Electrospun gelatin nanofibers: A facile cross-linking approach using oxidized sucrose

Advances and applications of crosslinked electrospun biomacromolecular nanofibers

Electrospinning is a technology for fabricating ultrafine fibers from natural or synthetic polymers that have novel or enhanced functional properties. These fibers have found applications in a diverse range of fields, including the food, medicine, cosmetics, agriculture, and chemical industries. However, the tendency for electrospun nanofibers to dissociate when exposed to certain environmental conditions limits many of their practical applications. The structural integrity and functional attributes of these nanofibers can be improved using physical and/or chemical crosslinking methods. This review article discusses the formation of polymeric nanofibers using electrospinning and then describes how different crosslinking methods can be used to enhance their mechanical, thermal, and biological attributes. Methods for optimizing the crosslinking reactions are discussed, including proper selection of crosslinker type and reaction conditions. Then, food, medical, and separation applications of crosslinked electrospun fibers are assessed, including in bone and skin tissue engineering, wound healing, drug delivery, air filtration, water filtration, oil removal, food packaging, food preservation, and bioactive delivery. Finally, areas where future research are needed are highlighted, as well as possible future applications of crosslinked nanofibers.

A self-healing crosslinked-xanthan gum/soy protein based film containing halloysite nanotube and propolis with antibacterial and antioxidant activity for wound healing

Traumatic multidrug-resistant bacterial infections are the most threat to wound healing. Lower extremity wounds under diabetic conditions display a significant delay during the healing process. To overcome these challenges, the utilization of protein-based nanocomposite dressings is crucial in implementing a successful regenerative medicine approach. These dressings hold significant potential as polymer scaffolds, allowing them to mimic the properties of the extracellular matrix (ECM). So, the objective of this study was to develop a nanocomposite film using dialdehyde-xanthan gum/soy protein isolate incorporated with propolis (PP) and halloysite nanotubes (HNTs) (DXG-SPI/PP/HNTs). In this protein-polysaccharide hybrid system, the self-healing capability was demonstrated through Schiff bonds, providing a favorable environment for cell encapsulation in the field of tissue engineering. To improve the properties of the DXG-SPI film, the incorporation of polyphenols found in PP, particularly flavonoids, is proposed. The synthesized films were subjected to investigations regarding degradation, degree of swelling, and mechanical characteristics. Additionally, halloysite nanotubes (HNTs) were introduced into the DXG-SPI/PP nanocomposite films as a reinforcing filler with varying concentrations of 3 %, 5 %, and 7 % by weight. The scanning electron microscope (SEM) analysis confirmed the proper embedding and dispersion of HNTs onto the DXG-SPI/PP nanocomposite films, leading to functional interfacial interactions. The structure and crystallinity of the synthesized nanocomposite films were characterized using Fourier Transform Infrared Spectrometry (FTIR) and X-ray diffraction (XRD), respectively. Moreover, the developed DXG-SPI/PP/HNTs nanocomposite films significantly improved cell growth of NIH-3T3 fibroblast cells in the presence of PP and HNTs, indicating their cytocompatibility. The antibacterial activity of the nanocomposite was evaluated against Escherichia coli (E. Coli) and Staphylococcus aureus (S. Aureus), which are commonly associated with wound infections. Overall, our findings suggest that the synthesis of DXG-SPI/PP/HNTs nanocomposite scaffolds holds great promise as a clinically relevant biomaterial and exhibits strong potential for numerous challenging biomedical applications.

A review of the current state of natural biomaterials in wound healing applications

Skin, the largest biological organ, consists of three main parts: the epidermis, dermis, and subcutaneous tissue. Wounds are abnormal wounds in various forms, such as lacerations, burns, chronic wounds, diabetic wounds, acute wounds, and fractures. The wound healing process is dynamic, complex, and lengthy in four stages involving cells, macrophages, and growth factors. Wound dressing refers to a substance that covers the surface of a wound to prevent infection and secondary damage. Biomaterials applied in wound management have advanced significantly. Natural biomaterials are increasingly used due to their advantages including biomimicry of ECM, convenient accessibility, and involvement in native wound healing. However, there are still limitations such as low mechanical properties and expensive extraction methods. Therefore, their combination with synthetic biomaterials and/or adding bioactive agents has become an option for researchers in this field. In the present study, the stages of natural wound healing and the effect of biomaterials on its direction, type, and level will be investigated. Then, different types of polysaccharides and proteins were selected as desirable natural biomaterials, polymers as synthetic biomaterials with variable and suitable properties, and bioactive agents as effective additives. In the following, the structure of selected biomaterials, their extraction and production methods, their participation in wound healing, and quality control techniques of biomaterials-based wound dressings will be discussed.

