Deciphering the mechanism of protein interaction with silk fibroin for drug delivery systems

Silk fibroin (SF) is an exceptional drug delivery carrier with respect to stabilizing, protecting, and delivering sensitive biologics. A synopsis of thermodynamic, static light scattering, hydrophobicity probing, and nanoparticle tracking analyses served as a basis to decipher the mechanism of interaction between SF and two model proteins, protamine and polylysine. The impact of salts aiding (chaotropic), not affecting (neutral), or opposing (cosmotropic) SF unfolding was a major determinant, ranging from complete abolishment to maximal interaction efficacy. Evidence is provided, that the underlying mechanism of the remarkable ability to tailor drug/SF interaction throughout such large ranges and by appropriate salt selection is the control of structural breakdown of SF micelles as present in pure SF ad initium. This study provides a mechanistically justified and hypothesis driven blueprint for future experimental designs addressing the controlled interaction of biologics and SF.     

Silk fibroin derived polypeptide-induced biomineralization of collagen

Silk fibroin (SF) is extensively investigated in osteoregenerative therapy as it combines extraordinary mechanical properties and directs calcium-phosphate formation. However, the role of the peptidic fractions in inducing the protein mineralization has not been previously decoded. In this study, we investigated the mineralization of fibroin-derived polypeptides (FDPs), which were obtained through the chymotryptic separation of the hydrophobic crystalline (Cp) fractions and of the hydrophilic electronegative amorphous (Cs) fractions. When immersed in simulated body fluid (SBF), only Cs fragments demonstrated the formation of carbonated apatite, providing experimental evidence that the mineralization of SF is dictated exclusively by its electronegative amino-acidic sequences. The potential of Cs to conceptually mimic the role of anionic non-collagenous proteins in biomineralization processes was investigated via their incorporation (up to 10% by weight) in bulk osteoid-like dense collagen (DC) gels. Within 6 h in SBF, apatite was formed in DC-Cs hybrid gels, and by day 7, carbonated hydroxylapatite crystals were extensively formed. This accelerated 3-D mineralization resulted in a nine-fold increase in the compressive modulus of the hydrogel. The tailoring of the mineralization and mechanical properties of hydrogels through hybridization with FDPs could potentially have a significant impact on cell delivery and bone regenerative medicine.     

丝素蛋白在组织工程细胞支架方面的研究进展

近年来有关丝素蛋白用做细胞培养基质材料的研究表明，丝素蛋白对多数种类细胞的体外培养表现出较高的细胞附着率和增殖率，与胶原相当，可以用作组织工程细胞支架材料，应用到组织工程皮肤、软骨、血管等诸多领域。本文就丝素蛋白用于细胞培养的研究现状及丝素蛋白在组织工程细胞支架方面的应用前景做一综述。     

Electrosonic ejector microarray for drug and gene delivery

We report on development and experimental characterization of a novel cell manipulation device—the electrosonic ejector microarray—which establishes a pathway for drug and/or gene delivery with control of biophysical action on the length scale of an individual cell. The device comprises a piezoelectric transducer for ultrasound wave generation, a reservoir for storing the sample mixture and a set of acoustic horn structures that form a nozzle array for focused application of mechanical energy. The nozzles are micromachined in silicon or plastic using simple and economical batch fabrication processes. When the device is driven at a particular resonant frequency of the acoustic horn structures, the sample mixture of cells and desired transfection agents/molecules suspended in culture medium is ejected from orifices located at the nozzle tips. During sample ejection, focused mechanical forces (pressure and shear) are generated on a microsecond time scale (dictated by nozzle size/geometry and ejection velocity) resulting in identical “active” microenvironments for each ejected cell. This process enables a number of cellular bioeffects, from uptake of small molecules and gene delivery/transfection to cell lysis. Specifically, we demonstrate successful calcein uptake and transfection of DNA plasmid encoding green fluorescent protein (GFP) into human malignant glioma cells (cell line LN443) using electrosonic microarrays with 36, 45 and 50 μm diameter nozzle orifices and operating at ultrasound frequencies between 0.91 and 0.98 MHz. Our results suggest that efficacy and the extent of bioeffects are mainly controlled by nozzle orifice size and the localized intensity of the applied acoustic field.     

