Zein Fibers Research Articles

Oxidative stability of encapsulated fish oil in electrospun zein fibres

Zein fibres loaded with fish oil were generated by electrospinning of zein polymer solutions (20% w/w) prepared in 70% (w/w) aqueous ethanol and isopropanol solvents. Zein fibres with a diameter of about 300nm with smooth surface morphology were produced from ethanol-based solutions. The fibre diameter increased to about 500nm as a result of the addition of 30% (w/w) fish oil. Thinner fibres (190±62nm) with beads averaging up to 1μm in size were produced from isopropanol zein solutions with decreasing bead formation due to the addition of fish oil by 30% (w/w). Transmission electron microscopy and florescence microscopy were utilized to examine the distribution of fish oil in the electrospun materials, revealing that the lipid phase tended to concentrate at the core of the fibres and beads, as a result of phase separation during the electrospinning process. This behaviour positively impacted the encapsulation efficiency, loading capacity, as well as the stability of the fish oil tested at 4, 25 and 60°C. The encapsulation efficiency of the electrospun zein fibres reached as high as 91% for ethanol-based and 96% for isopropanol-based fibres, at 30% (w/w) loading level. The oxidative stability of the encapsulated and non-encapsulated fish oil was monitored over a period of 14days by determining the formation of lipid peroxide using a modified ferrous oxidation–xylenol orange method. The secondary oxidative by-products were evaluated by p-anisidine value. The oxidative stability was further monitored via Fourier transform infrared spectroscopy. The results indicated that electrospun zein fibres provide a greater oxidative stability in comparison to non-encapsulated fish oil.

On the use of different hydrocolloids as electrospun adhesive interlayers to enhance the barrier properties of polyhydroxyalkanoates of interest in fully renewable food packaging concepts

This paper compares the effect of adding different high barrier nanostructured interlayers with adhesive properties, made of electrospun whey protein isolate (WPI), pullulan, zein and zein blends with WPI and pullulan, to a polyhydroxyalkanoates material, specifically, polyhydroxybutyrate-co-valerate with a valerate content of 3% (PHBV3) in a multilayer form. The attained morphology, thickness and inherent permeability of the electrospun nanostructures played an important role on oxygen and water barrier properties of these multilayer systems, since both permeability values were only improved when fibrillar morphologies (pullulan and/or zein fibres) were obtained. More specifically, oxygen and water vapour permeability values were improved between 38–48% and 28–35%, respectively, in multilayer systems prepared by the addition of electrospun zein and/or pullulan nanofibres. However, the electrospun WPI nanostructures, exhibiting a beaded morphology, did not significantly decrease the water vapour and oxygen permeability values of the PHBV3-multilayer systems as did zein and pullulan (fibres). These results add new insight, to other previous studies, into the potential of this processing method for the development of biodegradable PHBV multilayer systems of significant interest in food packaging applications.

Zein/polycaprolactone electrospun matrices for localised controlled delivery of tetracycline.

We report the controlled release of the antibiotic tetracycline (Tet) from triple-layered (3L) electrospun matrices consisting of zein or a zein/PCL blend, where the drug was loaded into the central layer with the two outer layers acting as diffusion barriers. These fibrous matrices successfully encapsulated Tet and efficiently inhibited the growth of a clinical isolate, the methicillin-resistant Staphylococcus aureus strain MRSA252, as demonstrated in a modified Kirby-Bauer disc assay over 5days. Whilst untreated zein fibres are unstable in an aqueous environment, rapidly shrinking due to plasticisation and film formation, blending zein with PCL stabilised the electrospun matrices and prevented them from shrinking. These 3L formulations display sustained antibiotic release and provide a proof of concept for zein-based polymeric matrices as wound dressings to treat or prevent bacterial infection. This is the first demonstration of the controlled release of a clinically used antibiotic from electrospun zein-based matrices.

