Orthogonally oriented scaffolds with aligned fibers for engineering intestinal smooth muscle

Controlling cellular alignment is critical in engineering intestines with desired structure and function. Although previous studies have examined the directional alignment of cells on the surface (x–y plane) of parallel fibers, quantitative analysis of the cellular alignment inside implanted scaffolds with oriented fibers has not been reported. This study examined the cellular alignment in the x–z and y–z planes of scaffolds made with two layers of orthogonally oriented fibers. The cellular orientation inside implanted scaffolds was evaluated with immunofluorescence. Quantitative analysis of coherency between cell orientation and fiber direction confirmed that cells aligned along the fibers not only on the surface (x–y plane) but also inside the scaffolds (x–z & y–z planes). Our study demonstrated that two layers of orthogonally aligned scaffolds can generate the histological organization of cells similar to that of intestinal circular and longitudinal smooth muscle.     

静电纺丝技术在生物医用材料领域中的应用

电纺丝是一种使带电荷的聚合物溶液或熔体在静电场中射流来制备聚合物超细纤维的加工方法。由于电纺丝技术制得的纤维，其直径可达纳米级，因此电纺丝纤维应用广泛。对静电纺丝技术的一些重要特性和当前在生物医用材料领域中的应用进行综述。     

Cellular Migration to Electrospun Poly(Lactic Acid) Fibermats

Abstract

Nonwoven fabrics prepared via an electrospinning method, so-called electrospun fibermats, are expected to be promising scaffold materials for bone tissue engineering. In the present work, poly(L-lactic acid) (PLLA) fibermats, consisting of fibers with diameters ranging from 1 to 10 μm, were prepared by electrospinning. Mouse osteoblast-like cells (MC3T3-E1) were seeded on the fibermats with various fiber diameters (10, 5 and 2 μm; they are denoted by samples A, B and C, respectively) and cultured in two different directions in order to compare the migration behaviours into the scaffold of the normal condition and the anti-gravity condition. The cells in/on the fibermats were observed by laser confocal microscopy to estimate the cellular migration ability into them. When the MC3T3-E1 cells were cultured in the normal direction, the thickness of their layer increased to approx. 90 μm in the sample A, consisting of 10-μm fibers after 13 days of culture, while that in the sample C, consisting of 2-μm fibers, did not increase. When the MC3T3-E1 cells were cultured in the anti-gravity condition, the thickness of the cell layer in the sample A increased to approx. 60 μm. These results mean that the MC3T3-E1 cells migrated into the inside of sample A in either the normal direction or the anti-gravity one. The cellular proliferation showed no significant difference among the fibermats with three different fiber diameters; MC3T3-E1 cells on the fibermat with 2 μm fiber diameter grew two-dimensionally, while they grew three-dimensionally in the fibermat with 10 μm fiber diameter.     

Electrospun Biomimic Nanofibrous Scaffolds of Silk Fibroin/Hyaluronic Acid for Tissue Engineering

Abstract

This study aimed to fabricate nanofibrous scaffolds which could biomimic the natural extracellular matrix from aqueous solutions of silk fibroin and hyaluronic acid blends (SF/HA) by means of electrospinning. Scanning electronic microscopy results indicated that electrospun SF/HA nanofibers were ribbon-shaped and their average width obviously decreased with the increase of HA content. However, there is no fiber observed when the volume of HA further increased to 50% of overall volume. After being treated with 75% ethanol vapor for 24 h, the fibers still remained their fibrous morphologies and presented good capability of water-resistance. Fourier transform infrared attenuated total reflectance spectroscopy, ¹³C-CP-MAS nuclear magnetic resonance and differential scanning calorimetry results revealed that HA did not induce SF conformation from random coil to β-sheet. SF conformation converted from random coil to β-sheet after being treated with 75% ethanol vapor. Cell viability studies demonstrated that SF/HA nanofibrous scaffolds significantly promoted cell proliferation. Electrospun SF/HA nanofibers may provide an ideal biomimic tissue-engineering scaffold or vehicle for water-soluble drugs.     

Shell-core bi-layered scaffolds for engineering of vascularized osteon-like structures

Bottom-up assembly of osteon-like structures into large tissue constructs represents a promising and practical strategy toward the formation of hierarchical cortical bone. Here, a unique two-step approach, i.e., the combination of electrospinning and twin screw extrusion (TSE) techniques was used to fabricate a microfilament/nanofiber shell–core scaffold that could precisely control the spatial distribution of different types of cells to form vascularized osteon-like structures. The scaffold contained a helical outer shell consisting of porous microfilament coils of polycaprolactone (PCL) and biphasic calcium phosphates (BCP) that wound around a hollow electrospun PCL nanofibrous tube (the core). The porous helical shell supported the formation of bone-like tissues, while the luminal surface of nanofibrous core enabled endothelialization to mimic the function of Haversian canal. Culture of mouse pre-osteoblasts (POBs, MC 3T3-E1) onto the coil shells revealed that coils with pitch sizes greater than 135 μm, in the presence of BCP, favored the proliferation and osteogenic differentiation of POBs. The luminal surface of PCL nanofibrous core supported the adhesion and spreading of mouse endothelial cells (ECs, MS-1) to form a continuous endothelial lining with the function similar to blood vessels. Taken together, the shell–core bi-layered scaffolds with porous, coil-like shell and nanofibrous tubular cores represent a new scaffolding technology base for the creation of osteon analogs.     