The alginate dialdehyde crosslinking on curcumin-loaded zein nanofibers for controllable release

In this study, electrospun zein/alginate dialdehyde (AD) nanofibers were prepared by green crosslinking. The degree of crosslinking could reach 50.72 %, and the diameter of electrospun fibers ranged from 446.2 to 541.8 nm. The generation of AD and the bonding of crosslinking were further confirmed by the changes on characteristic peaks and conformational ratios in the infrared spectroscopy and secondary structure analysis. High concentrations of AD led to improved thermal stabilities, mechanical properties, and hydrophobicity. And the highly crosslinked nanofibers (Z-8) owned the highest elastic modulus (24.92 MPa), tensile strength (0.28 MPa), and elongation at break (8.14 %) among five samples. Moreover, Z-8 possessed a high swelling ratio of 5.45 g/g, and a low weight loss of 6.09 %. The samples could encapsulate curcumin efficiently and show controllable release behaviors based on different AD addition. And the oxidation resistance of nanofibers gradually improved, consistent with the release performances. This study indicated AD crosslinking favored the preparation and application of zein nanofibers, and the oxidized polysaccharide acted as the green crosslinking agent, which provided reference value for the application of polysaccharides in food-related electrospun materials.

Cross-linking electrospinning

Although electrospinning (e-spinning) has witnessed rapid development in recent years, it has also been criticized by environmentalists due to the use of organic solvents. Therefore, aqueous e-spinning (green e-spinning) is considered a more attractive technique. However, considering the poor water resistance and mechanical properties of electrospun (e-spun) nanofibers, cross-linking is a perfect solution. In this review, we systematically discuss the cross-linking e-spinning system for the first time, including cross-linking strategies (in situ, liquid immersion, vapor, and spray cross-linking), cross-linking mechanism (physical and chemical cross-linking) of e-spun nanofibers, and the various applications (e.g., tissue engineering, drug delivery, water treatment, food packaging, and sensors) of cross-linked e-spun nanofibers. Among them, we highlight several cross-linking methods, including UV light cross-linking, electron beam cross-linking, glutaraldehyde (and other commonly used cross-linking agents) chemical cross-linking, thermal cross-linking, and enzymatic cross-linking. Finally, we confirm the significance of cross-linking e-spinning and reveal the problems in the construction of this system.

Novel electrospun nanofibers based on gelatin/oxidized xanthan gum containing propolis reinforced by Schiff base cross-linking for food packaging

Gelatin-based electrospun fibers are promising materials for food packaging but suffer from high hydrophilicity and weak mechanical properties. To overcome these limitations, in the current study, gelatin-based nanofibers were reinforced by using oxidized xanthan gum (OXG) as a crosslinking agent. The nanofibers' morphology was investigated through SEM, and the observations showed that the fibers' diameter was decreased by enhancing OXG content. The resultant fibers with more OXG content exhibited high tensile stress so the optimal sample obtained showed a tensile stress of 13.24 ± 0.76 MPa, which is up to 10 times more than neat gelatin fiber. Adding OXG to gelatin fibers reduced water vapor permeability, water solubility, and moisture content properties while increasing thermal stability and porosity. Additionally, the nanofibers containing propolis displayed a homogenous morphology with high antioxidant and antibacterial activities. In general, the findings suggested that the designed fibers could be used as a matrix for active food packaging.

Detailed Structural Characterization of Oxidized Sucrose and Its Application in the Fully Carbohydrate-Based Preparation of a Hydrogel from Carboxymethyl Chitosan

Oxidized sucrose (OS) is a bio-based cross-linking agent with excellent biological safety and environmental non-toxicity. However, the precise structure of OS has not been elucidated owing to its structural complexity and low purity. Accordingly, in this study, complete chemical shift assignments were performed by applying various nuclear magnetic resonance techniques, which permitted the structural and quantitative characterization of the two main OS products, each of which contained four aldehyde groups. In addition, we investigated the use of OS as a cross-linking agent in the preparation of a hydrogel from carboxymethyl chitosan (CMC), one of the most popular polysaccharides for use in biomedical applications. The primary amine groups of CMC were immediately cross-linked with the aldehyde groups of OS to form hydrogels without the requirement for a catalyst. It was found that the degree of cross-linking could be easily controlled by the feed amount of OS during CMC hydrogel preparation and the final cross-linking degree affected the thermal, swelling, and rheological properties of the obtained hydrogel. The results presented in this study are therefore expected to be applicable in the preparation of fully carbohydrate-based hydrogels for medical and pharmaceutical applications.

Nanofibrous scaffolds based on bacterial cellulose crosslinked with oxidized sucrose

In this work, oxidized sucrose (OS), which is a safe bio-based and non-toxic polyaldehyde, was used as a crosslinker in defibrillated bacterial cellulose (BC) sponges obtained by freeze-drying. For mimicking the proteins' crosslinking, BC was first modified with an aminosilane to partially replace the OH groups on the BC surface with more reactive amino groups. Further, the aminosilane-grafted bacterial cellulose (BCA) was crosslinked with OS in different concentrations and thermally cured. Functionalized bacterial celluloses showed a good thermal stability, comparable to that of unmodified cellulose and much improved mechanical properties. A threefold increase in the compression strength was obtained for the BCA scaffold after crosslinking and curing. This was correlated with the uniform pore structure emphasized by the micro-CT and SEM analyses. The OS-crosslinked BCA scaffolds were not cytotoxic and showed a porosity of around 80 %, which was almost 100 % open porosity. This study shows that the crosslinking of aminated BC scaffolds with OS allows the obtaining of 3D cellulose structures with good mechanical properties and high porosity, suitable for soft tissue engineering. The results recommend this new method as an innovative approach to obtaining biomaterial scaffolds that mimic the natural extracellular matrix.

