Interaction of gelatin with polyenes modulates antifungal activity and biocompatibility of electrospun fiber mats

Bacillus Metabolites: Compounds, Identification and Anti-Candida albicans Mechanisms

Candida albicans seriously threatens human health, especially for immunosuppressed groups. The antifungal agents mainly include azoles, polyenes and echinocandins. However, the few types of existing antifungal drugs and their resistance make it necessary to develop new antifungal drugs. Bacillus and its metabolites has antifungal activity against pathogenic fungi. This review introduces the application of Bacillus metabolites in the control of C. albicans in recent years. Firstly, several compounds produced by Bacillus spp. are listed. Then the isolation and identification techniques of Bacillus metabolites in recent years are described, including high-precision separation technology and omics technology for the separation of similar components of Bacillus metabolites. The mechanisms of Bacillus metabolites against C. albicans are distinguished from the inhibition of pathogenic fungi and inhibition of the fungal virulence factors. The purpose of this review is to systematically summarize the recent studies on the inhibition of pathogenic fungi by Bacillus metabolites. The review is expected to become the reference for the control of pathogenic fungi such as C. albicans and the application of Bacillus metabolites in the future.

Scaffolds in the microbial resistant era: Fabrication, materials, properties and tissue engineering applications

Due to microbial infections dramatically affect cell survival and increase the risk of implant failure, scaffolds produced with antimicrobial materials are now much more likely to be successful. Multidrug-resistant infections without suitable prevention strategies are increasing at an alarming rate. The ability of cells to organize, develop, differentiate, produce a functioning extracellular matrix (ECM) and create new functional tissue can all be controlled by careful control of the extracellular microenvironment. This review covers the present state of advanced strategies to develop scaffolds with antimicrobial properties for bone, oral tissue, skin, muscle, nerve, trachea, cardiac and other tissue engineering applications. The review focuses on the development of antimicrobial scaffolds against bacteria and fungi using a wide range of materials, including polymers, biopolymers, glass, ceramics and antimicrobials agents such as antibiotics, antiseptics, antimicrobial polymers, peptides, metals, carbon nanomaterials, combinatorial strategies, and includes discussions on the antimicrobial mechanisms involved in these antimicrobial approaches. The toxicological aspects of these advanced scaffolds are also analyzed to ensure future technological transfer to clinics. The main antimicrobial methods of characterizing scaffolds’ antimicrobial and antibiofilm properties are described. The production methods of these porous supports, such as electrospinning, phase separation, gas foaming, the porogen method, polymerization in solution, fiber mesh coating, self-assembly, membrane lamination, freeze drying, 3D printing and bioprinting, among others, are also included in this article. These important advances in antimicrobial materials-based scaffolds for regenerative medicine offer many new promising avenues to the material design and tissue-engineering communities.

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Antibacterial, antifungal and antibiofilm scaffolds.

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Antimicrobial scaffold fabrication techniques.

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Antimicrobial biomaterials for tissue engineering applications.

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Antimicrobial characterization methods of scaffolds.

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Bone, oral tissue, skin, muscle, nerve, trachea, cardiac, among other applications.

Chondroitin sulfate-based composites: a tour d'horizon of their biomedical applications

Chondroitin sulfate (CS), a natural anionic mucopolysaccharide, belonging to the glycosaminoglycan family, acts as the primary element of the extracellular matrix (ECM) of diverse organisms. It comprises repeating units of disaccharides possessing β-1,3-linked N-acetyl galactosamine (GalNAc), and β-1,4-linked D-glucuronic acid (GlcA), and exhibits antitumor, anti-inflammatory, anti-coagulant, anti-oxidant, and anti-thrombogenic activities. It is a naturally acquired bio-macromolecule with beneficial properties, such as biocompatibility, biodegradability, and immensely low toxicity, making it the center of attention in developing biomaterials for various biomedical applications. The authors have discussed the structure, unique properties, and extraction source of CS in the initial section of this review. Further, the current investigations on applications of CS-based composites in various biomedical fields, focusing on delivering active pharmaceutical compounds, tissue engineering, and wound healing, are discussed critically. In addition, the manuscript throws light on preclinical and clinical studies associated with CS composites. A short section on Chondroitinase ABC has also been canvassed. Finally, this review emphasizes the current challenges and prospects of CS in various biomedical fields.