Enhanced cell adhesion on silk fibroin via lectin surface modification

Various tissue engineering (TE) approaches are based on silk fibroin (SF) as scaffold material because of its superior mechanical and biological properties compared to other materials. The translation of one-step TE approaches to clinical application has generally failed so far due to the requirement of a prolonged cell seeding step before implantation. Here, we propose that the plant lectin WGA (wheat germ agglutinin), covalently bound to SF, will mediate cell adhesion in a time frame acceptable to be part of a one-step surgical intervention. After the establishment of a modification protocol utilizing carbodiimide chemistry, we examined the attachment of cells, with a special focus on adipose-derived stromal cells (ASC), on WGA-SF compared to pure native SF. After a limited time frame of 20 min the attachment of ASCs to WGA-SF showed an increase of about 17-fold, as compared to pure native SF. The lectin-mediated cell adhesion further showed an enhanced resistance to trypsin (as a protease model) and to applied fluid shear stress (mechanical stability). Moreover, we could demonstrate that the adhesion of ASCs on the WGA-SF does not negatively influence proliferation or differentiation potential into the osteogenic lineage. To test for in vitro immune response, the proliferation of peripheral blood mononuclear cells in contact with the WGA-SF was determined, showing no alterations compared to plain SF. All these findings suggest that the WGA modification of SF offers important benefits for translation of SF scaffolds into clinical applications.     

A family of bioreducible poly(disulfide amine)s for gene delivery

A family of bioreducible poly(disulfide amine)s, which differ in the length of polymethylene spacer [–(CH₂)_n–] in the main chain and the side chain, has been synthesized. These bioreducible poly(disulfide amine)s exhibit local environment specific degradability and are associated with lower cytotoxicity than branched poly(ethylenimine) (bPEI, 25 kDa). These cationic polymers also show higher buffering capacity and protonation degree than bPEI, facilitating the endosomal escape of carried genetic materials. The transfection efficiency of these agents is oligomethylene length dependent. Poly(cystaminebisacrylamide-spermine) [poly(CBA-SP)], poly(cystaminebisacrylamide-bis(3-aminopropyl)-1,3-propanediamine) [poly(CBA-APPD)], and poly(cyxtaminebisacrylamide-bis(3-aminopropyl)-ethylenediamine) [ploy(CBA-APED)] with longer propylene [–(CH₂)₃–] side spacer, demonstrate higher transfection efficacy than the counterpart poly(cystaminebisacrylamide-bis(2-aminoethyl)-1,3-propanediamine) [poly(CBA-AEPD)] and poly(cystaminebisacrylamide-triethylenetetramine) [poly(CBA-TETA)], which have shorter ethylene [–(CH₂)₂–] side spacer. The poly(CBA-SP), poly(CBA-APPD), poly(CBA-APED) with the main chain spacer of –(CH₂)₄–, –(CH₂)₃–, –(CH₂)₂– demonstrate similar transfection efficiency, indicating the length of polymer main chain spacer has less influence on transfection efficiency. However, with the same short ethylene [–(CH₂)₂–] side spacer, poly(CBA-AEPD), with the longer main chain oligomethylene units [–(CH₂)₃–], showed relatively higher transfection efficiency than poly(CBA-TETA), having shorter main chain oligomethylene units [–(CH₂)₂–]. Of these polymeric carriers, poly(CBA-SP) demonstrated the highest transfection in the C2C12 cell line, while poly(CBA-APED) showed the highest transfection in the HeLa cell line. All of these agents showed greater transfection activity than commercialized bPEI 25 kDa. The poly(disulfide amine)s are promising safe and efficient non-viral vectors for gene delivery.     

Silk fibroin porous scaffolds by N2O foaming

Silk fibroin has acquired increasing interest for biomedical applications, and namely for the fabrication of scaffolds for tissue engineering, because of its highly positive biological interaction and the possibility to adapt the material to several application requirements by adopting different fabrication methods, in order to make films, sponges, fibers, nets or gels with predictable degradation times. For tissue engineering, in most cases porous scaffolds are required, in some cases possibly in situ forming and therefore fabricated in mild body-compatible conditions. In this work, we present a novel one-step method for the preparation of silk fibroin foams starting from water solutions and using low-pressure nitrous oxide gas as foaming agent. This foaming technique allows preparing fibroin porous scaffolds with easily tunable porosity, in mild processing conditions with the use of a relatively inert foaming agent saturating a fibroin water solution, that could be occasionally injected through a thin needle in the implantation site where expansion and foaming would occur. Optimal foaming processing conditions have been investigated, and the prepared foams have been characterized with Fourier Transform Infrared Spectroscopy (FTIR) compressive mechanical and rheological properties measurements, and by scanning electron microscopy and microCT.     

