Acid Films Research Articles

Self-standing tridimensional structures from crumpling techniques made with composite films of polylactic acid and exfoliated graphite

Obtaining three-dimensional porous materials for different applications, has required complex methods to achieve the desired structure. Crumpling is an alternative to develop three-dimensional structures by randomly folding a sheet of material and offering a simple yet effective method to generate a unique, stiff and lightweight three-dimensional structure with minimal processing. Here, composite films made from polylactic acid (PLA), and exfoliated graphite (EG) were elaborated using solvent casting method. Additional pore formation is achieved adding calcium carbonate (CaCO3) particles as porogen. Films were characterized to corroborate the integration of exfoliated graphite to the PLA matrix as well as crystallinity changes due to EG and CaCO3 particles. Microscopy help to identify pore formation after CaCO3 remotion. Tensile tests, after increasing EG concentration in PLA, corroborate the formation of stiffer films with lower tensile strength, while pore formation decreased tensile strength and Young's modulus. After adding 0.5% wt. of EG, tensile strength partially recovered while Young's modulus was maintained. Composite films allowed to obtain 3D crumpled structures. Tests under compression help finding that 0.5% wt. of EG in PLA matrix resulted in a yield strength (26.6 MPa) and Younǵs modulus (32.5 MPa) increase, making necessary the application of considerable force to deform them.

Influence of an innovative, biodegradable active packaging on the quality of sunflower oil and “pesto” sauce during storage

The aim of this research was to produce an innovative, biodegradable multilayer active packaging solution, with excellent oxygen barrier properties, to extend shelf- life of oily foods. In fact, one of the main drawbacks of biodegradable films is the low barrier they offer against external agents that can thus easily accelerate the foods degradation during shelf-life. In this study, a multilayer material obtained by the adhesion of two polylactic acid (PLA) films with cold plasma application, in place of synthetic adhesives, was realized. Moreover, cold plasma treatment was employed to immobilize the oxygen scavenger agent (ascorbic acid), chosen for the activation of the packaging material. Preliminary studies on activated PLA pouches filled with sunflower oil, used as model system, were performed. Model systems were stored at 35 °C to accelerate oil oxidation phenomenon and analysed for PV and colour during 64 days of storage. After that, different samples of “Genovese pesto”, were tested as real food, stored at 25 and 45 °C and analysed for PV, water activity, rheological parameters and microbiological loads during 41 days of storage. Obtained results showed the greater ability of the new active packaging to decrease the oxidation kinetics of “pesto”, mainly when stored at 25 °C. Moreover, all samples packed in the activated biodegradable pouches (both sunflower oils stored at 35 °C and pesto stored at 25 °C) showed better and more stable quality characteristics, in terms of colorimetric, microbiological and textural parameters when compared with the respective control samples. Overall obtained results highlighted the potentiality of the new biodegradable material, activated with the oxygen scavenger, to be applied successfully in food industry, to extend food products shelf-life and/or maintain high quality levels during storage.

Biobased ternary films of thermoplastic starch, bacterial nanocellulose and gallic acid for active food packaging

