Development of polylactic acid (PLA) bio-composite films reinforced with bacterial cellulose nanocrystals (BCNC) without any surface modification

Preparation of waterborne anti-counterfeiting ink based on dual luminescent nanohybrids of bacterial cellulose nanocrystals and lanthanide‑nitrogen co-modified GQDs

To address the growing challenge of counterfeit prevention, this study developed a novel anti-counterfeiting ink system based on bacterial cellulose nanocrystals (BCNC) and lanthanide (Er, Yb)‑nitrogen (N) co-dropped graphene quantum dots (GQDs), which exhibited both photoluminescence (PL) and upconversion photoluminescence (UCPL) fluorescent properties as well as excellent rheological characteristics. The Er/Yb/N-GQDs with positive charges were synthesized by a one-step hydrothermal method and subsequently assembled with negatively charged BCNC through electrostatic self-assembly to fabricate a novel nanohybrid, Er/Yb/N-GQDs-BCNC. Raman spectroscopy results indicated an enhancement in the graphitization of GQDs due to lanthanide modification. The TEM results demonstrated a homogeneous distribution of Er/Yb/N-GQDs on BCNC, while XRD, FTIR, and XPS analyses confirmed their physical binding, thus validating the successful synthesis of novel nanohybrids. Then, Er/Yb/N-GQDs-BCNC was introduced into PVA waterborne ink and exhibited dual anti-counterfeiting properties by emitting blue fluorescence at Em 440 nm under Ex 370 nm and green fluorescence at Em 550 nm under Ex 980 nm. Furthermore, the incorporation of BCNC significantly enhanced the thixotropic behavior and yield stress of the PVA waterborne ink. This enhancement made the dual anti-counterfeiting fluorescent ink more suitable for diversified applications on different devices and various substrates, thus providing a novel approach for convenient and rapid information encryption and high security anti-counterfeiting.

In vitro degradation and antibacterial activity of bacterial cellulose deposited flax fabric reinforced with polylactic acid and polyhydroxybutyrate

The objective of this study was to prepare biocomposites through the solution casting method followed by compression moulding in which bacterial cellulose (BC) deposited flax fabric (FF) produced through fermentation is coated with minimal amount of polylactic acid (PLA) and polyhydroxybutyrate (PHB). Biocomposites incorporated with 60 % of PLA or PHB (% w/w) show enhanced tensile strength. Cross-sectional morphology showed good superficial interaction of these biopolymers with fibres of FF thereby filling up the gaps present between the fibres. The tensile strength of biocomposites at 60 % PLA and 60 % PHB improved from 37.97 MPa (i.e., BC deposited FF produced in presence of honey) to 67.17 MPa and 56.26 MPa, respectively. Further, 0.25 % of nalidixic acid (NA) (% w/w) and 6 % of oleic acid (OA) (% w/w) incorporation into the biocomposites imparted prolonged antibacterial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The in vitro cytotoxicity of biocomposites was determined using L929 mouse fibroblast cells. The 3-(4,5-cime- thylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cytotoxicity tests showed that the PHB derived biocomposites along with antibacterial compounds in it were non-toxic. In vitro degradation of biocomposites was measured for up to 8 weeks in the mimicked physiological environment that showed a gradual rate of degradation over the period.

Fabrication of PLA-Based Electrospun Nanofibers Reinforced with ZnO Nanoparticles and In Vitro Degradation Study

In this work, electrospun nanofibers based on polylactic acid, PLA, reinforced with ZnO nanoparticles have been studied, considering the growing importance of electrospun mats based on biopolymers for their applications in different fields. Specifically, electrospun nanofibers based on PLA have been prepared by adding ZnO nanoparticles at different concentrations, such as 0.5, 1, 3, 5, 10 and 20 wt%, with respect to the polymer matrix. The materials have been characterized in terms of their morphological, mechanical, and thermal properties, finding 3 wt% as the best concentration to produce PLA nanofibers reinforced with ZnO nanoparticles. In addition, hydrolytic degradation in phosphate buffer solution (PBS) was carried out to study the effect of ZnO nanoparticles on the degradation behavior of PLA-based electrospun nanofiber mats, obtaining an acceleration in the degradation of the PLA electrospun mat.

