High strength antibacterial membranes consisted of nanofibrous chitosan immobilized silver nanoparticles

Chitosan (CS) has biocompatibility and biodegradability, but the bulk CS hydrogel/membranes with its poor strength and limited antibacterial property could not satisfy the practical application. Here green dissolving/regeneration and in situ reduction strategy was combined to construct high strength antibacterial CS membranes. First nanofibrous CS hydrogels were constructed through dissolving CS in LiOH/KOH/urea aqueous system via freezing–thawing process followed regeneration. Then, Ag NPs were immobilized along CS nanofibers through in situ reductions of Ag + by the NH₂ group of CS. The obtained NCM-Ag composite dry membranes are easy for storing and can quick switch to nanofibrous hydrogels as absorbing water. Size of Ag NPs can be controlled to very small until 2 nm by concentration and limited space network. Fourier transform infrared spectroscopy and X-ray photoelectron spectrometer indicated the forceful grasp ability of CS nanofibers to Ag NPs for a stable binding, mechanical property was enhanced over 100Mpa as the nanofibrous structure and chain linked by Ag coordination. The NCM-Ag membranes had excellent antibacterial activities against both Staphylococcus aureus and Escherichia coli. Moreover, such nanofibrous CS membrane exhibited good adhesive ability to tissues. Combining all these properties, NCM-Ag membranes would be potential as antibacterial adhesion barrier to accelerate wound healing.     

Chitosan/silk fibroin composite scaffolds for wound dressing

Three‐dimensional (3D) chitosan/silk fibroin (CS/SF) porous composite scaffolds have been prepared by simply coating a thin layer of CS onto spunlaced SF scaffolds via hydrogen‐bonding assembly technique, and they were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and mechanical property measurements. The results show that porous scaffolds have a pore diameter around 50–200 μm, and improved mechanical property compared with SF, resulting from strong intermolecular hydrogen bonding interactions between CS and SF, together with the maintained β‐sheet structure of SF. The medical and biological properties of the composite scaffolds were further evaluated. The results demonstrate that they possess good biocompatibility and a broad spectrum of antimicrobial properties. The in vivo animal experiments show that the composite scaffolds promote skin regeneration of rats without any teratogenic effect and inflection, thus they are very promising in the application of wound dressings. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42503.     

Biodegradable nanofibrous membrane of zein/silk fibroin by electrospinning

BACKGROUND: Electrospinning of natural polymers offers a promising approach to generate nanofibers with a similar fibrillar structure to that of native extracellular matrix. In the present work, zein/silk fibroin (SF) blends were electrospun with formic acid as solvent to fabricate bicomponent nanofibrous scaffolds for biomedical applications. RESULTS: The zein/SF electrospun nanofibers had a smaller diameter and narrower diameter distribution than pure zein nanofibers, and the average diameter gradually decreased from 265 to 230 nm with increasing SF content in the blend. The predominant presence of α‐helix zein structure and random coil form of silk I in blend fibrous membranes was confirmed from Fourier transform infrared spectral and wide‐angle X‐ray diffraction data, while conversion to the β‐sheet structure of SF was also detected. The tensile strength of the zein/SF fibrous membranes was improved as the content of SF in the blend fibers increased. A preliminary study of in vitro degradation and cytotoxicity evaluated by MTT assay indicated that biodegradable zein/SF fibrous membranes did not induce cytotoxic effects in an L929 mouse fibroblast system. CONCLUSION: Biodegradable zein/SF fibrous membranes with good mechanical properties and cytocompatibility combine the beneficial characteristics of the individual components and may be useful for biomedical applications. Copyright © 2009 Society of Chemical Industry     

Effect of chitosan on morphology and conformation of electrospun silk fibroin nanofibers