The use of active packaging technologies and biopolymeric materials are among the emerging trends for implementation of sustainability in the food packaging industry. Thus, herein, bioactive transparent nanocomposite films of thermoplastic starch (TPS) reinforced with bacterial nanocellulose (BNC) (1%, 5% and 10% w/w, relative to starch) and enriched with gallic acid (GA) (1 and 1.5% w/w, relative to starch) were prepared by the solvent casting method. The addition of BNC (≥5% w/w) and GA (1 and 1.5% w/w) enhanced both the mechanical properties (Young's Modulus: 1.2–2.0 GPa vs. 1.0 GPa for TPS; tensile strength: 23–39 MPa vs. 20 MPa for TPS) and the water resistance (moisture absorption and solubility in water) of the nanocomposites. All films are thermally stable up to 125 °C. It was also found that the addition of GA imparted the hydrocolloid TPS-BNC nanocomposites with UV-blocking properties and antioxidant activity (DPPH scavenging activity above 80%). In addition, the film with 10% w/w of BNC nanofibers and 1% w/w of GA had good oxygen barrier properties with a coefficient of permeability of 0.91 ± 0.12 cm3 μm m−2 d−1 kPa−1 and antibacterial activity against the gram-positive Staphylococcus aureus (reduction of about 4.5 log10 colony forming units (CFU) mL−1 after 48 h). This is the first time that antibacterial activity is reported for TPS-BNC nanocomposites. The film with 10% w/w of BNC nanofibers and 1% w/w of GA was further demonstrated to have the ability of delaying the browning and weight loss of packaged fresh cut apple stored at +4 °C for 7 days. All these outcomes are of great relevance for the packaging sector, thus attesting the potential of the developed TPS-BNC-GA nanocomposites as sustainable and eco-friendly film materials for active food packaging.

Organophosphorus Reinforced Poly(vinyl alcohol) Nanocomposites Doped with Silver-Loaded Zeolite L Nanoparticles as Sustainable Materials for Packaging Applications.

The sustainable development of innovative eco-friendly multifunctional nanocomposites, possessing superior characteristics, is a noteworthy topic. Novel semi-interpenetrated nanocomposite films based on poly(vinyl alcohol) covalently and thermally crosslinked with oxalic acid (OA), reinforced with a novel organophosphorus flame retardant (PFR-4) derived from co-polycondensation in solution reaction of equimolar amounts of co-monomers, namely, bis((6-oxido-6H-dibenz[c,e][1,2]oxaphosphorinyl)-(4-hydroxyaniline)-methylene)-1,4-phenylene, bisphenol S, and phenylphosphonic dichloride, in a molar ratio of 1:1:2, and additionally doped with silver-loaded zeolite L nanoparticles (ze-Ag), have been prepared by casting from solution technique. The morphology of the as prepared PVA-oxalic acid films and their semi-interpenetrated nanocomposites with PFR-4 and ze-Ag was investigated by scanning electron microscopy (SEM), while the homogeneous distribution of the organophosphorus compound and nanoparticles within the nanocomposite films has been introspected by means of energy dispersive X-ray spectroscopy (EDX). It was established that composites with a very low phosphorus content had noticeably improved flame retardancy. The peak of the heat release rate was reduced up to 55%, depending on the content of the flame-retardant additive and the doping ze-Ag nanoparticles introduced into the PVA/OA matrix. The ultimate tensile strength and elastic modulus increased significantly in the reinforced nanocomposites. Considerably increased antimicrobial activity was revealed in the case of the samples containing silver-loaded zeolite L nanoparticles.

A highly sensitive electrochemical sensor by growing Ag nanoparticles on the surface of PPy@PEDOT:PSS film for detecting sodium hydroxymethanesulfinate molecules.

A high-sensitivity electrochemical sensor was fabricated via in situ growth of Ag nanoparticles (AgNPs) on the surface of a polypyrrole@poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PPy@PEDOT:PSS) film for detecting sodium hydroxymethanesulfinate (SHF) molecules in milk and rice flour samples. The sensor fabrication process involved randomly decorating Ag seed points on the porous PPy@PEDOT:PSS film via a chemical reduction process using a AgNO3 solution. Next, AgNPs were anchored on the PPy@PEDOT:PSS film surface using an electrochemical deposition method to prepare a sensor electrode. Under optimal conditions, the sensor exhibits a good linear relation within a range of 1-130ng/mL for real milk and rice flour samples and its limit-of-detection values were up to 0.58 and 0.29ng/mL, respectively. Additionally, Raman spectroscopy was used to identify the byproducts of the chemical reaction, such as formaldehyde. This AgNP/PPy@PEDOT:PSS film-based electrochemical sensor offers a simple and rapid method for detecting SHF molecules in food products.