Structural Analysis of Oxidized Sucrose and Its Application as a Crease-Resistant Crosslinking Agent

Oxidized sucrose is a non-formaldehyde crosslinking agent with many applications in polymer crosslinking and modification, such as in the preparation of starch films and protein films. However, research on the structure of oxidized sucrose is lacking. In this paper, oxidized sucrose was synthesized through selective oxidation of sodium periodate. By LC-MS, FTIR, TGA, NMR, and HRMS analyses, it was shown that oxidized sucrose existed in the form of a hydrate, and the tetraaldehyde oxidized sucrose could isomerize into the form of two six-membered hemiacetal rings. The structure of oxidized sucrose was also verified by theoretical calculations. Furthermore, the diffusional properties of oxidized sucrose were investigated by the rolling-film method. Finally, it was found that oxidized sucrose used as a crosslinking agent could effectively improve the wrinkle recovery performance of cotton fabrics.

Gelatin-based cellular solids: Fabrication, structure and properties

Although most cellular polymers are made from thermoplastics using different foaming technologies, gelatin and many other natural polymers can form hydrogels and convert them to cellular solids using various techniques, many of which differ from traditional plastic foaming, and so does their resulting structures. Cellular solids from natural hydrogels are porous materials that often exhibit a combination of desirable properties, including high specific surface area, biochemical activity, as well as thermal and acoustic insulation properties. Among natural hydrogels, gelatin-based porous materials are widely explored due to their availability, biocompatibility, biodegradability and relatively low cost. In addition, gelatin-based cellular solids have outstanding properties and are currently subject to increasing scientific research due to their potential in many applications, such as biocompatible cellular materials or biofoams to facilitate waste treatment. This article aims at providing a comprehensive review of gelatin cellular solids processing and their processing-properties-structure relationship. The fabrication techniques covered include aerogels production, mechanical foaming, blowing agents use, 3D printing, electrospinning and particle leaching methods. It is hoped that the assessment of their characteristics provides compiled information and guidance for selecting techniques and optimization of processing conditions to control material structure and properties to meet the needs of the finished products.

Bridging-induced densification strategy based on biomass-derived aldehyde tanning integrated with terminal Al(III) crosslinking towards high-performance chrome-free leather production

Chrome-free leather manufacturing has been acknowledged as a desirable option to eliminate potential environmental and human health risks of conventional chrome tanning. This work applied a sequential bridging-induced densification strategy to produce high-performance chrome-free leather with high crosslinking density derived from the biomass-derived aldehyde (BAT) crosslinking (BAT tanning of leather), followed by terminal Al(III) crosslinking (TAC). The TAC conditions for BAT tanned leather were optimized and the results suggested that the optimized conditions were as follows: the fixation pH was 4.2, the pre-penetration time was 180 min, the fixation temperature was 40 °C, and the dosage of the aluminum tanning agent (ATA) was 0.5% (based on Al₂O₃). Under the optimized conditions, the resultant BAT-TAC crust leather exhibited favorable overall performances compared with BAT crust leather in terms of higher hydrothermal stability, mechanical strengths, more pleasant uniform color, and comparable smooth grain surface. The obtained high-performance chrome-free leather is scalable, providing an avenue for designing and rationalizing other engineering technology towards high-performance eco-leather production.

Antimutagenic and Antiproliferative Activity of the Coccoloba uvifera L. Extract Loaded in Nanofibers of Gelatin/Agave Fructans Elaborated by Electrospinning

BACKGROUND

The Coccoloba uvifera L. species is currently considered an important source of compounds of high biological value such as lupeol, this is related to different biological activities of importance to human health.

OBJECTIVE

The objective of this study was to encapsulate the C. uvifera extract in nanofibers made with the biopolymers gelatin (G)/high-grade polymerization agave fructans (HDPAF) in the proportions 1:0, 1:1, 1:2, 1:3 and 0:1, through the electrospinning process, in addition to evaluating the antimutagenic and antiproliferative properties of the encapsulated extract.

METHOD

The physicochemical characteristics of the nanofibers were evaluated, as well as the antiproliferative and antimutagenic activities of the encapsulated and unencapsulated extract. SEM evaluation shows nanofibers of smooth, continuous morphology and nanometric size (50-250 nm). The TGA, FTIR-ATR, HPLC-MS analyzes reveal the presence of the extract in the nanofibers.

