PHBV Films Research Articles

Remote Activation of Antimicrobial Properties via Magnetoeletric Stimulation of Biopolymer‐Based Nanocomposites

AbstractAntimicrobial materials are crucial for high‐touch surfaces to prevent the adhesion and proliferation of microorganisms, playing a key role in infection control measures. In this work, a magnetoelectric nanocomposite able to exert antimicrobial activity when magnetically stimulated, is obtained by solvent casting. The nanocomposites, composed of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) and cobalt ferrite magnetostrictive nanoparticles (CFO NPs), respond to a variable magnetic field by mechanically stimulating the piezoelectric component of the material, thereby inducing an electrical polarization. The antimicrobial properties of the material are determined by exposing it to different frequencies (0.3 and 1 Hz) using a custom‐designed magnetic bioreactor, where the resulting electrical microenvironments are the contributing factor. The growth of Escherichia coli and Staphylococcus aureus over the nanocomposite is highly inhibited when magnetically stimulated (dynamic conditions) mainly at 0.3 Hz, in contrast to static conditions. The electric microenvironment is further measured upon magnetic stimulation, with PHBV films with 20% CFO inducing a voltage variation of ≈20 µV at the surface while the films with 10% CFO induced a voltage variation of ≈12 µV. This work demonstrated that magnetic stimulation, combined with magnetoelectric materials, can be used for remote antimicrobial control, thus preventing the spread of infections.

Investigating the impact of active PHBV films on the nutritional quality of minimally processed apples

The aim of the study was to study the effect of an active film, a blend of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with a derivative of ferulic acid known as bis-O-dihydroferuloyl-1,4-butanediol (BDF), on the quality decay kinetic of minimally processed apples. Due to its properties, BDF is a promising candidate to serve both as a non-toxic biobased plasticizer and as an active additive, simplifying formulation of active packaging. Molecular modelling studies were conducted to explore the interaction between polyphenol oxidase (PPO) and BDF molecule, with the aim of understanding the mechanism of inhibition. The apple slices packed in different treatments exhibited an increase in PPO activity; however, the samples packed in active films showed a significantly slower rate of PPO activity (P < 0.05). Almost 50% of the ascorbic acid content degraded in the control samples (4.95–4.97 mg/100 g fruit weight (FW)) at d7 compared with the samples packaged in BDF-releasing films (5.81–6.1 mg/100 g FW) in which the degradation was only 30%. Using molecular modelling, it was observed that BDF (−6.3 kcal/mol) exhibited a stronger interaction with PPO than catechol (−4.5 kcal/mol) in the met and oxy states. BDF-releasing films showed superior preservative potential over the control as BDF competitively inhibits the PPO active site due to π–π stacking between the aromatic cycle of the BDF molecule and the PHE259 and hydrogen bonding with the active site.

Tailored antimicrobial PHBV-based packaging for extended shelf life of processed cheese

A coupled experimental and modelling approach was used to develop an adapted PHBV active film with Lauroyl Arginate Ethyl (LAE®) as an antimicrobial compound incorporated in the bulk or as a coating to prolong the shelf life of cheese. The minimum inhibitory concentration (MIC) of LAE® was evaluated in the range of 25–100 ppm against spoilage and pathogenic microorganisms, such as Micrococcus luteus, Penicillium roqueforti, Salmonella enteritidis, and Pseudomonas putida. Film production induced a loss of 50 % of LAE® when introduced into the bulk, whereas only 4 % was lost in the case of incorporation by coating. When in contact with food simulant D1 (50 % ethanol), a release of 43 % and 34 % of LAE® was achieved in 10 days at 20 °C for LAE® incorporated as a coating and in the bulk, respectively, while a lower release level of 34 % and 14 % respectively was observed in food simulant C (20 % ethanol), confirming the interest to use active coating for fatty foods. The developed packaging was well adapted to reach the MIC while remaining below the admissible daily intake. The results also showed that the PHBV film activated with LAE® incorporated as a coating was as effective as modified atmosphere packaging (MAP) to preserve cheese against microorganism growth.

