) in ring structures] of CAP and hydroxyl (or amino) groups of CTS, as well as oxygen (O) in CAP with hydrogen in CTS or H2 O molecules. The in vitro release tests exhibited obvious pH/temperature sensitivity, with release dynamics following the first-order or Ritger-Peppas model. As the temperature increased, the CAP release process of the Ritger-Peppas model changed from Case-II to anomalous transport, and ultimately to a Fickian diffusion mechanism. The control effect against Plutella xylostella larvae also was evaluated by toxicity tests, where comparable efficacy of CCF to the commercial suspension concentrate was obtained.

CONCLUSION

The innovative, easy-to-prepare CCF can be used as a formulation with obvious pH/temperature sensitivity and good efficacy on target pests. This work contributes to the development of efficient and safe pesticide delivery systems, especially using the natural polymer materials as carriers. © 2023 Society of Chemical Industry.

Adsorption of antimicrobial peptide onto chitosan-coated iron oxide nanoparticles fosters oxidative stress triggering bacterial cell death

In the prevailing environmental status quo, bacterial resistance has made antibiotics and antimicrobial peptides (AMPs) ineffective, imparting a serious threat and putting a much greater financial burden on the biomedical and food industries. For this reason, the present study investigates the potential of iron oxide nanoparticles (IONPs) coated with chitosan (CS-IONP) as a platform for augmenting the antimicrobial activity of antimicrobial peptides like nisin. Hence, the nisin is allowed to be adsorbed onto chitosan-coated IONPs to formulate nisin-loaded CS-IONP nanoconjugates. The nanoconjugates were characterized by various optical techniques, such as XRD, FTIR, SEM, zeta and DLS. Remarkably, lower concentrations of N-CS-IONP nanoconjugate exhibited significant and broad-spectrum antibacterial potency compared to bare IONPs and nisin against both Gram-positive and Gram-negative bacteria. Biofilm production was also found to be drastically reduced in the presence of nanoconjugates. Further investigation established a relationship between an increase in antibacterial activity and the enhanced generation of reactive oxygen species (ROS). Oxidative stress exhibited due to enhanced ROS generation is a conclusive reason for the rupturing of bacterial membranes and leakage of cytoplasmic contents, eventually leading to the death of the bacteria. Thus, the current study emphasizes the formulation of a novel antimicrobial agent which exploits magnetic nanoparticles modulated with chitosan for enhanced remediation of resistant bacteria due to oxidative stress imparted by the nanoconjugates upon interaction with the bacteria, leading to cell death.

One-Step Preparation of Fe3O4/Nanochitin Magnetic Hydrogels with Remolding Ability by Ammonia Vapor Diffusion Gelation for Osteosarcoma Therapy

Chitin, a kind of second abundant natural saccharide, has great potential in biomedical applications. Here, chitin nanofibers combined with magnetic nanoparticles, a magnetic hydrogel, was prepared in one step by mixing Fe ions with partially deacetylated chitin nanofibers (DEChNs) and physically coagulating in an ammonia gas bath. The storage modulus of the prepared magnetic DEChN (M-DEChN) hydrogels reached 5507 Pa and could be remolded by adjusting the pH value assisted with an ultrasound treatment. In addition, the M-DEChN hydrogels showed an assignable heating behavior in alternating electromagnetic fields (AMFs), and the temperature of the M-DEChN was adjustable by controlling the content of magnetic particles inside. Benefiting from the remote heating ability, the biocompatible magnetic hydrogel showed thermoablation ability to osteosarcoma cells both in vitro and in vivo. These kinds of M-DEChN hydrogels show great application prospects in killing cancer cells.

Effect of ZnO-based nanophotocatalyst on degradation of aniline

In this research, a zinc oxide/copper oxide/graphene oxide (ZnO/CuO/GO) nanophotocatalyst was synthesized for photodegradation of aniline as a pollutant, upon exposure to ultraviolet light (UV). Three variables including initial aniline concentration, the nanophotocatalyst dosage, and pH were designed. The statistical test and optimal conditions were determined. The consequences specified that the optimum values of pH, initial aniline concentration, the dosage of nanophotocatalyst, and the reaction time were 6, 150 ppm, 1 g/L, and 3 h, respectively. The obtained results revealed that the photodegradation of aniline was enhanced with doping zinc oxide and CuO on the graphene oxide. Under optimal conditions, 97% photodegradation of aniline was observed. The mechanism of aniline degradation with nanophotocatalyst was evaluated by molecular dynamic (MD) graphs. The interactions between nanophotocatalysts and aniline were considered by energy, density graph.

Investigation on absorption and release of mercaptopurine anticancer drug from modified polylactic acid as polymer carrier by molecular dynamic simulation

The absorption and release of 6-mercaptopurine anticancer drug was investigated in biodegradable and biocompatible polymer of polylactic acid (PLA) using molecular dynamics simulation. For this purpose, the amount of mixing energy, radius of gyration, mean squared displacement and radial distribution function were computed and compared in concentrations of 5-36 wt% of 6-mercaptopurine drug. The simulation results show that increasing the concentration of the drug reduces mixing energy and PLA polymer carrier is able to carry 35.8 wt% of 6-mercaptopurine anticancer drug. Based on these results, the amount of 6-mercaptopurine release from PLA carrier 35.8 wt% of it in water environment is zero due to hydrophobic property of PLA and 6-mercaptopurine. Finally, polyethylene glycol (PEG) polymer with different percentages (10-30 wt%) was used to modify PLA carrier. The simulation results show that the rate of drug release increases by increasing the concentration of PEG polymer in the modified PLA carrier and also with increasing the percentage of drug loaded in the carrier and also the optimum weight percentage of PEG in modified PLA carrier for 35.8 wt% of drug concentration is 11 wt% and the rate of drug release is slower and equal to 4.4 molecules/ns.

Iron oxide nanoparticles - In vivo/in vitro biomedical applications and in silico studies

The review presents a broad overview of the biomedical applications of surface functionalized iron oxide nanoparticles (IONPs) as magnetic resonance imaging (MRI) agents for sensitive and precise diagnosis tool and synergistic combination with other imaging modalities. Then, the recent progress in therapeutic applications, such as hyperthermia is discussed and the available toxicity data of magnetic nanoparticles concerning in vitro and in vivo biomedical applications are addressed. This review also presents the available computer models using molecular dynamics (MD), Monte Carlo (MC) and density functional theory (DFT), as a basis for a complete understanding of the behaviour and morphology of functionalized IONPs, for improving NPs surface design and expanding the potential applications in nanomedicine.

Molecular dynamics simulation study of chitosan and gemcitabine as a drug delivery system

By using molecular dynamics (MD) simulation, biodegradable biopolymer chitosan as a carrier for the drug gemcitabine was investigated and the effect of three initial drug concentrations (10, 40, and 80%) on its loading efficiency was studied. Then water was added to the systems of drug and biopolymer and the effects of water on the interactions of drug and chitosan and on the drug loading efficiency were examined. From the results it was found that the maximum loading of the drug occurred at 40% of the drug concentration. The radial distribution function calculations indicated that in the absence of water molecules, the drug molecules were located at shorter distance from chitosan and the loading efficiency of the drug in these systems was higher.