Biodegradable Polylactic Acid-Polyhydroxyalkanoate-Based Nanocomposites with Bio-Hydroxyapatite: Preparation and Characterization

Biodegradable polymers play a significant role in medical applications, especially internal devices because they can be broken down and absorbed into the body without producing harmful degradation products. In this study, biodegradable polylactic acid (PLA)-polyhydroxyalkanoate (PHA)-based nanocomposites with various PHA and nano-hydroxyapatite (nHAp) contents were prepared using solution casting method. Mechanical properties, microstructure, thermal stability, thermal properties, and in vitro degradation of the PLA-PHA-based composites were investigated. PLA-20PHA/5nHAp was shown to give the desired properties so it was selected to investigate electrospinnability at different applied high voltages. PLA-20PHA/5nHAp composite shows the highest improvement of tensile strength at 36.6 ± 0.7 MPa, while PLA-20PHA/10nHAp composite shows the highest thermal stability and in vitro degradation at 7.55% of weight loss after 56 days of immersion in PBS solution. The addition of PHA in PLA-PHA-based nanocomposites improved elongation at break, compared to the composite without PHA. PLA-20PHA/5nHAp solution was successfully fabricated into fibers by electrospinning. All obtained fibers showed smooth and continuous fibers without beads with diameters of 3.7 ± 0.9, 3.5 ± 1.2, and 2.1 ± 0.7 µm at applied high voltages of 15, 20, and 25 kV, respectively.

Nano-Hydroxyapatite from White Seabass Scales as a Bio-Filler in Polylactic Acid Biocomposite: Preparation and Characterization

Nano-hydroxyapatite (nHAp) as a bio-filler used in PLA composites was prepared from fish by acid deproteinization (1DP) and a combination of acid-alkali deproteinization (2DP) followed by alkali heat treatment. Moreover, the PLA/nHAp composite films were developed using solution casting method. The mechanical and thermal properties of the PLA composite films with nHAp from different steps deproteinization and contents were compared. The physical properties analysis confirmed that the nHAp can be prepared from fish scales using both steps deproteinization. 1DP-nHAp showed higher surface area and lower crystallinity than 2DP-nHAp. This gave advantage of 1DP-nHAp for use as filler. PLA composite with 1DP-nHAp gave tensile strength of 66.41 ± 3.63 MPa and Young’s modulus of 2.65 ± 0.05 GPa which were higher than 2DP-nHAp at the same content. The addition of 5 phr 1DP-nHAp into PLA significantly improved the tensile strength and Young’s modulus. PLA composite solution with 1DP-nHAp at 5 phr showed electrospinnability by giving continuous fibers without beads.

Elucidation of Mechanical, Physical, Chemical and Thermal Properties of Microbial Composite Films by Integrating Sodium Alginate with Bacillus subtilis sp