Sewage sludge induces changes in the surface chemistry and crystallinity of polylactic acid and polyethylene films

Plastic pollution is a major threat facing our environment. To understand the full effects, we must first characterize how plastics break down in environmental systems. Heretofore, there has been little work examining how exposure to sewage sludge facilitates the degradation of plastics, particularly of plastics that have been previously weathered. Herein, we characterize how the crystallinity, surface chemistry, and morphology of polylactic acid (PLA) and polyethylene (PE) films change due to sludge exposure. In this work, sludge-induced changes in carbonyl index were found to depend on the level of prior exposure to ultraviolet (UV) irradiation. The carbonyl indices of un-irradiated films increased while those of UV-aged films decreased after 35 days of sludge exposure. In addition, the carbon‑oxygen and hydroxyl bond indices of PE films increased with sludge exposure, suggesting the surface oxidation of PE. As for PLA, crystallinity was found to increase with sludge exposure, consistent with a chain scission mechanism. This work will help to predict the behavior of plastic films after transfer from wastewater to sewage sludge.

Asymmetric tri-layer sponge-nanofiber wound dressing containing insulin-like growth factor-1 and multi-walled carbon nanotubes for acceleration of full-thickness wound healing

To more closely resemble the structure of natural skin, multi-layered wound dressings have been developed. Herein, a tri-layer wound dressing was prepared containing a polyacrylamide (PAAm)-Aloe vera (Alo) sponge that had been incorporated with insulin-like growth factor-1 (IGF1) to provide a porous absorbent layer, which was able to promote angiogenesis. Alo nanofibers with multi-walled carbon nanotubes (MWCNT) were electrospun into the bottom layer to increase cell behavior, and a small film of stearic acid was put as a top layer to avoid germy penetration. In comparison to bilayer dressing, the tensile strength increased by 17.0 % (from 0.200 ± 0.010 MPa to 0.234 ± 0.022 MPa) and the elastic modulus by 45.6 % (from 0.217 ± 0.003 MPa to 0.316 ± 0.012 MPa) in the presence of Alo nanofibers containing 0.5 wt% of MWCNT at the bottom layer of Trilayer0.5 dressing. The release profile of IGF1, the antibacterial activity and the degradability of different wound dressings were investigated. Trilayer0.5 indicated the highest cell viability, cell adhesion and angiogenic potential among the prepared dressing materials. In-vivo rat model revealed that the Trilayer0.5 dressing treated group had the highest rate of wound closure and wound healing within 10 days compared to other groups.

Structure evolution of amorphous poly(d-lactic acid) on highly oriented poly(l-lactic acid) film during annealing

Stereocomplex (SC) of poly(lactide)s (PLAs) has attracted much attention owing to its superior properties, and thus been extensively studied for the poly(d-lactide)/poly(l-lactide) (PDLA/PLLA) blend through solution, melt and cold crystallizations. In this work, the structure evolution of layered samples containing an amorphous PDLA layer and a crystalline PLLA layer with highly oriented edge-on α lamellar crystals during annealing at 175 °C has been studied by AFM, electron diffraction and FTIR techniques. It has been found that edge-on PDLA lamellar crystals and both PLA SC edge-on lamellar crystals and flat-on single crystals in shapes of triangular (preferentially) and hexagonal (less pronounced) can form during annealing. The edge-on PDLA and PLA SC lamellar crystals are highly oriented with molecular chains of both PDLA and PLLA parallel to the chain direction of the used PLLA substrate, reflecting the growth of them take place on the crystalline regions of the PLLA substrate. On the other hand, the random orientation of the triangular flat-on SC single crystals with respect to the used PLLA substrate suggests that the growth of them have nothing to do with the oriented PLLA substrate. It is thus conjectured that the formation of SC single crystals is most likely started in the amorphous regions at places with rich loosely folded loops, chain ends, and even free standing random coils of the used PLLA substrate film.

Fabrication of Pulsatile Polymeric Microparticles Encapsulating Rabies Antigen.