Silk fibroin and Nettle extract promote wound healing in a rat model: A histological and morphometrical study

IntroductionConsidering the anti-inflammatory, antimicrobial ability, and antioxidant effects besides stimulating ability of silk fibroin (SF) in cell migration and proliferation of Nettle, the current study aimed to investigate the effect of Nettle leaf extract (NLE) and SF on histology, morphometrical parameters and apoptosis on the wound in the rat model.Materials and methodsWistar rats are divided into 5 groups, including 1-control (rats with healthy skin and no treatment); 2-wound (without any treatment); 3-SF (administration of silk fibroin solution for 14 consecutive days); 4- Nettle (administration of Nettle ointment for 14 consecutive days), and 5- Eucerin group (administration of Eucerin substance for 14 consecutive days) and then assessed wound area by photography, angiogenesis, inflammation, and thickness of epidermis using hematoxylin and eosin (H&E) staining, collagen deposition, and structure of dermis layers evaluated by Masson's trichrome staining and the apoptosis index determined by tunnel assay on days 7, 14 and 21.Resultsphotographic illustrations showed that the wound surface environment on the seventh day in group 4 was significantly different from group 2 (p < 0.002). The rate of wound healing on the fourteenth day was higher in groups 3 and 4 than in group 2 (p < 0.001). Also, at this time, group 4 was significantly different from group 3 and group 5 (p = 0.003 and p = 0.000, respectively). There was a significant difference in epidermal thickness between the wound group and other experimental groups (p < 0.05). The number of apoptotic cells at the wound edges on the seventh day in both group 3 and group 4 had a significant decrease compared to other groups of wounds (p = 0.000), but there was a significant increase on the fourteenth day. Also, on the 21st day, a significant decrease in apoptotic cells was observed in both group 3 and group 4 compared to other wound groups (p = 0.000).Discussion and ConclusionNettle and SF maintain cell homeostasis and accelerate wound closure by reducing cell apoptosis and enhancing cell proliferation on the seventh day, but by increasing the apoptosis of fibroblast cells on the fourteenth day, they lead to remodeling and keratinocytes migration to epidermis formation. Increased apoptosis also seems to be one of the pathophysiological mechanisms to prevent the formation of keloid and hypertrophic scar tissue. SF and Nettle extract, by increasing cell proliferation and migration of different cell types to the site of injury, control the remodeling process by inducing and regulating apoptosis in the first two weeks of wound healing and accelerating the process of collagen deposition and epithelialization.     

Diblock copolymers with tunable pH transitions for gene delivery

A series of diblock copolymers containing an endosomal-releasing segment composed of diethylaminoethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The materials were designed to condense plasmid DNA (pDNA) through electrostatic interactions with a cationic poly(N,N-dimethylaminoethyl methacrylate) (DMAEMA) first block. The pDMAEMA was employed as a macro chain transfer agent (macroCTA) for the synthesis of a series in which the relative feed ratios of DEAEMA and BMA were systematically varied from 20% to 70% BMA. The resultant diblock copolymers exhibited low polydispersity (PDI ≤ 1.06) with similar molecular weights (M_n = 19.3-23.1 kDa). Dynamic light scattering (DLS) measurements in combination with ¹H NMR D₂O studies demonstrated that the free copolymers assemble into core-shell micelles at physiological pH. Reduction of the solution pH to values representative of endosomal/lysosomal compartments induced an increase in the net cationic charge of the core through protonation of the DEAEMA residues. This protonation promotes micelle destabilization and exposure of the hydrophobic BMA residues that destabilize biological membranes. The pH value at which this micelle-to-unimer transition occurred was dependent on the hydrophobic content of the copolymer, with higher BMA-containing copolymer compositions exhibiting pH-induced transitions to the membrane-destabilizing state at successively lower pH values. The ability of the diblock copolymers to deliver pDNA was subsequently investigated using a GFP expression vector in two monocyte cell lines. High levels of DNA transfection were observed for the copolymer compositions exhibiting the sharpest pH transitions and membrane destabilizing activities, demonstrating the importance of tuning the endosomal-releasing segment composition.     