RESULTS

The extract did not show a mutagenic effect during the development of the Ames test, on the other hand, the MTT test showed the antiproliferative effect at the concentrations of 50 and 100 µg/mL of extract.

CONCLUSION

the extract of C. uvifera loaded in nanofibers elaborated by electrospinning with the G/HDPAF biopolymers, conserves its antimutagenic and antiproliferative properties.

Coaxial structured drug loaded dressing combined with induced stem cell differentiation for enhanced wound healing

Controllable drug-loaded dressings combined with induced stem cell differentiation have received considerable interest. In this study, a directional core-shell drug-loaded magnetocaloric response PCL/Gelatin-Antibiotics/Fe₃O₄ multifunctional dressing was developed. Due to the magnetothermal heating effect of magnetic nanoparticles and the contraction of elastic electrospun fibers, the fibers release antibiotics as needed to prevent drug-resistant infection. IV collagenase catalyzes the degradation of gelatin by achieving an optimum reaction temperature, the purpose of which is also to reduce the viscosity of liquid gelatin and promote the release of drugs. With the sacrifice of gelatin, the directional structure of scaffold and the internal steric hindrance promoted stem cell differentiation and wound healing. The expression of Vimentin, VEGF, bFGF, TGF-β, and THY1 was confirmed by fluorescence immunostaining and RT-PCR. Western blot was used to detect expression of Vimentin, collagen, CD34, and CD31 in the (5/5, v/v) PCL/gelatin scaffold incubated with mouse wound. Therefore, the functional fibers can significantly accelerate the healing process.

Natural ‘Green’ Sugar-Based Treatment for Hair Styling

A major drawback of current hair styling treatments is their use of toxic chemicals, such as thioglycolates, sulfites, formaldehyde, and others. Exposure to such chemicals is not only harmful to hairstylists but also to the millions who routinely receive hair treatments. The present research discusses the development of a benign sucrose-based crosslinker consisting of aldehyde groups to stabilize hair via crosslinking amine groups in keratin. ATR-FTIR and 1H-NMR were used to confirm functional groups on sucrose. Hair straightening was carried out by crosslinking via flat ironing. Crosslinked hair swatches were hung in a high humidity environment and subjected to repeated washings with shampoo to characterize the permanency of the treatment. Hair straightening through crosslinking was found to be durable to high humidity and repeat shampoo washings. The tensile characteristics of hair, such as fracture stress, strain, and Young’s modulus, were unaffected by the treatment. SEM images showed no damage to surface scales. The sucrose-based crosslinker could be used to create curls in straight hair as well.

Evaluation of Freeze Drying and Electrospinning Techniques for Saffron Encapsulation and Storage Stability of Encapsulated Bioactives

Saffron extract was encapsulated into a gelatin matrix by means of electrospinning and freeze drying techniques and the degradation kinetics of bioactive compounds were evaluated during their storage at 4, 24, and 35 °C as compared to non-encapsulated control. The encapsulation efficiency, thermal properties, storage stability, morphology, and diameter distribution of the encapsulated saffron extract were evaluated as output parameters. In general, both encapsulation techniques demonstrated superior retention of bioactive compounds compared to samples without encapsulation during the entire storage period. Electrospinning and freeze drying techniques were able to retain at least 96.2 and 93.7% of crocin, respectively, after 42 days of storage at 35 °C with the 15% saffron extract. The half-life (t1/2) time parameter for the control sample (with 15% saffron extract without encapsulation) was 22 days at 4 °C temperature, while that encapsulated by electrospinning was 138 days and that obtained for freeze drying was 77 days, The half-lives were longer at lower temperatures. The encapsulation efficiency of crocin, picrocrocin, and safranal associated with the electro-spun gelatin fibers were 76.3, 86.0, and 74.2%, respectively, and in comparison, the freeze drying encapsulation efficiencies were relatively lower, at 69.0, 74.7, and 65.8%, respectively. Electro-spun gelatin fibers also had higher melting and denaturation temperatures of 78.3 °C and 108.1 °C, respectively, as compared to 65.4 °C and 93.2 °C, respectively, for freeze-dried samples. Thus, from all respects, it was concluded that electrospinning was a better and more effective technique than freeze drying in terms of preserving saffron bioactive compounds.

Biotechnological Applications of Polymeric Nanofiber Platforms Loaded with Diverse Bioactive Materials

This review article highlights the critical research and formative works relating to nanofiber composites loaded with bioactive materials for diverse applications, and discusses the recent research on the use of electrospun nanofiber incorporating bioactive compounds such as essential oils, herbal bioactive components, plant extracts, and metallic nanoparticles. Inevitably, with the common advantages of bioactive components and polymer nanofibers, electrospun nanofibers containing bioactive components have attracted intense interests for their applications in biomedicine and cancer treatment. Many studies have only concentrated on the production and performance of electrospun nanofiber loaded with bioactive components; in this regard, the features of different types of electrospun nanofiber incorporating a wide variety of bioactive compounds and their developing trends are summarized and assessed in the present article, as is the feasible use of nanofiber technology to produce products on an industrial scale in different applications.

