Synergic Effect of Nanolignin and Metal Oxide Nanoparticles into Poly(l-lactide) Bionanocomposites: Material Properties, Antioxidant Activity, and Antibacterial Performance

Abstract

Binary and ternary poly(L-lactide) (PLLA)-based nanocomposites, containing nanolignin (1 wt %) and different metal oxide nanoparticles (0.5 wt %, Ag 2 O, TiO 2 , WO 3 , Fe 2 O 3 , and ZnFe 2 O 4 ), were realized by solvent casting, and their morphological, thermal, surface, optical, antioxidant, and antimicrobial characterizations were performed. The presence of metal oxide nanoparticles at the selected weight concentration affects the surface microstructure of the PLLA polymer, and this outcome is particle-type dependent, according to the shape, morphology, and chemical properties of the selected nanoparticles (NPs). Analogously, wettability of PLLA-based nanocomposites was slightly modified by the presence of hydrophobic lignin nanoparticles and different shaped metal oxides. Results of differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD) tests confirmed that nanoparticle addition confined the mobility of the amorphous phase, increasing at the same time the formation of more numerous but less perfect PLLA crystals. Interestingly, antioxidant activity was also obtained in ternary-based nanocomposites, where a synergic effect of lignin and metal oxide nanoparticles was obtained. Antibacterial tests showed manifest activity of TiO 2 and Ag 2 O nanoparticles containing PLLA films, and the time dependence was more evident for Staphylococcus aureus than for Escherichia coli. Lignin nanoparticles are able to provide protection against UV light while still allowing visible light to pass and even surpass the UV-protection capacity provided by many inorganic nanoparticles. This makes them an attractive renewable additive for the realization of PLLA/metal oxide nanocomposites in the fields of food, drug packaging, and biomedical industry, where antibacterial and antioxidant properties are required.

Lignin Nanoparticles: A Promising Tool to Improve Maize Physiological, Biochemical, and Chemical Traits

“…Results of FESEM analysis of LNP ( Figure 1 a) showed that the nanoparticles have diameters in the range of 50 ± 20 nm [ 35 , 40 ] and appear in the form of aggregates: this phenomenon is related to the hydrodynamic radius of colloidal lignin in aqueous suspension, that can be influenced by different parameters, such as temperature, pH [ 41 , 42 ], and lignin concentration [ 43 ].…”

Lignin: Drug/Gene Delivery and Tissue Engineering Applications

“…Another possible route explored for the development of high-value usage lignin-based materials is hybridization with the inorganic components. 12 , 13 , 26 Lignin can be associated with the inorganic nanomaterials that form lignin-based hybrid nanocomposites. Hybridization changes the chemical nature and reactivity of lignin.…”

“…Because of the neutral 3D network, lignin can afford the uniform lignin/inorganic nanocomposite system when it combines with the inorganic nanoparticles/metals. 26 The resultant lignin-based nanomaterials can be used as high-value-added materials for potential applications in various biomedical domains, particularly in drug/gene delivery and tissue engineering due to synergetic interactions from both organic lignin and inorganic nanocomposites. 12 , 13 , 26 The binding ability of lignin with nanomaterials or other multivalent metal ions involves active functional groups (phenol, hydroxyl, and carboxyl groups), which act as both chelating and reducing agents to the metal center.…”

“… 26 The resultant lignin-based nanomaterials can be used as high-value-added materials for potential applications in various biomedical domains, particularly in drug/gene delivery and tissue engineering due to synergetic interactions from both organic lignin and inorganic nanocomposites. 12 , 13 , 26 The binding ability of lignin with nanomaterials or other multivalent metal ions involves active functional groups (phenol, hydroxyl, and carboxyl groups), which act as both chelating and reducing agents to the metal center. 2 , 3 , 8 The chelating ability of lignin depends on the type of lignin and its chemical structure.…”

Multifunctional lignin-based nanocomposites and nanohybrids

“…Such efforts are aimed at reducing the dependency on fossil carbon feedstocks and to fully utilize the plant-based resources, for example, in products relevant to the resin and plastic industries. Many applications such as bio-medical and nutritional materials under development strive to take advantage of lignins' antioxidant activity, [10][11][12][13] or its high carbon content attractive to carbonaceous materials in the form of fibers and electroactive components. 14 Owing to its amphiphilic structure, lignins have been shown to be surface-active and are able to improve the strength at interfaces, for example, in adhesives.…”