Drug-Loaded Zein Nanofibers Prepared Using a Modified Coaxial Electrospinning Process

This study investigated the preparation of drug-loaded fibers using a modified coaxial electrospinning process, in which only unspinnable solvent was used as sheath fluid. With zein/ibuprofen (IBU) co-dissolving solution and N, N-dimethylformamide as core and sheath fluids, respectively, the drug-loaded zein fibers could be generated continuously and smoothly without any clogging of the spinneret. Field emission scanning electron microscopy and transmission electron microscopy observations demonstrated that the fibers had ribbon morphology with a smooth surface. Their average diameters were 0.94±0.34 and 0.67±0.21 μm when the sheath-to-core flow rate ratios were taken as 0.11 and 0.25, respectively. X-ray diffraction and differential scanning calorimetry verified that IBU was in an amorphous state in all fiber composites. Fourier transform infrared spectra showed that zein had good compatibility with IBU owing to hydrogen bonding. In vitro dissolution tests showed that all the fibers could provide sustained drug release files via a typical Fickian diffusion mechanism. The modified coaxial electrospinning process reported here can expand the capability of electrospinning in generating fibers and provides a new manner for developing novel drug delivery systems.

Coaxial electrospinning with acetic acid for preparing ferulic acid/zein composite fibers with improved drug release profiles

This study investigated drug/zein composite fibers prepared using a modified coaxial electrospinning process. With unspinnable acetic acid as sheath liquid and an electrospinnable co-dissolving solution of zein and ferulic acid (FA) as core fluid, the modified coaxial process could run smoothly and continuously without any clogging. Compared with those from the single-fluid electrospinning process, the FA-loaded zein fibers from the modified process were rounder and possessed higher quality in terms of diameter and distribution, as verified by scanning electron microscopic observations of their surface and cross-section. Differential scanning calorimetry and X-ray diffraction showed that fibers from both processes similarly formed a composite with the FA present in the zein matrix in an amorphous state. The driving force of encapsulation of FA into zein fibers was hydrogen bonding, as evidenced by the attenuated total reflectance Fourier transform infrared spectra. However, in vitro dissolution tests demonstrated that the fibers from the coaxial process exhibited better sustained-release profiles with a smaller initial burst effect and less tailing-off release compared with those from the single process. The modified coaxial electrospinning process is a useful tool for generating nanofibers with higher quality and improved functional performance.

Electrospinning of Prolamin Proteins in Acetic Acid: The Effects of Protein Conformation and Aggregation in Solution

AbstractThe electrospinnability of hordein and gliadin from acetic acid solutions is demonstrated and compared to that of zein. The relation between protein conformations in solution and the properties of post‐spun fibers are studied by means of CD, FTIR, TEM, DLS, viscosity measurements, SEM, and mechanical testing. The results show that both electrospinnability of the proteins and mechanical properties of post‐spun fibers are significantly influenced by solution protein conformations. Ultrafine fibers are fabricated at optimized concentrations, while large compact aggregates caused by hydrophobic interactions have a negative effect on the formation of continuous protein fibers. Moreover, hordein fibers show a lower cytotoxicity than gliadin and zein fibers. magnified image