The electrospinning of silk fibroin(SF)/chitosan(CS) blends with different composition ratios was performed with formic acid as a spinning solvent. The SF/CS blends containing up to the CS content of 30% could be electrospun into the continuous fibrous structure, although pure CS was not able to be electrospun into the fibrous structure. As-spun SF/CS blend nanofibers showed smaller diameter and narrower diameter distribution than pure SF nanofibers, and the diameter gradually decreased from 450 to 130 nm with the addition of CS in blends. However, at the blend compositions with above 40 wt% chitosan, the continuous SF nanofibers containing CS beads were produced. We also investigated the influence of the methanol treatment on the secondary structure of as-spun SF or SF/CS blend nanofibers by means of ATR-IR and solid-state CP-MAS ¹³C-NMR. Comparing with the pure SF nanofibers, the conformational change of the as-spun SF/CS blend nanofibers into β-sheet was faster because the CS with rigid backbone synergistically might promote the conformational transition of SF by an intermolecular interaction.     

Influence of Post-Treatment with 75% (v/v) Ethanol Vapor on the Properties of SF/P(LLA-CL) Nanofibrous Scaffolds

In order to improve the water-resistant ability of silk fibroin (SF) and SF/P(LLA-CL) blended nanofibrous scaffolds for tissue engineering applications, 75% (v/v) ethanol vapor was used to post-treat electrospun nanofibers. SEM indicated that the treated SF and SF/P(LLA-CL) nanofibrous scaffolds maintained a nanofibrous structure and possessed good water-resistant ability. Characterization of (13)C CP-MAS NMR clarified that 75% (v/v) ethanol vapor could induce SF conformation from random coil or α-helix to β-sheet. Although the water contact showed that treated SF/P(LLA-CL) blended nanofibrous scaffolds were hydrophobic, the water uptake demonstrated that their hydrophilicity was greatly superior to those of pure P(LLA-CL) nanofibrous scaffolds. Furthermore, the treated SF/P(LLA-CL) nanofibrous scaffolds, both in dry state and wet state, could retain good mechanical properties. Therefore, 75% (v/v) ethanol vapor treatment might be an ideal method to treat SF and SF/P(LLA-CL) nanofibrous scaffolds for biomedical applications.     

丝素/羧甲基壳聚糖复合材料的制备及其在丝绸文物加固中的应用

为了对脆弱丝绸文物进行保护修复，延长其寿命，本研究以丝素蛋白（SF）、羧甲基壳聚糖（CMCS）为原料，谷氨酰胺转氨酶为交联剂，制备丝素/羧甲基壳聚糖复合材料（SF/CMCS），并将其应用于老化丝绸加固保护。选用傅里叶变换红外光谱（FT-IR）、X-射线衍射仪（XRD）、测色配色分光光度计、扫描电镜（SEM）及伺服高低温控制拉伸机对老化丝绸加固前后效果进行表征。结果表明，与老化丝绸相比，SF/CMCS加固丝绸的颜色无明显变化，物理机械性能有明显提升，抗张强度和断裂伸长率分别提升了379.12%、14.12%%，且有一定的抗菌性。     

Electrospun salicylic acid/polyurethane composite nanofibers for biomedical applications

Salicylic acid (SA)/polyurethane (PU) composite nanofiber mats were fabricated by introducing SA in PU solution during the electrospinning process. Cell viability assays showed that the as-prepared composite nanofibers had a good biocompatibility. Further, the composite mats showed good antibacterial performance against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. Easy fabrication, good mechanical properties, good biocompatibility as well as the antibacterial activity of PU nanofibers containing SA indicated their significant promise for a variety of potential medical applications such as tissue engineering, wound healing, and drug delivery system.     