Influence of substrate temperature parameter on electrospinning process: example of application to the formation of gelatin fibers

The substrate temperature was investigated to broaden the applicability of controlling the morphology of polymeric fibers produced during the electrospinning process. A laboratory electrospinning setup was designed using a substrate heated in a temperature range of 25 °C to 100 °C. A gelatin polymer was used as an example to obtain beads-free gelatin fibers by fixing the main electrospinning parameters. Based on XRD, FTIR, and DSC techniques, the electrospun gelatin fibers did not show any change in their chemical composition up to 100 °C. Heating the substrate at 50 °C may be the best selection factor to obtain gelatin fibers; the fiber diameters experienced a significant decrease from 680 ± 140 nm to 420 ± 120 nm with increasing substrate temperature from 25 to 50 °C, respectively. They showed stability of the diameter at 380 ± 130 nm and 390 ± 130 nm when increasing substrate temperatures from 75 to 100 °C, respectively, with a significant variation in their diameter distribution. Therefore, this ability to control the electrospinning process using a heated substrate makes it promising for fabricating electrospun beads-free fibers of biopolymers such as gelatin for tissue engineering and drug delivery carriers.

Electrospun nanofibers food packaging: trends and applications in food systems

Food safety is a bottleneck problem. In order to provide information about advanced and unique food packaging technique, this study summarized the advancements of electrospinning technique. Food packaging is a multidisciplinary area involving food science, food engineering, food chemistry, and food microbiology, and the interest in maintaining the freshness and quality of foods has grown considerably. For this purpose, electrospinning technology has gained much attention due to its unique functions and superior processing. Sudden advancements of electrospinning have been rapidly incorporated into research. This review summarized some latest information about food packaging and different materials used for the packaging of various foods such as fruits, vegetables, meat, and processed items. Also, the use of electrospinning and materials used for the formation of nanofibers are discussed in detail. However, in food industry, the application of electrospun nanofibers is still in its infancy. In this study, different parameters, structures of nanofibers, features and fundamental properties are described briefly, while polymers fabricated through electrospinning with advances in food packaging films are described in detail. Moreover, this comprehensive review focuses on the polymers used for the electrospinning of nanofibers as packaging films and their applications for variety of foods. This will be a valuable source of information for researchers studying various polymers for electrospinning for application in the food packaging industry.

Effectiveness of Core-Shell Nanofibers Incorporating Amphotericin B by Solution Blow Spinning Against Leishmania and Candida Species

The aim of this study was to develop polymeric nanofibers for controlled administration of Amphotericin B (AmpB), using the solution centrifugation technique, characterizing its microstructural and physical properties, release rate, and activity against Leishmania and Candida species. The core-shell nanofibers incorporated with AmpB were synthesized by Solution Blow Spinning (SBS) and characterized by scanning electron microscopy (SEM), differential scanning calorimetry, X-Ray diffraction, and drug release assay. In vitro leishmanicidal and antifungal activity were also evaluated. Fibrous membranes with uniform morphology and smooth surfaces were produced. The intensity of the diffraction peaks becomes slightly more pronounced, assuming the increased crystallization in PLA/PEG at high AmpB loadings. Drug release occurred and the solutions with nanofibers to encourage greater incorporation of AmpB showed a higher concentration. In the results of the experiment with promastigotes, the wells treated with nanofibers containing concentrations of AmpB at 0.25, 0.5, and 1%, did not have any viable cells, similar to the positive control. Various concentrations of AmpB improved the inhibition of fungal growth. The delivery system based on PLA/PEG nanofibers was properly developed for AmpB, presenting a controlled release and a successful encapsulation, as well as antifungal and antileishmanial activity.

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.

A gelatin/collagen/polycaprolactone scaffold for skin regeneration

Background

A tissue-engineered skin substitute, based on gelatin (“G”), collagen (“C”), and poly(ε-caprolactone) (PCL; “P”), was developed.

Method

G/C/P biocomposites were fabricated by impregnation of lyophilized gelatin/collagen (GC) mats with PCL solutions, followed by solvent evaporation. Two different GC:PCL ratios (1:8 and 1:20) were used.