Advanced Surface Modifications for Blood-Contacting Surfaces of Medical Devices

Surface modification of biomaterial interfaces remains an active field of research with a clear aim to enhance and retain blood compatibility of blood-contacting medical devices. Issues such as activation of coagulation pathways, altered hemostasis, inflammatory responses, and thrombosis are potential clinical complications during blood interaction with artificial surfaces that needs to be addressed when a new device is developed or there is a modification of a device or implant in the form of material, surface characteristics, shape, or function. Large surface areas in certain devices, such as blood oxygenator membranes, hemodialysis membranes, or nanosized particles, present unique surface-related challenges. Minimizing pro-coagulant protein adsorption, platelet activation and deposition on the biomaterial interface are key factors that ultimately decide the performance and long-term reliability of a device. Among various types of biomedical devices, polymeric ones have a lion's share and accordingly substantial attention is being paid to surface-modification of polymeric surfaces. Several challenges in attaining modification of the surfaces include, but are not limited to, device specifics, application specifics and underlying thermodynamic and kinetic specific parameters. International Journal of Biomaterials has launched this special issue with emphasis on analyzing numerous strategies in light of the ongoing advancements in design and development of blood-contacting medical devices. Peer-reviewed, original research, and review papers in the area of blood-compatible surface advancements are included. The topics comprise new methods and combination of principles, novel evaluation techniques, and current and future directions. The papers in this issue address several aspects of blood-contacting surfaces including modulation of interfacial bioactivities, evaluation methods and improvements in surface modification techniques. Altogether, five research papers and one review paper of this special issue are concerned with materials, devices, parameters, and mechanisms in relation to blood compatibility. P. A. Patston et al. describe modulation of specific blood contact activation parameter (kallikrein) by C1-inhibitor in the presence of type IV collagen. They not only demonstrate the tight binding of C1-inhibitor with type IV collagen but also show collagen's influence in reducing the rate of inhibition. This paper provides an additional insight into collagen containing biomaterial surfaces. B. Dhandayuthapani and coworkers report on critical evaluation of nanocomposite scaffolds comprising single wall carbon nanotubes and Zein fibers. This paper covers structural, physicochemical, and hemocompatibility assessments that bring into focus the applicability of these unique composite scaffolds. M. Faria et al. contribute with another detailed evaluation in particular of surfaces composed of poly(ester urethane urea) oxygenation membranes. This paper incorporates cross-sectional studies of membranes and analyses to assess physicochemical and hemocompatibility features of their surfaces. Oligonucleotide and Parylene surface coating for a specific hemocompatible surface modification is described by M. Schleicher et al. in a separate paper. This is an interesting contribution in the direction of biofunctionalization of vascular implant surfaces. W. Van Oeveren and coworkers present a comparative study between different blood circulation models. They estimate functional as well as mechanical blood damage features under specific conditions. The review article of this special issue focuses on physicochemical and biological methods of surface modifications related to surfaces of cardiovascular implants. It is contributed by A. de Mel et al. The paper highlights the role of nanotechnology in connection with surface modification. We are confident that this special issue provides a comprehensive review as well as new insights related to surface modification and evaluation technologies for blood contacting applications. Zhongjun J. Wu Narayana Garimella Rolf Larsson Eduard Brynda

Effect of Ethanol/water Solvent Ratios on the Morphology of Zein Nanofiber Mats and their Wettability

Zein is a hydrophobic protein produced from maize and has great potential in a number of industrial applications, such as food, food coating and food packaging. To obtain suitable electrospinning conditions for thinner and uniform zein nanofiber mats, a series of experiments was conducted on various volume ratios (v/v) of ethanol/water solutions with different zein concentrations. The prepared zein nanofiber mats were characterized by field emission scanning electron microscopy and contact angle measurements. Uniform zein fibers with a average diameter in the nanometer scale (300~500 nm) could be prepared from 30 wt.% zein in 7/3 (v/v) ethanol/water solutions.

Influence of solution and processing parameters towards the fabrication of electrospun zein fibers with sub-micron diameter

Abstract The effects of processing and solution parameters on the morphology of food grade electrospun fibers were investigated. The relationship of entanglement concentration ( C e ) of zein solution and its electrospinnability was inspected to determine the correlation of fiber morphology with the rheology of solutions. Bead-free and uniform zein electrospun fibers were successfully constructed. Response surface methodology (RSM) was utilized to facilitate a more systematic understanding of the electrospinning parameters of zein solutions. The electrospinning parameters studied were concentration of zein solution, solution feed rate, applied voltage and distance between needle tip and collector. The individual and interaction effects between the parameters on average diameter of the electrospun fibers were determined using Box and Behnken factorial design. The interaction effect between feed rate and voltage, the quadratic coefficients of the applied voltage as well as linear coefficients of the solution concentration, voltage and feed rate were found statistically significant in the fabrication of sub-micron fibers. Hence, this work provides an overview on the impact of solution and processing parameters to the fabrication of zein electrospun fibers which may find uses as nanostructured materials in food industry.

