Modulation of protein release from biodegradable core-shell structured fibers prepared by coaxial electrospinning

Biodegradable core-shell structured fibers with poly(epsilon-caprolactone) as shell and bovine serum albumin (BSA)-containing dextran as core were prepared by coaxial electrospinning for incorporation and controlled release of proteins. BSA loading percent in the fibers and its release rate could be conveniently varied by the feed rate of the inner dope during electrospinning. With the increase in the feed rate of the inner dope, there was an associated increase in the loading percent and accelerated release of BSA. Poly(ethylene glycol) (PEG) was added to the shell section of the fibers to further finely modulate the release behavior of BSA. It was revealed that the release rate of BSA increased with the PEG percent in the shell section. By varying the feed rate of the inner dope and PEG content, most of BSA could be released from the core-shell structured fibers within the period of time ranging from 1 week to more than 1 month. The effect of the feed rate of the inner dope and addition of PEG into the shell section on the fiber morphology was also examined by scanning electron microscope.     

Melt electrospinning of biodegradable polyurethane scaffolds

Electrospinning from a melt, in contrast to from a solution, is an attractive tissue engineering scaffold manufacturing process as it allows for the formation of small diameter fibers while eliminating potentially cytotoxic solvents. Despite this, there is a dearth of literature on scaffold formation via melt electrospinning. This is likely due to the technical challenges related to the need for a well-controlled high-temperature setup and the difficulty in developing an appropriate polymer. In this paper, a biodegradable and thermally stable polyurethane (PU) is described specifically for use in melt electrospinning. Polymer formulations of aliphatic PUs based on (CH(2))(4)-content diisocyanates, polycaprolactone (PCL), 1,4-butanediamine and 1,4-butanediol (BD) were evaluated for utility in the melt electrospinning process. The final polymer formulation, a catalyst-purified PU based on 1,4-butane diisocyanate, PCL and BD in a 4/1/3M ratio with a weight-average molecular weight of about 40kDa, yielded a nontoxic polymer that could be readily electrospun from the melt. Scaffolds electrospun from this polymer contained point bonds between fibers and mechanical properties analogous to many in vivo soft tissues.     

Structural stability and release profiles of proteins from core-shell poly (DL-lactide) ultrafine fibers prepared by emulsion electrospinning

This study was aimed at assessing the potential use of emulsion electrospinning to prepare core-shell structured ultrafine fibers as carriers for therapeutic proteins. It focused on the effect of fiber structure on the release profiles and structural stability of encapsulated proteins. In the case of bovine serum albumin (BSA) which was selected as a model protein, poly-DL-lactide ultrafine fibers prepared by emulsion electrospinning using a lower volume ratio of aqueous to organic phase, showed higher structural integrity of core-shell fiber as assessed by laser confocal scanning microscope (LCSM). This structural property can reduce the initial drug burst and improved the ability of the device to provide sustained therapeutic action. Fickian release was observed for the initial 60% of protein release. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography (SEC) were used to assess the primary structure of BSA. These studies indicated that ultra-sonication caused denaturation of protein molecules, while the core-shell structured electrospun fibers protected the structural integrity of encapsulated protein during incubation in the medium. Fourier transform infrared (FTIR) analyses showed that the electrospinning process had much less effect on the secondary structure of protein than ultra-sonication. In vitro degradation study showed that the protein release from fibers led to more significant mass loss, higher molecular weight reduction and larger molecular weight distribution of the matrix residues, compared with fibers without protein inoculation. These data suggest that emulsion electrospinning can provide a useful core-sheath structure, which may serve as a promising scaffold for sustainable, controllable, and effective release of bioactive proteins in tissue engineering and other applications.     

