Designing active mats based on cellulose acetate/polycaprolactone core/shell structures with different release kinetics

Characterization of sodium alginate film containing zein-Arabic gum nanoparticles encapsulated with oregano essential oil for chilled pork packaging

Chilled pork retains most of its nutrients but is prone to deterioration during the production-to-consumption process. To address this issue this study aimed to develop zein-Arabic gum composite nanoparticles loaded with oregano essential oil (ZAG-OEO) and incorporate them into sodium alginate films to enhance the freshness and shelf life of chilled pork. Sodium alginate, known for its excellent film-forming properties, was selected as the matrix to prepare ZAG-OEO-containing sodium alginate films (SA-ZAG-OEO). The results revealed that the tensile strength and elongation at break of the prepared films were 47.73 ± 2.15 MPa and 6.27 ± 0.21 %, respectively, at a 2.5 % nanoparticle concentration. The water contact angle of the films incorporating nanoparticles reached 81.5 ± 1.95°. The incorporation of nanoparticles enhanced the thermal stability and antibacterial activity of the films. The prepared films were utilized for the storage of chilled pork, and the quality changes were analyzed. The results demonstrate that SA-ZAG-OEO films inhibit microbial growth and lipid oxidation, thereby delaying pork spoilage. This study offers new insights into extending the shelf life of chilled pork and developing advanced meat preservation methods for the future development of the meat industry.

Novel Electrospun Gelatin Nanofibers Loaded with Purple Potato Anthocyanin and Syringic Acid for Multifunctional Food Packaging

In this study, a series of novel nanofibers based on gelatin (GA) loading with purple potato anthocyanin (PPA) and syringic acid (SA) were obtained by electrospinning technology. The effects of SA on mechanical properties, thermal stability, antioxidant capacity, and antimicrobial activity of the GA/PPA nanofibers were systematically characterized. The scanning electron microscopy observation results revealed a smooth surface on the nanofibers. The incorporation of SA enhanced the viscosity of the electrospun solutions, and it increased the average diameter of nanofibers from 0.17 μm to 0.28 μm. The tensile strength and thermal stability of the obtained nanofibers were enhanced with the addition of a suitable level of SA (1.5%, w/v), which strengthened the intermolecular interaction. The GA/PPA/SA nanofibers presented over 80% antioxidant capacity and strong antibacterial activity against E. coli and S. aureus. Meanwhile, the sensitivity responses of nanofibers to NH3 revealed that GA/PPA/SA II nanofibers (1.5% w/v SA) presented good sensitivity of colorimetric behavior to ammonia. A pork spoilage test was performed to evaluate practical application of the nanofibers, and an obvious color change (dark purple to green) was observed. These results indicated GA/PPA/SA II nanofibers can be utilized as an active and intelligent multipurpose packaging material to preserve and track the freshness of pork.

Core-Shell Gel Nanofiber Scaffolds Constructed by Microfluidic Spinning toward Wound Repair and Tissue Regeneration

Growing demand for wound care resulting from the increasing chronic diseases and trauma brings intense pressure to global medical health service system. Artificial skin provides mechanical and microenvironmental support for wound, which is crucial in wound healing and tissue regeneration. However, challenges still remain in the clinical application of artificial skin since the lack of the synergy effect of necessary performance. In this study, a multi-functional artificial skin is fabricated through microfluidic spinning technology by using core-shell gel nanofiber scaffolds (NFSs). This strategy can precisely manipulate the microstructure of artificial skin under microscale. The as-prepared artificial skin demonstrates superior characteristics including surface wettability, breathability, high mechanical strength, strain sensitivity, biocompatibility and biodegradability. Notably, this artificial skin has the capability to deliver medications in a controlled and sustained manner, thereby accelerating the wound healing process. This innovative approach paves the way for the development of a new generation of artificial skin and introduces a novel concept for the structural design of the unique core-shell gel NFSs.

Preparation and characterization of zein-tannic acid nanoparticles/chitosan composite films and application in the preservation of sugar oranges

Chitosan-based food packaging film was prepared by incorporating zein-tannic acid nanoparticles (ZTNPs) into chitosan and was evaluated in terms of structure, physical, mechanical and functional properties. Results showed that there were hydrogen bonding interactions between ZTNPs and chitosan matrix, which is conductive to mechanical enhancements of chitosan films. Compared with the pure chitosan film, the composite films with 10% ZTNPs at pH 4 showed the increased tensile strength by 196.58%, increased elongation at break by 161.37%, decreased water vapor permeability by 70.76% and decreased oxygen permeability by 40.68%. The highest inhibition rates of this composite film-forming fluid against Escherichia coli and Staphylococcus aureus reached 83.32% and 72.35%, respectively. The composite film forming solution formed by adding 10% ZTNPs was used for sugar orange preservation. The weight loss rate of oranges was reduced and the nutrient retention rate was improved. This study expanded the application of chitosan-based packaging materials in fruit preservation.