Electrospun zein fibers using glyoxal as the crosslinking reagent

AbstractAfter reaction of zein with glyoxal the resulting electrospun fibers have improved resistance to known zein solvents. Durable fibers with diameters of 0.6 μm could be produced. The reaction between zein and glyoxal was carried out in acetic acid (AcOH) at temperatures between 25 and 60°C at various lengths of time. Gelation would occur after higher extents of reaction. During the course of reaction, solution viscosity increased which increased the diameter of the electrospun fibers produced from these solutions. Gel electrophoresis showed increased molecular weight as the reaction progressed. When 6% glyoxal was allowed to react with zein at 25°C for 6 h, the resulting fibers were durable to AcOH as spun. Other formulations required a second thermal treatment to provide solvent durable fabrics. Fibers displayed different secondary structure utilizing far‐UV circular dichroism spectroscopy. The infrared spectra displayed peaks in the CO region supporting the reaction of glyoxal with hydroxyl groups present on zein. Zein fabrics incorporating glyoxal had modestly improved tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electrospinning formaldehyde‐crosslinked zein solutions

AbstractIn order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as a crosslinking reagent before spinning. The crosslinking reaction was carried out in either acetic acid or ethanolic HCl where the amount of crosslinking reagent was between 1 and 6%. Reactions were carried out at various times and temperatures. When carried out in acetic acid, the maximum amount of formaldehyde that could be used was 1.5% as gelation occurred at higher levels. In ethanolic HCl, 6% formaldehyde could be incorporated into zein. All solutions were successfully electrospun, producing predominantly ribbon and round fibers; the morphology was strongly dependent on solvent and spinning solids. The formaldehyde‐crosslinked zein fabrics had double the tensile strength of control fabrics. SDS‐PAGE analysis clearly showed crosslinking had occurred. Electrospun fabrics from all formaldehyde‐treated zein solutions required an additional heating step in order to be resistant to dissolution in acetic acid, a known very good solvent for zein. Copyright © 2011 Society of Chemical Industry

Water-Stable Electrospun Zein Fibers for Potential Drug Delivery

This paper reports the development of electrospun zein fibers with improved water stability and tensile strength for potential drug delivery. The low morphological stability in aqueous environment and poor mechanical properties in dry and wet states have restricted the applications of electrospun protein materials, though these materials possess a unique structure, special adsorption properties, biocompatibility and biodegradability. In this study, the electrospun zein fibers were modified by non-toxic citric acid crosslinking catalyzed by NaOH. An up to 183% enhancement in dry tensile strength and an up to 448% improvement in wet tensile strength were generated. The cross-linked fibers were able to maintain their fibrous structure for 15 days in phosphate-buffered saline at 37°C. Moreover, those cross-linked electrospun zein fibers showed a potential in controlled drug delivery with a 58% drug-loading efficiency and a sustained profile drug release in artificial gastric juice.

Cytocompatible cross-linking of electrospun zein fibers for the development of water-stable tissue engineering scaffolds

This paper reports a new method of cross-linking electrospun zein fibers using citric acid as a non-toxic cross-linker to enhance the water stability and cytocompatibility of zein fibers for tissue engineering and other medical applications. The electrospun structure has many advantages over other types of structures and protein-based biomaterials possess unique properties preferred for tissue engineering and other medical applications. However, ultrafine fiber matrices developed from proteins have poor mechanical properties and morphological stability in the aqueous environments required for medical applications. Efforts have been made to improve the water stability of electrospun protein scaffolds using cross-linking and other approaches, but the current methods have major limitations, such as cytotoxicity and low efficiency. In this research electrospun zein fibers were cross-linked with citric acid without using any toxic catalysts. The stability of the cross-linked fibers in phosphate-buffered saline and their ability to support the attachment, spreading and proliferation of mouse fibroblast cells were studied. The cross-linked electrospun fibers retained their ultrafine fibrous structure even after immersion in PBS at 37 degrees C for up to 15 days. Citric acid cross-linked electrospun zein scaffolds showed better attachment, spreading and proliferation of fibroblast cells than uncross-linked electrospun zein fibers, cross-linked zein films and electrospun polylactide fibers.