Fabrication and intermolecular interactions of silk fibroin/hydroxybutyl chitosan blended nanofibers

The native extracellular matrix (ECM) is composed of a cross-linked porous network of multifibril collagens and glycosaminoglycans. Nanofibrous scaffolds of silk fibroin (SF) and hydroxybutyl chitosan (HBC) blends were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents to biomimic the native ECM via electrospinning. Scanning electronic microscope (SEM) showed that relatively uniform nanofibers could be obtained when 12% SF was blended with 6% HBC at the weight ratio of 50:50. Meanwhile, the average nanofibrous diameter increased when the content of HBC in SF/HBC blends was raised from 20% to 100%. Fourier transform infrared spectra (FTIR) and (13)C nuclear magnetic resonance (NMR) showed SF and HBC molecules existed in hydrogen bonding interactions but HBC did not induce conformation of SF transforming from random coil form to β-sheet structure. X-ray diffraction (XRD) confirmed the different structure of SF/HBC blended nanofibers from both SF and HBC. Thermogravimetry-Differential thermogravimetry (TG-DTG) results demonstrated that the thermal stability of SF/HBC blend nanofibrous scaffolds was improved. The results indicated that the rearrangement of HBC and SF molecular chain formed a new structure due to stronger hydrogen bonding between SF and HBC. These electrospun SF/HBC blended nanofibers may provide an ideal tissue engineering scaffold and wound dressing.     

再生丝素/壳聚糖共混纳米纤维的结构与性能

以98%的甲酸为溶剂,不同质量分数的再生丝素溶液和3.5%的壳聚糖溶液以质量比70∶30共混静电纺丝。测定了壳聚糖的含量对共混膜的结构及力学、溶解等性能的影响。结果表明:随着壳聚糖相对含量的增加,丝素β化程度提高,纤维结晶度增大,丝素与壳聚糖以70∶30共混时的溶失率最小;甲醇处理后,溶失率明显降低;共混纳米纤维的断裂强度随着壳聚糖相对含量的增大而增加,柔软性也逐渐提高;共混纤维膜具有优异的抗菌性。     

3D mesoporous bioactive glass/silk/chitosan scaffolds and their compatibility with human adipose-derived stromal cells

Human adipose-derived stem/stromal cells (hASCs) have been popularly studied as cell-based therapy in the field of regenerative medicine due to their ability to differentiate into several cell types. In this study, in order to improve the mechanical strength and bioactivity of scaffolds for bone tissue engineering, three types of mesoporous bioactive glasses with different shapes and compositions were dispersed in the silk fibroin/chitosan (SF/CS)-based scaffolds, which were fabricated with a combination of freezing and lyophilization. The characteristic and physical properties of these composite scaffolds were evaluated. The biocompatibility was also assessed through hASCs in vitro tests. Both Alamar Blue® and Live/Dead assay® revealed that the spherical mesoporous bioactive glass doped scaffolds enhanced cell viability and proliferation. Furthermore, the addition of spherical mesoporous bioactive glass into SF/CS scaffolds encouraged hASC osteogenic differentiation as well. These results suggested that this composite scaffold can be applicable material for bone regeneration.     

Preparation and characterization of biomimetic silk fibroin/chitosan composite nanofibers by electrospinning for osteoblasts culture

ABSTRACT: In this study, we have successfully fabricated electrospun bead-free silk fibroin [SF]/chitosan [CS] composite nanofibers [NFs] covering the whole range of CS content (0%, 25%, 50%, 75%, and 100%). SF/CS spinning solutions were prepared in a mixed solvent system of trifluoroacetic acid [TFA] and dichloromethane. The morphology of the NFs was observed by scanning electron microscope, and the average fiber diameter ranges from 215 to 478 nm. Confocal laser scanning microscopy confirms the uniform distribution of SF and CS within the composite NFs. To increase biocompatibility and preserve nanostructure when seeded with cells in culture medium, NFs were treated with an ethanol/ammonia aqueous solution to remove residual TFA and to change SF protein conformation. After the chemical treatment, SF/CS NFs could maintain the original structure for up to 54 days in culture medium. Properties of pristine and chemically treated SF/CS NFs were investigated by Fourier transform infrared spectroscopy [FT-IR], X-ray diffraction [XRD], and thermogravimetry/differential scanning calorimetry [TG/DSC]. Shift of absorption peaks in FT-IR spectra confirms the conformation change of SF from random coil to β-sheet by the action of ethanol, which is also consistent with the SF crystalline diffraction patterns measured by XRD. From TG/DSC analysis, the decomposition temperature peaks due to salt formation from TFA and protonated amines disappeared after chemical treatment, indicating complete removal of TFA by binding with ammonium ions during the treatment. This was also confirmed with the disappearance of F1s peak in X-ray photoelectron spectroscopy spectra and disappearance of TFA salt peaks in FT-IR spectra. The composite NFs could support the growth and osteogenic differentiation of human fetal osteoblastic [hFOB] cells, but each component in the composite NF shows distinct effect on cell behavior. SF promotes hFOB proliferation while CS enhances hFOB differentiation. The composite SF/CS NFs will be suitable for bone tissue engineering applications by choosing a suitable blend composition.PACS: 87.85.jf; 87.85.Rs; 68.37.Hk.     