Results

Differential scanning calorimetry revealed that all G/C/P biocomposites had characteristic melting point of PCL at around 60 °C. Scanning electron microscopy showed that all biocomposites had similar fibrous structures. Good cytocompatibility was present in all G/C/P biocomposites when incubated with primary human epidermal keratinocytes (PHEK), human dermal fibroblasts (PHDF) and human adipose-derived stem cells (ASCs) in vitro. All G/C/P biocomposites exhibited similar cell growth and mechanical characteristics in comparison with C/P biocomposites. G/C/P biocomposites with a lower collagen content showed better cell proliferation than those with a higher collagen content in vitro. Due to reasonable mechanical strength and biocompatibility in vitro, G/C/P with a lower content of collagen and a higher content of PCL (GC_LP_H) was selected for animal wound healing studies. According to our data, a significant promotion in wound healing and skin regeneration could be observed in GC_LP_H seeded with adipose-derived stem cells by Gomori’s trichrome staining.

Conclusion

This study may provide an effective and low-cost wound dressings to assist skin regeneration for clinical use.

Current development of biodegradable polymeric materials for biomedical applications

In the last half-century, the development of biodegradable polymeric materials for biomedical applications has advanced significantly. Biodegradable polymeric materials are favored in the development of therapeutic devices, including temporary implants and three-dimensional scaffolds for tissue engineering. Further advancements have occurred in the utilization of biodegradable polymeric materials for pharmacological applications such as delivery vehicles for controlled/sustained drug release. These applications require particular physicochemical, biological, and degradation properties of the materials to deliver effective therapy. As a result, a wide range of natural or synthetic polymers able to undergo hydrolytic or enzymatic degradation is being studied for biomedical applications. This review outlines the current development of biodegradable natural and synthetic polymeric materials for various biomedical applications, including tissue engineering, temporary implants, wound healing, and drug delivery.

Effect of annealing temperature on mechanical and antibacterial properties of Cu-bearing titanium alloy and its preliminary study of antibacterial mechanism

Cu-bearing titanium alloys are designed and studied as a novel medical metal material with antibacterial function. However, the addition of Cu would affect the mechanical properties of titanium alloy more or less, especially the ductility, despite its excellent antibacterial property. Thus, the aim of this study was to optimize the heat treatment for Cu-bearing titanium alloys in order to achieve a balance of satisfactory mechanical, antibacterial and other properties. In this study, Ti6Al4V-5 wt% Cu alloy was fabricated, and then different annealing treatments with various heating temperatures (700-910 °C) were employed on the alloy. The effects of heating temperature on microstructure evolution, mechanical properties, corrosion resistance and antibacterial performance of Ti6Al4V-5Cu alloy were systematically studied. It was found that annealing at 740 °C for Ti6Al4V-5Cu alloy showed the best comprehensive properties of high strength, excellent ductility, corrosion resistance and antibacterial performance. The Ti₂Cu phases played an important role in the mechanical property and antibacterial performance for Ti6Al4V-5Cu alloy, and bacteria preferred to adhere on the α phase region, rather than the β or globule Ti₂Cu region.

Fabrication and characterization of chicken feather keratin/polysaccharides blended polymer coated nonwoven dressing materials for wound healing applications

In this research work, three kinds of nonwoven wound dressings were developed from chicken feather keratin (CFK-NW), keratin‑sodium alginate (CFK-SA-NW) and keratin-chitosan (CFK-CS-NW) and characterized using FTIR and SEM. The physical characteristics such as air permeability, thickness and areal density test results revealed the suitability of fabricated materials for wound dressing applications. CFK-SA-NW and CFK-CS-NW indicated a positive antibacterial effect against Gram's positive Staphylococcus aureus and Gram's negative Klebsiella pneumoniae and Escherichia coli bacteria with the zone of inhibition enhanced over >2.0 cm. Moreover, the biomedical potentials of dressing materials has been investigated by cell viability and cytotoxicity tests. Further, the wound healing ability was demonstrated using in vivo model (Albino Wistar rat). The fabricated materials exhibited good support for cell viability and a strong cytocompatibility. Furthermore, the hundred percent wound healing ability of CFK-CS-NW, CFK-SA-NW, CFK-NW and untreated control rats was observed at 15, 17, 21 and 23 days, respectively, Moreover, the wound healing potential of CFK-CS-NW and CFK-SA-NW was found to be better than that of CFK-NW and control group of rats. The outcome of the present study discloses the prospective applications of the developed materials as wound dressing biomaterial.