Electrospun Zein Fibers as Carriers to Stabilize (−)‐Epigallocatechin Gallate

In this study, a method was developed for continuous electrospinning of ultrafine corn zein protein fibers with diameters ranging from 150 to 600 nm. Fiber-forming solutions with various zein concentrations (10% to 30%, w/w) and aqueous ethanol concentrations (60% to 90%, w/w) were electrospun at 15 and 20 kV. Scanning electron microscopy results showed that the morphology of zein fibers was affected by aqueous ethanol concentration, zein concentration, and the applied voltage. The optimal condition for forming bead-less fibers was found to be 20% protein, 70% alcohol, and 15 kV. The zein fibers resisted solubilization in water, although swelling and plasticization were apparent after the water treatment. The efficacy of zein fibers was tested for stabilization of a green tea polyphenol, (-)-epigallocatechin gallate (EGCG), by incorporating the EGCG in zein fiber-forming solutions. Freshly spun fibers were less effective at immobilizing the EGCG upon immersion in water (82% recovery) as compared to fibers that were aged at 0% relative humidity for at least 1 d (>98% recovery) before water immersion. Fourier transform infrared spectroscopy studies demonstrated that hydrogen bonding, hydrophobic interactions, and physical encapsulation are the major contributors to the stabilization of EGCG in zein fibers in water.

Alkali‐catalyzed low temperature wet crosslinking of plant proteins using carboxylic acids

We report the development of a new method of alkali-catalyzed low temperature wet crosslinking of plant proteins to improve their breaking tenacity without using high temperatures or phosphorus-containing catalysts used in conventional poly(carboxylic acid) crosslinking of cellulose and proteins. Carboxylic acids are preferred over aldehyde-containing crosslinkers for crosslinking proteins and cellulose because of their low toxicity and cost and ability to improve the desired properties of the materials. However, current knowledge in carboxylic acid crosslinking of proteins and cellulose requires the use of carboxylic acids with at least three carboxylic groups, toxic phosphorous-containing catalysts and curing at high temperatures (150-185 degrees C). The use of high temperatures and low pH in conventional carboxylic acid crosslinking has been reported to cause substantial strength loss and/or undesired changes in the properties of the crosslinked materials. In this research, gliadin, soy protein, and zein fibers have been crosslinked with malic acid, citric acid, and butanetetracarboxylic acid to improve the tenacity of the fibers without using high temperatures and phosphorus-containing catalysts. The new method of wet crosslinking using carboxylic acids containing two or more carboxylic groups will be useful to crosslink proteins for various industrial applications.

Novel route to stabilization of bioactive antioxidants by encapsulation in electrospun fibers of zein prolamine

The encapsulation of the light sensitive model β-carotene, a colorant and antioxidant molecule widely used in the food industry, has been successfully achieved in ultrafine fibers of zein prolamine, a sustainable agropolymer, by means of electrospinning. Fiber capsules were in the micro- and nanorange in the cross-section and the encapsulation preserved the fluorescence of the polyene molecules. Observations with confocal Raman imaging spectroscopy showed that the antioxidant was stable and widely dispersed inside the zein fibers but agglomerated in some areas. Nevertheless, a significant increase in the light stability of the β-carotene when exposed to UV–vis irradiation was determined for the encapsulated compound. As a result, electrospinning of zein prolamine shows an excellent outlook for its application in the stabilization of light sensitive added-value food components.