Biodegradation behavior of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) containing phenolic compounds in seawater in laboratory testing conditions

Biodegradation in marine medium of PHBV films with or without 5 % wt. of phenolic compounds (catechin, ferulic acid, and vanillin) was assessed at laboratory scale. Respirometric analyses and film disintegration kinetics were used to monitor the process over a period of 162 days. Structural changes in the films were analyzed throughout the exposure period using FESEM, DSC, Thermogravimetric analyses, XRD, and FTIR spectra. Respirometric tests showed complete biodegradation of all materials during the exposure period (the biodegradation half-time ranged between 63 and 79 days) but at different rates, depending on the phenolic compound incorporated. Ferulic acid and vanillin accelerate the PHBV biodegradation, whereas catechin delayed the process. Disintegration kinetics confirmed these results and showed that degradation occurred from the surface to the interior of the films. This was controlled by the degradation rate of the polymer amorphous phase and the formation of a biomass coating on the film surface. This is the result of the compounds generated by polymer degradation in combination with excretions from microorganisms. This coating has the potential to affect the enzyme diffusion to the polymer substrate. Moreover, the cohesion forces of the amorphous phase (reflected in its glass transition temperature) affected its degradation rate, while the slower degrading crystalline fragments were released, thus contributing to the disintegration process on the film's surface. Ferulic acid, with its hydrolytic effect, enhanced degradation, as did vanillin for its plasticizing and weakening effect in the amorphous phase of polymer matrix. In contrast, catechin with cross-linking effect hindered the progress of the material degradation, considerably slowing down the process rate.

Active Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Films Containing Phenolic Compounds with Different Molecular Structures.

To obtain more sustainable and active food packaging materials, PHBV films containing 5% wt. of phenolic compounds with different molecular structures (ferulic acid, vanillin, and catechin) and proved antioxidant and antimicrobial properties were obtained by melt blending and compression molding. These were characterized by their structural, mechanical, barrier, and optical properties, as well as the polymer crystallization, thermal stability, and component migration in different food simulants. Phenolic compounds were homogenously integrated within the polymer matrix, affecting the film properties differently. Ferulic acid, and mainly catechin, had an anti-plasticizing effect (increasing the polymer glass transition temperature), decreasing the film extensibility and the resistance to breaking, with slight changes in the elastic modulus. In contrast, vanillin provoked a plasticizing effect, decreasing the elastic modulus without notable changes in the film extensibility while increasing the water vapor permeability. All phenolic compounds, mainly catechin, improved the oxygen barrier capacity of PHBV films and interfered with the polymer crystallization, reducing the melting point and crystallinity degree. The thermal stability of the material was little affected by the incorporation of phenols. The migration of passive components of the different PHBV films was lower than the overall migration limit in every simulant. Phenolic compounds were released to a different extent depending on their thermo-sensitivity, which affected their final content in the film, their bonding forces in the polymer matrix, and the simulant polarity. Their effective release in real foods will determine their active action for food preservation. Catechin was the best preserved, while ferulic acid was the most released.

A novel adjustable PHBV basement film for enhancing the efficacy of glaucoma surgery by inhibiting scar formation

Trabeculectomy is the primary surgical approach used to treat glaucoma, but scarring of the filtering passage (filtering bleb) after surgery often leads to treatment failure. To address this issue, we have developed a drug release system called RSG/Pd@ZIF-8 PHBV film. This system enables the sustained release of an anti-fibrosis drug, aiming to prevent scarring. In vitro, the film has the function of continuous Rosiglitazone (RSG) release, with accelerated release after laser irradiation. The antibacterial experiments revealed that the film exhibited antibacterial rates of 87.0 % against E.coli and 97.1 % against S.aureus, respectively. Moreover, we confirmed its efficacy in a rabbit eye model undergoing trabeculectomy. After implantation of the film, we observed a prolonged postoperative period for reducing intraocular pressure (IOP), increased survival rate of filtering blebs, and improved long-term surgical outcomes in vivo. Additionally, the film exhibited excellent biosafety. In summary, the designed sustained-release film in this study possesses the aforementioned functionalities, allowing for the regulation of anti-scarring drug release without causing harm post-surgery. This personalized and precise anti-scarring strategy represents a significant advancement.