A Single-Step Surface Modification of Electrospun Silica Nanofibers Using a Silica Binding Protein Fused with an RGD Motif for Enhanced PC12 Cell Growth and Differentiation

In this study, a previously known high-affinity silica binding protein (SB) was genetically engineered to fuse with an integrin-binding peptide (RGD) to create a recombinant protein (SB-RGD). SB-RGD was successfully expressed in Escherichia coli and purified using silica beads through a simple and fast centrifugation method. A further functionality assay showed that SB-RGD bound to the silica surface with an extremely high affinity that required 2 M MgCl₂ for elution. Through a single-step incubation, the purified SB-RGD proteins were noncovalently coated onto an electrospun silica nanofiber (SNF) substrate to fabricate the SNF-SB-RGD substrate. SNF-SB-RGD was characterized by a combination of scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and immunostaining fluorescence microscopy. As PC12 cells were seeded onto the SNF-SB-RGD surface, significantly higher cell viability and longer neurite extensions were observed when compared to those on the control surfaces. These results indicated that SB-RGD could serve as a noncovalent coating biologic to support and promote neuron growth and differentiation on silica-based substrates for neuronal tissue engineering. It also provides proof of concept for the possibility to genetically engineer protein-based signaling molecules to noncovalently modify silica-based substrates as bioinspired material.

Novel pH-responsive tobramycin-embedded micelles in nanostructured multilayer-coatings of chitosan/heparin with efficient and sustained antibacterial properties

To endow orthopaedic implants with satisfactory antibacterial properties, the design and development of antibiotic coating on the surface of implants is highly desired. In this work a novel and facile strategy was developed to form pH-responsive layer-by-layer (LbL) films implanted with polymeric micelles as nano-vehicles loaded with charge-weak antibiotic drugs, enabling high drug loading efficiency. Negatively charged tobramycin (Tob)-embeded heparin miscells (HET) and positively charged chitosan (CHT) were exploited as a pH-responsive LBL multilayer building block, respectively. The formation mechanism and pH-stimulated release behavior of the Tob-contained heparin micelles were studied. The characterization on the morphologies, chemical compositions and hydrophilicity of the modified surface confirmed the successuful deposition of the Tob-loaded CHT/HET multilayers coatings on the polydopamine-modified Ti surface. The drug release profiles displayed fast release at pH 7.4 and slow release after exposure to weakly acidic environments. Antibacterial tests indicated that the Tob-embed CHT/HET nanostructured multilayers not only strongly inhibited initial bacterial adhesion, but also disruptted biofilm formation. Particularly, this functional coatings showed "long-term antibacterial" pattern in acid condition. Meanwhile, MC3T3 cells showed acceptable adhesion, spread and proliferation on the multilayer coatings in cytocompatible studies. In a word, these multilayer coatings incorporated with a wide variety of antibiotics show promisiong applications in preventing postoperative infection and resolving unmet clinical need.

The Effect of Laminin Surface Modification of Electrospun Silica Nanofiber Substrate on Neuronal Tissue Engineering

In this study, we first synthesized a slow-degrading silica nanofiber (SNF2) through an electrospun solution with an optimized tetraethyl orthosilicate (TEOS) to polyvinyl pyrrolidone (PVP) ratio. Then, laminin-modified SNF2, namely SNF2-AP-S-L, was obtained through a series of chemical reactions to attach the extracellular matrix protein, laminin, to its surface. The SNF2-AP-S-L substrate was characterized by a combination of scanning electron microscopy (SEM), Fourier transform–infrared (FTIR) spectroscopy, nitrogen adsorption/desorption isotherms, and contact angle measurements. The results of further functional assays show that this substrate is a biocompatible, bioactive and biodegradable scaffold with good structural integrity that persisted beyond 18 days. Moreover, a synergistic effect of sustained structure support and prolonged biochemical stimulation for cell differentiation on SNF2-AP-S-L was found when neuron-like PC12 cells were seeded onto its surface. Specifically, neurite extensions on the covalently modified SNF2-AP-S-L were significantly longer than those observed on unmodified SNF and SNF subjected to physical adsorption of laminin. Together, these results indicate that the SNF2-AP-S-L substrate prepared in this study is a promising 3D biocompatible substrate capable of sustaining longer neuronal growth for tissue-engineering applications.