Generation of bioactive nano-composite scaffold of nanobioglass/silk fibroin/carboxymethyl cellulose for bone tissue engineering

Abstract

The development of bone tissue construct through tissue engineering approach offers a great promise in meeting the increasing demand for repair and regeneration of damaged and/or diseased bone tissue. For the generation of bone tissue engineered construct, polymer-ceramic composite matrices with nanostructure architecture and mesenchymal stem cells (hMSCs) of human origin are of prime requirement. Keeping these in view, in the present work a novel electrospun nanofibrous silk fibroin (SF)/carboxymethyl cellulose (CMC)/nano-bioglass (nBG) composite scaffold that mimics native bone extracellular matrix with appropriate composition was designed and fabricated by free liquid surface electrospinning technique. The scaffold possesses desired morphological, structural, biodegradability, bioactivity, surface roughness and mechanical properties thereby exhibited an excellent platform to support the growth of cells. The in-vitro culture of hMSCs over the developed scaffold has shown adhesion, proliferation and viability of cells, thus facilitated cell-scaffold construct generation and further extracellular bone matrix formation through osteogenic differentiation as evident from alkaline phosphatase activity, biomineralization, immunostaining and Runx2/osteocalcin expression assessment. Thus, the developed hMSCs seeded scaffold construct might be suitable for bone tissue engineering applications.     

Surface polyethylene glycol enhances substrate-mediated gene delivery by nonspecifically immobilized complexes

Substrate-mediated gene delivery describes the immobilization of gene therapy vectors to a biomaterial, which enhances gene transfer by exposing adhered cells to elevated DNA concentrations within the local microenvironment. Surface chemistry has been shown to affect transfection by nonspecifically immobilized complexes using self-assembled monolayers (SAMs) of alkanethiols on gold. In this report, SAMs were again used to provide a controlled surface to investigate whether the presence of oligo(ethylene glycol) (EG) groups in a SAM could affect complex morphology and enhance transfection. EG groups were included at percentages that did not affect cell adhesion. Nonspecific complex immobilization to SAMs containing combinations of EG- and carboxylic acid-terminated alkanethiols resulted in substantially greater transfection than surfaces containing no EG groups or SAMs composed of EG groups combined with other functional groups. Enhancement in transfection levels could not be attributed to complex binding densities or release profiles. Atomic force microscopy imaging of immobilized complexes revealed that EG groups within SAMs affected complex size and appearance and could indicate the ability of these surfaces to preserve complex morphology upon binding. The ability to control the morphology of the immobilized complexes and influence transfection levels through surface chemistry could be translated to scaffolds for gene delivery in tissue engineering and diagnostic applications.     

丝素蛋白与胎盘间充质干细胞生物相容性的实验研究

目的 探讨丝素蛋白（SF）材料与胎盘间充质干细胞（PMSCs）的生物相容性.方法 运用SF溶液包被的培养瓶培养PMSCs,流式细胞术分析其表型并对其定向分化潜能进行探讨;PMSCs置于SF膜材料培养后通过扫描电镜观察细胞形态变化.结果 用SF溶液包被的培养瓶培养的PMSCs,其生长特性、表面标志、多向分化潜能无明显变化;PMSCs在SF膜材料上生长良好,培养8 d时材料上细胞伸展增殖,分泌大量颗粒状、网状基质物质,材料间隙被基质填满.结论 SF材料不影响PMSCs的生长特性、表面标志和多向分化潜能,具有良好的生物相容性.     

Bioengineered silk protein-based gene delivery systems

Silk proteins self-assemble into mechanically robust material structures that are also biodegradable and non-cytotoxic, suggesting utility for gene delivery. Since silk proteins can also be tailored in terms of chemistry, molecular weight and other design features via genetic engineering, further control of this system for gene delivery can be considered. In the present study, silk-based block copolymers were bioengineered with poly(l-lysine) domains for gene delivery. Ionic complexes of these silk-polylysine based block copolymers with plasmid DNA (pDNA) were prepared for gene delivery to human embryonic kidney (HEK) cells. The material systems were characterized by agarose gel electrophoresis, atomic force microscopy, and dynamic light scattering. The polymers self-assembled in solution and complexed plasmid DNA through ionic interactions. The pDNA complexes with 30 lysine residues prepared at a polymer/nucleotide ratio of 10 and with a solution diameter of 380 nm showed the highest efficiency for transfection. The pDNA complexes were also immobilized on silk films and demonstrated direct cell transfection from these surfaces. The results demonstrate the potential of bioengineered silk proteins as a new family of highly tailored gene delivery systems.     