Electrospun nanofibers promote wound healing: theories, techniques, and perspectives

At present, the clinical strategies for treating chronic wounds are limited, especially when it comes to pain relief and rapid wound healing. Therefore, there is an urgent need to develop alternative treatment methods. This paper provides a systematic review on recent researches on how electrospun nanofiber scaffolds promote wound healing and how the electrospinning technology has been used for fabricating multi-dimensional, multi-pore and multi-functional nanofiber scaffolds that have greatly promoted the development of wound healing dressings. First, we provide a review on the four stages of wound healing, which is followed by a discussion on the evolvement of the electrospinning technology, what is involved in electrospinning devices, and factors affecting the electrospinning process. Finally, we present the possible mechanisms of electrospun nanofibers to promote wound healing, the classification of electrospun polymers, cell infiltration favoring fiber scaffolds, antibacterial fiber scaffolds, and future multi-functional scaffolds. Although nanofiber scaffolds have made great progress as a type of multi-functional biomaterial, major challenges still remain for commercializing them in a way that fully meets the needs of patients.

Highly Osmotic Oxidized Sucrose-Crosslinked Polyethylenimine for Gene Delivery Systems

In this work, highly osmotic oxidized sucrose-crosslinked polyethylenimine (SP2K) polymers were developed for gene delivery systems, and the transfection mechanism is examined. First, periodate-oxidized sucrose and polyethylenimine 2K (PEI2K) were crosslinked with various feed ratios via reductive amination. The synthesis was confirmed by ¹H NMR and FTIR. The synthesized SP2K polymers could form positively charged (~40 mV zeta-potential) and nano-sized (150–200 nm) spherical polyplexes with plasmid DNA (pDNA). They showed lower cytotoxicity than PEI25K but concentration-dependent cytotoxicity. Among them, SP2K7 and SP2K10 showed higher transfection efficiency than PEI25K in both serum and serum-free conditions, revealing the good serum stability. It was found that SP2K polymers possessed high osmolality and endosome buffering capacity. The transfection experiments with cellular uptake inhibitors suggest that the transfection of SP2K polymers would progress by multiple pathways, including caveolae-mediated endocytosis. It was also thought that caveolae-mediated endocytosis of SP2K polyplexes would be facilitated through cyclooxygenase-2 (COX-2) expression induced by high osmotic pressure of SP2K polymers. Confocal microscopy results also supported that SP2K polyplexes would be internalized into cells via multiple pathways and escape endosomes efficiently via high osmolality and endosome buffering capacity. These results demonstrate the potential of SP2K polymers for gene delivery systems.

Electrospun Polyvinylpyrrolidone-Gelatin and Cellulose Acetate Bi-Layer Scaffold Loaded with Gentamicin as Possible Wound Dressing

Acceleration of wound healing can be achieved with the use of wound dressings. Through the electrospinning technique, a polymeric scaffold composed of two layers was processed: a gelatin and polyvinylpyrrolidone layer with gentamicin, and a second layer of cellulose acetate. The conditions for the electrospinning process were standardized for voltage parameters, feed flow and the distance from the injector to the collector. Once the values of the main variables for the electrospinning were optimized, a three-hour processing time was established to allow the separation of the material from the collector. The obtained material was characterized by observations on scanning electron microscopy, Fourier transform infrared spectroscopy and thermal analysis; contact angle measurement was performed to evaluate wettability properties, and antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus were evaluated using the Kirby–Bauer test. The obtained fibers that form the bi-layer scaffold present diameters from 100 to 300 nm. The scaffold presents chemical composition, thermal stability, wettability characteristics and antibacterial activity that fulfill the proposal from this study, based on obtaining a scaffold that could be used as a drug delivery vehicle and a wound dressing material.

Oxysucrose polyaldehyde: A new hydrophilic crosslinking reagent for anti-crease finishing of cotton fabrics

For the first time, oxidized sucrose (oxysucrose) was used as a hydrophilic crosslinking reagent instead of conventional anti-crease reagents for cotton fabrics. In this research, the partial oxidization of sucrose with sodium periodate generated multiple aldehydes, which acted as multifunctional cross-linkers and endowed cotton fabrics with anti-crease and hydrophilic function. The results showed that the oxysucrose-treated cotton fabrics obtained the maximum crease recovery angle of 245°, durable press rating of 3.0, and whiteness index of 82.8. Importantly, the oxysucrose-treated samples showed better hydrophilicity that overcomes the hydrophobization deficiency of anti-creased cotton fabrics treated with previously reported dimethylol dihydroxy ethylene urea (DMDHEU), glutaraldehyde (GA), and 1, 2, 3, 4,-butanetetracarboxylic acid (BTCA). The etherification reaction between the aldehyde group of oxysucrose and the hydroxyl group of cellulose was investigated and the possible crosslinking and anti-crease mechanism was proposed.