Thymol incorporation within chitosan/polyethylene oxide nanofibers by concurrent coaxial electrospinning and in-situ crosslinking from core-out for active antibacterial packaging

Active packaging systems that are sustainable and capable of delivering antimicrobial agents are in demand in food industry. In this work, Thymol (Thy) was encapsulated into Polyethylene oxide (PEO)/Chitosan (CS) to form core-shell nanofibers via coaxial electrospinning. Various dose of the crosslinker-genipin (GP) were encapsulated into the core layer to achieve in-situ etching crosslink with the CS of shell layer during the electrospinning process. The core-shell structure of the nanofiber was confirmed by transmission electron microscopy. The microstructures, mechanical properties, water vapor permeability, swelling ratios, wettability, thermal stability, biocompatibility and antibacterial properties of the crosslinked films were characterized. The results showed that the crosslinked films had compact structures, strong water resistance, better mechanical property and thermal stability, the sustained release profiles and antioxidant activity were also improved. More importantly, the antibacterial assays indicated that the Thy loaded nanofiber films could effectively inhibit the growth of two common food spoilage bacteria-E. coli and S. aureus.

Encapsulation of quercetin into zein-ethyl cellulose coaxial nanofibers: Preparation, characterization and its anticancer activity

In order to efficiently improve the colon-targeted delivery of quercetin, the hydrophobic core-shell nanofibers were fabricated to encapsulate quercetin using ethyl cellulose as the shell and zein as the core by coaxial electrospinning. The encapsulation efficiency of coaxial nanofibers reached >97 %. FTIR and XRD results revealed the interactions between quercetin and wall materials and quercetin was encapsulated in an amorphous state. The thermal stability and surface hydrophobicity of coaxial nanofibers were improved compared to the uniaxial zein fibers. After in vitro gastrointestinal digestion, the quercetin release from core-shell nanofibers was <12.38 %, while the corresponding value for zein fibers was 36.24 %. DPPH and FRAP assays showed that there was no significant difference in the antioxidant activity of quercetin before and after encapsulation. Furthermore, the encapsulated quercetin exhibited similar anti-proliferative activity against HCT-116 cells compared to the free form. The results suggest these coaxial nanofibers have potential applications in functional foods.

Mimicking natural electrical environment with cellulose acetate scaffolds enhances collagen formation of osteoblasts

The medical field is continuously seeking new solutions and materials, where cellulose materials due to their high biocompatibility have great potential. Here we investigate the applicability of cellulose acetate (CA) electrospun fibers for bone tissue regeneration. For the first time we show the piezoelectric properties of electrospun CA fibers via high voltage switching spectroscopy piezoresponse force microscopy (HVSS-PFM) tests, which are followed by surface potential studies using Kelvin probe force microscopy (KPFM) and zeta potential measurements. Piezoelectric coefficient for CA fibers of 6.68 ± 1.70 pmV^-1 along with high surface (718 mV) and zeta (-12.2 mV) potentials allowed us to mimic natural electrical environment favoring bone cell attachment and growth. Importantly, the synergy between increased surface potential and highly developed structure of the fibrous scaffold led to the formation of a vast 3D network of collagen produced by osteoblasts only after 7 days of in vitro culture. We clearly show the advantages of CA scaffolds as a bone replacement material, when long-lasting structural support is needed.

Developing Core/Shell Capsules Based on Hydroxypropyl Methylcellulose and Gelatin through Electrodynamic Atomization for Betalain Encapsulation

Betalains are bioactive compounds with remarkable functional and nutritional activities for health and food preservation and attractiveness. Nevertheless, they are highly sensitive to external factors, such as oxygen presence, light, and high temperatures. Therefore, the search for new structures, polymeric matrices, and efficient methods of encapsulation of these compounds is of great interest to increase their addition to food products. In this work, betalains were extracted from red beetroot. Betacyanin and betaxanthin contents were quantified. Subsequently, these compounds were successfully encapsulated into the core of coaxial electrosprayed capsules composed of hydroxypropyl methylcellulose (HPMC) and gelatin (G). The effect of incorporating the carbohydrate and the protein both in the core or shell structures was studied to elucidate the best composition for betalain protection. Morphological, optical, and structural properties were analyzed to understand the effect of the incorporation of the bioactive compounds in the morphology, color, and chemical interactions between components of resulting electrosprayed capsules. The results of the thermogravimetric and encapsulation efficiency analysis coincided that the incorporation of beetroot extract in G in the core and HPMC in the shell resulted in the structure with greater betalain protection. The effectiveness of the core/shell structure was confirmed for future food applications.