Green electrospun nanocuprous oxide–poly(ethylene oxide)–silk fibroin composite nanofibrous scaffolds for antibacterial dressings

Cuprous oxide (Cu₂O) nanoparticles have attracted extensive attention because of their excellent optical, catalytic, antibacterial, and antifungal properties and low cost. Nano-Cu₂O–poly(ethylene oxide) (PEO)–silk fibroin (SF) composite nanofibrous scaffolds (CNSs) were fabricated through green electrospinning to impart excellent antibacterial properties onto nanofibrous scaffolds. Scanning electron microscopy revealed that the nanofibers became more nonuniform and appeared more and more as beads in the nanofibers with increasing nano-Cu₂O concentration, and no obvious morphological changes were observed after 75% EtOH vapor treatment. Transmission electron microscopy and X-ray photoelectron spectroscopy demonstrated that nano-cuprous oxide (nano-Cu₂O) was successfully loaded into the PEO–SF nanofibers. Fourier transform infrared–attenuated total reflectance spectroscopy results indicate that nano-Cu₂O did not induce SF conformation from random coils to β sheets. The SF conformation converted from random coils to β sheets after 75% EtOH vapor treatment. The results of water contact angle testing and swelling property measurement clarified that nano-Cu₂O–PEO–SF CNSs possessed outstanding hydrophilicity. Nano-Cu₂O–PEO–SF CNSs exhibited better antibacterial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria than PEO–SF nanofibrous scaffolds, and the antibacterial activity increased with increasing nano-Cu₂O concentration. Cell viability studies with pig iliac endothelial cells demonstrated that nano-Cu₂O–PEO–SF CNSs had no cytotoxicity. Nano-Cu₂O–PEO–SF CNSs are expected to be ideal biomimetic antibacterial dressings for wound healing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47730.     

Preparation and characterization of polyhydroxybutyrate‐co‐hydroxyvalerate/silk fibroin nanofibrous scaffolds for skin tissue engineering

Nanofibrous scaffolds were obtained by co‐electrospinning poly (3‐hydroxybuty‐rate‐co‐3‐hydroxyvalerate) (PHBV) and fibroin regenerated from silk in different proportions using 1,1,1,3,3,3‐hexafluoro‐2‐isopropanol (HFIP) as solvent. Field emission scanning electron microscope (FESEM) investigation showed that the fiber diameters of the nanofibrous scaffolds ranged from 190 to 460 nm. X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy analysis (FT‐IR) showed that the main structure of silk fibroin (SF) in the nanofibrous scaffold was β‐sheet. Compared to the PHBV nanofibrous scaffold, the surface hydrophilicity and water‐uptake capability of the PHBV/SF nanofibrous scaffold with 50/50 were improved. The results of cell adhesion experiment showed that the fibroblasts adhered more to the PHBV/SF nanofibrous scaffold with 50/50 than the pure PHBV nanofibrous scaffold. The proliferation of fibroblast on the PHBV/SF nanofibrous scaffold with 50/50 was higher than that on the pure PHBV nanofibrous scaffold. Our results indicated that the PHBV/SF nanofibrous scaffold with 50/50 may be a better candidate for biomedical applications such as skin tissue engineering and wound dressing. POLYM. ENG. SCI., 55:907–916, 2015. © 2014 Society of Plastics Engineers     