Surface modification of aligned electrospun poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-based scaffold for binding with fibronectin or collagen in vascular tissue engineering

BackgroundVascular diseases are a leading cause of morbidity and mortality worldwide. The combination of the natural polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with essential extracellular matrix proteins such as fibronectin (FN) or collagen (COL) using various methods (coating, grafting and air plasma) to create small-diameter vascular grafts holds significant promise in the field of vascular tissue engineering. MethodsThe final data from this study indicated that after conjugation, the films maintained a smooth surface area and preserved morphology. Endothelial progenitor cells (EPCs) and human umbilical vein endothelial cells (HUVECs) were employed to assess the cytotoxicity, biocompatibility, and proliferation potential of cell lines treated with the synthesized films. The FN-binding PHBV and COL-binding PHBV films exhibited remarkable cell biocompatibility and cell proliferation rates. Furthermore, the treated cells exhibited specific gene expressions, including VEGFR-2, vWF, CD31, CD34, and CD133. Additionally, at specified time points, the cell retention rate and anti-coagulation ability of EPCs and HUVECs cultured on various PHBV films were tested, yielding successful outcomes. Significant findingsThe results suggested that FN-binding PHBV films represent an ideal bio-based polymer for applications in vascular tissue engineering.

Relation of 3HV fraction and thermomechanical properties of poly(3–hydroxybutyrate–co–3–hydroxyvalerate) produced by Azotobacter vinelandii OP

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has attracted substantial attention as a promising material for industrial applications. In this study, different PHBV films with distinct 3-hydroxyvalerate (3HV) contents produced by Azotobacter vinelandii OP were evaluated. The 3HV fraction ranged from 18.6 to 36.7 mol%, and the number-average molecular weight (Mn) was between 238 and 434 kDa. In the bioreactor, a 3HV fraction (36.7 mol%) and an Mn value of 409 kDa were obtained with an oxygen transfer rate (OTR) of 12.5 mmol L−1 h−1. Thermal analysis measurements showed decreased melting (Tm) and glass transition (Tg) temperatures, and values with relatively high 3HV fractions indicated improved thermomechanical properties. The incorporation of the 3HV fraction in the PHBV chain improved the thermal stability of the films, reduced the polymer Tm, and affected the tensile strength. PHBV film with 36.7 mol% 3HV showed an increase in its tensile strength (51.8 MPa) and a decrease in its Tm (170.61 °C) compared with PHB. Finally, scanning electron microscopy (SEM) results revealed that the PHBV film with 32.8 mol% 3HV showed a degradation upon contact with soil, water, or soil bacteria, showing more porous surfaces after degradation. The latter phenomenon indicated that thermomechanical properties played an important role in biodegradation.

Release and antibacterial action of phenolic acids incorporated into PHBV films

Ferulic or p-coumaric acids were incorporated (3, 6 or 9%) into PHBV films by melt processing or surface anchoring (3–4% in the film). The release kinetics of phenolics and the films’ antibacterial effect against Escherichia coli and Listeria innocua were analysed. At equilibrium, a near 100% release of phenolics was obtained from melt processed films in a low polar simulant (D1: 50% v/v ethanol in water), whereas it ranged between 10% and 38% in a more polar simulant (A: 10% v/v ethanol in water). The diffusion coefficient of FA or PCA in the matrix also rose by 4–30 times in contact with simulant D1. The limited release of the phenolics in contact with aqueous systems hindered the film’s antibacterial effect in contact with the inoculated culture media. In contrast, surface-loaded films exhibited a complete release of phenolics in aqueous media and a significant (near 2 log CFU) bacterial growth inhibition.