Tuning the Drug Release from Antibacterial Polycaprolactone/Rifampicin-Based Core-Shell Electrospun Membranes: A Proof of Concept

The employment of coaxial fibers for guided tissue regeneration can be extremely advantageous since they allow the functionalization with bioactive compounds to be preserved and released with a long-term efficacy. Antibacterial coaxial membranes based on poly-ε-caprolactone (PCL) and rifampicin (Rif) were synthesized here, by analyzing the effects of loading the drug within the core or on the shell layer with respect to non-coaxial matrices. The membranes were, therefore, characterized for their surface properties in addition to analyzing drug release, antibacterial efficacy, and biocompatibility. The results showed that the lower drug surface density in coaxial fibers hinders the interaction with serum proteins, resulting in a hydrophobic behavior compared to non-coaxial mats. The air-plasma treatment increased their hydrophilicity, although it induced rifampicin degradation. Moreover, the substantially lower release of coaxial fibers influenced the antibacterial efficacy, tested against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Indeed, the coaxial matrices were inhibitory and bactericidal only against S. aureus, while the higher release from non-coaxial mats rendered them active even against E. coli. The biocompatibility of the released rifampicin was assessed too on murine fibroblasts, revealing no cytotoxic effects. Hence, the presented coaxial system should be further optimized to tune the drug release according to the antibacterial effectiveness.

Bioactive Electrospun Fibers of Poly(ε-Caprolactone) Incorporating α-Tocopherol for Food Packaging Applications

Antioxidant activity is an important feature for food contact materials such as packaging, aiming to preserve freshness and retard food spoilage. Common bioactive agents are highly susceptible to various forms of degradation; therefore, protection is required to maintain functionality and bioavailability. Poly(ε-caprolactone) (PCL), a biodegradable GRAS labeled polymer, was used in this study for encapsulation of α-tocopherol antioxidant, a major component of vitamin E, in the form of electrospun fibers. Rheological properties of the fiber forming solutions, which determine the electrospinning behavior, were correlated with the properties of electrospun fibers, e.g., morphology and surface properties. Interactions through hydrogen bonds were evidenced between the two components. These have strong effect on structuration of macromolecular chains, especially at low α-tocopherol amounts, decreasing viscosity and elastic modulus. Intra-molecular interactions in PCL strengthen at high α-tocopherol amounts due to decreased solvation, allowing good structural recovery after cease of mechanical stress. Morphologically homogeneous electrospun fibers were obtained, with ~6 μm average diameter. The obtained fibers were highly hydrophobic, with fast release in 95% ethanol as alternative simulant for fatty foods. This induced good in vitro antioxidant activity and significant in vivo reduction of microbial growth on cheese, as determined by respirometry. Therefore, the electrospun fibers from PCL entrapping α-tocopherol as bioactive agent showed potential use in food packaging materials.

Development of Active Packaging to Extend the Shelf Life of Agaricus bisporus by Using Plasma Technology

In this study, a preservation package that can extend the shelf life of Agaricus bisporus was developed using plasma modification combined with low-density polyethylene (LDPE), collagen (COL), and carboxymethyl cellulose (CMC). Out results showed that the selectivity of LDPE to gas can be controlled by plasma modification combined with coating of different concentrations of CMC and COL. Packaging test results applied to A. bisporus showed that 3% and 5% of CMC and COL did not significantly inhibit polyphenol oxidase and β-1,3-glucanase, indicating no significant effect on structural integrity and oxidative browning. The use of 0.5% and 1.0% CMC and COL can effectively inhibit the polyphenol oxidase and β-1,3-glucanase activity of A. bisporus, leading to improved effects in browning inhibition and structural integrity maintenance. P-1.0COL can effectively maintain gas composition in the package (carbon dioxide: 10–15% and oxygen: 8–15%) and catalase activity during storage, thereby reducing the oxidative damage caused by respiration of A. bisporus. The current study confirmed that the use of plasma modification technology combined with 1.0% COL can be used in preservation packaging by regulating the respiration of A. bisporus, thus extending its shelf life from 7 to 21 days.

Designing Biodegradable and Active Multilayer System by Assembling an Electrospun Polycaprolactone Mat Containing Quercetin and Nanocellulose between Polylactic Acid Films

The design of multilayer systems is an innovative strategy to improve physical properties of biodegradable polymers and introduce functionality to the materials through the incorporation of an active compound into some of these layers. In this work, a trilayer film based on a sandwich of electrospun polycaprolactone (PCL) fibers (PCLé) containing quercetin (Q) and cellulose nanocrystals (CNC) between extruded polylactic acid (PLA) films was designed with the purpose of improving thermal and barrier properties and affording antioxidant activity to packaged foods. PCLé was successfully electrospun onto 70 µm-thick extruded PLA film followed by the assembling of a third 25 µm-thick commercial PLA film through hot pressing. Optical, morphological, thermal, and barrier properties were evaluated in order to study the effect of PCL layer and the addition of Q and CNC. Bilayer systems obtained after the electrospinning process of PCL onto PLA film were also evaluated. The release of quercetin from bi- and trilayer films to food simulants was also analyzed. Results evidenced that thermal treatment during thermo-compression melted PCL polymer and resulted in trilayer systems with barrier properties similar to single PLA film. Quercetin release from bi- and trilayer films followed a similar profile, but achieved highest value through the addition of CNC.