The improved antibacterial efficiency of a zinc phthalocyanine when embedded on silver nanoparticle modified silica nanofibers

This work reports on the fabrication and modification of electrospun polymer free silica nanofibers (SiO₂ NFs) with the aim of creating heterogeneous antibacterial catalysts. The optical and photophysical properties of the obtained NFs i.e. bare SiO₂, Ag-SiO₂, Pc-SiO₂ and Pc@Ag-SiO₂ NFs (Pc = phthalocyanine) were compared and reported. The singlet oxygen quantum yields of the Pc-SiO₂ and Pc@Ag-SiO₂ NFs were also quantified and found to be 0.08 and 0.12, respectively, in water. All the modified SiO₂ NFs were found to possess photoactivity against S. aureus with the most effective being the Pc@Ag-SiO₂ NFs due to the synergy between the Pc and Ag nanoparticles. The bare SiO₂ NFs do not exhibit any antibacterial activity while the Ag-SiO₂ and Pc@Ag-SiO₂ NFs were found to also exhibit dark toxicity. The generated photocatalysts are attractive because they are active against bacteria and they are easily retrievable post-application. The nanocatalysts reported herein are therefore feasible candidates for real-life antibacterial applications.     

Fabrication of hybrid scaffold based on hydroxyapatite-biodegradable nanofibers incorporated with liposomal formulation of BMP-2 peptide for bone tissue engineering

In the present study, we fabricated an efficient, simple biomimetic scaffold to stimulate osteogenic differentiation of mesenchymal stem cells (MSCs). Electrospun poly L-lactic acid nanofibers were employed to mimic the nanofibrillar structure of bone proteins and coated with hydroxyapatite nanoparticles to simulate bone minerals. Thereafter, we regulated the release pattern of BMP-2 peptide through covalent attachment of an optimized liposomal formulation to the scaffold. The fabricated platform provided a sustained release profile of BMP-2 peptide up to 21?days while supporting cellular attachment and proliferation without cytotoxicity. In-vitro results confirmed the superiority of the scaffold containing liposomes through enhancement of growth and differentiation of MSCs. Ectopic bone formation model exhibited significant localized initiation of bone formation of liposome incorporated scaffold. Consequently, these findings demonstrated that our designed platform with modified release properties of BMP-2 peptide considerably promoted osteogenic differentiation of MSCs making it a unique candidate for bone regeneration therapeutics.     

In vivo wound healing performance of drug loaded electrospun composite nanofibers transdermal patch

Acute injuries or wound is required the fast delivery of drug to control infections without any side effect. In this direction in the present investigation, antibiotic ciprofloxacin loaded hydrophilic biodegradable poly vinyl alcohol (PVA) and sodium alginate (NaAlg) electrospun composite nanofiber based transdermal patch was developed for local delivery of antibiotic drug. The antibiotic drug ciprofloxacin was loaded in it by active loading. The drug entrapped in the composite nanofibers was confirmed by the scanning electron microscopy and swelling behavior. The in vivo studies were carried on male rabbits by using the drug loaded and unloaded composite nanofibers transdermal patch and marketed one. It is observed that, in vitro activity provides a sustained and controlled release pattern of the drug from transdermal patch. The mechanism of drug release was also studied using different models. The nanofiber transdermal patch follows the Higuchi and Korsmeyer–Peppas model for drug release. The in vivo studies demonstrate that, wound healing takes place in less time as compared drug unloaded patch. Hydroxyproline produced in wound bed with time shows that it content is maximum in case drug loaded PAV-NaAlg patch. This demonstrates that wound healing rate is higher in case drug loaded PVA-NaAlg transdermal patch.     

The effect of thick fibers and large pores of electrospun poly(ε-caprolactone) vascular grafts on macrophage polarization and arterial regeneration

The vascular grafts prepared by electrospinning often have relatively small pores, which limit cell infiltration into the grafts and hinder the regeneration and remodeling of the grafts into neoarteries. To overcome this problem, macroporous electrospun polycaprolactone (PCL) scaffolds with thicker fibers (5–6 μm) and larger pores (∼30 μm) were fabricated in the present study. In vitro cell culture indicated that macrophages cultured on thicker-fiber scaffolds tended to polarize into the immunomodulatory and tissue remodeling (M2) phenotype, while those cultured on thinner-fiber scaffolds expressed proinflammatory (M1) phenotype. In vivo implantation by replacing rat abdominal aorta was performed and followed up for 7, 14, 28 and 100 d. The results demonstrated that the macroporous grafts markedly enhanced cell infiltration and extracellular matrix (ECM) secretion. All grafts showed satisfactory patency for up to 100 days. At day 100, the endothelium coverage was complete, and the regenerated smooth muscle layer was correctly organized with abundant ECM similar to those in the native arteries. More importantly, the regenerated arteries demonstrated contractile response to adrenaline and acetylcholine-induced relaxation. Analysis of the cellularization process revealed that the thicker-fiber scaffolds induced a large number of M2 macrophages to infiltrate into the graft wall. These macrophages further promoted cellular infiltration and vascularization. In conclusion, the present study confirmed that the scaffold structure can regulate macrophage phenotype. Our thicker-fiber electrospun PCL vascular grafts could enhance the vascular regeneration and remodeling process by mediating macrophage polarization into M2 phenotype, suggesting that our constructs may be a promising cell-free vascular graft candidate and are worthy for further in vivo evaluation.