Jong-Whan Rhim

Preparation and properties of carbohydrate-based composite films incorporated with CuO nanoparticles

The present study aimed to develop the carbohydrate biopolymer based antimicrobial films for food packaging application. The nanocomposite films of various biopolymers and copper oxide nanoparticles (CuONPs) were prepared by solvent casting method. The nanocomposite films were characterized using SEM, FTIR, XRD, and UV-vis spectroscopy. The thermal stability, UV barrier, water vapor permeability, and antibacterial activity of the composite films were also evaluated. The surface morphology of the films was dependent on the types of polymers used. The XRD revealed the crystallinity of CuONPs in the composite films. The addition of CuONPs increased the thickness, tensile strength, UV barrier property, relative humidity, and water vapor barrier property. The CuONPs incorporated composite films exhibited strong antibacterial activity against Escherichia coli and Listeria monocytogenes. The developed composite films could be used as a UV-light barrier antibacterial films for active food packaging.

Facile approach for large-scale production of metal and metal oxide nanoparticles and preparation of antibacterial cotton pads

Metallic nanoparticles such as zinc oxide (ZnONPs), copper oxide (CuONPs), and silver (AgNPs) were synthesized in gram scale using green methods. The antibacterial cotton fibers/nanoparticles (cotton fibers/NPs) composite pads were prepared, and nanoparticle binding/release tests were performed. All the NPs were crystalline and showed characteristic XRD diffraction peaks and showed the characteristic FTIR bands of the respective nanoparticles. All the NPs showed strong antimicrobial activity against Gram-positive and Gram-negative pathogenic bacteria. The NPs were attached to the cotton pad by adsorption at different extent depending on the types of nanoparticles. The adsorption and release of nanoparticles on and from cotton pads were also dependent on the types of nanoparticles. The NPs-adsorbed cotton pads showed potent antibacterial activity against pathogenic bacteria such as Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Staphylococcus epidermis. The developed NPs-adsorbed cotton pads have potential to be used as wound dressings and antibacterial food packaging applications.

Preparation of antimicrobial hybrid nano-materials using regenerated cellulose and metallic nanoparticles

In this study, antimicrobial hybrid nano-materials were prepared by one-pot syntheses of silver (Ag), copper oxide (CuO), or zinc oxide (ZnO) nanoparticles (NPs) during regeneration of cellulose from cotton linter (CL) and microcrystalline cellulose (MCC). SEM micrographs indicated that the metallic nanoparticles were attached to the surface of the regenerated cellulose. EDX and ICP results showed that more AgNPs were adsorbed on the cellulose than CuONPs or ZnONPs. FTIR results revealed that the metallic nanoparticles were attached to the cellulose through the interaction with the hydroxyl group of cellulose. XRD results showed the characteristic diffraction peaks of individual metallic nanoparticles. The thermal stability of the R-CL and R-MCC increased in the hybrids with AgNPs and ZnONPs. The R-cellulose/metallic NPs hybrids showed strong antibacterial activity against E. coli and L. monocytogenes. Thus, the hybrid nano-materials can be used as nanofillers for the preparation of antibacterial packaging films.

Preparation of multifunctional chitin nanowhiskers/ZnO-Ag NPs and their effect on the properties of carboxymethyl cellulose-based nanocomposite film

Chitin nanowhiskers (ChNW) were isolated and used for the synthesis of hybrid ChNW/ZnO-Ag NPs. The hybrid nanoparticles were used for the preparation of multifunctional carboxymethyl cellulose (CMC) films. A ChNW was needle shape with the width of 8-40nm, the length of 150-260nm, and crystallinity index of 93.6%. The ZnO-Ag NPs were spherical with the diameter of 10.5-16.2nm. STEM, EDX, XRD, and UV-vis analyses confirmed the formation of ZnO-Ag NPs on the surface of ChNW. The thermal stability of ChNW was increased by incorporation of ZnO-Ag NPs. A CMC-based nanocomposite film incorporated with 5wt% of ChNW/ZnO-Ag NPs was homogeneous and showed the high UV-barrier property. The tensile strength (TS) and elastic modulus (E) of the composite film increased by 18-32% and 55-100%, respectively, while the elongation at break (EB) decreased by 23-33%. CMC composite films showed strong antibacterial activity against E. coli and L. monocytogenes.

Characterization of carboxymethyl cellulose-based nanocomposite films reinforced with oxidized nanocellulose isolated using ammonium persulfate method

Cellulose nanocrystals (CNCs) were isolated from cotton linter (CL) and microcrystalline cellulose (MCC) using an ammonium persulfate (APS) method for a simultaneous isolation and oxidation of CNCs. The CNCs were in rod-like shape with a diameter of 10.3nm and 11.4nm, a length of 120-150nm and 103-337nm, a crystallinity index of 93.5% and 79.1% for the CNCCL and CNCMCC, respectively. The suspensions of oxidized CNCs were transparent and stable with the zeta potential values of -50.6mV and -46.9mV. The CNCs were uniformly distributed within the carboxymethyl cellulose (CMC) polymer matrix. The tensile strength (TS) increased by 102% and 73%, and elastic modulus (E) increased by 228% and 166% with the incorporation of at 10wt% of CNCCL and CNCMCC, respectively. Conclusively, the CNCCL showed a more uniform particle size distribution, higher crystallinity, transparency, thermal stability, and superior mechanical strength compared with the CNCMCC.