Electrospun hybrid TiO2/humic substance PHBV films for active food packaging applications

Sustainable packaging materials can play a key role in minimizing the environmental footprint of packaged food by preserving its quality and avoiding environmental persistence of plastic waste. Waste to wealth approach can cope with these major challenges by providing for bioavailable active compounds from waste residues. To this regard, humic substances (HS), derived from biowaste oxidative processes, exhibit intrinsic antioxidant and antimicrobial features, which can be significantly boosted by molecular combination with an inorganic nanostructured phase.Herein, this approach has been integrated with the electrospinning technology to design composite films made of electrospun biodegradable and bioderived polymers filled with nanostructured hybrid HS based materials.Therefore, electrospun composites made by including hybrid TiO2_HS nanostructures into PHBV matrix were first produced and then converted into homogeneous and continuous films to obtain an active layer which will be part of a multilayer food packaging solution. These were characterized in terms of morphology, thermal, crystallinity, optical, mechanical and barrier properties as well as antimicrobial performance against Staphylococcus aureus and Escherichia coli, two main strains of food pathogens.Theresults suggested that the combination of hybrid nanomaterials with electrospinning methodology is a promising and sustainable approach to convert biowaste into multifunctional materials for active packaging.

The Structural Evolution of β-to-α Phase Transition in the Annealing Process of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate).

In this study, the structural and property changes induced in the highly ordered structure of preoriented poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV films containing the β-form during annealing were investigated. The transformation of the β-form was investigated by means of in situ wide-angle X-ray diffraction (WAXD) using synchrotron X-rays. The comparison of PHBV films with the β-form before and after annealing was performed using small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The evolution mechanism of β-crystal transformation was elucidated. It was revealed that most of the highly oriented β-form directly transforms into the highly oriented α-form, and there might be two kinds of transformations: (1) The β-crystalline bundles may be transformed one by one rather than one part by one part during annealing before a certain annealing time. (2) The β-crystalline bundles crack or the molecular chains of the β-form are separated from the lateral side after annealing after a certain annealing time. A model to describe the microstructural evolution of the ordered structure during annealing was established based on the results obtained.

Piezoelectric and Magnetically Responsive Biodegradable Composites with Tailored Porous Morphology for Biotechnological Applications.

The biomedical area in the scope of tissue regeneration pursues the development of advanced materials that can target biomimetic approaches and, ideally, have an active role in the environment they are placed in. This active role can be related to or driven by morphological, mechanical, electrical, or magnetic stimuli, among others. This work reports on the development of active biomaterials based on poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid), PHBV, a piezoelectric and biodegradable polymer, for tissue regeneration application by tailoring its morphology and functional response. PHBV films with different porosities were obtained using the solvent casting method, resorting to high-boiling-point solvents, as N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO), and the combination of chloroform (CF) and DMF for polymer dissolution. Furthermore, magnetoelectric biomaterials were obtained through the combination of the piezoelectric PHBV with magnetostrictive iron oxide (Fe3O4) nanoparticles. Independently of the morphology or filler content, all biomaterials proved to be suitable for biomedical applications.

New sustainable routes for gas separation membranes: The properties of poly(hydroxybutyrate-co-hydroxyvalerate) cast from green solvents

The gas separation performance of biopolymers is still scarcely characterized, mostly because of their poor thermomechanical properties and high crystallinity which is associated to low permeability. In this work we characterize the gas transport in a poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) random copolymer, that has a relatively low crystallinity and good mechanical properties, combined with a renewable origin, biodegradability and biocompatibility. In the study we also compared several solvents for membrane casting, with different toxicity levels. We found that dimethyl carbonate allows the production of polymer films with transport properties similar to those obtained with the more toxic CHCl3, and it leads also to stable crystallinity of the samples over time. PHBV films show a size-sieving gas separation behaviour, as the permeability decreases significantly with the gas kinetic diameter. However, the strong energetic interactions of CO2 with the polymer matrix, confirmed by the Flory-Huggins model, induce a marked solubility-driven CO2/N2 and CO2/CH4 selectivity, which could make the material potentially interesting for CO2 removal processes.

In vitro evaluation of porous poly(hydroxybutyrate-co-hydroxyvalerate)/akermanite composite scaffolds manufactured using selective laser sintering.