Efficacy of engineered FVIII-producing skeletal muscle enhanced by growth factor-releasing co-axial electrospun fibers

Co-axial electrospun fibers can offer both topographical and biochemical cues for tissue engineering applications. In this study, we demonstrate the sustained treatment of hemophilia through a non-viral, tissue engineering approach facilitated by growth factor-releasing co-axial electrospun fibers. FVIII-producing skeletal myotubes were first engineered on aligned electrospun fibers in vitro, followed by implantation in hemophilic mice with or without a layer of core-shell electrospun fibers designed to provide sustained delivery of angiogenic or lymphangiogenic growth factors, which serves to stimulate the lymphatic or vascular systems to enhance the FVIII transport from the implant site into systemic circulation. Upon subcutaneous implantation into hemophilic mice, the construct seamlessly integrated with the host tissue within one month, and specifically induced either vascular or lymphatic network infiltration in accordance with the growth factors released from the electrospun fibers. Engineered constructs that induced angiogenesis resulted in sustained elevation of plasma FVIII and significantly reduced blood coagulation time for at least 2-months. Biomaterials-assisted functional tissue engineering was shown in this study to offer protein replacement therapy for a genetic disorder such as hemophilia.     

A biodegradable nanofiber scaffold by electrospinning and its potential for bone tissue engineering

Microporous, non-woven poly( epsilon -caprolactone) (PCL) scaffolds were made by electrostatic fiber spinning. In this process, polymer fibers with diameters down to the nanometer range, or nanofibers, are formed by subjecting a fluid jet to a high electric field. Mesenchymal stem cells (MSCs) derived from the bone marrow of neonatal rats were cultured, expanded and seeded on electrospun PCL scaffolds. The cell-polymer constructs were cultured with osteogenic supplements under dynamic culture conditions for up to 4 weeks. The cell-polymer constructs maintained the size and shape of the original scaffolds. Scanning electron microscopy (SEM), histological and immunohistochemical examinations were performed. Penetration of cells and abundant extracellular matrix were observed in the cell-polymer constructs after 1 week. SEM showed that the surfaces of the cell-polymer constructs were covered with cell multilayers at 4 weeks. In addition, mineralization and type I collagen were observed at 4 weeks. This suggests that electrospun PCL is a potential candidate scaffold for bone tissue engineering.     

Preparation and properties of ProNectin F-coated biodegradable hollow fibers

ProNectin F-coated biodegradable hollow fibers were newly prepared and their cytocompatibility was evaluated in vitro. Although the coating efficiency onto poly(l-lactic acid) (PLLA) and poly(lactide-co-caprolactone) [p(LA/CL)] matrices was similar, the cell adhesion properties were greatly affected by the nature of the polymer substrate. ProNectin F-coated PLLA showed about seven times higher cytocompatibility than ProNectin F-coated p(LA/CL). The single-extruded melt spinning method and the core–sheath bicomponent melt spinning method were employed to prepare PLLA hollow fibers. The effect of the spinning conditions, such as the melt draw ratio, spinneret temperature, and take-up speed, on the diameter and wall thickness of the spun fibers was studied in detail. For single-extruded melt spinning, a segmented type of spinneret was used, and the effect of the flow rate of nitrogen, which was confined in the hollow part of fibers, was studied. X-ray photographs of the drawn hollow fibers, clarified the significant molecular orientation, which was much higher than that in drawn solid PLLA fiber under identical drawing conditions. The morphology and mechanical properties of hollow fibers demonstrated an increase in the tensile strength and a decrease in the thickness of the PLLA wall with increased nitrogen flow rates and melt draw ratios for single-extruded melt spinning. These results indicate the unique characteristics of ProNectin F-coated PLLA hollow fibers, which can be successfully utilized as a biodegradable substrate.     

Hybrid nanofibrous scaffolds from electrospinning of a synthetic biodegradable elastomer and urinary bladder matrix

Synthetic materials can be electrospun into submicron or nanofibrous scaffolds to mimic extracellular matrix (ECM) scale and architecture with reproducible composition and adaptable mechanical properties. However, these materials lack the bioactivity present in natural ECM. ECM-derived scaffolds contain bioactive molecules that exert in vivo mimicking effects as applied for soft tissue engineering, yet do not possess the same flexibility in mechanical property control as some synthetics. The objective of the present study was to combine the controllable properties of a synthetic, biodegradable elastomer with the inherent bioactivity of an ECM derived scaffold. A hybrid electrospun scaffold composed of a biodegradable poly(ester-urethane)urea (PEUU) and a porcine ECM scaffold (urinary bladder matrix, UBM) was fabricated and characterized for its bioactive and physical properties both in vitro and in vivo. Increasing amounts of PEUU led to linear increases in both tensile strength and breaking strain while UBM incorporation led to increased in vitro smooth muscle cell adhesion and proliferation and in vitro mass loss. Subcutaneous implantation of the hybrid scaffolds resulted in increased scaffold degradation and a large cellular infiltrate when compared with electrospun PEUU alone. Electrospun UBM/PEUU combined the attractive bioactivity and mechanical features of its individual components to result in scaffolds with considerable potential for soft tissue engineering applications.     