Muscle tissue engineering in fibrous gelatin: implications for meat analogs

Bioprocessing applications that derive meat products from animal cell cultures require food-safe culture substrates that support volumetric expansion and maturation of adherent muscle cells. Here we demonstrate scalable production of microfibrous gelatin that supports cultured adherent muscle cells derived from cow and rabbit. As gelatin is a natural component of meat, resulting from collagen denaturation during processing and cooking, our extruded gelatin microfibers recapitulated structural and biochemical features of natural muscle tissues. Using immersion rotary jet spinning, a dry-jet wet-spinning process, we produced gelatin fibers at high rates (~ 100 g/h, dry weight) and, depending on process conditions, we tuned fiber diameters between ~ 1.3 ± 0.1 μm (mean ± SEM) and 8.7 ± 1.4 μm (mean ± SEM), which are comparable to natural collagen fibers. To inhibit fiber degradation during cell culture, we crosslinked them either chemically or by co-spinning gelatin with a microbial crosslinking enzyme. To produce meat analogs, we cultured bovine aortic smooth muscle cells and rabbit skeletal muscle myoblasts in gelatin fiber scaffolds, then used immunohistochemical staining to verify that both cell types attached to gelatin fibers and proliferated in scaffold volumes. Short-length gelatin fibers promoted cell aggregation, whereas long fibers promoted aligned muscle tissue formation. Histology, scanning electron microscopy, and mechanical testing demonstrated that cultured muscle lacked the mature contractile architecture observed in natural muscle but recapitulated some of the structural and mechanical features measured in meat products.

Cross-Linking Strategies for Electrospun Gelatin Scaffolds

Electrospinning is an exceptional technology to fabricate sub-micrometric fiber scaffolds for regenerative medicine applications and to mimic the morphology and the chemistry of the natural extracellular matrix (ECM). Although most synthetic and natural polymers can be electrospun, gelatin frequently represents a material of choice due to the presence of cell-interactive motifs, its wide availability, low cost, easy processability, and biodegradability. However, cross-linking is required to stabilize the structure of the electrospun matrices and avoid gelatin dissolution at body temperature. Different physical and chemical cross-linking protocols have been described to improve electrospun gelatin stability and to preserve the morphological fibrous arrangement of the electrospun gelatin scaffolds. Here, we review the main current strategies. For each method, the cross-linking mechanism and its efficiency, the influence of electrospinning parameters, and the resulting fiber morphology are considered. The main drawbacks as well as the open challenges are also discussed.

Enhancing Strength of Wool Fiber Using a Soy Flour Sugar-Based "Green" Cross-linker

This study presents the preparation and use of a "green" cross-linker derived from a waste soy flour sugar (SFS) mixture to cross-link keratin in wool fibers to increase their tensile properties. Earlier studies of keratin cross-linking involved chemicals such as glyoxal and glutaraldehyde that are toxic to humans. In addition, their effectiveness in improving tensile properties has been significantly lower than obtained in this study using modified SFS. Characterization of SFS using ¹³C NMR revealed the presence of five sugars having different molecular lengths. Oxidation of SFS using sodium periodate resulted in multiple aldehyde groups, as confirmed by ¹H NMR and attenuated total reflection Fourier-transform infrared (ATR-FTIR). The oxidized SFS (OSFS) when used to cross-link the amine groups from the wool keratin resulted in 36 and 56% increase in the tensile strength and Young's modulus of the fibers, respectively. These significant increases in strength and Young's modulus were a result of having multiple aldehyde groups on each sugar molecule as well as different molecular lengths of sugars, which favored cross-links of multiple lengths within the cortical cell matrix of wool fibers. The cross-linking between the aldehyde groups in OSFS and amine groups in wool fibers was confirmed using ATR-FTIR and from the color change resulting from the Maillard reaction as well as decrease in moisture absorption by the fibers. Stronger wool fibers can not only increase the efficiencies of wool fiber spinning and weaving and reduce yarn and fabric defects but can also allow spinning finer yarns from the same fibers. Oxidized sugars with optimum molecular lengths can be used to cross-link other biological proteins as well, replacing the currently used toxic cross-linkers.

Electrospun polycaprolactone/collagen nanofibers cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide and genipin facilitate endothelial cell regeneration and may be a promising candidate for vascular scaffolds

Purpose

A promising vascular scaffold must possess satisfying mechanical properties, great hemocompatibility, and favorable tissue regeneration. Combining natural with synthetic materials is a popular method of creating/enhancing such scaffolds. However, the effect of additional modification on the materials requires further exploration.

Materials and methods

We selected polycaprolactone (PCL), which has excellent mechanical properties and biocompatibility and can be combined with collagen. Electrospun fibers created using a PCL/collagen solution were used to fashion mixed nanofibers, while separate syringes of PCL and collagen were used to create separated nanofibers, resulting in different pore sizes. Mixed and separated nanofibers were cross-linked with glutaraldehyde (GA), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and genipin; hence, we named them as mixed GA, mixed EDC (ME), mixed genipin (MG), separated GA, separated EDC (SE), and separated genipin (SG).