Fabrication of highly interconnected porous silk fibroin scaffolds for potential use as vascular grafts

Silk fibroin (SF) scaffolds have been designed and fabricated for multiple organ engineering owing to SF’s remarkable mechanical property, excellent biocompatibility and biodegradability, as well as its low immunogenicity. In this study, an easy-to-adopt and mild approach based on a modified freeze-drying method was developed to fabricate a highly interconnected porous SF scaffold. The physical properties of the SF scaffold, including pore morphology, pore size, porosity and compressive modulus, could be adjusted by the amount of ethanol added, the freezing temperature and the concentration of SF. Fourier transform infrared spectroscopy illustrated that treatment of the lyophilized scaffolds with 90% methanol led to a structure transition of SF from silk I (random coil) to silk II (beta-sheet), which stabilized the SF scaffolds in water. We also incorporated heparin during fabrication to obtain a heparin-loaded scaffold which possessed excellent anticoagulant property. The heparin that was incorporated into the SF scaffolds could be released in a sustain manner for approximately 7 days, inhibiting the proliferation of human smooth muscle cells within the scaffold in vitro while promoting neovascularization in vivo. We therefore propose that the SF porous scaffold fabricated here may be an attractive candidate for use as a potential vascular graft for implantation based on its high porosity, excellent blood compatibility and mild fabrication process.     

Sodium oleate induced rapid gelation of silk fibroin

Silk fibroin has acquired increasing interest in the last years for application in medicine and namely in tissue engineering. Several methods have been developed to process fibroin and for the fabrication of nets, sponges, films and gels. This paper deals with the fabrication and characterization of fibroin hydrogels obtained by using sodium oleate as gelation agent. Gels have been prepared by mixing Silk fibroin (SF) and Sodium oleate (SO) water solutions in different concentrations, and a quite wide frame of compositions have been explored. Rheological tests have been performed to determine the gelation times, scanning electron microscopies have been made to evaluate morphologies, FTIR analysis has been done to determine the conformation of the starting materials and of the resulting gels, water content has been measured and cytotoxicity tests have been performed to validate the potential biomedical use of the hydrogels. Depending on the SF and SO different gelation times have been obtained thanks to the formation of intermolecular bonds between the fibroin chains. The obtained fastest gelation of about 80 s could make this specific formulation compatible with in situ gelation. By changing composition, gels with different morphologies, rheological properties and water contents have been prepared.     

Silk fibroin rods for sustained delivery of breast cancer therapeutics

A silk-protein based reservoir rod was developed for zero-order and long-term sustained drug delivery applications. Silk reservoir rod formulations were processed in three steps. First, a regenerated silk fibroin solution, rich in random-coil content was transformed into a tubular silk film with controllable dimensions, uniform film morphology and a structure rich in silk II, β-sheet content via “film-spinning.” Second, the drug powder was loaded into swollen silk tubes followed by tube end clamping. Last, clamped silk tube ends were sealed completely via dip coating. Anastrozole, an FDA approved active ingredient for the treatment of breast cancer, was used as a model drug to investigate viability of the silk reservoir rod technology for sustained drug delivery. The in vitro and in vivo pharmacokinetic data (in a female Sprague–Dawley rat model) analyzed via liquid chromatography-tandem mass spectroscopy indicated zero-order release for 91 days. Both in vitro and in vivo anastrozole release rates could be controlled simply by varying silk rod dimensions. The swelling behavior of silk films and zero-order anastrozole release kinetics indicated practically immediate film hydration and formation of a linear anastrozole concentration gradient along the silk film thickness. The dependence of anastrozole release rate on the overall silk rod dimensions was in good agreement with an essentially diffusion-controlled sustained release from a reservoir cylindrical geometry. In vivo results highlighted a strong in vitro-in vivo pharmacokinetic correlation and a desirable biocompatibility profile of silk reservoir rods. During a 6-month implantation in rats, the apparent silk molecular weight values decreased gradually, while rod dry mass and β-sheet crystal content values remained essentially constant, providing a suitable timeframe for controlled, long-term sustained delivery applications. Overall, the silk reservoir rod may be a viable candidate for sustained delivery of breast cancer therapeutics.     