Preparation of poly(lactide)/lignin/silver nanoparticles composite films with UV light barrier and antibacterial properties

Organosolv lignin was used as a reducing agent for the preparation of silver nanoparticles (AgNPs) and their incorporation into poly(lactide) (PLA) polymer to prepare composite films. The composite films were characterized using UV-vis spectroscopy, FE-SEM, FTIR, XRD, and TGA. The optical, mechanical, water vapor barrier, and antibacterial properties of the composite films were evaluated. The UV-vis spectra of films exhibited two characteristics peaks around 300 and 450nm attributed to lignin and AgNPs, respectively. XRD results indicated that the crystalline AgNPs had been formed. The transmission of light at 280nm decreased significantly after incorporation of lignin and AgNPs. FTIR results showed that there was no change in the chemical structure of PLA after incorporation of lignin and AgNPs. The mechanical and water vapor barrier properties of the composite films increased after lignin and AgNPs incorporation, The films containing AgNPs exhibited potent antibacterial activity against Escherichia coli and Listeria monocytogenes.

Effect of oxidized chitin nanocrystals isolated by ammonium persulfate method on the properties of carboxymethyl cellulose-based films

Oxidized chitin nanocrystals (ChNCs) were isolated from crab shell chitin using ammonium persulfate (APS) method. The oxidized ChNCs were in needle shape with a diameter of 15nm, the length of 400-500nm, and crystallinity index of 93.5%. Carboxymethyl cellulose (CMC)-based films reinforced with the ChNCs (0, 1, 5, and 10wt.%) were flexible and transparent. The mechanical strength of the CMC film increased significantly (p<0.05) after blending with the ChNCs. The tensile strength (TS) and elastic modulus (EM) increased by 88% and 243% when 10wt.% of ChNCs were incorporated. Water vapor barrier property of the composite films decreased and the hydrophilicity increased compared with the neat CMC film. The oxidized ChNCs obtained using the APS method have a high potential for being used as a reinforcing filler to improve the mechanical properties of nanocomposite films for the application in food packaging, nano-papers, hydrogels as well as biomedical applications.

Incorporation of zinc oxide nanoparticles improved the mechanical, water vapor barrier, UV-light barrier, and antibacterial properties of PLA-based nanocomposite films

Zinc oxide nanoparticles (ZnO NPs) were synthesized using zinc chloride and NaOH and they were incorporated to prepare PLA/ZnO NPs composite films. The SEM images showed that the ZnO NPs were cubical in shape with size ranged from 50 to 100 nm, and the PLA/ZnO NPs composite films were smooth and compact. The composite films exhibited strong UV-light barrier property with a slight decrease in the transparency. The thickness, tensile strength, and water vapor barrier property of the films increased significantly after incorporation of ZnO NPs. The TS of PLA films increased by 37.5%, but the WVP decreased by 30.5% from 3.11 × 10-11 to 2.16 × 10-11 g m/m2·Pa·s when 0.5 wt% of ZnO NPs was incorporated. The composite films exhibited potent antibacterial activity against food-borne pathogenic bacteria, Escherichia coli and Listeria monocytogenes. The developed films were applied to the packaging of a minced fish paste and showed strong antibacterial function. The prepared composite films could be used as antibacterial and UV-light barrier films for food packaging and biomedical applications.

Preparation of sulfur nanoparticles and their antibacterial activity and cytotoxic effect

Sulfur nanoparticles (SNPs) were prepared using sodium thiosulfate and hydrochloric acid, and the UV-visible spectrum showed the formation of nanoparticulate sulfur. The SNPs were characterized by UV-visible spectrophotometer, transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The antibacterial activity and the cytotoxic effects of the SNPs on the human lung carcinoma (A549), mouse colon carcinoma (CT26), Caco-2, and human fibroblast (CCD-986sk) cells were tested. In addition, the inhibitory effect of the SNPs on the cancer cell migration was evaluated. The SNPs capped with chitosan (SNP2) exhibited strong antibacterial activity against Escherichia coli and Staphylococcus aureus. SNP2 also effectively inhibited the proliferation and migration of cancer cells with minimal toxic effect on normal cells. SNP2 therefore has potential for medical applications, including those used as antibacterial and chemotherapeutic agents.

Antimicrobial wrapping paper coated with a ternary blend of carbohydrates (alginate, carboxymethyl cellulose, carrageenan) and grapefruit seed extract

A functional biopolymer-coated paper was prepared by coating a ternary blend of the alginate, carboxymethyl cellulose, and carrageenan with grapefruit seed extract (GSE) for the substitute use of synthetic polymer-coated paper. The microstructure of the surface and cross-section of the coated paper analyzed by field emission scanning electron microscope (FE-SEM) indicated that the biopolymer was compatible with the base paper and filled the pores of the porous fiber to make a smooth-surfaced coating paper. The properties of the biopolymer-coated paper, such as water and oil resistance, water vapor barrier, surface hydrophobicity, and mechanical properties, increased significantly compared with not only the base paper but also commercially used PE-coated paper. The blended biopolymer coating material exhibited strong antibacterial activity against food-borne pathogenic bacteria, Listeria monocytogenes and Escherichia coli, which were destroyed completely within 3 and 9 h, respectively. The packaging test for a minced fish cake packed with the biopolymer-coated paper showed the complete destruction of surface inoculated bacteria in 6-9 days. The biopolymer-coated paper showed a high potential for disposable food packaging applications to increase the shelf-life of packaged food.