The immobilization of proteins on biodegradable fibers via biotin-streptavidin bridges

This paper aims at developing novel bioactive fibrous mats for protein immobilization and for protein separation/purification. For this purpose, an amphiphilic triblock copolymer, biotinylated poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-lysine) was co-electrospun together with poly(L-lactide-co-glycolide) into ultrafine fibers approximately 2 microm in diameter, and a layer of blocking agent was coated on the fiber surfaces to block off possible non-specific binding of proteins. The biotin species retained their ability to specifically recognize and bind streptavidin, and the immobilized streptavidin could further combine with biotinylated antibodies, antigens and other biological moieties. Horseradish peroxidase-labeled streptavidin and fluorescein isothiocyanate-labeled goat globulin were used to detect the immobilizations of streptavidin and rabbit anti-goat IgG(H+L) via enzyme-linked immunoassay and confocal laser scanning microscope, respectively. The immobilized antigen was eluted from the fiber substrate with a glycine/HCl solution and the eluted antigen retained its bioactivity. Therefore, these biotin-carrying composite fibers have a variety of uses, including selective immobilization of functional proteins, antigen/antibody separation and purification, and vaccine preparation.     

Preparation of ultrafine poly(methyl methacrylate-co-methacrylic acid) biodegradable nanoparticles loaded with ibuprofen

Ibuprofen-loaded polymeric particles with around 9.2 nm in mean diameter, as determined by electron microscopy, dispersed in an aqueous media containing up to 12.8% solids were prepared by semicontinuous heterophase polymerization. The polymeric material is a (2/1 mol/mol) methyl methacrylate-co-methacrylic acid copolymer similar to Eudragit S100, deemed safe for human consumption and used in the manufacturing of drug-loaded pills as well as micro- and nanoparticles. The loading efficiency was 100%, attaining around 10–12% in drug content. Release studies showed that the drug is released from the nanoparticles at a slower rate than that in the case of free IB. Given their size as well as the pH values required for their dissolution, it is believed that this type of particles could be used as a basis for preparing nanosystems loaded with a variety of drugs.     

静电纺丝丝素蛋白水溶液制备无纺布

对不同条件下的丝素蛋白水溶液静电纺丝进行研究.在扫描电子显微镜(scanning electronic microscope,SEM)下观察了不同条件下制备出的丝素蛋白纤维的微观形貌,并用傅立叶变换红外光谱(Fourier transform infrared,FTIR)分析丝素蛋白在产物中的构象.结果 表明,丝素蛋白无纺布中的丝素蛋白以无规线团/silk Ⅰ为主,甲醇处理后,丝素蛋白无纺布中β折叠的含量明显增加.本研究为静电纺丝法制备丝素蛋白无纺布提供了新的途径,这种无纺布由于在制备过程中没有使用有机溶剂作静电纺丝溶剂,也没有共混其他聚合物,减少了溶剂残留并简化了制备过程,它将可被用于组织工程支架.     

The immobilization of proteins on biodegradable polymer fibers via click chemistry