静电纺丝工艺参数对丝素/壳聚糖纳米纤维的形貌及直径的影响

以98%的甲酸为溶剂,不同质量分数的再生丝素溶液和3.5%的壳聚糖溶液以质量比70:30共混静电纺丝。用扫描电子显微镜(SEM)观察了丝素质量分数、电压和极距(喷丝口到收集装置的距离)对丝素/壳聚糖纳米纤维的形貌及直径的影响。正交试验结果表明:在丝素/壳聚糖溶液静电纺丝的工艺参数中,对纤维平均直径的影响因素由大到小依次为丝素质量分数、电压、极距。单因素试验表明:丝素/壳聚糖纳米纤维的平均直径及其分布范围随丝素质量分数的增加而增大;在15￣30kV范围内纤维的平均直径随电压增大而减小;当极距大于12cm时,对纤维直径影响不大。最佳工艺条件为:丝素质量分数13%,电压30kV,极距为12cm,制得的纳米纤维平均直径104nm。     

Analyzing the interactions and miscibility of silk fibroin/mucin blends

Mucin, a glycoprotein with viscoelastic properties, and silk fibroin, a protein excreted from silkworms with properties of thermal and mechanical resistance, have been probed as building blocks in the design of biomaterials. Aiming to evaluate the interaction and miscibility between mucin and fibroin, we synthesized silk fibroin and mucin (SF/MU) blends for biomedical applications. The morphological analysis of the SF/MU blends showed the presence of two phases, suggesting a partial miscibility between the polymers. The degradation temperature of the SF/MU blends increased with an increase in the silk fibroin content, indicating that silk fibroin contributed to the thermal stability of the blends. The glass transition temperature of the SF/MU blends lay between the values of the pure polymers. The Fourier-transform infrared spectroscopy results pointed out that the interaction between fibroin and mucin occurred between the amine group of silk fibroin and mucin carboxyl and hydroxyl groups. The outcomes of this work provided essential information on the miscibility of the SF/MU blends. These findings will be critical for further studies with fibroin and mucin-based biomaterials, especially in mucoadhesive systems and wound healing applications.     

Comparison of three-dimensional printing for fabricating silk fibroin-blended scaffolds

In this study, two types of scaffolds were fabricated by 3D printing. Morphology, physical properties, biochemical were evaluated. Cell morphology and distribution were observed. It was found that the silk fibroin/collagen (SF/C) scaffold-based material had significantly higher values than the silk fibroin/chitosan (SF/CS) scaffold-based material. Hematoxylin and eosin staining of the scaffolds revealed that the number of cells in the SF/C scaffold was higher. Cells grew well inside the SF/C scaffold as measured by scanning electron microscope. Reverse Transcriotion-Polymerase Chain Reaction (RT-PCR) and Western blot showed that type II collagen and Sox9 can be found in SF/C scaffold. Therefore, the SF/C scaffold exhibited better overall performance compared with the SF/CS scaffold.     

Process optimization of electrospun silk fibroin fiber mat for accelerated wound healing

Considering the outstanding biocompatibility of Bombyx mori silk fibroin, this study is designed to fabricate biomimetic nanofibrous structure made of silk fibroin, which can enhance cell activities for tissue formation. The electrospinning of blend of silk fibroin with low molecular weight poly(ethylene‐oxide) (PEO) is explored with ease of preparation for high productivities. The average diameter of electrospun silk fibroin (eSF) is decreased from 414 ± 73 to 290 ± 46 nm after PEO extraction. To induce the desired cellular activity, the surface of the eSF fibers is modified with fibronectin by using the carbodiimide chemistry method. The potential use of the obtained wound healing material is assessed by indirect cytotoxicity evaluation on normal human dermal fibroblast (NHDF) in terms of their attachment and cell proliferation. The surface‐modified eSF nanofiber mats show good support for cellular adhesion and spreading as a result of fibronectin grafting on the fiber surface, especially for cell migration inside the fibrous structure. These results demonstrate a new fabrication technique of surface‐modified silk fibroin electrospun nanofibers for biomedical application; with the ability to accelerate wound healing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3634–3644, 2013     