The current guidelines for rabies post-exposure prophylaxis require multiple injections administered over several weeks. This can be disproportionately burdensome to those living in low- and middle-income countries (LMICs), where the majority of deadly exposures to rabies occur. Different drug delivery strategies have been explored to condense vaccine regimens to a single injection by encapsulating antigens into polymeric particles. However, harsh stressors during the encapsulation process can cause denaturation of the encapsulated antigen. This article describes a method for encapsulating the rabies virus (RABV) antigen into polymeric microparticles that exhibit tunable pulsatile release. This method, termed Particles Uniformly Liquified and Sealed to Encapsulate Drugs (PULSED), generates microparticles using soft lithography to create inverse polydimethylsiloxane (PDMS) molds from a multi-photon, 3D-printed master mold. Poly(lactic-co-glycolic acid) (PLGA) films are then compression-molded into the PDMS molds to generate open-faced cylinders that are filled with concentrated RABV using a piezoelectric dispensing robot. These microstructures are then sealed by heating the top of the particles, allowing the material to flow and form a continuous, nonporous polymeric barrier. Post-fabrication, an enzyme-linked immunosorbent assay (ELISA) specific to the detection of intact trimeric rabies virus glycoprotein is used to confirm the high recovery of immunogenic antigen from the microparticles.

On the Effect of Monomeric and Polymeric Plasticizer on Polybutylene Succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic Acid (PLA) Films with 20wt%PCL for Flexible Packaging Application

Nowadays, biodegradable polymers such as Polybutylene succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic acid (PLA) are widely used commercially, especially in flexible packaging applications, but these polymers have certain limitations in their properties. The main aim of this study was to develop biodegradable polymer films with improved performance characteristics. This paper focused on developing and enhancing the characterization such as tensile properties, water barrier properties, and biodegradation properties of PBS-PCL(Polycaprolactone), PHB-PCL, and PLA-PCL blends, with the addition of 5wt% of plasticizer [GTA (Triacetin/ glycerol triacetate), a monomeric plasticizer P1, Ultramoll, a polymeric plasticizer P2; and mixed plasticizer P3 (1: 1 mix of P1 and P2)] for flexible packaging application. The plasticized polymer films (thickness 0.25mm) was prepared by injection molding and hot pressing method, and analyze the characterization such as tensile properties (ASTM D882-18 method), water vapor barrier properties (ASTM E96-16 method), and the biodegradation properties in compost (ASTM D5338-15 method), and seawater (ASTM D6991-17 method) medium, and analysis the effect of plasticizers on plasticized polymer blends. The research shows that compared to polymers blends such as PBS, PHB, and PLA, with 20wt% of PCL, there was a significant increase in tensile elongation by 22%,76.6%, and 139.3%, respectively and an increase in biodegradability by 19.5%, 3.6%, and 38.9% in compost medium, and 22.1%, 1.8%, and 41.0% in seawater medium, respectively, with the addition of all three 5wt% plasticizers (Ultramoll), though the tensile strength and water vapor properties were decreased. The plasticizer study shows that plasticized polymer blends using mixed plasticizer (P3) provide the best overall performance enhancement.

Property Improvement of Polybutylene Succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic Acid (PLA) Films with PCL (Polycaprolactone) for Flexible Packaging Application

