Lactoferrin-Immobilized Surfaces onto Functionalized PLA Assisted by the Gamma-Rays and Nitrogen Plasma to Create Materials with Multifunctional Properties

Both cold nitrogen radiofrequency plasma and gamma irradiation have been applied to activate and functionalize the polylactic acid (PLA) surface and the subsequent lactoferrin immobilization. Modified films were comparatively characterized with respect to the procedure of activation and also with unmodified sample by water contact angle measurements, mass loss, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), and chemiluminescence measurements. All modified samples exhibit enhanced surface properties mainly those concerning biocompatibility, antimicrobial, and antioxidant properties, and furthermore, they are biodegradable and environmentally friendly. Lactoferrin deposited layer by covalent coupling using carbodiimide chemistry showed a good stability. It was found that the lactoferrin-modified PLA materials present significantly increased oxidative stability. Gamma-irradiated samples and lactoferrin-functionalized samples show higher antioxidant, antimicrobial, and cell proliferation activity than plasma-activated and lactoferrin-functionalized ones. The multifunctional materials thus obtained could find application as biomaterials or as bioactive packaging films.

Production and properties of nanocellulose-reinforced methylcellulose-based biodegradable films

Methylcellulose (MC)-based films were prepared by casting from its 1% aqueous solution containing 0.5% vegetable oil, 0.25% glycerol, and 0.025% Tween 80. Puncture strength (PS), puncture deformation (PD), viscoelasticity coefficient, and water vapor permeability (WVP) were found to be 147 N/mm, 3.46 mm, 41%, and 6.34 g.mm/m(2).day.kPa, respectively. Aqueous nanocellulose (NC) solution (0.1-1%) was incorporated into the MC-based formulation, and it was found that PS was improved (117%) and WVP was decreased (26%) significantly. Films containing 0.25% NC were found to be the optimum. Then films were exposed to gamma radiation (0.5-50 kGy), and it was revealed that mechanical properties of the films were slightly decreased after irradiation, whereas barrier properties were further improved with a decrease of WVP to 28.8% at 50 kGy. Molecular interactions due to incorporation of NC were supported by FTIR spectroscopy. Thermal properties of the NC-containing films were improved, confirmed by TGA and DSC. Crystalline peaks appeared due to NC addition, found by XRD. Micrographs of films containing NC were investigated by SEM.

Improving the compatibility of zein/poly(vinyl alcohol) blends by gamma irradiation and graft copolymerization of acrylic acid

The effect of gamma irradiation and graft copolymerization with different ratios of acrylic acid monomer (AAc) on improving the compatibility of polymeric blends based on zein, as natural protein, and different ratios of poly(vinyl alcohol) (PVA) up to 50% were studied. The structure property of the polymeric blends was characterized by Fourier transform infrared spectroscopy (FTIR), mechanical testing, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The FTIR analysis indicated that grafted AAc into zein/PVA matrix was stabilized by hydrogen bonding. The stress-strain curves showed that pure zein films were brittle, whereas pure PVA and zein/PVA blends films were tough materials either before or after gamma irradiation. The SEM micrographs indicated the formation of multilayers during the blending of zein and PVA, and these layers turned to dispersion in matrix after gamma irradiation and grafting with AAc, suggesting an effectiveness of gamma irradiation on improving compatibility.