Yaowen Liu

Composite poly(lactic acid)/chitosan nanofibrous scaffolds for cardiac tissue engineering

Fibrous scaffolds with different ratios of poly (lactic acid) (PLA) and chitosan were fabricated by conventional electrospinning. After crosslinking by the glutaraldehyde vapor, the structure, mechanical properties, hydrophilicity, and in-fiber chemical interactions of the scaffolds were investigated. We found that the fiber diameter decreased with the concentration of chitosan, while mechanical properties and hydrophilicity improved. In addition, we found that scaffolds with aligned fibers have higher mechanical strength and biocompatibility than scaffolds with randomly oriented fibers. In particular, scaffolds with aligned fibers with PLA:chitosan ratios of 7:1 was found to support cardiomyocyte viability, elicit cell elongation, and enhance production of sarcomeric α-actinin and troponin I. Collectively, the data indicate that composite scaffolds consisting of PLA/chitosan fibers have great potential for engineering cardiac tissue, and for accelerating the regeneration of myocardia.

Fabrication of Electrospun Polylactic Acid/Cinnamaldehyde/β-Cyclodextrin Fibers as an Antimicrobial Wound Dressing

Cinnamaldehyde (CA) was successfully encapsulated in β-cyclodextrin (β-CD), and polylactic acid (PLA)-based composite fibers were prepared by incorporating CA/β-CD via electrospinning. Morphological, structural, spectral, and antibacterial properties of different weight ratios of PLA:β-CD/CA (88:12, 94:6, 97:3, and 98.5:1.5) and PLA/CA/β-CD fibers were investigated. PLA and CA/β-CD were incorporated by mixing of CA/β-CD inclusions to enhance the viscosity of the mixed solution. The mechanical properties and hydrophilicity of nanofibers were improved following the addition of CA/β-CD. Moreover, CA/β-CD improved the antibacterial activities of the mixture against Escherichia coli and Staphylococcus aureus. PLA/CA/β-CD-3 exhibited excellent antibacterial effects and low cytotoxicity. Thus, our study showed that PLA/CA/β-CD fibers may have applications as wound dressing materials and for use in other biomedical applications.

Fabrication of antibacterial chitosan-PVA blended film using electrospray technique for food packaging applications

In this study, blended films from poly(vinyl alcohol) (PVA) containing chitosan (CS) were prepared via a simple solution casting and electrospraying method. The structures of the PVA-CS films were characterized by Fourier-transform infrared spectroscopy. The morphologies of the films were observed by scanning electron microscopy. The thermal properties of the PVA-CS films were examined by thermogravimetry. The effects of CS contents on the mechanical properties, oxygen permeability values, water vapor permeation levels, and antibacterial behaviors against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) strains were investigated. Compared to the pure PVA film, the PVA-CS films showed greater elongation at break, lower oxygen permeability, higher water barrier properties, and greater antibacterial activity, especially for the PVA:CS weight ratio of 75:25. The obtained results indicate the PVA-CS film may be a promising material for food packaging applications.

Development of Poly(lactic acid)/Chitosan Fibers Loaded with Essential Oil for Antimicrobial Applications

Cinnamon essential oil (CEO) was successfully encapsulated into chitosan (CS) nanoparticles at different loading amounts (1%, 1.5%, 2%, and 2.5% v/v) using oil-in-water (o/w) emulsion and ionic-gelation methods. In order to form active packaging, poly(lactic acid) (PLA) was used to fabricate PLA/CS-CEO composite fibers using a simple electrospinning method. The shape, size, zeta potential, and encapsulation efficacy of the CS-CEO nanoparticles were investigated. The composition, morphology, and release behavior of the composite fibers were investigated. PLA/CS-CEO-1.5 showed good stability and favorable sustained release of CEO, resulting in improved antimicrobial activity compared to the other blends. The PLA/CS-CEO fibers showed high long-term inactivation rates against Escherichia coli and Staphylococcus aureus due to the sustained release of CEO, indicating that the developed PLA/CS-CEO fibers have great potential for active food packaging applications.

Patterned Fibers Embedded Microfluidic Chips Based on PLA and PDMS for Ag Nanoparticle Safety Testing

A new method to integrate poly-dl-lactide (PLA) patterned electrospun fibers with a polydimethylsiloxane (PDMS) microfluidic chip was successfully developed via lithography. Hepatocyte behavior under static and dynamic conditions was investigated. Immunohistochemical analyses indicated good hepatocyte survival under the dynamic culture system with effective hepatocyte spheroid formation in the patterned microfluidic chip vs. static culture conditions and tissue culture plate (TCP). In particular, hepatocytes seeded in this microfluidic chip under a flow rate of 10 μL/min could re-establish hepatocyte polarity to support biliary excretion and were able to maintain high levels of albumin and urea secretion over 15 days. Furthermore, the optimized system could produce sensitive and consistent responses to nano-Ag-induced hepatotoxicity during culture. Thus, this microfluidic chip device provides a new means of fabricating complex liver tissue-engineered scaffolds, and may be of considerable utility in the toxicity screening of nanoparticles.