Nowadays, developing highly biodegradable polymer films for flexible packaging applications is one of many researchers' demanding and challenging tasks. Conventional plastics/polymers are still being extensively used, creating environmental pollution. Because most of the commercially available plastic products are marketed as biodegradable are not truly biodegradable and have several limitations for making flexible packaging films. The main objective of this work is to manufacture biodegradable polymer blends, with the best performance characteristics, for flexible packaging applications. The paper focused on improving the properties, i.e., tensile, barrier, and biodegradation properties, of commercially available polymers such as Polybutylene succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic acid (PLA) by blending with Polycaprolactone (PCL) for flexible packaging application. Polymer films of various compositions such as PBS-PCL, PHB-PCL, and PLA-PCL blends were fabricated by injection molding and hot pressing. The characterization analysis included analyzing polymer blends' tensile and water vapor barrier properties, as per ASTM D882-18 method and ASTM E96-16 method, respectively, following that biodegradation analysis in compost (ASTM D5338-15 method) and seawater medium (ASTM D6991-17 method) of the polymer blends, and analysis of PCL blends' effect. The research showed that compared to the pure polymer blends such as PBS, PHB, and PLA blends, polymer blends with 20% of PCL has increased tensile elongation by 26.3%, 68%, and 171%, respectively, and the water vapor barrier properties were increased by 28.3%, 26.8%, and 30.3%. the biodegradation rate in compost medium was increased by 21.9%, 6.4% and 21.2%, and the biodegradation rate in seawater medium was increased by 31%, 7.5%, and 16.6%, respectively, even though a slight decrease in tensile strength. In conclusion, the polymer blends with 20wt% of PCL provide overall improved of polymer properties.

PLA Films Containing Montmorillonite Nanoclay–Citronella Essential Oil Hybrids for Potential Active Film Formulation

This work evaluated the synergistic effect of citronella essential oil (Ct) and montmorillonite (MMT) (called hybrid compound) incorporated in Poly(lactic acid) (PLA) films at different concentrations (3, 10, 15, and 20 wt%). PLA films were characterized using X-ray diffraction, SEM, TGA, and DSC considering their mechanical properties and essential oil migration. XRD analysis showed the effective interaction between MMT and oil. Thermal analysis, SEM, and mechanical tests were essential to understand the saturation point of the PLA composites. Samples with 15% and 20% of Ct showed a crystallinity reduction of 0.5% compared to samples with 3% and 10% of Ct. PLA/MMT–Ct showed a reduction in tensile strength of the order of 16 and 24, correlated to 15% and 20% of the Ct content, respectively, compared to PLA/MMT–Ct3%. Migration tests showed fast oil delivery correlated with high oil concentration, as evidenced using the PLA/MMT–Ct20% sample results, which showed an estimated release of 50% in the first 150 h due to system saturation, and the remaining being released in the last 350 h. Therefore, the migration tests provide an effective Ct concentration range promising for application with active packaging due to the intrinsic antimicrobial properties of Ct.

Photo-aged non-biodegradable and biodegradable mulching film microplastics alter the interfacial behaviors between agricultural soil and inorganic arsenic

The impacts of microplastics (MPs) prevalent in soil on the transport of pollutants were urged to be addressed, which has important implications for ecological risk assessment. Therefore, we investigated the influence of virgin/photo-aged biodegradable polylactic acid (PLA) and non-biodegradable black polyethylene (BPE) mulching films MPs on arsenic (As) transport behaviors in agricultural soil. Results showed that both virgin PLA (VPLA) and aged PLA (APLA) enhanced the adsorption of As(Ⅲ) (9.5%, 13.3%) and As(Ⅴ) (22.0%, 6.8%) due to the formation of abundant H-bonds. Conversely, virgin BPE (VBPE) reduced the adsorption of As(Ⅲ) (11.0%) and As(Ⅴ) (7.4%) in soil owing to the “dilution effect”, while aged BPE (ABPE) improved arsenic adsorption amount to the level of pure soil due to newly generated O-containing functional groups being feasible to form H-bonds with arsenic. Site energy distribution analysis indicated that the dominant adsorption mechanism of arsenic, chemisorption, was not impacted by MPs. The occurrence of biodegradable VPLA/APLA MPs rather than non-biodegradable VBPE/ABPE MPs resulted in an increased risk of soil accumulating As(Ⅲ) (moderate) and As(Ⅴ) (considerable). This work uncovers the role of biodegradable/non-biodegradable mulching film MPs in arsenic migration and potential risks in the soil ecosystem, depending on the types and aging of MPs.