Novel zein‐based electrospun fibers with the water stability and strength necessary for various applications

AbstractBACKGROUND: Some of the problems with electrospun zein fiber are that it has very low tenacities in the dry and wet states and that mats of the fiber become films when immersed in water. The fibers are therefore unusable for various applications despite their good biocompatibility and biodegradability. This research was conducted to overcome these problems by electrospinning novel fibers containing various concentrations of zein, citric acid (CA) and sodium hypophosphite monohydrate (SHP) and by crosslinking the zein with CA and with SHP serving as a catalyst.RESULTS: The CA‐crosslinked electrospun zein fiber has as much as 10‐fold greater wet tenacity and 15‐fold greater dry tenacity than regular electrospun zein fiber. The average diameter of these fibers is 451 nm, which is the smallest diameter ever reported for zein‐based electrospun fiber. A mat of this fiber retains its fibrous structure when immersed in water, and the fiber retains about 70% of its tenacity after 16 days at 50 °C and 90% relative humidity.CONCLUSION: The high dry and wet tenacities, good water stability and small diameter of the novel CA‐crosslinked electrospun zein fiber make it attractive for biomedical and other applications that expose zein to water or that require high surface area. Copyright © 2008 Society of Chemical Industry

Electrospun Zein Fibers Using Glutaraldehyde as the Crosslinking Reagent: Effect of Time and Temperature

AbstractGlutaraldehyde was used as a crosslinking reagent to produce electrospun zein fibers with improved physical properties and solvent resistance. Using 8% glutaraldehyde, round and ribbon fibers were produced with diameters between 1 and 70 µm. All fibers readily dissolved in acetic acid. Heating the zein/glutaraldehyde fibers at temperatures from 80 to 180 °C for different times provided various degrees of insolubility to the fibers. A model was developed relating the extent of dissolution with the amount of glutaraldehyde used and the temperature/time at which the fiber was exposed. The fibers were found to be birefringent; upon heating, the amount of α‐helix in the fiber was reduced.magnified image

Characterization of the morphology and thermal properties of Zein Prolamine nanostructures obtained by electrospinning

Zein is a “yellowish” colored maize storage prolamine that shows great interest in a number of industrial applications such as food, food coating and food packaging. Nanofibers generated by electrospinning from solution exhibit an array of unique features and properties that distinguish them from other 1-D nanostructures fabricated using other nanotechnology techniques. This paper presents a complete study reporting on the effect of changing a number of unprecedented process parameters such as polymer concentration, solvent content, flow-rate, applied voltage, needle tip-to-collector distance and pH in order to control fiber size and end morphology. The results indicated that modifying the process parameters led to “white” colored zein fiber networks with fiber diameters ranging from less than a 100 nm (smaller nanometric morphologies ever reported for zein) to above 1 μm. Sample morphologies as determined by SEM and AFM tended to exhibit tubular-like shapes but more complex fiber morphologies such as nanobeads were also observed. Acidifying the alcohol zein solution yielded ribbon like morphologies which exhibited higher glass transition temperature than zein fibers obtained from pure alcohol solutions. On the contrary, alkaline solutions of zein yielded low solution viscosity and hence a faulty electrospinning experience. Fiber networks were seen to have increased thermal properties compared to solvent cast films due to probably their particular molecular structure and a high solvent removing efficiency. Finally, ATR-FTIR spectroscopy nicely showed that the zein secondary structure, particularly the α-helix length, is different depending on the electrospinning conditions applied and that this must influence the observed end properties of the protein fiber networks.

Novel Protein Fibers from Wheat Gluten

Protein fibers with mechanical properties similar to those of wool and better than those of soyprotein and zein fibers have been produced from 100% wheat gluten. Wheat gluten is a low cost, abundantly available, and renewable resource suitable for fiber production. A simple production method has been developed to obtain high-quality wheat gluten fibers, and the structure and properties of the fibers have been studied. Wheat gluten fibers have breaking tenacity of about 115 MPa, breaking elongation of 23%, and a Young's modulus of 5 GPa, similar to those of wool. Wheat gluten fibers have better tensile properties than soyprotein- and casein-based biomaterials. In addition, the wheat gluten fibers have resistance similar to that of PLA fibers to water in weak alkaline and slightly lower resistance in weak acidic conditions at high temperatures.