Macro/microporous silk fibroin scaffolds with potential for articular cartilage and meniscus tissue engineering applications

This study describes the developmental physicochemical properties of silk fibroin scaffolds derived from high-concentration aqueous silk fibroin solutions. The silk fibroin scaffolds were prepared with different initial concentrations (8, 10, 12 and 16%, in wt.%) and obtained by combining the salt-leaching and freeze-drying methodologies. The results indicated that the antiparallel β-pleated sheet (silk-II) conformation was present in the silk fibroin scaffolds. All the scaffolds possessed a macro/microporous structure. Homogeneous porosity distribution was achieved in all the groups of samples. As the silk fibroin concentration increased from 8 to 16%, the mean porosity decreased from 90.8 ± 0.9 to 79.8 ± 0.3% and the mean interconnectivity decreased from 97.4 ± 0.5 to 92.3 ± 1.3%. The mechanical properties of the scaffolds exhibited concentration dependence. The dry state compressive modulus increased from 0.81 ± 0.29 to 15.14 ± 1.70 MPa and the wet state dynamic storage modulus increased by around 20- to 30-fold at each testing frequency when the silk fibroin concentration increased from 8 to 16%. The water uptake ratio decreased with increasing silk fibroin concentration. The scaffolds present favorable stability as their structure integrity, morphology and mechanical properties were maintained after in vitro degradation for 30 days. Based on these results, the scaffolds developed in this study are proposed to be suitable for use in meniscus and cartilage tissue-engineered scaffolding.     

Multi-layered nanoparticles for combination gene and drug delivery to tumors

Drug resistance and toxicity are major obstacles in cancer chemotherapy. Combination therapies can overcome resistance, and synergies can minimize dosing. Polymer nanocarriers are interesting vehicles for cancer therapeutics for their delivery and tumor targeting abilities. We synthesized a multi-layered polymer nanoparticle (MLNP), comprising of poly(lactic-co-glycolic acid) with surface polyethyleneimine and functional peptides, for targeted drug and gene delivery. We confirmed the particle's ability to inhibit tumor growth through synergistic action of the drug and gene product. MLNPs achieved transfection levels similar to lipofectamine, while maintaining minimal cytotoxicity. The particles delivered camptothecin (CPT), and plasmid encoding TNF related apoptosis inducing ligand (pTRAIL) (CT MLNPs), and synergistically inhibited growth of multiple cancer cells in vitro. The synergy of co-delivering CPT and pTRAIL via CT MLNPs was confirmed using the Chou-Talalay method: the combination index (CI) values at 50% inhibition ranged between 0.31 and 0.53 for all cell lines. Further, co-delivery with MLNPs resulted in a 3.1–15 fold reduction in CPT and 4.7–8.0 fold reduction in pTRAIL dosing. CT MLNPs obtained significant HCT116 growth inhibition in vivo compared to monotherapy. These results support our hypothesis that MLNPs can deliver both small molecules and genetic agents towards synergistically inhibiting tumor growth.     

In vitro evaluation of electrospun silk fibroin/nano-hydroxyapatite/BMP-2 scaffolds for bone regeneration

Bone tissue engineering by using osteoinductive scaffolds seeded with stem cells to promote bone extracellular matrix (ECM) production and remodeling has evolved into a promising approach for bone repair and regeneration. In order to mimic the ECM of bone tissue structurally and compositionally, nanofibrous silk fibroin (SF) scaffolds containing hydroxyapatite (HAP) nanoparticles and bone morphogenetic protein 2 (BMP-2) were fabricated in this study using electrospinning technique. The microstructure, mechanical property, biocompatibility, and osteogenic characteristics were examined. It was found that the HAP nanoparticles were successfully incorporated in the SF nanofibers (diameter, 200–500 nm). The mechanical properties of SF/HAP/BMP-2 composite scaffolds increased with HAP content when it was less than 20 wt%, after which the mechanical properties dropped as HAP content increased. Cell culture tests using bone marrow mesenchymal stem cells (BMSCs) showed that the scaffolds had good biocompatibility and promoted the osteogenic differentiation of BMSCs. Therefore, the electrospun SF/HAP/BMP-2 scaffolds may serve as a promising biomaterial for bone tissue engineering.