Microbiota Assessment of Fresh-Cut Apples Packaged in Two Different Films.

The aim of this work was to assess the natural microbiota of packed fresh-cut apples during refrigerated storage. Two different films were tested for the package, a biodegradable (PLA) film and a conventional and commercial one (OPP). Two antioxidant additives were applied, a natural olive pomace extract and the commercial ascorbic acid used by the industries. The results revealed lower bacteria counts in samples with olive pomace extract and PLA films than in those with ascorbic acid and OPP films after 5 and 12 days of storage. These findings suggest that the use of such natural extracts as additives in fruits could delay the growth of mesophilic bacteria. The characterization and identification of the bacterial isolates from fresh-cut apple samples showed that the most prevalent species were Citrobacter freundii, Staphylococcus warneri, Pseudomonas oryzihabitans, Alcalinogenes faecalis, Corynebacterium jeikeium, Micrococcus spp., Pantoea aglomerans and Bacillus spp. Furthermore, an increase in the microbial diversity during the storage time at refrigerated temperatures was observed, except for the sample treated with olive pomace extract and packaged in OPP film. The highest microbial diversity was found for samples with ascorbic acid as an additive. This could indicate a negative effect of ascorbic acid on the microbial inhibition of apple slices. The natural olive pomace extract demonstrated potential as an antimicrobial additive for fresh-cut apples.

Effect of Fatty Acids with Different Chain Lengths and Degrees of Unsaturation on Film Properties of Potato Starch-Fatty Acids Films for Chicken Packaging

Effect of Fatty Acids with Different Chain Lengths and Degrees of Unsaturation on Film Properties of Potato Starch-Fatty Acids Films for Chicken Packaging

Infrared Reflection-Absorption Spectroscopy of α-Keto Acids at the Air-Water Interface: Effects of Chain Length and Headgroup on Environmentally Relevant Surfactant Films.

A variety of organic surfactants are found at air-water interfaces in natural environments, including on the surfaces of aqueous aerosols. The structure and morphology of these organic films can have profound impacts on material transfer between the gas and condensed phases, the optical properties of atmospheric aerosol, and chemical processing at air-water interfaces. Combined, these effects can have significant impacts on climate via radiative forcing, but our understanding of organic films at air-water interfaces is incomplete. Here, we examine the impact of the polar headgroup and alkyl tail length on the structure and morphology of organic monolayers at the air-water interfaces. First, we focus on the substituted carboxylic acids, α-keto acids, using Langmuir isotherms and infrared reflection absorption spectroscopy (IR-RAS) to elucidate key structures and phase behaviors of α-keto acids with a range of surface activities. We show that the structure of α-keto acids, both soluble and insoluble, at water surfaces is a compromise between van der Waals interactions of the hydrocarbon tail and hydrogen bonding interactions involving the polar headgroup. Then, we use this new data set regarding α-keto acid films at water surfaces to examine the role of the polar headgroup on organic films using a similar substituted carboxylic acid (α-hydroxystearic acid), an unsubstituted carboxylic acid (stearic acid), and an alcohol (stearyl alcohol). We show that the polar headgroup and its hydrogen bonding interactions can significantly affect the orientation of amphiphiles at air-water interfaces. Here, we provide side-by-side comparisons of Langmuir isotherms and IR-RA spectra for a set of environmentally relevant organic amphiphiles with a range of alkyl tail lengths and polar headgroup structures.