A facile and efficient method to immobilize bioactive proteins onto polymeric substrate was established. Testis-specific protease 50 (TSP50) was immobilized on ultrafine biodegradable polymer fibers, i.e., (1) to prepare a propargyl-containing polymer P(LA90-co-MPC10) by introducing propargyl group into a cyclic carbonate monomer (5-methyl-5-propargyloxycarbonyl-1,3-dioxan-2-one, MPC) and copolymerizing it with l-lactide; (2) to electrospin the functionalized polymer into ultrafine fibers; (3) to azidize the TSP50, and (4) to perform the click reaction between the propargyl groups on the fibers and the azido groups on the protein. The TSP50-immobilized fibers can resist non-specific protein adsorptions but preserve specific recognition and combination with anti-TSP50. ELISA tests were carried out by using HRP-goat-anti-mouse-IgG(H+L) as secondary antibody and o-phenylenediamine (OPDA)/H(2)O(2) as substrate to detect the combination of immobilized TSP50 with anti-TSP50. The results showed that anti-TSP50 can be selectively adsorbed from its solution onto the TSP50-immobilized fibers in the presence of BSA of as high as 10(4) times concentration. TSP50 immobilized on the fiber and anti-TSP50 combined to the fiber were also quantitatively determined. Anti-TSP50 can be then eluted off from the fiber when pH changes. The eluted fiber can re-combine anti-TSP50 at an efficiency of 75% compared to the original TSP50-immobilized fiber. Therefore, the TSP50-immobilized fibers can be used in the detection, separation, and purification of anti-TSP50. The "click" method can lead to a universal strategy to protein immobilization.     

Effect of a low-molecular-weight cross-linkable macromer on electrospinning of poly(lactide-co-glycolide) fibers

A mixture of low-molecular-weight poly(L-lactide-co-glycolide ethylene oxide fumarate) (PLGEOF) macromer and high-molecular-weight poly(lactide-co-glycolide) (PLGA) was used to produce fibers by electrospinning. PLGEOF is a biodegradable and in situ cross-linkable terpolymer made from building blocks with excellent biocompatibility. PLGA provides the required elongational viscosity to the spinning jet while the unsaturated PLGEOF macromers contribute to in situ crosslinking of fibers and attachment of bioactive functional groups. Mechanical rheometry demonstrated that PLGEOF macromers cross-link in situ by ultraviolet radiation. The addition of PLGEOF macromer to PLGA solutions had a significant effect on size and morphology of the electrospun fibers. The morphology of the electrospun fibers changed from bead- to fiber-like with increasing PLGEOF concentration. As PLGEOF was added to 12 wt% PLGA solutions, the fiber diameter first decreased with 2% PLGEOF and then increased with the addition of 5% and 10% PLGEOF. Our results demonstrate that the fiber size initially is decreased with the addition of PLGEOF due to an increase in solution conductivity and then is increased with further PLGEOF addition due to higher viscosity of the polymerizing mixture.     

Peripheral nerve regeneration by microbraided poly(L-lactide-co-glycolide) biodegradable polymer fibers

Tiny tubes with fiber architecture were developed by a novel method of fabrication upon introducing some modification to the microbraiding technique, to function as nerve guide conduit and the feasibility of in vivo nerve regeneration was investigated through several of these conduits. Poly(L-lactide-co-glycolide) (10:90) polymer fibers being biocompatible and biodegradable were used for the fabrication of the conduits. The microbraided nerve guide conduits (MNGCs) were characterized using scanning electron microscopy to study the surface morphology and fiber arrangement. Degradation tests were performed and the micrographs of the conduit showed that the degradation of the conduit is by fiber breakage indicating bulk hydrolysis of the polymer. Biological performances of the conduits were examined in the rat sciatic nerve model with a 12-mm gap. After implantation of the MNGC to the right sciatic nerve of the rat, there was no inflammatory response. One week after implantation, a thin tissue capsule was formed on the outer surface of the conduit, indicating good biological response of the conduit. Fibrin matrix cable formation was seen inside the MNGC after 1 week implantation. One month after implantation, 9 of 10 rats showed successful nerve regeneration. None of the implanted tubes showed tube breakage. The MNGCs were flexible, permeable, and showed no swelling apart from its other advantages. Thus, these new poly(L-lactide-co-glycolide) microbraided conduits can be effective aids for nerve regeneration and repair and may lead to clinical applications.     