Electrospun silk fibroin/β-cyclodextrin citrate nanofibers as a novel biomaterial for application in controlled drug release

Abstract

A novel β-cyclodextrin-grafted silk fibroin (SF) nanofibers was successfully fabricated. The morphology and diameter of the electrospun nanofibers were characterized. FE-SEM images showed that the morphology and diameter of the nanofibers were mainly affected by weight ratio of the blend. FTIR, ¹H-NMR, DSC and TGA confirmed the crosslinking reaction between β-cyclodextrin and SF. The release rate of Ciprofloxacin was measured and observed that the SF-g-CD nanofibrous mat provided slower release of the entrapped drug when compared with SF nanofibrous mat. A mathematical analysis of the drug release data suggested that the Higuchi model was the best fitted model.     

Silk nanofibrils/chitosan composite fibers with enhanced mechanical properties

Chitosan (CS) fibers have been applied in various fields due to their biocompatibility, biodegradability, and antibacterial properties. However, weak mechanical properties remain as obstacles to further applications. Silk nanofibrils (SNFs) extracted from natural silk fibroin fibers preserve outstanding mechanical properties at the nanoscale, which are expected to impact structural programming and mechanical reinforcement for CS fibers. In this study, wet-spun CS/SNFs composite fibers were continuously collected from NaOH/ethanol coagulation. Scanning electron microscope (SEM) results showed that SNFs were uniformly distributed in the CS matrix, and obvious orientation was observed when the mass ratio of SNF/CS was 75/100. Tensile tests showed that the introduction of SNFs significantly enhanced the mechanical properties of CS fibers when the mass ratio of SNF/CS was more than 25/100. With the increasing of SNF content, the tensile strength gradually increased, and the tensile strength and modulus could be increased 2.9 times and 3.5 times, respectively, when 100% SNF was added. The improvement of mechanical properties was partially attributed to hydrogen bonding between SNF filaments and CS, which was confirmed by FTIR and XRD results. This study provides a facile and eco-friendly method to spin CS fibers with enhanced mechanical properties and a hierarchical structure.     

Preparation and characterization of biomimetic tussah silk fibroin/chitosan composite nanofibers

Tussah silk fibroin (TSF)/chitosan (CS) composite nanofibers were prepared to mimic extracellular matrix by electrospinning with hexafluoroisopropanol (HFIP) as a solvent. The viscosity and conductivity of TSF/CS blend solution were analyzed and the morphology, secondary structure, and thermal property of TSF/CS composite fibers were investigated by SEM, ¹³C CP/MAS-NMR, X-ray diffraction, and DSC Techniques. The electrospinnability of TSF solution was improved significantly by adding 10 wt% CS, and morphology of electrospun TSF nanofibers changed from flat strip to cylindrical. At the same time, the average fiber diameters decreased from 542 to 312 nm, accompanying by an obvious improvement in fiber diameter uniformity. However, when the CS content in blend solution was more than 15 wt%, the diameter of electrospun TSF/CS nanofibers appeared to be polarized which can be attributed to phase separation of the two components in composite nanofibers. Blending 10 wt% CS did not change the conformation of TSF in TSF/CS composite nanofibers, and TSF in composite nanofibers at various composition ratios had mainly taken the α-helix structure. The thermal decomposition temperature of electrospun TSF/CS composite nanofibers decreased with the increase of CS content due to the lower decomposition temperature of CS. To study the cytocompatibility and cell behavior on the TSF/CS nanofibers, human renal mesangial cells were seeded onto electrospun TSF/CS composite nanofibers. Results indicated that the addition of CS promoted cell attachment and spreading on TSF nanofibers significantly, suggesting that electrospun TSF/CS composite nanofibers could be a candidate scaffold for tissue engineering.