Novel bifurcation stents coated with bioabsorbable nanofibers with extended and controlled release of rosuvastatin and paclitaxel

A novel bifurcation stent coated with bioabsorbable nanofibers that deliver the extended and controlled release of rosuvastatin and paclitaxel was developed. Bioabsorbable bifurcation stents, consisting of a double-slit tubular main body and two spiral branches, were manufactured. Bi-layered poly (lactic-co-glycolic acid) nanofibers that contained rosuvastatin and paclitaxel were used for treating the stents. Various properties of the fabricated stents, including compression strengths, collapse pressure, water contact angle and flow properties within a circulation model, were quantified. In vitro nanofibrous elution chromatography assays from the drug-loading bifurcation stents were carried out for the release patterns of pharmaceuticals. The effectiveness of eluted rosuvastatin and paclitaxel in inhibiting the adhesion of platelets as well as the proliferation of smooth muscle cells (SMCs) were studied, respectively. The experimental results suggest that bioabsorbable nanofibrous bifurcation stents released high concentrations of rosuvastatin and paclitaxel for 27 and 70 days, respectively. The eluted drugs of rosuvastatin and paclitaxel effectively reduced adherent platelets and the proliferation of SMCs. The developed bioabsorbable nanofibrous bifurcation stents herein may provide a promising means of treating cardiovascular bifurcation lesions.

Antimicrobial gelatin-based elastomer nanocomposite membrane loaded with ciprofloxacin and polymyxin B sulfate in halloysite nanotubes for wound dressing

Bacterial infection is a major problem world-wide, especially in wound treatment where it can severely prolong the healing process. In this study, a double drug co-delivery elastic antibacterial nanocomposite was developed by combining ciprofloxacin (CPX) and polymyxin B sulfate-loaded halloysite clay nanotubes (HNTs-B) into a gelatin elastomer. CPX nanoparticles which act against both gram positive and gram-negative bacterium were dispersed directly in the matrix, and polymyxin B sulfate was loaded in HNTs and then distributed into the matrix. The effect of CPX and HNTs-B content on the physical properties, cytotoxicity, fibroblast adhesion and proliferation, in vitro drug release behavior and anti-bacterial properties were systematically investigated. The ciprofloxacin crystals and HNT-B were distributed in the matrix uniformly. The HNTs in the drug loading system not only enhanced the matrix' tensile strength but also slowed down the release rate of the high dissoluble polymyxin B sulfate. When the amount of HNT in the matrix increased, the thermal stability and tensile strength also increased but the polymyxin B sulfate release rate decreased because the HNTs prevented the drug release inside. All the nanocomposites exhibited antimicrobial activity against both gram-negative and gram-positive bacteria with the dual combination of drugs released from the nanocomposites. Furthermore, this kind of gelatin-based nanocomposites possesses higher water-absorbing quality, low cytotoxicity, adaptable biodegradability and good elasticity which can satisfy the requirements for an ideal biomaterial for use in wound healing applications.

Antibacterial modification of PET with quaternary ammonium salt and silver particles via electron-beam irradiation

Quaternary ammonium compound 2-dimethyl-2-hexadecyl-1-methacryloxyethyl ammonium bromide (DEHMA) was synthesized and grafted onto polyester (PET) fibers with acrylic acid (AA) via electron-beam (EB) irradiation process. The grafted fibers were soaked in AgNO₃ solution for further improving antibacterial efficiency. SEM, FTIR, EDX, and XPS were used to characterize the treated PET samples. The antibacterial efficacy testing showed the grafted PET samples inactivated all Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli O157:H7) in 10min. After coated with silver ions, the antibacterial efficacy of the grafted PET with silver against S. aureus improved significantly. The EB irradiation process only caused a small degree of the breaking strength loss of the grafted PET fabrics which is acceptable in practical application.

