Preparation and characterization of antimicrobial films based on nanocrystalline cellulose

Recent advances in cellulose nanocrystals-based antimicrobial agents

Over the past five years, there has been growing interest in the design of modified cellulose nanocrystals (CNCs) as nanoscale antimicrobial agents in potential end-user applications such as food preservation/packaging, additive manufacturing, biomedical and water purification. The interest of applying CNCs-based antimicrobial agents arise due to their abilities to be derived from renewable bioresources and their excellent physicochemical properties including rod-like morphologies, large specific surface area, low toxicity, biocompatibility, biodegradability and sustainability. The presence of ample surface hydroxyl groups further allows easy chemical surface modifications for the design of advanced functional CNCs-based antimicrobial materials. Furthermore, CNCs are used to support antimicrobial agents that are subjected to instability issues. The current review summarizes recent progress in CNC-inorganic hybrid-based materials (Ag and Zn nanoparticles, other metal/metal oxide) and CNC-organic hybrid-based materials (polymers, chitosan, simple organic molecules). It focuses on their design, syntheses and applications with a brief discussion on their probable modes of antimicrobial action whereby the roles of CNCs and/or the antimicrobial agents are highlighted.

Carbon dots, cellulose nanofiber, and essential oil from Torreya grandis aril added to fish scale gelatin film for tomato preservation

In this study, carbon dots (CDs), cellulose nanofibers (CNF) and essential oil nanoemulsion (EON) were extracted from the aril waste of Torreya grandis following nuts production. These three nanomaterials were formulated for the preparation of a composite film to be employed for postharvest tomato storage. Visual, microscopical and physicochemical properties of the prepared nanocomposite films were analyzed at different levels of CDs and CNF for optimization purposes. The UV absorption and antioxidant capacity of gelatin film with 10 % CDs (G/10CD) were enhanced compared with gelatin (G) film, concurrent with a reduction in water barrier capacity, water contact angle (WCA) and tensile strength (TS). Compared with G/10CD film, the WCA of gelatin film after incorporation of 10 % CDs and 3 % CNF (G/10CD/3CNF) was significantly increased by 14.5°at 55 s. In contrast, TS increased by 1.26 MPa, as well as the significant enhancement in water barrier capacity. The above composite film mixed with NEO (G/10CD/3CNF/EON) exerted further antimicrobial effects against Escherichia coli. G/10CD/3CNF/EON coating effectively extended tomato shift life compared with the control group. Therefore, this new eco-friendly film presents several advantages of biodegradability, sustainability as well as multifunctional properties posing it as potential packaging material for food applications.

Nanofibrillated cellulose as coating agent for food packaging paper

Nanofibrillated cellulose (NFC), a promising bio-based nanomaterial, has received much attention in the field of coating preparation due to its unique properties. Herein, NFC was prepared from microcrystalline cellulose (MCC) via high-pressure homogenization process and deliberately employed as coating agent to enhance the properties of paper coatings and coated paper. The results demonstrated that the obtained paper coatings exhibited strong NFC concentration dependence on rheological behavior and displayed decreased water retention value with the increased NFC addition. Meanwhile, NFC addition was found to lead to the reduced Cobb value, improved air resistance, and enhanced tensile strength of coated paper. Under an optimized NFC addition of 0.30-0.40%, the properties of coated paper generally reached the optimum state. Moreover, SEM observation further confirmed that NFC addition imparted a relatively uniform surface structure to coated paper. Hence, NFC could be defined as an effective coating agent for developing high-performance coated paper for food packaging applications.

N-Halamine Hydantoin-Containing Chitosan: Synthesis, Characterization, Thermal and Photolytic Stability Studies

Current demand for new protective materials ensuring sterility is systematically growing. The purpose of this work was the synthesis of the biocidal N-halamine hydantoin-containing chitosan (CS-CMH-Cl) and characterization of its properties. The functionalization of the chitosan by 5-hydantoinacetic acid substitution leads to obtaining the CS-CMH polymer, which was chlorinated in next step to transform N-H into N-Cl bonds. In this study, the possibility of forming two biocidal N-Cl bonds in hydantoin ring, grafted onto chitosan chains, was proved. The structure and stability of the prepared material was confirmed by spectroscopic (FTIR, NMR, colorimetric test) and microscopic analyses (SEM, AFM). Surface properties were investigated based on contact-angle measurements. In addition, the thermal and photochemical stability of the obtained samples were determined as functional features, determining the range of potential use. It was found that both modified chitosan polymers (CS-CMH and CS-CMH-Cl) were characterized by the smaller thermal stability and more hydrophilic and rougher surface than unmodified CS. Photooxidative degradation of the obtained materials was observed mainly on the sample surface. After irradiation, the surfaces became more hydrophilic-especially in the case of the CS-CMH-Cl-which is advantageous from the point of view of the antibacterial properties. Antibacterial tests against S. aureus and E. coli confirmed the antibacterial activities of received CS-CMH-Cl material.