Release characteristics and processing-structure-performance relationship of electro-spinning curcumin-loaded polyethersulfone based porous ultrafine fibers

Abstract

Polymeric porous ultrafine fibers with different structures as drug carrier could be facilely prepared. However, the drug release characteristics and relevant mechanism of different structural porous ultrafine fibers were not well studied. In the present work, different structural Poly-Ether-Sulfone (PES) based porous ultrafine fibers, namely PES, PES/Poly-Ethylene-Glycol (PEG) and PES/Water were prepared by electro-spinning. Curcumin was chosen as drug model loaded in these fibers. Investigation of curcumin release characteristics was carried out by the total immersion in buffer solution. The surface and inner structure of PES based ultrafine fibers were studied by scanning electron microscopy (SEM) in detail. It is found that there is significant difference in the accumulate release amount and release rate with similar structure. About 92.5% of curcumin released within 600?min for PES/PEG ultrafine fibers and only 58.9% of curcumin flowed out from PES with 1000?min. In order to discuss the fact of this phenomenon, the development structure of PES based porous ultrafine fibers was studied with curcumin release. The results indicated that the curcumin release was directly involved with the structure. For PES/PEG, curcumin around the surface layer released in advance. And then, some penetrable structure emerged with PEG dissolving in the buffer solution, which result in larger specific surface area and more embedded curcumin from the interior structure of the ultrafine fibers diffusing out. For the others, curcumin release only through its own pores of ultrafine fibers. Finally, the processing-structure-performance relationship of PES based porous ultrafine fibers were confirmed by the diversity of porosity and contact angle. The research results demonstrate that PES based porous ultrafine fibers have the potential to be used as drug carrier in the drug delivery according to the practical clinical requirements.     

Effect of a low-molecular-weight cross-linkable macromer on electrospinning of poly(lactide-co-glycolide) fibers

A mixture of low-molecular-weight poly(L-lactide-co-glycolide ethylene oxide fumarate) (PLGEOF) macromer and high-molecular-weight poly(lactide-co-glycolide) (PLGA) was used to produce fibers by electrospinning. PLGEOF is a biodegradable and in situ cross-linkable terpolymer made from building blocks with excellent biocompatibility. PLGA provides the required elongational viscosity to the spinning jet while the unsaturated PLGEOF macromers contribute to in situ crosslinking of fibers and attachment of bioactive functional groups. Mechanical rheometry demonstrated that PLGEOF macromers cross-link in situ by ultraviolet radiation. The addition of PLGEOF macromer to PLGA solutions had a significant effect on size and morphology of the electrospun fibers. The morphology of the electrospun fibers changed from bead- to fiber-like with increasing PLGEOF concentration. As PLGEOF was added to 12 wt% PLGA solutions, the fiber diameter first decreased with 2% PLGEOF and then increased with the addition of 5% and 10% PLGEOF. Our results demonstrate that the fiber size initially is decreased with the addition of PLGEOF due to an increase in solution conductivity and then is increased with further PLGEOF addition due to higher viscosity of the polymerizing mixture.     

Nanofibrous scaffold from electrospinning biodegradable waterborne polyurethane/poly(vinyl alcohol) for tissue engineering application

A series of nanofibrous scaffolds, free of organic solvents, are prepared by electrospinning biodegradable waterborne polyurethane (BWPU) emulsion blending with aqueous poly(vinyl alcohol)(PVA). Tuning the proration of BWPU to PVA, various nanofibers with diameter from 370 to 964 nm are obtained. Strong intermolecular interaction existing between them benefits to the electrospun of BWPU emulsion, which is demonstrated by dynamic thermomechanical analysis and Fourier transform infrared spectroscopy. The nontoxic nanofibrous scaffolds with porous structure, which is similar to the natural extracellular matrix, favor to the attachment and proliferation of the L929 fibroblasts. Thus, the scaffolds are promising to be used as biomaterials for many natural tissues repair.     

Incorporation of biodegradable electrospun fibers into calcium phosphate cement for bone regeneration