A novel layer-structured scaffold with large pore sizes suitable for 3D cell culture prepared by near-field electrospinning

Electrospinning is a powerful method for preparing porous materials that can be applied as biomedical materials for implantation or tissue engineering or as scaffolds for 3D cell culture experiments. However, this technique is limited in practical applications because the pore size of 3D scaffolds directly prepared by conventional electrospinning is usually less than several tens of micrometres, which may not be suitable for 3D cell culture and tissue growth. To allow for satisfactory 3D cell culture and tissue engineering, the pore size of the scaffold should be controllable according to the requirement of the specific cells to be cultured. Here, we show that layer-structured scaffolds with pore sizes larger than 100μm can be obtained by stacking meshes prepared by direct-writing using the near-field electrospinning (NFES) technique. In the study, we prepared composite scaffolds made of polycaprolactone (PCL) and hydroxyapatite (HAp) via the above-mentioned method and tested the effectiveness of the novel scaffold in cell culture using mouse pre-osteoblast cells (MC3T3-E1). The pore size and the degradability of the PCL/HAp scaffolds were characterized. The results showed that the average pore size of the scaffolds was 167μm, which was controllable based on the required application; the degradation rate was controllable depending on the ratio of PCL to HAp. The biocompatibility of the scaffolds in vitro was studied, and it was found that the scaffolds showed no toxicity and that the cells could effectively attach, proliferate, and differentiate in the 3D skeleton of the scaffolds. Our studies showed that a simple modification of the preparation procedure can lead to a new way to fabricate novel layer-structured 3D scaffolds with controllable structures and pore sizes suitable for practical applications in implantation, tissue engineering and 3D cell culture.

Nano-fibrous and ladder-like multi-channel nerve conduits: Degradation and modification by gelatin

We recently fabricated multi-channel PLLA nerve conduits (NCs, conduits diameter: ~3mm, channels diameter: ~200μm) with nano-fibrous microstructure (NNCs) and ladder-like microstructure (LNCs), and found the nanofibers in the NNCs promote differentiation of nerve stem cells (NSCs) into neurons. In the present study, we evaluated the degradation profile of NNCs and LNCs, and observed that NNCs degraded too fast to implant. To delay the degradation and retain the nano-scale effect of NNCs, we used gelatin to wrap (2% w/v gelatin) or embed (8% w/v gelatin) NNCs and LNCs via vacuum infusion and chemical cross-linking with genipin. NNCs-wrapped maintained their original nano-fibrous microstructure, but NNCs-embedded presented a porous morphology without nanofibers appearing. Incorporation of gelatin did not change their compressive moduli, but increased the creep recovery ratios of LNCs and NNCs. In vitro degradation revealed that integrity was maintained and the mass loss was <5% for NNCs-wrapped after 10weeks, in comparison with 15% mass loss and collapsed structure of the pure NNCs after 4weeks. Meanwhile, there were no obvious changes in the degradation of LNCs with modification. Nerve stem cells (NSCs) were then seeded onto the six NCs represented as: NNCs, NNCs-wrapped, NNCs-embedded, LNCs, LNCs-wrapped, and LNCs-embedded. Immunocytochemistry analysis demonstrated that gelatin coating enhanced the adhesion and proliferation of NSCs, and the NNCs-wrapped scaffold promoted the differentiation proportion of NSCs into neurons from 25.8% (on pure NNCs) to 53.4% after 14days of seeding. On the other hand, only 14.3% of neurons were derived from the differentiation of the seeded NSCs on the NNCs-embedded. NNCs-wrapped would be a good choice for future studies in nerve injury repair in vivo due to its appropriate degradation rate, flexibility, and nano-scale effect.

Comparative study of kerateine and keratose based composite nanofibers for biomedical applications

In this work, two forms of keratins, kerateine (KR) and keratose (KO), were fabricated respectively into electrospun nanofibers by combination with polyurethane (PU). The differences of the structure and material properties between KR and KO based fibers were investigated by SEM observation, ATR-FTIR, XRD, contact angle, tensile test, in vitro degradation and cytocompatibility assay. The results indicated that the KR based nanofibers exhibited a higher tensile modulus, lower fracture strain and slower degradation rate, mainly due to the reformation of disulfide crosslinking between the regenerated cysteines in KR after the reductive extraction. The KO based nanofibers demonstrated a stronger hydrophilic property and higher water uptake ability due to the cysteic acid residues resulting from the oxidative extraction. Furthermore, the combination of keratins, regardless of KR or KO, could obviously improve the cytocompatibility of PU, especially in the cell attachment stage.