Results

Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction showed that cross-linking did not affect the main functional groups of fibers in all groups. ME, MG, SE, and SG met the requisite mechanical properties, and they also resisted collagenase degradation. In hemocompatibility assays, only ME and MG demonstrated ideal safety. Furthermore, ME and MG presented the greatest cytocompatibility. For vascular scaffolds, rapid endothelialization helps to prevent thrombosis. According to human umbilical vein endothelial cell migration on different nanofibers, ME and MG are also successful in promoting cell migration.

Conclusion

ME and MG may be promising candidates for vascular tissue engineering. The study suggests that collagen cross-linked by EDC/N-hydroxysuccinimide or genipin facilitates endothelial cell regeneration, which could be of great benefit in tissue engineering of vascular scaffolds.

The effects of cross-linked/uncross-linked electrospun fibrinogen/polycaprolactone nanofibers on the proliferation of normal human epidermal keratinocytes

The aim of this study was an investigation on the proliferation rate of normal human epidermal keratinocytes (NHEK) on the cross-linked and uncross-linked fibrinogen/polycaprolactone (Fbg/PCL) nanofibers to determine a suitable scaffold for skin tissue engineering. Nanofibrous scaffolds were prepared by electrospinning of different weight ratios of Fbg to PCL and were analyzed as morphology, surface chemical properties and cytocompatibility by scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, respectively. The diameters of the blended uncross-linked scaffolds were in the range of 124±43 nm–209±155 nm. Cross-linking of scaffolds with glutaraldehyde did not make a significant change in the diameter of blended scaffolds in 16 h. Cross-linking also improved the tensile strength and weight loss rate of scaffolds. However, cross-linking demonstrated an unfavorable effect on the attachment and proliferation of NHEK cells. The proliferation study revealed that uncross-linked scaffolds containing 50% and 70% Fbg provide a better environment for the growth of NHEK cells, and can be considered promising scaffolds in tissue engineering applications.

Synthesis of a thin-layer gelatin nanofiber mat for cultivating retinal cell

Thin-layer gelatin nanofiber mats were fabricated as a biodegradable scaffold for proliferating human retinal pigment epithelium. Together with MTT assay, the glucose consumption rate, lactate formation, and lactate dehydrogenase activity of the human retinal pigment epithelium cells—on the gelatin nanofibers—were analyzed as indicators for cell growth and viability. The results showed that gelatin nanofiber did not make any toxic effect on the cells and the growth rate was comparable to the tissue culture plates. Using the fabricated thin-layer nanofibers let the by-product to leave which in turn cause less adverse effect on the cells. The biodegradability and stability of the gelatin nanofibers were optimized as a function of reaction time.

Characterisation of electrospun gelatine nanofibres encapsulated with Moringa oleifera bioactive extract

BACKGROUND

Drumstick (Moringa oleifera) leaves have been used as a folk herbal medicine across many cultures since ancient times. This is most probably due to presence of phytochemicals possessing antioxidant properties, which could retard oxidative stress, and their degenerative effect. The current study deals with nanoencapsulation of Moringa oleifera (MO) leaf ethanolic extract within fish sourced gelatine matrix using electrospinning technique.

RESULTS

The total phenolic and flavonoid content, radical scavenging (IC₅₀ ) and metal reducing properties were 67.0 ± 2.5 mg GAE g^-1 sample 32.0 ± 0.5 mg QE g^-1 extract, 0.08 ± 0.01 mg mL^-1 and 510 ± 10 µmol eq Fe(II) g^-1 extract, respectively. Morphological and spectroscopic analysis of the fibre mats confirmed successful nanoencapsulation of MO extract within defect free nanofibres via electrospinning process. The percentage encapsulation efficiency (EE) was between 80% and 85%. Furthermore, thermal stability of encapsulated fibres, especially at 3% and 5% of core loading content, was significantly improved. Toxicological analysis revealed that the extract in its original and encapsulated form was safe for oral consumption.

CONCLUSION

Overall, the present study showed the potential of ambient temperature electrospinning process as a safe nanoencapsulation method, where MO extract retained its antioxidative capacities. © 2016 Society of Chemical Industry.

Fabrication and characterization of electrospun gelatin nanofibers crosslinked with oxidized phenolic compounds

In this study, the ability of oxidized phenolic compounds of tannic, gallic, ferulic and caffeic acids to crosslink gelatin (G) was investigated. The electrospun crosslinked gelatin nanofibers were assessed in terms of gelatin solution properties, fiber morphology, thermal properties, FTIR spectra, XRD pattern and antioxidant activity. Tannic acid showed the most crosslinking activity towards gelatin (13.3 vs 7.44, 4.65, and 3.45% for caffeic, gallic and ferulic, respectively). Crosslinking enhanced roughly electrical conductivity of gelatin solution while the surface tension and viscosity reduced. According to scanning electron microscopy (SEM) results, the fibrous structure of crosslinked gelatin nanofibers didn't change while their diameter increased to the highest value of 280nm for gelatin-tannic. Gelatin-gallic sample showed the highest total phenolic content (86.3mg gallic acid equivalent/g) and antioxidant activity (86.5%). Surprisingly, from differential scanning calorimetry (DSC) curves, it was found that crosslinking led to the reduction of thermal stability of gelatin nanofibers.