Incorporation of a bioactive mineral filler in a biodegradable polyester scaffold is a promising strategy for scaffold assisted bone tissue engineering (TE). The current study evaluates the in vitro behavior of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/Akermanite (AKM) composite scaffolds manufactured using selective laser sintering (SLS). Exposure of the mineral filler on the surface of the scaffold skeleton was evident from in vitro mineralization in PBS. PHBV scaffolds and solvent cast films served as control samples and all materials showed preferential adsorption of fibronectin compared to serum albumin as well as non-cytotoxic response in human osteoblasts (hOB) at 24h. hOB culture for up to 21days revealed that the metabolic activity in PHBV films and scaffolds was significantly higher than that of PHBV/AKM scaffolds within the first two weeks of incubation. Afterwards, the metabolic activity in PHBV/AKM scaffolds exceeded that of the control samples. Confocal imaging showed cell penetration into the porous scaffolds. Significantly higher ALP activity was observed in PHBV/AKM scaffolds at all time points in both basal and osteogenic media. Mineralization during cell culture was observed on all samples with PHBV/AKM scaffolds exhibiting distinctly different mineral morphology. This study has demonstrated that the bioactivity of PHBV SLS scaffolds can be enhanced by incorporating AKM, making this an attractive candidate for bone TE application.

Physical-Chemical and Structural Stability of Poly(3HB-co-3HV)/(ligno-)cellulosic Fibre-Based Biocomposites over Successive Dishwashing Cycles.

In order to lengthen the life cycle of packaging materials, it is essential to study their potential for reuse. This has been never carried out for emerging bio-based and biodegradable materials such as PHBV/(ligno-)cellulosic fibre-based biocomposite materials. This work therefore highlights the impact of successive dishwashing cycles on the physical-chemical and structural stability of such materials. Several parameters were considered to assess this stability, such as the visual aspect and colour, the microstructure, the thermal and tensile properties, and the overall migration in food liquid simulants. The effect of fibre composition, morphology, and content was investigated by selecting three types of commercial (ligno-)cellulosic fibres and two filler contents (20 and 40 wt%). A great potential for reuse of PHBV films was highlighted by their high stability after up to at least 50 dishwashing cycles. However, the addition of (ligno-)cellulosic fillers negatively impacts the stability of PHBV-based materials, especially due to the hygroscopic behaviour of (ligno-)cellulosic fillers and the heterogenous microstructure of biocomposites, with at best up to 10 possible dishwashing cycles for ultra-pure cellulose. In conclusion, reuse including dishwashing steps can be considered for neat PHBV materials, while this should be prohibited for PHBV/(ligno-)cellulosic fibre-based biocomposite materials.

Activated gallic acid as radical and oxygen scavenger in biodegradable packaging film

A coupled experimental and modelling approach was developed to characterize the radical inhibition and oxygen scavenger properties of gallic acid/ sodium carbonate mixture included in a PHBV film. PHBV active packaging was produced by thermoforming. In contact with acqueous and fatty food simulants, almost 30% of the initial gallic acid was released into food simulants A (10% ethanol), and D1 (50% ehtanol), where it showed a radical inhibition value (I%) reaching 68 ± 0.1% and 77 ± 0.1% respectively, while no release was observed in food simulant D2 (isooctane). In addition, the active films displayed an O2 scanvenger capacity of 120 mg O2 g−1 GA at room temperature, after 10 days of storage. Models showed a good fitting to experimental data. The PHBV active packaging combining both antiradical and oxygen scavenger activities has high potential for food protection. However, some improvements are still needed to enhance its oxygen barrier capacity and to meet the reglementation.