Fabrication and preliminary study of a biomimetic tri-layer tubular graft based on fibers and fiber yarns for vascular tissue engineering

Designing a biomimetic and functional tissue-engineered vascular graft has been urgently needed for repairing and regenerating defected vascular tissues. Utilizing a multi-layered vascular scaffold is commonly considered an effective way, because multi-layered scaffolds can easily simulate the structure and function of natural blood vessels. Herein, we developed a novel tri-layer tubular graft consisted of Poly(L-lactide-co-caprolactone)/collagen (PLCL/COL) fibers and Poly(lactide-co-glycolide)/silk fibroin (PLGA/SF) yarns via a three-step electrospinning method. The tri-layer vascular graft consisted of PLCL/COL aligned fibers in inner layer, PLGA/SF yarns in middle layer, and PLCL/COL random fibers in outer layer. Each layer possessed tensile mechanical strength and elongation, and the entire tubular structure provided tensile and compressive supports. Furthermore, the human umbilical vein endothelial cells (HUVECs) and smooth muscle cells (SMCs) proliferated well on the materials. Fluorescence staining images demonstrated that the axially aligned PLCL/COL fibers prearranged endothelium morphology in lumen and the circumferential oriented PLGA/SF yarns regulated SMCs organization along the single yarns. The outside PLCL/COL random fibers performed as the fixed layer to hold the entire tubular structure. The in vivo results showed that the tri-layer vascular graft supported cell infiltration, scaffold biodegradation and abundant collagen production after subcutaneous implantation for 10weeks, revealing the optimal biocompatibility and tissue regenerative capability of the tri-layer graft. Therefore, the specially designed tri-layer vascular graft will be beneficial to vascular reconstruction.

Effects of copper nanoparticles in porous TiO2 coatings on bacterial resistance and cytocompatibility of osteoblasts and endothelial cells

Copper (Cu) has garnered increasing interest due to its excellent antimicrobial activity and important roles in human metabolism. Although the biological effects of Cu have been studied, the effects of Cu nanoparticles (NPs) on cell behavior are not well understood. In this study, porous TiO₂ coatings doped with different amounts of Cu NPs (designated as 0 Cu, 0.3 Cu, and 3.0 Cu) are deposited on titanium by micro-arc oxidation (MAO). The Cu NPs coated samples exhibit excellent antibacterial activity against Staphylococcus aureus (S. aureus). In vitro cytocompatibility evaluation discloses that 0 Cu and 0.3 Cu have no toxicity to osteoblasts but 3.0 Cu shows cytotoxicity. 0.3 Cu promotes proliferation and adhesion of osteoblasts and enhances extracellular matrix mineralization (ECM), but has little effects on the alkaline phosphatase activity (ALP) and collagen secretion. Surprisingly, the Cu NPs coated samples show a different behavior with endothelial cells. Both 0.3 Cu and 3.0 Cu show no cytotoxicity on endothelial cells and promote cell proliferation. Production of nitric oxide (NO) and secretion of vascular endothelial growth factor (VEGF) by the endothelial cells are observed from the Cu NPs doped TiO₂ coatings.

Electrospun vein grafts with high cell infiltration for vascular tissue engineering

Demand is increasing for functional small-diameter vascular grafts (diameter<6mm) for clinical arterial replacement. In the present study, we develop a bilayer poly(ε-caprolactone, PCL) fibrous vascular graft consisting of a thin internal layer made of longitudinally aligned fibers and a relatively thick highly porous external layer. The internal layer provides a scaffold with the necessary mechanical strength and enhances the growth of endothelial cells, whereas the external layer enhances cell motility through the scaffold bulk. The biocompatibility and biological performance of bilayer fibrous scaffolds are evaluated by in vivo experiments, molecular biology, and histology studies. Our bilayer scaffolds demonstrate much better fiber alignment and higher porosity than do normal electrospun vascular grafts with randomly distributed fibers. The results suggest that the proposed grafts can overcome limitations owing to the inadequate porosity, small pores, and poor cell infiltration of scaffolds fabricated by conventional electrospinning. The unique structure of bilayer scaffolds is satisfactory and promotes cell proliferation, collagen-fiber deposition, and ingrowth of smooth muscle cells and endothelial cells in vivo. The results of this study illustrate the strong potential of such bilayer fibrous scaffolds for vascular tissue engineering and regeneration.