A comparative study of the properties and self-aggregation behavior of collagens from the scales and skin of grass carp (Ctenopharyngodon idella)

Collagens were extracted from the scales and skin of Ctenopharyngodon idella (C. idella) as raw materials using an acid-enzyme hybrid method. The structural properties of the extracted collagens were compared using ultraviolet-visible spectrophotometry, Fourier transform infrared spectroscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and differential scanning calorimetry. Additionally, the in vitro self-aggregation behaviors of the two types of collagens (fish skin- and scale-derived collagens) were compared using turbidimetric assays, aggregation assays, and scanning electron microscopy (SEM). The results showed that both types of extracted collagen were typical type I collagen with two α chains and intact triple-helical structures. The denaturation temperatures of the collagens from fish scales and skin were 34.99°C and 39.75°C, respectively. Both types of collagens were capable of self-aggregation in neutral salt solution at 30°C, with aggregation degrees of 28% and 27.33% for the scale and skin collagens, respectively. SEM analysis revealed that both types of collagens could self-aggregate into interwoven fibers, and the fish scale-derived collagen had a more pronounced reticular fiber structure with a striped periodic D-band pattern of collagen fibrils, whereas the collagen fibers from the self-aggregation of fish skin-derived collagen had a certain degree of disruption without any D-band pattern.

Electrospun Antimicrobial Polylactic Acid/Tea Polyphenol Nanofibers for Food-Packaging Applications

The development of new bioactive food-packaging materials that extend the shelf life of food is an important objective. Herein, we report the fabrication of four polylactic acid/tea polyphenol (PLA/TP) composite nanofibers, with PLA/TP ratios of 5:1, 4:1, 3:1, and 2:1, by electrospinning. The morphological quality of each sample was examined by scanning electron microscopy (SEM), and samples with higher TP content were found to be deeper in color. The samples were then examined by Fourier transform infrared (FTIR) spectroscopy to confirm the presence of TP. Examination of the mechanical properties of these fibers revealed that the presence of TP decreased both tensile strength and elongation at break; however, this decrease was only slight for the PLA/TP-3:1 composite fiber. The addition of TP influenced the hydrophilic–hydrophobic property and release behavior of the composite fibers, which significantly improved the antioxidant behavior of these samples, with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacities of up to 95.07% ± 10.55% observed. Finally, antimicrobial activities against Escherichia coli and Staphylococcus aureus of up to 92.26% ± 5.93% and 94.58% ± 6.53%, respectively, were observed for the PLA/TP-3:1 composite fiber. The present study demonstrated that PLA/TP composite nanofibers can potentially be used for food-packaging applications that extend food shelf life.

Physical and Antibacterial Properties of Sodium Alginate—Sodium Carboxymethylcellulose Films Containing Lactococcus lactis

Edible films have gradually become a research focus for food packaging materials due to a variety of benefits, including environmental friendliness, good barrier properties, and good carrying capacity. In this experimental study, we used sodium alginate as a film-forming substrate, sodium carboxymethylcellulose as a modifier, and glycerol as a plasticizer, then Lactococcus lactis was added to film solutions to form bacteriostatic films via the tape casting method. With the addition of Lactococcus lactis, the films did not significantly change thickness, while the transparency decreased and a significant increase in red and yellow hues was observed. Meanwhile, the dispersion of bacterial cells in film solutions destroyed intermolecular interactions in the solutions during film formation and increased the volume of voids in the Lactococcus lactis-containing films, thereby slightly decreasing the tensile strength of the films, but significantly increasing water vapor permeability. Moreover, the films with added Lactococcus lactis showed significant bacteriostatic activity against Staphylococcus aureus at 4 °C. In a seven-day bacteriostatic test, the films with Lactococcus lactis added at a level of 1.5 g/100 g resulted in a decrease in the viable cell count of Staphylococcus aureus by at least four logarithmic units. This study of Lactococcus lactis-containing films has provided a new method and strategy for antibacterial preservation of foods.

Preparation and properties of polylactic acid-tea polyphenol-chitosan composite membranes

To study the properties of composite membranes consisting of polylactic acid (PLA), tea polyphenol (TP), and chitosan (CS), the stretch film method was employed to make PLA-TP- CS composite membranes of different concentrations. By testing the density, mechanical properties, heat-sealing performance, water vapor permeability, and solubility of the pure PLA membrane and the composite membranes, the comprehensive performance of the composite membranes were analyzed with regard to the actual use value. The results show that, compared with the pure PLA membrane, adding TP and CS significantly increases the heat-sealing strength, water vapor permeability, and solubility of the composite membrane. When the composite membrane is used for the preservation of cherries, it is found that the composite membrane with the mass ratio of TP to CS of 3:7 can decrease the rotting rate and mass loss rate significantly, postpone the consumption of soluble solids and vitamin C, maintain the quality of the cherries, and extend the shelf life, thus proving its potential for application in food packaging.

Fabrication of polylactic acid/carbon nanotubes/chitosan composite fibers by electrospinning for strawberry preservation

In this study, we employed electrospinning to fabricate polylactic acid (PLA)/carbon nanotubes (CNTs)/chitosan (CS) composite fibers containing different CS contents and examined the ability of these fibers for strawberry preservation for the first time. The experimental results showed that as CS content increased, the mechanical properties, solubility, and swelling ratio of the fiber films first improved and then degraded, with peak values being achieved at a CS content of 7u202fwt%. The antimicrobial activity test results showed that as CS content increased, the antimicrobial activity of the composite fiber films against four microorganisms increased and the activity was the best when the CS content was 7u202fwt%. In addition, the composite fibers exhibited better antimicrobial activity against Gram-negative and -positive bacteria than against molds. Moreover, the fibers exhibited better antimicrobial activity against Staphylococcus aureus than against Escherichia coli. The preservation experiments showed that the nanocomposite fibers containing different CS contents exhibited good preservation effects for strawberries, with the fiber containing 7u202fwt% CS showing the best results. Thus, these fibers can delay the physiological changes in strawberries and extend their shelf life and therefore have important potential applications for fruit and vegetable preservation in the future.