Lesser galangal (Alpinia officinarum Hance) essential oil incorporated biodegradable PLA/PBS films as shelf-life extension packaging of cooked rice

Adding natural essential oils to biodegradable polymers produces functional active packaging that reduces food loss and package waste. Polylactic acid and polybutylene succinate (PLA/PBS) films were produced via cast extrusion and blended with lesser galangal (Alpinia officinarum Hance.) essential oils (EO) at up to 6 %. Effects of EO and PLA/PBS ratios on morphology, relaxation, crystallinity and film properties were investigated. Results indicated that plasticization effects of EO reduced α-relaxation temperature and crystallinity, decreasing tensile strength by up to 22 %, while permeability of water vapor and oxygen increased by up to 42 % and 29 %, respectively. Interaction between EO and PLA/PBS shifted the diffraction angle, suggesting modified crystal morphology. EO enhanced melting of PBS giving smoother microstructures and reduced aggregates in the film matrices, contributing to lower surface roughness and hydrophobicity. Films were placed into packages of freshly steamed glutinous rice, allowing release of volatile lesser galangal EO majorly consisted of β-ocimene, 2-bornanone, eucalyptol and geraniol as determined by GC/MS. PLA/PBS films with lower PLA contents containing EO showed higher efficacy to delay fungal growth in cooked glutinous rice. Total microbial viable counts were significantly lower in packages containing EO above 4 %. PLA/PBS/EO films effectively extended the shelf-life of cooked glutinous rice by more than 2-fold depending on EO concentrations and PLA/PBS ratios due to release of volatiles into the headspace. Essential oil release from film interface into vapor and liquid phases showed antimicrobial functions which delayed mold and bacterial growth.

Smart Antibacterial Food Packaging Based on MIL-53 (Fe) Functionalized Polylactic Acid Film for pH-Responsive Controlled Release

Smart Antibacterial Food Packaging Based on MIL-53 (Fe) Functionalized Polylactic Acid Film for pH-Responsive Controlled Release

Active Poly (Lactic Acid) Films with Rice Straw Aqueous Extracts for Meat Preservation Purposes

Aqueous extracts from rice straw (RS), using ultrasound-assisted reflux heating extraction (USHT) and subcritical water extraction (SWE), under two process conditions (160 °C, 7 bars; and 180 °C, 11 bars), were obtained and characterised as to their phenolic content and antioxidant and antimicrobial capacities. These extracts were incorporated (6% wt.) into poly (lactic acid) (PLA) films by melt blending and compression moulding that were characterised as to their structural and functional properties and their capacity to preserve fresh pork meat, as vacuum thermo-sealed bags, throughout 16 days of cold storage. The extracts slightly reduced the extensibility, resistance to break, and water barrier capacity of the PLA films but enhanced their oxygen barrier capacity and the UV light-blocking effect. The films with RS extracts were effective at preserving meat quality parameters, inhibiting microbial growth, meat oxidation, discolouration, and weight loss. The SWE extract obtained at 180 °C was the most effective at obtaining active films for meat preservation, exhibiting the greatest antioxidant and antibacterial activity. Therefore, the green SWE technique is useful for obtaining active extracts from RS, allowing for its valorisation in the development of biodegradable active materials useful to preserve food quality.

Poly(l‐Lactic Acid) Nanofiber‐Based Multilayer Film for the Electrical Stimulation of Nerve Cells

AbstractPoly(l‐lactic acid) (PLLA) films have excellent piezoelectric properties, but the strong hydrophobicity of the surface makes it difficult for cells to attach there. PLLA nanofibers have good biocompatibility, but the weak piezoelectric coefficient limits the ability of the nanofibers to stimulate cell growth. Therefore, the PLLA piezoelectric film is combined with the PLLA nanofibers to make a multilayer film. In our tests, the piezoelectric output of the multilayer film ≈260 mV. In the biological experiments section, without piezoelectric stimulation, the cell length on the nanofibers is approximately twice that of the cells in the blank control group. The length of cells cultured on piezoelectric‐based stimulated nanofibers is more than twice that of cells cultured on nanofibers without piezoelectric stimulation. Therefore, it is confirmed that under the dual action of nanofiber guidance and piezoelectric stimulation, the growth rate of cells is four times faster than that in ordinary Petri dishes. Intracellular calcium imaging experiments confirmed that the concentration of Ca2+ in electrically stimulated cells is approximately twice that of ordinary cells. It is also confirmed that piezoelectric materials can complete electrical stimulation of cells in indirect contact with cells.