Release of oregano essential oil from PHBV films in simulated food conditionsa

Poly(hydroxybutyrate-co-hydroxyvalerate) – PHBV plays an important role in sustainability and food safety. In this work, active packaging with antimicrobial properties was analyzed for the controlled release of active compound in three environments (acidic aqueous foods, fresh foods, and fatty foods). The compositions were produced with the addition of sepiolite nanoparticles (Sep) and oregano essential oil (OEO). The GC-MS analysis detected the presence of 3-methyl-4-isopropyl phenol as the primary constituent of the OEO (71.7%). The characterization of the films by FTIR and SEM confirmed the presence of additives, and the quantification of OEO and thermal stability of the nanocomposites was verified by TGA. Four kinetic models were used to analyze the release profile. Our findings indicate that it is possible to adjust the kinetic release of the OEO by varying the composition of the films, which is a promising alternative for producing an antibacterial biomaterial for application in food packaging.

Thermal and Barrier Characterizations of Cellulose Esters with Variable Side-Chain Lengths and Their Effect on PHBV and PLA Bioplastic Film Properties.

Cellulose esters (CEs) are promising biodegradable substitutes for traditional petroleum-based plastic materials. Research on structure–property relationships of CEs is necessary to evaluate their suitability for industrial applications such as food packaging. Cellulose esters with different side-chain lengths were synthesized and studied. Their thermal and moisture barrier properties were characterized. Cellulose triheptanoate (CTH) was proved to have an optimal moisture barrier (WVTR = 0.31 g·mil/day/in.2) and was used to blend with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactic acid (PLA) bioplastics. CTH addition improved the PLA thermal stability, enhanced the ductility, and increased the moisture barrier by 32%, while it decreased the PHBV thermal stability, weakened the ductility, and reduced the moisture barrier by 90%. We demonstrated that by proper choice of the combination of CE and bioplastic, bioplastic blends with unique and useful synergistic properties can be obtained. These blends can potentially be used for commercial applications, such as biodegradable flexible packaging.

Effects of talc, kaolin and calcium carbonate as fillers in biopolymer packaging materials

AbstractWe compared the performance of bio-based and biodegradable polymers for packaging applications. Cost-effective inorganic fillers (talc, kaolin and calcium carbonate) were first melt-compounded with polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and poly(hydroxy butyrate-co-valerate) (PHBV). Following this, injection- and compression-molded specimens were produced to test the effect of filler loading (0–30 wt%) in relation to the morphological, thermal, mechanical and barrier properties of the composites. All the fillers were homogeneously dispersed in the polymer matrices and suitable polymer–filler adhesion was observed for talc and kaolin. The elastic modulus increased at the expense of a reduced tensile and elongation. The most significant improvements in water vapor and oxygen barrier properties were achieved with talc in PLA, PBAT and PHBV films. Overall, the results point to the promise of the introduced compositions for food packaging materials.

Impact of the processing temperature on the crystallization behavior and mechanical properties of poly[R-3-hydroxybutyrate-co-(R-3-hydroxyvalerate)

Poly[R-3-hydroxybutyrate-co-(R-3-hydroxyvalerate)] (PHBVs) are promising biopolymers, which could substitute petro-based plastics for packaging applications. To anticipate the behavior of PHBVs when transformed using conventional thermo-mechanical shaping processes, it is needed to better understand the effect of processing temperature on their crystallization behavior and final properties. The objectives of the present work were thus (1) to better understand the influence of the processing temperature on the PHBV macromolecular and crystalline structures, depending on its HV content, and (2) to define a processing window guaranteeing optimized mechanical properties of PHBV films. An innovative experimental strategy was proposed, enabling the study of melting and crystallization events, crystalline structure changes, and evolution of mechanical properties of PHBV according to processing temperature, using identical thermal cycles. A comprehensive dynamic monitoring of the studied PHBVs was achieved by coupling differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), step scan DSC (SDSC), observations of isothermal crystallization under polarized optical microscopy (POM), thermo-regulated wide angle X-ray analysis (WAXS), Nuclear Magnetic Resonance (NRM), and finally mechanical tests on PHBV films. The combination of these experiments revealed how inappropriate processing temperatures can result in irreversible changes in PHBVs’ macromolecular and crystalline structures, thermal behavior and mechanical performances. When increasing the HV content of the copolymer, adjusting the processing conditions according to these results revealed to be critical to match the functional properties targeted for a specific use.