Novel poly(ε-caprolactone)/gelatin wound dressings prepared by emulsion electrospinning with controlled release capacity of Ketoprofen anti-inflammatory drug

In the present study, a single and binary Ketoprofen-loaded mats of ultrathin fibers were developed by electrospinning and their physical properties and drug release capacity was analyzed. The single mat was prepared by solution electrospinning of poly(ε-caprolactone) (PCL) with Ketoprofen at a weight ratio of 5wt%. This Ketoprofen-containing PCL solution was also used as the oil phase in a 7:3 (wt/wt) emulsion with gelatin dissolved in acidified water. The resultant stable oil-in-water (O/W) emulsion of PCL-in-gelatin, also containing Ketoprofen at 5wt%, was electrospun to produce the binary mat. Cross-linking process was performed by means of glutaraldehyde vapor on the electrospun binary mat to prevent dissolution of the hydrophilic gelatin phase. The performed characterization indicated that Ketoprofen was successfully embedded in the single and binary electrospun mats, i.e. PCL and PCL/gelatin, and both mats showed high hydrophobicity but poor thermal resistance. In vitro release studies interestingly revealed that, in comparison to the single PCL electrospun mat, the binary PCL/gelatin mat significantly hindered Ketoprofen burst release and exhibited a sustained release capacity of the drug for up to 4days. In addition, the electrospun Ketoprofen-loaded mats showed enhanced attachment and proliferation of L929 mouse fibroblast cells, presenting the binary mat the highest cell growth yield due to its improved porosity. The here-developed electrospun materials clearly show a great deal of potential as novel wound dressings with an outstanding controlled capacity to release drugs.

Fabrication and characterization of nanofibers of honey/poly(1,4-cyclohexane dimethylene isosorbide trephthalate) by electrospinning

We report the fabrication of novel nanofibers using naturally occurring antimicrobial honey incorporated in poly(1,4-cyclohexane dimethylene isosorbide trephthalate) (PICT) for the potential wound dressing applications. We fabricated PICT/honey using three blend ratios 90:10, 85:15 and 80:20 respectively. Morphology of PICT nanofibers and PICT/honey nanofibers was observed under Scanning Electron Microscope and it showed bead-free nanofibers. Fourier Transform Infrared Spectroscope was used to confirm the presence of honey in PICT electrospun nanofibers. Tensile strength of PICT/honey nanofibers was slightly reduced with variation in effect of elongation. Water contact angle measurements were done with the static contact angle by a contact angle meter, which showed that hydrophobicity was decreased by adding the honey. The XPS spectra showed that honey was present in the PICT/honey nanofibers. The release behavior of honey was investigated by UV-visible Spectrophotometer. The release was complete in 15min and the maximum release of honey was 72mg/L in 10min. Therefore, PICT/honey nanofibers having 15% concentration of honey are suitable for good elastic behavior and tensile strength as compared to other concentrations of honey.

Design and fabrication of auxetic PCL nanofiber membranes for biomedical applications

The main objective of this study was to fabricate poly (ε-caprolactone) (PCL)-based auxetic nanofiber membranes and characterize them for their mechanical and physicochemical properties. As a first step, the PCL nanofibers were fabricated by electrospinning with two different thicknesses of 40μm (called PCL thin membrane) and 180μm (called PCL thick membrane). In the second step, they were tailored into auxetic patterns using femtosecond laser cut technique. The physicochemical and mechanical properties of the auxetic nanofiber membranes were studied and compared with the conventional electrospun PCL nanofibers (non-auxetic nanofiber membranes) as a control. The results showed that there were no significant changes observed among them in terms of their chemical functionality and thermal property. However, there was a notable difference observed in the mechanical properties. For instance, the thin auxetic nanofiber membrane showed the magnitude of elongation almost ten times higher than the control, which clearly demonstrates the high flexibility of auxetic nanofiber membranes. This is because that the auxetic nanofiber membranes have lesser rigidity than the control nanofibers under the same load which could be due to the rotational motion of the auxetic structures. The major finding of this study is that the auxetic PCL nanofiber membranes are highly flexible (10-fold higher elongation capacity than the conventional PCL nanofibers) and have tunable mechanical properties. Therefore, the auxetic PCL nanofiber membranes may serve as a potent material in various biomedical applications, in particular, tissue engineering where scaffolds with mechanical cues play a major role.