Materials are the foundation in human development for improving human standards of life. This research aimed to develop microbial composite films by integrating sodium alginate with Bacillus subtilis. Sodium alginate film was fabricated as control. The microbial composite films were fabricated by integrating 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 g of Bacillus subtilis into the sodium alginate. Evaluations were performed on the mechanical, physical, chemical and thermal properties of the films. It was found that films reinforced with Bacillus subtilis significantly improved all the mentioned properties. Results show that 0.5 g microbial composite films had the highest tensile strength, breaking strain and toughness, which were 0.858 MPa, 87.406% and 0.045 MJ/m³, respectively. The thickness of the film was 1.057 mm. White light opacity, black light opacity and brightness values were 13.65%, 40.55% and 8.19%, respectively. It also had the highest conductivity, which was 37 mV, while its water absorption ability was 300.93%. Furthermore, it had a higher melting point of 218.94 °C and higher decomposition temperature of 252.69 °C. SEM also showed that it had filled cross-sectional structure and smoother surface compared to the sodium alginate film. Additionally, FTIR showed that 0.5 g microbial composite films possessed more functional groups at 800 and 662 cm⁻¹ wavenumbers that referred to C–C, C–OH, C–H ring and side group vibrations and C–OH out-of-plane bending, respectively, which contributed to the stronger bonds in the microbial composite film. Initial conclusions depict the potential of Bacillus subtilis to be used as reinforcing material in the development of microbial composite films, which also have the prospect to be used in electronic applications. This is due to the conductivity of the films increasing as Bacillus subtilis cell mass increases.

Heterogeneous deacetylation reaction of chitin under low-frequency ultrasonic irradiation

Low-frequency ultrasonic irradiation was employed as a low cost technique for chitin's deacetylation at a relatively low-temperature range (below 70 °C) and a short reaction times (up to 120 min). Eley-Rideal mechanism and the power-law model were carried out to describe the mechanism of the reaction. The results indicated that the produced chitosan deacetylation degree (DD) was up to 87.73% under the optimum conditions compared to 66.82% using the conventional one (thermo-alkaline process). The Fourier Transform Infrared (FTIR) observations of the produced chitosan presented the same fingerprint as the commercial chitosan, X-Ray Diffraction (XRD), and Differential Scanning Calorimetry (DSC) studies show that the DD induced a lousy impact on the chitosan's thermal degradation and crystallinity index. This work effectively demonstrates that chitin's deacetylation under low-frequency ultrasonic irradiation provides a green process to produce chitosan, and the power-law model, r_DD = k₁(C_R1-NH2)^α; k₁=Aexp-E_aRT, is an excellent model to describe the complex reaction.

Nanofluid to Nanocomposite Film: Chitosan and Cellulose-Based Edible Packaging

Chitosan (CH)-based materials are compatible to form biocomposite film for food packaging applications. In order to enhance water resistance and mechanical properties, cellulose can be introduced to the chitosan-based film. In this work, we evaluate the morphology and water resistance of films prepared from chitosan and cellulose in their nanoscale form and study the phenomena underlying the film formation. Nanofluid properties are shown to be dependent on the particle form and drive the morphology of the prepared film. Film thickness and water resistance (in vapor or liquid phase) are clearly enhanced by the adjunction of nanocrystalline cellulose.

Cellulose Nanocrystals to Improve Stability and Functional Properties of Emulsified Film Based on Chitosan Nanoparticles and Beeswax

The framework of this work was to develop an emulsion-based edible film based on a chitosan nanoparticle matrix with cellulose nanocrystals (CNCs) as a stabilizer and reinforcement filler. The chitosan nanoparticles were synthesized based on ionic cross-linking with sodium tripolyphosphate and glycerol as a plasticizer. The emulsified film was prepared through a combination system of Pickering emulsification and water evaporation. The oil-in-water emulsion was prepared by dispersing beeswax into an aqueous colloidal suspension of chitosan nanoparticles using high-speed homogenizer at room temperature. Various properties were characterized, including surface morphology, stability, water vapor barrier, mechanical properties, compatibility, and thermal behaviour. Experimental results established that CNCs and glycerol improve the homogeneity and stability of the beeswax dispersed droplets in the emulsion system which promotes the water-resistant properties but deteriorates the film strength at the same time. When incorporating 2.5% w/w CNCs, the tensile strength of the composite film reached the maximum value, 74.9 MPa, which was 32.5% higher than that of the pure chitosan film, while the optimum one was at 62.5 MPa, and was obtained by the addition of 25% w/w beeswax. All film characterizations demonstrated that the interaction between CNCs and chitosan molecules improved their physical and thermal properties.