Electrospun protein nanofibers in healthcare: A review

Electrospun nanofibers are being utilized for a wide range of healthcare applications. A plethora of natural and synthetic polymers are exploited for their ability to be electrospun and replace the complex habitat provided by the extracellular matrix for the cells. The fabrication of nanofibers can be tuned to act as a multicarrier system to deliver drugs, growth factors and health supplements etc. in a sustained manner. Owing to its pliability, nanofibers reached its heights in tissue engineering and drug delivery applications. This review mainly focuses on various standardized parameters and optimized blending ratios for animal and plant proteins to yield fine, continuous nanofibers for effective utilization in various healthcare applications.

Fabrication of FGF-2 immobilized electrospun gelatin nanofibers for tissue engineering

Conjugated gelatin nanofibers were fabricated by electrospinning, followed by a simple glutaraldehyde cross-linking procedure and avidin conjugation. Then, biotinylated growth factors were immobilized onto the surface of the fibers through avidin-biotin covalent binding. The immobilization of growth factors was confirmed through immunostaining using fluorescence microscopy and microplate spectrophotometry. Adipose derived stem cells (ASCs) were cultured to examine the effect of immobilized growth factors on cell proliferation using the cell counting Kit-8 (CCK-8) assay. Gelatin nanofibers with no growth factors attached and growth factors in suspension within media were used as controls. Growth factors were successfully immobilized onto the surface, in amounts corresponding to the concentrations applied, and increased cell proliferation to a higher extend than growth factors in suspension. Our results suggest that this controllable scaffolding strategy provides an effective system for growth factors delivery in tissues, suitable for engineering applications.

Graphene oxide decorated electrospun gelatin nanofibers: Fabrication, properties and applications

Gelatin nanofiber fabricated by electrospinning process is found to mimic the complex structural and functional properties of natural extracellular matrix for tissue regeneration. In order to improve the physico-chemical and biological properties of the nanofibers, graphene oxide is incorporated in the gelatin to form graphene oxide decorated gelatin nanofibers. The current research effort is focussed on the fabrication and evaluation of physico-chemical and biological properties of graphene oxide-gelatin composite nanofibers. The presence of graphene oxide in the nanofibers was established by transmission electron microscopy (TEM). We report the effect of incorporation of graphene oxide on the mechanical, thermal and biological performance of the gelatin nanofibers. The tensile strength of gelatin nanofibers was increased from 8.29±0.53MPa to 21±2.03MPa after the incorporation of GO. In order to improve the water resistance of nanofibers, natural based cross-linking agent, namely, dextran aldehyde was employed. The cross-linked composite nanofibers showed further increase in the tensile strength up to 56.4±2.03MPa. Graphene oxide incorporated gelatin nanofibers are evaluated for bacterial activity against gram positive (Staphylococcus aureus) and gram negative (Escherichia coli) bacteria and cyto compatibility using mouse fibroblast cells (L-929 cells). The results indicate that the graphene oxide incorporated gelatin nanofibers do not prevent bacterial growth, nevertheless support the L-929 cell adhesion and proliferation.

Preparation and characterization of electrospun in-situ cross-linked gelatin-graphite oxide nanofibers

Electrospun gelatin(Gel) nanofibers scaffold has such defects as poor mechanical property and quick degradation due to high solubility. In this study, the in situ cross-linked electrospinning technique was used for the production of gelatin nanofibers. Deionized water was chosen as the spinning solvent and graphite oxide (GO) was chosen as the enhancer. The morphological structure, porosity, thermal property, moisture absorption, and moisture retention performance, hydrolysis resistance, mechanical property, and biocompatibility of the produced nanofibers were investigated. Compared with in situ cross-linked gelatin nanofibers scaffold, in situ cross-linked Gel-GO nanofibers scaffold has the following features: (1) the hydrophilicity, moisture absorption, and moisture retention performance slightly reduce, while the hydrolysis resistance is improved; (2) the breaking strength, breaking elongation, and Young's modulus are significantly improved; (3) the porosity slightly reduces while the biocompatibility considerably increases. The in situ cross-linked Gel-GO nanofibers scaffold is likely to be applied in such fields as drug delivery and scaffold for skin tissue engineering.

Fabrication of cationized gelatin nanofibers by electrospinning for tissue regeneration

A green fabrication approach has been developed to produce biocompatible and non-cytotoxic cationically modified gelatin nanofibers with enhanced biological performance.