Inherent brittleness and slow degradation are the major drawbacks for the use of calcium phosphate cements (CPCs). To address these issues, biodegradable ultrafine fibers were incorporated into the CPC in this study. Four types of fibers made of poly(ε-caprolactone) (PCL) (PCL12: 1.1 μm, PCL15: 1.4 μm, PCL18: 1.9 μm) and poly(l-lactic acid) (PLLA4: 1.4 μm) were prepared by electrospinning using a special water pool technique, then mixed with the CPC at fiber weight fractions of 1%, 3%, 5% and 7%. After incubation of the composites in simulated body fluid for 7 days, they were characterized by a gravimetric measurement for porosity evaluation, a three-point bending test for mechanical properties, microcomputer topography and scanning electron microscopy for morphological observation. The results indicated that the incorporation of ultrafine fibers increases the fracture resistance and porosity of CPCs. The toughness of the composites increased with the fiber fraction but was not affected by the fiber diameter. It was found that the incorporated fibers formed a channel-like porous structure in the CPCs. After degradation of the fibers, the created space and high porosity of the composite cement provides inter-connective channels for bone tissue in growth and facilitates cement resorption. Therefore, we concluded that this electrospun fiber-CPC composite may be beneficial to be used as bone fillers.     

Preparation of native cellulose-AgCl fiber with antimicrobial activity through one-step electrospinning

The native Cellulose-AgCl fiber have been firstly fabricated by one-step electrospinning of cellulose solution with poly(vinyl pyrrolidone) (PVP) and AgNO₃. X-ray diffraction, Scanning electron microscopy (SEM), Energy dispersive spectrometer, Thermo-gravimetric analysis and Fourier transform infrared are used to characterize the crystal structure, morphology and composition of cellulose-AgCl nanocomposites. The results of SEM indicate that the size of AgCl in cellulose fiber matrix is able to be adjusted by the addition of Polyvinylpyrrolidone (PVP). The antimicrobial activity of the nanocomposites fiber is also tested against the model microbes E. coli (Gram-negative) and S. aureus (Gram-positive). The results indicate that cellulose-AgCl nanocomposites have a good antimicrobial activity, which is improving with the decrease of AgCl size in fiber matrix. This work provides a novel and simple way to adjust the AgCl size in electrospinning cellulose matrix which can be applied as functional biomaterials.     

Preparation of PVA/PEI ultra-fine fibers and their composite membrane with PLA by electrospinning

Ultra-fine fibers of poly(vinyl alcohol)/polyethylenimine (PVA/PEI) were prepared by electrospinning of their blend solutions in water. Effects of PVA/PEI mass ratio and the polymer concentration on the fiber morphology were discussed by analysis of scanning electron micrographs. Results showed that uniform ultra-fine fibers could be obtained from an 8% PVA/PEI solution with 75:25 mass ratio. It was supposed that the introduction of PVA could promote electrospinning of PEI by weakening the intermolecular interaction and increasing solution viscosity. A composite membrane of PVA/PEI with poly(D,L-lactide) (PLA) was produced by co-electrospinning simultaneously from the aqueous 8% PVA/PEI (75:25) solution and a 20% PLA solution in N,N-dimethylformamide in two separated syringes. Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy verified the existence of PVA/PEI and PLA in the fibrous membrane. We attempted to incorporate PEI with PLA as ultra-fine fibers to diminish the acidic inflammation caused by biodegradation of PLA. The fibrous composite membrane of PVA/PEI-PLA could provide better biocompatibility and would be used as drug-delivery carriers or tissue-engineering scaffolds.     

Preparation of PVA/PEI ultra-fine fibers and their composite membrane with PLA by electrospinning

Ultra-fine fibers of poly(vinyl alcohol)/polyethylenimine (PVA/PEI) were prepared by electrospinning of their blend solutions in water. Effects of PVA/PEI mass ratio and the polymer concentration on the fiber morphology were discussed by analysis of scanning electron micrographs. Results showed that uniform ultra-fine fibers could be obtained from an 8% PVA/PEI solution with 75:25 mass ratio. It was supposed that the introduction of PVA could promote electrospinning of PEI by weakening the intermolecular interaction and increasing solution viscosity. A composite membrane of PVA/PEI with poly(D,L-lactide) (PLA) was produced by co-electrospinning simultaneously from the aqueous 8% PVA/PEI (75:25) solution and a 20% PLA solution in N,N-dimethylformamide in two separated syringes. Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy verified the existence of PVA/PEI and PLA in the fibrous membrane. We attempted to incorporate PEI with PLA as ultra-fine fibers to diminish the acidic inflammation caused by biodegradation of PLA. The fibrous composite membrane of PVA/PEI-PLA could provide better biocompatibility and would be used as drug-delivery carriers or tissue-engineering scaffolds.